JP2009065216A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized photoelectric conversion element which can be manufactured inexpensively and has excellent photoelectric conversion efficiency. <P>SOLUTION: A solar battery 1A shown in Fig. 1 is a so-called dry solar battery which does not require an electrolytic solution, and provided with a first electrode 3, a second electrode 6 placed opposite to the first electrode 3, an electron transport layer 4 positioned therebetween, a dye layer D being in contact with the electron transport layer 4, and a hole transport layer 5 which is positioned between the electron transport layer 4 and the second electrode 6 and in contact with the dye layer D, all of which are placed on a substrate 2. The electron transport layer contains a material for suppressing the reverse electron transfer of electrons excited from dye. The material for suppressing the reverse electron transfer of the electrons is a material which has the bottom potential of a conduction band on a valence band side from the bottom potential of the conduction band of the electron transport layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element.

Conventionally, solar cells (photoelectric conversion elements) using silicon have attracted attention as environmentally friendly power sources. 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,
In addition, a large amount of energy is required for production, and it cannot always be said to be an energy-saving power source.

In addition, a dye-sensitized wet solar cell (see, for example, Patent Document 1), which has been developed as a next-generation solar cell that replaces this and has a low production cost and low production energy, is an electrolysis with a high vapor pressure. Since the solution was used, there was a problem that the electrolyte solution volatilized.

In addition, as a supplement to such drawbacks, a completely solid dye-sensitized solar cell (for example, see Non-Patent Document 1) has been announced.

This solar cell is configured to have an electrode in which a TiO ₂ layer is laminated and a p-type semiconductor layer provided on the TiO ₂ layer.

However, any of these types of dye-sensitized solar cells has not yet been put into practical use because of low conversion efficiency.

Further, as a conventional technique, a nanotube-like crystal titania (titania nanotube) that is a material suitable for a photocatalyst or the like has been developed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 1-220380 JP 10-152323 A K. Tennakone, G.R.R.A.Kumara, I.R.M.Kottegoda, K.G.U.Wijiayantha, and V.P.S.Perera: J. Phys. D: Appl. Phys. 31 (1998) 1492

An object of the present invention is to provide a solid-state dye-sensitized photoelectric conversion element that can be manufactured at low cost and has excellent photoelectric conversion efficiency.

Such an object is achieved by the present inventions (1) to (17) below.
(1) Located between the first electrode, the second electrode disposed opposite to the first electrode, the first electrode and the second electrode, at least a part of which is located A photoelectric conversion element comprising a porous electron transport layer, a dye layer in contact with the electron transport layer, and a hole transport layer positioned between the electron transport layer and the second electrode, A photoelectric conversion element characterized in that an electron transport layer contains a substance that suppresses reverse electron transfer of electrons excited from a dye.
(2) The substance that suppresses reverse electron transfer of the electron is a conduction band of the electron transport layer.
Band) A photoelectric conversion element which is a substance having a conduction band lower end potential lower than the lower end potential.
(3) The substance that suppresses reverse electron transfer of the electron is a conduction band of the electron transport layer.
Band) A photoelectric conversion element that is a substance having a conduction band lower end potential on the valence band side of the lower end potential.
(4) The photoelectric conversion element in which the surface which suppresses the reverse electron transfer of the electron excited from the pigment | dye is overcoated on the surface of the said electron carrying layer.
(5) The photoelectric conversion element in which the surface of the electron transport layer is overcoated with a substance having a conduction band lower end potential lower than the conduction band lower end potential of the electron transport layer.
(6) The photoelectric conversion element whose substance which suppresses the reverse electron transfer of the said electron is an oxide.
(7) The photoelectric conversion element whose substance which suppresses the reverse electron transfer of the said electron is a metal oxide.
(8) The photoelectric conversion element whose substance which suppresses the reverse electron transfer of the said electron is a compound.
(9) A photoelectric conversion element in which a conduction band lower end potential of the electron transport layer is 4.5 eV.
(10) The photoelectric conversion element which is a substance which has the lower end potential of the conduction band of the substance which suppresses the reverse electron transfer of the electrons on the valence band side from 4.5 eV.
(11) The photoelectric conversion element whose overcoat layer of the substance which suppresses the reverse electron transfer of the said electron of the said electron transport material surface is 0.1-10 nanometer.
(12) The photoelectric conversion element in which the electron transport material contains at least crystal particles or tube crystals.
(13) The photoelectric conversion element, wherein the electron transport material is at least TiO ₂ nanoparticles or titania nanotubes.
(14) The substance that suppresses reverse electron transfer of the electron is a valence band (Valenc) of the electron transport layer.
e Band) A photoelectric conversion element which is a substance having a valence band lower end potential higher than the lower end potential.
(15) The substance that suppresses reverse electron transfer of the electrons is a valence band (Valenc) of the electron transport layer.
e Band) A photoelectric conversion element that is a substance having a valence band lower end potential closer to the conduction band than the lower end potential.
(16) A valence band (Va) higher than the lower end potential of the valence band (Valence Band) of the electron transport layer.
lence Band) A photoelectric conversion element in which a substance having a lower end potential is overcoated on the surface of the electron transport layer.
(17) A photoelectric conversion element which is a solar cell.

Hereinafter, preferred embodiments of the photoelectric conversion element of the present invention shown in the accompanying drawings will be described in detail.

<First Embodiment>
FIG. 1 is a partial cross-sectional view showing a first embodiment when the photoelectric conversion element of the present invention is applied to a solar cell, and FIG. 2 is a cross section near the central portion in the thickness direction of the solar cell of the first embodiment. FIG. 3 is a partially enlarged view showing a cross section of the electron transport layer on which the dye layer is formed, FIG. 4 is a schematic view showing the configuration of the electron transport layer and the dye layer, and FIG. 5 is the principle of the solar cell. FIG. 6 is a diagram showing an equivalent circuit of the solar cell circuit shown in FIG.

The solar cell 1 shown in FIG. 1 is a so-called completely solid dye-sensitized solar cell that does not require an electrolyte solution, and is placed opposite to the first electrode 3 and the first electrode 3. Second
The electrode 6, the electron transport layer 4 positioned therebetween, the dye layer D in contact with the electron transport layer 4, the electron transport layer 4 and the second electrode 6, and the dye layer D A hole transport layer 5 and a barrier layer 8 are in contact with each other, and these are disposed on the substrate 2.

Hereinafter, each component will be described. In the following description, in FIGS. 1 and 2, the upper surface of each layer (each member) is referred to as “upper surface” and the lower surface is referred to as “lower surface”.

The substrate 2 is for supporting the first electrode 3, the barrier layer 8, the electron transport layer 4, the dye layer D, the hole transport layer 5, and the second electrode 6, and is composed of a plate-shaped member. ing.

In the solar cell 1A of the present embodiment, as shown in FIG. 1, light such as sunlight (hereinafter simply referred to as “light”) is incident from the substrate 2 and the first electrode 3 side described later, for example. (Irradiated) for use. 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 material of the substrate 2 include various glass materials, various ceramic materials, various resin materials such as polycarbonate (PC) and polyethylene terephthalate (PET), and various metal materials such as aluminum.

The average thickness of the substrate 2 is appropriately set depending on the material, use, etc., and is not particularly limited.
For example, it can be as follows.

When the substrate 2 is made of a hard material such as a glass material, the average thickness is preferably about 0.1 to 1.5 mm, and preferably about 0.8 to 1.2 mm. More preferred.

When the substrate 2 is made of a flexible material (flexible material) such as polyethylene terephthalate (PET), the average thickness is preferably about 0.5 to 150 μm, preferably 10 to 75 μm. More preferred is the degree.

  In addition, the board | substrate 2 can also be abbreviate | omitted as needed.

On the upper surface of the substrate 2, a layered (flat plate) first electrode 3 is provided. In other words, the first electrode 3 is disposed on the light receiving surface side of the electron transport layer 4 on which a dye layer D described later is formed so as to cover the light receiving surface. The first electrode 3 receives electrons generated in the dye layer D, which will be described later, via the electron transport layer 4 and the barrier layer 8, and is connected to the external circuit 100.
To communicate.

As a constituent material of the first electrode 3, for example, indium tin oxide (ITO),
Fluorine-doped tin oxide (FTO), indium oxide (IO), metal oxides such as tin oxide (SnO ₂ ), aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum,
Examples thereof include metals such as titanium and tantalum, alloys containing these, and various carbon materials such as graphite. One or more of these can be used in combination.

The average thickness of the first electrode 3 is appropriately set depending on the material, application, and the like, and is not particularly limited. For example, the average thickness can be as follows.

When the first electrode 3 is composed of the metal oxide (transparent conductive metal oxide), the average thickness is preferably about 0.05 to 5 μm, preferably 0.1 to 1.5 μm. More preferred is the degree.

Further, when the first electrode 3 is made of the above-described metal, an alloy containing these, or various carbon materials, the average thickness is preferably about 0.01 to 1 μm.
More preferably, it is about 03 to 0.1 μm.

In addition, the 1st electrode 3 is not limited to the thing of the structure of illustration, For example, the thing etc. which have the shape which has several comb teeth may be sufficient. In this case, the light passes between the plurality of comb teeth,
Since it reaches the dye layer D, the first electrode 3 may not be substantially transparent. This
The range of selection of the constituent material, the forming method (manufacturing method), and the like of the first electrode 3 can be expanded.
In this case, the average thickness of the first electrode 3 is not particularly limited.
The thickness is preferably about 5 μm.

Further, as the first electrode 3, such a comb-like electrode and a transparent electrode made of ITO, FTO, or the like can be used in combination (for example, laminated).

On the upper surface of the first electrode 3, a film-like (layer-like) barrier layer (short-circuit preventing means) 8 is provided. The details of the barrier layer 8 will be described later.

On the upper surface of the barrier layer 8, a porous electron transport layer 4 and a dye layer D in contact with the electron transport layer 4 are provided.

The electron transport layer 4 has a function of transporting at least electrons generated in the dye layer D.

Examples of the constituent material of the electron transport layer 4 include titanium oxide such as titanium dioxide (TiO ₂ ), titanium monoxide (TiO), and dititanium trioxide (Ti ₂ O ₃ ), zinc oxide (ZnO), and tin oxide ( Examples include n-type oxide semiconductor materials such as SnO ₂ ), other n-type semiconductor materials, and the like, and one or more of these can be used in combination. Among these, titanium oxide, In particular, it is preferable to use titanium dioxide. That is, the electron transport layer 4 is
It is preferably composed mainly of titanium dioxide.

Titanium dioxide is particularly excellent in electron transport capability and high sensitivity to light.
The electron transport layer 4 itself can also generate electrons. As a result, in the solar cell 1A, the photoelectric conversion efficiency (power generation efficiency) can be further improved.

