JP2002314108A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell which can provide enough photoelectric conversion efficiency even when it is increased in scale. SOLUTION: A solar cell 1A is a so-called dry solar cell which can be operated without an electrolytic solution and equipped with a board 2, a first electrode 3 (plane electrode) formed on the front surface of the board 2, a light receiving layer 4 formed on the top surface of the first electrode 3, a second electrode (counter electrode) 5 formed on the top surface of the light receiving layer 4, a third electrode 6 formed on the top surface of the second electrode 5, current collectors 10 installed in contact with the first electrode 3, and a connecting part 12 which is continuously formed together with the current collectors 10. The current collector 10 is formed of material smaller in electric resistance than that of the first electrode 3, in contact with the first electrode 3, so that the first electrode 3 is improved in conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a solar cell.

[0002]

2. Description of the Related Art Conventionally, as an environmentally friendly power source,
Solar cells using silicon are attracting attention. Among the solar cells using silicon, there are single-crystal silicon solar cells used for artificial satellites and the like, but practically, solar cells using polycrystalline silicon and amorphous silicon are particularly used. Solar cells have been put into practical use for industrial and home use.

However, these solar cells using silicon all use a vacuum process such as a CVD (Chemical Vapor Deposition) method, so that the manufacturing cost is high, and
In these processes, a large amount of heat and electricity are used, so that the balance between the energy required for manufacturing and the energy generated by the solar cell is extremely poor, and it is not necessarily an energy-saving power source.

On the other hand, a so-called "wet solar cell",
A new type of non-silicon solar cell called a "fourth generation photocell" has been proposed.

[0005] This solar cell has a configuration in which an electrode in which a semiconductor is laminated on a transparent electrode, a counter electrode, and an electrolyte solution are provided between these electrodes.

In such a solar cell, electrons generated in the semiconductor are transmitted to the transparent electrode, and further, the electrons are transmitted to the counter electrode via an external circuit.

However, in this solar cell, when the size of the solar cell is increased, the area of the transparent electrode increases (increase in area).
There is a problem that the electrical resistance of the transparent electrode increases, and as a result, the photoelectric conversion efficiency decreases.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solar cell capable of obtaining a sufficient photoelectric conversion efficiency even when the size is increased.

[0009]

This and other objects are achieved by the present invention which is defined below as (1) to (33).

(1) A porous light-receiving layer mainly composed of titanium oxide, a surface electrode provided on the light-receiving surface side of the light-receiving layer so as to cover the light-receiving surface, A current collector comprising a material having a lower electric resistance than a material of the surface electrode, comprising a current collector having a counter electrode provided to face the surface electrode, and providing a current collector in contact with the surface electrode; A solar cell characterized by being configured to improve overall conductivity.

(2) The ratio of the area occupied by the current collector to the entire area of the surface electrode when viewed from a direction perpendicular to the surface electrode is 0.01 to 10%. Solar cell.

(3) The solar cell according to the above (1) or (2), wherein the current collector is composed of a plurality of linear bodies.

(4) The solar cell according to (3), wherein each of the linear bodies is disposed substantially in parallel.

(5) The solar cell according to (3) or (4), wherein the linear members are arranged in a lattice.

(6) The solar cell according to any one of the above (3) to (5), wherein the linear bodies are respectively disposed at substantially equal intervals.

(7) The solar cell according to (6), wherein the interval is 1 to 10 mm.

(8) The linear body has an average width of 1 to 10.
The solar cell according to any one of the above (3) to (7), which has a thickness of 0 μm.

(9) The linear body has an average height of 0.5.
The solar cell according to any one of the above (3) to (8), which has a thickness of from 50 μm to 50 μm.

(10) The solar cell according to any one of the above (3) to (9), wherein the linear body is a thin metal wire.

(11) The current collector has a conductivity of 1 × 1.
The solar cell according to any one of the above (1) to (10), which has a value of 0 ³ S / m or more.

(12) The current collector is provided so as to be embedded in the plane electrode.
The solar cell according to any one of 1).

(13) The current collector is provided so as to be embedded in the light receiving layer.
The solar cell according to any one of 2).

(14) The solar cell according to any one of (1) to (13), which is formed continuously with the current collector and has a connection portion for connecting an external circuit.

(15) The solar cell according to any one of the above (1) to (14), wherein the titanium oxide is mainly composed of titanium dioxide.

(16) The light receiving layer has an average particle size of 1n.
The solar cell according to any one of the above (1) to (15), which is manufactured using a titanium oxide powder of m to 1 μm.

(17) The light receiving layer has a porosity of 5 to 9
The solar cell according to any one of the above (1) to (16), which is 0%.

(18) The solar cell according to any one of (1) to (17), wherein the light-receiving layer has a surface roughness Ra of 5 nm to 10 μm.

(19) The solar cell according to any one of the above (1) to (18), wherein the light receiving layer has a film shape.

(20) The light-receiving layer has an average thickness of 0.1 mm.
The solar cell according to the above (19), which has a thickness of 1 to 300 μm.

(21) The solar cell according to any one of (1) to (20), wherein a rectifying barrier is formed at an interface between the light receiving layer and the counter electrode.

(22) The solar cell according to the above (21), wherein the counter electrode is made of a substance having ion conduction properties.

(23) The solar cell according to the above (22), wherein the substance having the ion conductive property is a metal halide compound.

(24) The metal halide compound is
The solar cell according to the above (23), which is a metal iodide compound.

(25) The above-mentioned (22) to (22) to the above-mentioned (22) to (22), wherein the counter electrode is formed by applying a material for the counter electrode obtained by dissolving the substance having the ion conductive property in a solvent to the light receiving layer by a coating method. The solar cell according to any one of (24).

(26) The solar cell according to (25), wherein the counter electrode material is applied onto the light receiving layer while heating the light receiving layer.

(27) The material according to (25) or (26), wherein the counter electrode material contains a substance that suppresses an increase in crystal size when the substance having ion conduction properties is crystallized. Solar cells.

(28) The solar cell according to the above (27), wherein the substance is a halide.

(29) The solar cell according to the above (28), wherein the halide is an ammonium halide.

(30) The content of the above (28), wherein the content of the substance in the counter electrode material is 10 ^-4 to 10 ^-1 % by weight.
Or the solar cell according to (29).

(31) An electrolyte is provided between the light receiving layer and the counter electrode (1) or (2).
0) The solar cell according to any of the above.

(32) The solar cell according to (31), wherein a wall member is provided around the light receiving layer and the electrolyte.

(33) The light incident angle on the light receiving layer is 9
The photoelectric conversion efficiency at 0 ° is R _90, and the incident angle of light is 52 °.
Assuming that the photoelectric conversion efficiency of R ₅₂ is R ₅₂ , R ₅₂ / R ₉₀ is in the range of 0.5.
The solar cell according to any one of the above (1) to (32), which has 8 or more.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the solar cell of the present invention shown in the attached drawings will be described below in detail.

<First Embodiment> FIG. 1 is a partial sectional view showing a first embodiment of a solar cell (photovoltaic cell: photoelectric conversion element) of the present invention, and FIG. 2 is a light-receiving layer in the solar cell of the first embodiment. FIG. 3 is an enlarged view showing a cross section near the interface between
FIG. 3 is an enlarged view showing a cross section near a light receiving surface of a light receiving layer in the solar cell of the first embodiment.

The solar cell 1A shown in FIG. 1 is a so-called dry solar cell that does not require an electrolyte solution, and includes a substrate 2 and a first electrode (plane electrode) 3 provided on the upper surface of the substrate 2. A light-receiving layer 4 provided on the upper surface of the first electrode 3, a second electrode (opposite electrode) 5 provided on the upper surface of the light-receiving layer 4, and a second electrode 5 provided on the upper surface of the second electrode 5. 3, an electrode 6, a current collector 10 installed in contact with the first electrode 3, and a connection portion 12 formed continuously with the current collector 10. Is sandwiched between the first electrode 3 and the second electrode 5.

Hereinafter, each component will be described. The substrate 2 is for supporting the current collector 10, the connection portion 12, the first electrode 3, the light receiving layer 4, the second electrode 5, and the third electrode 6, and is composed of a plate-shaped member. ing.

In the solar cell 1A of this embodiment, as shown in FIG. 1, the substrate 2 and a first electrode 3, which will be described later,
For example, light such as sunlight (hereinafter, simply referred to as “light”) is used by being incident (irradiated). Therefore, each of the substrate 2 and the first electrode 3 is preferably substantially transparent (colorless transparent, colored transparent or translucent). Thereby, light can efficiently reach the light receiving surface of the light receiving layer 4.

As a constituent material of the substrate 2, for example,
Examples include various glass materials, various ceramic materials, various plastic materials, resin materials such as polycarbonate (PC), and metal materials such as aluminum.

