JP2004228449A - Photoelectric conversion element - Google Patents

Abstract

An object of the present invention is to provide a photoelectric conversion element capable of obtaining sufficient photoelectric conversion efficiency even in a case where the size is increased.
The photoelectric conversion element includes a first electrode (a surface electrode) provided on a substrate, a second electrode (a counter electrode) provided to face the first electrode, and a first electrode. A dense layer located between the first electrode and the second electrode, a porous layer in contact with the dense layer, a dye layer in contact with the porous layer, and a second electrode located between the porous layer and the second electrode. And a current collector 7 having a hole transport layer in contact with the dye layer, and made of a material having a lower electric resistance than the constituent material of the first electrode, provided so as to be in contact with the first electrode, The first electrode is configured to improve conductivity. The current collector 7 includes three types of linear bodies (a first linear body 7a, a second linear body 7b, and a third linear body 7c) having different widths, and these are connected to each other. ing.
[Selection diagram] FIG.

Description

【０１３６】
表１に示すように、実施例１、２で製造した光電変換素子（本発明の光電変換素子）は、いずれも、同一幅の線状体で構成した集電体を備える光電変換素子（比較例２〜４の光電変換素子）と比較して、大面積化に伴う光電変換効率の低下が少ないものであることが明らかとなった。
【図面の簡単な説明】
【図１】本発明の光電変換素子の第１実施形態を示す斜視図である。
【図２】図１中のＡ−Ａ線断面図である。
【図３】図１に示す光電変換素子が備える集電体７の構成を示す平面図である。
【図４】光電変換素子の製造方法に用いられる液滴吐出装置を模式的に示す図である。
【図５】本発明の光電変換素子の第２実施形態を示す縦断面図である。
【図６】図５に示す光電変換素子が備える集電体７の構成を示す平面図である。
【符号の説明】
１……光電変換素子 ２……基板 ３……第１の電極 ４……電子輸送層 ４１……緻密質層 ４２……多孔質層 ４２１……空孔 ５……正孔輸送層 ６……第２の電極 ７……集電体 ７ａ……第１の線状体 ７ｂ……第２の線状体 ７ｃ……第３の線状体 ７１……電気接続部 ８……外部回路 Ｄ……色素層 １０……液滴吐出装置 ２０……載置テーブル ３０……Ｘ軸駆動ローラ ４０……ノズル ５０……液滴吐出ヘッド ６０……Ｙ軸駆動機構 ７０……液滴[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photoelectric conversion element.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a wet or dry dye-sensitized solar cell has been proposed as a solar cell (photoelectric conversion element) that can be manufactured at low cost using inexpensive materials without requiring large-scale facilities.
These dye-sensitized solar cells have a configuration in which a semiconductor carrying a dye is provided between a transparent electrode and a counter electrode, and electrons and holes generated in the dye by light reception face the transparent electrode, respectively. And an electrode, and a potential difference is generated between them.
[0003]
However, since the transparent electrode is usually composed of a transparent conductive oxide having relatively high electric resistance, when the size of the dye-sensitized solar cell is increased, the area of the transparent electrode increases (increase in area). As a result, there is a problem that the electric resistance increases, and as a result, the photoelectric conversion efficiency decreases.
In order to solve such a problem, a dye-sensitized solar cell in which a current collector made of a material having a lower electric resistance than the constituent material of the transparent electrode is installed so as to be in contact with the transparent electrode, and the conductivity of the entire transparent electrode is improved. A battery has been proposed (for example, see Patent Document 1).
In the dye-sensitized solar cell described in Patent Literature 1, although a reduction in photoelectric conversion efficiency due to an increase in size can be suppressed, development of a configuration capable of further suppressing a reduction in photoelectric conversion efficiency has been demanded. I have.
[0004]
[Patent Document 1]
JP 2002-314108 A
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a photoelectric conversion element that can obtain sufficient photoelectric conversion efficiency even when the size is increased.
[0006]
[Means for Solving the Problems]
Such an object is achieved by the present invention described below.
The photoelectric conversion element of the present invention, a surface electrode provided on a substrate,
A counter electrode provided to face the surface electrode;
Located between the surface electrode and the counter electrode, at least a portion of a porous electron transport layer,
A dye layer in contact with the electron transport layer;
A hole transporting layer located between the electron transporting layer and the counter electrode, and in contact with the dye layer;
A photoelectric conversion element configured to provide a current collector made of a material having a lower electric resistance than the constituent material of the surface electrode, so as to be in contact with the surface electrode, and to improve the conductivity of the entire surface electrode,
The current collector is connected to the first linear body and the first linear body so as to branch or intersect with the first linear body, and has a width smaller than that of the first linear body. And a second linear body.
Thereby, sufficient photoelectric conversion efficiency can be obtained even when the size is increased.
[0007]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that the second linear member connects the different first linear members.
Thereby, even when a part of the current collector is disconnected, electrons can be taken out to an external circuit via another path that is not disconnected.
[0008]
In the photoelectric conversion element of the present invention, when the width (average) of the first linear body is A [mm] and the width (average) of the second linear body is B [mm], A / B is preferably 1 to 100.
This allows the current collector to more efficiently extract electrons from each part of the surface electrode.
[0009]
In the photoelectric conversion element according to the aspect of the invention, the current collector is connected to the second linear body so as to branch or intersect with the second linear body, and has a smaller width than the second linear body. Preferably, a third linear body is provided.
Thus, the current collector can efficiently extract electrons from a wide portion of the surface electrode.
[0010]
In the photoelectric conversion element according to the aspect of the invention, the third linear body connects the first linear body and the second linear body, or connects the different second linear bodies to each other. Is preferred.
Thereby, even when a part of the current collector is disconnected, electrons can be taken out to an external circuit via another path that is not disconnected.
[0011]
In the photoelectric conversion element of the present invention, when the width (average) of the second linear body is B [mm] and the width (average) of the third linear body is C [mm], B / C is preferably 1 to 100.
This allows the current collector to more efficiently extract electrons from each part of the surface electrode.
[0012]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that at least the first linear body is arranged in a lattice.
Thus, the current collector can uniformly extract electrons from the surface electrode.
[0013]
In the photoelectric conversion element of the present invention, it is preferable that at least the first linear body is arranged in a honeycomb shape.
Thus, when a flexible substrate is used as the substrate, the current collector can function as a reinforcing material for the substrate.
[0014]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that the current collector is provided so that at least a part thereof is embedded in the surface electrode.
Thereby, electrons can be more efficiently extracted from the current collector 7 and the surface electrode.
[0015]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that at least a part of the current collector is provided to be embedded in the substrate.
Accordingly, unevenness generated on the upper surface of the substrate can be reduced, so that poor connection between the current collector and the surface electrode can be more reliably prevented.
[0016]
In the photoelectric conversion element of the present invention, the substrate is mainly formed of a resin material,
It is preferable that the current collector is provided so that at least a part of the current collector is embedded in the substrate by subjecting the substrate on which the current collector is formed to hot pressing.
Thus, the current collector can be relatively easily embedded in the substrate.
[0017]
In the photoelectric conversion element according to the aspect of the invention, the substrate provided so that at least a part of the current collector is embedded therein may be configured such that the current collector is formed on a sheet material mainly including a precursor of a thermosetting resin. After formation, it is preferable that the current collector be obtained by subjecting the sheet material on which the current collector is formed to a heat press treatment.
Thus, the current collector can be relatively easily embedded in the substrate, and the surface shapes of the substrate and the current collector can be made smoother.
[0018]
In the photoelectric conversion element of the present invention, it is preferable that the current collector has an average height of 0.2 mm or less.
Thus, the thickness of the photoelectric conversion element can be further reduced.
[0019]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that a ratio of an area occupied by the current collector to an entire area of the surface electrode be 0.01 to 30% when viewed from a direction perpendicular to the surface electrode.
Thus, the conductivity of the entire surface electrode can be further improved, and a decrease in the light arrival rate to the dye layer can be suitably prevented.
[0020]
In the photoelectric conversion device according to the aspect of the invention, it is preferable that the minimum units of the region surrounded by the current collector have substantially the same area.
This allows the current collector to more uniformly extract electrons from the surface electrode.
[0021]
In the photoelectric conversion device according to the aspect of the invention, it is preferable that the minimum units of the region surrounded by the current collector have substantially the same shape.
This allows the current collector to more uniformly extract electrons from the surface electrode.
[0022]
In the photoelectric conversion element according to the aspect of the invention, it is preferable that the current collector is formed using an inkjet method.
Thus, the current collector can be formed easily and with high accuracy without requiring large-scale equipment.
[0023]
In the photoelectric conversion element of the present invention, it is preferable that the substrate is a flexible substrate mainly composed of a resin material.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a photoelectric conversion element of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<First embodiment>
First, a first embodiment of the photoelectric conversion element of the present invention will be described.
