JP2003234485A - Photoelectric transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state dyestuff sensitizing type photoelectric transducer which can be manufactured at a low cost and excellent in photoelectric conversion efficiency. <P>SOLUTION: A solar battery 1A shown by figure 1 is a so-called dry type solar battery which does not need electrolytic solution, and provided with a first electrode 3, a second electrode 6 which is arranged to face the first electrode 3, a charge transfer layer 4 positioned between the electrodes 3 and 6, a dyestuff layer D which is in contact with the charge transfer layer 4, a hole transfer layer 5 which is positioned between the charge transfer layer 4 and the second electrode 6 and in contact with the dyestuff layer D, and a barrier layer 8. These are arranged on a substrate 2. The hole transfer layer 5 contains binder and is subjected to plasticating treatment by using heat or light. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric conversion element.

[0002]

2. Description of the Related Art Conventionally, as an environmentally friendly power source,
Solar cells (photoelectric conversion elements) using silicon have been attracting attention. Among the solar cells that use silicon, there are single-crystal silicon type solar cells that are used in artificial satellites, etc., but as practical ones, especially solar cells that use polycrystalline silicon and amorphous silicon are used. The solar cells that have been put into practical use have begun to be used for industrial and household purposes.

However, any of these solar cells using silicon has a high manufacturing cost, requires a large amount of energy for manufacturing, and is not necessarily an energy-saving power source.

Further, Japanese Patent Laid-Open No. 01-220380,
JP 05-504023 A and JP 06-511.
The dye-sensitized wet-type solar cell as disclosed in Japanese Patent No. 113 uses an electrolytic solution having a high vapor pressure, and thus has a problem that the electrolytic solution is volatilized.

In addition, in order to make up for such drawbacks,
Presentation of complete solid-state dye-sensitized solar cell (K. Tennakone,
GRRA Kumara, IRM Kottegoda, KGU Wijiayan
tha, and VPS Perera: J. Phys. D: Appl. Phys. 31
(1998) 1492).

This solar cell has a structure having an electrode in which a TiO ₂ layer is laminated and a p-type semiconductor layer provided on the TiO ₂ layer. However, such a solar cell has a drawback that the p-type semiconductor layer penetrates the TiO ₂ layer and short-circuits with the electrode.

In this presentation, CuI is used as the constituent material of the p-type semiconductor layer. The solar cell using CuI has a problem that the generated current is lowered due to deterioration due to an increase in the crystal grains of CuI.

Further, the method of applying CuI, which is a constituent material of the p-type semiconductor layer used in this presentation, is a solution in which 0.6 g of CuI is dissolved in 20 mL of acetonitrile which is a solvent (when the insoluble matter remains, the supernatant portion is removed). Solution), Ti
A method of coating on the O ₂ layer is used.

However, in this coating method, CuI
Acetonitrile vapor used as a solvent for the solution
Since the pressure is high, T formed by CuI in a nanoporous state
iO ₂The solvent acetonitril is required before it fully penetrates the layer.
Since it will volatilize, it was formed into a nanoporous state.
TiO₂CuI does not penetrate into the layer enough
O₂There was a problem that it was deposited on the upper surface of the layer.

That is, the fact that CuI does not sufficiently penetrate into the TiO ₂ layer formed in the nanoporous state means that the TiO ₂ formed in the nanoporous state has an enormous surface area.
_This means that the contact area with the _two layers cannot be sufficiently obtained and the photoelectric conversion efficiency is not improved, and the characteristics of the dye-sensitized nanoporous structure photoelectric conversion device are not fully utilized.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid-state dye-sensitized photoelectric conversion device which can be manufactured at low cost and has excellent photoelectric conversion efficiency.

[0012]

The above object is achieved by the present invention described in (1) to (16) below. (1) A first electrode, a second electrode that is installed so as to face the first electrode and has a catalyst layer on its surface, and is located between the first electrode and the second electrode. , At least a part of which is positioned in contact with a porous electron transporting layer, a dye layer in contact with the electron transporting layer, and a catalyst layer formed on the surface of the electron transporting layer and the second electrode. A photoelectric conversion element having a hole transport layer, wherein the hole transport layer contains a hole transport material and a binder. (2) The photoelectric conversion element according to (1), wherein the binder is a conductive resin. (3) The photoelectric conversion element according to (1), wherein the binder is a cyanide. (4) The photoelectric conversion device according to (3), wherein the cyanide is cyanoethylated. (5) The photoelectric conversion element according to (4), wherein the cyanoethylated product is cyanoethyl cellulose. (6) The photoelectric conversion element according to (4), wherein the cyanoethylated product is cyanoethyl hydroxyethyl cellulose. (7) The photoelectric conversion element according to (4), wherein the cyanoethylated product is cyanoethyl polyvinyl alcohol. (8) The photoelectric conversion element according to (4), wherein the cyanoethylated product is cyanoethyl sucrose. (9) The photoelectric conversion element according to (4), wherein the cyanoethylated product is cyanoethyl pullulan. (10) The photoelectric conversion element according to (3), wherein the cyanide has a nitrogen content of 9 to 15%. (11) The refractive index (n ²⁵ ) of the cyanide is 1.45.
The photoelectric conversion element according to (3), wherein the photoelectric conversion element is ˜1.55. (12) The refractive index (n ²⁵ ) of the cyanide is 1.49.
To 1.52, the photoelectric conversion element according to (3). (13) The volume resistivity (Ω-cm) of the cyanide is 5
The photoelectric conversion element according to (3), which is x10 ¹² to 1x10 ¹² (measured with a super insulation meter under conditions of direct current, measurement voltage 50 V, 25 ° C, 60% RH). (14) The true specific gravity (d ²⁵ ) of the cyanide is 1.05
The photoelectric conversion element according to (3), which has a weight ratio of 1.30 g / cc. (15) The binder is plasticized (1)
The photoelectric conversion element described in 1. (16) The photoelectric conversion element according to any one of (1) to (14), which is a solar cell.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the photoelectric conversion device of the present invention shown in the accompanying drawings will be described in detail below.

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

The solar cell 1A shown in FIG. 1 is a so-called completely solid-type dye-sensitized solar cell that does not require an electrolyte solution, and is opposed to the first electrode 3 and the first electrode 3. The installed second electrode 6, the electron transport layer 4 located between them, and the dye layer D in contact with the electron transport layer 4.
And a hole transport layer 5 located between the electron transport layer 4 and the second electrode 6 and in contact with the dye layer D, and a barrier layer 8,
These are installed on the substrate 2.

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

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 a flat member. It is composed of.

