JP2012099592A - Organic photoelectric conversion element, solar cell and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bulk hetero junction type organic photoelectric conversion element having high photoelectric conversion efficiency and durability, a method for manufacturing the organic photoelectric conversion element, and a solar cell using the organic photoelectric conversion element.SOLUTION: The organic photoelectric conversion element comprises at least a first electrode; an organic photoelectric conversion layer containing a p-type organic semiconductor material with electron-donating properties, an n-type organic semiconductor material with electron-receptive properties, and metal oxide fine particles; and a second electrode on a substrate. The method for manufacturing the organic photoelectric conversion element includes an organic photoelectric conversion layer forming step that a coating liquid which contains the p-type organic semiconductor material and the n-type organic semiconductor material and in which the metal oxide fine particles are dispersed, is applied to the electrode to form a layer, then it is heat-treated at 90°C or higher to eccentrically dispose the metal oxide fine particles in the normal direction to the organic photoelectric conversion layer surface and to increase a concentration of the metal oxide fine particles in the vicinity of at least one surface.

Description

  The present invention relates to an organic photoelectric conversion element and a solar cell, and more particularly to a bulk heterojunction type organic photoelectric conversion element, a solar cell using the organic photoelectric conversion element, and a method for manufacturing the same.

  Due to the recent rise in fossil energy, there is a demand for a system that can generate electric power directly from natural energy. A solar cell using single crystal, polycrystalline or amorphous Si, a compound solar cell such as GaAs or CIGS, or Dye-sensitized photoelectric conversion elements (Gretzel cells) and the like have been developed and put into practical use.

  However, the cost of generating electricity with these solar cells is still higher than the price of electricity generated and transmitted using fossil fuels, which has hindered widespread use. In addition, since heavy glass must be used for the substrate, reinforcement work is required at the time of installation, which is one of the causes that increase the power generation cost.

  For such a situation, as a solar cell that can achieve a lower cost than the power generation cost of fossil fuel, an electron donor layer (p-type semiconductor layer) and an electron acceptor layer (n A bulk heterojunction photoelectric conversion element is proposed in which a photoelectric conversion layer mixed with a semiconductor layer is mixed (see, for example, Non-Patent Document 1 and Patent Document 1).

  Since these bulk heterojunction solar cells are formed by a coating process other than the anode and the cathode, it is expected that they can be manufactured at high speed and at low cost, and there is a possibility that the problems of conventional high power generation costs can be solved. is there. Furthermore, unlike conventional Si-based solar cells, compound semiconductor-based solar cells, or dye-sensitized solar cells, there is no process at a temperature higher than 160 ° C., so that it can be formed on a cheap and lightweight plastic substrate. Is done.

  For example, in the invention described in Non-Patent Document 1, conversion efficiency exceeding 5% has been achieved. This is achieved by utilizing intramolecular charge transfer between a thiophene ring and a benzothiadiazole ring, which is extremely long. This is because it has become possible to absorb a wide range of sunlight up to the wavelength (˜900 nm).

  Moreover, although durability is also required for the solar cell, the durability of the organic thin-film solar cell is still insufficient. In Non-Patent Document 2 using the above materials, it is reported that the photoelectric conversion efficiency is reduced by about 40% in 100 hours.

  In order to deal with such problems, the layers are stacked in the reverse order of normal organic thin-film solar cells, the electrons are taken out from the transparent electrode side, and the holes are taken out from the stable metal electrode side having a deep work function. An organic thin film solar cell has been proposed (Patent Document 2).

  It has been disclosed that such a configuration eliminates the need to use a metal having a shallow work function that is unstable and easily oxidized in the electrode, suppresses deterioration due to the electrode, and can greatly improve the life.

In such a reverse layer configuration, since it is necessary to coat and laminate a photoelectric conversion layer on the electron transport layer, the material used for the electron transport layer can be formed into a coating and is insoluble in the solvent for coating the photoelectric conversion layer. A material is required. However, there are few reports of such electron transport materials, and TiO _x is disclosed as an electron transport material that can be formed by a coating process (Patent Document 2), but the TiO _x layer is formed by reacting moisture with titanium alkoxide. Therefore, it cannot be said that it is a preferable material for an organic photoelectric conversion element that is deteriorated by moisture, and there is a problem that a stable film cannot be formed on a mass production scale.

  Moreover, although TiOx is disclosed as an electron transport material that can be formed on the photoelectric conversion layer by a coating process in the normal layer (Patent Document 3), as described above, a preferable material for an organic photoelectric conversion element in which deterioration due to moisture occurs. However, there is a problem that a stable film cannot be formed on a mass production scale.

  On the other hand, in order to improve the photoelectric conversion efficiency, the photoelectric conversion layer contains inorganic nanoparticles, and the inorganic nanoparticles have a concentration distribution in the normal direction from the plane of the positive electrode or the negative electrode, thereby improving the charge extraction efficiency. A method for improving this has been proposed (Patent Document 4). However, in the present invention, in order to have a concentration distribution, a multi-layer coating process is necessary, and the process load is large. Further, since the photoelectric conversion layer is a multi-layer coating, there is a problem in durability because the interface contact between the photoelectric conversion layers varies with time.

JP-T 8-500701 JP 2009-146981 A Special table 2009-522818 JP 2009-158730 A

Nature Mat. , Vol. 6 (2007), p497, A.I. Heeger etc. Science_317_2007_p222

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a bulk heterojunction organic photoelectric conversion element having high photoelectric conversion efficiency and durability, a method for producing the same, and a solar cell using the same. There is to do.

  The above object of the present invention can be achieved by the following constitution.

(1)
At least a first electrode on the substrate, an organic photoelectric conversion layer containing a p-type organic semiconductor material having an electron donating property, an n-type organic semiconductor material having an electron accepting property, and metal oxide fine particles, and a second electrode In the manufacturing method of the organic photoelectric conversion element having,
In the step of forming the organic photoelectric conversion layer, a coating liquid containing the p-type organic semiconductor material and the n-type organic semiconductor material and in which metal oxide fine particles are dispersed is applied onto the electrode to form a layer. Thereafter, the metal oxide fine particles are unevenly distributed in the normal direction with respect to the surface of the organic photoelectric conversion layer by performing a heat treatment at 90 ° C. or higher to increase the concentration of the metal oxide fine particles in the vicinity of at least one surface. The manufacturing method of the organic photoelectric conversion element characterized by these.

(2)
The step of forming the organic photoelectric conversion layer is performed at 90 ° C. or higher after applying a coating liquid containing the p-type organic semiconductor material and the n-type organic semiconductor material and in which metal oxide fine particles are dispersed on the electrode. The method for producing an organic photoelectric conversion device according to (1), wherein the layer is formed by drying at a temperature of 5 ° C.

(3)
The organic photoelectric conversion element according to (1) or (2), wherein the metal oxide fine particles are unevenly distributed in the vicinity of both surfaces of the organic photoelectric conversion layer.

(4)
The average primary particle diameter of the metal oxide fine particles is 30% or less with respect to the film thickness of the photoelectric conversion layer. The organic photoelectric conversion element according to (2) or (3),

(5)
The content of the metal oxide fine particles is 0.5% by mass or more and 10% by mass or less based on the total of the p-type organic semiconductor material and the n-type organic semiconductor material (3) or ( The organic photoelectric conversion element as described in 4).