The average thickness of the substrate 2 is appropriately set according to the material, the use and the like, and is not particularly limited. For example, the average thickness can be as follows.

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

The substrate 2 is made of a flexible material (flexible material) such as polyethylene terephthalate (PET).
, The average thickness is 0.5 to 15
It is preferably about 0 μm, more preferably about 10 to 75 μm. Note that the substrate 2 can be omitted as necessary.

On the upper surface of the substrate 2, a layered (flat) first
(Surface electrode) 3 is provided. In other words, the first electrode 3 is provided on the light receiving surface side of the light receiving layer 4 described later so as to cover the light receiving surface. The first electrode 3 captures electrons generated in the light receiving layer 4.

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 );
One or more of these can be used in combination.

The average thickness of the first electrode 3 is not particularly limited, but is, for example, preferably about 0.05 to 5 μm, and more preferably about 0.1 to 1.5 μm.

On the upper surface of the substrate 2, a current collector 10 composed of a plurality of fine metal wires (linear bodies) 11 is installed so as to be embedded in the first electrode 3. This allows
The current collector 10 is provided so as to be in contact with the first electrode 3. In the present embodiment, the current collector 10 (each thin metal wire 11)
Is not in contact with the light receiving layer 4, but may be provided so as to be in contact with the light receiving layer 4.

These thin metal wires 11 have a substantially semicircular (or semielliptical) cross-sectional shape, and are arranged substantially in parallel and at substantially equal intervals as shown in FIG. The cross-sectional shape of each thin metal wire 11 is not limited to the illustrated shape, and may be, for example, a circle or a polygon such as a triangle, a quadrangle (square, rectangle, or rhombus).

Further, a thin metal wire 1 indicated by a length h in FIG.
The average height (average thickness) of 1 is preferably 0.5
５０50 μm, more preferably about 0.1-20 μm.

Further, a connecting portion 12 in the form of a layer (a flat plate) is continuously formed on each thin metal wire 11 (current collector 10), and an external circuit 900 is connected to the connecting portion 12. ing. The connection part 12 is, as shown in FIG.
Preferably, it is formed integrally with each thin metal wire 11.
Thereby, it is possible to reduce the manufacturing cost and the manufacturing time of the solar cell 1A. In addition, the connection part 12
May be formed separately from each thin metal wire 11.

Such a current collector 10 (each thin metal wire 11)
Is made of a material having lower electric resistance than the material of the first electrode 3.

Therefore, electrons generated in the light receiving layer 4 described later can be captured by the first electrode 3 and pass through the inside of the first electrode 3, but the current collector 10 having a smaller electric resistance can be used. (Each thin metal wire 11) and transmitted from the connection portion 12 to the external circuit 900. That is, the current collector 10 has a function as a bypass line for the electrons captured by the first electrode 3.

As a constituent material of the current collector 10 (each thin metal wire 11), for example, a metal such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum, or a metal containing these is used. Alloys and the like, and one or more of these can be used in combination.

On the upper surface of the first electrode 3, a light receiving layer 4, which preferably has a film shape (layer shape), is provided. Light receiving layer 4
Is porous mainly composed of titanium oxide and has a plurality of holes 41. The light receiving layer 4 generates electrons and holes by receiving light. The details of the light receiving layer 4 will be described later.

On the upper surface of the light receiving layer 4, a layered (flat) second electrode 5 is provided. The second electrode 5 captures holes generated in the light receiving layer 4.

The average thickness of the second electrode 5 is not particularly limited, but is preferably, for example, about 1 to 500 μm, more preferably about 10 to 300 μm, and about 10 to 30 μm. Is more preferred.

As a constituent material of the second electrode 5, for example, a substance having various ion conduction properties, a metal such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum, or the like can be used. Alloys containing these are listed, and one or more of these can be used in combination.

On the upper surface of the second electrode 5, a layered (flat)
The third electrode 6 is provided. Via the third electrode 6, holes are formed in the external circuit 9 connected to the third electrode 6.
Is transmitted to 00.

The average thickness of the third electrode 6 may be a material,
It is appropriately set according to the use and the like, and is not particularly limited.

The constituent material of the third electrode 6 is as follows.
For example, aluminum, nickel, cobalt, platinum,
Metals such as silver, gold, copper, molybdenum, titanium, and tantalum or alloys containing these, carbon, and the like can be given, and one or more of these can be used in combination. Note that the third electrode 6 can be omitted as necessary.

In the solar cell 1A of the present embodiment, a rectifying barrier having diode characteristics is formed at the interface between the second electrode (counter electrode) 5 and the light receiving layer 4, and a rectifying action occurs.

When this situation is represented by an equivalent circuit, a current circulating circuit having a diode 800 as shown in FIG. 4 is formed.

At this time, when light enters the light receiving layer 4,
In the light receiving layer 4, electrons are excited, and electrons and holes are generated. In addition, an electric field exists at the rectification barrier due to the interface potential. Therefore, these electrons and holes are
The potential difference (photoelectromotive force) is generated between the connection portion 12 (first electrode 3) and the third electrode 6 by the electric field at the interface.
Occurs, and a current (light excitation current) flows through the external circuit 900.

To obtain such a rectifying barrier, the second
As a constituent material of the electrode 5, among the materials described above,
In particular, a substance having ion conduction properties is preferably used.

Examples of the substance having ion conductivity include metal iodide compounds such as CuI and AgI, metal halide compounds such as metal bromide compounds such as AgBr, and metal thiocyanate compounds such as CuSCN. And the like. One or more of these compounds can be used in combination. Among them, one or more of metal iodide compounds such as CuI and AgI can be used. More preferably, they are used in combination. By using such a metal iodide compound, the photoelectric conversion efficiency (energy conversion efficiency) of solar cell 1A can be further improved.

The second electrode 5 is preferably formed so as to penetrate into the hole 41 of the light receiving layer 4 as shown in FIG. Thereby, the formation region of the rectification barrier can be increased, and the solar cell 1A can further improve the power generation efficiency.

The rectifying barrier may be formed not at the interface between the light receiving layer 4 and the second electrode 5 but at the interface between the light receiving layer 4 and the first electrode 3 or at both of them. May be.

The light receiving layer 4 is irradiated with light (received light).
In this example, electrons and holes are simultaneously generated, but in the following description, "electrons are generated" for convenience.

The present invention is characterized in that the above-described current collector 10 is provided to improve the conductivity of the entire first electrode 3. Hereinafter, this point will be described.

In a solar cell without the current collector 10, electrons generated in the light receiving layer 4 are captured by the first electrode 3 and transmitted to the external circuit 900 via the first electrode 3. Will be.

In such a solar cell, when the size is increased, the area occupied by the first electrode 3 needs to be large (the first electrode 3 has a large area). The first electrode 3 is made of a metal oxide as described above, and this metal oxide has a relatively large electric resistance. For this reason,
By increasing the area of the first electrode 3, the first electrode 3
In this case, the electric resistance increases, and the power generation efficiency (photoelectric conversion efficiency) of the solar cell decreases.

On the other hand, in the present invention, since the current collector 10 is provided so as to be in contact with the first electrode 3, even if the solar cell 1 A is enlarged, the electrons captured by the first electrode 3 can be reduced. , Passed to the current collector 10 and efficiently connected to the external circuit 9.
Is transmitted to 00. That is, in the solar cell 1A, an increase in the electrical resistance of the first electrode 3 due to the increase in the area is suppressed (first
Of the electrode 3 as a whole), and as a result, a decrease in power generation efficiency (photoelectric conversion efficiency) can be suitably prevented.

From the viewpoint of suppressing (preventing) an increase in the electric resistance of the first electrode 3, it is preferable to increase the area occupied by the current collector 10. Is too large, the light arrival rate on the light receiving surface of the light receiving layer 4 is reduced. Therefore, the occupied area (formation area) of the current collector 10 has a suitable range.

Specifically, when viewed from a direction perpendicular to the first electrode 3, the current collector 1 corresponds to the entire area of the first electrode 3.
The ratio of the area occupied by 0 (the arrangement density of the current collectors 10) is preferably, for example, about 0.01 to 10%.
More preferably, it is about 03 to 5%.

As a result, in the solar cell 1A, the conductivity of the entire first electrode 3 can be further improved, and a decrease in the rate of light reaching the light receiving surface of the light receiving layer 4 can be suitably prevented. Therefore, the power generation efficiency (photoelectric conversion efficiency) can be significantly improved.

Thus, the average width (length w in FIG. 1) of the thin metal wires 11 is preferably about 1 to 100 μm, more preferably about 1.5 to 50 μm. Are respectively (length a in FIG. 1)
Preferably about 1 to 10 mm, more preferably 3 to 7 m
m.

The current collector 10 has a conductivity
For example, it is preferably about 1 × 10 ³ S / m or more, and more preferably about 1 × 10 ⁵ S / m or more. By setting the conductivity of the current collector 10 to the above numerical range, the solar cell 1 </ b> A can further improve the conductivity of the entire first electrode 3.