In the solar cell 1A of this embodiment, as shown in FIG. 1, from the substrate 2 and the first electrode 3 side described later,
For example, it is used by irradiating (irradiating) with light such as sunlight (hereinafter, simply referred to as “light”). Therefore, each of the substrate 2 and the first electrode 3 is preferably substantially transparent (colorless transparent, colored transparent or translucent). Thereby, the light can efficiently reach the dye layer D described later.

The constituent material of the substrate 2 is, for example,
Various glass materials, various ceramic materials, polycarbonate (PC), polyethylene terephthalate (PET)
Examples of various resin materials such as, or various metal materials such as aluminum.

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

When the substrate 2 is made of a hard material such as a glass material, its average thickness is 0.1 to 10.
It is preferably about 1.5 mm, and 0.8 to 1.2 m
It is more preferably about m.

When the substrate 2 is made of a flexible material (flexible material) such as polyethylene terephthalate (PET), its average thickness is 0.
It is preferably about 5 to 150 μm, and 10 to 75 μm
It is more preferably about m.

The substrate 2 can be omitted if necessary.

On the upper surface of the substrate 2, a layered (plate-shaped) first
Electrode 3 is installed. In other words, the first electrode 3
Is installed on the light receiving surface side of the electron transport layer 4 on which the dye layer D described later is formed so as to cover the light receiving surface.
The first electrode 3 receives the electrons generated in the dye layer D described later via the electron transport layer 4 and the barrier layer 8,
It is transmitted to the external circuit 100 connected to this.

As the 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 ), metals such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium and tantalum, or alloys containing these, or various carbons such as graphite Examples thereof include materials, and one or more of these may be used in combination.

The average thickness of the first electrode 3 is a material,
It is appropriately set depending on the application and the like, and is not particularly limited, but for example, the following can be performed.

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

When the first electrode 3 is made of the above-mentioned metals, alloys containing these, or various carbon materials, the average thickness thereof is preferably about 0.01 to 1 μm, and 0 is preferable. More preferably, it is about 0.03 to 0.1 μm.

The first electrode 3 is not limited to the one shown in the drawing, and may have a shape having a plurality of comb teeth, for example. In this case, since the light passes between the plurality of comb teeth and reaches the dye layer D, the first electrode 3 does not need to be substantially transparent. This allows
The range of selection of the constituent material of the first electrode 3 and the forming method (manufacturing method) can be expanded. Also, in this case, the first
The average thickness of the electrode 3 is not particularly limited, but is preferably about 1 to 5 μm, for example.

Further, as the first electrode 3, a comb-teeth-shaped electrode as described above and a transparent electrode made of ITO, FTO or the like can be combined (for example, laminated) and used.

A film-shaped (layered) barrier layer (short-circuit preventing means) 8 is provided on the upper surface of the first electrode 3. In addition,
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 which is 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 dioxide (TiO ₂ ) and titanium monoxide (Ti).
O), titanium oxide such as dititanium trioxide (Ti ₂ O ₃ ), n-type oxide semiconductor materials such as zinc oxide (ZnO) and tin oxide (SnO ₂ ), and other n-type semiconductor materials. Among these, one kind or a combination of two or more kinds can be used, and among these, it is preferable to use titanium oxide, particularly titanium dioxide. That is, the electron transport layer 4 is preferably composed mainly of titanium dioxide.

Titanium dioxide is particularly excellent in electron transporting ability and highly sensitive to light, so that the electron transporting layer 4 itself can generate electrons. as a result,
In the solar cell 1A, the photoelectric conversion efficiency (power generation efficiency) can be further improved.

Further, since the crystal structure of titanium dioxide is stable, the electron transport layer 4 mainly composed of titanium dioxide is used.
Then, even if it is exposed to a harsh environment, it has an advantage that it does not change (deteriorate) over time and stable performance can be continuously obtained for a long time.

Further, as titanium dioxide, those having a crystal structure mainly composed of anatase type titanium dioxide, those mainly composed of rutile type titanium dioxide, and a mixture of anatase type titanium dioxide and rutile type titanium dioxide are used. It may be one of the main ones.

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

When rutile type titanium dioxide and anatase type titanium dioxide are mixed, the mixing ratio of rutile type titanium dioxide and anatase type titanium dioxide is
Although not particularly limited, for example, 95: 5 to 5: 5 by weight ratio.
It is preferably about 95, and is 80:20 to 20:80.
It is more preferable that the degree is.

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, light passing through the barrier layer 8 (arrows in FIG. 3) is emitted by the electron transport layer 4
Of the electron transport layer 4 or is reflected in any direction in the hole 41 (diffuse reflection, diffusion, etc.). At this time, the light comes into contact with the dye layer D, and electrons and holes can be generated in the dye layer D with high frequency.

The porosity of the electron transport layer 4 is not particularly limited, but is preferably about 5 to 90%, more preferably about 15 to 50%, and more preferably 2
It is more preferably about 0 to 40%.

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 made sufficiently large. 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. Therefore, in the dye layer D, sufficient electrons can be generated and the 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.

The electron transport layer 4 may have a relatively large thickness, but a film-shaped one is preferable.
This is advantageous because the solar cell 1A can be made thinner (smaller) and the manufacturing cost can be reduced.

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

The electron transport layer 4 is formed in such a manner that the dye layer D is brought into contact with the dye by, for example, adsorbing, 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 pigment constituting the pigment layer D is not particularly limited, but examples thereof include pigments and dyes,
These can be used alone or in combination,
It is preferable to use a pigment from the viewpoint of less deterioration and deterioration with time, and a dye from the viewpoint of more excellent adsorptivity 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,
Azo series such as disazo yellow, condensed azo yellow, benzimidazolone yellow, dinitroaniline orange, benzimidazolone orange, toluidine red, permanent carmine, permanent red, naphthol red, condensed azo red, benzimidazolone carmine, benzimidazolone brown Pigments, anthrapyrimidine yellow, anthraquinone pigments such as anthraquinonyl red, azomethine pigments such as copper azomethine yellow,
Quinophthalone pigments such as quinophthalone yellow, isoindoline pigments such as isoindoline yellow, nitroso pigments such as nickel dioxime yellow, perinone pigments such as perinone orange, quinacridone magenta, quinacridone maroon, quinacridone scarlet, quinacridone red, etc. Quinacridone pigments, perylene red, perylene pigments such as perylene maroon, pyrrolopyrrole pigments such as diketopyrrolopyrrole red, organic pigments such as dioxazine pigments such as dioxazine violet, carbon black, lamp black, furnace black, Carbon pigments such as ivory black, graphite and fullerene, chromate pigments such as yellow lead, molybdate orange, cadmium yellow, cadmium lithopone yellow and cadmium Sulfide, cadmium lithopone orange, silver vermillion, cadmium red, cadmium lithopone red, sulfide pigments such as sulfur, ocher, titanium yellow, titanium barium nickel yellow, red iron oxide, amber, amber iron oxide, zinc iron chrome brown , Chrome oxide, cobalt green, cobalt chrome green, titanium cobalt green, cobalt blue, cerulean blue, cobalt aluminum chrome blue, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, etc. Pigments, hydroxide pigments such as Viridian,
Examples include ferrocyanide pigments such as dark blue, silicate pigments such as ultramarine blue, phosphate pigments such as cobalt violet and mineral violet, and inorganic pigments such as cadmium sulfide and cadmium selenide. The
These can be used alone or in combination of two or more.