(6)
A solar cell comprising the organic photoelectric conversion device according to any one of (3) to (5).

  ADVANTAGE OF THE INVENTION According to this invention, the bulk heterojunction type organic photoelectric conversion element which has high photoelectric conversion efficiency and durability, its manufacturing method, and a solar cell using the same can be provided.

Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element of a normal layer structure. Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element of a reverse layer structure. Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with a tandem-type photoelectric conversion layer. An example of the cross-sectional TEM image of the organic photoelectric converting layer of this invention. An example of the cross-sectional TEM image of the organic photoelectric converting layer of this invention.

  Hereinafter, although the typical form for implementing this invention is demonstrated, this invention is not necessarily limited to these.

  As a result of diligent investigations on the above problems, the inventors of the present invention applied metal oxide fine particles to a bulk heterojunction photoelectric conversion layer coating liquid in which a p-type organic semiconductor material and an n-type organic semiconductor material having electron acceptability were mixed. When the coating is applied, the metal oxide fine particles are not dispersed in the photoelectric conversion layer depending on the heat treatment temperature after layer formation or the temperature at which the coating solution is dried, but either from the plane of the positive electrode or the negative electrode in the normal direction. It was found that it is unevenly distributed in the vicinity of one or both surfaces, and that the above-mentioned problems can be achieved.

  When light is incident on a bulk heterojunction photoelectric conversion layer in which a p-type organic semiconductor material and an n-type organic semiconductor material are mixed, electrons from the p-type organic semiconductor material start from the highest occupied orbit (hereinafter referred to as “HOMO”). Excited in the lowest unoccupied orbit (hereinafter referred to as “LUMO”), the electrons move to the conduction band of the n-type organic semiconductor material, and then move to the conduction band of the p-type conjugated polymer via an external circuit. Electrons generated in the conduction band of the p-type conjugated polymer move to the LUMO level.

  On the other hand, when light is incident, holes generated at the HOMO level of the p-type organic semiconductor material move to the valence band of the n-type semiconductor via the external circuit. Thus, a photocurrent flows in the bulk heterojunction photoelectric conversion layer. It is considered that such photocharge separation is promoted as the contact interface between the p-type organic semiconductor material and the n-type semiconductor material increases.

  A bulk heterojunction photoelectric conversion layer in which a p-type organic semiconductor material and an n-type organic semiconductor material are mixed is coated with a mixed solution, and then annealed by heat to promote the crystallinity of the p-type organic semiconductor material. It is known that a microphase separation structure is formed, the contact interface between the p-type organic semiconductor material and the n-type organic semiconductor material is increased, and the conversion efficiency is improved.

  The present inventors apply a bulk heterojunction photoelectric conversion layer coating liquid in which a p-type organic semiconductor material, an n-type organic semiconductor material, and metal oxide fine particles are mixed to form a layer, and then perform a heat treatment at 90 ° C. or higher. Or by applying a coating liquid and drying at a temperature of 90 ° C. or more to form a layer, the metal oxide fine particles are not dispersed in the photoelectric conversion layer, but are normal to the plane of the positive electrode or the negative electrode And found that it is unevenly distributed in the vicinity of one or both surfaces. Japanese Patent Application Laid-Open No. 2009-158730 describes an example in which, after applying a mixed coating solution, drying is performed in a vacuum thermostat at 80 ° C. for 60 minutes, and a concentration distribution is provided in the film thickness direction. However, according to the method of the present invention, the photoelectric conversion efficiency and durability superior to those of the prior art are exhibited. This seems to be because at least the orientation of the metal oxide fine particles is surely and clearly advanced by the method of the present invention.

  In this regard, the present inventors have performed p-type organic by performing a heat treatment at 90 ° C. or higher after coating the mixed coating liquid, or by drying at a temperature of 90 ° C. or higher after coating the coating liquid to form a layer. In the process of promoting the crystallinity of the semiconductor material and forming the micro phase separation structure, the metal oxide fine particles are pushed out and are considered to be unevenly distributed near the surface of one or both of the normal directions consisting of the plane of the positive electrode or the negative electrode. ing.

  In the present invention, the metal oxide fine particles are unevenly distributed in the vicinity of one surface in the normal direction consisting of the plane of the positive electrode or the negative electrode, so that the electron acceptability is increased by the work function, or electrons are efficiently taken out. The acceptability increases and holes can be taken out efficiently.

  It was thought that metal oxide fine particles were unevenly distributed in the vicinity of both surfaces in the normal direction from the plane of the positive electrode or negative electrode. I found it. The reason for this is that the metal oxide fine particles do not form a continuous layer in the plane direction only by being unevenly distributed, so that electrons or holes are taken out from the p-type organic semiconductor material and the n-type organic semiconductor material. The present inventors consider that this is not disturbed.

  In addition, by applying a liquid in which a p-type organic semiconductor material, an n-type organic semiconductor material, and metal oxide fine particles are mixed, the metal oxide fine particles are placed in one or both of the normal directions of the positive or negative electrode planes. Unlike the photoelectric conversion layer in which metal oxide fine particles formed by multi-layer coating are unevenly distributed, durability is improved by uneven distribution in the vicinity of the surface, because there is no interface between the photoelectric conversion layers. The present inventors consider that the microlayer separation structure does not change, and that the flow of metal oxide fine particles in the photoelectric conversion layer is suppressed because the microlayer separation structure is unevenly distributed at the manufacturing stage. ing.

  Hereinafter, details of each component according to the present invention will be sequentially described.

[Configuration of organic photoelectric conversion element and solar cell]
FIG. 1 is an example of a cross-sectional view showing a normal layer type bulk heterojunction type organic photoelectric conversion element. In FIG. 1, a bulk heterojunction type organic photoelectric conversion element 10 includes a transparent electrode (generally an anode) 12, a hole transport layer 17, a photoelectric conversion layer 14, an electron transport layer 18 and a counter electrode (generally a cathode) on the surface of a substrate 11. ) 13 are sequentially stacked.

  The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion layer 14, and the counter electrode 13 that are sequentially stacked. In the present embodiment, since light photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light subjected to photoelectric conversion, that is, transparent to the wavelength of the light to be photoelectrically converted. It is an important member. As the substrate 11, for example, a glass substrate or a resin substrate is used. The substrate 11 is not essential. For example, the bulk heterojunction type organic photoelectric conversion element 10 may be configured by forming the transparent electrode 12 and the counter electrode 13 on both surfaces of the photoelectric conversion layer 14.

  The photoelectric conversion layer 14 is a layer that converts light energy into electric energy, and is configured by uniformly mixing a p-type organic semiconductor material and an n-type organic semiconductor material. The p-type organic semiconductor material functions relatively as an electron donor (donor), and the n-type organic semiconductor material functions relatively as an electron acceptor (acceptor).

  Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

  In FIG. 1, light incident from the transparent electrode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the photoelectric conversion layer of the photoelectric conversion layer 14, and electrons move from the electron donor to the electron acceptor. Thus, a hole-electron pair (charge separation state) is formed. In the case where the generated electric charges have different internal electric fields, for example, when the work functions of the transparent electrode 12 and the counter electrode 13 are different, the electrons pass between the electron acceptors and the holes are between the electron donors due to the potential difference between the transparent electrode 12 and the counter electrode 13. And is carried to different electrodes, and photocurrent is detected.