Further, as described above, each metal wire 11
Are arranged substantially in parallel and at substantially equal intervals, respectively. Thereby, the conductivity of the entire first electrode 3 can be made more uniform, so that in the solar cell 1A, the light receiving layer 4
Can be taken out without unevenness.

Next, the light receiving layer 4 will be described in detail. The light receiving layer 4 is mainly composed of titanium oxide as described above.

Examples of the titanium oxide include titanium dioxide, titanium monoxide, dititanium trioxide and the like, and one or more of these can be used in combination. Is preferably mainly composed of titanium dioxide. Since titanium dioxide has high sensitivity to light, the light use efficiency of the light receiving layer 4 using titanium dioxide as the titanium oxide is further improved.

Further, as the titanium dioxide, those having a crystal structure mainly of anatase-type titanium dioxide, those mainly comprising rutile-type titanium dioxide, and a mixture of anatase-type titanium dioxide and rutile-type titanium dioxide can be used. Any of the main ones may be used.

Since rutile-type titanium dioxide can use light having a wavelength in the visible light region near the ultraviolet region, the light-receiving layer 4 mainly composed of rutile-type titanium dioxide has a light It has the advantage of excellent utilization efficiency.

Since the crystal structure of rutile-type titanium dioxide is stable, even if the light-receiving layer 4 mainly composed of rutile-type titanium dioxide is exposed to a severe environment, it changes over time ( (Deterioration) is small and stable performance can be obtained continuously for a long period of time.

On the other hand, since the crystal structure of anatase-type titanium dioxide is relatively unstable, the light-receiving layer 4 mainly composed of anatase-type titanium dioxide has an advantage that electrons are easily generated. .

Further, the light-receiving layer 4 mainly composed of a mixture of rutile-type titanium dioxide and anatase-type titanium dioxide can have the above-mentioned advantages.

When mixed in this way, the rutile-type titanium dioxide and the anatase-type titanium dioxide are not particularly limited. For example, the weight ratio is 95: 5 to 5: 9.
It is preferably about 5 and more preferably about 80:20 to 20:80.

The light receiving layer 4 is porous as described above, and has a plurality of holes 41. FIG.
A state where light is incident near the light receiving surface of the light receiving layer 4 is schematically shown. In FIG. 3, the substrate 2, the current collector 1
0, the connection portion 12 and the first electrode 3 are omitted. As shown in FIG. 3, in the porous light-receiving layer 4, light (arrows in FIG. 3) penetrates from the surface (light-receiving surface) of the light-receiving layer 4 further into the inside thereof, and passes through the light-receiving layer 4 or passes through the hole. It is reflected within 41. For this reason, light is more frequently transmitted to the light receiving layer 4.
Since electrons are generated in the light receiving layer 4, the light use efficiency of the light receiving layer 4 is improved.

In this case, the surface area of the light receiving layer 4 is significantly increased (for example, 50 to 10,000 times) as compared with the surface area of the dense light receiving layer. Thereby, the solar cell 1A using such a light receiving layer 4 has a large current (for example, 50 to 100) as compared with a solar cell using a dense light receiving layer.
10,000 times).

The index indicating the degree of such porosity includes, for example, the porosity (porosity) of the light-receiving layer 4, the surface roughness Ra of the light-receiving surface of the light-receiving layer 4, and the like. It is preferable that one of the porosity and the surface roughness Ra of the light receiving surface satisfies the following condition, and that both the porosity and the surface roughness Ra of the light receiving surface satisfy the following condition. preferable.

Although the porosity of the light receiving layer 4 is not particularly limited, it is preferably, for example, about 5 to 90%.
More preferably, it is about 15 to 50%.
% Is more preferable.

The surface roughness Ra of the light receiving surface of the light receiving layer 4 is not particularly limited.
m, more preferably about 20 nm to 1 μm.

In the light-receiving layer 4 whose degree of porosity is within the above-mentioned range, light use efficiency is further improved, and electrons can be generated more reliably.

From such a viewpoint, it is preferable that the light receiving layer 4 is manufactured using titanium oxide powder (powder-like titanium oxide). Thereby, the light receiving layer 4 can be easily and reliably made porous.

The average particle size of the titanium oxide powder is not particularly limited, but is, for example, preferably about 1 nm to 1 μm, and more preferably about 5 to 50 nm. By setting the average particle size of the titanium oxide powder within the above range, the uniformity of the titanium oxide powder in the light-receiving layer material can be improved. In addition, by reducing the average particle size of the titanium oxide powder in this way, the specific surface area (surface area) of the obtained light receiving layer 4 can be further increased.

The light receiving layer 4 may have a relatively large thickness, but preferably has a film shape (layer shape) as described above. By using the light receiving layer 4 in the form of a film for the solar cell 1A, the power generation efficiency of the solar cell 1A can be further improved, and the thinning (miniaturization) and manufacturing cost of the solar cell 1A can be advantageously reduced. .

In this case, the average thickness (film thickness) of the light receiving layer 4 is not particularly limited.
It is preferably about μm, more preferably about 0.5 to 100 μm, and even more preferably about 1 to 25 μm. When the average thickness of the light-receiving layer 4 is less than the lower limit described above, depending on the porosity and the like, the light incident on the light-receiving layer 4 is significantly transmitted, and the light use efficiency may be reduced. On the other hand, even if the thickness of the light receiving layer 4 is increased beyond the above-mentioned upper limit value, further increase in light use efficiency cannot be expected.

Further, such a light-receiving layer 4 is subjected to a visualization process so as to be in a visible light region (usually 400 to 750 nm).
It is preferable that light of a wide range of wavelengths can be absorbed. Thereby, the light receiving layer 4 can further improve the light use efficiency and generate electrons more reliably, that is, can further improve the photoelectric conversion efficiency (photoelectric quantum efficiency).

Examples of such a visualization method include a dye adsorption method for adsorbing a dye, an oxygen defect formation method for forming oxygen defects, and an atomic substitution method for substituting a part of titanium atoms with a metal atom different from titanium atoms. And the like, and one or more of these can be used in combination. Hereinafter, each of these methods will be described in detail.

Dye Adsorption Method In the dye adsorption method, a film-like material (hereinafter, simply referred to as a “film-like material”) in which a light-receiving layer material is formed into a film and a solvent in which, for example, a dye is dissolved or suspended (dispersed) Is brought into contact with, for example, dipping, coating, or the like, so that the dye is adsorbed on the surface of the film and in the pores.

The dye is not particularly limited.
For example, pigments, dyes and the like can be mentioned, and these can be used alone or as a mixture.However, deterioration with time, pigments in that deterioration is less, and dyes in terms of more excellent adsorptivity are used. Is preferred.

The pigment is not particularly limited. For example, phthalocyanine pigments such as phthalocyanine green and phthalocyanine blue, fast yellow,
Azo series such as disazo yellow, condensed azo yellow, penzoimidazolone yellow, dinitroaniline orange, penzimidazolone orange, toluidine red, permanent carmine, permanent red, naphthol red, condensed azo red, benzimidazolone carmine, benzimidazolone brown, etc. 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, and quinacridone red. Organic pigments such as quinacridone pigments, perylene pigments such as perylene red and perylene maroon, pyrrolopyrrole pigments such as diketopyrrolopyrrole red, dioxazine pigments such as dioxazine violet, carbon black, lamp black, furnace black, Carbon pigments such as ivory black, graphite, fullerene, etc., chromate pigments such as graphite, molybdate orange, cadmium yellow, cadmium lithopone yellow, cadmium oxide , Cadmium lithopone orange, silver vermilion, cadmium red, cadmium lithopone red, sulfide-based pigments such as sulfide, ocher, titanium yellow, titanium barium nickel yellow, red iron, lead red, amber, brown iron oxide, zinc iron chrome brown Oxides such as chromium 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 Pigments, hydroxide pigments such as viridian,
Examples include ferrocyanide pigments such as navy 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. And
One or more of these can be used in combination.

The dye is not particularly limited. For example, RuL ₂ (SCN) ₂ , RuL ₂ Cl ₂ , RuL ₂ (CN) ₂ ,
um535-bisTBA (manufactured by Solaronics), metal complex dyes such as [RuL ₂ (NCS) ₂ ] ₂ H ₂ O, cyan dyes, xanthene dyes, azo dyes, hibiscus dyes, blackberry dyes, raspberry dyes, Pomegranate juice pigments, chlorophyll pigments and the like can be mentioned, and one or more of these can be used in combination. Here, L in the above composition formula represents 2,2′-bipyridine or a derivative thereof.