In addition, since the crystal structure of titanium dioxide is stable, the electron transport layer 4 mainly composed of titanium dioxide has little secular change (deterioration) even when exposed to a harsh environment, and stable performance. Has the advantage that it can be obtained continuously over a long period of time.

Further, for the electron transport layer 4 made of titanium dioxide, nanotube-shaped crystalline titania (titania nanotube) may be used as a single substance or as a mixture.

Conventionally, this nanotube-like crystalline titania (titania nanotube) has been disclosed in
As reported in Japanese Patent No. 152323, it is used as a material suitable for applications such as ultraviolet absorbers, adhesives, and catalysts.

In our experiment, when this titania nanotube is used alone or as a mixture in the electron transport layer of the present invention, the propagation speed of the electrons excited by the dye and injected into the electron transport layer becomes very fast. It has been clarified that there is an action of suppressing recombination of holes.

This is because conventional TiO ₂ nanoparticles are composed of several to several tens of TiO ₂ molecules (particles, gr
ain), whereas titania nanotubes are composed of single or several molecules of Ti.
This is because the O ₂ molecules are combined in a tube shape to form a titania nanotube, and the electron propagation speed is fast and the reverse electron transfer of the electrons excited by the dye is suppressed. This is because bonding is difficult to occur.

When a nanotube-like crystal titania (hereinafter referred to as titania nanotube) is used alone or as a mixture for the electron transport layer 4 made of titanium dioxide, the specific surface area of the titania nanotube is 5 to 100 times larger than that of the commonly used titanium dioxide particles. The surface area of the electron transport layer 4 can be made sufficiently large.

More specifically, titanium dioxide particles generally used as compared to a specific surface area of about 10 to 150 m ² / g, titania nanotubes have a specific surface area of about 100~1500m ² / g.

Therefore, the formation area (formation region) of the dye layer D (see below) formed along the outer surface of the electron transport layer 4 and the inner surface of the hole 41 can be sufficiently increased, and the conventional porous T
The amount of dye adsorbed was 5 to 100 times that of the iO ₂ crystal.

The specific surface area of the titania nanotube is greater reason than the specific surface area of a conventional TiO ₂ nanoparticles, conventional TiO ₂ nanoparticles, several to several tens of TiO ₂ molecules mass of (particles, gr
ain), whereas titania nanotubes are composed of single or several molecules of Ti.
This is because O ₂ molecules are bonded in a tube shape to form a titania nanotube.

Next, a method for forming the titania nanotube will be described in detail below.
(1) First, a metal alkoxide such as titanium isopropoxide (Ti (OPr) ₄ ) and I
A sol-gel method in which TiO ₂ (titanium dioxide) is formed by hydrolysis by adding water to a solution in which an acid such as nitric acid or acetic acid is added to a solution in which an alcohol such as PA (isopropyl alcohol) is mixed. a strong acid etc., vapor phase method for forming the TiO ₂ hydrous titanium oxide obtained by heating overheated water decomposition by firing at 800 to 900 ° C., the TiO ₂ in contact with O ₂ and H ₂ in the TiCl ₄ TiO ₂ is formed by a well-known formation method such as a liquid phase method to be formed.
(2) Next, TiO ₂ (crystals) obtained by these methods is converted to 5-15 M (mol) K.
Put in an aqueous solution of OH (potassium hydroxide) or NaOH (sodium hydroxide), 60-
An alkali treatment is performed at 150 ° C. for 10 to 20 hours.
(3) The TiO ₂ alkali aqueous solution is neutralized with a dilute hydrochloric acid (HCl) aqueous solution and pure water so as to have a pH of around 7.
(4) In this state, since it is a lump of TiO ₂ , it is mixed in a mortar or the like for about 1 to 10 hours to obtain titania nanotubes.

When the powder thus obtained was observed with an SEM (scanning electron microscope), titania nanotubes having a diameter of 5 to 50 nm, a length of 10 to 200 nm, and a specific surface area of 100 to 1500 m ² / g were formed depending on the production conditions. .

The thus formed nanotube-like (body) crystalline titania (titania nanotubes) made of titanium dioxide is used for the electron transport layer 4 as a single body or a mixture.

As another method for suppressing reverse electron transfer of electrons excited by a dye, the above-described TiO
_A substance (thin metal oxide) that suppresses reverse electron transfer of 0.1 to 10 nanometer electrons may be overcoated on the surface of the _two nanoparticles or titania nanotube.

At this time, the substance that suppresses reverse electron transfer of electrons is a conduction band of the electron transport layer.
The material must have a conduction band lower potential than the lower band potential, and the conduction band lower than the conduction band lower potential of the electron transport layer.
An overcoat layer having a thickness of 0.1 to 10 nanometers is formed on the surface of the electron transport layer.

A substance that suppresses reverse electron transfer of an electron has a conduction band lower end potential lower than the conduction band lower end potential of the electron transport layer. That is, the substance that suppresses the conduction band is a substance having a conduction band lower end potential on the valence band side of the conduction band lower end potential of the electron transport layer.

In our experiment, as a substance that suppresses reverse electron transfer of electrons, the conduction band of the electron transport layer (
When a substance having a conduction band lower end potential lower than the lower end potential is overcoated on the surface of titania nanoparticles or titania nanotubes with a thickness of 0.1 to 10 nanometers, it is excited by the dye. The electrons are first injected into the overcoat layer made of metal oxide and then propagated to TiO ₂ . After that, both conduction bands (Con
duction Band) Due to the difference in the height of the lower end potential, the reverse transfer of electrons from TiO ₂ to the metal oxide is less likely to occur. ing.

At this time, when TiO ₂ is used for the electron transport layer, the conduction band of TiO ₂ (Conduction Ban
d) The lower end potential is 4.5 eV, and the conduction band of a substance that suppresses reverse electron transfer of electrons (Conductio)
n Band) The lower end potential is 4.5 eV or less.

The lower end potential of the conduction band of the substance that suppresses reverse electron transfer of electrons is 4.5 eV.
This means that the conduction band of a substance that suppresses reverse electron transfer of electrons (Conduction Band)
) It indicates that the lower end potential is a substance having a lower end potential on the valence band side from 4.5 eV.

The electron transport material contains at least crystal particles or tube-like crystals, and is preferably at least TiO ₂ nanoparticles or titania nanotubes.

In addition, the substance that suppresses reverse electron transfer of the electron is a valence band (Valence) of the electron transport layer.
Preferably, the substance has a valence band lower end potential higher than the lower end potential. That is, the substance that suppresses reverse electron transfer of the electron is a valence band (Valence B) that is closer to the conduction band than the lower end potential of the valence band (Valence Band) of the electron transport layer.
and) having a lower end potential.

As a specific example of the substance that suppresses reverse electron transfer of electrons, a metal oxide is preferable. Specific examples of the metal oxide include zirconium oxide, strontium titanate, niobium oxide, M
gO, ZnO, SnO _{2 and the} like are used, and these are conduction bands lower than the lower end potential of the conduction band (conduction band) of TiO ₂ (titanium dioxide) constituting the electron transport layer 4.
) A metal oxide having a lower end potential.

This material is overcoated with a thickness of 0.1 to 10 nanometers on the surface of the electron transport layer.

Next, the formation method of this overcoat layer is demonstrated in detail below.
(1) An electron transport material layer containing at least titania nanoparticles or titania nanotubes is formed on a glass substrate.
(2) Next, the glass substrate on which the electron transport material layer is formed is immersed in a magnesium solution.
(3) After that, the substrate taken out from the solution is washed, and the substrate is 40 in the air or in an oxygen atmosphere.
By re-baking the substrate at a temperature of 0 to 500 degrees, a thin film metal oxide layer of 0.1 to 10 nanometers of magnesium oxide is formed on the surface of titania nanoparticles or titania nanotubes which are electron transport material layers.

Such a thin-film group oxide layer is overcoated with a thickness of 0.1 to 10 nanometers on the surface of the electron transport layer.

Next, as titanium dioxide, the one whose crystal structure is mainly anatase type titanium dioxide,
Any of those mainly composed of rutile type titanium dioxide and those mainly composed of a mixture of anatase type titanium dioxide and rutile type titanium dioxide may be used.

Titanium dioxide having an anatase type crystal structure has an advantage that electrons can be transported more efficiently.

When mixing rutile type titanium dioxide and anatase type titanium dioxide, the mixing ratio of rutile type titanium dioxide and anatase type titanium dioxide is not particularly limited,
For example, the weight ratio is preferably about 95: 5 to 5:95, and 80:20 to 20:80.
More preferred is the degree.

The electron transport layer 4 has a plurality of holes (pores) 41. FIG. 3 schematically shows a state where light is incident on the electron transport layer 4. As shown in FIG. 3, the light that has passed through the barrier layer 8 (
3) penetrates to the inside of the electron transport layer 4 and transmits through the electron transport layer 4 or reflects (diffuse reflection, diffusion, etc.) in an arbitrary direction within the hole 41.
At this time, light comes into contact with the dye layer D, and electrons and holes can be generated at a high frequency in the dye layer D.

The porosity of the electron transport layer 4 is not particularly limited. For example, it is preferably about 5 to 90%, more preferably about 15 to 50%, and about 20 to 40%. Is more preferable.

By setting the porosity of the electron transport layer 4 within such a range, the surface area of the electron transport layer 4 can be sufficiently increased. Therefore, the formation area (formation region) of the dye layer D (see later) formed along the outer surface of the electron transport layer 4 and the inner surface of the hole 41 can be sufficiently increased. For this reason, in the dye layer D, sufficient electrons can be generated, and these electrons can be efficiently transferred to the electron transport layer 4. As a result, in the solar cell 1A,
The power generation efficiency (photoelectric conversion efficiency) can be further improved.

In addition, the electron transport layer 4 may have a relatively large thickness, but preferably has a film shape. Thereby, the solar cell 1A can be thinned (downsized) and the manufacturing cost can be reduced, which is advantageous.

In this case, the average thickness (film thickness) of the electron transport layer 4 is not particularly limited.
The thickness is preferably about 0.1 to 300 μm, more preferably about 0.5 to 100 μm, and further preferably about 1 to 25 μm.

Such an electron transport layer 4 is formed so that the dye layer D comes into contact with the dye by, for example, adsorption, bonding (covalent bond, coordinate bond), or the like.

The dye layer D is a light-receiving layer that generates electrons and holes by receiving light, and is formed along the outer surface of the electron transport layer 4 and the inner surface of the hole 41 as shown in FIG.
Thereby, the electrons generated in the dye layer D can be efficiently transferred to the electron transport layer 4.