  Here, since the work function of the transparent electrode 12 is usually larger than that of the counter electrode 13, holes are transported to the transparent electrode 12 and electrons are transported to the counter electrode 13.

  If the work function is reversed, electrons and holes are transported in the opposite direction to the reverse layer configuration.

  FIG. 2 is an example of a cross-sectional view showing an inverted layer bulk heterojunction organic photoelectric conversion element. As described above, the work function relationship is reversed, and the positions of the hole transport layer 17 and the electron transport layer 18 in FIG.

  Although not shown in FIGS. 1 and 2, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

  Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). FIG. 3 is an example of a cross-sectional view illustrating an organic photoelectric conversion element including a tandem photoelectric conversion layer.

  In the case of the tandem configuration, the transparent electrode 12, the electron transport layer 18, and the first photoelectric conversion layer 14 ′ are sequentially stacked on the substrate 11, the charge recombination layer 15 is stacked, and then the second photoelectric conversion layer 16. Then, by stacking the counter electrode 13, a tandem configuration can be obtained. The second photoelectric conversion layer 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion layer 14 'or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. is there. Moreover, you may have the positive hole transport layer 17 between 1st photoelectric converting layer 14 ', 2nd photoelectric converting layer 16, and each electrode.

  In the present invention, the photoelectric conversion layer is formed by applying a mixed solution of a p-type organic semiconductor material, an n-type organic semiconductor material, and metal oxide fine particles, and the metal oxide fine particles are positive or It is unevenly distributed in the vicinity of one or both surfaces with respect to the normal direction composed of the plane of the negative electrode. Therefore, as described above, the charge generated by the photoreaction in the photoelectric conversion layer can be more efficiently transported to the electrode or an adjacent layer.

  Below, the material which comprises these layers is described.

[Metal oxide fine particles]
The metal oxide fine particles of the present invention will be described.

  The metal oxide of the metal oxide fine particles is selected from, for example, Ti, Zn, Ge, Zr, Hf, Si, Sn, Mn, Ga, Mo, In, Sb, Ta, V, Y, Al, Ni, and Nb. At least one kind of metal oxide, or a composite metal oxide obtained by combining two or more of these metals, and the metal oxide fine particles contain the metal oxide or the composite metal oxide. It is preferable.

Examples of the metal oxide include ZnO, GeO ₂ , TiO ₂ , ZrO ₂ , HfO ₂ , SiO ₂ , SnO, SnO ₂ , SnO ₃ , Mn ₂ O ₃ , Ga ₂ O ₃ , Mo ₂ O ₃ , In _2. Examples include O ₃ , Sb ₂ O ₃ , Ta ₂ O ₅ , V ₂ O ₅ , Y ₂ O ₃ , Al ₂ O ₃ , NiO, Ni ₂ O ₃ , and Nb ₂ O ₅ .

  Examples of the composite metal oxide include a composite oxide of titanium and zirconium, a composite oxide of titanium, zirconia and hafnium, a composite oxide of titanium and barium, a composite oxide of titanium and silicon, and a composite of titanium, zirconium and silicon. Oxides, composite oxides of titanium and tin, composite oxides of titanium, zirconia and tin, AZO (Al doped ZnO), indium tin oxide (ITO), antimony tin oxide (ATO), GZO (Ga doped) ZnO), indium zinc oxide (IZO), and the like.

As such a metal oxide, TiO ₂ , SnO ₂ , ZrO ₂ , SiO ₂ , AZO, and GZO are preferable, and TiO ₂ and SnO ₂ are more preferable. The crystal structure of TiO ₂ may be any one of anatase type (tetragonal), rutile type (tetragonal), and brucite type (orthorhombic), but rutile type is preferable, and both natase type and brucite type are mixed. May be.

  The method for producing the metal oxide fine particles is not particularly limited, and any known method can be used. For example, desired oxide fine particles can be obtained by using a metal salt or metal alkoxide as a raw material and hydrolyzing in a reaction system containing water.

  The metal oxide fine particles of the present invention preferably have an average primary particle size of 30% or less with respect to the film thickness of the photoelectric conversion layer. When the average primary particle size is 30% or less with respect to the film thickness of the photoelectric conversion layer, it is easy to be unevenly distributed in the vicinity of one or both surfaces with respect to the normal direction composed of the plane of the positive electrode or the negative electrode, It is easy to make the film thickness uniform and suppresses the occurrence of short circuit of the battery. Usually, the film thickness of the bulk heterojunction photoelectric conversion layer is from 50 nm to 400 nm, more preferably from 80 nm to 300 nm. Therefore, the average primary particle diameter of the metal oxide fine particles is preferably 1 nm or more and 90 nm or less. Moreover, it is generally difficult to obtain metal oxide fine particles having an average primary particle size smaller than 1 nm. On the other hand, if the average primary particle size is too small, the metal oxide fine particles form a continuous layer in the plane direction, making it difficult to obtain the effects of the present invention. The average primary particle size of the metal oxide fine particles is preferably 2 nm or more, more preferably 3 nm or more.

  The average primary particle size of the metal oxide fine particles can be measured by a method known in the art, for example, by TEM, adsorption method, light scattering method, SAXS, X-ray diffraction (XRD) apparatus or the like. It can be measured. In TEM, observation is performed with an electron microscope. When the particle size distribution is wide, it is necessary to pay attention to whether or not the particles entering the field of view represent all particles. In the adsorption method, the BET surface area is evaluated by N2 adsorption or the like.

  The content of the metal oxide fine particles of the present invention is preferably 0.5 to 10% by mass with respect to the total of the p-type organic semiconductor material and the n-type organic semiconductor material having electron accepting properties. By setting this range, the metal oxide fine particles are likely to be unevenly distributed in the vicinity of one or both surfaces with respect to the normal direction consisting of the plane of the positive electrode or the negative electrode, the film thickness can be easily made uniform, and the battery can be short-circuited. Suppresses the occurrence. More preferably, it is 1 mass% to 5 mass%.

  The metal oxide fine particles of the present invention are desirably used in a state of being dispersed in a solution in advance. As the dispersion solution, a solvent used in a method for forming a bulk heterojunction layer described later is preferable, and a solvent in which metal oxide fine particles do not aggregate or settle when mixed with a solvent used in a method for forming a bulk heterojunction layer is preferable. The dispersion solution may contain a dispersant such as a surfactant.

[P-type organic semiconductor materials]
Examples of the p-type organic semiconductor material used for the photoelectric conversion layer (bulk heterojunction layer) of the present invention include various condensed polycyclic aromatic low molecular compounds and conjugated polymers.

  Examples of the condensed polycyclic aromatic compound include oligothiophene, oligoparaphenylene, fluorene, carbazole, anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, Ovalene, circumcamanthracene, bisanthene, zestrene, heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, thienothiophene, benzodithiophene, cyclopentadithiophene, dithienopyrrole, dithienosilole, dithienonaphthalene, benzothiophenobenzothiophene Compounds such as tradithiophene, thienopyrazine, benzothiadiazole, diketopyrrolopyrrole, pyrazolotriazole, Firin or copper phthalocyanine, tetrathiafulvalene (TTF) - tetracyanoquinodimethane (TCNQ), bis-ethylenedioxy-thia tetrathiafulvalene (BEDTTTF), and the like, and these derivatives.

