WO2012005116A1

WO2012005116A1 - Organic photoelectric conversion element and method for manufacturing same

Info

Publication number: WO2012005116A1
Application number: PCT/JP2011/064378
Authority: WO
Inventors: 伊東　宏明; 野島　隆彦; 伊藤　博英
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2010-07-06
Filing date: 2011-06-23
Publication date: 2012-01-12
Also published as: JPWO2012005116A1; JP5700044B2

Abstract

Disclosed are: an organic photoelectric conversion element which has improved short-circuit current density (Jsc) by reducing the optical loss of a charge transport layer, while achieving excellent fill factor (FF) by reducing damage to the charge transport layer during the formation of a counter electrode and suppressing leakage; and a method for manufacturing the organic photoelectric conversion element. Specifically disclosed is an organic photoelectric conversion element which comprises, between a first electrode and a second electrode, at least a power generating layer that contains a p-type semiconductor material and an n-type semiconductor material and a charge transport layer that mainly transports either holes or electrons. The organic photoelectric conversion element is characterized in that the charge transport layer contains a polymer (A) that has at least one unit structure selected from the three unit structures described below.

Description

Organic photoelectric conversion element and manufacturing method thereof

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

An organic solar cell (organic photoelectric conversion element) has a power generation layer including a p-type semiconductor and an n-type semiconductor on a transparent electrode, and a charge transport layer that transports generated charges to the electrode, and is formed by light absorption. It is characterized in that the charge is efficiently separated before the child is deactivated, and the generated charges can be taken out to the electrode.

The power generation layer and the charge transport layer need to be designed to have optimum film thicknesses in consideration of the light absorption efficiency and the charge transport resistance of the layer itself. In particular, it is important to utilize optical interference between the transparent electrode and the counter electrode, and it is necessary to design the film thickness so that the electric field strength distribution of light is optimized for the power generation layer. ITO (tin-doped indium oxide) is generally used for the transparent electrode of the organic solar cell, and since the refractive index is high, the light reflected by the counter electrode is reflected back to the power generation layer side. By designing the electric field strength of light optimally, the apparent optical path length of the power generation layer can be obtained, and higher light absorption efficiency can be obtained even with a thin film.

However, there is a problem that light loss occurs due to light absorption in a charge transport layer that does not contribute to power generation while light reciprocates between the electrodes. If the charge transport layer is designed to be thin in order to reduce optical loss, the above-mentioned electric field strength distribution may greatly deviate from the power generation layer, or the layer may be too thin to cause leakage between the electrode and the power generation layer. There was a problem that stable power generation efficiency could not be obtained.

In addition, the above-mentioned metal electrode is generally formed by vapor deposition, sputtering, printing, or the like. When contacting the metal cluster evaporated at that time or a printing plate, the charge transport layer is formed. It has also been a problem that a part of the electrode is destroyed and causes leakage between the electrode and the power generation layer or between the electrodes. To deal with such problems, if the thickness of the charge transport layer is made too thick, not only the optical loss as described above increases, but also the increase in resistance due to the increase in film thickness causes a decrease in performance, resulting in a technical trade-off. It was.

In response to such a problem, for example, by providing an optical spacer layer having a charge transport property between the power generation layer and the electrode, the optical electric field strength of the power generation layer is increased and the optical effect is positively enhanced (for example, patent Reference 1), a method of reducing the resistance of the charge transport layer itself by adding a small amount of an agent having hydroxyls, and reducing resistance increase due to thickening (for example, see Patent Document 2), A method of reducing damage to the charge transport layer by producing a metal electrode by a glow discharge method (see, for example, Patent Document 3), an organic charge transport layer later on an anode and a cathode previously produced on the same substrate. The method of laminating (see, for example, Patent Document 4) has been introduced.

However, in any of the above-mentioned solutions, sufficient reduction in optical loss of the charge transport layer and reduction in damage during electrode formation cannot be achieved without extremely reducing the membrane resistance, and sufficient performance can be obtained. It was not done.

Special table 2008-533745 Special table 2010-508430 gazette Japanese Patent Laid-Open No. 9-92863 JP 2004-152786 A

The object of the present invention is to reduce the optical loss of the charge transport layer and improve the short circuit current density (Jsc), reduce the damage of the charge transport layer when forming the counter electrode, and have an excellent fill factor (FF) due to the leak suppression effect. It is in providing an organic photoelectric conversion element and its manufacturing method.

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

1. Organic having at least a power generation layer including a p-type semiconductor material and an n-type semiconductor material and a charge transport layer mainly transporting either holes or electrons between the first electrode and the second electrode In the photoelectric conversion element, the charge transport layer contains a polymer (A) having at least one selected from the following three unit structures.

(In the formula, X represents a hydrogen atom or a methyl group, R ₁ to R ₃ each independently represents a linear or branched alkylene group having 1 to 5 carbon atoms. L, m, and n represent the polymer (A ) Represents the respective composition ratio (mol%) when the total number of moles of all monomers constituting 100 is 100, and 50 ≦ l + m + n ≦ 100.)
2. 2. The organic photoelectric conversion device according to 1, wherein the charge transport layer contains at least the polymer (A), a π-conjugated polymer, and a polyanion.

3. 3. The organic photoelectric conversion device as described in 1 or 2 above, wherein the solid content ratio of the polymer (A) in the charge transport layer is 10% by mass to 90% by mass.

4. Any one of the above 1 to 3, wherein the charge transport layer has an elastic modulus measured by a nanoindentation method after a heat treatment step of the polymer (A) and the polyanion is 4 GPa or more and 10 GPa or less. The organic photoelectric conversion element of 1 item | term.

5. 5. The organic photoelectric conversion element according to any one of 1 to 4, wherein the organic photoelectric conversion element is produced by a heat treatment step of the polymer (A) and the polyanion after forming the charge transport layer. A method for manufacturing a conversion element.

According to the present invention, it was possible to provide an organic photoelectric conversion element that achieves an excellent short-circuit current density and a fill factor, and has excellent durability at high temperatures and high humidity, and a method for manufacturing the same.

It is the figure which illustrated the photoelectric conversion element of this invention.

As a result of intensive studies, the present inventors have mainly used a power generation layer including a p-type semiconductor material and an n-type semiconductor material and either a hole or an electron between the first electrode and the second electrode. An organic photoelectric conversion device having at least a charge transport layer for transporting to the surface, wherein the charge transport layer includes the polymer (A), thereby providing an organic photoelectric conversion device, which is excellent for the problems described above. I found that it was a solution.

Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

(Configuration of organic photoelectric conversion element and solar cell)
The organic photoelectric conversion element of the present invention includes a first electrode, a second electrode, and a power generation layer sandwiched between them (a layer in which a p-type semiconductor and an n-type semiconductor are mixed, a bulk heterojunction layer, or a BHJ layer) , Also referred to as i layer), and is an element that generates current when irradiated with light.

Although the preferable form of the organic photoelectric conversion element concerning this invention is demonstrated using FIG. 1, it is not limited to this.

FIG. 1 is a diagram schematically showing a cross-sectional structure of a preferred photoelectric conversion element of the present invention.

In FIG. 1, the photoelectric conversion element 10 includes a first electrode 101, a hole blocking layer (or electron transport layer) 102, a power generation layer 103, (a p-type semiconductor material 103 a and an n-type semiconductor material 103 b) on a substrate (not shown). (Bulk heterojunction structure) The electron blocking layer (or hole transport layer) 104 and the second electrode 105 are stacked.