The dye constituting the dye layer D is not particularly limited, and examples thereof include pigments, dyes, and the like. These can be used alone or as a mixture, but are less deteriorated and deteriorated over time. It is preferable to use a dye from the viewpoint that the pigment is more adsorbable to the electron transport layer 4 (bondability with the electron transport layer 4).

The pigment is not particularly limited, but examples thereof include phthalocyanine pigments such as phthalocyanine green and phthalocyanine blue, fast yellow, disazo yellow, condensed azo yellow, benzoimidazolone yellow, dinitroaniline orange, benzimidazolone orange, and toluidine. Red, permanent carmine, permanent red, naphthol red, condensed azo red, azo pigments such as benzimidazolone carmine and benzimidazolone brown, anthraquinone pigments such as anthrapyrimidine yellow and anthraquinonyl red, and azomethines such as copper azomethine yellow Pigments, quinophthalone pigments such as quinophthalone yellow, isoindoline pigments such as isoindoline yellow, nitroso such as nickel dioxime yellow Pigments, perinone pigments such as perinone orange, quinacridone pigments such as quinacridone magenta, quinacridone maroon, quinacridone scarlet and quinacridone red, perylene pigments such as perylene red and perylene maroon, and pyrrolopyrrole pigments such as diketopyrrolopyrrole red Organic pigments such as dioxazine pigments such as dioxazine violet, carbon black, lamp black, furnace black, ivory black, carbon pigments such as graphite and fullerene, chromate pigments such as chrome lead and molybdate orange, cadmium Yellow, cadmium lithopone yellow, cadmium orange, cadmium lithopone orange, silver vermilion, cadmium red, cadmium lithopone red, sulfide pigments such as sulfide, ocher, titanium yellow , Titanium barium nickel yellow, red rice, red lead, amber, brown iron oxide, zinc iron chrome brown, chromium oxide, cobalt green, cobalt chrome green, titanium cobalt green, cobalt blue, cerulean blue, cobalt aluminum chrome blue, iron black, Oxide pigments such as manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, hydroxide pigments such as viridian, ferrocyanide pigments such as bitumen,
Examples include silicate pigments such as ultramarine, phosphate pigments such as cobalt violet and mineral violet, and other inorganic pigments such as cadmium sulfide and cadmium selenide. Two or more kinds can be used in combination.

The dye is not particularly limited, and examples thereof include RuL ₂ (SCN) ₂ and RuL ₂ C.
metal complex dyes such as l ₂ , RuL ₂ CN ₂ , Rutenium 535-bisTBA (manufactured by Solaronics), [RuL ₂ (NCS) ₂ ] ₂ H ₂ O, cyan dyes, xanthene dyes, azo dyes, hibiscus dyes , Blackberry pigments, raspberry pigments, pomegranate juice pigments, chlorophyll pigments, etc., and one or more of these can be used in combination. Note that L in the composition formula is 2,2′-bipyridin.
e or a derivative thereof.

On the upper surface of the electron transport layer 4 on which the dye layer D is formed, a layered (flat plate) hole transport layer 5 is provided. In other words, the hole transport layer 5 is disposed to face the first electrode 3 through the electron transport layer 4 on which the dye layer D is formed. The hole transport layer 5 has a function of capturing and transporting holes generated in the dye layer D. In other words, the hole transport layer 5 has a function of transporting holes to the external circuit 100 via a second electrode 6 described later or the hole transport layer 5 itself becomes an electrode.

The average thickness of the hole transport layer 5 is not particularly limited. For example, it is preferably about 1 to 500 μm, more preferably about 10 to 300 μm, and further preferably about 10 to 30 μm. .

Examples of the constituent material of the hole transport layer 5 include substances having various ion conduction characteristics, triphenyldiamine (monomers, polymers, etc.), polyaniline, polypyrrole, polythiophene, phthalocyanine compounds (for example, copper phthalocyanine) or derivatives thereof. Various p-type semiconductor materials such as aluminum, nickel, cobalt, platinum, silver, gold, copper,
Examples thereof include metals such as molybdenum, titanium, and tantalum, and alloys containing these. One or more of these can be used in combination, but in particular, a substance having ion conduction characteristics is preferably used. .

That is, it is preferable that the hole transport layer 5 is mainly composed of a substance having ion conduction characteristics. Thereby, the hole transport layer 5 can transport holes generated in the dye layer D more efficiently.

At this time, the hole transport material constituting the hole transport layer 5 is preferably a p-type inorganic semiconductor or a p-type compound semiconductor material having ion conduction characteristics, and the electron transport material in the electron transport layer When TiO ₂ is used, since the band gap of TiO ₂ is 2.2 eV, the band gap of the hole transport material constituting the hole transport layer 5 needs to be 2.2 eV or more.
In addition, examples of the substance having the ion conduction characteristics include metal halide compounds such as metal iodide compounds such as CuI and AgI, metal bromide compounds such as AgBr, and CuSC.
Examples include thiocyanate metal salts (rhodanide metal compounds) such as N, and one of these
Species or a combination of two or more can be used.

Among these, metal halide compounds such as metal iodide compounds and metal bromide compounds are preferable as substances having ion conduction characteristics. The metal halide compound is particularly excellent in ion conduction characteristics.

Furthermore, it is particularly preferable to use one or more of metal iodide compounds such as CuI and AgI in combination as the substance having ion conduction characteristics. Metal iodide compounds are extremely excellent in ion conduction characteristics. For this reason, by using a metal iodide compound as the main material of the hole transport layer 5, the photoelectric conversion efficiency (energy conversion efficiency) of the solar cell 1A can be further improved.

Further, as shown in FIG. 2, the hole transport layer 5 has holes 4 in the electron transport layer 4 on which the dye layer D is formed.
1 is formed. As a result, the contact area between the dye layer D and the hole transport layer 5 can be increased, so that holes generated in the dye layer D can be transmitted to the hole transport layer 5 more efficiently. it can. As a result, the solar cell 1A can further improve the power generation efficiency.

  On the upper surface of the hole transport layer 5, a layered (flat plate) second electrode 6 is provided.

The average thickness of the second electrode 6 is appropriately set depending on the material, application, etc., and is not particularly limited.

The constituent material of the second electrode 6 is, for example, a metal such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum or an alloy containing these metals, or a graphite. Various carbon materials etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.

Further, since the photoelectric conversion element of the present invention is a photochemical element, the second electrode 6 and the hole transport layer 5 are used.
An interface is formed between the catalyst layer and the catalyst layer.

Since the conventional dye-sensitized wet photoelectric conversion element uses an electrolytic solution made of an iodine solution or the like for the hole transport layer, between the second electrode 6 and the electron transport layer 4 that adsorbs the dye, A gap of a certain distance was formed using a spacer or the like, and the gap was filled with an electrolyte solution as a hole transport layer.

Such conventional dye-sensitized wet solar cells and K. Tennakone, GRRA Kumara, IRM
Kottegoda, KGU Wijiayantha, and VPS Perera: J. Phys. D: Appl. Phys. 31 (199
8) The conventional solid-state dye-sensitized solar cell disclosed in 1492, etc., clips the substrate on which the second electrode is formed and the substrate on which the electron transport layer 4 on which the dye is adsorbed is formed. The hole transport layer and the second electrode are pressed against each other and physically contacted by pressing, and there is a problem that the contact resistance is large.

However, in the completely solid dye-sensitized photoelectric conversion element of the present invention, an interface is formed between the second electrode 6 and the hole transport layer 5, and a catalyst layer is formed at this interface. This is different from the above-described conventional dye-sensitized solar cell and the like.

The interface state of the interface comprising the hole transport layer 5 and the catalyst layer of the completely solid dye-sensitized photoelectric conversion element of the present invention is preferably 0.1 to 0.0001 eV, and more preferably an interface state. Is 0.01 to 0.001 eV.

In the present invention, the catalyst layer on the hole transport layer 5 is formed by a wet process (wet) method such as spin coating, printing, spray coating, coating, etc. An interface is formed between them. In the subsequent step of these wet processes (wet processes), the catalyst layer may be dried and fired.

In the present invention, the catalyst layer on the hole transport layer 5 is formed by sputtering, vapor deposition, or CVD.
A dry process (dry type) method such as a method is used to form an interface between the hole transport layer 5 and the catalyst layer.

As the catalyst layer, Pt (platinum), Pt—Ru (platinum-ruthenium), Au (gold), or the like is used. In the present invention, various carbon materials such as graphite are optimal.

Examples of carbon materials include graphite, graphite, diamond, carbon nanotubes,
Any one or more of fullerene (C60) or the like is used.

In order to increase the strength of the carbon material, carbon fibers may be woven into these carbon materials. As the carbon fiber, a fiber made by carbonizing an organic fiber such as rayon or polyacrylonitrile or a fiber made by spinning a refined petroleum pitch in an inert gas is used.

In particular, the carbon fiber made of polyacrylonitrile has high elasticity and high strength, and a composite agent obtained by hardening the carbon fiber with the above-described carbon material and resin is optimal as the catalyst layer of the present invention.

  Carbon fiber and resin have electrical conductivity.

Furthermore, in order to form a tighter interface between the second electrode 6 and the hole transport layer 5, it is necessary to form the hole transport layer more smoothly.

The surface of the hole transport layer on the side that forms the interface with the catalyst layer is desirably flat, and the surface roughness on the surface that forms the interface with the catalyst layer of the hole transport layer has an Rmax (maximum surface roughness) of 10 μm. Desirably, Ra (average surface roughness) is desirably 5 μm or less.

Further, the surface roughness of the formed catalyst layer is preferably Rmax (maximum surface roughness) of 10 μm or less, and Ra (average surface roughness) of 5 μm or less.

In such a solar cell 1A, as shown in FIG. 5, when light is incident, electrons are excited mainly in the dye layer D to generate electrons (e ⁻ ) and holes (h ⁺ ). Among these, electrons move to the electron transport layer 4, holes move to the hole transport layer 5, and between the first electrode 3 and the second electrode 6,
A potential difference (photoelectromotive force) is generated, and a current (photoexcitation current) flows through the external circuit 100.

The values of Vaccum Energy shown in FIG. 5 are the electron transport layer 4 and the barrier layer 8.
Is an example in which is made of titanium dioxide and the hole transport layer 5 is made of CuI.

When this state is represented by an equivalent circuit, a current circulation circuit having a diode 200 as shown in FIG. 6 is formed.

It should be noted that electrons and holes are generated simultaneously in the dye layer D by light irradiation (light reception).
In the following description, for convenience, it is described as “electrons are generated”.

Now, the present invention is characterized in that a short-circuit prevention means for preventing or suppressing a short-circuit (leakage) between the first electrode 3 and the hole transport layer 5 is provided.