  In the present invention, the low molecular weight compound means a single molecule having no distribution in the molecular weight of the compound. On the other hand, the polymer compound means an aggregate of compounds having a certain molecular weight distribution by reacting a predetermined monomer. However, in practical terms, when defining by molecular weight, a compound having a molecular weight of 5000 or more is preferably classified as a polymer compound. More preferably, it is 10,000 or more, More preferably, it is 30000 or more. On the other hand, since the solubility decreases as the molecular weight increases, the molecular weight is preferably 1,000,000 or less, more preferably 100,000 or less. The molecular weight can be measured by gel permeation chromatography (GPC). Purification according to molecular weight can also be performed by preparative gel permeation chromatography (GPC).

  A more preferable p-type semiconductor material is a conjugated polymer semiconductor material having a conjugated double bond in the molecular structure, and a known conjugated polymer material can be used as the conjugated polymer semiconductor material.

  As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and an oligomer thereof, or a technical group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, polythiophene-thienothiophene copolymer, polythiophene-diketopyrrolopyrrole copolymer described in WO08 / 000664, Adv. Mater. , 2007, p4160, a polythiophene-thiazolothiazole copolymer, Nature Mat. vol. 6 (2007), p497 described in PCPDTBT, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane. Of these, polythiophene copolymers such as poly-3-hexylthiophene (P3HT) and PCPDTBT are particularly preferred.

  Moreover, you may use together a condensed polycyclic aromatic low molecular weight compound and a conjugated polymer. Further, a known oligomer material may be used in combination.

  As the oligomer material, α-sexual thiophene, α, ω-dihexyl-α-sexual thiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3-butoxypropyl)-, which are thiophene hexamers, are used. Oligomers such as α-sexithiophene can be preferably used.

[N-type organic semiconductor materials]
The n-type organic semiconductor material used for the bulk heterojunction layer of the present invention is not particularly limited. For example, a perfluoro compound (perfluoropentacene) in which hydrogen atoms of a p-type semiconductor such as fullerene and octaazaporphyrin are substituted with fluorine atoms. And perfluorophthalocyanine), naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide and other aromatic carboxylic acid anhydrides and imidized polymers thereof as a skeleton A compound etc. can be mentioned.

  However, fullerene derivatives that can perform charge separation with various p-type organic semiconductor materials at high speed (up to 50 fs) and efficiently are preferable. Fullerene derivatives include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc. Partially by hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, etc. Examples thereof include substituted fullerene derivatives.

  Among them, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61- Butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n-hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, US Pat. No. 7,329,709, etc. It is preferable to use a fullerene derivative having a substituent and having improved solubility, such as fullerene having a cyclic ether group such as a calligraphy.

[Method of forming bulk heterojunction layer]
The bulk heterojunction layer of the present invention is formed by applying a mixed solution of a p-type organic semiconductor material, an n-type organic semiconductor material, and metal oxide fine particles. Coating methods include casting, spin coating, blade coating, wire bar coating, gravure coating, spray coating, dipping (dipping) coating, bead coating, air knife coating, curtain coating, and inkjet. Conventional methods such as the Langmuir-Blodgett (LB) method, such as a printing method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, a flexographic printing method, and the like. It is particularly preferred to use the blade coating method.

  When a bulk heterojunction layer is formed using a coating method, it is preferable to use a solvent that can dissolve or disperse the p-type organic semiconductor material and the n-type organic semiconductor material and disperse the metal oxide fine particles. Examples of the solvent include hydrocarbon solvents such as hexane, octane, decane, toluene, xylene, ethylbenzene, and 1-methylnaphthalene, for example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, such as dichloromethane, Halogenated hydrocarbon solvents such as chloroform, tetrachloromethane, dichloroethane, trichloroethane, tetrachloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, for example, ester solvents such as ethyl acetate, butyl acetate, amyl acetate, Alcohols such as methanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol Solvents such as ether solvents such as dibutyl ether, tetrahydrofuran, dioxane, anisole such as N, N-dimethylformamide, N, N-dimethylacetamide, 1-methyl-2-pyrrolidone, 1-methyl-2-imidazolid Examples thereof include polar solvents such as non- and dimethyl sulfoxide. Preferably, toluene, chlorobenzene, dichlorobenzene, trichlorobenzene, and xylene are used.

  The mixing ratio of the p-type organic semiconductor material and the n-type organic semiconductor material of the bulk heterojunction photoelectric conversion layer of the present invention is preferably in the range of 2: 8 to 8: 2, more preferably 4: 6 to 6 in terms of mass ratio. : 4 range. The content of the metal oxide fine particles of the present invention is preferably in the range of 0.5 to 10% by mass, more preferably in the range of 1 to 10% by mass with respect to the total of the p-type organic semiconductor material and the n-type organic semiconductor material. is there.

  The film thickness of the bulk heterojunction photoelectric conversion layer of the present invention is preferably from 50 nm to 400 nm, more preferably from 80 nm to 300 nm.

  The solid concentration of the solution used for coating depends on the coating method and the film thickness, but is preferably 1% by mass to 15% by mass, and more preferably 1.5% by mass to 10% by mass.

  To obtain a bulk heterojunction photoelectric conversion layer in which the metal oxide fine particles of the present invention are unevenly distributed in the vicinity of one or both surfaces in the organic photoelectric conversion layer with respect to the normal direction composed of the plane of the positive electrode or the negative electrode It is necessary to apply a coating solution to form a layer and then perform a heat treatment at 90 ° C. or higher, or to apply a coating solution and dry at a temperature of 90 ° C. or higher to form a layer. When the heat treatment temperature or the drying temperature is less than 90 ° C., the metal oxide fine particles are not unevenly distributed near the surface and are dispersed in the photoelectric conversion layer. Preferably it is the range of 90 to 200 degreeC, More preferably, it is the range of 100 to 160 degreeC. The heat treatment time is preferably 3 minutes to 30 minutes, more preferably 5 minutes to 15 minutes. The drying time is preferably in the range of 30 seconds to 5 minutes, more preferably in the range of 40 seconds to 2 minutes. When the temperature exceeds 160 ° C., the metal oxide fine particles are unevenly distributed, but the p-type organic semiconductor material and the n-type organic semiconductor material are excessively phase-separated to reduce the contact interface area between the metal oxide particles and reduce the effect. start. In addition, after forming the organic photoelectric conversion layer and before providing another layer, heat treatment and drying at a predetermined temperature are preferable because the uneven distribution of metal oxide fine particles is ensured. When heat treatment is performed after providing another layer next to the organic photoelectric conversion layer, it is difficult to make it unevenly distributed.

[Electron transport layer / hole blocking layer]
Since the organic photoelectric conversion element 10 of the present invention can take out charges generated in the bulk heterojunction layer more efficiently by forming the electron transport layer 18 between the bulk heterojunction layer and the cathode. It is preferable to have this layer.