[0025]
FIG. 1 is a perspective view showing a first embodiment of the photoelectric conversion element of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a current collector provided in the photoelectric conversion element shown in FIG. FIG. 3 is a plan view showing a configuration of a body 7. In the following description, the upper side of the paper in FIGS. 1 and 2 is referred to as “upper” or “upper”, the lower side is referred to as “lower” or “lower”, and the upper side of each layer (each member) is referred to. The “upper surface” and the lower surface are referred to as “lower surface”.
[0026]
The photoelectric conversion element 1 shown in FIG. 1 does not require an electrolyte solution, and is a so-called dry photoelectric conversion element. The photoelectric conversion element 1 includes a substrate 2, a current collector 7, a first electrode (plane electrode) 3, a dense layer (dense electron transport layer) 41, and a porous layer (porous electron transport layer). Transport layer) 42, dye layer D, hole transport layer 5, and second electrode (counter electrode) 6. Hereinafter, the configuration of each layer (each part) will be described.
The substrate 2 supports the first electrode 3, the current collector 7, the dense layer 41, the porous layer 42, the dye layer D, the hole transport layer 5, and the second electrode 6. The substrate 2 is formed of a flat (or layered) member.
[0027]
In the photoelectric conversion element 1 of the present embodiment, as shown in FIGS. 1 and 2, for example, light such as sunlight (hereinafter, simply referred to as “light”) from the substrate 2 and a first electrode 3 described later. ) Is 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 dye layer D described later.
[0028]
Examples of the constituent material of the substrate 2 include various glass materials, various ceramic materials, various resin materials such as polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI), and polyethylene naphthalate (PEN). Can be Further, the substrate 2 may be formed of a single layer or a multilayer of a plurality of layers.
[0029]
The average thickness of the substrate 2 is appropriately set depending on 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 hard, the average thickness is preferably about 0.1 to 1.5 mm, and more preferably about 0.8 to 1.2 mm. When the substrate 2 has flexibility (flexibility) (a flexible substrate mainly composed of a resin material), the average thickness is preferably about 0.5 to 150 μm, More preferably, it is about 10 to 75 μm.
When the photoelectric conversion element 1 is mounted on various electronic devices, the components of the electronic device can be used as the substrate 2 of the photoelectric conversion element 1.
[0030]
On the upper surface of the substrate 2, a layered first electrode (plane electrode) 3 is provided.
The constituent material of the first electrode 3 is, for example, indium tin oxide (ITO), tin oxide (FTO) doped with fluorine, indium oxide (IO), tin oxide (SnO).₂), And various metal oxides (transparent conductive oxides) can be used, and one or more of these can be used in combination.
The average thickness of the first electrode 3 is preferably about 0.05 to 5 μm, and more preferably about 0.1 to 1.5 μm.
[0031]
As shown in FIG. 3, a current collector 7 is provided on the upper surface of the substrate 2 so as to contact the first electrode 3. The current collector 7 includes linear bodies (thin metal wires) 7a to 7c having a plurality of types (three types in the present embodiment) of which widths, and an electric connection part 71 is connected to a part thereof. In the present embodiment, the current collector 7 is provided so as to be embedded in the first electrode 3. The electrical connection 71 is exposed to the outside of the photoelectric conversion element 1, and the external circuit 8 is connected to the electrical connection 71.
[0032]
The current collector 7 is made of a material having lower electric resistance than the constituent material of the first electrode 3. The electrons generated in the dye layer D and transported through the electron transport layer 4 can be captured by the first electrode 3 and transmitted to the external circuit 8 through the inside of the first electrode 3. 7, the electric current is transferred to the current collector 7 (each of the linear bodies 7 a to 7 c) having a smaller electric resistance and transmitted to the external circuit 8. That is, the current collector 7 functions as a bypass line for the electrons captured by the first electrode 3, whereby the conductivity of the entire first electrode 3 can be improved.
[0033]
Here, if the current collector 7 is not provided in the photoelectric conversion element, if the area of each layer of the photoelectric conversion element is increased with the enlargement of the photoelectric conversion element, the transparent conductive oxide as described above (this In particular, the first electrode 3 composed of (i.e., has a relatively large electrical resistance) the electrical resistance increases, and as a result, the power generation efficiency (photoelectric conversion efficiency) of the photoelectric conversion element decreases.
[0034]
On the other hand, in the present invention, by providing the current collector 7 so as to be in contact with the first electrode 3, even when the photoelectric conversion element 1 is enlarged, the current collector 7 is provided via the current collector 7 even when the photoelectric conversion element 1 is enlarged. Electrons can be efficiently extracted to the external circuit 8, and as a result, a decrease in the photoelectric conversion efficiency of the photoelectric conversion element 1 can be suitably prevented.
In particular, by providing (buried) the current collector 7 so as to be embedded in the first electrode 3, the contact area between the first electrode 3 and the current collector 7 can be increased. The electric body 7 can extract electrons from the first electrode 3 more efficiently.
[0035]
Examples of the constituent material of the current collector 7 include various metal materials such as aluminum, nickel, cobalt, platinum, palladium, silver, gold, copper, molybdenum, titanium, tantalum, and alloys containing these, carbon, and carbon. Examples include various carbon materials such as nanotubes and fullerenes, and one or more of these materials can be used in combination.
In particular, the present invention is characterized by the configuration of the current collector 7. This point (feature) will be described later in detail.
[0036]
An electron transport layer 4 is provided on the upper surface of the first electrode 3. That is, the electron transport layer 4 is located between the first electrode 3 and a second electrode 6 described later. In the present embodiment, the electron transport layer 4 is provided on the dense layer 41 provided on the first electrode 3 side and on the upper surface of the dense layer 41 so as to be in contact with the dense layer 41. And a porous layer 42. The electron transport layer 4 has a function of capturing and transporting electrons generated in the dye layer D described later.
[0037]
The constituent material of the electron transport layer 4 is, for example, titanium dioxide (TiO 2).₂), Titanium monoxide (TiO), dititanium trioxide (Ti₂O₃), Zinc oxide (ZnO), tin oxide (SnO)₂), SrTiO₃, SiO₂, Al₂O₃, SnO₂Such as oxides, carbides such as TiC and SiC, Si₃N₄, B₄Various n-type semiconductor materials such as nitrides such as N and BN, sulfides such as CdS, and selenides such as CdSe can be used, and one or more of these can be used in combination. it can. Among them, it is preferable to use titanium oxide (particularly, titanium dioxide) as a constituent material of the electron transport layer 4. That is, the electron transport layer 4 is preferably made of titanium dioxide as a main material.
[0038]
Titanium dioxide is particularly excellent in the ability to transport electrons. In addition, titanium dioxide has high sensitivity to light, and by forming the electron transport layer 4 using titanium dioxide as a main material, the electron transport layer 4 itself can generate electrons. Thereby, the photoelectric conversion efficiency (power generation efficiency) of the photoelectric conversion element 1 can be further improved.
In addition, since titanium dioxide has a stable crystal structure, the electron transport layer 4 containing titanium dioxide as a main material is stable with little aging (deterioration) even when exposed to a severe environment. This has the advantage that performance can be obtained over a long period of time.
[0039]
Further, as titanium dioxide, anatase type titanium dioxide, rutile type titanium dioxide, or a mixture thereof can be used. When a mixture of anatase-type titanium dioxide and rutile-type titanium dioxide is used as the titanium dioxide, the mixing ratio thereof is not particularly limited, but is preferably about 95: 5 to 5:95 by weight. More preferably, it is more preferably about 80:20 to 20:80.
[0040]
The porosity of the dense layer 41 is set smaller than the porosity of the porous layer 42. The dense layer 41 has a function of preventing or suppressing contact between a hole transport layer 5 described below and the first electrode 3. By providing the dense layer 41, it is possible to prevent the photoelectric conversion efficiency (energy conversion efficiency) of the photoelectric conversion element 1 from decreasing.
[0041]
On the other hand, the porosity of the porous layer 42 is set to be relatively large, and has a plurality of holes 421 as shown in FIG. The porous layer 42 is provided so as to be in contact with the dye layer D, as will be described later. By forming the porous layer 42 into a shape having a plurality of holes 421, the dye layer D 42 and the inner surface of the hole 421.
[0042]
Therefore, a sufficient contact area between the dye layer D and the porous layer 42 can be ensured. Thereby, the electrons generated in the dye layer D can be more efficiently transmitted to the electron transport layer 4. Further, the light that has entered the porous layer 42 enters the inside of the porous layer 42 and transmits through the porous layer 42 or is reflected (arbitrarily reflected, diffused, or the like) in an arbitrary direction within the hole 421, The dye in the dye layer D is absorbed with a higher probability, and electrons and holes are more efficiently generated in the dye layer D. Thus, the photoelectric conversion efficiency (energy conversion efficiency) of the photoelectric conversion element 1 can be further improved.
[0043]
From the viewpoint of allowing the dense layer 41 and the porous layer 42 to exhibit their functions, respectively, it is preferable to set the conditions of the dense layer 41 and the porous layer 42 as follows.