In the organic photoelectric conversion element, at least one of the first electrode 101 and the second electrode 105 described above is a transparent electrode. However, in the present invention, the effect can be obtained when either is transparent or both are transparent. Further, the polymer (A) is included in a charge transport layer (at least one of an electron transport layer and a hole transport layer) that comes into contact with the electrode side to be formed later.

Furthermore, in the present invention, it is more preferable that the charge transport layer contains at least the polymer (A), a π-conjugated polymer, and a polyanion.

[Polymer (A)]
The photoelectric conversion element of the present invention is characterized by having at least a charge transport layer between the first electrode and the second electrode, and further comprising the polymer (A) in the charge transport layer. Features.

In the present invention, by including the polymer (A) in the charge transport layer, it is possible to improve the transmittance without reducing the conductivity of the film, and the performance is lowered even if the film is made thicker. This makes it possible to suppress damage to electrode formation, which is a preferred embodiment.

As specific examples of the polymer (A) preferably used in the present invention, in the polymer (A), X represents a hydrogen atom or a methyl group, and R ₁ to R ₃ are each independently a straight chain having 1 to 5 carbon atoms or Represents a branched alkylene group. l, m, and n represent respective constituent ratios (mol%) when the total number of moles of all monomers constituting the polymer (A) is 100, and 50 ≦ l + m + n ≦ 100 is preferable. . The composition ratio is more preferably in the range of 70 ≦ m ≦ 100.

In the present invention, it is preferable to use a hydrophilic polymer binder which is a polymer that can be dissolved or dispersed in an aqueous solvent (described later) in combination with the polymer (A). Examples thereof include polyester resins, acrylic resins, polyurethane resins, acrylic urethane resins, polycarbonate resins, cellulose resins, polyvinyl acetal resins, polyvinyl alcohol resins, and the like. Specific examples of the compound include Vylonal MD1200, MD1400, MD1480 (manufactured by Toyobo Co., Ltd.) as polyester resins.

As the hydrophilic polymer binder according to the present invention, a compound having a group that reacts with a cross-linking agent described later is more preferable because a stronger film is formed. As such a hydrophilic polymer binder, a group that reacts with the crosslinking agent varies depending on the crosslinking agent, and examples thereof include a hydroxy group, a carboxyl group, and an amino group. Among these, it is most preferable to have a hydroxy group in the side chain.

Specific examples of the hydrophilic polymer binder according to the present invention include polyvinyl alcohol PVA-203, PVA-224, PVA-420 (manufactured by Kureha), hydroxypropylmethylcellulose 60SH-06, 60SH-50, 60SH. -4000, 90SH-100 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), methylcellulose SM-100 (produced by Shin-Etsu Chemical Co., Ltd.), cellulose acetate L-20, L-40, L-70 (above, manufactured by Daicel Chemical Industries, Ltd.) Carboxymethylcellulose CMC-1160 (manufactured by Daicel Chemical Industries, Ltd.), hydroxyethyl cellulose SP-200, SP-600 (manufactured by Daicel Chemical Industries, Ltd.), alkyl acrylate copolymer Jurimer AT-210, AT-510 (above, Manufactured by Toagosei Co., Ltd.), polyhydroxyethyl Acrylate, may be mentioned poly-hydroxyethyl methacrylate.

When the polymer (A) is contained in a certain amount, the conductivity of the charge transport layer containing the π-conjugated polymer and the polyanion can be improved, and the compatibility with the π-conjugated polymer is good and high. Transparency and smoothness can be achieved. Furthermore, when the polyanion has a sulfo group, if the polymer (A) is used, the sulfo group effectively acts as a dehydration catalyst, and a dense cross-linked layer can be formed without using an additional agent such as a cross-linking agent. This is a more preferred embodiment because it can be formed and an improvement in film strength can be expected.

The main copolymerization component of the polymer (A) is the three unit structures contained in the polymer (A), and 50 mol% or more of the copolymerization component is any one of the three unit structures, or the 3 It is a copolymer having a total of 50 mol% of one unit structure. The polymer (A) preferably has a total of the three unit structures of 80 mol% or more, and may be a homopolymer formed from any one monomer of the three unit structures. It is an embodiment.

In the polymer (A), other monomer components may be copolymerized as long as they are soluble in an aqueous solvent, but a monomer component having high hydrophilicity is more preferable. The polymer (A) has a number average molecular weight of preferably 1000 or less and 0 to 5% or less.

The number average molecular weight of the polymer (A) is such that the content of 1000 or less is 0 to 5% or less, such as reprecipitation method, preparative GPC, synthesis of monodisperse polymer by living polymerization, etc. Methods that remove components or suppress the formation of low molecular weight components can be used. In the reprecipitation method, the polymer is dissolved in a solvent in which the polymer can be dissolved and dropped into a solvent having a lower solubility than the solvent in which the polymer is dissolved, thereby precipitating the polymer and removing low molecular weight components such as monomers, catalysts, and oligomers. It is a method to do. Further, preparative GPC can be divided by molecular weight, for example, by recycling preparative GPCLC-9100 (manufactured by Japan Analytical Industrial Co., Ltd.), polystyrene gel column, and passing the polymer-dissolved solution through the column. It is a method that can be cut. In the living polymerization, the generation of the starting species does not change with time, and there are few side reactions such as termination reaction, and a polymer having a uniform molecular weight can be obtained. Since the molecular weight can be adjusted by the amount of monomer added, for example, if a polymer having a molecular weight of 20,000 is synthesized, the production of low molecular weight substances can be suppressed. The reprecipitation method and living polymerization are preferable from the viewpoint of production suitability.

The number average molecular weight and weight average molecular weight of the polymer (A) or hydrophilic polymer binder of the present invention can be measured by generally known gel permeation chromatography (GPC). The molecular weight distribution can be expressed by a ratio of (weight average molecular weight / number average molecular weight). The solvent to be used is not particularly limited as long as the polymer (A) or the hydrophilic polymer binder is dissolved, preferably THF, DMF, CH ₂ Cl ₂ , more preferably THF, DMF, and further preferably DMF. . The measurement temperature is not particularly limited, but 40 ° C. is preferable.

The molecular weight of the polymer (A) according to the present invention is preferably in the range of 3,000 to 2,000,000 in terms of number average molecular weight, more preferably in the range of 4,000 to 500,000, still more preferably in the range of 5,000 to 100,000. is there. The molecular weight distribution of the polymer (A) is preferably from 1.01 to 1.30, more preferably from 1.01 to 1.25.

In the distribution obtained by GPC, the content with a number average molecular weight of 1000 or less was converted to a ratio by integrating the area with a number average molecular weight of 1000 or less and dividing by the area of the entire distribution.

The living radical polymerization solvent is inactive under reaction conditions and is not particularly limited as long as it can dissolve the monomer and the polymer to be formed, but a mixed solvent of an alcohol solvent and water is preferable. The living radical polymerization temperature varies depending on the initiator used, but is generally -10 to 250 ° C, preferably 0 to 200 ° C, more preferably 10 to 100 ° C.

The abundance ratio of the polymer (A) according to the present invention is preferably such that the solid content ratio in the charge transport layer is 10% by mass to 90% by mass. More preferably, it is 20% by mass to 80% by mass. If it is 10% by mass or more, the effect of improving the transmittance can be obtained without significantly lowering the conductivity, and if it is 90% by mass or less, sufficient conductivity can be maintained, which is a preferable abundance ratio in the present invention.