[0049] As the dye is not particularly limited, for _{example, RuL 2 (SCN) 2,} RuL 2 Cl 2, RuL 2 CN 2, Rutenium
535-bisTBA (manufactured by Solaronics), a metal complex dye such as [RuL ₂ (NCS ₂ ] ₂ H ₂ O, a cyan dye, a xanthene dye,
Azo dye, hibiscus dye, blackberry dye,
Raspberry pigments, pomegranate juice pigments, chlorophyll pigments and the like can be mentioned, and one kind or a combination of two or more kinds thereof can be used. L in the above composition formula
Represents 2,2'-bipyridine or a derivative thereof.

On the upper surface of the electron transport layer 4 on which the dye layer D is formed, a layered (plate-shaped) hole transport layer 5 is provided. In other words, the hole transport layer 5 is provided so as to face the first electrode 3 with the electron transport layer 4 having the dye layer D formed therebetween. 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 the second electrode 6 described later, or the hole transport layer 5 itself serves as an electrode.

The average thickness of the hole transport layer 5 is not particularly limited, but is preferably about 1 to 500 μm, more preferably about 10 to 300 μm, and more preferably about 10 to 30 μm. Is more preferable.

As the constituent material of the hole transport layer 5, for example, substances having various ion-conducting properties, triphenyldiamine (monomers, polymers, etc.), polyaniline, polypyrrole, polythiophene, phthalocyanine compounds (eg copper phthalocyanine), or these Examples thereof include various p-type semiconductor materials such as derivatives of Al, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum, and alloys containing these. One kind or a combination of two or more kinds can be used, and in particular, a substance having ionic conductivity is preferably used. That is, the hole transport layer 5 is preferably composed mainly of a substance having ionic conductivity. Thereby, the hole transport layer 5 is
The holes generated in the dye layer D can be transported more efficiently.

Examples of the substance having the ionic conductivity include metal iodide compounds such as CuI and AgI, metal halide compounds such as metal bromide compounds such as AgBr, and metal thiocyanate such as CuSCN. Examples thereof include salts (metal rhodanide compounds) and the like, and these can be used alone or in combination of two or more.

Among these, metal halide compounds such as metal iodide compounds and metal bromide compounds are preferable as the substance having ionic conductivity. The metal halide compound is particularly excellent in ionic conductivity.

Further, it is particularly preferable to use one kind or a combination of two or more kinds of metal iodide compounds such as CuI and AgI as the substance having the ion conductive property. The metal iodide compound has extremely excellent ionic conductivity. Therefore, by using the metal iodide compound as the main material of the hole transport layer 5, the solar cell 1
The photoelectric conversion efficiency (energy conversion efficiency) of A can be further improved.

As shown in FIG. 2, the hole transport layer 5 is formed so as to enter the holes 41 of the electron transport layer 4 in which the dye layer D 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 more efficiently transferred to the hole transport layer 5. 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) shape is formed.
Second electrode 6 is installed.

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

Further, as the constituent material of the second electrode 6,
For example, aluminum, nickel, cobalt, platinum,
Examples thereof include metals such as silver, gold, copper, molybdenum, titanium, and tantalum, alloys containing these, and various carbon materials such as graphite. One or two of these are included.
A combination of two or more species can be used.

The second electrode 6 can be omitted if necessary.

In such a solar cell 1A, as shown in FIG. 5, when light is incident, electrons are excited mainly in the dye layer D, and electrons (e ⁻ ) and holes (h ⁺ ) are generated. To do.
Among these, the electrons move to the electron transport layer 4 and the 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 in the external circuit 100.

The value of Vaccum Energy shown in FIG.
This is an example in which the electron transport layer 4 and the barrier layer 8 are 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 circulating circuit having a diode 200 as shown in FIG. 6 is formed.

By the irradiation of light (reception of light), the dye layer D
In the following, electrons and holes are generated at the same time, but in the following description, it is described as “electrons are generated” for convenience.

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

The short-circuit preventing means will be described in detail below.

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

When manufacturing the solar cell 1A, as 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, if the porosity of the electron transport layer 4 is increased in the solar cell in which the barrier layer 8 is not provided, the hole transport layer material becomes the pores of the electron transport layer 4 in which the dye layer D is formed. It may penetrate into the inside 41 and reach the first electrode 3. That is, in the solar cell having no barrier layer 8, the leakage current increases due to the contact (short circuit) between the first electrode 3 and the hole transport layer 5, and the power generation efficiency (photoelectric conversion efficiency) is increased. May be reduced.

On the other hand, in the solar cell 1A provided with the barrier layer 8, the inconvenience as described above is prevented, and the decrease in power generation efficiency is suitably prevented or suppressed.

When the porosity of the barrier layer 8 is A [%] and the porosity of the electron transport layer 4 is B [%], B /
A is, for example, preferably about 1.1 or more, 5
It is more preferably about 10 or more, and even more preferably about 10 or more. Thereby, the barrier layer 8 and the electron transport layer 4 can exhibit their respective functions more suitably.

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

Further, the thickness ratio of the barrier layer 8 and the electron transport layer 4 is not particularly limited, but is, for example, 1:99 to.
It is preferably about 60:40 and 10:90 to 4
It is more preferably about 0:60. In other words, the ratio of the thickness of the barrier layer 8 to the whole of the barrier layer 8 and the electron transport layer 4 is preferably about 1 to 60%, more preferably about 10 to 40%. Accordingly, 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 at the same time, 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, preferably about 0.01 to 10 μm, more preferably about 0.1 to 5 μm, More preferably, it is about 0.5 to 2 μm. Thereby, the effect can be further improved.