When the porosity of the dense layer 41 is A [%] and the porosity of the porous layer 42 is B [%], B / A is preferably 1.1 or more, and more preferably 5 or more. More preferably, it is more preferably 10 or more.
Specifically, the porosity A of the dense layer 41 is preferably less than 20%, more preferably less than 5%, and even more preferably less than 2%. On the other hand, the content of the porous layer 42 is preferably 20% or more, more preferably about 20 to 50%, and still more preferably about 20 to 40%.
[0044]
The ratio of the thickness of the dense layer 41 to the thickness of the porous layer 42 is not particularly limited, but is preferably about 1:99 to 60:40, and is preferably about 10:90 to 40:60. More preferred.
Specifically, the average thickness of the dense layer 41 is preferably about 0.01 to 10 μm, and more preferably about 0.1 to 5 μm. On the other hand, the average thickness of the porous layer 42 is preferably about 0.1 to 300 μm, more preferably about 0.5 to 100 μm, and still more preferably about 1 to 25 μm.
[0045]
The interface between the dense layer 41 and the porous layer 42 is preferably unclear, that is, the dense layer 41 and the porous layer 42 are preferably partially overlapped with each other. Thereby, electrons can be more reliably transmitted from the porous layer 42 to the dense layer 41.
Note that the dense layer 41 may be omitted depending on, for example, the type of a constituent material of the hole transport layer 5 described later. That is, the electron transport layer 4 may be entirely porous, unlike the illustrated configuration in which a part thereof is porous. Further, for example, the electron transport layer 4 may have a configuration in which the dense layer 41 is provided in the middle of the thickness direction.
[0046]
The dye layer D is provided so as to contact the porous layer 42. The dye layer D is mainly composed of a dye, and is formed along the outer surface of the porous layer 42 and the inner surface of the holes 421.
The dye layer D (dye) generates electrons and holes by receiving light. Of these, electrons are transmitted to the electron transport layer 4 and holes are transmitted to the hole transport layer 5 described later.
For this dye, for example, various pigments and various dyes can be used alone or in combination, but the pigment is transferred to the electron transport layer 4 (porous layer 42) in that there is little deterioration (deterioration) with time. It is preferable to use a dye from the viewpoint of excellent adsorbability.
[0047]
Examples of the pigment include phthalocyanine pigments, azo pigments, anthraquinone pigments, azomethine pigments, quinophthalone pigments, isoindoline pigments, nitroso pigments, perinone pigments, quinacridone pigments, perylene pigments, and pyrrolopyrrole pigments Pigments, various organic pigments such as dioxazine pigments, carbon pigments, chromate pigments, sulfide pigments, oxide pigments, hydroxide pigments, ferrocyanide pigments, silicate pigments, Various inorganic pigments such as phosphate pigments and others (for example, cadmium sulfide, cadmium selenide, etc.) are exemplified.
[0048]
As the dye, for example, RuL₂(SCN)₂, RuL₂Cl₂, RuL₂(CN)₂, Rutenium 535-bisTBA (manufactured by Solaronics), [RuL₂(NCS)₂]₂H₂Examples include metal complex dyes such as O, cyan dyes, xanthene dyes, azo dyes, hibiscus dyes, blackberry dyes, raspberry dyes, pomegranate juice dyes, chlorophyll dyes, and the like. Note that L in the above composition formula represents 2,2'-bipyridine or a derivative thereof.
[0049]
On the upper surface of the electron transport layer 4 on which the dye layer D is formed, a layered hole transport layer 5 is provided so as to contact the dye layer D. That is, the hole transport layer 5 is located between the electron transport layer 4 (porous layer 42) and a second electrode 6 described later. The hole transport layer 5 has a function of capturing and transporting holes generated in the dye layer D.
Examples of a constituent material of the hole transport layer 5 include various inorganic p-type semiconductors such as iodides such as CuI and AgI, halides such as bromide such as AgBr, and thiocyanate (rhodanide) such as CuSCN. Materials, various organic p-type semiconductor materials such as triphenyldiamine (monomer, polymer, etc.), polyaniline, polypyrrole, polythiophene, phthalocyanine compound (for example, copper phthalocyanine) or a derivative thereof. Two or more kinds can be used in combination. Among these, as a constituent material of the hole transport layer 5, an inorganic p-type semiconductor material is particularly preferable. That is, the hole transport layer 5 is preferably made mainly of an inorganic p-type semiconductor material. By configuring the hole transport layer 5 with a substance having an inorganic p-type semiconductor material as a main material, the hole transport layer 5 more efficiently captures and transports holes generated in the dye layer D. Will be able to do it. Thereby, the photoelectric conversion efficiency (power generation efficiency) of the photoelectric conversion element 1 can be further improved.
[0050]
The inorganic p-type semiconductor material can be used alone or in combination of two or more of the above compounds. Among them, halides are preferable and iodides are more preferable as the inorganic p-type semiconductor material. Halides (especially iodides) are particularly excellent in hole transporting ability. Therefore, by forming the hole transport layer 5 using iodide as a main material, the photoelectric conversion efficiency of the photoelectric conversion element 1 can be further improved.
Further, as shown in FIG. 2, the hole transport layer 5 is formed by penetrating into the holes 421 of the porous layer 42 on which the dye layer D is formed, and the contact between the dye layer D and the hole transport layer 5 is formed. The area is sufficiently secured. Therefore, holes generated in the dye layer D can be more efficiently transmitted to the hole transport layer 5.
[0051]
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 still more preferably about 10 to 30 μm.
On the upper surface of the hole transport layer 5, a layered second electrode 6 is provided. That is, the second electrode (counter electrode) 6 is provided so as to face the first electrode (plane electrode) 3.
[0052]
As a constituent material of the second electrode 6, for example, various metal materials such as aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum, titanium, tantalum, or alloys containing these, or graphite such as Various carbon materials and the like, and one or more of them can be used in combination. In addition, various transparent conductive oxides can be used as the constituent material of the second electrode 6.
The average thickness of the second electrode 6 is appropriately set depending on the material, use, and the like, and is not particularly limited, but is preferably about 0.01 to 5 μm, and more preferably about 0.03 to 1.5 μm. preferable.
[0053]
When light enters the photoelectric conversion element 1 configured as described above from the substrate 2 side, electrons are mainly excited in the dye layer D (dye), and electrons (e⁻) And holes (h⁺) Occurs. Of these, electrons are transmitted to the electron transport layer 4 and holes are transmitted to the hole transport layer 5, and are transported in each layer. As a result, a potential difference (photoelectromotive force) is generated between the first electrode 3 (electrical connection portion 71) and the second electrode 6. Then, when the first electrode 3 and the second electrode 6 of the photoelectric conversion element 1 are connected by the external circuit 8, a current (photoexcitation current) flows through the external circuit 8.
[0054]
Next, the configuration of the current collector 7 will be described in detail.
As shown in FIGS. 2 and 3, the current collector 7 has three types of linear bodies (first linear bodies 7a) having a substantially semicircular (or semielliptical) cross-sectional shape and different widths from each other. , A second linear body 7b and a third linear body 7c). In the present embodiment, the width (average) of the first linear body 7a is A [mm], the width (average) of the second linear body 7b is B [mm], and the width of the third linear body 7c. When (average) is C [mm], these are set so that A> B> C.
[0055]
As shown in FIG. 3, the second linear member 7b has one end connected to the first linear member 7a so as to branch or intersect with the first linear member 7a, and the other end. Are connected to different first linear bodies 7a. Further, one end of the third linear body 7c is connected to the second linear body 7b so as to branch or cross from the second linear body 7b, and the other end is connected to the first linear body 7b. It is connected to the body 7a. Thus, the current collector 7 has a net shape as a whole.
With such a configuration, the current collector 7 can efficiently extract electrons from a wide portion of the first electrode 3. Further, even when a part of the linear members 7a to 7c is disconnected, there is an advantage that electrons can be taken out to the external circuit 8 via another path which is not disconnected.
[0056]
In the present embodiment, all of the first linear member 7a, the second linear member 7b, and the third linear member 7c are arranged in a lattice. Thus, the current collector 7 can uniformly (without unevenness) extract electrons from the first electrode 3.
In particular, in the present embodiment, the current collector 7 has a minimum unit (a rectangular area in FIG. 3) of a region surrounded by the current collector 7 having substantially the same area and substantially the same shape. It is formed so that it becomes. Thereby, the current collector 7 can more uniformly (evenly) extract electrons from the first electrode 3.
The current collector 7 is preferably formed so that the minimum unit of the region surrounded by the current collector 7 has substantially the same area and substantially the same shape, respectively. It may be formed so as to satisfy only the condition.
[0057]
The relationship between the width (average) A [mm] of the first linear body 7a and the width (average) B [mm] of the second linear body 7b is such that A / B is about 1 to 100 ( In particular, it is preferably about 2 to 10), and the relationship between the width (average) B [mm] of the second linear body 7b and the width (average) C [mm] of the third linear body 7c. It is preferable that B / C is about 1 to 100 (particularly about 2 to 10). Thus, the current collector 7 can more efficiently extract electrons from each part of the first electrode 3.