[Π-conjugated polymer]
The π-conjugated polymer preferably used in the present invention is not particularly limited, but is preferably a so-called conductive polymer. Furthermore, it is more preferable to have a π-conjugated polymer and a polyanion. Such a polymer can be easily produced by chemical oxidative polymerization of a precursor monomer that forms a π-conjugated polymer described later in the presence of an appropriate oxidizing agent, an oxidation catalyst, and a polyanion described later.

Examples of the π-conjugated polymer that can be used in the present invention include polythiophenes (including basic polythiophenes, the same applies hereinafter), polypyrroles, polyindoles, polycarbazoles, polyanilines, polyacetylenes, polyfurans, and polyparaffins. Chain conductive polymers such as phenylene vinylenes, polyazulenes, polyparaphenylenes, polyparaphenylene sulfides, polyisothianaphthenes, polythiazyl compounds, and the like can be used. Of these, polythiophenes and polyanilines are preferable from the viewpoints of conductivity, transparency, stability, and the like. Furthermore, polyethylenedioxythiophenes are preferable.

The precursor monomer that forms a π-conjugated polymer of the present invention has a π-conjugated system in the molecule, and even when polymerized by the action of an appropriate oxidizing agent, a π-conjugated system is formed in the main chain. Can be preferably used. Examples thereof include pyrroles and derivatives thereof, thiophenes and derivatives thereof, anilines and derivatives thereof, and the like.

Specific examples of the precursor monomer include pyrrole, 3-methylpyrrole, 3-ethylpyrrole, 3-n-propylpyrrole, 3-butylpyrrole, 3-octylpyrrole, 3-decylpyrrole, 3-dodecylpyrrole, 3, 4-dimethylpyrrole, 3,4-dibutylpyrrole, 3-carboxylpyrrole, 3-methyl-4-carboxylpyrrole, 3-methyl-4-carboxyethylpyrrole, 3-methyl-4-carboxybutylpyrrole, 3-hydroxypyrrole 3-methoxypyrrole, 3-ethoxypyrrole, 3-butoxypyrrole, 3-hexyloxypyrrole, 3-methyl-4-hexyloxypyrrole, thiophene, 3-methylthiophene, 3-ethylthiophene, 3-propylthiophene, 3 -Butylthiophene, 3-hexyl Offene, 3-heptylthiophene, 3-octylthiophene, 3-decylthiophene, 3-dodecylthiophene, 3-octadecylthiophene, 3-bromothiophene, 3-chlorothiophene, 3-iodothiophene, 3-cyanothiophene, 3-phenyl Thiophene, 3,4-dimethylthiophene, 3,4-dibutylthiophene, 3-hydroxythiophene, 3-methoxythiophene, 3-ethoxythiophene, 3-butoxythiophene, 3-hexyloxythiophene, 3-heptyloxythiophene, 3- Octyloxythiophene, 3-decyloxythiophene, 3-dodecyloxythiophene, 3-octadecyloxythiophene, 3,4-dihydroxythiophene, 3,4-dimethoxythiophene, 3,4-diethoxythio , 3,4-dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-dihexyloxythiophene, 3,4-diheptyloxythiophene, 3,4-dioctyloxythiophene, 3,4-didecyl Oxythiophene, 3,4-didodecyloxythiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, 3,4-butenedioxythiophene, 3-methyl-4-methoxythiophene, 3- Methyl-4-ethoxythiophene, 3-carboxythiophene, 3-methyl-4-carboxythiophene, 3-methyl-4-carboxyethylthiophene, 3-methyl-4-carboxybutylthiophene, aniline, 2-methylaniline, 3- Isobutylaniline, 2-anilinesulfonic acid, 3-anili Sulfonic acid and the like.

[Polyanion]
The polyanion preferably used in the present invention is not particularly limited, but it is more preferable to have a sulfo group as the anionic group.

Specific examples of polyanions include substituted or unsubstituted polyalkylene, substituted or unsubstituted polyalkenylene, substituted or unsubstituted polyimide, substituted or unsubstituted polyamide, substituted or unsubstituted polyester, and co-polymers thereof. Preferred is a combination of a structural unit having an anionic group and a structural unit having no anionic group.

This polyanion is a solubilized polymer that solubilizes a π-conjugated conductive polymer in a solvent. The anion group of the polyanion functions as a dopant for the π-conjugated conductive polymer, and improves the conductivity and heat resistance of the π-conjugated conductive polymer.

The anion group of the polyanion may be a functional group capable of undergoing chemical oxidation doping to the π-conjugated conductive polymer. Among them, from the viewpoint of ease of production and stability, a monosubstituted sulfate group, A monosubstituted phosphate group, a phosphate group, a carboxy group, a sulfo group and the like are preferable. Furthermore, from the viewpoint of the doping effect of the functional group on the π-conjugated conductive polymer, a sulfo group, a monosubstituted sulfate group, and a carboxy group are more preferable.

Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid ethyl sulfonic acid, polyacrylic acid butyl sulfonic acid, poly-2-acrylamido-2-methylpropane sulfonic acid, polyisoprene sulfone. Acid, polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacryl carboxylic acid, polymethacryl carboxylic acid, poly-2-acrylamido-2-methylpropane carboxylic acid, polyisoprene carboxylic acid, polyacrylic acid and the like. . These homopolymers may be sufficient and 2 or more types of copolymers may be sufficient.

Also, it may be a polyanion having F in the compound. Specifically, Nafion (made by Dupont) containing a perfluorosulfonic acid group, Flemion (made by Asahi Glass Co., Ltd.) made of perfluoro vinyl ether containing a carboxylic acid group, and the like can be mentioned.

Among these, when a compound having a sulfonic acid is formed by applying and drying a conductive polymer-containing layer, when subjected to a heat treatment at a temperature of 100 ° C. or more and 200 ° C. or less for 5 minutes or more, It is more preferable because the solvent resistance of the coating film is remarkably improved.

Further, among these, polystyrene sulfonic acid, polyisoprene sulfonic acid, polyacrylic acid ethyl sulfonic acid, and polybutyl acrylate sulfonic acid are preferable. These polyanions have high compatibility with the binder resin, and can further increase the conductivity of the obtained conductive polymer.

The polymerization degree of the polyanion is preferably in the range of 10 to 100,000 monomer units, and more preferably in the range of 50 to 10,000 from the viewpoint of solvent solubility and conductivity.

As a method for producing a polyanion, for example, a method of directly introducing an anionic group into a polymer having no anionic group using an acid, a method of introducing into a polymer having no anionic group by sulfonation with a sulfonating agent, The method of manufacturing by superposition | polymerization of an anionic group containing polymeric monomer is mentioned.

Examples of the method for producing an anion group-containing polymerizable monomer by polymerization include a method for producing an anion group-containing polymerizable monomer in a solvent by oxidative polymerization or radical polymerization in the presence of an oxidizing agent and / or a polymerization catalyst. Specifically, a predetermined amount of the anionic group-containing polymerizable monomer is dissolved in a solvent, kept at a constant temperature, and a solution in which a predetermined amount of an oxidizing agent and / or a polymerization catalyst is dissolved in the solvent is added to the predetermined amount. React with time. The polymer obtained by the reaction is adjusted to a certain concentration by the solvent. In this production method, an anionic group-containing polymerizable monomer may be copolymerized with a polymerizable monomer having no anionic group.

The oxidizing agent, oxidation catalyst, and solvent used in the polymerization of the anionic group-containing polymerizable monomer are the same as those used in the polymerization of the precursor monomer that forms the π-conjugated conductive polymer.