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 , Zn.
Various metal oxides such as O, SiO ₂ , Al ₂ O ₃ and SnO ₂ , CdS, CdSe, TiC, Si ₃ N ₄ , SiC, B
It is possible to use one kind or a combination of two or more kinds of various metal compounds such as ₄ N and BN, and among them, those having electric conductivity equivalent to that of the electron transport layer 4 are preferable, and particularly, Those mainly containing titanium oxide are more preferable. By forming the barrier layer 8 with such a material, the electrons generated in the dye layer D can be more efficiently transferred from the electron transport layer 4 to the barrier layer 8, and 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 entire barrier layer 8 and the electron transport layer 4, that is, the barrier value. The resistance value in the thickness direction of the laminate of the layer 8 and the electron transport layer 4 is preferably about 100 Ω / cm ² or more, more preferably about 1 kΩ / cm ² or more. Thereby, it is possible to more reliably prevent or suppress a leak (short circuit) between the first electrode 3 and the hole transport layer 5, and it is possible to prevent a decrease in power generation efficiency of the solar cell 1A. There is.

The interface between the barrier layer 8 and the electron transport layer 4 may or may not be clear, but is preferably 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. This makes it possible to transfer electrons more reliably (efficiently) between the barrier layer 8 and the electron transport layer 4.

Further, the barrier layer 8 and the electron transport layer 4 are
A structure in which materials having the same composition (for example, a material mainly containing titanium dioxide) is used, and only the porosities thereof are different, that is, a part of the electron transport layer 4 is part of the barrier layer 8 is formed.
May be configured to function as.

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,
It can also be formed at any position in the thickness direction.

Further, in this case, the electron transport layer 4 has a structure having a portion sandwiching a rough portion between dense portions, a structure having a portion sandwiching a dense portion between rough portions, and the like. It may be.

In such a solar cell 1A, the dye layer D
The photoelectric conversion efficiency when the incident angle of light on 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 5
When the photoelectric conversion efficiency at 2 ° is R ₅₂ , it is preferable that R ₅₂ / R ₉₀ has a property of about 0.8 or more, and more preferably about 0.85 or more. . Satisfying such a condition means that the electron transport layer 4 on which the dye layer D is formed has a low directivity to light, that is,
It is isotropic. Therefore, such a solar cell 1A can generate power more efficiently over almost the entire sunshine duration of the sun.

Further, in the solar cell 1A, the first electrode 3
Is positive and the second electrode 6 (hole transport layer 5) is negative, and when a voltage of 0.5 V is applied, its resistance value is
For example, it preferably has a characteristic of about 100 Ω / cm 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. It is a thing. 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, for example, as follows.

First, the substrate 2 made of soda glass or the like is prepared. As the substrate 2, a substrate having a uniform thickness and no bending is preferably used.

<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 the material of the first electrode 3 composed of, for example, FTO or the like by using, for example, a vapor deposition method, a sputtering method, a printing method or the like.

<2> Next, the barrier layer 8 is formed on the first electrode 3
Formed on the upper surface of.

The barrier layer 8 is 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, it is preferable to form the sol-gel method.

This sol-gel method is extremely easy to operate. For example, by using it in combination with various coating methods such as dipping, dropping, doctor blade, spin coating, brush coating, spray coating, and roll coater, The barrier layer 8 can be preferably formed in a film shape (thick film and thin film) without requiring a large-scale device.

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

The sol-gel method does not allow (prevent) a reaction (for example, hydrolysis, polycondensation, etc.) of a titanium compound (organic or inorganic) described later in the barrier layer material (hereinafter referred to as " MOD (Metal Organic Deposition
Or "Metal Organic Decomposition) method". ), Or a method which allows this, 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 (reproducible) and dense. (Porosity within the above range).

In particular, titanium tetraisopropoxide (T
PT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, and the like, using an organic titanium compound such as titanium alkoxide (metal alkoxide) which is chemically extremely unstable (easy to decompose)
When forming an iO ₂ layer (barrier layer 8 of the present invention),
This MOD method is optimal.

The method of forming the barrier layer 8 by the MOD method will be described below.

[Preparation of Barrier Layer Material] For example, among organic titanium compounds such as titanium alkoxide (metal alkoxide) such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide and titanium tetrabutoxide. In the case of using one kind or a combination of two or more kinds, first, this organic titanium compound (or this solution) is treated with, for example, anhydrous ethanol,
It is dissolved in an organic solvent (or a mixed solvent thereof) such as 2-butanol, 2-propanol, and 2-n-butoxyethanol.

Thereby, the concentration (content) of the organic titanium compound in the solution is adjusted (for example, 0.1 to 10 mol).
/ L) to adjust the viscosity of the resulting barrier layer material. The viscosity of the barrier layer material is appropriately set depending on the type of the coating method and the like, and is not particularly limited, but when spin coating is used, it is preferably high viscosity (for example, about 0.5 to 20 cP (normal temperature)). When a spray coat is used, it is preferable that the viscosity is low (for example, 0.1
Approximately 2 cP (normal temperature)).

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

By adding these additives, these additives substitute for the alkoxide (alkoxyl group) which coordinates with the titanium atom in the titanium alkoxide and coordinate with the titanium atom. This suppresses the hydrolysis of the titanium alkoxide and stabilizes it. That is, these additives function as a hydrolysis inhibitor that suppresses the hydrolysis of the titanium alkoxide. in this case,
The compounding ratio of this additive to the titanium alkoxide is not particularly limited, but for example, it is preferable that the molar ratio is about 1: 2 to 8: 1.

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

The same applies to combinations in other cases.

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

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

Further, when an organic titanium compound such as titanium oxyacetylacetonate (TOA) is used,
Since this organic titanium compound (or this solution) is stable alone, a stable barrier layer material can be obtained by dissolving it in the organic solvent.

In the present invention, when the barrier layer 8 is formed by the MOD method, among the above-mentioned three solutions,
It is optimum to use a solution prepared by the following method. That is, titanium tetraisopropoxide (TP
T), an organic titanium compound such as titanium tetramethoxide, titanium tetraethoxide, titanium alkoxide such as titanium tetrabutoxide (or a solution thereof) is dissolved (or diluted) with a solvent, and titanium tetrachloride and acetic acid are added to the solution. It is optimum to use a solution prepared by a method of adding additives such as acetylacetone, triethanolamine, diethanolamine and the like. According to this method, it is possible to obtain a compound that is stabilized when titanium dioxide is produced by coordinating the additive with the titanium atom of the titanium alkoxide.

As a result, the 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 containing titanium dioxide as a main material.

[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 rotation speed is 500 to 4000 rpm.
It is preferably carried out to the extent.

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

Such heat treatment can be carried out, for example, in air or nitrogen gas, or in addition to various inert gases,
Vacuum or reduced pressure (for example, 1 × 10 ⁻¹ to 1 × 10 ⁻⁶ To)
It may be performed in a non-oxidizing atmosphere such as rr).