  As the electron transport layer 18, octaazaporphyrin, a p-type semiconductor perfluoro product (perfluoropentacene, perfluorophthalocyanine, etc.) can be used. Similarly, a p-type organic semiconductor material used for a bulk heterojunction layer is used. The electron transport layer having a HOMO level deeper than the HOMO level is given a hole blocking function having a rectifying effect so that holes generated in the bulk heterojunction layer do not flow to the cathode side. More preferably, a material deeper than the HOMO level of the n-type semiconductor is used as the electron transport layer. Moreover, it is preferable to use a compound with high electron mobility from the characteristic of transporting electrons.

  Such an electron transport layer is also called a hole blocking layer, and it is preferable to use an electron transport layer having such a function. Examples of such materials include phenanthrene compounds such as bathocuproine, n-type semiconductor materials such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and titanium oxide. N-type inorganic oxides such as zinc oxide and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used. A layer made of a single n-type organic semiconductor material used for the bulk heterojunction layer can also be used.

  The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

[Hole Transport Layer / Electron Blocking Layer]
In the organic photoelectric conversion element 10 of the present invention, the hole transport layer 17 can be taken out between the bulk heterojunction layer and the anode, and charges generated in the bulk heterojunction layer can be taken out more efficiently. It is preferable to have.

  As a material constituting these layers, for example, as the hole transport layer 17, PEDOT such as trade name BaytronP, polyaniline and its doping material, a cyanide compound described in WO2006 / 019270, etc. Etc. can be used. Note that the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the bulk heterojunction layer has a rectifying effect that prevents electrons generated in the bulk heterojunction layer from flowing to the anode side. It has an electronic block function. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function. As such a material, a triarylamine compound described in JP-A-5-271166 or a metal oxide such as molybdenum oxide, nickel oxide, or tungsten oxide can be used. A layer made of a single p-type semiconductor material used for the bulk heterojunction layer can also be used.

  The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method. Forming the coating film in the lower layer before forming the bulk heterojunction layer is preferable because it has the effect of leveling the coating surface and reduces the influence of leakage and the like.

[Other layers]
For the purpose of improving energy conversion efficiency and improving the lifetime of the element, a structure having various intermediate layers in the element may be employed. Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer. Further, a layer such as a silane coupling agent may be provided in order to make the metal oxide fine particles unevenly distributed in the upper layer more stable. Further, a metal oxide layer may be laminated adjacent to the bulk heterojunction organic photoelectric conversion layer of the present invention.

〔electrode〕
The organic photoelectric conversion element of the present invention has at least an anode and a cathode. Further, when a tandem configuration is adopted, the tandem configuration can be achieved by using an intermediate electrode. In the present invention, an electrode through which holes mainly flow is called an anode, and an electrode through which electrons mainly flow is called a cathode.

  Further, because of the function of whether or not there is a light-transmitting property, a light-transmitting electrode may be called a transparent electrode, and a non-light-transmitting electrode may be called a counter electrode. Usually, the anode is a translucent transparent electrode, and the cathode is a non-translucent counter electrode.

(anode)
The anode of the present invention is preferably an electrode that transmits light of 380 to 800 nm. As the material, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires and carbon nanotubes can be used.

  Also, a conductive material selected from the group consisting of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and polynaphthalene. A functional polymer can also be used. Further, a plurality of these conductive compounds can be combined to form an anode.

(cathode)
The cathode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination. As a conductive material for the cathode, a material having a work function (4 eV or less) metal, alloy, electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the viewpoint of electron extraction performance and durability against oxidation, etc., a mixture of these metals and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, magnesium / Aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

  If a metal material is used as the conductive material of the cathode, the light coming to the cathode side is reflected and reflected to the first electrode side, and this light can be reused and absorbed again by the photoelectric conversion layer, further improving the photoelectric conversion efficiency. It is preferable.

  The cathode may be a metal (eg, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon nanoparticles, nanowires, or nanostructures. If it is a thing, a transparent and highly conductive cathode can be formed by the apply | coating method, and it is preferable.

  When the cathode side is made light transmissive, for example, a conductive material suitable for the cathode, such as aluminum and aluminum alloy, silver and silver compound, is formed with a thin film thickness of about 1 to 20 nm, and By providing a film of the conductive light-transmitting material mentioned in the description, a light-transmitting cathode can be obtained.

(Intermediate electrode)
In addition, the material of the intermediate electrode (charge recombination layer) required in the case of the tandem configuration as shown in FIG. 3 is preferably a layer using a compound having both transparency and conductivity. Materials used (transparent metal oxides such as ITO, AZO, FTO, and titanium oxide, very thin metal layers such as Ag, Al, and Au, or layers containing nanoparticles / nanowires, PEDOT: PSS, polyaniline, etc. Or the like can be used.

  In addition, in the hole transport layer and the electron transport layer described above, there is also a combination that works as an intermediate electrode (charge recombination layer) by appropriately combining and laminating, and with such a configuration, the process of forming one layer This is preferable because it can be omitted.

〔substrate〕
When light that is photoelectrically converted enters from the substrate side, the substrate is preferably a member that can transmit the light that is photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. As the substrate, for example, a glass substrate, a resin substrate and the like are preferably mentioned, but it is desirable to use a transparent resin film from the viewpoint of light weight and flexibility.

  There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things. For example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~800nm), can be preferably applied to a transparent resin film according to the present invention. Among these, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy adhesion layer in order to ensure the wettability and adhesiveness of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  Further, for the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

(Optical function layer)
The organic photoelectric conversion element of the present invention may have various optical functional layers for the purpose of more efficient reception of sunlight. As the optical functional layer, for example, a light condensing layer such as an antireflection film or a microlens array, a light diffusion layer that can scatter the light reflected by the cathode and enter the power generation layer again may be provided. .

  Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

  As the condensing layer, for example, it is processed so as to provide a structure on the microlens array on the sunlight receiving side of the support substrate, or the amount of light received from a specific direction is increased by combining with a so-called condensing sheet. Conversely, the incident angle dependency of sunlight can be reduced.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it is smaller than this, the effect of diffraction is generated and colored.

  Examples of the light scattering layer include various antiglare layers, layers in which nanoparticles or nanowires such as metals or various inorganic oxides are dispersed in a colorless and transparent polymer, and the like.

[Patterning]
The method and process for patterning the electrode, the power generation layer, the hole transport layer, the electron transport layer, and the like according to the present invention are not particularly limited, and known methods can be appropriately applied.

  If it is a soluble material such as a bulk heterojunction layer and a transport layer, only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc., or direct patterning at the time of coating using a method such as an ink jet method or screen printing. May be.

  In the case of an insoluble material such as an electrode material, the electrode can be patterned by a known method such as mask vapor deposition during vacuum deposition or etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

[Sealing]
Moreover, since the produced organic photoelectric conversion element is not deteriorated by oxygen, moisture, or the like in the environment, it is preferable to seal not only the organic photoelectric conversion element but also an organic electroluminescence element by a known method. For example, a method of sealing a cap made of aluminum or glass by bonding with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed and an organic photoelectric conversion element are pasted with an adhesive. Method, spin coating of organic polymer material (polyvinyl alcohol, etc.) with high gas barrier property, inorganic thin film (silicon oxide, aluminum oxide, etc.) or organic film (parylene etc.) with high gas barrier property are deposited under vacuum Examples thereof include a method and a method of laminating these in a composite manner.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1:
[Production of Organic Photoelectric Conversion Element 1]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 110 nm (sheet resistance 13 Ω / □) is patterned to a width of 2 mm using a normal photolithography technique and hydrochloric acid etching, and transparent An electrode was formed.