The width (average) A of the first linear body 7a, the width (average) B of the second linear body 7b, and the width (average) C of the third linear body 7c are, for example, current collection. It is appropriately set according to the resistivity of the body 7, the arrangement density of each linear body (wiring pitch, arrangement shape), and the like.
[0058]
As an example, the sheet resistance of the current collector 7 is 0.1Ω / □, each linear body is formed in a lattice shape, the first linear bodies 7a are spaced by about 10 cm, and the second linear bodies 7b are When arranging the third linear body at an interval of about 5 mm at an interval of about 2 cm,
The width (average) A of the first linear body 7a indicated by Wa in FIG. 3 is preferably about 2 to 30 mm, and more preferably about 5 to 15 mm.
The width (average) B of the second linear member 7b indicated by Wb in FIG. 3 is preferably about 0.4 to 6 mm, and more preferably about 1 to 3 mm.
The width (average) C of the third linear body 7c indicated by Wc in FIG. 3 is preferably about 0.1 to 1.5 mm, and more preferably about 0.2 to 0.6 mm. .
When the arrangement of the linear members is the same as described above and the sheet resistance of the current collector 7 is 1/10, the width of each linear member can be reduced to about 1/10.
[0059]
From the viewpoint of improving the conductivity of the first electrode 3 as a whole, the current collector 7 preferably has an area occupied by the first electrode 3 (formation area) as large as possible. If the area occupied by one of the electrodes 3 is too large, the arrival rate of light to the dye layer D is reduced depending on the constituent material and thickness of the current collector 7. Therefore, there is a suitable range in the area occupied by the current collector 7 with respect to the first electrode 3.
[0060]
Specifically, when viewed from a direction perpendicular to the first electrode 3, the ratio of the area occupied by the current collector 7 to the entire area of the first electrode 3 (distribution density of the current collector 7) is Although it depends on the resistivity of the electric conductor 7 and is not particularly limited, it is preferably about 0.01 to 30%, and more preferably about 1 to 15%. Thus, the conductivity of the entire first electrode 3 can be further improved, and a decrease in the light arrival rate to the dye layer D can be suitably prevented. As a result, the power generation efficiency (photoelectric conversion efficiency) of the photoelectric conversion element 1 can be significantly improved.
Further, the current collector 7 (each of the linear members 7a to 7c) preferably has an average height (H in FIG. 3) of 0.2 mm or less, more preferably 0.1 mm or less, and More preferably, it is about 50 μm. Thereby, the thickness of the photoelectric conversion element 1 can be further reduced.
[0061]
Such a current collector 7 has a conductivity of, for example, 1 × 10³It is preferably about S / m or more, and 1 × 10⁵More preferably, it is about S / m or more. Thereby, the conductivity of the entire first electrode 3 can be further improved.
The cross-sectional shape of each of the linear bodies 7a to 7c is not limited to the illustrated one, and may be, for example, a circle or a polygon such as a triangle, a quadrangle (square, rectangle, rhombus).
Further, the third linear body 7c is not limited to the one that connects the first linear body 7a and the second linear body 7b, and may be, for example, one that connects different second linear bodies 7b. May be included, or may connect the second linear bodies 7b which are all different from each other.
[0062]
Each layer of the photoelectric conversion element 1 (the current collector 7, the electrical connection portion 71, the first electrode 3, the dense layer 41, the porous layer 42, the dye layer D, the hole transport layer 5, and the second electrode 6) is, for example, an inkjet method, a printing method, a vacuum evaporation method, a sputtering method (particularly, a low-temperature sputtering method), a spray pyrolysis method, a jet mold (plasma spraying) method, a CVD method, an electrolytic plating method, and an electroless method. The layers may be formed by appropriately selecting from plating methods and the like, but it is preferable that each of these layers is formed by an inkjet method. According to the inkjet method, each layer can be formed easily and with high precision without requiring large-scale equipment.
[0063]
Hereinafter, a case where each of the above-mentioned layers (each part) is formed using an inkjet method will be described as an example. In this case, for example, a droplet discharge device (inkjet device) as shown in FIG. 4 is used.
The droplet discharge device 10 illustrated in FIG. 4 includes a mounting table 20 on which the substrate 2 is mounted, an x-axis driving roller 30 that moves the mounting table 20 in the x-axis direction (main scanning), and a liquid having a nozzle 40. A droplet discharge head 50 and a y-axis drive mechanism 60 that moves (sub-scans) the droplet discharge head 50 in the y-axis direction are provided.
[0064]
A liquid containing the constituent material of each layer or a precursor thereof is stored in the droplet discharge head 50, and is discharged as a droplet 70 from a small hole formed at the tip of the nozzle 40.
By moving the mounting table 20 in the x-axis direction and reciprocating the droplet discharge head 50 in the y-axis direction, the droplets 70 are discharged from the small holes of the nozzles 40 to form each of the above layers.
[0065]
The viscosity (normal temperature) of the liquid to be used is not particularly limited, but is usually preferably about 3 to 10 cps, more preferably about 4 to 8 cps. By setting the viscosity of the liquid to be used in such a range, it is possible to discharge the droplet 70 from the small hole of the nozzle 40 more stably.
The amount (average) of one droplet 70 is not particularly limited, but is preferably about 5 to 40 pL, and more preferably about 10 to 30 pL. By setting the amount (average) of one droplet 70 in such a range, a more precise shape can be formed.
[0066]
Next, each step of the method for manufacturing the photoelectric conversion element 1 will be sequentially described.
[1] Formation of Current Collector 7 and Electrical Connection 71
First, the substrate 2 is prepared. As the substrate 2, a substrate having a uniform thickness and no bending is preferably used.
The liquid for forming the current collector 7 and the electric connection portion 71 is supplied to the upper surface of the substrate 2 by using an ink-jet method to form the current collector 7 and the electric connection portion 71.
Examples of the liquid for forming the current collector 7 and the electric connection portion 71 include (1): a dispersion (suspension) containing particles composed of various metal materials and various carbon materials, and (2): various metals. A dispersion (suspension) containing particles composed of a metal oxide, which is a precursor of the material, and a reducing agent can be used.
[0067]
In the case of {circle around (1)}, the content of the particles in the liquid for forming the current collector 7 and the electric connection portion 71 varies depending on the type and composition of the dispersion medium and is not particularly limited, but is about 0.1 to 40 wt%. And more preferably about 2 to 20 wt%.
The average particle size of the particles used is not particularly limited, but is preferably about 1 to 30 nm, more preferably about 2 to 10 nm.
[0068]
Further, it is preferable to use particles coated with an aggregation inhibitor (dispersant) for inhibiting aggregation at room temperature. Examples of the aggregation inhibitor include a compound having a group containing a nitrogen atom such as an alkylamine, a compound having a group containing an oxygen atom such as an alkanediol, and a group containing a sulfur atom such as an alkylthiol and an alkanedithiol. And the like.
[0069]
In this case, a removing agent capable of removing the aggregation inhibitor is added to the liquid for forming the current collector 7 and the electric connection portion 71 by a predetermined process (for example, heating). Examples of the removing agent include linear or branched saturated carboxylic acids having 1 to 10 carbon atoms such as formic acid, acetic acid, propionic acid, butanoic acid, hexanoic acid, and octylic acid, acrylic acid, methacrylic acid, and croton. Acids, cinnamic acid, benzoic acid, unsaturated carboxylic acids such as sorbic acid, various carboxylic acids such as oxalic acid, malonic acid, sebacic acid, maleic acid, fumaric acid, and dibasic acids such as itaconic acid; Organic acids such as various phosphoric acids and various sulfonic acids in which a carboxyl group of a carboxylic acid is substituted with a phosphoric acid group or a sulfonyl group, or an organic acid ester thereof, other phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, Benzophenonetetracarboxylic anhydride, ethylene glycol bis (anhydrotrimellitate), glycerol tris (anhydrotrimeltate) Aromatic acid anhydrides such as maleic anhydride, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, alkenylsuccinic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride Examples thereof include acids, cyclic aliphatic acid anhydrides such as methylcyclohexenetetracarboxylic anhydride, and aliphatic acid anhydrides such as polyadipic anhydride, polyazeleic anhydride, and polysebacic anhydride.
As the dispersion medium, for example, terpineol, mineral spirit, xylene, toluene, ethylbenzene, mesitylene, hexane, heptane, octane, decane, dodecane, cyclohexane, cyclooctane, or a mixed solution containing these can be used.
[0070]
The phenol resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, oligoester acrylate resin, xylene resin, bismaleimide triazine resin are contained in the liquid for forming the current collector 7 and the electric connection portion 71. Precursors of various thermosetting resins such as furan resin, urea resin, polyurethane resin, melamine resin, and silicone resin may be added (mixed).
The viscosity of the liquid for forming the current collector 7 and the electric connection portion 71 is adjusted by, for example, appropriately setting the content of the particles, the type and composition of the dispersion medium, the presence and the type of the additive, and the like. can do.