The coating of the barrier layer material on the upper surface of the first electrode 3 may be performed while heating the first electrode 3.

Further, the coating film is heat-treated at a temperature higher than the above heat treatment. As a result, the organic component remaining in the coating film is removed, and titanium dioxide (TiO ₂ ) is sintered to form the barrier layer 8 made of titanium dioxide having an amorphous or anatase type crystal structure. The heat treatment conditions are 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.

The atmosphere of such heat treatment may be the same as that of the heat treatment.

The above-mentioned operations are preferably carried out for 1 to 20
The barrier layer 8 having an average thickness as described above is formed about once, more preferably about 1 to 10 times.

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

Prior to the formation of the barrier layer 8, the first
The upper surface of the electrode 3 of, for example, O ₂ plasma treatment, EB
The organic substance attached to the upper surface of the first electrode 3 may be removed by performing a treatment, a cleaning treatment with an organic solvent (for example, ethanol, acetone, or the like). in this case,
A mask layer is formed on the upper surface of the first electrode 3 and masked in advance, leaving a portion for forming the barrier layer 8. Further, 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 is formed, for example, by the sol-gel method,
It can be formed by a vapor deposition method, a sputtering method, or the like, and among these, the sol-gel method is preferable.

This sol-gel method is extremely easy to operate. For example, by using it in combination with various coating methods such as dipping, dropping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc., The electron transport layer 4 is preferably used without requiring a large-scale device.
Can be formed into a film (thick film and thin film).

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

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

The average particle size of the powder of the electron transport layer material is not particularly limited, but is preferably about 1 nm to 1 μm, and more preferably about 5 to 50 nm. By setting the average particle size of the powder of the electron transport layer material within the above range, it is possible to improve the uniformity of the powder of the electron transport layer material in the sol liquid. Further, since the surface area (specific surface area) of the obtained electron transport layer 4 can be increased by reducing the average particle size of the powder of the electron transport layer material in this way, the formation region (formation of the dye layer D) Area) can be made larger, and solar cell 1
It contributes to the improvement of power generation efficiency of A.

An example of the method of forming the electron transport layer 4 will be described below.

[Preparation of Titanium Oxide Powder (Powder for Electron Transport Layer Material)] <3-A0> A rutile type titanium dioxide powder and an anatase type titanium dioxide powder are mixed at a predetermined mixing ratio (only anatase type titanium dioxide powder is used). , And rutile type titanium dioxide powder alone).

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

The average particle size of the titanium oxide powder as a whole is within the above range.

[Preparation of Sol Solution (Electron Transport Layer Material)] <3-A1> First, for example, titanium such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide and titanium tetrabutoxide. Organic titanium compounds such as alkoxide and titanium oxyacetylacetonate (TOA), and titanium tetrachloride (T
TC) and the like, one or a combination of two or more of inorganic titanium compounds, for example, anhydrous ethanol, 2-
It is dissolved in an organic solvent (or a mixed solvent thereof) such as butanol, 2-propanol and 2-n-butoxyethanol.

At this time, the concentration (content) of the titanium compound (organic or inorganic) in the solution is not particularly limited, but is preferably about 0.1 to 3 mol / L.

Next, if necessary, various additives are added to this solution. When titanium alkoxide, for example, is used as the organic titanium compound, titanium alkoxide has low chemical stability, and therefore, additives such as acetic acid, acetylacetone and nitric acid are added. Thereby, the titanium alkoxide can be made into a chemically stable compound. In this case, the compounding ratio of this additive and the titanium alkoxide is not particularly limited, but, for example,
The molar ratio is preferably about 1: 2 to 8: 1.

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

<3-A3> Then, the titanium oxide powder prepared in the step <3-A0> is mixed with the solution to obtain a suspension (dispersion) liquid.

<3-A4> Further, this suspension is diluted with the above-mentioned organic solvent (or mixed solvent). This prepares a sol liquid. The dilution ratio is preferably about 1.2 to 3.5 times, for example.

The content of titanium oxide powder (electron transport layer material powder) in the sol liquid is not particularly limited, but is preferably about 0.1 to 10 wt% (wt%), More preferably, it is about 0.5 to 5 wt%. Thereby, the porosity of the electron transport layer 4 can be preferably set within the above range.

[Formation of Electron Transport Layer (Titanium Oxide Layer) 4] <3-A5> While the barrier layer 8 is preferably heated, a coating method (for example, dropping) is applied on the upper surface of the barrier layer 8.
The sol solution is applied to obtain a film-like body (coating film). The heating temperature is not particularly limited, but is, for example, 80 to 180.
The temperature is preferably about 0 ° C, more preferably about 100 to 160 ° C.

The above operation is preferably carried out in the range of 1 to 10
The electron transport layer 4 having the above-mentioned average thickness is formed about once, more preferably about 5 to 7 times.

Then, the electron transport layer 4 may be subjected to a heat treatment (for example, firing) at a temperature of about 250 to 500 ° C. for about 0.5 to 3 hours, if necessary.

<3-A6> The electron transport layer 4 obtained in the step <3-A5> can be subjected to a post-treatment, if necessary.

As the post-processing, for example, mechanical processing (post-processing) such as grinding and polishing for adjusting the shape.
Other examples include post-treatment such as cleaning and chemical treatment.

The electron transport layer 4 can also be formed as follows, for example. Hereinafter, another method of forming the electron transport layer 4 will be described. In the following explanation,
The description will focus on the differences from the above-described forming method, and the description of the same items will be omitted.

[Preparation of Titanium Oxide Powder (Powder for Electron Transport Layer Material)] <3-B0> The same step as the above step <3-A0> is performed.

[Preparation of coating liquid (electron transport layer material)] <3-B1> First, the titanium oxide powder prepared in the above step is mixed with an appropriate amount of water (for example, distilled water, ultrapure water, ion-exchanged water, RO). Suspended in water).

<3-B2> Next, a stabilizer such as nitric acid is added to the suspension and sufficiently kneaded in an agate (or alumina) mortar.

<3-B3> Then, in the suspension,
The above water is added and the mixture is further kneaded. At this time, the compounding ratio of the stabilizer and water is preferably 10:90 by volume.
~ 40: 60, more preferably 15: 85-30:
The viscosity of the suspension is, for example, 0.2 to
It is about 30 cP (normal temperature).

<3-B4> Then, in the suspension,
For example, a surfactant is added and kneaded so that the final concentration is about 0.01 to 5 wt%. Thus, the coating liquid (electron transport layer material) is prepared.

As the surface active agent, cationic,
It may be anionic, zwitterionic or nonionic, but nonionic ones are preferably used.