  The patterned transparent electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning. On this transparent substrate, a conductive polymer Baytron P4083 (PEDOT-PSS (poly (3,4-ethylenedioxythiophene) -poly (stylensulfonate)) aqueous dispersion manufactured by Starck Vitec Co., Ltd.) is spin-coated at a film thickness of 30 nm. After that, it was dried by heating at 140 ° C. in the atmosphere for 10 minutes.

  After this, the substrate was brought into the glove box and operated under a nitrogen atmosphere. First, the substrate was heat-treated at 140 ° C. for 3 minutes in a nitrogen atmosphere.

As a p-type organic semiconductor material mixed with chlorobenzene, P3HT (manufactured by Plectotronics, Plexcore OS2100) at 1.0% by mass and PCBM (manufactured by Frontier Carbon) at 1.0% by mass as an n-type semiconductor material, A liquid in which 10% by mass of tin oxide (SnO ₂ ) particles (average primary particle size 25 nm) was dispersed with respect to the total amount of P3HT and PCBM was prepared, and stirred (60 minutes) while heating to 70 ° C. in an oven. And PCBM were dissolved and cooled to room temperature. While this solution was filtered through a 0.2 μm filter, spin coating was performed at 700 rpm for 60 seconds and then at 2000 rpm for 2 seconds to obtain a photoelectric conversion layer having a thickness of 100 nm. Thereafter, an annealing treatment was performed at 150 ° C. for 5 minutes to form a photoelectric conversion layer.

A cross-sectional TEM image is shown in FIG. It is clear that the tin oxide (SnO ₂ ) particles are not dispersed in the photoelectric conversion layer and are unevenly distributed in the vicinity of both surfaces with respect to the normal direction composed of the plane of the positive electrode or the negative electrode. In addition, it is unevenly distributed on the lower surface, and when the SnO ₂ content decreases, it can be easily predicted that it is unevenly distributed only on the lower side.

Next, the substrate on which the organic layer was formed was placed in a vacuum evaporation apparatus. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 0.5 nm of lithium fluoride and 80 nm of Al were evaporated. The vapor deposition rate was 2 nm / second for vapor deposition, and the organic photoelectric conversion element 1 having a light receiving part size of 2 mm square was obtained.

  The obtained organic photoelectric conversion element 1 was sealed using an aluminum cap and a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) in a nitrogen atmosphere.

[Production of organic photoelectric conversion elements 2 to 9]
As shown in Table 1, organic photoelectric conversion elements 2 to 9 were obtained in the same manner as the organic photoelectric conversion element 1 except that the addition amount of the metal oxide fine particles and the annealing treatment temperature of the photoelectric conversion layer were changed.

[Production of organic photoelectric conversion elements 10 to 18]
As shown in Table 1, the organic photoelectric conversion elements 10 to 18 were changed in the same manner as the organic photoelectric conversion elements 1 to 9 except that the metal oxide fine particles were changed to titanium oxide (TiO ₂ ) particles (average primary particle size 15 nm). Obtained.

The cross-sectional TEM image after forming even the photoelectric converting layer of the organic photoelectric conversion element 10 in FIG. 5 is shown. It is clear that the titanium oxide (TiO ₂ ) particles are not dispersed in the photoelectric conversion layer and are unevenly distributed in the vicinity of both surfaces with respect to the normal direction composed of the plane of the positive electrode or the negative electrode. Moreover, it is unevenly distributed on the upper surface and the lower surface in the same manner, and it can be easily predicted that it is unevenly distributed on both sides even if the TiO ₂ content decreases.

[Production of Organic Photoelectric Conversion Elements 19-22]
As shown in Table 1, the metal oxide fine particles are made of aluminum / zinc oxide (AZO) particles (average primary particle size 25 nm), indium / tin oxide (ITO) particles (average primary particle size 25 nm), gallium / zinc. From the organic photoelectric conversion element 19 in the same manner as the organic photoelectric conversion element 1 except that the oxide (GZO) particles (average primary particle diameter 25 nm) and zirconium oxide (ZrO ₂ ) particles (average primary particle diameter 25 nm) were changed. 22 was obtained.

[Production of Organic Photoelectric Conversion Element 23]
As shown in Table 1, after applying the photoelectric conversion layer, the organic photoelectric conversion element 11 was treated in the same manner as the organic photoelectric conversion element 11 except that it was dried in a vacuum thermostat at 80 ° C. for 60 minutes as described in JP2009-158730A. A conversion element 23 was obtained.

[Production of Organic Photoelectric Conversion Element 24]
As shown in Table 1, an organic photoelectric conversion element 24 was obtained in the same manner as the organic photoelectric conversion element 1 except that the metal oxide fine particles were not added to the photoelectric conversion layer.

[Evaluation of photoelectric conversion efficiency]
The photoelectric conversion element sealed prepared above, was irradiated with light having an intensity of 100 mW / cm ² solar simulator (AM1.5G filter), a superposed mask in which the effective area 4.0 mm ² on the light receiving portion, the short circuit current The density Jsc (mA / cm ² ), the open circuit voltage Voc (V), and the fill factor (fill factor) FF were measured for each of the four light receiving portions formed on the same element, and the average value was obtained. Further, energy conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1. The results are shown in Table 1. It shows that energy conversion efficiency (photoelectric conversion efficiency) is so favorable that a number is large.

Formula 1 Jsc (mA / cm ² ) × Voc (V) × FF = η (%)
[Durability evaluation of photoelectric conversion efficiency]
A solar simulator (AM1.5G) was irradiated at an irradiation intensity of 100 mW / cm ² , voltage-current characteristics were measured, and conversion efficiency before exposure was measured. Further, with the resistor connected between the anode and the cathode, the solar simulator (AM1.5G) was irradiated with 100 times the irradiation intensity of 1000 mW / cm ² for 10 hours, and then the solar simulator (AM1.5G) Light was irradiated at an irradiation intensity of 100 mW / cm ² , voltage-current characteristics were measured, and conversion efficiency after exposure was measured. The relative efficiency reduction of the conversion efficiency was calculated from Equation 2. The results are shown in Table 1. It shows that durability of energy conversion efficiency (durability of photoelectric conversion efficiency) is so favorable that a number is small.

Formula 2 Reduction in relative efficiency of conversion efficiency (%)
= (1-conversion efficiency after exposure / conversion efficiency before exposure) × 100

  From Table 1, it can be seen that the photoelectric conversion element of the configuration and the manufacturing method according to the present invention can improve the conversion efficiency by improving Jsc, and can also improve the durability (durability of the conversion efficiency).

Example 2:
[Production of Organic Photoelectric Conversion Elements 25-30]
As shown in Table 2, organic photoelectric conversion elements 25 to 30 were obtained in the same manner as in the organic photoelectric conversion element 2 or 11 except that the average particle diameter of the metal oxide fine particles was changed. Evaluation similar to Example 1 was performed. The results are shown in Table 2.

  From Table 2, it can be seen that the photoelectric conversion element of the configuration and the manufacturing method according to the present invention can improve the conversion efficiency by improving Jsc, and can also improve the durability (durability of the conversion efficiency).