When the obtained polymer is a polyanion salt, it is preferably transformed into a polyanionic acid. Examples of the method for converting to an anionic acid include an ion exchange method using an ion exchange resin, a dialysis method, an ultrafiltration method, and the like. Among these, the ultrafiltration method is preferable from the viewpoint of easy work.

Such a conductive polymer is preferably a commercially available material. For example, a conductive polymer (abbreviated as PEDOT-PSS) composed of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid is described in H.C. C. It is commercially available from Starck as the CLEVIOS series, from Aldrich as PEDOT / PSS 483095, 560598, and from Nagase Chemtex as the Denatron series. Polyaniline is also commercially available from Nissan Chemical as the ORMECON series. In the present invention, such an agent can also be preferably used.

A water-soluble organic compound may be contained as the second dopant. There is no restriction | limiting in particular in the water-soluble organic compound which can be used by this invention, It can select suitably from well-known things, For example, an oxygen containing compound is mentioned suitably.

The oxygen-containing compound is not particularly limited as long as it contains oxygen, and examples thereof include a hydroxy group-containing compound, a carbonyl group-containing compound, an ether group-containing compound, and a sulfoxide group-containing compound. Examples of the hydroxy group-containing compound include ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, glycerin and the like. Among these, ethylene glycol and diethylene glycol are preferable. Examples of the carbonyl group-containing compound include isophorone, propylene carbonate, cyclohexanone, γ-butyrolactone, and the like. Examples of the ether group-containing compound include diethylene glycol monoethyl ether. Examples of the sulfoxide group-containing compound include dimethyl sulfoxide. These may be used alone or in combination of two or more, but at least one selected from dimethyl sulfoxide, ethylene glycol, and diethylene glycol is preferably used.

(Formation of charge transport layer)
In the present invention, it is more preferable that the charge transport layer contains at least the polymer (A), a π-conjugated polymer, and a polyanion. For example, it can be formed by applying and drying a coating solution comprising at least a hydrophilic polymer binder component containing the polymer (A), a π-conjugated polymer component, a polyanion component, and a solvent.

The abundance ratio of the π-conjugated polymer according to the present invention is preferably such that the solid content ratio in the charge transport layer is 10% by mass or more. More preferably, it is 10% by mass to 90% by mass, and more preferably 20% by mass to 80% by mass. In the present invention, depending on the compatibility with the polymer binder containing the polymer (A) described above, even if it is 20% by mass to 50% by mass, the transmittance can be improved while maintaining conductivity, so that it is more preferable in the present invention. Is the ratio.

In the case of a conductive polymer composed of poly (3,4-ethylenedioxythiophene) which is a π-conjugated polymer and polystyrene sulfonic acid which is a polyanion, the composition ratio of the π-conjugated polymer and the polyanion is also important. In particular, when used as a charge transport layer in the photoelectric conversion element of the present invention, the composition amount of the polyanion is preferably 3 to 50 times the π-conjugated polymer. If it is 3 times or more, it is preferable because hole charges can be selectively transported and electron charges can be effectively blocked. Moreover, if it is 50 times or less, the hole charge mobility is sufficiently high, which is preferable in the present invention. A more preferable composition ratio is 5 times or more and 10 times or less.

In addition, when used as a charge transport layer, the conductivity functions as a charge transport layer if it is 1 S / cm or less, more preferably 1 × 10 ⁻² S / cm or less, 1 × 10 ⁻⁶ S / cm. More preferably, it is 1 × 10 ⁻³ S / cm or less, and 1 × 10 ⁻⁵ S / cm or more. The conductivity in this range is the same reason as described above, but has a sufficient ability to block electronic charges, and is a preferred embodiment in the photoelectric conversion element of the present invention.

As the solvent, an aqueous solvent can be preferably used. Here, the aqueous solvent represents a solvent in which 50% by mass or more is water. Of course, pure water containing no other solvent may be used. The component other than water in the aqueous solvent is not particularly limited as long as it is a solvent compatible with water, but an alcoholic solvent can be preferably used, and isopropyl alcohol having a boiling point relatively close to water can be used. This is advantageous for the smoothness of the film to be formed.

As coating methods, roll coating method, bar coating method, dip coating method, spin coating method, casting method, die coating method, blade coating method, bar coating method, gravure coating method, curtain coating method, spray coating method, doctor coating method A letterpress (letter) printing method, a stencil (screen) printing method, a lithographic (offset) printing method, an intaglio (gravure) printing method, a spray printing method, an ink jet printing method, and the like can be used.

The dry film thickness of the charge transport layer is preferably 30 to 2000 nm. The charge transport layer according to the present invention preferably has a thickness of 100 nm or more from the viewpoint of suppressing damage during electrode formation, and more preferably has a thickness of 200 nm or more from the viewpoint of further improving the leak prevention effect. Moreover, it is more preferable that it is a film thickness of 1000 nm or less from a viewpoint of maintaining the high transmittance | permeability and the resistance reduction as a film | membrane.

After coating, a drying process is appropriately performed to volatilize the solvent. Although there is no restriction | limiting in particular as conditions of a drying process, It is preferable to dry-process at the temperature of the range which does not damage a board | substrate and a conductive polymer content layer. For example, a drying treatment can be performed at 80 to 150 ° C. for 10 seconds to 10 minutes.

In the charge transport layer of the present invention, the solid content ratio of the polymer (A) contained in the dry film is more preferably 10% by mass to 90% by mass. If it is 15 mass% or more, the transmittance of the film can be improved depending on the amount added, and if it is 70 mass% or less, the film resistance can be kept low, which is preferable in the present invention.

[Formation of cross-linked structure]
In the charge transport layer of the present invention, when the polymer having a sulfo group as the polyanion and the polymer (A) are included, it is found that the film strength is significantly increased by the crosslinking reaction after the film formation by the dehydration reaction of the hydroxyl group. Thus, the effect of reducing damage to the organic layer during electrode formation can be expected, and this is a more preferable configuration.

In the present invention, for the purpose of accelerating the crosslinking reaction, it is preferable to have a crosslinking reaction step in which an additional heat treatment is performed after the film formation is dried. There is no restriction on the conditions of the heat treatment, but it is preferable to perform the treatment at a temperature within a range where the substrate and other layers are not damaged. For example, the drying treatment can be performed at 80 to 150 ° C. for 2 minutes to 120 minutes. Further, a long-time treatment of about 10 to 200 hours may be performed at a relatively low temperature of about 40 ° C. to 100 ° C. Furthermore, as a heat treatment method, in addition to heating with a general hot air dryer, a crosslinking reaction can be caused in a shorter time by using an IR heater, IH heater, microwave heating, or a combination thereof. However, since it involves a dehydration reaction, it is preferable to use at least heating with hot air.

[Nanoindentation elastic modulus]
The improvement of the film strength by the crosslinking reaction of the present invention can be evaluated by the elastic modulus using the nanoindentation method. The nanoindentation elastic modulus in the present invention is a method of calculating the elastic modulus from the degree of depression of the cantilever by pressing a special SPM cantilever against the target film with a constant load.

In order to reduce damage to the charge transport layer of the present invention, the elastic modulus is preferably 4 GPa or more and 10 GPa. If the elastic modulus is 4 GPa or more, damage during electrode formation can be suppressed, and if it is 10 GPa or less, deformation and cracks can be suppressed by appropriate flexibility, which is preferable. The more preferable elastic modulus is most preferably 5 GPa or more and 8 GPa or less from the above viewpoint.

Hereinafter, preferred embodiments of the present invention will be described in detail.