Further, as the stabilizer, instead of nitric acid,
It is also possible to use a titanium oxide surface modification reagent such as acetic acid or acetylacetone.

In the coating liquid (electron transport layer material),
If necessary, various additives such as a binder such as polyethylene glycol, a plasticizer and an antioxidant may be added.

[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. Form the body (coating). Alternatively, the coating and drying operations may be performed a plurality of times to stack the layers. This allows
The electron transport layer 4 is obtained.

Next, if necessary, the electron transport layer 4 may be subjected to heat treatment (eg, firing) at a temperature of about 250 to 500 ° C. for about 0.5 to 3 hours. As a result, the titanium oxide powders that have just stopped contacting each other are diffused at the contact portions, and the titanium oxide powders are fixed (fixed) to some extent. In this state, the electron transport layer 4 becomes porous.

<3-B6> The same step as 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 the liquid containing the dye as described above (for example, a solution in which the dye is dissolved in a solvent, a suspension in which the dye is suspended in the solvent) are immersed, for example. , Dyes D are formed on the outer surface of the electron transport layer 4 and the inner surfaces of the holes 41 by, for example, adsorbing, bonding, and the like.

More specifically, the substrate 2, the first electrode 3,
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 by immersing the laminate of the barrier layer 8 and the electron transport layer 4 in the liquid containing the dye.

The solvent (liquid) for dissolving or suspending (dispersing) the dye is not particularly limited, but examples thereof include various types of 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.

Then, the laminate is treated with the solution (suspension).
From the inside, 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.

If necessary, this laminate may be dried in a clean oven or the like at a temperature of about 60 to 100 ° C. for about 0.5 to 2 hours. Thereby, the dye can be more strongly adsorbed (bonded) to the electron transport layer 4.

<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).

For the hole transport layer 5, for example, a hole transport layer material (electrode material) containing a substance having ionic conductivity such as CuI is provided on the upper surface of the electron transport layer 4 on which the dye layer D is formed.
For example, it is preferably formed by coating by various coating methods such as dipping, dropping, doctor blade, spin coating, brush coating, spray coating and roll coater.

According to such a coating method, the hole transport layer 5
Can be more surely permeated into the holes 41 of the electron transport layer 4 in which the dye layer D is formed.

After the coating film is formed, the coating film may be subjected to heat treatment, but the dye layer D of the hole transport layer material may be used.
Coating on the upper surface of the electron transport layer 4 on which the
It is preferable to perform it while heating (the electron transport layer 4 on which the dye layer D is formed). As a result, the hole transport layer 5 can be more quickly formed.
Is advantageous in shortening the manufacturing time of the solar cell 1A.

The heating temperature is preferably 5
It is set to about 0 to 150 ° C. When the heat treatment is performed after forming the coating film, the coating film may be dried before the heat treatment.

The above operation may be repeated a plurality of times.

More specifically, the substrate 2, the first electrode 3, the barrier layer 8 are placed on a hot plate heated to about 80 ° C.
And the laminated body of the electron transport layer 4 on which the dye layer D is formed is installed, 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 repeated a plurality of times to form the hole transport layer 5 having the above-mentioned average thickness.

The solvent used for the hole transport layer material is not particularly limited, but for example, an organic solvent such as acetonitrile, ethanol, methanol, isopropyl alcohol, etc., or one kind or a combination of two or more kinds such as various kinds of water is used. be able to.

Acetonitrile is preferably used as a solvent for dissolving a substance having ionic conductivity.

At this time, in the present invention, the solution of the hole transport layer material is a low-concentration CuI solution prepared by dissolving 200 to 1 mg of the hole transport material in 10 mL of the solvent.

More preferably, as the solution of the hole transport layer material, a low concentration CuI solution prepared by dissolving 100 to 10 mg of the hole transport material in 10 mL of the solvent is used.

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

More preferably, acetonitrile 10 m
A low-concentration CuI solution having CuI dissolved in a weight ratio of 1.5 to 0.1% with respect to L (7.8 g) is used.

More specifically, 10 mL of acetonitrile
(7.8g), 100mg (weight ratio 1.28)
%) CuI is used to dissolve CuI in a low concentration.

This coating method is based on this low concentration CuI.
The solution is permeated onto the dye layer in 2 to 100 times and applied, and the low-concentration CuI solution is applied at intervals of low-concentration Cu.
After the solvent of the solution I is volatilized or immediately before volatilization, the solution is continuously applied.

[0171] Thus, in the present invention, because of the use of low concentrations of CuI solution, it is possible to reduce the amount of CuI in a single coating step, the upper surface of CuI is TiO ² layer by evaporation of acetonitrile It is possible to solve the problem of depositing on the surface.

Further, as in the present invention, a low-concentration CuI solution is continuously applied a plurality of times (about 2 to 100 times) so that the solvent, acetonitrile, can re-extract 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 that is dissolved and formed into a nanoporous state.

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

Further, in the present invention, a cyanoethyl compound such as cyanoresin may be added as a binder to the acetonitrile solution of the substance having ionic conductivity. In this case, the cyanoethylated compound is added to the substance having the ionic conductivity in a mass ratio (weight ratio) of 5
It is preferable to mix (blend) at 0.5 wt%.

As an example of the cyanoethylated product, cyanoethyl cellulose, cyanoethyl hydroxyethyl cellulose, cyanoethyl polyvinyl alcohol, cyanoethyl sucrose, cyanoethyl pullulan and the like can be used.

The nitrogen content of the cyanoethylated product is 9 to
15% is desirable, and the refractive index (n ²⁵ ) is 1.
45 to 1.55, and more preferable refractive index (n ²⁵ ).
Is more preferably 1.49 to 1.52.

Volume specific resistance of the cyanoethylated compound (Ω
-cm) is preferably 5 × 10 ¹² to 1 × 10 ¹² (measured with a super-insulator under conditions of direct current, measurement voltage 50 V, 25 ° C., 60% RH), and the true specific gravity of the cyanoethylated product ( d ²⁵ ) is preferably 1.05 to 1.30 g / cc.

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

The hole transport efficiency improving substance is not particularly limited, but examples thereof include halides such as ammonium halides, and particularly ammonium halides such as tetrapropylammonium iodide (TPAI) are preferably used. . As a substance that improves hole transport efficiency,
By using an ammonium halide, especially tetrapropylammonium iodide, the hole transport layer 5
The carrier mobility is further increased by further improving the ion conduction characteristics. As a result, the hole transport layer 5
Further improves its electrical conductivity.