Example 3:
[Production of Organic Photoelectric Conversion Element 31]
As shown in Table 3, an organic photoelectric conversion element 31 was obtained in the same manner as the organic photoelectric conversion element 10 except that the addition amount of titanium oxide (TiO ₂ ) particles (average primary particle diameter 15 nm) was changed.

[Production of Organic Photoelectric Conversion Element 32]
After applying the photoelectric conversion layer, an organic photoelectric conversion element 32 was obtained in the same manner as the organic photoelectric conversion element 31 except that it was dried in a vacuum thermostat at 80 ° C. for 60 minutes as described in JP-A-2009-158730.

[Production of Organic Photoelectric Conversion Element 33]
As shown below, after the photoelectric conversion layer not containing metal oxide fine particles, a photoelectric conversion layer containing metal oxide fine particles was applied as described in Example 1 of JP-A-2009-158730.

  An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 110 nm (sheet resistance 13 Ω / □) is patterned to a width of 2 mm using a normal photolithography technique and hydrochloric acid etching, and transparent An electrode was formed.

  The patterned transparent electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning. On this transparent substrate, a conductive polymer Baytron P4083 (PEDOT-PSS (poly (3,4-ethylenedioxythiophene) -poly (stylensulfonate)) aqueous dispersion manufactured by Starck Vitec Co., Ltd.) is spin-coated at a film thickness of 30 nm. After that, it was dried by heating at 140 ° C. in the atmosphere for 10 minutes.

  After this, the substrate was brought into the glove box and operated under a nitrogen atmosphere. First, the substrate was heat-treated at 140 ° C. for 3 minutes in a nitrogen atmosphere.

  A solution is prepared by mixing 1.0% by mass of P3HT (Plectotronics, Plexcore OS2100) as p-type organic semiconductor material and 1.0% by mass of PCBM (frontier carbon) as n-type semiconductor material in chlorobenzene. The mixture was stirred (60 minutes) while being heated to 70 ° C. in an oven to dissolve P3HT and PCBM, and then cooled to room temperature. While this solution was filtered with a 0.2 μm filter, spin coating was performed at 2000 rpm for 62 seconds to obtain a photoelectric conversion layer having a thickness of 50 nm. Then, it dried for 60 minutes in an 80 degreeC vacuum thermostat, and formed the photoelectric converting layer.

Next, P3HT (Plextronics, Plexcore OS2100) as a p-type organic semiconductor material was mixed with chlorobenzene at 1.0% by mass, and PCBM (Frontier Carbon) as an n-type semiconductor material was mixed at 1.0% by mass. Then, a liquid in which 2% by mass of titanium oxide (TiO ₂ ) particles (average primary particle size 15 nm) are dispersed with respect to the total amount of P3HT and PCBM is prepared, and stirred (60 minutes) while heating to 70 ° C. in an oven. P3HT and PCBM were dissolved and cooled to room temperature. While this solution was filtered with a 0.2 μm filter, spin coating was performed at 2000 rpm for 62 seconds to obtain a photoelectric conversion layer having a thickness of 50 nm. Then, it dried for 60 minutes in an 80 degreeC vacuum thermostat, and formed the photoelectric converting layer by 2 layer application | coating.

  After forming the photoelectric conversion layer, the organic photoelectric conversion element 33 was obtained in the same manner as in Example 1.

[Preparation of Organic Photoelectric Conversion Element 34]
An organic photoelectric conversion element 34 was obtained in the same manner as the organic photoelectric conversion element 33 except that the heat treatment of the first photoelectric conversion layer was changed to an annealing treatment at 150 ° C. for 5 minutes.

[Production of Organic Photoelectric Conversion Element 35]
An organic photoelectric conversion element 35 was obtained in the same manner as the organic photoelectric conversion element 34 except that the heat treatment of the second photoelectric conversion layer was changed to an annealing process at 150 ° C. for 5 minutes.

  Evaluation similar to Example 1 was performed. The results are shown in Table 3.

  From Table 3, it can be seen that the photoelectric conversion element of the configuration and the manufacturing method according to the present invention can improve the conversion efficiency by improving Jsc, and can also improve the durability (durability of the conversion efficiency).

Example 4:
[Production of Organic Photoelectric Conversion Element 36]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 110 nm (sheet resistance 13 Ω / □) is patterned to a width of 2 mm using a normal photolithography technique and hydrochloric acid etching, and transparent An electrode was formed.

  The patterned transparent electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning. After this, the substrate was brought into the glove box and operated under a nitrogen atmosphere.

  On this transparent substrate, a mixed solution of polyethyleneimine dissolved in isopropanol and glycerol propoxylate triglycidyl ether was applied, spin-coated with a film thickness of 30 nm, dried on a hot plate at 120 ° C. for 10 minutes, and then transported by electrons. Layers were formed.

As a p-type organic semiconductor material mixed with chlorobenzene, P3HT (manufactured by Plectotronics, Plexcore OS2100) at 1.0% by mass and PCBM (manufactured by Frontier Carbon) at 1.0% by mass as an n-type semiconductor material, A liquid in which 10% by mass of tin oxide (SnO ₂ ) particles (average primary particle size 25 nm) was dispersed with respect to the total amount of P3HT and PCBM was prepared, and stirred (60 minutes) while heating to 70 ° C. in an oven. And PCBM were dissolved and cooled to room temperature. While this solution was filtered through a 0.2 μm filter, spin coating was performed at 700 rpm for 60 seconds and then at 2000 rpm for 2 seconds to obtain a photoelectric conversion layer having a thickness of 100 nm. Thereafter, an annealing treatment was performed at 150 ° C. for 5 minutes to form a photoelectric conversion layer.

  Next, Baytron P4083 (an aqueous dispersion of PEDOT-PSS (poly (3,4-ethylenedithiophene) -poly (styreneenesulfate)) manufactured by Starck Vitec), which is a conductive polymer, is spin-coated at a film thickness of 100 nm, and then 140 Heat drying at 10 ° C. for 10 minutes.

Next, the substrate on which the organic layer was formed was placed in a vacuum evaporation apparatus. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 80 nm of Ag was deposited. The vapor deposition rate was 2 nm / second, and an organic photoelectric conversion element 36 having a light receiving portion with a size of 2 mm square was obtained.

[Production of organic photoelectric conversion elements 37 to 44]
As shown in Table 4, organic photoelectric conversion elements 37 to 34 were obtained in the same manner as the organic photoelectric conversion element 36 except that the addition amount of the metal oxide fine particles and the annealing treatment temperature of the photoelectric conversion layer were changed.

[Production of Organic Photoelectric Conversion Elements 45-53]
As shown in Table 4, organic photoelectric conversion elements 45 to 53 were obtained in the same manner as the organic photoelectric conversion elements 36 to 44 except that the metal oxide fine particles were changed to titanium oxide (TiO 2) particles (average primary particle diameter 15 nm). It was.

[Production of Organic Photoelectric Conversion Element 54]
As shown in Table 4, after the photoelectric conversion layer was applied, the organic photoelectric conversion element 46 was treated in the same manner as the organic photoelectric conversion element 46 except that it was dried in a vacuum thermostat at 80 ° C. for 60 minutes as described in JP2009-158730A. A conversion element 54 was obtained.