  Hereinafter, this short-circuit prevention means will be described in detail.

In the present embodiment, as a short-circuit preventing means, a barrier layer 8 is provided which is in the form of a film (layer) and is located between the first electrode 3 and the electron transport layer 4. The barrier layer 8 is formed so that the porosity is smaller than the porosity of the electron transport layer 4.

When manufacturing the solar cell 1A, as will be described later, for example, a hole transport layer material is applied to the upper surface of the electron transport layer 4 on which the dye layer D is formed by a coating method.

In this case, in the solar cell in which the barrier layer 8 is not provided, if the porosity of the electron transport layer 4 is increased, the hole transport layer material may pass through the holes 41 of the electron transport layer 4 in which the dye layer D is formed. It may penetrate and reach the first electrode 3 in some cases. That is, in a solar cell that does not have the barrier layer 8, contact (short circuit) occurs between the first electrode 3 and the hole transport layer 5, thereby increasing leakage current and generating efficiency (photoelectric conversion efficiency). May be reduced.

On the other hand, in the solar cell 1 </ b> A provided with the barrier layer 8, the above-described disadvantages are prevented, and a decrease in power generation efficiency is preferably prevented or suppressed.

Further, when the porosity of the barrier layer 8 is A [%] and the porosity of the electron transport layer 4 is B [%], the B / A is preferably about 1.1 or more, for example. More preferably, it is about 5 or more, more preferably about 10 or more. Thereby, the barrier layer 8 and the electron transport layer 4 can each exhibit their functions more suitably.

More specifically, the porosity A of the barrier layer 8 is, for example, preferably about 20% or less, more preferably about 5% or less, and still more preferably about 2% or less. . That is, the barrier layer 8 is preferably a dense layer. Thereby, the said effect can be improved more.

Furthermore, the ratio of the thickness of the barrier layer 8 and the electron transport layer 4 is not particularly limited.
It is preferably about 1:99 to 60:40, more preferably about 10:90 to 40:60. In other words, the ratio of the thickness occupied by the barrier layer 8 in the whole of the barrier layer 8 and the electron transport layer 4 is preferably about 1 to 60%, and more preferably about 10 to 40%. As a result, the barrier layer 8 can more reliably prevent or suppress a short circuit due to contact between the first electrode 3 and the hole transport layer 5, and the light arrival rate to the dye layer D is reduced. This can be suitably prevented.

More specifically, the average thickness (film thickness) of the barrier layer 8 is, for example, 0.01 to 10 μm.
m is preferably about 0.1 to 5 μm, more preferably about 0.5 to 2 μm.
More preferably, it is about m. Thereby, the said effect can be improved more.

The constituent material of the barrier layer 8 is not particularly limited. For example, in addition to titanium oxide which is the main constituent material of the electron transport layer 4, for example, SrTiO ₃ , ZnO, SiO ₂ , Al ₂ O ₃
, Various metal oxides such as SnO ₂ , CdS, CdSe, TiC, Si ₃ N ₄ , SiC, B ₄
N, BN and various metal compounds can be used alone or in combination of two or more. Among these, it is preferable to have an electrical conductivity equivalent to that of the electron transport layer 4, and in particular, Those mainly composed of titanium oxide are more preferable. By configuring the barrier layer 8 with such a material, electrons generated in the dye layer D can be more efficiently converted from the electron transport layer 4 to the barrier layer 8.
As a result, the power generation efficiency of the solar cell 1A can be further improved.

The resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 are not particularly limited, but the resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 as a whole, that is, the barrier layer 8 and The resistance value in the thickness direction of the laminate with the electron transport layer 4 is preferably about 100 Ω / cm ² or more, and more preferably about 1 kΩ / cm ² or more. Thereby, the leak (short circuit) between the 1st electrode 3 and the positive hole transport layer 5 can be prevented or suppressed more reliably, and the advantage that the fall of the power generation efficiency of 1 A of solar cells can be prevented. There is.

Further, the interface between the barrier layer 8 and the electron transport layer 4 may not be clear or may be clear, but it is preferable that the interface is not clear (unclear). That is, it is preferable that the barrier layer 8 and the electron transport layer 4 are integrally formed and partially overlap each other. Thereby, the transmission of electrons between the barrier layer 8 and the electron transport layer 4 can be performed more reliably (efficiently).

Further, the barrier layer 8 and the electron transport layer 4 are formed using materials having the same composition (for example, a material mainly composed of titanium dioxide), and only their porosity is different, that is, the electron transport layer. 4 may be configured such that a part of 4 functions as the barrier layer 8.

In this case, the electron transport layer 4 has a dense portion and a rough portion in the thickness direction, and the dense portion functions as the barrier layer 8.

In this case, the dense portion is preferably formed on the first electrode 3 side of the electron transport layer 4, but can also be formed at an arbitrary position in the thickness direction.

Further, in this case, the electron transport layer 4 may have a configuration having a portion where a rough portion is sandwiched between dense portions or a configuration having a portion where a dense portion is sandwiched between rough portions. Good.

In such a solar cell 1A, the photoelectric conversion efficiency when the incident angle of light to the dye layer D (the electron transport layer 4 on which the dye layer D is formed) is 90 ° is R _90, and the incident angle of light is 52 °. When the photoelectric conversion efficiency at R ₅₂ is R ₅₂ , R ₅₂ / R ₉₀ preferably has a characteristic of about 0.8 or more, more preferably about 0.85 or more. Satisfying these conditions means
That is, the electron transport layer 4 on which the dye layer D is formed has low directivity with respect to light, that is, isotropic. Therefore, such a solar cell 1A can generate power more efficiently over almost the entire solar sunshine duration.

Furthermore, in the solar cell 1A, when a voltage of 0.5 V is applied so that the first electrode 3 is positive and the second electrode 6 (hole transport layer 5) is negative, the resistance value is For example, 100Ω / c
It preferably has a characteristic of about m ² or more, and more preferably has a characteristic of about 1 kΩ / cm ² or more. Having such characteristics indicates that in the solar cell 1A, a short circuit (leakage) due to contact or the like between the first electrode 3 and the hole transport layer 5 is preferably prevented or suppressed. Is. Therefore, in such a solar cell 1A, the power generation efficiency (photoelectric conversion efficiency) can be further improved.

  Such a solar cell 1A can be manufactured as follows, for example.

First, a substrate 2 made of, for example, soda glass is prepared. A substrate having a uniform thickness and no deflection is preferably used for the substrate 2.

<1> First, the first electrode 3 is formed on the upper surface of the substrate 2.
The first electrode 3 can be formed by using, for example, a vapor deposition method, a sputtering method, a printing method, or the like as the material of the first electrode 3 made of, for example, FTO.

<2> Next, the barrier layer 8 is formed on the upper surface of the first electrode 3.
The barrier layer 8 can be formed by, for example, a sol-gel method, a vapor deposition (vacuum vapor deposition) method, a sputtering method (high frequency sputtering, DC sputtering), a spray pyrolysis method, a jet mold (plasma spraying) method, a CVD method, or the like. Of these, the sol-gel method is preferable.

This sol-gel method is very easy to operate. For example, it can be used in combination with various coating methods such as dipping, dripping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc. However, the barrier layer 8 can be suitably formed into a film shape (thick film and thin film).

Further, according to the coating method, the barrier layer 8 having a desired pattern shape can be easily obtained by performing masking using a mask or the like, for example.

As this sol-gel method, a method of preventing (preventing) the reaction (for example, hydrolysis, polycondensation, etc.) of a titanium compound (organic or inorganic) described later in the barrier layer material (hereinafter referred to as “M”).
"OD (Metal Organic Deposition or Metal Organic Decomposition) method". )
Alternatively, a method allowing this is mentioned, but it is particularly preferable to use the MOD method.

According to this MOD method, the stability of the titanium compound (organic or inorganic) in the barrier layer material is maintained, and the barrier layer 8 is more easily and reliably (with good reproducibility) and dense (within the above range). Inside porosity).

In particular, organic titanium such as titanium alkoxide (metal alkoxide) that is chemically very unstable (decomposable) such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, etc. Dense T using compound
This MOD method is optimal when forming an iO ₂ layer (the barrier layer 8 of the present invention).

  Hereinafter, a method of forming the barrier layer 8 by the MOD method will be described.

[Preparation of barrier layer material]
For example, one or a combination of two or more organic titanium compounds such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium alkoxide (metal alkoxide) such as titanium tetrabutoxide When this is used, first, this organotitanium compound (or this solution) is mixed with, for example, absolute ethanol, 2
-It melt | dissolves in organic solvents (or these mixed solvents), such as butanol, 2-propanol, and 2-n-butoxyethanol.

Thereby, the concentration (content) of the organic titanium compound in the solution is prepared (for example, 0.1 to 0.1).
The viscosity of the obtained barrier layer material is adjusted.
The viscosity of the barrier layer material is appropriately set depending on the type of coating method and the like, and is not particularly limited. However, when spin coating is used, a high viscosity (for example, 0.5 to 20) is preferable.
When using spray coating, the viscosity is preferably low (for example, about 0.1 to 2 cP (room temperature)).

Next, an additive having a function of stabilizing the titanium alkoxide (metal alkoxide) such as titanium tetrachloride, acetic acid, acetylacetone, triethanolamine, diethanolamine is added to the solution.

By adding these additives, these additives replace the alkoxide (alkoxyl group) coordinated to the titanium atom in the titanium alkoxide, and coordinate to the titanium atom. Thereby, hydrolysis of titanium alkoxide is suppressed and stabilized. That is, these additives function as a hydrolysis inhibitor that inhibits hydrolysis of titanium alkoxide. In this case, the compounding ratio of this additive and titanium alkoxide is not particularly limited, but is preferably about 1: 2 to 8: 1 in terms of a molar ratio, for example.

More specifically, when diethanolamine is coordinated to titanium alkoxide, it replaces (substitutes) the alkoxide (alkoxyl group) of titanium alkoxide, and two molecules of diethanolamine are coordinated to the titanium atom. The compound substituted with diethanolamine is a compound that is more stable in producing titanium dioxide than titanium alkoxide.

  The same applies to other combinations.

  Thereby, a barrier layer material (a sol solution for forming a barrier layer: a sol solution for MOD) is obtained.

When an inorganic titanium compound such as titanium tetrachloride (TTC) is used, this inorganic titanium compound (or this solution) is mixed with absolute ethanol, 2-butanol, 2-propanol,
By dissolving in an organic solvent (or a mixed solvent thereof) such as 2-n-butoxyethanol, the organic solvent coordinates to titanium and becomes a stable compound without adding an additive.

Furthermore, when an organic titanium compound such as titanium oxyacetylacetonate (TOA) is used, this organic titanium compound (or this solution) is stable by itself, and thus stable when dissolved in the organic solvent. A barrier layer material can be obtained.