The content of the hole transport efficiency improving substance in the hole transport layer material is not particularly limited, but is 1 × 10 ⁻⁴ to 1
It is preferable that it is about × 10 ⁻¹ wt% (weight%).
More preferably, it is in the range of x10 ^-4 to 1 x 10 ^-2 wt%. Within such a numerical range, the above-mentioned effect becomes more remarkable.

When the hole transport layer 5 is composed mainly of a substance having ion conduction characteristics, the hole transport layer material is formed by crystallizing a substance having ion conduction characteristics when crystallized. It is preferable to contain a crystal size coarsening suppressing substance that suppresses an increase in size.

As the crystal size coarsening suppressing substance,
Although not particularly limited, examples thereof include thiocyanate (rhodanide) and the like in addition to the above-mentioned cyanoethylated compound, hole transport efficiency improving substance. Further, the crystal size coarsening suppressing substance may be used alone or in combination of two or more.

As the thiocyanate, for example,
Sodium thiocyanate (NaSCN), potassium thiocyanate (KSCN), copper thiocyanate (CuSC
N), ammonium thiocyanate (NH ₄ SCN) and the like.

As the crystal size coarsening suppressing substance,
When a hole transport efficiency improving substance is used, ammonium halide is suitable. Among the hole transport efficiency improving substances, ammonium halide is particularly excellent in the function of suppressing the increase in the crystal size of the substance having the ion conductive property.

Here, if the hole transport layer material does not contain this crystal size coarsening suppressing substance, depending on the type of substance having ion conduction characteristics, the above-mentioned heating temperature, etc.
When a substance having ion-conducting properties is crystallized, the crystal size may become too large, and the volume expansion of the crystal may proceed excessively. In particular, when such crystallization occurs in the holes (small holes) of the barrier layer 8, cracks are generated in the barrier layer 8 and, as a result, between the hole transport layer 5 and the first electrode 3,
A short circuit may occur partially due to contact or the like.

When the crystal size of the substance having the ionic conduction property becomes large, the electron transport layer 4 in which the dye layer D is formed may be formed depending on the kind of the substance having the ionic conduction property.
There is a case where the contact property with is lowered. As a result, the substance having the ionic conductivity, that is, the hole transport layer 5 may be separated from the electron transport layer 4 on which the dye layer D is formed.

Therefore, such a solar cell may deteriorate in device characteristics such as photoelectric conversion efficiency.

On the other hand, when the hole transport layer material contains the crystal size coarsening suppressing substance, the substance having ionic conductivity is suppressed from increasing in crystal size, and the crystal size is extremely small or comparative. It will be small.

For example, when thiocyanate is added to a CuI acetonitrile solution, thiocyanate ions (SCN ⁻ ) are adsorbed around Cu atoms of CuI dissolved in a saturated state, and Cu—S ( Sulfur)
Bonding occurs. As a result, C dissolved in a saturated state
The binding between uI molecules is significantly inhibited, resulting in C
Since it is possible to prevent the crystal growth of uI, it is possible to obtain a CuI crystal grown finely.

From the above, the solar cell 1A can preferably suppress the inconvenience caused by the coarsening of the crystal size of the substance having the ion conduction characteristic as described above.

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

Further, the hole transport layer 5 is formed of the p-type as described above.
In the case of using a p-type semiconductor material, the p-type semiconductor material may be, for example, acetone or isopropyl alcohol (IP
A) A hole transport layer material is prepared by dissolving (or suspending) it in various organic solvents (or mixed solvents containing these) such as ethanol. 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 can be formed by using, for example, the material of the second electrode 6 made of platinum or the like, for example, by the vapor deposition method, the sputtering method, the printing method or the like.

<7> Next, the photoelectric conversion element sandwiched by the first electrode and the second electrode 6 is plasticized by heat or light.

This treatment is a treatment for more firmly associating the hole transporting layer made of CuI with the TiO ₂ layer having the plastic binder (conductive resin) and the dye adsorbed thereon, and further for making it conform.

That is, by plasticizing the plastic binder (conductive resin) contained in the hole transport layer made of CuI or the like, the hole transport layer is sufficiently permeated into the TiO ₂ layer formed in the nanoporous state, Make them adhere closely.

The viscosity (20 ° C.) of the plastic binder (conductive resin) used at this time is 150 to 7000 cP, and the appearance is granular or mucus, and more preferably the plastic binder ( The viscosity (20 ° C.) of the conductive resin is particularly preferably 240 to 1200 cP.

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. It is particularly suitable.

The softening temperature of the plastic binder (conductive resin) must be a temperature at which the dye adsorbed by the heat of plasticizing the binder is not destroyed.

Next, the method of plasticizing the plastic binder (conductive resin) contained in the hole transport layer made of CuI or the like will be specifically described.

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

The second plasticizing treatment is photoplasticizing treatment. This photo-plasticizing treatment is carried out with a halogen or xenon light source, and is continued at a temperature of 25 to 250 ° C. for a time of about 5 to 300 minutes.

The solar cell 1A is manufactured through the above steps.

Although the photoelectric conversion element of the present invention has been described based on the illustrated embodiments, the present invention is not limited to these. Each part constituting the photoelectric conversion element,
It can be replaced with an arbitrary one having 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 is applicable not only to solar cells but also to various elements (light receiving elements) such as optical sensors and optical switches that receive light and convert it into electric energy. Is something that can be done.

Further, in the photoelectric conversion device of the present invention, the incident direction of light may be from the opposite direction, unlike the one shown in the drawing. That is, the incident direction of light is arbitrary.

[0209]

EXAMPLES 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, the dimensions: length 30 mm x width 35
A soda glass substrate having a size of mm × thickness of 1.0 mm was prepared.
Next, this soda glass substrate was immersed in a cleaning liquid (mixed liquid of sulfuric acid and hydrogen peroxide solution) at 85 ° C. for cleaning to clean the surface.

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

-2- Next, a barrier layer was formed in a region of 30 mm in length × 30 mm in 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 added to 2-n-
It was dissolved in butoxyethanol to a concentration of 0.5 mol / L.

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

Thus, a barrier layer material was obtained. In addition,
The barrier layer material had a viscosity of 3 cP (normal temperature).

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

Next, 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 60 ° C. for 10 minutes.

Further, the laminated body was heated at 480 ° C. for 30 minutes.
The organic components remaining in the coating film were removed by applying a heat treatment in the oven for 1 minute.

This operation was repeated 10 times so that the layers were laminated.

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

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

[Preparation of Titanium Oxide Powder] Titanium oxide powder composed of a mixture of rutile type titanium dioxide powder and anatase type titanium dioxide powder was prepared. The average particle size of the titanium oxide powder was 40 nm, and the compounding ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder was 60:40 by weight.