<Charge transport layer: hole transport layer, electron transport layer>
The original function of the charge transport layer is to serve as a blocking layer that transports only holes or electrons generated in the power generation layer to the electrode and prevents transport of the opposite carrier. In this case, the hole transport layer can be referred to as an electron blocking layer, and the electron transport layer as a hole blocking layer.

The hole blocking layer has a function of an electron transport layer in a broad sense. More specifically, the hole blocking layer is made of a hole blocking material having a function of transporting electrons and having a remarkably small ability to transport holes, and transports electrons. While blocking holes, the recombination probability of electrons and holes on the electrode can be improved. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed. The hole blocking layer is preferably provided adjacent to the power generation layer.

On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense. More specifically, the electron blocking layer is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports holes. However, the probability of recombination of electrons and holes can be improved by blocking electrons. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed.

As described above, the dry film thickness of the charge transport layer of the present invention is preferably 30 to 2000 nm. In particular, the charge transport layer (for example, 104 in FIG. 1) on the electrode forming side later preferably has a thickness of 100 nm or more from the viewpoint of suppressing damage during electrode formation, and 200 nm or more from the viewpoint of further improving the leakage prevention effect. More preferably, the film thickness is Moreover, it is more preferable that it is a film thickness of 1000 nm or less from a viewpoint of maintaining the high transmittance | permeability and the resistance reduction as a film | membrane.

On the other hand, the charge transport layer on the substrate side (for example, 102 in FIG. 1) is preferably 5 to 500 nm, more preferably 7 to 200 nm, and most preferably 10 to 100 nm from the viewpoint of film resistance and transmittance. .

<Hole transport layer>
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

The hole transport material has either hole injection or transport or electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, the π-conjugated polymers, conductive polymer oligomers, particularly thiophene oligomers.

The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.

Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si, p-type-SiC, nickel oxide, and molybdenum oxide can also be used as the hole injection material and the hole transport material.

Also, JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used.

It is also possible to use a hole transport layer having a high p property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

As the material, any one of conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodisides. Examples include methane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) Aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metals of these metal complexes are In, Mg Metal complexes replaced with Cu, Ca, Sn, Ga, or Pb can also be used as electron transport materials. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. Similar to the hole injection layer and the hole transport layer, inorganic semiconductors such as n-type-Si and n-type-SiC can also be used as the electron transport material.

It is also possible to use an electron transport layer having a high n property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

Also, n-type conductive inorganic oxides (titanium oxide, zinc oxide, etc.) can be used.

Specific examples include N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine (TPD) and 4,4'-bis [N- (naphthyl)- Aromatic diamine compounds such as N-phenyl-amino] biphenyl (α-NPD) and derivatives thereof, oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, polyarylalkane, butadiene, 4 , 4 ', 4 "-tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, titanium phthalocyanine oxide, etc. , Triazole derivatives, oki Use of dizazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealed amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, etc. In the polymer material, polymers such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene, and derivatives thereof can be preferably used.

Further, for example, nitrogen-containing compounds described in JP-T-2010-525613 can be preferably used in the present invention. The compound is R ₁ N (R ₂ R ₃ ), and each of R ₁ , R ₂ , and R ₃ is independently H, C1-C20 alkyl, C1-C20 alkoxy, aryl, heteroaryl, C3- C20 cycloalkyl, or C3-C20 heterocycloalkyl, or R ₁ and R ₂ , R ₂ and R ₃ , or R ₁ and R ₃ together with their attached nitrogen atoms are heteroaryl or C3-C20 Wherein R ₁ is C1-C20 alkyl substituted with Si (OR) ₃ or NH (R), or aryl substituted with COOH or SH, and each R is independently C1 It is preferably a C20 alkyl. Specific examples of nitrogen-containing compounds that can be preferably used in the present invention include 3- (2-aminoethyl) aminopropyltrimethoxysilane, (3-trimethoxysilylpropyl) diethylenetriamine, and 3-aminopropyltrimethoxysilane. 3- (N, N-dimethylamino) propyltrimethoxysilane, 4-dimethylaminobenzoic acid, 4-aminobenzoic acid or 4-aminothiophenol is preferred. More preferred is polyamine, polyethyleneimine or a derivative thereof.

In the present invention, it is more preferable that at least some of the molecules of the polymer are crosslinked by a crosslinking agent. Although the crosslinking agent is not particularly limited, it preferably contains an epoxy-containing compound, and glycerol propoxylate triglycidyl ether or glycerol diglycidyl ether can be preferably used as a specific example of the crosslinking agent.

<P-type semiconductor material>
Examples of the p-type semiconductor material used for the power generation 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 low-molecular compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, circumanthracene, bisanthene, zeslen, Compounds such as heptazeslen, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF ) -Perchloric acid complexes, and derivatives and precursors thereof.

Examples of the derivative having the above condensed polycycle include WO 03/16599 pamphlet, WO 03/28125 pamphlet, US Pat. No. 6,690,029, JP 2004-107216 A. A pentacene derivative having a substituent described in JP-A No. 2003-136964, a pentacene precursor described in US Patent Application Publication No. 2003/136964, and the like; Amer. Chem. Soc. , Vol127. No. 14.4986, J. MoI. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, acene-based compounds substituted with a trialkylsilylethynyl group described in 2706 and the like.

Examples of the conjugated polymer include a polythiophene such as poly (3-hexylthiophene) (P3HT) and oligomers thereof, or a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Such polythiophene, Nature Material, (2006) vol. 5, p328, a polythiophene-thienothiophene copolymer described in WO2008 / 000664, a polythiophene-diketopyrrolopyrrole copolymer described in WO2008 / 000664, an Adv Mater, a polythiophene-thiazolothiazole copolymer described in 2007p4160, Nature Mat. vol. 6 (2007), p497 described in PCPDTBT, etc., 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.

In addition, oligomeric materials, not polymer materials, include thiophene hexamer α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3 Oligomers such as -butoxypropyl) -α-sexithiophene can be preferably used.

Among these compounds, compounds that are highly soluble in an organic solvent to the extent that a solution process can be performed, can form a crystalline thin film after drying, and can achieve high mobility are preferable.

Further, when the electron transport layer is formed on the power generation layer by coating, there is a problem that the electron transport layer solution dissolves the power generation layer. Therefore, a material that can be insolubilized after coating by a solution process may be used. .

Examples of such materials include materials that can be insolubilized by polymerizing the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Alternatively, the soluble substituent reacts to become insoluble (pigmented) by applying energy such as heat, as described in US Patent Application Publication No. 2003/136964, and Japanese Patent Application Laid-Open No. 2008-16834. Materials etc. can be mentioned.

<N-type semiconductor material>
The n-type semiconductor material used for the bulk heterojunction layer of the present invention is not particularly limited. For example, fullerene, octaazaporphyrin and the like, p-type semiconductor perfluoro products (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalenetetra Examples thereof include aromatic carboxylic acid anhydrides such as carboxylic acid anhydrides, naphthalene tetracarboxylic acid diimides, perylene tetracarboxylic acid anhydrides, and perylene tetracarboxylic acid diimides, and polymer compounds containing the imidized product thereof as a skeleton.

However, for example, when a thiophene-based conjugated polymer is used as a p-type semiconductor material, a fullerene derivative capable of efficient charge separation is 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), and the like. 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-n-butyl ester (PCBnB), [6,6] -phenyl C61-buty Rick 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, and cyclics such as US Pat. No. 7,329,709. It is preferable to use a fullerene derivative having a substituent and having improved solubility, such as fullerene having an ether group.