In the present invention, when the barrier layer 8 is formed by the MOD method, it is optimal to use a solution prepared by the following method among the three solutions described above. That is, titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide,
An organic titanium compound such as titanium alkoxide such as titanium tetrabutoxide (or this solution) is dissolved (or diluted) with a solvent, and additives such as titanium tetrachloride, acetic acid, acetylacetone, triethanolamine, diethanolamine are added to this solution. It is optimal to use a solution prepared by the method of addition. According to this method, a compound stabilized in producing titanium dioxide by coordinating the additive to the titanium atom of the titanium alkoxide can be obtained.

Thereby, a chemically unstable titanium alkoxide can be made into a chemically stable compound. Such a compound is extremely useful in forming the barrier layer 8 of the present embodiment, that is, the dense barrier layer 8 mainly composed of titanium dioxide.

[Formation of barrier layer 8]
A barrier layer material is applied to the upper surface of the first electrode 3 by a coating method (for example, spin coating) to form a film. When spin coating is used as the coating method, the rotational speed is 500 to 40.
It is preferable to carry out at about 00 rpm.

Next, heat treatment is applied to the coating film. Thereby, the organic solvent is volatilized and removed. The heat treatment conditions are preferably about 50 to 250 ° C. and about 1 to 60 minutes, more preferably about 100 to 200 ° C. and about 5 to 30 minutes.

Such heat treatment can be performed, for example, in the atmosphere or in nitrogen gas, and for example, various inert gases, vacuum, reduced pressure conditions (for example, 1 × 10 ⁻¹ to 1 × 10 ⁻⁶ Torr), etc. It may be performed in an oxidizing atmosphere.

Note that the barrier layer material may be applied to the upper surface of the first electrode 3 while the first electrode 3 is heated.

Further, the coating film is subjected to heat treatment at a temperature higher than the heat treatment. As a result, organic components remaining in the coating film are removed, and titanium dioxide (TiO ₂ ) is sintered to form a barrier layer 8 made of titanium dioxide having an amorphous or anatase type crystal structure. The heat treatment condition is preferably about 300 to 700 ° C. for about 1 to 70 minutes, more preferably about 400 to 550 ° C. for about 5 to 45 minutes.

  In addition, the atmosphere of this heat processing can be made into the atmosphere similar to the said heat processing.

The above operation is preferably performed about 1 to 20 times, more preferably about 1 to 10 times to form the barrier layer 8 having the average thickness as described above.

In this case, the thickness (film thickness) of the coating film obtained by one operation is preferably about 100 nm or less, and more preferably about 50 nm or less. By laminating such thin films to form the barrier layer 8, the barrier layer 8 can be made more uniform and dense. Moreover, adjustment of the film thickness obtained by the said operation of 1 time can be easily performed by adjusting the viscosity of barrier layer material.

Prior to the formation of the barrier layer 8, the upper surface of the first electrode 3 is subjected to, for example, O ₂ plasma treatment, EB treatment, cleaning treatment with an organic solvent (eg, ethanol, acetone, etc.), etc. You may make it remove the organic substance adhering to the upper surface of the 1st electrode 3. FIG. in this case,
A mask layer is formed on the upper surface of the first electrode 3 except for a portion where the barrier layer 8 is to be formed and masked. The mask layer may be removed after the barrier layer 8 is formed, or may be removed after the solar cell 1A is completed.

<3> Next, the electron transport layer 4 is formed on the upper surface of the barrier layer 8.
The electron transport layer 4 can be formed by, for example, a sol / gel method, a vapor deposition method, a sputtering method, or the like. Among these, it is preferable to form the electron transport layer 4 by a sol / gel method.

This sol-gel method is very easy to operate. For example, it can be used in combination with various coating methods such as dipping, dripping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc. The electron transport layer 4 is preferably used.
Can be formed into a film (thick film and thin film).

Further, according to the coating method, for example, by performing masking using a mask or the like, the electron transport layer 4 having a desired pattern shape can be easily obtained.

For the formation of the electron transport layer 4, it is preferable to use a sol solution containing powder of the electron transport layer material. Thereby, the electron carrying layer 4 can be made more easily and reliably porous.

Although it does not specifically limit as an average particle diameter of the powder of electron transport layer material, For example, 1 nm-1
It is preferably about μm, and more preferably about 5 to 50 nm. By setting the average particle diameter of the powder of the electron transport layer material within the above range, the uniformity of the powder of the electron transport layer material in the sol liquid can be improved. Moreover, since the surface area (specific surface area) of the obtained electron transport layer 4 can be increased by reducing the average particle diameter of the powder of the electron transport layer material in this way, the formation region (formation of the dye layer D) Area) can be increased, which contributes to the improvement of the power generation efficiency of the solar cell 1A.

  Below, an example of the formation method of the electron carrying layer 4 is demonstrated.

[Preparation of titanium oxide powder (electron transport layer material powder)]
<3-A0> A rutile-type titanium dioxide powder and anatase-type titanium dioxide powder are blended at a predetermined blending ratio (including only anatase-type titanium dioxide powder and only rutile-type titanium dioxide powder). Mix.

The average particle size of these rutile type titanium dioxide powders and the average particle size of anatase type titanium dioxide powders may be different or the same, but are preferably different.

  In addition, the average particle diameter as a whole titanium oxide powder shall be the above-mentioned range.

Also, instead of the titanium dioxide powder or mixed with the titanium dioxide powder,
Nanotube (body) crystalline titania (titania nanotubes) may be used alone or as a mixture.

The average size of the titania nanotubes at this time was 5 nm in inner diameter, 8 nm in outer diameter, and 70 nm in length. The average specific surface area of the titania nanotube is 400 m ² / g.
Met.

[Preparation of sol solution (electron transport layer material)]
<3-A1> First, for example, titanium alkoxides such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, and organic titanium compounds such as titanium oxyacetylacetonate (TOA) Or an organic solvent such as anhydrous ethanol, 2-butanol, 2-propanol, 2-n-butoxyethanol, or a combination of one or more inorganic titanium compounds such as titanium tetrachloride (TTC). (Or a mixed solvent thereof).

At this time, although it does not specifically limit as a density | concentration (content) in the solution of a titanium compound (organic or inorganic), For example, it is preferable to set it as about 0.1-3 mol / L.

Next, various additives are added to this solution as necessary. As an organic titanium compound,
For example, when titanium alkoxide is used, since titanium alkoxide has low chemical stability, for example, an additive such as acetic acid, acetylacetone, and nitric acid is added. Thereby, titanium alkoxide can be made into a chemically stable compound. In this case, the compounding ratio of the additive and titanium alkoxide is not particularly limited.
: It is preferable to set it as about 2-8: 1.

<3-A2> Next, water, such as distilled water, ultrapure water, ion-exchange water, RO water, is mixed with this solution, for example. The mixing ratio of water and titanium compound (organic or inorganic) is 1:
It is preferably about 4 to 4: 1.

<3-A3> Next, the solution is mixed with the titanium oxide powder or titania nanotube prepared in the above-mentioned step <3-A0> to obtain a suspension (dispersion) liquid.

<3-A4> Further, the suspension is diluted with the organic solvent (or mixed solvent). Thereby, a sol solution is prepared. The dilution factor is preferably about 1.2 to 3.5 times, for example.

Further, the content in the sol solution of titanium oxide powder (electron transport layer material powder) or titania nanotube is not particularly limited, but is preferably about 0.1 to 10 wt% (wt%), for example, More preferably, it is about 0.5 to 5 wt%. Thereby, the porosity of the electron carrying layer 4 can be made into the said range suitably.

[Formation of Electron Transport Layer (Titanium Oxide Layer) 4]
<3-A5> While the barrier layer 8 is preferably heated, a sol solution is applied to the upper surface of the barrier layer 8 by a coating method (for example, dropping) to obtain a film-like body (coating film). Although it does not specifically limit as this heating temperature, For example, it is preferable that it is about 80-180 degreeC, and it is 100-16.
More preferably, it is about 0 ° C.

The above operation is preferably performed about 1 to 10 times, more preferably about 5 to 7 times, to form the electron transport layer 4 having the average thickness as described above.

Next, if necessary, the electron transport layer 4 may be reduced to 0 at a temperature of about 250 to 500 ° C., for example.
. You may perform heat processing (for example, baking etc.) for about 5 to 3 hours.

<3-A6> The electron transport layer 4 obtained in the step <3-A5> can be post-treated as necessary.

As this post-processing, for example, machining such as grinding and polishing for adjusting the shape (
Post-processing), and other post-treatments such as cleaning and chemical treatment.

Moreover, the electron carrying layer 4 can also be formed as follows, for example. Hereinafter, another method for forming the electron transport layer 4 will be described. In the following description, differences from the above-described formation method will be mainly described, and description of similar matters will be omitted.

[Preparation of titanium oxide powder (electron transport layer material powder)]
<3-B0> A step similar to the step <3-A0> is performed.

[Preparation of coating solution (electron transport layer material)]
<3-B1> First, the titanium oxide powder or titania nanotube prepared in the above step is suspended in an appropriate amount of water (for example, distilled water, ultrapure water, ion-exchanged water, RO water, or the like).

<3-B2> Next, for example, a stabilizer such as nitric acid is added to the suspension, and the agate (
Or kneaded sufficiently in a mortar made of alumina.

<3-B3> Next, the above water is added to the suspension and further kneaded.
At this time, the mixing ratio of the stabilizer and water is preferably 10:90 to 40: 6 in volume ratio.
About 0, more preferably about 15:85 to 30:70, and the viscosity of the suspension is, for example, about 0.2 to 30 cP (normal temperature).

<3-B4> Then, a surfactant is added to the suspension so as to have a final concentration of about 0.01 to 5 wt%, and the mixture is kneaded. Thereby, a coating liquid (electron transport layer material) is prepared.

The surfactant may be cationic, anionic, amphoteric or nonionic, but preferably a nonionic one.

Further, as the stabilizer, a surface modifying reagent of titanium oxide such as acetic acid or acetylacetone can be used instead of nitric acid.

Moreover, you may add various additives, such as binders, such as polyethylene glycol, a plasticizer, antioxidant, in a coating liquid (electron transport layer material) as needed.

[Formation of Electron Transport Layer (Titanium Oxide Layer) 4]
<3-B5> A coating solution is applied and dried on the upper surface of the first electrode 3 by a coating method (for example, dipping) to form a film-like body (coating film). Alternatively, the coating and drying operations may be performed a plurality of times for lamination. Thereby, the electron transport layer 4 is obtained.