Oxygen Deficiency Forming Method The oxygen deficiency forming method is not particularly limited. For example, a method in which a titanium oxide powder or a film is heat-treated in a hydrogen atmosphere (reducing atmosphere), a vacuum (for example, 10 ⁻⁵ to 10 ⁻⁵ )
A method of performing a heat treatment under 10 ⁻⁶ Torr), a method of performing a low-temperature plasma treatment, and the like are given. Among them, as the oxygen defect forming method, a method of heat-treating a titanium oxide powder or a film in a hydrogen atmosphere is preferable.

Atom Replacement Method As the atom replacement method, for example, a method of baking (sintering) a film of a light-receiving layer material to which an inorganic sensitizer made of the above-described metal atom or its oxide is added, Injects (drives) ionized metal atoms into the body
Method and the like. Among them, as the atom replacement method, a method of firing a film of the light-receiving layer material to which the inorganic sensitizer is added is more preferable. In addition, such an atom substitution method can be applied to titanium oxide powder.

A solar cell 1A using such a light receiving layer 4
In this example, when the photoelectric conversion efficiency at a light incident angle of 90 ° on the light receiving layer 4 is R ₉₀ and the photoelectric conversion efficiency at a light incident angle of 52 ° is R ₅₂ , R ₅₂ / R ₉₀ is 0. It is preferable to have a characteristic of about 0.8 or more, more preferably about 0.85 or more. Satisfying such a condition means that the light receiving layer 4 has low directivity to light, that is, has light isotropy. Therefore, the solar cell 1A having such a light receiving layer 4 can generate power more efficiently over almost the entire sunshine duration.

Such a solar cell 1A can be manufactured, for example, as follows. First, a substrate 2 made of, for example, quartz glass is prepared. As the substrate 2, a substrate having a uniform thickness and no bending is preferably used.

<0> First, the current collector 10 (each fine metal wire 1)
1) The connection portion 12 is formed on the upper surface of the substrate 2.

The current collector 10 and the connection portion 12 are made of, for example, a vapor deposition method, a sputtering method, a CVD method, a plating method, and a paste printing method. Can be patterned (pattern formation) by a method of baking the print layer after forming the print layer by the method described above, or a method of supplying (coating) the conductive layer as a conductive adhesive.

The material of the current collector 10 and the material of the connection portion 12 may be different.

After the metal wires 11 have been formed, they may be arranged on the upper surface of the substrate 2.

<1> Next, the first electrode 3 is formed on the upper surface of the substrate 2 so as to cover the current collector 10.

The first electrode 3 can be formed by using a material for the first electrode 3 made of, for example, ITO or the like by using, for example, an evaporation method, a sputtering method, a printing method, or the like. Thereby, the current collector 10 is embedded in the first electrode 3.

<2> Next, the light receiving layer 4 is formed on the upper surface of the first electrode 3. The light receiving layer 4 is made of a light receiving layer material, for example,
Various coating methods such as dipping, doctor blade, spin coating, brush coating, spray coating, roll coater, etc.
It can be formed into a film (thick film and thin film) by a method such as thermal spraying. Among them, the method for forming the light receiving layer 4 is preferably a method using various coating methods.

According to such a coating method, the operation is as follows:
Since it is extremely simple and does not require a large-scale device, it is advantageous for reducing the manufacturing cost and the manufacturing time of the light receiving layer 4 and the solar cell 1A. Further, according to the coating method, the light receiving layer 4 having a desired pattern shape can be easily obtained by using, for example, masking.

Hereinafter, an example of a forming method of the light receiving layer 4 by a coating method will be described. In the following description, the method of visualization processing (<2A> dye adsorption method, <2B>, <2C
> Oxygen deficiency forming method and <2D> atom replacement method), but the same matters will not be described later. Further, regarding the oxygen defect forming method, <2B> the case where the method is applied to the titanium oxide powder and the <2C>
The description will be made separately for the case of applying to a film-like body.

<2A>: Dye adsorption method [Preparation of titanium oxide powder] <A0> A predetermined mixing ratio of rutile type titanium dioxide powder and anatase type titanium dioxide powder (only anatase type titanium dioxide powder, rutile type titanium dioxide powder) (Including the case of using only titanium dioxide powder).

The average particle size of the rutile type titanium dioxide powder and the average particle size of the anatase type titanium dioxide powder may be different or the same, respectively. Is preferred. The average particle size of the entire titanium oxide powder is in the above-mentioned range.

[Preparation of Coating Solution (Light-Receiving Layer Material)] <A1> First, the titanium oxide powder prepared in the above step was mixed with an appropriate amount of water (for example, distilled water, ultrapure water, ion-exchanged water,
RO water, etc.).

<A2> Next, a stabilizer such as nitric acid is added to the suspension, and the suspension is sufficiently kneaded in a mortar made of agate (or made of alumina).

<A3> Next, the above-mentioned water is added to the suspension, followed by further kneading. At this time, the mixing ratio of the stabilizer to water is preferably 10:90 to 4 by volume ratio.
About 0:60, more preferably 15:85 to 30:70
And the viscosity of the suspension is, for example, 0.2-30.
Approximately cP.

<A4> Thereafter, a surfactant is added to the suspension so as to have a final concentration of, for example, about 0.01 to 5% by weight and kneaded. Thereby, a coating liquid (light-receiving layer material) is prepared.

The surfactant is cationic,
Any of anionic, amphoteric, and nonionic may be used, but a nonionic one is preferably used.

Further, as a stabilizer, nitric acid is used instead of nitric acid.
A titanium oxide surface modification reagent such as acetic acid or acetylacetone can also be used.

Further, various additives such as a binder such as polyethylene glycol, a plasticizer, and an antioxidant may be added to the coating liquid (light-receiving layer material) as necessary.

[Formation of Light-Receiving Layer 4] <A5> A coating solution is applied and dried on the upper surface of the first electrode 3 by a coating method (for example, dipping or the like) to form a film (coating). . Alternatively, the coating and drying operations may be performed a plurality of times to laminate.

Next, if necessary, the film 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. As a result, the titanium oxide powder that has just stopped contacting is diffused at the contact portion, and the titanium oxide powders are fixed (fixed) to some extent. In this state, the film becomes porous.

<A6> The film-like body obtained in the step <A5> may be subjected to post-treatment, if necessary.

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

The surface roughness Ra of the light receiving surface may be adjusted by the post-processing in the step <A6>.

<A7> Next, a laminate of the substrate 2, the current collector 10, the connection portion 12, the first electrode 3, and the film-like body is added to a solution in which a dye such as carbon black is dissolved or suspended (dispersed). Is immersed. As a result, the solution penetrates into the pores of the film and reaches the first electrode 3 side, and the dye is adsorbed on the surface and the pores of the film.

The solvent for dissolving or suspending (dispersing) the dye is not particularly limited. For example, 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 these can be used in combination.

Thereafter, the laminate is taken out of the solution, 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 may be dried in a clean oven or the like at a temperature of, for example, about 60 to 100 ° C. for about 0.5 to 2 hours. This allows the dye to be more firmly adsorbed on the film.

<2B>: Oxygen defect formation method (when applied to titanium oxide powder) [Preparation of titanium oxide powder] <B0> A predetermined mixing ratio (rutile) of rutile type titanium dioxide powder and anatase type titanium dioxide powder (Including the case of only the titanium dioxide powder of the type)). In addition, by the heat treatment by the oxygen defect formation method described later,
When it is assumed that the crystal structure of titanium dioxide changes (changes) from anatase type to rutile type, only anatase type titanium dioxide powder may be used.

Next, the titanium oxide powder thus compounded was
Heat treatment by an oxygen defect forming method is performed. The heat treatment at this time is performed in a hydrogen atmosphere, preferably at a temperature of 800.
The temperature is about 1200 to 1200 ° C. and about 0.2 to 3 hours, more preferably about 900 to 1200 ° C. and about 0.5 to 1 hour.

At this time, when the titanium oxide powder contains anatase-type titanium dioxide powder, depending on the heat treatment temperature and heat treatment time, the anatase-type titanium dioxide has a part or all of the crystal structure of rutile. May transfer to the mold.

In the oxygen defect forming method, this step <B0>
Before this, a titanium oxide powder may be prepared by applying to rutile-type titanium dioxide powder and / or anatase-type titanium dioxide powder and blending the titanium dioxide powder.

[Preparation of Coating Liquid (Light-Receiving Layer Material)] <B1> to <B4> Steps similar to the above steps <A1> to <A4> are performed.

[Formation of Light-Receiving Layer 4] <B5> The same step as the step <A5> is performed.

<B6> If necessary, the step <A6
>. The step <A7> for dye adsorption is omitted.

<2C>: Oxygen vacancy forming method (when applied to a film) [Preparation of Titanium Oxide Powder] <C0> A predetermined mixing ratio (rutile) of rutile-type titanium dioxide powder and anatase-type titanium dioxide powder (Including the case of only the titanium dioxide powder of the type)). In addition, by the heat treatment by the oxygen defect formation method described later,
When it is assumed that the crystal structure of titanium dioxide changes (changes) from anatase type to rutile type, only anatase type titanium dioxide powder may be used.