[0071]
In the case of (2), the content of the particles in the liquid for forming the current collector 7 and the electric connection portion 71 varies depending on the type and composition of the dispersion medium and is not particularly limited, but is about 0.1 to 40 wt%. And more preferably about 2 to 20 wt%.
The average particle size of the particles used is not particularly limited, but is preferably about 10 to 100 nm, and more preferably about 30 to 70 nm.
Examples of the reducing agent include ascorbic acid (vitamin C), hydrogen sulfide, oxalic acid, carbon monoxide and the like.
[0072]
As the dispersion medium, for example, low-viscosity oils and fats such as butyl cellosolve and polyethylene glycol, alcohols such as 2-propanol, and a mixed solution containing these can be used.
The viscosity of the liquid for forming the current collector 7 and the electric connection portion 71 can be adjusted, for example, by appropriately setting the content of the particles, the type and the composition of the dispersion medium, and the like.
The liquid for forming the current collector 7 and the electric connection portion 71 is discharged as a droplet 70 from a small hole of the nozzle 40, and a film (thin film or thick film) having a predetermined shape is formed on the upper surface of the substrate 2. Film).
[0073]
Next, this film is subjected to, for example, heat treatment or irradiation with ultraviolet rays, electron beams, radiation, laser beams, or the like.
If necessary, the above operations are repeated to form the current collector 7 and the electric connection portion 71 having a desired thickness.
Note that the current collector 7 and the electric connection portion 71 may be formed integrally or separately. In the latter case, the materials of the current collector 7 and the electrical connection 71 may be the same or different.
[0074]
[2] Formation of first electrode 3
Next, the first electrode 3 is formed on the upper surface of the substrate 2 so as to cover the current collector 7.
The first electrode 3 is formed by supplying a liquid for forming the first electrode 3 to the upper surface of the substrate 2 using an inkjet method.
As the liquid for forming the first electrode 3, for example, a solution containing precursors of various metal oxides can be used.
Examples of the metal oxide precursor to be used include metal alkoxides, organic metal compounds such as acetic acid or metal salts of acetic acid derivatives, metal chlorides, metal sulfides, and inorganic metal compounds such as metal cyanides. One or more of these can be used in combination.
[0075]
The concentration (content) of the metal oxide precursor in the liquid for forming the first electrode 3 varies depending on the type and composition of the solvent and is not particularly limited, but is about 0.1 to 40 wt%. Is preferred, and more preferably about 2 to 20 wt%.
Examples of the solvent include water, ethylene glycol, glycerin, diethylene glycol, polyhydric alcohols such as triethanolamine, methanol, ethanol, isopropanol, butanol, allyl alcohol, furfuryl alcohol, and ethylene glycol monoacetate. A monovalent alcohol or a mixed solution containing these can be used.
The viscosity of the liquid for forming the first electrode 3 can be adjusted, for example, by appropriately setting the concentration of the metal oxide precursor, the type and composition of the solvent, and the like.
[0076]
The liquid for forming the first electrode 3 is discharged as droplets 70 from the small holes of the nozzle 40 to form a film (thin film or thick film) on the upper surface of the substrate 2.
Next, this film is subjected to, for example, heat treatment or irradiation with ultraviolet rays, electron beams, radiation, laser beams, or the like.
If necessary, the above operation is repeated to form the first electrode 3 having a desired thickness.
[0077]
[3] Formation of electron transport layer 4
Next, the electron transport layer 4 is formed on the upper surface of the first electrode 3. Hereinafter, a case where the electron transport layer 4 mainly composed of titanium dioxide is formed will be described as an example.
[3-1] Formation of dense layer 41
First, a liquid for forming the dense layer 41 is supplied to the upper surface of the first electrode 3 by using an inkjet method to form the dense layer 41.
[0078]
As the liquid for forming the dense layer 41, for example, a solution containing a precursor of titanium dioxide can be used.
As a precursor of titanium dioxide, for example, titanium titanium alkoxide such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, and organic titanium such as titanium oxyacetylacetonate (TOA) Examples thereof include compounds and inorganic titanium compounds such as titanium tetrachloride (TTC), and one or more of these can be used as a mixture.
[0079]
The concentration (content) of the titanium dioxide precursor in the liquid for forming the dense layer 41 is not particularly limited, but is preferably about 0.1 to 10 mol / L, and about 0.1 to 2 mol / L. Is more preferable.
Further, as the solvent, for example, anhydrous ethanol, 2-butanol, 2-propanol, 2-n-butoxyethanol or a mixed solution containing these can be used.
[0080]
When using titanium alkoxide as a precursor of titanium dioxide, various additives such as titanium tetrachloride, acetic acid, acetylacetone, diethanolamine, and triethanolamine are added to the liquid for forming the dense layer 41. Is preferred. Thereby, the hydrolysis reaction of the titanium alkoxide can be suppressed. The mixing ratio of this additive and titanium alkoxide is not particularly limited, but is preferably about 1: 2 to 8: 1 in molar ratio.
[0081]
The viscosity of the liquid for forming the dense layer 41 may be determined, for example, by appropriately setting the concentration of the titanium dioxide precursor, the type and composition of the solvent, the presence or absence of the additive, the type, the composition and the concentration, and the like. Can be adjusted.
The liquid for forming the dense layer 41 is discharged as droplets 70 from the small holes of the nozzle 40 to form a film (thin film or thick film) on the upper surface of the first electrode 3.
[0082]
Next, the film is subjected to a heat treatment (drying). Thereby, the solvent is volatilized and removed. The condition of this heat treatment is preferably about 50 to 250 ° C. × 1 to 60 minutes, more preferably about 100 to 200 ° C. × 5 to 30 minutes. The atmosphere for the heat treatment can be, for example, air, nitrogen gas, an inert gas, or a non-oxidizing atmosphere such as a vacuum or reduced pressure state.
[0083]
Further, the film is subjected to a heat treatment (firing) at a higher temperature than the heat treatment. As a result, the organic components (solvent, additives, and the like) remaining in the film can be removed, and amorphous or anatase-type titanium dioxide is generated. The conditions of this heat treatment are preferably about 300 to 700 ° C for about 1 to 70 minutes, and more preferably about 400 to 550 ° C for about 5 to 45 minutes. The atmosphere for the heat treatment may be the same as the above.
When a substrate mainly composed of a resin material (flexible substrate) is used as the substrate 2, it is preferable to perform a hydrothermal synthesis process (hydrothermal treatment) on the film.
[0084]
Here, the hydrothermal synthesis means that the membrane is treated with high-pressure steam (saturated steam). Specifically, the hydrothermal synthesis treatment is performed by storing the substrate on which the film is formed in a closed container together with a small amount of water and heating the closed container. In the closed container, water becomes water vapor by heating, and the pressure in the closed container increases. The high-pressure steam removes the organic components present in the film, and at the same time, a hydrolysis reaction proceeds to the titanium dioxide precursor to form amorphous titanium dioxide. According to the hydrothermal synthesis process, there is an advantage that the film can be processed at a relatively low temperature at which water evaporates (for example, about 100 to 200 ° C.).
[0085]
The above operation is repeated as necessary to form the dense layer 41 having a desired thickness.
Prior to the formation of the dense layer 41, for example, O₂The organic substances adhering to the upper surface of the first electrode 3 may be removed by performing a plasma treatment, an EB treatment, a cleaning treatment with an organic solvent (for example, ethanol, acetone, or the like), or the like.
[0086]
[3-2] Formation of porous layer 42
Next, a liquid for forming the porous layer 42 is supplied to the upper surface of the dense layer 41 using an ink-jet method to form the porous layer 42.
As the liquid for forming the porous layer 42, for example, a dispersion liquid (sol liquid) containing titanium dioxide powder and a precursor of titanium dioxide can be used. Thereby, the porous layer 42 having the above-described configuration can be relatively easily obtained.
[0087]
As the titanium dioxide powder (particles) to be used, any of anatase type titanium dioxide powder alone, rutile type titanium dioxide powder alone or a mixture thereof may be used.
The average particle size of the titanium dioxide powder is not particularly limited, but is preferably about 1 nm to 1 μm, more preferably about 1 to 100 nm, and still more preferably about 5 to 50 nm. Thereby, the titanium dioxide powder can be more uniformly dispersed in the liquid for forming the porous layer 42, and the control of the pore form (for example, the porosity, the distribution of the pores, etc.) of the porous layer 42 is easy. It becomes.
[0088]
When a mixture of anatase-type titanium dioxide powder and rutile-type titanium dioxide powder is used, these two types of powders may have different or different average particle diameters. .
The content of the titanium dioxide powder in the liquid for forming the porous layer 42 is not particularly limited, but is preferably about 0.1 to 10 wt%, and more preferably about 0.5 to 5 wt%.
[0089]
The liquid for forming the porous layer 42 can be prepared as follows.