Next, if necessary, the electron transport layer 4 may be reduced to 0 at a temperature of about 250 to 500 ° C., for example.
. You may perform heat processing (for example, baking etc.) for about 5 to 3 hours. As a result, the titanium oxide powders that have merely stopped contacting each other are diffused at the contact sites, and the titanium oxide powders are fixed (fixed) to a certain extent. In this state, the electron transport layer 4 becomes porous.

  <3-B6> A step similar to the step <3-A6> is performed.

  The electron transport layer 4 is obtained through the above steps.

<4> Next, the electron transport layer 4 and a liquid containing a pigment as described above (for example, a solution in which a pigment is dissolved in a solvent, a suspension in which a pigment is suspended in a solvent) are immersed, applied, or the like. Thus, the dye layer D is formed on the outer surface of the electron transport layer 4 and the inner surface of the hole 41 by, for example, adsorption or bonding.

More specifically, a laminate of the substrate 2, the first electrode 3, the barrier layer 8 and the electron transport layer 4 is formed.
By immersing in the liquid containing the dye, the dye layer D can be easily formed along the outer surface of the electron transport layer 4 and the inner surface of the hole 41.

The solvent (liquid) for dissolving or suspending (dispersing) the dye is not particularly limited. For example, various water, methanol, ethanol, isopropyl alcohol, acetonitrile, ethyl acetate, ether, methylene chloride, NMP (N-methyl- 2-pyrrolidone) and the like, and one or more of them can be used in combination.

Thereafter, the laminate is taken out from the solution (suspension), and the solvent is removed by, for example, a method of natural drying or a method of blowing a gas such as air or nitrogen gas.

Further, if necessary, the laminate is made, for example, at a temperature of about 60 to 100 ° C., 0.5 to
You may dry with a clean oven etc. for about 2 hours. Thereby, a pigment | dye can be adsorb | sucked (bonded) to the electron carrying layer 4 more firmly.

<5> Next, the hole transport layer 5 is formed on the upper surface of the dye layer D (the electron transport layer 4 on which the dye layer D is formed).
The hole transport layer 5 is formed by, for example, dipping a hole transport layer material (electrode material) containing a substance having ion conduction characteristics such as CuI on the upper surface of the electron transport layer 4 on which the dye layer D is formed.
It is preferably formed by coating by various coating methods such as dripping, doctor blade, spin coating, brush coating, spray coating, and roll coater.

According to such a coating method, the hole transport layer 5 is replaced with the hole 4 of the electron transport layer 4 on which the dye layer D is formed.
1 can be formed so as to penetrate more reliably.

In addition, these coating methods are performed on the upper surface of the dye layer D in a state where the substrate 2 on which the dye layer D is formed on the electron transport layer 4 is placed in a container at least depressurized from the atmospheric pressure. It is desirable that the hole transport layer 5 is applied by the various application methods described above.

More specifically, a decompression chamber shown in FIG. 7 is used. As shown in FIG. 7, this decompression chamber is composed of, for example, an upper structure 80 and a lower structure 79. The decompression chamber is positioned by a positioning port 76 and a positioning pin 77 and is sealed by a sealing member 81 made of silicon rubber or the like. The structure is a structure that is closely attached by caulking with a nut and a bolt.

The decompression chamber has a suction port 78, a decompression valve (valve) 74, and a decompression chamber 75, and the suction port 78 is connected to a vacuum pump. When the vacuum pump is operated with the decompression valve 74 opened, the interior of the decompression chamber 75 is decompressed and, as described above, 1 × 10 ⁻¹ to 1 × 10.
It becomes a vacuum state of about ^-6 torr.

In this sealed chamber, the substrate 2 on which the dye layer D is formed on the electron transport layer 4 is placed, and this chamber is evacuated. Thereafter, a dye layer formed on the electron transport layer 4 in a state where the needle 71 of the syringe 73 containing a hole transport material is inserted into the silicon rubber provided on the substrate 2 of the chamber and the hermetic state is not broken. The hole transport material in the syringe is slowly dropped on D and applied.

The amount of the hole transport material dripped onto the substrate at this time is 1 to 0.00 with respect to an area of 1 cm ² .
001 mL per minute.

Further, depending on the coating method, the start of dropping of the hole transport material onto the dye layer is started 1 to 5 minutes after the inside of the decompression chamber is in a decompressed state.

In this way, when the hole transport layer is applied on the substrate 2 on which the dye layer D is formed on the electron transport layer 4, if the coating process is performed under reduced pressure, the dye layer D is formed in the electron transport layer. Air (gas) in the voids in the porous layer can be degassed.

Therefore, it is possible to further assist the penetration of CuI into the TiO ₂ layer formed in the nanoporous state.

The reduced pressure state at this time is performed in a state lower than the atmospheric pressure, but more specifically, 1 ×
10 ⁻¹ to 1 × 10 ⁻⁶ torr is preferable, and 1 × 10 ⁻¹ to 1 is more preferable.
More desirably, it is × 10 ⁻³ torr.

The average thickness of the hole transport layer 5 formed by the coating method is not particularly limited, but is preferably about 1 to 500 μm, more preferably about 10 to 300 μm, and more preferably 10 to 30 μm. More preferably, it is about.

Thereafter, the check valve 72 made of silicon rubber or the like provided on the substrate 2 placed in the decompression chamber 75 of the chamber is pierced with a needle 71 of a syringe 73 containing a hole transport material, and the vacuum chamber is airtight. The hole transport material in the syringe 71 is slowly dropped and applied onto the dye layer D formed on the electron transport layer 4 without being broken.

In addition, after the coating film is formed, the coating film may be subjected to heat treatment. However, the coating on the upper surface of the electron transport layer 4 on which the dye layer D of the hole transport layer material is formed is performed by applying the dye layer D (dye layer D). It is preferable to carry out the heating while heating the electron transport layer 4) on which the layer D has been formed. Thereby, the hole transport layer 5 is more quickly
That is, it is advantageous for shortening the manufacturing time of the solar cell 1A.

The heating temperature is preferably set to a temperature of about 50 to 150 ° C.
5-60 minutes. In addition, when performing heat treatment after coating film formation, before such heat treatment,
The coating film may be dried.

  The above operation may be repeated a plurality of times.

More specifically, on a hot plate heated to about 80 ° C., the substrate 2, the first electrode 3,
A laminate of the electron transport layer 4 on which the barrier layer 8 and the dye layer D are formed is placed, and the hole transport layer material is dropped on the upper surface of the electron transport layer 4 on which the dye layer D is formed, and dried. This operation is performed a plurality of times to form the hole transport layer 5 having the average thickness as described above.

In addition, as described above, when the hole transport material is applied in a reduced pressure state using a vacuum chamber, the application step is performed by installing the reduced pressure chamber on a hot plate heated to about 80 ° C.

Although it does not specifically limit as a solvent used for a positive hole transport layer material, For example, organic solvents, such as acetonitrile, ethanol, methanol, isopropyl alcohol, or 1 type, or 2 or more types, such as various water, can be used in combination. .

In addition, acetonitrile is preferably used as the solvent for dissolving the substance having ion conduction characteristics.

At this time, in the present invention, the hole transport layer material solution is 200 to 1 m with respect to 10 mL of the solvent.
A low concentration CuI solution prepared by dissolving g hole transport material is used.

More preferably, the solution of the hole transport layer material is 100 to 10 mg with respect to 10 mL of the solvent.
A low-concentration CuI solution prepared by dissolving the hole transporting material is used.

For example, when acetonitrile is used as the solvent, 10 mL of acetonitrile (7.8 g
), A low concentration CuI solution in which 2.5 to 0.05% CuI is dissolved by weight is used.

More preferably, the weight ratio is 1.5 to 10 mL (7.8 g) of acetonitrile.
A low concentration CuI solution in which 0.1% CuI is dissolved is used.

More specifically, a low concentration CuI solution in which 100 mg (1.28% by weight) of CuI is dissolved in 10 mL (7.8 g) of acetonitrile is used.

In this application method, the low-concentration CuI solution is applied to the dye layer by penetrating 2 to 100 times, and the application interval of the low-concentration CuI solution is determined after the solvent of the low-concentration CuI solution is volatilized or Apply continuously immediately before volatilization.

Thus, in the present invention, since the CuI solution having a low concentration is used, the amount of CuI in one application process can be reduced. Therefore, CuI is deposited on the upper surface of the TiO ₂ layer by volatilization of acetonitrile. Can solve the problem.

Further, as in the present invention, by continuously applying a low concentration CuI solution a plurality of times (about 2 to 100 times), acetonitrile as a solvent redissolves CuI deposited on the upper surface of the TiO ₂ layer, It is possible to assist the penetration of CuI into the TiO ₂ layer formed in the nanoporous state.

In addition, when a low concentration CuI solution is used as in the present invention, the amount of solvent in a unit solution can be increased, so that the time for volatilization of acetonitrile as a solvent can be lengthened.

Furthermore, in the present invention, a cyanoethylated product such as cyanoresin may be added as a binder to an acetonitrile solution of a substance having ion conduction characteristics. In this case, the cyanoethylated product with respect to the substance having ion conduction characteristics is 5% by mass ratio (weight ratio).
It is preferable to mix (blend) at ˜0.5 wt%.

Further, the hole transport layer material preferably contains a hole transport efficiency improving substance having a function of improving the hole transport efficiency. When the hole transport layer material contains this hole transport efficiency improving substance, the hole transport layer 5 has higher carrier mobility due to the improvement of ion conduction characteristics. As a result, the hole transport layer 5 has improved electrical conductivity.

The hole transport efficiency improving substance is not particularly limited, and examples thereof include halides such as ammonium halide, and particularly tetrapropylammonium iodide (TPA).
It is preferred to use ammonium halides such as I). As a hole transport efficiency improving substance,
By using ammonium halide, in particular, tetrapropylammonium iodide, the hole transport layer 5 is further improved in ionic conduction characteristics, thereby further increasing carrier mobility. As a result, the hole transport layer 5 is further improved in electrical conductivity.

The content of the hole transport efficiency improving substance in the hole transport layer material is not particularly limited, but is 1 ×
It is preferably about 10 ⁻⁴ to 1 × 10 ⁻¹ wt% (weight%), and 1 × 10 ⁻⁴ to 1 × 10 ^−2.
More preferably, it is about wt%. Within such a numerical range, the above-described effect becomes more remarkable.

In addition, when the hole transport layer 5 is composed mainly of a substance having ion conduction characteristics, the hole transport layer material increases in crystal size when the substance having ion conduction characteristics is crystallized. It is preferable to contain a crystal size coarsening-suppressing substance that suppresses this.