[Preparation of Sol Solution (Titanium Oxide Layer Material)] First, titanium tetraisopropoxide was dissolved in 2-propanol to a concentration of 1 mol / L.

Next, acetic acid (additive) was added to this solution,
Mix with distilled water. 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). So that

Next, the prepared titanium oxide powder was mixed with this solution. Further, this suspension was diluted 2-fold with 2-propanol. Thus, a sol liquid (titanium oxide layer material) was prepared.

The content of titanium oxide powder in the sol solution was set to 3 wt%.

[Formation of Titanium Oxide Layer] A laminated body of a soda glass substrate, an FTO electrode and a barrier layer was placed on a hot plate heated to 140 ° C., and a sol solution (titanium oxide layer material) was placed on the upper surface of the barrier layer. Is dropped (application method),
Dried. This operation was repeated 7 times so that the layers were laminated.

As a result, a titanium oxide layer having a porosity of 34% was obtained. The average thickness of this titanium oxide layer was 7.
It was 2 μm.

The resistance value in the thickness direction of the entire barrier layer and titanium oxide layer was 1 kΩ / cm ² or more.

-4- Next, soda glass substrate, FT
The laminated body of the O electrode, the barrier layer and the titanium oxide layer was immersed in a saturated ethanol solution of ruthenium trisbipidyl (organic dye), and then taken out from the ethanol solution.
Ethanol was volatilized by natural drying. Furthermore, 80
After drying in a clean oven at 0 ° C. for 0.5 hours, it was left overnight. As a result, a dye layer was formed along the outer surface of the titanium oxide layer and the inner surface of the holes.

-5-Next, soda glass substrate, FT
The laminate of the titanium oxide layer on which the O electrode, the barrier layer, and the dye layer D were formed was placed on a hot plate heated to 80 ° C., and 100 mg of CuI was dissolved in 10 mL of an acetonitrile solution (hole transport layer material). Dye layer D
It was dropped on the upper surface of the titanium oxide layer on which was formed and dried.

This operation was repeated about 2 to 100 times so that the CuI solution formed into a nanoporous state TiO ₂
A CuI layer (hole transport layer) having dimensions of 30 mm in length × 30 mm in width × 30 μm in thickness was formed so as to sufficiently penetrate the layer.

Tetrapropylammonium iodide was added to the acetonitrile solution as a substance for improving the hole transport efficiency so as to be 1 × 10 ³ wt%.

In addition, CuI was added to the acetonitrile solution.
As a binder of, cyanoresin (cyanoethylated product) was added. In addition, CuI and cyanoresin were mixed in a mass ratio (weight ratio) of 97: 3.

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

-6- Then, on the upper surface of the CuI layer, dimensions: 30 mm in length × 30 mm in width × 0.1 in thickness by vapor deposition.
mm platinum electrode (second electrode) was formed.

-7- Then, the photoelectric conversion element sandwiched between the first electrode and the second electrode 6 was photo-annealed with a xenon light source. At this time, the temperature is 110 ° C. and the time is 180 minutes. Made at the temperature of.

[0239]

As described above, according to the present invention, in the photoelectric conversion element sandwiched by the first electrode and the second electrode 6, the hole transport layer contains a binder. ,
Since the hole transporting layer containing the binder is plasticized by heat or light, the hole transporting layer made of CuI and Ti having a binder (conductive resin) and a dye adsorbed thereon are used.
Since the O ₂ layer can be bound more firmly and can be made to fit more, the photoelectric conversion element is less deteriorated and the photoelectric conversion efficiency is improved.

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

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment when a photoelectric conversion element of the present invention is applied to a solar cell.

FIG. 2 is an enlarged view showing a cross section in the vicinity of a 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 an electron transport layer on which a dye layer is formed.

FIG. 4 is a schematic diagram showing a configuration of an electron transport layer and a dye layer.

FIG. 5 is a schematic diagram showing the principle of a solar cell.

6 is a diagram showing an equivalent circuit of the solar cell circuit shown in FIG.

[Explanation of symbols]

1A, 1B ... Solar cells 2 ... substrate 3 ... the first electrode 4 ... Electron transport layer 41 ... hole 5: Hole transport layer 51 ... Convex 6 ... second electrode 7: Spacer 8: Barrier layer 11A: laminated body 12A ... Laminate 11B: laminated body 12B ... laminated body 100 ... External circuit 200 …… Diode D ... Dye layer

Claims (16)

[Claims] 1. A first electrode, a second electrode that is installed so as to face the first electrode and has a catalyst layer on its surface, and between the first electrode and the second electrode. Located at least partially in contact with the electron transport layer, a dye layer in contact with the electron transport layer, and the catalyst layer formed on the surface of the electron transport layer and the second electrode. A photoelectric conversion element having a hole transport layer formed of the above, wherein the hole transport layer contains a hole transport material and a binder. 2. The photoelectric conversion element according to claim 1, wherein the binder is a conductive resin. 3. The photoelectric conversion element according to claim 1, wherein the binder is a cyanide. 4. The photoelectric conversion element according to claim 3, wherein the cyanide is a cyanoethylated compound. 5. The photoelectric conversion element according to claim 4, wherein the cyanoethylated product is cyanoethyl cellulose. 6. The photoelectric conversion element according to claim 4, wherein the cyanoethylated product is cyanoethyl hydroxyethyl cellulose. 7. The photoelectric conversion element according to claim 4, wherein the cyanoethylated product is cyanoethyl polyvinyl alcohol. 8. The photoelectric conversion element according to claim 4, wherein the cyanoethylated product is cyanoethyl sucrose. 9. The photoelectric conversion element according to claim 4, wherein the cyanoethylated product is cyanoethyl pullulan. 10. The nitrogen content of the cyanide is 9-1.
It is 5%, The photoelectric conversion element of Claim 3. 11. The refractive index (n ²⁵ ) of the cyanide is
The photoelectric conversion element according to claim 3, which has a thickness of 1.45 to 1.55. 12. The refractive index (n ²⁵ ) of the cyanide is
The photoelectric conversion element according to claim 3, wherein the photoelectric conversion element has a thickness of 1.49 to 1.52. 13. The volume resistivity (Ω-c of the cyanide
The photoelectric conversion element according to claim 3, wherein m) is 5 × 10 ¹² to 1 × 10 ¹² (measured with a super-insulator under conditions of direct current, measurement voltage 50 V, 25 ° C., 60% RH). 14. The true specific gravity (d ²⁵ ) of the cyanide is
The photoelectric conversion element according to claim 3, which has a weight of 1.05 to 1.30 g / cc. 15. The photoelectric conversion element according to claim 1, wherein the binder is plasticized. 16. The photoelectric conversion element according to claim 1, which is a solar cell.