That is, first, a liquid similar to the liquid for forming the dense layer 41 described above is prepared. The concentration (content) of the titanium dioxide precursor in this liquid is not particularly limited, but is preferably about 0.1 to 3 mol / L, and is preferably about 0.1 to 2 mol / L. More preferred.
[0090]
Next, water is mixed with the liquid. The mixing ratio of the water and the titanium dioxide precursor is not particularly limited, but is preferably about 1: 4 to 4: 1 in molar ratio.
Next, a liquid for forming the porous layer 42 is obtained by mixing titanium dioxide powder with the mixed liquid. The liquid for forming the porous layer 42 may be diluted with a solvent used for the liquid for forming the dense layer 41, if necessary, for example.
The viscosity of the liquid for forming the porous layer 42 is, for example, the content of the titanium dioxide powder, the concentration of the titanium dioxide precursor, the type and composition of the solvent, the presence or absence of the additive, the type, the composition and the concentration. It can be adjusted by appropriately setting the degree of dilution (dilution ratio) and the like.
[0091]
The liquid for forming the porous layer 42 is discharged as droplets 70 from the small holes of the nozzle 40 to form a film (thin film or thick film) on the upper surface of the dense layer 41.
At this time, it is preferable that the droplet 70 is landed (supplied) on the upper surface of the dense layer 41 while heating the dense layer 41. The heating temperature is not particularly limited, but is preferably about 80 to 180 ° C, more preferably about 100 to 160 ° C.
[0092]
Next, this film may be subjected to a heat treatment (for example, baking or the like) as necessary. The condition of this heat treatment is preferably, for example, a temperature of 250 to 500 ° C. × 0.5 to 3 hours.
When a substrate (flexible substrate) mainly composed of a resin material is used as the substrate 2, the above-described hydrothermal synthesis process (hydrothermal treatment) may be performed instead of this heat treatment. Good.
If necessary, the above operations are repeated to form the porous layer 42 having a desired thickness.
[0093]
[4] Formation of dye layer D
Next, a liquid for forming the dye layer D is supplied to the upper surface of the porous layer 42 (electron transport layer 4) by using an inkjet method to form the dye layer D.
As the liquid for forming the dye layer D, for example, a solution or a dispersion (suspension) containing a dye can be used.
[0094]
The concentration (content) of the dye in the liquid for forming the dye layer D is not particularly limited, but is preferably about 0.0001 to 0.1 wt%, and about 0.001 to 0.01 wt%. Is more preferred.
As the solvent or the dispersion medium, for example, water, methanol, ethanol, isopropanol, acetonitrile, ethyl acetate, ether, methylene chloride, NMP (N-methyl-2-pyrrolidone), or a mixed solution containing these can be used. .
The viscosity of the liquid for forming the dye layer D can be adjusted by, for example, appropriately setting the concentration of the dye, the type and composition of the solvent or the dispersion medium, and the like.
The liquid for forming the dye layer D is discharged as droplets 70 from the small holes of the nozzle 40 and supplied to the upper surface of the porous layer 42.
[0095]
Next, 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, drying may be performed by performing a heat treatment or the like at, for example, about 60 to 100 ° C. × about 0.5 to 2 hours. As a result, the dye is adsorbed (chemically adsorbed), bonded (covalent bond, coordinate bond) or the like on the outer surface of the porous layer 42 and the inner surface of the pore 421, for example.
If necessary, the above operation is repeated to form the dye layer D having a desired thickness.
[0096]
[5] Formation of hole transport layer 5
Next, a liquid for forming the hole transport layer 5 is supplied to the upper surface of the porous layer 42 (electron transport layer 4) on which the dye layer D is formed, using an ink-jet method. Form. Hereinafter, a case where the hole transport layer 5 mainly formed of iodide (inorganic p-type semiconductor material) is described as an example.
[0097]
As the liquid for forming the hole transport layer 5, for example, a solution containing iodide can be used.
The liquid for forming the hole transport layer 5 is preferably used as a saturated solution of iodide to a 10-fold diluted solution of the saturated solution.
Further, as the solvent, for example, water, acetonitrile, ethanol, methanol, isopropyl alcohol or a mixed solution containing these can be used, and among them, acetonitrile is particularly preferable.
[0098]
When iodide is used as the constituent material of the hole transport layer 5, it is preferable to add a cyanoethylated compound such as cyanoresin as a binder to the liquid for forming the hole transport layer 5. In this case, the mixing ratio of the iodide and the cyanoethylate is not particularly limited, but is preferably about 99: 1 to 80:20 by weight.
[0099]
In addition, it is preferable to add a hole transport efficiency improving substance having a function of improving hole transport efficiency to the liquid for forming the hole transport layer 5. Thereby, the carrier mobility (hole transport ability) of the hole transport layer 5 can be further improved.
As the hole transport efficiency improving substance, for example, various halides such as ammonium halide can be used, and tetrapropylammonium iodide (TPAI) is particularly preferable.
[0100]
The concentration (content) of the hole transport efficiency improving substance in the liquid for forming the hole transport layer 5 is not particularly limited, but is 1 × 10 5^-4~ 1 × 10^-1It is preferably about 1% by weight.^-4~ 1 × 10^-2More preferably, it is about wt%. Thereby, the effect can be further improved.
Further, it is preferable to add, to the liquid for forming the hole transport layer 5, a crystal size coarsening suppressing substance that suppresses an increase in crystal size when iodide is crystallized. This prevents or suppresses the increase in crystal size of the iodide during crystallization. Therefore, inconveniences such as generation of cracks in the electron transport layer 4 and a decrease in contact between the dye layer D and the hole transport layer 5 can be suitably prevented. As a result, deterioration (deterioration) of characteristics such as the photoelectric conversion efficiency of the photoelectric conversion element 1 can be prevented.
[0101]
Examples of the crystal size coarsening suppressing substance include, for example, sodium cyanide (NaSCN), potassium thiocyanate (KSCN), copper thiocyanate (CuSCN), and thiocyanate, in addition to the cyanoethylated compound and the hole transport efficiency improving substance described above. Ammonium salt (NH₄One or a combination of two or more of thiocyanates (rhodanides) such as SCN) can be used.
[0102]
The concentration (content) of the crystal size coarsening suppressing substance in the liquid for forming the hole transport layer 5 is not particularly limited, but is 1 × 10^{− 6}It is preferably about 10 to 10% by weight.^-4~ 1 × 10^-2More preferably, it is about wt%. Thereby, the effect can be further improved.
The viscosity of the liquid for forming the hole transport layer 5 may be, for example, the type, composition and concentration of the constituent material of the hole transport layer, the type and concentration of the hole transport efficiency improving substance, and the type and composition of the solvent. It can be adjusted by appropriately setting the presence / absence, type, concentration and the like of the additive.
[0103]
The liquid for forming the hole transport layer 5 is discharged as droplets 70 from the small holes of the nozzle 40 to form a film (thin film or thick film) on the upper surface of the porous layer 42 on which the dye layer D is formed. Form.
At this time, the droplet 70 is landed (supplied) on the upper surface of the porous layer 42 on which the dye layer D is formed while heating the dye layer D (the porous layer 42 on which the dye layer D is formed). preferable. The heating temperature is not particularly limited, but is preferably about 50 to 150 ° C, and more preferably about 70 to 100 ° C.
If necessary, the above operation is repeated to form the hole transport layer 5 having a desired thickness.
[0104]
[6] Formation of second electrode 6
Next, a liquid for forming the second electrode 6 is supplied to the upper surface of the hole transport layer 5 by an ink-jet method to form the second electrode 6.
The second electrode 6 can be formed in the same manner as in the step [1] or [2].
Through the steps described above, the photoelectric conversion element 1 is manufactured.
[0105]
In each of the steps [1] to [6], prior to the formation of each layer, a bank defining the shape of each layer is formed, and each layer is defined in a region defined (defined) by the bank. The liquid for formation may be discharged and supplied as droplets 70 from the small holes of the nozzle 40.
By forming the bank before forming each layer, it is possible to prevent the liquid for forming each layer from flowing out to the side (other than the formation region). For this reason, a liquid having a relatively low viscosity can be used as the liquid for forming each layer, and the range of selection of materials used for the liquid for forming each layer can be greatly increased.
[0106]
As a constituent material of this bank, for example, acrylic, acrylic epoxy, photocurable acrylic, and the like can be cited, and any one or a combination of two or more of them can be used.
Examples of the method for forming the bank include a screen printing method and an ink-jet molding method.
For example, a new bank may be formed in each of the steps [2] to [6], or a common bank may be used in two or more consecutive steps.
[0107]
<Second embodiment>
Next, a second embodiment of the photoelectric conversion element of the present invention will be described.
FIG. 5 is a longitudinal sectional view showing a second embodiment of the photoelectric conversion element of the present invention, and FIG. 6 is a plan view showing the configuration of a current collector 7 provided in the photoelectric conversion element shown in FIG.
Hereinafter, the second embodiment will be described, but the description will focus on the differences from the first embodiment, and a description of similar items will be omitted.