The substance for suppressing the coarsening of crystal size is not particularly limited, and examples thereof include thiocyanate (rhodanide) in addition to the aforementioned cyanoethylated substance and hole transport efficiency improving substance. Moreover, the crystal size coarsening inhibitor can be used alone or in combination of two or more thereof.

Examples of thiocyanate include sodium thiocyanate (NaSCN), potassium thiocyanate (KSCN), copper thiocyanate (CuSCN), and ammonium thiocyanate (NH ₄ SCN).

In addition, when a hole transport efficiency improving substance is used as the crystal size coarsening suppressing substance, ammonium halide is preferable. Among the materials that improve the hole transport efficiency, ammonium halide has a particularly excellent function of suppressing an increase in crystal size of a material having ion conduction characteristics.

Here, if the hole transport layer material does not contain this crystal size coarsening suppression substance, the substance having ion conduction characteristics may crystallize depending on the kind of substance having ion conduction characteristics, the heating temperature described above, and the like. In this case, the crystal size becomes too large, and the volume expansion of the crystal may proceed excessively. In particular, when such crystallization occurs in the pores (micropores) of the barrier layer 8, cracks occur in the barrier layer 8, and as a result, a partial transfer occurs between the hole transport layer 5 and the first electrode 3. May cause a short circuit due to contact.

Further, when the crystal size of the substance having ion conduction characteristics is increased, the contact property with the electron transport layer 4 on which the dye layer D is formed may be lowered depending on the kind of the substance having ion conduction characteristics. . As a result, the substance having ion conduction characteristics, that is, the hole transport layer 5 may be peeled off from the electron transport layer 4 on which the dye layer D is formed.

Therefore, such solar cells may have reduced device characteristics such as photoelectric conversion efficiency.

On the other hand, when the hole transport layer material contains this crystal size coarsening-suppressing substance, the substance having ion conduction characteristics is suppressed from increasing in crystal size, and the crystal size is extremely small or relatively small. It becomes.

For example, when thiocyanate is added to an acetonitrile solution of CuI, thiocyanate ions (SCN ⁻ ) are adsorbed around Cu atoms in CuI dissolved in a saturated state, and Cu—S (sulfur, Sulfor) is absorbed. ) Bonding occurs. As a result, the bonding between CuI molecules dissolved in a saturated state is remarkably inhibited, and as a result, CuI crystal growth can be prevented, so that a finely grown CuI crystal can be obtained.

For this reason, the solar cell 1A can suitably suppress the disadvantages caused by the coarsening of the crystal size of the substance having the ion conduction characteristics as described above.

Further, the content of the crystal size coarsening inhibitor in the hole transport layer material is not particularly limited, but is preferably about 1 × 10 ^{6 to} 10 wt% (weight%), and 1 × 10 ^−4. ~
More preferably, it is about 1 × 10 ⁻² wt%. Within such a numerical range, the above-described effect becomes more remarkable.

When the hole transport layer 5 is composed of the p-type semiconductor material as described above, the p-type semiconductor material is made of various organic solvents such as acetone, isopropyl alcohol (IPA), and ethanol (or these). The hole transport layer material is prepared by dissolving (or suspending) in a mixed solvent containing). Using this hole transport layer material, the hole transport layer 5 is formed (formed) in the same manner as described above.

<6> Next, the second electrode 6 is formed on the upper surface of the hole transport layer 5.
The second electrode 6 is made of, for example, a vapor deposition method using a material of the second electrode 6 made of, for example, platinum.
It can be formed by using a sputtering method, a printing method, or the like.

<7> Next, the photoelectric conversion element sandwiched between the first electrode and the second electrode 6 is plasticized by heat or light.
This treatment is a treatment for binding the hole transport layer made of CuI to the TiO ₂ layer adsorbing the plastic binder (conductive resin) and the dye more firmly, and further to adapt.

That is, by plasticizing a plastic binder (conductive resin) contained in a hole transport layer made of CuI or the like, the hole transport layer is sufficiently penetrated and adhered to the TiO ₂ layer formed in a nanoporous state.

The viscosity (20 ° C.) of the plastic binder (conductive resin) used at this time is 150 to 700.
0 cP is used, and the appearance is granular or viscous. More preferably, the viscosity (20 ° C.) of the plastic binder (conductive resin) is 240 to 1200 cP.

Further, the softening temperature of the plastic binder (conductive resin) is 25 to 200 ° C., more preferably, the softening temperature of the plastic binder (conductive resin) is 40 to 120 ° C.
Are particularly preferred.

The softening temperature of the plastic binder (conductive resin) needs to be a temperature at which the dye adsorbed by the heat of plastic processing of the binder is not destroyed.
Next, the plastic treatment method of the plastic binder (conductive resin) contained in the hole transport layer made of CuI or the like will be specifically described.

The first plastic processing method is a thermoplastic processing. This thermoplastic treatment is performed at a temperature of 25 to 250 ° C. and is continued for about 5 to 300 minutes.

The second plasticizing process is a photoplasticizing process. This photoplastic treatment is performed with a halogen or xenon light source, and is continued at a temperature of 25 to 250 ° C. for about 5 to 300 minutes.

  Through the steps as described above, the solar cell 1A is manufactured.

As mentioned above, although the photoelectric conversion element of this invention was demonstrated based on each embodiment of illustration, this invention is not limited to these. Each unit constituting the photoelectric conversion element can be replaced with any component that can exhibit the same function.

The photoelectric conversion element of the present invention may be a combination of any two or more configurations of the first and second embodiments.

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.

In the embodiment of the present invention described above, the hole transport layer of the photoelectric conversion element has been described using an example of a solid material such as CuI (copper iodide). However, in the present invention, hole transport is performed. Even if the layer is made of a liquid such as a conventional iodine solution, the effect of using the titania nanotube as the electron transport layer can be obtained. Therefore, (Example 2) shows an example of a dye-sensitized wet solar cell (Japanese Patent Laid-Open No. 1-220380) in the case where titania nanotubes are used for the electron transport layer.

  Next, specific examples of the present invention will be described.

Example 1
The solar cell (photoelectric conversion element) shown in FIG. 1 was manufactured as follows.

-0- First, a soda glass substrate having dimensions: length 30 mm × width 35 mm × thickness 1.0 mm was prepared. Next, this soda glass substrate was cleaned by immersing it in a cleaning solution (mixed solution of sulfuric acid and hydrogen peroxide solution) at 85 ° C. to clean the surface.

-1- Next, on the upper surface of the soda glass substrate, the dimensions: length 30 mm × width 35 by vapor deposition.
An FTO electrode (first electrode) of mm × thickness 1 μm was formed.

-2- Next, a barrier layer was formed in an area of 30 mm length × 30 mm width on the upper surface of the formed FTO electrode. This was done as follows.

[Preparation of barrier layer material]
First, titanium tetraisopropoxide (organic titanium compound) was dissolved in 2-n-butoxyethanol so as to be 0.5 mol / L.

Then, diethanolamine (additive) was added to this solution. The mixing ratio of diethanolamine and titanium tetraisopropoxide was 2: 1 (molar ratio).

Thereby, a barrier layer material was obtained. The viscosity of the barrier layer material was 3 cP (normal temperature).

[Formation of barrier layer]
The barrier layer material was applied by spin coating (coating method) to obtain a coating film. This spin coating was performed at a rotation speed of 1500 rpm.

Subsequently, the laminated body of the soda glass substrate, the FTO electrode, and the coating film was placed on a hot plate, and the coating film was dried by heat treatment at 160 ° C. for 10 minutes.

Further, the laminate was subjected to heat treatment in an oven at 480 ° C. for 30 minutes to remove organic components remaining in the coating film.

  Such an operation was repeated 10 times to laminate.

Thereby, a barrier layer having a porosity of less than 1% was obtained. The average thickness of this barrier layer is
It was 0.9 μm.

-3- Next, a titanium oxide layer (electron transport layer) was formed on the upper surface (whole) of the barrier layer. This was done as follows.

[Preparation of titanium oxide powder]
A titanium oxide powder made of a mixture of a rutile type titanium dioxide powder and an anatase type titanium dioxide powder was prepared. The average particle diameter of the titanium oxide powder is 40 nm, and the mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder is 60 by weight.
: 40.

Furthermore, a titania nanotube was prepared separately from the titanium dioxide powder. The diameter of the titania nanotube is 5 to 50 nm depending on the production conditions, and the length is 10 to 200 nm.
It is. Further, the specific surface area of the titania nanotube was about 200 to 600 m ² / g.

[Preparation of sol solution (titanium oxide layer material)]
First, titanium tetraisopropoxide was dissolved in 2-propanol so as to be 1 mol / L.

Next, acetic acid (additive) and distilled water were mixed with this solution. The mixing ratio of acetic acid and titanium tetraisopropoxide is 1: 1 (molar ratio), and the mixing ratio of distilled water and titanium tetraisopropoxide is 1: 1 (molar ratio). It was made to become.

Next, the prepared titanium oxide powder or titania nanotube was mixed with the solution. Further, this suspension was diluted 2-fold with 2-propanol. As a result, the sol solution (
Titanium oxide layer material) was prepared.

In addition, content in the sol liquid at the time of using a titanium oxide powder single-piece | unit was 0.1-10 wt%.

In addition, when the titania nanotube is used alone, the content in the sol solution is 0.1 to 10 wt.
%.

Furthermore, the content in the sol solution when a mixture of titanium oxide powder and titania nanotube was used was 0.1 to 10 wt%. At this time, the mixture ratio of titanium oxide powder and titania nanotube was set to 99: 1 to 1:99.

[Formation of titanium oxide layer]
A laminated body of soda glass substrate, FTO electrode and barrier layer is placed on a hot plate heated to 140 ° C., and a sol solution (titanium oxide layer material) is dropped onto the upper surface of the barrier layer (coating method)
And dried. This operation was repeated 7 times to laminate.

Thereby, a titanium oxide layer having a porosity of 34% was obtained. The average thickness of this titanium oxide layer was 7.2 μm.

The resistance value in the thickness direction of the entire barrier layer and titanium oxide layer is 1 kΩ / cm _2.
That was all.

-4- Next, the soda glass substrate, the FTO electrode, the barrier layer, and the titanium oxide layer are immersed in a saturated ethanol solution of ruthenium trisbipidyl (organic dye), then taken out from the ethanol solution, and then naturally dried. The ethanol was volatilized. In addition, 80
After drying in a clean oven at 0 ° C. for 0.5 hour, it was left overnight. Thereby, the dye layer was formed along the outer surface of the titanium oxide layer and the inner surface of the hole.

-5- Next, in a state where the laminated body of the titanium oxide layer on which the soda glass substrate, the FTO electrode, the barrier layer, and the dye layer D are formed is put in at least a reduced pressure chamber shown in FIG. The hole transport layer 5 is applied to the upper surface of the dye layer D by the various application methods.