[Preparation of Coating Solution (Light-Receiving Layer Material)] <C1> to <C4> Steps similar to the above steps <A1> to <A4> are performed.

[Formation of Light-Receiving Layer 4] <C5> After performing the same step as the above-mentioned step <A5>,
The light receiving layer 4 is formed by subjecting the film to a heat treatment by an oxygen defect forming method.
Get. The heat treatment is performed in a hydrogen atmosphere, preferably at a temperature of about 800 to 1200 ° C. for about 0.2 to 3 hours, more preferably at a temperature of about 900 to 1200 ° C. for about 0.5 to 1 hour. .

In this case, the heat treatment (for example, baking) in the step <A5> can be also used as the heat treatment by the oxygen defect forming method.

<C6> If necessary, the step <A6
>. The step <A7> for dye adsorption is omitted.

<2D>: Atomic substitution method [Preparation of titanium oxide powder] <D0> A predetermined mixing ratio of rutile-type titanium dioxide powder and anatase-type titanium dioxide powder (even when only rutile-type titanium dioxide powder is used) ) And mix. When it is assumed that the crystal structure of titanium dioxide changes (changes) from an anatase type to a rutile type by baking by an atom replacement method described later, only anatase type titanium dioxide powder may be used. .

[Preparation of coating liquid (light-receiving layer material)] <D1> to <D3> Steps similar to the above steps <A1> to <A3> are performed.

<D4> In the same step as the step <A4>, an inorganic sensitizer is added to the suspension and kneaded. Thereby, a coating liquid (light-receiving layer material) is prepared.

Examples of the inorganic sensitizer include, but are not particularly limited to, chromium, vanadium, nickel, iron, manganese, copper, zinc, niobium, and oxides thereof. Alternatively, two or more kinds can be used in combination.

The content of the inorganic sensitizer is not particularly limited, but is preferably, for example, about 0.1 to 2.5 μmol per 1 g of the titanium oxide powder.
More preferably, it is about 0.5 to 2.0 μmol.

When the titanium oxide powder contains anatase-type titanium dioxide powder and it is desired to prevent the crystal structure of the anatase-type titanium dioxide from changing to the rutile type, a sintering aid is added. I do.

The sintering aid is preferably a metal oxide having a melting point of 900 ° C. or less. The metal oxide is not particularly limited, for example, molybdenum trioxide,
Bismuth trioxide, lead oxide, palladium oxide, diantimony trioxide, tellurium dioxide, dithallium trioxide and the like can be mentioned, and one or more of these can be used in combination.

In this case, the mixing ratio of the sintering aid and the titanium oxide powder is not particularly limited, but is preferably, for example, about 1:99 to 40:60 by volume, preferably 5:40:60.
The ratio is more preferably about 95 to 20:80.

As a result, the film can be fired (sintered) at a temperature of 900 ° C. or less, so that the transition of the crystal structure of titanium dioxide from anatase type to rutile type can be more reliably prevented (suppressed). Can be.

[Formation of Light-Receiving Layer 4] <D5> After performing the same step as the step <A5>,
For example, air, nitrogen gas, or various inert
Gas, vacuum, reduced pressure (for example, 10^-1-10 ^-6Tor
It is fired (sintered) in a non-oxidizing atmosphere as in r).

The firing conditions at this time can be, for example, as follows. When the titanium oxide powder does not contain anatase-type titanium dioxide powder, or when it is assumed that the crystal structure of titanium dioxide changes from anatase-type to rutile-type, the temperature is preferably 0.1 to 1200 ° C. It is about 5 to 10 hours.

When it is not assumed that the crystal structure of titanium dioxide changes from an anatase type to a rutile type (it is desired to prevent it), it is preferable that the temperature be about 900 ° C. or lower and 1 to 1
It is about 26 hours.

In this case, the heat treatment (for example, sintering or the like) in the step <A5> can also be used for the sintering by the atomic substitution method.

In addition, such an atomic substitution method may be applied to rutile-type titanium dioxide powder and / or anatase-type titanium dioxide powder before preparing titanium oxide powder. The titanium oxide powder may be applied later. In these cases, the firing by the atom replacement method in the present step <D5>
Can be omitted.

<D6> If necessary, the step <A6
>. The step <A7> for dye adsorption is omitted. Through the steps described above, the light receiving layer 4 is obtained.

<3> Next, the second electrode 5 is formed on the upper surface of the light receiving layer 4. The second electrode 5 is formed, for example, by dipping, dripping, or dripping the material of the second electrode 5 (counter electrode material) obtained by dissolving a substance having ion conductivity such as CuI in a solvent on the upper surface of the light receiving layer 4. It is preferable to form by applying by various coating methods such as blade, spin coating, brush coating, spray coating and roll coater.

According to such a coating method, the second electrode 5
In the hole 41 of the light receiving layer 4.

After the coating film is formed, the coating film may be subjected to a heat treatment. However, the material of the second electrode 5 is applied to the upper surface of the light receiving layer 4 while heating the light receiving layer 4. Is preferred. Thereby, it is advantageous to form the second electrode 5 more quickly, that is, to shorten the manufacturing time of the solar cell 1A. The heating temperature is preferably about 50 to 100 ° C. In the case where heat treatment is performed after the coating film is formed, the coating film may be dried before the heat treatment. Further, the above operation may be repeatedly performed a plurality of times.

More specifically, the substrate 2, the current collector 10, and the connection portion 1 were placed on a hot plate heated to about 80 ° C.
2. A laminated body of the first electrode 3 and the light receiving layer 4 is provided, and the material of the second electrode 5 is dropped on the upper surface of the light receiving layer 4 and dried. This operation is repeated a plurality of times to form the second electrode 5 having the average thickness as described above.

The solvent for dissolving the substance having the ion conductive property is not particularly limited. For example, an organic solvent such as acetonitrile is preferably used.

It is preferable that the material of the second electrode 5 contains a substance that suppresses an increase in crystal size when a substance having ion conduction properties is crystallized.

If the material of the second electrode 5 does not contain this substance, the type of the substance having ion conduction properties,
Depending on the above-mentioned heating temperature or the like, when the substance having ion conduction properties is crystallized, the crystal size becomes too large (the volume expansion of the crystal proceeds excessively). If it occurs inside the light-receiving layer 41, cracks occur in the light-receiving layer 4, and as a result, the second electrode 5 and the first electrode 3
Short-circuit (contact) may occur.

On the other hand, if the material of the second electrode 5 contains this substance, the substance having ion conduction properties becomes
The crystal size is relatively small. For this reason, the above-mentioned inconvenience can be suitably suppressed.

Examples of such a substance include, but are not limited to, halides such as ammonium halide, and particularly, ammonium halide such as tetrapropylammonium iodide (TPAI) is preferably used. By using tetrapropylammonium iodide, an increase in the crystal size of a substance having ion conduction properties can be more suitably suppressed.

Although the content of this substance in the material of the second electrode 5 is not particularly limited, for example, 10 ^-4
It is preferably about 10 ^-1 wt% (wt%).
More preferably, it is about 0 ^-4 to 10 ^-2 wt%. Within such a numerical range, the above-mentioned effect becomes more remarkable.

<4> Next, the third electrode 6 is formed on the upper surface of the second electrode 5. The third electrode 6 is made of a material for the third electrode 6 made of, for example, platinum, for example, by a vapor deposition method,
It can be formed by using a sputtering method, a printing method, or the like. Through the steps described above, solar cell 1A is manufactured.

The solar cell 1A includes a laminate in which the second electrode 5 is formed on the upper surface of the third electrode 6, the substrate 2, the current collector 10, the connection portion 12, the first electrode 3, and the light receiving layer. 4 can be manufactured by joining the light receiving layer 4 and the second electrode 5 so as to be in contact with each other.

Further, the second electrode 5 and / or the third electrode 6 are made of the same material as the first electrode 3,
That is, it can be a transparent electrode. In this case, the above-described current collector 10 may be provided so as to be in contact with these electrodes.

The current collector 10 may be installed so as to be embedded in both the first electrode 3 and the light receiving layer 4, or may be provided on the surface of the first electrode 3 opposite to the light receiving layer. (A lower surface in FIG. 1) so as to protrude from the substrate 2.

<Second Embodiment> Next, a second embodiment of the solar cell of the present invention will be described.

FIG. 5 is a partial sectional view showing a second embodiment of the solar cell of the present invention. Hereinafter, the solar cell 1 shown in FIG.
Regarding B, differences from the solar cell 1A of the first embodiment will be described, and description of the same items will be omitted.

In the solar cell 1B shown in FIG.
Except that the solar cell 1 of the first embodiment is different.
Same as A.