[0108]
In the second embodiment, the installation position and the configuration of the current collector 7 are different, and the rest is the same as the first embodiment.
That is, the current collector 7 is disposed so as to be embedded in the substrate 2. Accordingly, unevenness generated on the upper surface of the substrate 2 can be reduced, so that poor connection between the current collector 7 and the first electrode 3 can be more reliably prevented.
[0109]
The current collector 7 shown in FIG. 5 is obtained by, for example, forming a plating layer made of a constituent material (various metal materials) of the current collector 7 on the upper surface of the substrate 2 and then etching the plating layer. And its cross-sectional shape is substantially rectangular. In the case of the current collector 7 having such a shape, it is particularly effective to dispose the current collector 7 so as to be embedded in the substrate 2.
[0110]
As a method for embedding the current collector 7 in the substrate 2, for example, the following method can be mentioned. That is, (1) when the substrate 2 is hard, a concave portion (groove) is formed in the substrate 2 in advance, and the current collector 7 is formed in the concave portion. When it is made of a resin material (a thermoplastic resin or the like), the substrate 2 on which the current collector 7 is formed is subjected to a hot press treatment to be embedded in the substrate 2; After the current collector 7 is formed on the sheet material formed of the precursor (prepolymer) of the thermosetting resin, the sheet material on which the current collector 7 is formed is subjected to a hot pressing process. A method can be used. According to the methods (2) and (3), the current collector 7 can be relatively easily embedded in the substrate 2. In particular, according to the method (3), since the pressing is performed in the state of the curing precursor, the surface shape of the substrate 2 and the current collector 7 can be made more smooth, which is preferable.
[0111]
The current collector 7 includes a first linear body 7a and a second linear body 7b that connects different first linear bodies 7a, and the first linear body 7a has a honeycomb shape. It is arranged in. With such a configuration, when a flexible substrate is used as the substrate 2, the current collector 7 can function as a reinforcing material for the substrate 2, thereby improving the mechanical strength of the entire photoelectric conversion element 1. Can be done.
[0112]
Further, in the present embodiment, the current collector 7 has a minimum unit (each triangular area in FIG. 6) of a region surrounded by the current collector 7 having substantially the same area and substantially the same shape. It is formed so that it becomes. Thereby, in addition to the effects described in the first embodiment, the effect of reinforcing the current collector 7 when a flexible substrate is used as the substrate 2 can be further improved.
In the second embodiment, the same operation and effect as those in the first embodiment can be obtained.
[0113]
As described above, according to the present invention, the current collector 7 that is in contact with the first electrode 3 is provided to improve the conductivity of the entire first electrode 3. Electrons can be efficiently extracted. In particular, in the present invention, since the current collector 7 is composed of a plurality of types of linear bodies having different widths, the current collector 7 can be more uniformly extracted from the first electrode 3. Thus, according to the present invention, sufficient photoelectric conversion efficiency can be obtained even when the size is increased. Further, the photoelectric conversion element 1 of the present invention can be manufactured inexpensively and efficiently.
[0114]
As described above, the illustrated embodiments of the photoelectric conversion element of the present invention have been described. However, the present invention is not limited to these, and the configuration of each unit may be replaced with any configuration that performs the same function. Other configurations (for example, one or more layers for any purpose between layers) may be added.
Further, in each of the above-described embodiments, the configuration in which the current collector is embedded in the surface electrode (first electrode) or the substrate has been described, but the current collector is embedded in both the surface electrode and the substrate. May be configured to be inserted. Further, in the present invention, the current collector may be provided on the electron transport layer side as long as it is in contact with the surface electrode.
[0115]
Further, the arrangement pattern of the current collector is not limited to the configuration shown in the drawing. For example, the shape of the minimum unit of the area surrounded by the current collector may be a pentagon, a hexagon, or the like.
Further, in the present invention, the second linear member may be configured not to connect the first linear members to each other, and further, the third linear member may be configured to include the first linear member and the second linear member. A configuration may be adopted in which the second linear bodies are not connected to each other.
[0116]
【Example】
Next, specific examples of the present invention will be described.
(Example 1)
The photoelectric conversion device shown in FIG. 1 was manufactured as follows.
First, a polyethylene terephthalate substrate having dimensions of 200 mm long × 310 mm wide × 50 μm thick was prepared.
[0117]
-1- Formation of current collector and electrical connection
[Preparation of Liquid for Forming Current Collector and Electrical Connection]
In a mixture of terpineol and toluene, precursors of Ag particles (average particle size: 8 nm), dodecylamine (aggregation inhibitor), methylhexahydrophthalic anhydride (removing agent), and resole-type phenolic resin (thermosetting resin) Were mixed in predetermined amounts to prepare a liquid for forming a current collector and an electric connection portion.
In addition, the viscosity (normal temperature) of the liquid for forming the current collector and the electric connection portion was 3 to 5 cps.
[0118]
[Formation of Current Collector and Electrical Connection]
The substrate is placed on an XY table of a droplet discharge device, and a liquid for forming a current collector and an electric connection portion is discharged as droplets (about 20 pL) onto the upper surface of the substrate, as shown in FIG. The film was patterned into a shape, and then a heat treatment (180 ° C. × 2 hours) was applied to the patterned film to obtain a current collector and an electrical connection.
[0119]
The width (average) of the first linear body is 1 mm, the interval is 5 cm, the width (average) of the second linear body is 0.1 mm, the interval is 1 cm, and the width of the third linear body is (Average) was 0.03 mm, the interval was 2.5 mm, and the height (average) of the current collector was 5 μm. The sheet resistance of the obtained current collector was 0.01 Ω / □.
The dimensions of the electrical connection part were 200 mm long × 10 mm wide × 0.05 μm thick.
[0120]
-2- Formation of first electrode
Next, a first electrode was formed by sputtering ITO at a low temperature so as to cover the current collector. Next, an operation of treating the first electrode with high-pressure steam at 105 ° C. for 300 minutes was performed.
Note that the dimensions of the first electrode were 200 mm long × 300 mm wide × 0.1 μm thick. When viewed from a direction perpendicular to the first electrode, the ratio of the area occupied by the current collector to the entire area of the first electrode was set to 10%.
[0121]
-3- Formation of dense layer (dense electron transport layer)
[Preparation of liquid for forming dense layer]
First, titanium tetraisopropoxide (organic titanium compound) was dissolved in 2-n-butoxyethanol at a concentration of 0.5 mol / L.
Next, a liquid for forming a dense layer was prepared by mixing diethanolamine (additive) with this solution. Diethanolamine was mixed such that the ratio of diethanolamine: titanium tetraisopropoxide (molar ratio) was 2: 1.
The viscosity (normal temperature) of the liquid for forming the dense layer was 3 cps.
[0122]
[Formation of dense layer]
Next, in the same manner as in the above step 1- (using the ink jet method), a liquid for forming a dense layer is discharged as droplets onto the upper surface of the first electrode (ITO electrode) to form a film. An operation of treating the film with high-pressure steam at 120 ° C. for 600 minutes was performed. By repeating this operation, a dense layer was obtained. The resulting dense layer had a porosity of less than 1%.
Note that the dimensions of the dense layer were 200 mm long × 300 mm wide × 0.1 μm thick.
[0123]
-4- Formation of porous layer (porous electron transport layer)
[Preparation of liquid for forming porous layer]
First, titanium tetraisopropoxide (organic titanium compound) was dissolved in 2-propanol at a concentration of 1 mol / L.
Next, acetic acid (additive) and distilled water were mixed into this solution. Acetic acid is mixed such that acetic acid: titanium tetraisopropoxide (molar ratio) becomes 1: 1 and distilled water is mixed such that distilled water: titanium tetraisopropoxide (molar ratio) becomes 1: 1. did.
[0124]
Next, anatase-type titanium dioxide powder (average particle size: 40 nm) was mixed with this solution, and the mixture (dispersion) was diluted twice with 2-propanol to form a porous layer. Was prepared. The content of the anatase type titanium dioxide powder in the liquid for forming the porous layer was adjusted to 3 wt%.
In addition, the viscosity (normal temperature) of the liquid for forming a porous layer was 5 cps.
[0125]
[Formation of porous layer]
Next, the operation of discharging the liquid for forming the porous layer as droplets onto the upper surface of the dense layer heated to 140 ° C. is repeated in the same manner as in the above-mentioned step 1-1 (using the inkjet method). As a result, a porous layer was obtained. The obtained porous layer had a porosity of 34%.
The dimensions of the porous layer were 200 mm long × 300 mm wide × 10 μm thick.
[0126]
-5 Formation of dye layer
[Preparation of Liquid for Forming Dye Layer]
Ruthenium trisbipidil (dye) was dissolved in ethanol to a concentration of 0.005 wt% to prepare a liquid for forming a dye layer.
The viscosity (normal temperature) of the liquid for forming the dye layer was 1 cps.