<Electrode>
The organic photoelectric conversion element according to the present invention has at least a transparent electrode and a counter electrode. In the present invention, either of them is formed by the above-described forming method. Further, when a tandem configuration is adopted, the tandem configuration can be achieved by using an intermediate electrode. The structure of a preferable transparent electrode and a counter electrode is described below.

The transparent electrode and the counter electrode are the names of the electrodes expressed from the function of whether or not there is translucency. However, in the present invention, the electrodes through which holes mainly flow are used when the electrodes are classified according to the type of carrier flow. The electrode through which electrons mainly flow is called the anode, and it is called the cathode.

In the case where the first electrode is a positive electrode, since the holes are mainly extracted from the carriers composed of holes and electrons, as described above, between the first electrode and the photoelectric conversion layer (power generation layer). It is preferable to have a hole transport layer. Similarly, in the case where the second electrode is a cathode, it is preferable to have an electron transport layer between the second electrode and the photoelectric conversion layer (power generation layer) because the structure mainly extracts electrons.

<Transparent electrode>
As the transparent electrode in the organic photoelectric conversion element, a material using an electrode substance of a metal, an alloy, an electrically conductive compound and a mixture thereof is preferably used. The material composition of the optimal work function can be selected according to the junction configuration with the charge transport layer. Compositions with shallow work function 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 ) mixture , Indium, lithium / aluminum mixture, rare-earth metal, etc. In addition, as a composition having a deep work function, an ultra-thin film such as gold, silver, or platinum, or a nanoparticle / nanowire layer thereof, a conductive metal oxide material such as indium tin oxide (ITO), SnO ₂ , or ZnO, And conductive polymers. Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous light-transmitting conductive film may be used.

Furthermore, it is also a preferable aspect of the present invention to use such a metal thin film, nanoparticle / nanowire, and metal oxide material in combination as a transparent electrode having both high transmittance and high conductivity.

The sheet resistance of the transparent electrode is preferably several hundred Ω / □ or less, more preferably 50Ω / □, and further preferably 15Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected from the viewpoint of transmittance / resistance in the range of 10 to 1000 nm, preferably 100 to 200 nm.

In the case of a configuration in which electrons are extracted from the transparent electrode side, it is more preferable to perform a process of changing the work function on the above-described transparent conductive oxide film. For example, as described in the pamphlet of WO2008 / 134492, a method of forming a composition having nitrogen, phosphorus, sulfur or the like in the molecule on an oxide film, APPLIED PHYSICS LETTERS 92, 173303 (2008), or Adv. Mater. By preferably using the method of forming carbonate, cesium fluoride, Cs (acac), etc. described in 2008, 20, 415-419 on the oxide film, electrons generated in the power generation layer can be efficiently extracted. More preferred.

<Counter electrode>
On the other hand, as the counter electrode, a metal, an alloy, an electrically conductive compound and a mixture thereof are preferably used. However, metals and the like do not need to be thin films, and there are no particular limitations on the film thickness and composition as long as desired electrical conductivity can be obtained. Further, it is preferable to select a material having an optimum work function according to the charge transport layer in contact therewith. As a specific material, the same material as the example mentioned in the above-mentioned transparent electrode can be used.

In the case of a configuration in which electrons are extracted from the counter electrode side, it is more preferable that a material having a shallower work function is selected from the above-described materials so that electrons can be efficiently extracted.

(Other functional layers)
For the purpose of improving the sunlight utilization rate (photoelectric conversion efficiency), an element is formed on a pair of comb-shaped electrodes instead of the sandwiched structure between the first electrode and the second electrode as shown in FIG. The back contact type organic photoelectric conversion element can also be configured.

Further, although not shown in FIG. 1, for the purpose of improving the energy conversion efficiency and improving the lifetime of the device, various intermediate layers may be included in the device. Examples of the intermediate layer include a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, a wavelength conversion layer, a smoothing layer, and the like.

If a metal material is used as the conductive material of the counter electrode, the light coming to the counter electrode side is reflected and reflected to the first electrode side, and this light can be reused and is absorbed again by the photoelectric conversion layer, and more photoelectric conversion is performed. Efficiency is improved and preferable.

(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 in ~ 800 nm), 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 adhesion 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, or a light diffusion layer that can scatter light reflected by the cathode and enter the power generation layer again may be provided. .

As the antireflection layer, various known antireflection layers can be provided. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, an easy adhesion layer is provided adjacent to the film, and the refractive index thereof. Is preferably 1.57 to 1.63, since 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 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 a microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

Also, 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.

(Film forming method / Surface treatment method)
Examples of the method for forming a photoelectric conversion layer in which an electron acceptor and an electron donor are mixed, and a transport layer / electrode include a vapor deposition method, a coating method (including a casting method and a spin coating method), and the like. Among these, as a formation method of a photoelectric converting layer, a vapor deposition method, the apply | coating method (a casting method, a spin coat method is included), etc. can be illustrated. Among these, the coating method is preferable in order to increase the area of the interface where charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. The coating method is also excellent in production speed.

The coating method used at this time is not limited, and examples thereof include spin coating, casting from a solution, dip coating, blade coating, wire bar coating, gravure coating, and spray coating. Furthermore, patterning can also be performed by a printing method such as an ink jet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, or a flexographic printing method.

After application, it is preferable to perform heating in order to cause removal of residual solvent, moisture, and gas, and improvement of mobility and absorption of long wave by crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the particles is microscopically aggregated or crystallized and the photoelectric conversion layer can have an appropriate phase separation structure. As a result, the carrier mobility of the photoelectric conversion layer is improved and high efficiency can be obtained.

The power generation layer (bulk heterojunction layer) may be composed of a layer in which a p-type semiconductor and an n-type semiconductor are mixed, or may have a plurality of layers having different mixing ratios in the film thickness direction or a gradation structure with a mixing ratio.

(Patterning)
There is no particular limitation on the method and process for patterning the electrode, power generation layer, hole transport layer, electron transport layer, block layer and the like according to the present invention, and known methods can be applied as appropriate.

If it is a soluble material such as a photoelectric conversion layer and a transport layer, only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc., or ablation using a carbonic acid laser after film formation, or scraping directly with a scriber Patterning may be performed by a method or the like, or direct patterning may be performed using various printing methods such as an inkjet method, screen printing, and gravure printing.

In the case of insoluble materials such as electrode materials, various printing methods such as vacuum deposition, vacuum sputtering, plasma CVD, screen printing using ink in which fine particles of electrode material are dispersed, gravure printing, and ink jet The pattern may be formed by a known method such as etching or lift-off of the deposited film, or by transferring a pattern formed on another substrate.

(Sealing)
In order to prevent the produced organic photoelectric conversion element from being deteriorated by oxygen, moisture, etc. in the atmosphere, it is preferable to seal 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 of coating, method of coating organic polymer material (polyvinyl alcohol etc.) with high gas barrier property, method of depositing inorganic thin film (silicon oxide, aluminum oxide etc.) or organic film (parylene etc.) with high gas barrier property under vacuum And a method of laminating these in a composite manner.

Further, in the present invention, from the viewpoint of improving energy conversion efficiency and device life, the entire device may be sealed with two substrates with a barrier, and preferably a moisture getter, oxygen getter, etc. are enclosed. Is more preferred in the present invention.

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

[Preparation of polymer (A)]
As polymer (A), poly (2-hydroxyethyl acrylate) was synthesized.