That is, the current collector 10 is composed of a plurality of fine metal wires (linear bodies) 11 arranged in a lattice.

As a result, the conductivity of the first electrode 3 as a whole can be made more uniform, so that in the solar cell 1B, electrons generated in the light receiving layer 4 can be taken out more evenly.

Further, even when a part of the thin metal wire 11 is broken, there is an advantage that electrons can be taken out from the connection portion 12 to the external circuit 900 via another path which is not broken. is there.

<Third Embodiment> Next, a third embodiment of the solar cell of the present invention will be described.

FIG. 6 is a partial sectional view showing a third embodiment of the solar cell of the present invention. Hereinafter, the solar cell 1 shown in FIG.
Regarding C, differences from the solar cell 1A of the first embodiment will be described, and description of similar items will be omitted.

In the solar cell 1C shown in FIG.
It is the same as the solar cell 1A of the first embodiment, except that the installation position is different.

That is, the current collector 10 is disposed so as to be embedded in the light receiving layer 4. Specifically, a current collector 10 is formed on the upper surface of the first electrode 3, and the current collector 10
The light receiving layer 4 is formed so as to cover.

In this embodiment, since the current collector 10 is in direct contact with the light receiving layer 4, there is an advantage that electrons generated in the light receiving layer 4 can be directly taken into the current collector 10 having a low electric resistance.

<Fourth Embodiment> Next, a fourth embodiment of the solar cell of the present invention will be described.

FIG. 7 is a partial sectional view showing a third embodiment of the solar cell of the present invention, and FIG. 8 is an enlarged view showing a section near the light receiving surface of the light receiving layer in the solar cell of the fourth embodiment. is there.

Hereinafter, the solar cell 1D shown in FIG.
Differences from the solar cell 1A of the first embodiment will be described, and description of the same items will be omitted.

A solar cell 1D shown in FIG.
0, a first electrode (plane electrode) 30 provided on the upper surface of the first substrate 20, a light receiving layer 40 provided on the upper surface of the first electrode 30, and provided so as to surround the light receiving layer 40,
A wall (wall member) 90 having a storage space 80 therein.
A second electrode (opposite electrode) 50 disposed opposite to the first electrode 30 with the light receiving layer 40 interposed therebetween; and a second electrode 50
, An electrolyte solution (liquid electrolyte) 81 stored in a storage space 80, and a current collector 1 installed in contact with the first electrode 30.
00 and a connection portion 1 formed continuously on the current collector 100
20.

Hereinafter, each component will be described. First
The substrate 20 is a support member for the current collector 100, the connection portion 120, and the first electrode 30, and is formed of a plate-shaped member.

In the solar cell 1D of the present embodiment, as shown in FIG. 7, the first substrate 20 and the first electrode
It is used by irradiating (irradiating) light from the 0 side. Therefore, the first substrate 20 and the first electrode 30
Are preferably each substantially transparent (colorless transparent, colored transparent or translucent). Thereby, light can efficiently reach the light receiving surface of the light receiving layer 40.

The first substrate 20 and a second substrate 70 described later can have the same configuration as the substrate 2 of the first embodiment. Note that the first substrate 20 can be omitted as necessary.

On the upper surface of the first substrate 20, a first electrode 30 having a layered (flat) shape and a current collector 100 (each thin metal wire 11) are formed.
0) and the connection part 120 are provided.

The first electrode 30 and the current collector 100
The (each thin metal wire 110) and the connection portion 120 can have the same configuration as the first electrode 3, the current collector 10 (the thin metal wire 11), and the connection portion 12 of the first embodiment, respectively.

On the upper surface of the first electrode 30, a light receiving layer 40 is provided. The light receiving layer 40 can have the same configuration as the light receiving layer 4 of the first embodiment.

Further, as shown in FIG.
It has a plurality of holes 401. Thereby, the light receiving layer 40
It is possible to increase the area of light irradiation to the light-receiving layer 40 and the contact area between the light-receiving layer 40 and the electrolyte solution 81.

The light receiving layer 40 and a second electrode 5 described later
0, an electrolyte solution (liquid electrolyte) 81 is provided, and around the light receiving layer 40 and the electrolyte solution 81,
A wall 90 is provided.

In other words, on the upper surface of the first electrode 30,
A wall portion 90 is erected so as to surround the light receiving layer 40, and the light receiving layer 40, a second electrode 50 described below, and a storage space 80 are defined inside the wall portion 90. An electrolyte solution 81 is stored.

The wall portion 90 has a function as a sealing member for hermetically sealing the side surface of the solar cell 1D. The wall portion 90 reduces the distance (distance) between the first electrode 30 and the second electrode 50. It also functions as a spacer that keeps constant.

When the wall portion 90 has a function as a spacer, the solar cell 1D must maintain its strength, in particular, at least the light receiving layer 40 and the electrolyte solution 81.
(Electrolyte) deformation can be prevented. For this reason,
In the solar cell 1D, the ionic conduction state of the electrolyte solution 81 can be made suitable, and as a result, the power generation efficiency (photoelectric conversion efficiency) can be further improved.

The average width (length in the horizontal direction in FIG. 7) of the wall portion 90 is not particularly limited.
mm, more preferably about 0.5 to 5 mm.

The average height of the wall portion 90 (the length in the vertical direction in FIG. 7), that is, the average thickness of the wall portion 90 is not particularly limited, but is, for example, about 0.001 to 1.0 mm. Is preferred, and more preferably about 0.01 to 0.1 mm.

The wall section 90 is made of an insulating material. As this insulating material, for example, polycarbonate, ultraviolet curing resin, thermosetting resin, epoxy resin,
Examples include various resin materials such as polyimide resin, various glass materials, various free-cutting ceramic materials, and the like, and one or more of these materials can be used in combination. In particular, when the wall portion 90 has a function as a spacer, it is more excellent in strength.
Among the above materials, it is preferable to use polycarbonate and various glass materials.

When the wall portion 90 is made of a material having resistance to ultraviolet rays, such as low-melting glass, for example, it is necessary to prevent the wall portion 90 from being deteriorated or deteriorated with time due to light irradiation. The solar cell 1D has an electrolyte solution 81
Liquid leakage can be more reliably prevented, and the durability can be further improved.

[0213] From such a viewpoint, the wall portion 90 may be formed integrally with the first substrate 20 or a second substrate 70 described later.

A second electrode 50 is provided on the upper surface of the wall 90 so as to face the light receiving layer 40. That is, the second electrode (counter electrode) 50 is provided to face the first electrode (plane electrode) 30 via the light receiving layer 40. This second
The electrode 50 can have the same configuration as the third electrode 6 of the first embodiment.

On the upper surface of the second electrode 50, a plate-shaped second
Substrate 70 is provided. This second substrate 70
It is a support member for the second electrode 50. Note that the second substrate 70 can be omitted as necessary.

[0216] In the storage space 80, an electrolyte solution 81 is stored as an electrolyte. The electrolyte solution 81 is not particularly limited. For example, an I / I ₃ system, Br
/ Br ₃ system, Cl / Cl ₃ system, F / F ₃ based halogen-based, such as, quinone / hydroquinone system redox electrolyte of: a combination of one or more of (a redox substance electrolyte component) For example, various water, acetonitrile,
A solvent dissolved in a solvent such as ethylene carbonate, propylene carbonate, or polyethylene glycol (or a mixed solvent thereof) can be used. Among these, an iodine solution (I / I ₃ system solution) is particularly preferably used as the electrolyte solution 81. More specifically, the electrolyte solution 81 is, for example, a solution obtained by dissolving iodine and potassium iodide in ethylene glycol, dimethylhexylimidazolium, iodine and lithium iodide in a predetermined amount.
A solution of Tertiary-butylpyridine dissolved in acetonitrile, Iodolyte TG50 (Solaroni
cs), 1,2-dimethyl-3-propylimidazolium iodide and the like.

The concentration (content) of the electrolyte component in the electrolyte solution 81 is not particularly limited.
２５25 wt%, preferably 0.5-15 w
It is more preferably about t%.

The amount of the electrolyte solution 81 is not particularly limited. For example, the dimensions of the solar cell 1D to be manufactured,
It can be set appropriately according to the concentration of the electrolyte component in the electrolyte solution 81 and the like.

In such a solar cell 1D, the light receiving layer 40
Then, when light enters, electrons are excited in the light receiving layer 40 to generate electrons and holes.

Then, the electrons are collected on the counter electrode second electrode 50 via the first electrode 30, the current collector 100 (the thin metal wire 110), the connection portion 120, and the external circuit 900.
When the iodine solution is used as the electrolyte solution 81, the electrons reduce iodine in the electrolyte solution 81 to form I ⁻ .