[Formation of dye layer]
Next, in the same manner as in the above-mentioned step 1- (using the ink jet method), the liquid for forming the dye layer is discharged as droplets onto the upper surface of the porous layer, dried naturally, and then dried at 80 ° C × Heat treatment was performed for 0.5 hour to obtain a dye layer.
[0127]
-6 Formation of hole transport layer
[Preparation of liquid for forming hole transport layer]
First, CuI was dissolved in acetonitrile until it was saturated. Next, tetrapropylammonium iodide (a substance for improving hole transport efficiency), cyanoresin (cyanoethylated compound) and sodium thiocyanate (a substance for suppressing crystal size coarsening) are mixed with this solution to form a liquid for forming a hole transport layer. Was prepared. Tetrapropyl ammonium iodide is 1 × 10^-3wt%, the cyanoresin was used so that the ratio of CuI: cyanoresin (weight ratio) was 97: 3, and the sodium thiocyanate was 1 × 10^-3It mixed so that it might become wt%.
The viscosity (normal temperature) of the liquid for forming the hole transport layer was 3 cps.
[0128]
[Formation of hole transport layer]
Next, in the same manner as in the above-mentioned step 1- (using the ink jet method), the liquid for forming the hole transport layer is applied as droplets to the upper surface of the electron transport layer on which the dye layer is formed by heating to 80 ° C. By repeating the discharging operation, a hole transport layer was obtained.
The dimensions of the hole transport layer were 200 mm long × 300 mm wide × 10 μm thick.
[0129]
-7- Formation of second electrode
A second electrode was formed in the same manner as in Step-2-.
The dimensions of the second electrode were 200 mm long × 300 mm wide × 0.1 μm thick.
[0130]
(Example 2)
The configuration of the current collector was changed as shown in FIG. 6, and other than that, the photoelectric conversion element shown in FIG. 5 was manufactured in substantially the same manner as in Example 1.
Note that the current collector and the electrical connection portion were formed by forming a polyethylene terephthalate substrate on a rolled copper foil and then etching the copper foil. Prior to the step-3, the current collector was embedded in the substrate by subjecting the substrate on which the current collector was formed to a heat press treatment (condition: 180 ° C. × 60 minutes).
The sheet resistance of the obtained current collector was 0.006 Ω / □.
When viewed from a direction perpendicular to the first electrode, the ratio of the area occupied by the current collector to the entire area of the first electrode was 15%.
[0131]
(Comparative Example 1)
A photoelectric conversion element shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the current collector was omitted.
(Comparative Example 2)
The current collector was composed of only the first linear body, that is, the first linear body was arranged in a grid with a width (average) of 1 mm and an interval of 5 cm. 1, the photoelectric conversion element shown in FIG. 1 was manufactured.
In addition, the sheet resistance value of the obtained current collector was 0.01 Ω / □.
When viewed from a direction perpendicular to the first electrode, the ratio of the area occupied by the current collector to the entire area of the first electrode was set to 4%.
[0132]
(Comparative Example 3)
The current collector is composed of only the second linear body, that is, the second linear body is arranged in a grid with a width (average) of 0.1 mm and an interval of 1 cm. In the same manner as in Example 1, the photoelectric conversion element shown in FIG. 1 was manufactured.
In addition, the sheet resistance value of the obtained current collector was 0.01 Ω / □.
When viewed from a direction perpendicular to the first electrode, the ratio of the area occupied by the current collector to the entire area of the first electrode was set to 2%.
[0133]
(Comparative Example 4)
The current collector is composed of only the third linear body, that is, the third linear body is arranged in a grid with a width (average) of 0.03 mm and an interval of 2.5 mm. In the same manner as in Example 1, the photoelectric conversion element shown in FIG. 1 was manufactured.
In addition, the sheet resistance value of the obtained current collector was 0.01 Ω / □.
When viewed from a direction perpendicular to the first electrode, the ratio of the area occupied by the current collector to the entire area of the first electrode was 2.4%.
[0134]
(Evaluation)
Light from an artificial sun lamp (irradiation light intensity: AM 1.5, 100 W / m) was applied to the photoelectric conversion elements manufactured in Examples 1 and 2 and Comparative Examples 1 to 4.²) Was applied to the substrate from a direction of 90 °, and the photoelectric conversion efficiency of each photoelectric conversion element was compared.
Table 1 shows the results. In Table 1, the photoelectric conversion efficiency of each photoelectric conversion element is shown as a relative value, with the photoelectric conversion efficiency of the photoelectric conversion element manufactured in Comparative Example 1 being 100.
[0135]
[Table 1]

[0136]
As shown in Table 1, the photoelectric conversion elements (the photoelectric conversion elements of the present invention) manufactured in Examples 1 and 2 each include a photoelectric conversion element including a current collector formed of a linear body having the same width (comparative). Compared with (the photoelectric conversion elements of Examples 2 to 4), it was clarified that the decrease in the photoelectric conversion efficiency due to the enlargement of the area was small.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of a photoelectric conversion element of the present invention.
FIG. 2 is a sectional view taken along line AA in FIG.
FIG. 3 is a plan view showing a configuration of a current collector 7 provided in the photoelectric conversion element shown in FIG.
FIG. 4 is a diagram schematically showing a droplet discharge device used in a method for manufacturing a photoelectric conversion element.
FIG. 5 is a longitudinal sectional view showing a second embodiment of the photoelectric conversion element of the present invention.
6 is a plan view showing a configuration of a current collector 7 provided in the photoelectric conversion element shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoelectric conversion element 2 ... Substrate 3 ... 1st electrode 4 ... Electron transport layer 41 ... Dense layer 42 ... Porous layer 421 ... Hole 5 ... Hole transport layer 6 ... Second electrode 7 Current collector 7a First linear body 7b Second linear body 7c Third linear body 71 Electrical connection unit 8 External circuit D ... Dye layer 10... Droplet discharge device 20... Mounting table 30. X-axis drive roller 40. Nozzle 50... Droplet discharge head 60... Y-axis drive mechanism 70.

Claims (18)

A surface electrode provided on the substrate,
A counter electrode provided to face the surface electrode;
Located between the surface electrode and the counter electrode, at least a portion of a porous electron transport layer,
A dye layer in contact with the electron transport layer;
A hole transporting layer located between the electron transporting layer and the counter electrode, and in contact with the dye layer;
A photoelectric conversion element configured to provide a current collector made of a material having a lower electric resistance than the constituent material of the surface electrode, so as to be in contact with the surface electrode, and to improve the conductivity of the entire surface electrode,
The current collector is connected to the first linear body and the first linear body so as to branch or intersect with the first linear body, and has a width smaller than that of the first linear body. A photoelectric conversion element comprising: a second linear body. The photoelectric conversion element according to claim 1, wherein the second linear body connects the different first linear bodies to each other. When the width (average) of the first linear body is A [mm] and the width (average) of the second linear body is B [mm], A / B is 1 to 100. Item 3. The photoelectric conversion element according to item 1 or 2. The current collector is connected to the second linear body so as to branch or intersect with the second linear body, and includes a third linear body that is narrower than the second linear body. The photoelectric conversion device according to claim 1. The photoelectric conversion element according to claim 4, wherein the third linear body connects the first linear body and the second linear body, or connects the different second linear bodies to each other. . When the width (average) of the second linear body is B [mm] and the width (average) of the third linear body is C [mm], B / C is 1 to 100. Item 6. The photoelectric conversion element according to item 4 or 5. The photoelectric conversion element according to claim 1, wherein at least the first linear body is arranged in a lattice. The photoelectric conversion element according to claim 1, wherein at least the first linear body is arranged in a honeycomb shape. The photoelectric conversion element according to claim 1, wherein at least a part of the current collector is provided so as to be embedded in the surface electrode. The photoelectric conversion element according to claim 1, wherein at least a part of the current collector is provided so as to be embedded in the substrate. The substrate is mainly made of a resin material,
The said current collector is provided so that at least one part may be embedded in the said board | substrate by performing the hot press process with respect to the said board | substrate with which the said current collector was formed. Photoelectric conversion element. The substrate provided so that at least a part of the current collector is embedded therein is formed on a sheet material mainly formed of a precursor of a thermosetting resin. The photoelectric conversion element according to claim 10, wherein the photoelectric conversion element is obtained by subjecting the sheet material on which is formed is subjected to a heat press treatment. The photoelectric conversion element according to claim 1, wherein the current collector has an average height of 0.2 mm or less. The photoelectric device according to claim 1, wherein a ratio of an area occupied by the current collector to an entire area of the surface electrode is 0.01 to 30% when viewed from a direction perpendicular to the surface electrode. Conversion element. 15. The photoelectric conversion element according to claim 1, wherein the minimum units of the region surrounded by the current collector have substantially the same area. 16. The photoelectric conversion element according to claim 1, wherein the minimum units of the region surrounded by the current collector have substantially the same shape. 17. The photoelectric conversion element according to claim 1, wherein the current collector is formed by using an inkjet method. 18. The photoelectric conversion device according to claim 1, wherein the substrate is a flexible substrate mainly made of a resin material.

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