First, in order to synthesize an initiator, 2-bromoisobutyryl bromide (7.3 g, 35 mmol), triethylamine (2.48 g, 35 mmol) and THF (20 ml) were added to a 50 ml three-necked flask, and the internal temperature was reduced to 0 with an ice bath. Held at 0C. In this solution, 30 ml of a 33% THF solution of oligoethylene glycol (10 g, 23 mmol, ethylene glycol units 7-8, manufactured by Laporte Specialties) was added dropwise. After stirring for 30 minutes, the solution was brought to room temperature and further stirred for 4 hours. After THF was removed under reduced pressure by a rotary evaporator, the residue was dissolved in diethyl ether and transferred to a separatory funnel. Water was added and the ether layer was washed three times, and then the ether layer was dried with MgSO ₄ . Ether was distilled off under reduced pressure using a rotary evaporator to obtain 8.2 g of initiator (yield 73%).

Subsequently, 5 ml of the synthesized initiator (500 mg, 1.02 mmol), 2-hydroxyethyl acrylate (4.64 g, 40 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), 50:50 v / v% methanol / water mixed solvent was added to the Schlenk tube. The Schlenk tube was immersed in liquid nitrogen for 10 minutes under reduced pressure. The Schlenk tube was taken out of liquid nitrogen and replaced with nitrogen after 5 minutes. After performing this operation three times, bipyridine (400 mg, 2.56 mmol) and CuBr (147 mg, 1.02 mmol) were added under nitrogen, and the mixture was stirred at 20 ° C. After 30 minutes, the reaction solution was dropped onto a 4 cm Kiriyama funnel with filter paper and silica, and the reaction solution was recovered under reduced pressure. The solvent was distilled off under reduced pressure using a rotary evaporator and then dried under reduced pressure at 50 ° C. for 3 hours. As a result, 2.60 g (yield 84%) of poly (2-hydroxyethyl acrylate) having a number average molecular weight of 13100, a molecular weight distribution of 1.17, and a content of number average molecular weight <1000 and a content of 0% were obtained.

The structure and molecular weight were measured by ¹ H-NMR (400 MHz, manufactured by JEOL Ltd.) and GPC (Waters 2695, manufactured by Waters), respectively.

<GPC measurement conditions>
Apparatus: Wagers 2695 (Separations Module)
Detector: Waters 2414 (Refractive Index Detector)
Column: Shodex Asahipak GF-7M HQ
Eluent: Dimethylformamide (20 mM LiBr)
Flow rate: 1.0 ml / min
Temperature: 40 ° C
Similarly to the above synthesis method, poly (2-hydroxybutyl acrylate) (number average molecular weight of about 15000) was synthesized from 2-hydroxybutyl acrylate as a raw material, and purified in the same manner as in the above method.

For poly (2-hydroxyethyl vinyl ether) (number average molecular weight about 20000, solid content 20% aqueous solution) and poly (2-hydroxyethyl acrylamide) (number average molecular weight about 20000, solid content 20% aqueous solution), A commercial product having the number average molecular weight was obtained and purified in the same manner as described above so that the content of the number average molecular weight <1000 was 0%.

[Measurement of elastic modulus by nanoindentation method]
The elastic modulus was measured by the nanoindentation method according to the following.

Using a Triscope made by Hystron, it was mounted on SPI3800N made by SII Nano Technology and measured. For the measurement, a triangular pyramid diamond indenter called a Belkovic indenter (tip ridge angle 142.3 °) having a tip curvature radius of 75 to 100 nm was used. Applying pressure at right angles to the surface, gradually applying pressure, and gradually returning the load to 0 after reaching the maximum load. A value P / A obtained by dividing the maximum load P at this time by the projected area A of the indenter contact portion is calculated as hardness, and this value (hardness = P / A (GPa)) is used as an index representing the nanoindentation elastic modulus. Show.

[Production of Organic Photoelectric Conversion Device SC-101]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 150 nm (sheet resistance: 8 Ω / □) is patterned to a width of 10 mm using a normal photolithography technique and wet etching to form a first 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 with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

On this transparent substrate, a mixed solution of polyethyleneimine dissolved in isopropanol and glycerol propoxylate triglycidyl ether was applied and dried on a hot plate at 120 ° C. for 10 minutes to form a hole blocking layer.

Subsequently, P3HT (manufactured by Prectronics: regioregular poly-3-hexylthiophene, HOMO: -5.5 eV, LUMO: -3.4 eV) and PCBM (manufactured by Frontier Carbon: 6,6-phenyl-C) were added to chlorobenzene. _61- butyric acid methyl ester, HOMO: -6.1 eV, LUMO: -4.3 eV) prepared at a ratio of 1: 0.8 so as to be 3.0% by mass, filtered through a filter and dried. A power generation layer was formed on the substrate so that the film thickness was about 200 nm. Subsequently, a liquid containing PEDOT-PSS (Baytron P4083, manufactured by Starkvitech, IP (HOMO): -5.0 eV) composed of a conductive polymer and a polyanion, Emulgen manufactured by Kao Chemical Co., Ltd., and isopropanol was prepared. The coating film was dried 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 Ag metal is deposited at a deposition rate of 5.0 nm / second. The second electrode was formed by laminating 200 nm. The obtained organic photoelectric conversion element SC-101 was moved to a nitrogen chamber and sealed with a sealing cap and a UV curable resin, and the organic photoelectric conversion element SC-101 having a light receiving portion of 10 × 10 mm size was obtained. Produced.

Separately, a substrate on which only the hole transport layer was formed was prepared, and after heat treatment at 150 ° C. for 10 minutes, the elastic modulus was measured using the nanoindentation method described above, and it was 1.9 GPa.

In addition, the elastic modulus of each organic photoelectric conversion element described below is also formed in a film thickness of 300 nm only for the charge transport layer that mainly transports either holes or electrons of each element as in the organic photoelectric conversion element SC-101. The prepared substrate was manufactured, heat-treated at 150 ° C. for 10 minutes, and then the elastic modulus was measured using a nanoindentation method.

[Production of Organic Photoelectric Conversion Device SC-102]
In the production of the organic photoelectric conversion element SC-101, functional layers were similarly formed up to the power generation layer. Subsequently, PEDOT-PSS (Baytron P4083, Starckvitech, IP (HOMO): -5.0 eV) composed of a conductive polymer and a polyanion, Emulgen, Kao Chemical Co., Ltd., and the above synthesized poly (2-Hydroxyethyl acrylate) was prepared so as to contain 5% by mass of the solid content of the dry film, and applied and dried so that the dry film thickness was about 100 nm. Thereafter, the hole transport layer was formed by promoting the crosslinking reaction by heat treatment at 150 ° C. for 10 minutes.

A photoelectric conversion element SC-102 was produced in the same manner as SC-101 except that the hole transport layer was formed as described above.

The elastic modulus of the SC-102 hole transport layer was measured to be 3.6 GPa.

[Production of Organic Photoelectric Conversion Device SC-103]
In the production of the organic photoelectric conversion element SC-102, except that poly (2-hydroxyethyl acrylate) is contained in the hole transport layer in a solid content of 15% by mass, the organic photoelectric conversion element SC-102 Similarly, SC-103 was produced.

The elastic modulus of the SC-103 hole transport layer was measured to be 4.9 GPa.

[Production of Organic Photoelectric Conversion Device SC-104]
In the production of the organic photoelectric conversion element SC-102, except that poly (2-hydroxyethyl acrylate) is included in the hole transport layer in a solid content of 30% by mass in the dry film, Similarly, SC-104 was produced.