[0221] The I ^- (reductant) is then diffused in the electrolyte solution 81, reaches the surface (light receiving surface) of the light-receiving layer 40,
Electrons are deprived (oxidized) by holes remaining on the surface of the light-receiving layer 40 to be in an I ₃ ⁻ (oxidized form). This completes the current loop.

[0222] Incidentally, I ₃ ^- is a middle electrolyte solution 81 diffuses moved back to the second electrode 50, repeated action of being reduced gotten electrons.

Thus, in the solar cell 1D, the current collector 1
By installing 10 so as to be in contact with the first electrode 30, even when the size is increased, as in the first embodiment,
It is possible to suppress (prevent) an increase in electric resistance due to an increase in the area of the first electrode 30, and to appropriately prevent a decrease in power generation efficiency.

Such a solar cell 1D can be manufactured, for example, as follows. First, a first substrate 20 and a second substrate 70 made of, for example, quartz glass or the like are prepared. For the first substrate 20 and the second substrate 70, those having a uniform thickness and no bending are preferably used.

<0 ′> First, the current collector 100 (each thin metal wire 110) and the connection portion 120 are formed on the upper surface of the first substrate 20.

This is the same as the current collector 10 of the first embodiment.
It can be formed in the same manner as (the thin metal wires 11) and the connection portion 12.

<1 ′> Next, the first electrode 30 is placed on the upper surface of the first substrate 20 so as to cover the current collector 100.
The second electrode 50 is provided on the upper surface of the second substrate 70, respectively.
Form.

The first electrode 30 can be formed by using a material of the first electrode 30 made of, for example, ITO or the like by using, for example, an evaporation method, a sputtering method, a printing method, or the like.

The material of the second electrode 50 made of, for example, platinum or the like is formed by, for example, a vapor deposition method.
It can be formed by using a sputtering method, a printing method, or the like.

<2 ′> Next, the light receiving layer 40 is formed on the upper surface of the first electrode 30. This can be formed in the same manner as the light receiving layer 4 of the first embodiment.

<3 ′> Next, an electrolyte solution 81 is sealed between the light receiving layer 40 and the second electrode 50, and the solar cell 10
To complete.

First, the outer edge (periphery) of the light receiving layer 40 is surrounded by the material of the wall portion 90 made of, for example, polycarbonate, and then an electrolyte solution 81 such as an iodine solution is supplied into the inside.

Next, the first substrate 20 and the second substrate 70 are arranged and laminated so that the light receiving layer 40 and the second electrode 50 face each other, and the electrolyte solution 81 is sealed. Thereafter, the material of the wall portion 90 is solidified (hardened). Through the steps described above, solar cell 1D is manufactured.

In the present embodiment, the wall portion 90 is configured to cover the entire circumference of the light receiving layer 40 and the electrolyte solution 81 (electrolyte).
May be arranged around the light receiving layer 40 and the electrolyte solution 81 at predetermined intervals, and the gap may be sealed with a sealing member.

As the electrolyte, a solid electrolyte or a gel electrolyte can be used in place of the electrolyte solution (liquid electrolyte) 81.

As described above, the solar cell of the present invention has been described based on the illustrated embodiments, but the present invention is not limited to these embodiments. Each component constituting the solar cell can be replaced with an arbitrary component having the same function.

In the solar cell of the present invention, a barrier layer having a function of preventing or suppressing the counter electrode or the electrolyte from contacting the surface electrode may be provided between the surface electrode and the light receiving layer.

Further, in the solar cell of the present invention, the light incident direction may be from the opposite direction, different from the illustrated one.

The solar cell of the present invention has the first
In the fourth embodiment, any two or more configurations may be combined.

[0240]

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

Example 1 A solar cell shown in FIG. 1 was manufactured as follows.

First, dimensions: 300 mm long × 310 mm wide
X A quartz glass substrate having a thickness of 1.0 mm was prepared. next,
The quartz glass substrate was immersed in a cleaning liquid (a mixed liquid of sulfuric acid and hydrogen peroxide solution) at 85 ° C. to perform cleaning and clean the surface.

-0- On the top surface of this quartz glass substrate, by vapor deposition method, dimensions: width 2 μm × height 1 μm × length 300
mm fine aluminum wire (current collector), each interval is 5mm
Was formed so as to be almost parallel.

Further, continuously, the size is 300 m in length.
An aluminum film (connection site) having a size of mx 10 mm in width x 1 µm in thickness was formed.

-1- Next, the upper surface of the quartz glass substrate is covered with the aluminum fine wire, and the I: 300 mm × 300 mm × 1.3 μm thick is deposited by vapor deposition.
A TO electrode (first electrode) was formed.

-2- Next, on the upper surface of the formed ITO electrode, dimensions: 300 mm long × 300 mm wide × 10 μm thick
Was formed. This was performed as follows.

[Preparation of Titanium Oxide Powder] Titanium oxide powder comprising 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 mixing ratio of the rutile type titanium dioxide powder and the anatase type titanium dioxide powder was 60:40 by weight.

[Preparation of coating liquid (light-receiving layer material)] First, 50 g of the prepared titanium oxide powder was suspended in 100 mL of distilled water.

Next, nitric acid (stabilizer) 5 was added to the suspension.
0 mL was added and kneaded sufficiently in an agate mortar.

Next, 100 mL of distilled water was added to the suspension.
And further kneaded. By the addition of distilled water, the mixing ratio of nitric acid and water was finally adjusted to 20:80 (volume ratio). At this time, the viscosity of the suspension was 5
cP.

Next, a nonionic surfactant ("Triton-X100", manufactured by ICN Biomedical) was added to the suspension to a final concentration of 3% by weight and kneaded. Thus, a coating liquid (light-receiving layer material) was prepared.

[Formation of Light-Receiving Layer] A light-receiving layer material was applied on the upper surface of the ITO electrode by dipping (coating method).
Firing (heat treatment) was performed at a temperature of 300 ° C. for 2 hours to obtain a film.

Next, the laminated body of the quartz glass substrate, the thin aluminum wire, the ITO electrode and the film is immersed in ethanol in which carbon black (inorganic pigment) is suspended, taken out of the suspension, and naturally dried. The ethanol was evaporated. Furthermore, after drying in a clean oven at 80 ° C. for 0.5 hour, it was left overnight. Thus, a light receiving layer on which carbon black was adsorbed was obtained.

The light-receiving layer thus obtained has a porosity of 32.
%, And the surface roughness Ra of the light receiving surface was 0.44 μm.

-3- Then, a laminated body of the quartz glass substrate, the thin aluminum wires, the aluminum film, the ITO electrode and the light-receiving layer was placed on a hot plate heated to 80 ° C., and a CuI acetonitrile solution was (Material of the second electrode) was dropped and dried. This operation was repeated to form a CuI electrode (second electrode) having a size of 300 mm long × 300 mm wide × 30 μm thick.

Incidentally, tetrapropylammonium iodide was added to the acetonitrile solution so as to be 10 ⁻³ wt%.

-4- Next, a platinum electrode (third electrode) having a size of 300 mm long × 300 mm wide × 0.1 mm thick was formed on the upper surface of the CuI electrode by vapor deposition.

Example 2 A solar cell as shown in FIG. 5 was manufactured in the same manner as in Example 1 except that aluminum thin wires were arranged in a lattice.

The light-receiving layer thus obtained has a porosity of 30.
%, And the surface roughness Ra of the light receiving surface was 0.40 μm.

Example 3 A solar cell shown in FIG. 6 was manufactured in the same manner as in Example 1 except that the thin aluminum wires were embedded in the light receiving layer.

The obtained light receiving layer has a porosity of 32.
%, And the surface roughness Ra of the light receiving surface was 0.42 μm.

Example 4 A solar cell shown in FIG. 7 was manufactured as follows.

First, dimensions: length 300 mm × width 310 mm
X Two quartz glass substrates (first substrate and second substrate) having a thickness of 1.0 mm were prepared. Next, these quartz glass substrates were immersed in a cleaning liquid (a mixed liquid of sulfuric acid and hydrogen peroxide solution) at 85 ° C. to perform cleaning, and the surfaces thereof were cleaned.

-0'- An aluminum thin wire (current collector) having a size of 2 μm in width × 1 μm in height × 300 mm in length is formed on the upper surface of the quartz glass substrate by vapor deposition at intervals of 5 mm to be substantially parallel. Pattern.

In addition, continuously, the size: 300 m in length
An aluminum film (connection site) having a size of mx 10 mm in width x 1 µm in thickness was formed.

-1'- Next, the upper surface of the quartz glass substrate is covered with the aluminum fine wire,
Dimensions: 300 mm long × 300 mm wide × 1.3 μm thick ITO electrode (first electrode), and on the upper surface of the other quartz glass substrate by vapor deposition method, dimensions: 300 mm long × 310 mm wide × 1 μm thick (A second electrode) was formed.