[Preparation of organic photoelectric conversion element 55]
As shown in Table 4, an organic photoelectric conversion element 55 was obtained in the same manner as the organic photoelectric conversion element 36 except that the metal oxide fine particles were not added to the photoelectric conversion layer.

  Evaluation similar to Example 1 was performed. The results are shown in Table 4.

  From Table 4, it can be seen that the photoelectric conversion element of the configuration and the manufacturing method according to the present invention can improve the conversion efficiency by improving Jsc, and can also improve the durability (durability of the conversion efficiency).

Example 5:
[Production of Organic Photoelectric Conversion Element 56]
An indium tin oxide (ITO) transparent conductive film deposited on a PET substrate with a thickness of 150 nm (sheet resistance 12 Ω / □) is patterned to a width of 10 mm using a normal photolithography technique and wet etching. An electrode was formed. The patterned first electrode was washed in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried by nitrogen blowing, and finally subjected to ultraviolet ozone cleaning. After this, the substrate was brought into the glove box and operated under a nitrogen atmosphere.

  On this transparent substrate, a mixed solution of polyethyleneimine dissolved in isopropanol and glycerol propoxylate triglycidyl ether was applied and dried using a blade coater so that the dry film thickness was about 400 nm. Thereafter, heat treatment was performed at 120 ° C. for 10 minutes to form an electron transport layer.

  As a p-type organic semiconductor material mixed with chlorobenzene, P3HT (manufactured by Plectotronics, Plexcore OS2100) at 1.0% by mass and PCBM (manufactured by Frontier Carbon) at 1.0% by mass as an n-type semiconductor material, A liquid in which 10% by mass of tin oxide (SnO2) particles (average primary particle size 25 nm) is dispersed with respect to the total amount of P3HT and PCBM is prepared, and stirred (60 minutes) while heating to 70 ° C. in an oven. After the PCBM was dissolved, it was cooled to room temperature. This solution was filtered with a 0.2 μm filter, applied with a blade coater so that the dry film thickness was about 100 nm, and immediately dried with 110 ° C. dry air for 60 seconds to obtain a photoelectric conversion layer. .

Subsequently, as a hole transport layer, PEDOT-PSS (CLEVIOS (registered trademark) PVP AI 4083, manufactured by HC Starck Co., Ltd., made of conductive polymer and polyanion, conductivity 1 × 10 ⁻³ S / cm ), And a liquid containing isopropanol was prepared, and applied and dried using a blade coater so that the dry film thickness was about 100 nm. Thereafter, heat treatment was performed at 150 ° C. for 10 minutes to form a hole transport layer.

Next, the substrate on which the series of functional layers is formed is moved into a vacuum deposition apparatus chamber, the pressure inside the vacuum deposition apparatus is reduced to 1 × 10 ⁻⁴ Pa or less, and then the deposition rate is 5.0 nm / second. A second electrode was formed by laminating 200 nm of Ag metal. The obtained organic photoelectric conversion element was moved to a nitrogen chamber and sealed using a sealing cap and a UV curable resin, whereby an organic photoelectric conversion element 56 having a light receiving portion of about 10 × 10 mm size was obtained.

[Preparation of organic photoelectric conversion elements 57 to 58]
As shown in Table 5, organic photoelectric conversion elements 57 to 58 were obtained in the same manner as the organic photoelectric conversion element 56 except that the drying air temperature after application of the photoelectric conversion layer was changed.

[Production of organic photoelectric conversion elements 59 to 61]
As shown in Table 5, the organic photoelectric conversion elements 59 to 61 were changed in the same manner as the organic photoelectric conversion elements 56 to 58 except that the metal oxide fine particles were changed to titanium oxide (TiO ₂ ) particles (average primary particle diameter 15 nm). Obtained.

  Evaluation similar to Example 1 was performed. The results are shown in Table 5.

  From Table 5, it can be seen that the photoelectric conversion element of the manufacturing method according to the present invention can improve the conversion efficiency and improve the durability (durability of the conversion efficiency) by improving Jsc.

Example 6:
[Production of Organic Photoelectric Conversion Element 62]
In production of the photoelectric conversion element 11, after vapor deposition of Al, an additional annealing treatment was performed at 150 ° C. for 5 minutes to obtain an organic photoelectric conversion element 62.

[Production of Organic Photoelectric Conversion Element 63]
In production of the photoelectric conversion element 18, after vapor deposition of Al, an additional annealing treatment was performed at 150 ° C. for 5 minutes to obtain an organic photoelectric conversion element 63.

[Production of Organic Photoelectric Conversion Element 64]
In preparation of the photoelectric conversion element 24, after vapor-depositing Al, an additional annealing treatment was performed at 150 ° C. for 5 minutes to obtain an organic photoelectric conversion element 64.

  Evaluation similar to Example 1 was performed. The results are shown in Table 5.

  It can be seen from Table 6 that the photoelectric conversion element of the manufacturing method according to the present invention can improve the conversion efficiency and improve the durability (durability of the conversion efficiency) by improving Jsc.

DESCRIPTION OF SYMBOLS 10 Organic photoelectric conversion element 11 Substrate 12 Transparent electrode 13 Counter electrode 14, 14 'Photoelectric conversion layer 15 Charge recombination layer 16 2nd photoelectric conversion layer 17 Hole transport layer 18 Electron transport layer 101 ITO glass substrate 102 PEDOT-PSS layer 103 Photoelectric conversion layer 104 Protective layer for obtaining TEM observation sample

Claims (6)

At least a first electrode on the substrate, an organic photoelectric conversion layer containing a p-type organic semiconductor material having an electron donating property, an n-type organic semiconductor material having an electron accepting property, and metal oxide fine particles, and a second electrode In the manufacturing method of the organic photoelectric conversion element having,
In the step of forming the organic photoelectric conversion layer, a coating liquid containing the p-type organic semiconductor material and the n-type organic semiconductor material and in which metal oxide fine particles are dispersed is applied onto the electrode to form a layer. Thereafter, the metal oxide fine particles are unevenly distributed in the normal direction with respect to the surface of the organic photoelectric conversion layer by performing a heat treatment at 90 ° C. or higher to increase the concentration of the metal oxide fine particles in the vicinity of at least one surface. The manufacturing method of the organic photoelectric conversion element characterized by these.   The step of forming the organic photoelectric conversion layer is performed at 90 ° C. or higher after applying a coating liquid containing the p-type organic semiconductor material and the n-type organic semiconductor material and in which metal oxide fine particles are dispersed on the electrode. The method for producing an organic photoelectric conversion element according to claim 1, wherein the layer is formed by drying at a temperature of 5 μm.   The organic photoelectric conversion element according to claim 1, wherein the metal oxide fine particles are unevenly distributed in the vicinity of both surfaces of the organic photoelectric conversion layer.   4. The organic photoelectric conversion element according to claim 2, wherein an average primary particle size of the metal oxide fine particles is 30% or less with respect to a film thickness of the photoelectric conversion layer.   The content of the metal oxide fine particles is 0.5 mass% or more and 10 mass% or less with respect to the total of the p-type organic semiconductor material and the n-type organic semiconductor material. The organic photoelectric conversion element as described in 2.   A solar cell comprising the organic photoelectric conversion device according to any one of claims 3 to 5.