The elastic modulus of the hole transport layer of SC-104 was measured and found to be 5.4 GPa.

[Production of Organic Photoelectric Conversion Device SC-105]
In the production of the organic photoelectric conversion element SC-102, except that poly (2-hydroxyethyl acrylate) is included in the hole transport layer in a solid content of 50% by mass in the dry film, Similarly, SC-105 was produced.

The elastic modulus of the hole transport layer of SC-105 was measured to be 6.3 GPa.

[Production of Organic Photoelectric Conversion Device SC-106]
In the production of the organic photoelectric conversion element SC-102, except that poly (2-hydroxyethyl acrylate) is included in the hole transport layer in a solid content of 70% by mass in the dry film, Similarly, SC-106 was produced.

The elastic modulus of the hole transport layer of SC-106 was measured to be 5.5 GPa.

[Production of Organic Photoelectric Conversion Device SC-107]
In the production of the organic photoelectric conversion device SC-102, except that poly (2-hydroxyethyl acrylate) was included in the hole transport layer in a solid content of 90% by mass in the dry film, Similarly, SC-107 was produced.

The elastic modulus of the hole transport layer of SC-107 was measured to be 4.7 GPa.

[Production of Organic Photoelectric Conversion Device SC-108]
In the production of the organic photoelectric conversion element SC-106, SC was made in the same manner as the organic photoelectric conversion element SC-106 except that poly (2-hydroxybutyl acrylate) was used instead of poly (2-hydroxyethyl acrylate). -108 was produced.

The elastic modulus of the hole transport layer of SC-108 was measured to be 5.2 GPa.

[Production of Organic Photoelectric Conversion Device SC-109]
In the production of the organic photoelectric conversion element SC-106, SC was made in the same manner as the organic photoelectric conversion element SC-106 except that poly (2-hydroxyethyl vinyl ether) was used instead of poly (2-hydroxyethyl acrylate). -109 was produced.

The elastic modulus of the hole transport layer of SC-109 was measured to be 4.5 GPa.

[Production of Organic Photoelectric Conversion Device SC-110]
In the production of the organic photoelectric conversion element SC-106, SC was made in the same manner as the organic photoelectric conversion element SC-106 except that poly (2-hydroxyethyl acrylamide) was used instead of poly (2-hydroxyethyl acrylate). -110 was produced.

Note that when the elastic modulus of the hole transport layer of SC-110 was measured, it was 5.9 GPa.

[Production of Organic Photoelectric Conversion Device SC-111]
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 150 nm (sheet resistance: 8 Ω / □) is patterned to a width of 10 mm using a normal photolithography technique and wet etching to form a first 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 with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

A liquid containing PEDOT-PSS (Baytron P4083, Starck Vitec, IP (HOMO): -5.0 eV) and isopropanol composed of a conductive polymer and polyanion is prepared so that the dry film thickness is about 50 nm. And dried. Thereafter, heat treatment was performed at 150 ° C. for 10 minutes to form a hole transport layer.

Subsequently, P3HT (manufactured by Prectronics: regioregular poly-3-hexylthiophene, HOMO: -5.5 eV, LUMO: -3.4 eV) and PCBM (manufactured by Frontier Carbon: 6,6-phenyl-C) were added to chlorobenzene. _61- butyric acid methyl ester, HOMO: -6.1 eV, LUMO: -4.3 eV) prepared at a ratio of 1: 0.8 so as to be 3.0% by mass, filtered through a filter and dried. A power generation layer was formed on the hole transport layer so that the film thickness was about 200 nm.

Subsequently, in addition to polyethyleneimine (PEI) dissolved in isopropanol, glycerol propoxylate triglycidyl ether (GPTGE), and polyanion as Nafion (Nafion: polyfluorinated sulfone, manufactured by DuPont Chemical Co., Ltd.), the solid content concentration of the dry membrane is 50 Poly (2-hydroxyethyl acrylate) was dissolved so as to have a mass%, and was applied and dried so that the dry film thickness was 20 nm. Thereafter, heat treatment was performed at 120 ° C. for 30 minutes to form a hole blocking layer.

Next, the substrate on which the series of functional layers is formed is moved into a vacuum deposition apparatus chamber, the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻⁴ Pa or less, and then Al metal is deposited at a deposition rate of 5.0 nm / second. The second electrode was formed by laminating 200 nm. The obtained organic photoelectric conversion element SC-111 was moved to a nitrogen chamber and sealed using a sealing cap and a UV curable resin, so that the organic photoelectric conversion element SC-111 having a light receiving portion of 10 × 10 mm size was obtained. Produced.

Separately, a substrate on which a functional layer before Ag deposition was formed was prepared, and the elastic modulus was measured using the nanoindentation method described above, and it was 3.2 GPa.

<Evaluation of device performance>
About the photoelectric conversion element produced above, by irradiating the solar simulator (AM1.5G filter) with light of 100 mW / cm ² intensity and overlaying a mask with an effective area of 1 cm ² on the light receiving part, the IV characteristics are evaluated. The short-circuit current density Jsc (mA / cm ² ), the open circuit voltage Voc (V), and the fill factor FF were measured at four light receiving portions formed on the same element. Here, relative values were estimated when SC-101 Jsc and FF were set to 100, and the results are shown in Table 1.

Further, the electric conductivity of the hole transport layer formed by SC-102 was measured by a four-terminal four-probe method and found to be 2 × 10 ⁻⁴ S / cm. The conductivity was in the range of 10 ⁻⁵ S / cm to 1 × 10 ⁻³ S / cm, though there was a difference between SC-103 to SC-106 and SC-108 to SC-110.

As is clear from Table 1, the SC-102 to SC-111 of the present application show superior results of Jsc and FF with high transmittance and elastic modulus, compared with the conventional structure SC-101. The effect of the invention became clear.

DESCRIPTION OF SYMBOLS 10 Photoelectric conversion element 101 1st electrode 102 Hole blocking layer (or electron transport layer)
103 power generation layer 103a p-type semiconductor material 103b n-type semiconductor material 104 electron blocking layer (hole transport layer)
105 second electrode

Claims

Organic having at least a power generation layer including a p-type semiconductor material and an n-type semiconductor material and a charge transport layer mainly transporting either holes or electrons between the first electrode and the second electrode In the photoelectric conversion element, the charge transport layer contains a polymer (A) having at least one selected from the following three unit structures.

(In the formula, X represents a hydrogen atom or a methyl group, R 1 to R 3 each independently represents a linear or branched alkylene group having 1 to 5 carbon atoms. L, m, and n represent the polymer (A ) Represents the respective composition ratio (mol%) when the total number of moles of all monomers constituting 100 is 100, and 50 ≦ l + m + n ≦ 100.)
The organic photoelectric conversion device according to claim 1, wherein the charge transport layer contains at least the polymer (A), a π-conjugated polymer, and a polyanion.
3. The organic photoelectric conversion element according to claim 1, wherein the solid content ratio of the polymer (A) in the charge transport layer is 10% by mass to 90% by mass.
The elastic modulus of the charge transport layer measured by a nanoindentation method after the heat treatment step of the polymer (A) and the polyanion is 4 GPa or more and 10 GPa or less. The organic photoelectric conversion element of Claim 1.
The organic photoelectric conversion device according to any one of claims 1 to 4, wherein the organic photoelectric conversion device is produced by a heat treatment step of the polymer (A) and the polyanion after the formation of the charge transport layer. A method for producing a photoelectric conversion element.