-2'- Next, on the upper surface of the formed ITO electrode, dimensions: 290 mm (length) × 290 mm (width) × 10 μm (thickness)
m light-receiving layers were formed. This was performed in the same manner as in Example 1.

The obtained light-receiving layer had a porosity of 33.
%, And the surface roughness Ra of the light receiving surface was 0.45 μm.

-3'- The periphery of the light-receiving layer was surrounded by polycarbonate (wall material), and the inside was filled with an iodine solution (electrolyte solution).

The iodine solution was prepared by dissolving iodine and lithium iodide (electrolyte component) in ethylene glycol so as to be 0.6 wt% and 3.5 wt%, respectively.

Next, the quartz glass substrates were arranged and laminated so that the light-receiving layer and the platinum electrode faced each other, and then the polycarbonate was solidified.

(Comparative Example 1) A solar cell was manufactured in the same manner as in Example 1 except that the current collector was omitted.

The obtained light-receiving layer had a porosity of 32.
%, And the surface roughness Ra of the light receiving surface was 0.44 μm.

(Comparative Example 2) A solar cell was manufactured in the same manner as in Example 4 except that the current collector was omitted.

The light-receiving layer thus obtained has a porosity of 33.
%, And the surface roughness Ra of the light receiving surface was 0.45 μm.

(Evaluation) Examples 1-4 and Comparative Examples 1 and 2
Each of the solar cells manufactured in 2) was irradiated with light from an artificial sun lamp, and the photoelectric conversion efficiency at this time was measured. The incident angles of light to the light receiving layer were set to 90 ° and 52 °, and the photoelectric conversion efficiency when the incident angle of light was 90 ° was R _90.
And then, the photoelectric conversion efficiency at 52 ° was R _52. Table 1 shows the results of this evaluation.

[0277]

[Table 1]

From the results shown in Table 1, the solar cell of the present invention in which the current collector was placed in contact with the ITO electrode (Examples 1 to 3)
In each of 4), the photoelectric conversion efficiency was excellent.

On the other hand, in Comparative Example 1 where the current collector was omitted,
In each of the solar cells of No. 2, the photoelectric conversion efficiency was inferior. This is considered to be due to an increase in electric resistance accompanying an increase in the area of the ITO electrode.

The solar cell of the present invention (Examples 1 to 4)
In each case, R ₅₂ / R ₉₀ was 0.85 or more, which indicated that the solar cell of the present invention had lower directivity to light.

[0281]

As described above, according to the solar cell of the present invention, since the current collector in contact with the surface electrode is provided to improve the conductivity of the entire surface electrode, the solar cell is generated in the light receiving layer. Electrons can be efficiently extracted, and as a result, excellent photoelectric conversion efficiency can be obtained.

The above effect can be further improved by appropriately setting the ratio of the area occupied by the current collector to the entire surface electrode when viewed from the direction perpendicular to the surface electrode.

Further, by forming the current collector with a plurality of linear bodies and disposing them substantially in parallel or in a grid and at substantially equal intervals, the conductivity of the plane electrode can be made uniform. The effect can be further improved. Further, the solar cell of the present invention is easy to manufacture and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of a solar cell (photovoltaic cell: photoelectric conversion element) of the present invention.

FIG. 2 shows a light-receiving layer and a second layer in the solar cell of the first embodiment.
FIG. 3 is an enlarged view showing a cross section near the interface of the electrode of FIG.

FIG. 3 is an enlarged view showing a cross section near a light receiving surface of a light receiving layer in the solar cell of the first embodiment.

FIG. 4 is a diagram showing an equivalent circuit of the solar cell circuit shown in FIG.

FIG. 5 is a partial sectional view showing a second embodiment of the solar cell of the present invention.

FIG. 6 is a partial sectional view showing a third embodiment of the solar cell of the present invention.

FIG. 7 is a partial sectional view showing a fourth embodiment of the solar cell of the present invention.

FIG. 8 is an enlarged view showing a cross section near a light receiving surface of a light receiving layer in a solar cell according to a fourth embodiment.

[Explanation of symbols]

 1A to 1C solar cell 2 substrate 3 first electrode 4 light receiving layer 41 hole 5 second electrode 6 third electrode 10 current collector 11 linear body 12 connection site 1D solar cell 20 first substrate 30 first Electrode 40 Light receiving layer 401 Hole 50 Second electrode 70 Second substrate 80 Storage space 81 Electrolyte solution 90 Wall part 100 Current collector 110 Linear body 120 Connection part 800 Diode 900 External circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F051 AA14 FA04 FA06 FA14 5H032 AA06 AS16 CC13 CC14 CC16 EE00 EE02 EE03 EE07 EE18 HH00 HH01 HH04

Claims (33)

[Claims] 1. A porous light-receiving layer mainly composed of titanium oxide; a surface electrode provided on the light-receiving surface side of the light-receiving layer so as to cover the light-receiving surface; A current collector having a surface electrode and a counter electrode disposed opposite to the surface electrode, and a current collector made of a material having a lower electric resistance than the material of the surface electrode is disposed so as to be in contact with the surface electrode. A solar cell characterized in that it is configured to improve the conductivity of the solar cell. 2. When viewed from a direction perpendicular to the plane electrode,
The solar cell according to claim 1, wherein a ratio of an area occupied by the current collector to an area of the entire surface electrode is 0.01% to 10%. 3. The solar cell according to claim 1, wherein the current collector includes a plurality of linear bodies. 4. The solar cell according to claim 3, wherein each of said linear bodies is disposed substantially in parallel. 5. The solar cell according to claim 3, wherein the linear members are arranged in a grid. 6. The solar cell according to claim 3, wherein the linear bodies are disposed at substantially equal intervals. 7. The solar cell according to claim 6, wherein the interval is 1 to 10 mm. 8. The linear body has an average width of 1 to 100 μm.
The solar cell according to claim 3, wherein 9. The linear body has an average height of 0.5 to 50.
The solar cell according to any one of claims 3 to 8, wherein the thickness is μm. 10. The solar cell according to claim 3, wherein the linear body is a thin metal wire. 11. The current collector has a conductivity of 1 × 10 ³ S.
The solar cell according to any one of claims 1 to 10, which is not less than / m. 12. The solar cell according to claim 1, wherein the current collector is installed so as to be embedded in the surface electrode. 13. The solar cell according to claim 1, wherein the current collector is provided so as to be embedded in the light receiving layer. 14. The solar cell according to claim 1, further comprising a connection portion formed continuously with the current collector and connecting an external circuit. 15. The solar cell according to claim 1, wherein the titanium oxide is mainly composed of titanium dioxide. 16. The light-receiving layer has an average particle diameter of 1 nm to 1 nm.
The solar cell according to any one of claims 1 to 15, wherein the solar cell is manufactured using a titanium oxide powder of μm. 17. The solar cell according to claim 1, wherein the light receiving layer has a porosity of 5 to 90%. 18. The light-receiving layer has a surface roughness Ra of 5 nm.
The solar cell according to any one of claims 1 to 17, which has a thickness of 10 to 10 µm. 19. The solar cell according to claim 1, wherein said light receiving layer is in the form of a film. 20. The light-receiving layer has an average thickness of 0.1 to 3
The solar cell according to claim 19, which has a thickness of 00 µm. 21. The solar cell according to claim 1, wherein a rectifying barrier is formed at an interface between the light receiving layer and the counter electrode. 22. The solar cell according to claim 21, wherein the counter electrode is made of a material having ion conduction characteristics. 23. The substance having ion conduction properties,
23. The solar cell according to claim 22, which is a metal halide compound. 24. The solar cell according to claim 23, wherein the metal halide compound is a metal iodide compound. 25. The counter electrode according to claim 22, wherein the counter electrode is formed by applying a counter electrode material obtained by dissolving the substance having the ion conduction property in a solvent on the light receiving layer by a coating method. The solar cell according to any one of the above. 26. The solar cell according to claim 25, wherein the counter electrode material is applied on the light receiving layer while heating the light receiving layer. 27. The counter electrode material contains a substance that suppresses an increase in crystal size when the substance having the ion conduction property is crystallized.
The solar cell according to 1. 28. The solar cell according to claim 27, wherein said substance is a halide. 29. The solar cell according to claim 28, wherein the halide is an ammonium halide. 30. Content of the substance in the counter electrode material
The quantity is 10^-Four-10 ^-128 or 2% by weight.
10. The solar cell according to 9. 31. The solar cell according to claim 1, wherein an electrolyte is provided between the light receiving layer and the counter electrode. 32. The solar cell according to claim 31, wherein a wall member is provided around the light receiving layer and the electrolyte. 33. When the incident angle of light on the light receiving layer is 90 °
The photoelectric conversion efficiency of R ₉₀Light at an incident angle of 52 °
The conversion efficiency is R₅₂And R₅₂/ R₉₀Is 0.8 or more
The solar cell according to any one of claims 1 to 32, wherein
pond.