More specifically, the substrate 2 on which the dye layer D is formed on the electron transport layer 4 is placed in a sealed chamber shown in FIG. 7, and this chamber is decompressed.

Next, with the pressure reducing valve (valve) 74 of the pressure reducing chamber opened, the vacuum pump is operated to reduce the pressure in the pressure reducing chamber 75 to a vacuum state of about 1 × 10 ⁻² torr.

Thereafter, a dye layer formed on the electron transport layer 4 in a state where the needle 71 of the syringe 73 containing a hole transport material is inserted into the silicon rubber provided on the substrate 2 of the chamber and the hermetic state is not broken. The hole transport material in the syringe is slowly dropped on D and applied.

The amount of the hole transport material dropped onto the substrate at this time is 0.01% with respect to an area of 1 cm ^2.
mL per minute.

In addition, depending on the said coating method, the start of dripping of the hole transport material onto the dye layer was started after 1 to 5 minutes had elapsed after the inside of the decompression chamber was in a decompressed state.

The average thickness of the hole transport layer 5 formed by the coating method was about 20 μm.

The decompression chamber was placed on a hot plate heated to 80 ° C., and a solution of CuI in acetonitrile (hole transport layer material) was dropped onto the top surface of the titanium oxide layer on which the dye layer D was formed and dried. It was.

This operation is repeated about 2 to 100 times so that the CuI solution sufficiently penetrates the TiO ₂ layer formed in the nanoporous state, and the dimensions are: length 30 mm × width 30 mm × thickness 20 μm.
m CuI layer (hole transport layer) was formed.

In the acetonitrile solution, tetrapropylammonium iodide was added as a hole transport efficiency improving substance so as to be 1 × 10 ⁻³ wt%.

Further, cyanoresin (cyanoethylated product) was added to the acetonitrile solution as a CuI binder. In addition, CuI and cyanoresin are 97 by mass ratio (weight ratio).
: Blended to be 3.

Furthermore, sodium thiocyanate (NaSCN) was added to the acetonitrile solution as a crystal size coarsening inhibitor so as to be 1 × 10 ⁻³ wt%.

-6 Next, on the upper surface of the CuI layer, the dimensions: length 30 mm x width 30 mm x by vapor deposition
A platinum electrode (second electrode) having a thickness of 0.1 mm was formed.

−7− Next, the photoelectric conversion element held between the first electrode and the second electrode 6 was optically annealed with a xenon light source. The temperature at this time is 110 ° C. and the time is 180 minutes. Made at a temperature of

(Example 2)
A wet dye-sensitized solar cell (photoelectric conversion element) was produced as follows.

-0- First, a soda glass substrate having dimensions: length 30 mm × width 35 mm × thickness 1.0 mm was prepared. Next, this soda glass substrate was cleaned by immersing it in a cleaning solution (mixed solution of sulfuric acid and hydrogen peroxide solution) at 85 ° C. to clean the surface.

-1- Next, on the upper surface of the soda glass substrate, the dimensions: length 30 mm × width 35 by vapor deposition.
An FTO electrode (first electrode) of mm × thickness 1 μm was formed.

-2- Next, a titanium oxide layer (electron transport layer) was formed in a region of 30 mm length × 30 mm width on the upper surface of the formed FTO electrode. This was done as follows.

[Preparation of titanium oxide powder]
A titanium oxide powder made of a mixture of a rutile type titanium dioxide powder and an anatase type titanium dioxide powder was prepared. The average particle diameter of the titanium oxide powder is 20 nm, and the mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder is 60 by weight.
: 40.

Furthermore, a titania nanotube was prepared separately from the titanium dioxide powder. The diameter of the titania nanotube (body) is 5 to 50 nm depending on the production conditions, and the length is 10 to 2.
00 nm.

[Preparation of sol solution (titanium oxide layer material)]
First, titanium tetraisopropoxide was dissolved in 2-propanol so as to be 1 mol / L.

Next, acetic acid (additive) and distilled water were mixed with this solution. The mixing ratio of acetic acid and titanium tetraisopropoxide is 1: 1 (molar ratio), and the mixing ratio of distilled water and titanium tetraisopropoxide is 1: 1 (molar ratio). It was made to become.

Next, the prepared titanium oxide powder or titania nanotube was mixed in the solution. Further, this suspension was diluted 2-fold with 2-propanol. As a result, the sol solution (
Titanium oxide layer material) was prepared.

In addition, content in the sol liquid at the time of using a titanium oxide powder single-piece | unit was 0.1-10 wt%.

In addition, when the titania nanotube is used alone, the content in the sol solution is 0.1 to 10 wt.
%.

Furthermore, the content in the sol solution when a mixture of titanium oxide powder and titania nanotube was used was 0.1 to 10 wt%. At this time, the mixture ratio of titanium oxide powder and titania nanotube was set to 99: 1 to 1:99.

[Formation of titanium oxide layer]
The periphery of the FTO electrode on the soda glass substrate was masked with a tape of about 5 mm, and a sol solution (titanium oxide layer material) containing titania nanotubes was applied by a squeegee printing method or the like and dried.

Thereafter, the masking tape was peeled off from the glass substrate, put into an atmospheric furnace heated to 450 ° C., and baked for about 30 minutes.

Thereby, a titanium oxide layer having a porosity of 34% was obtained. The average thickness of the titanium oxide layer was 17.2 μm.

-3- Next, the soda glass substrate, the FTO electrode, and the titanium oxide layer laminate were immersed in a saturated ethanol solution of ruthenium trisbipidyl (organic dye), then taken out from the ethanol solution, and the ethanol was removed by natural drying. Volatilized. Furthermore, 80 ° C., 0.5
After drying in a clean oven for an hour, it was left overnight. Thereby, the dye layer was adsorbed along the outer surface of the titanium oxide layer, the inside of the pores, and the inner surface of the titania nanotube.

-4-
Next, a spacer of about 30 μm is attached to the periphery of the area where the TiO ₂ layer is not formed on the FTO substrate, and further, dimensions: 30 mm long × 30 mm wide × 1.0 mm thick on the spacer.
A glass substrate was attached.

-5-
Next, an iodine solution using acetonitrile as a solvent was injected into the gap between the two glass substrates prepared above. Tetrapropylammonium iodide was added as a hole transport efficiency improving substance so as to be 1 × 10 ⁻³ wt%.

As described above, according to the present invention, in the photoelectric conversion element sandwiched between the first electrode and the second electrode 6, the electron transport layer material includes a nanotube-like (body) crystalline titania (titania). Since the specific surface area of titania nanotubes is larger than that of normally used titanium dioxide particles, the surface area of the electron transport layer 4 can be made sufficiently large. Therefore, the formation area (formation region) of the dye layer D (see later) formed along the outer surface of the electron transport layer 4 and the inner surface of the hole 41 can be sufficiently increased.

  The photoelectric conversion element of the present invention is easy to manufacture and can be manufactured at low cost.

It is a fragmentary sectional view which shows 1st Embodiment at the time of applying the photoelectric conversion element of this invention to a solar cell. It is an enlarged view which shows the cross section of the center part vicinity of the thickness direction of the solar cell of 1st Embodiment. It is the elements on larger scale which show the cross section of the electron carrying layer in which the pigment | dye layer was formed. It is a schematic diagram which shows the structure of an electron carrying layer and a pigment | dye layer. It is a schematic diagram which shows the principle of a solar cell. It is a figure which shows the equivalent circuit of the solar cell circuit shown in FIG.

Explanation of symbols

1A, 1B ... solar cell, 2 ... substrate, 3 ... first electrode, 4 ... electron transport layer, 41 ... hole, 5 ...
Hole transport layer, 51 ... convex portion, 6 ... second electrode, 7 ... spacer, 8 ... barrier layer, 11A ... laminate, 12A ... laminate, 11B ... laminate, 12B ... laminate, 100 ... external circuit , 200 ... diode, D ... dye layer.

Claims (17)

A first electrode;
A second electrode disposed opposite the first electrode;
An electron transport layer located between the first electrode and the second electrode, at least a portion of which is porous;
A dye layer in contact with the electron transport layer;
A photoelectric conversion element having a hole transport layer located between the electron transport layer and the second electrode,
The photoelectric conversion element, wherein the electron transport layer contains a substance that suppresses reverse electron transfer of electrons excited from the dye. The substance that suppresses the reverse electron transfer of the electrons is a conduction band of the electron transport layer.
2. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a substance having a conduction band lower end potential lower than the lower end potential. The substance that suppresses the reverse electron transfer of the electrons is a conduction band of the electron transport layer.
2. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a substance having a conduction band lower end potential on the valence band side of the lower end potential. 4. The photoelectric conversion element according to claim 1, wherein a surface of the electron transport layer is overcoated with a substance that suppresses reverse electron transfer of electrons excited from the dye. 5. The photoelectric conversion according to claim 1, wherein a surface of the electron transport layer is overcoated with a substance having a conduction band lower end potential lower than a conduction band lower end potential of the electron transport layer. element. An overcoat layer of a substance that suppresses reverse electron transfer of the electrons on the surface of the electron transport material,
It is 0.1-10 nanometer, The photoelectric conversion element of Claim 5 and Claim 6 characterized by the above-mentioned.   The photoelectric conversion element according to claim 1, wherein the substance that suppresses reverse electron transfer of an electron is an oxide. The photoelectric conversion element according to claim 1, wherein the substance that suppresses reverse electron transfer of electrons is a metal oxide.   The photoelectric conversion element according to claim 1, wherein the substance that suppresses reverse electron transfer of electrons is a compound. The photoelectric conversion device according to claim 1, wherein a lower end potential of a conduction band of the electron transport layer is 4.5 eV. The lower end potential of the conduction band of the substance that suppresses reverse electron transfer of the electron is 4.5.
The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a substance having a lower end potential on the valence band side of eV. The photoelectric conversion element according to claim 1, wherein the electron transport material contains at least crystal particles or tube crystals. The photoelectric conversion element according to claim 1, wherein the electron transport material is at least TiO ₂ nanoparticles or titania nanotubes. The substance that suppresses reverse electron transfer of the electrons is a valence band of the electron transport layer.
The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a substance having a valence band lower end potential higher than the lower end potential. The substance that suppresses reverse electron transfer of the electrons is a valence band of the electron transport layer.
2. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a substance having a valence band lower end potential closer to a conduction band than a lower end potential. A valence band higher than the lower end potential of the valence band of the electron transport layer.
nd) A substance having a lower end potential is overcoated on the surface of the electron transport layer.
The photoelectric conversion element of Claim 4 and Claim 15.   The photoelectric conversion device according to claim 1, which is a solar cell.

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