JP2011009622A - Method of forming thin film for organic thin film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thin film for organic thin film solar cell which provides an organic thin film solar cell superior in efficiency by an applying method capable of obtaining a large area easily and at low cost by using an acene-group compound.SOLUTION: The thin film for the organic thin film solar cell includes a substrate on which an electrode is formed, a p-type organic semiconductor and an n-type organic semiconductor. The method for forming the thin film includes: (1) a p-type layer formation process where a p-type organic semiconductor coating liquid containing one or more kinds of acene-group compounds is applied to the electrode of the substrate on which the electrode is formed directly or via the organic layer, and a p-type organic semiconductor layer is formed by setting a substrate temperature during application and/or after application at 40°C or higher; and (2) a thin film formation process where an n-type organic semiconductor coating liquid containing one or more kinds of n-type organic semiconductors is applied on the p-type organic semiconductor layer to form the thin film.

Description

  The present invention relates to a method for producing a thin film for an organic thin film solar cell using an acene compound.

  The organic thin film solar cell has been actively researched and developed since it was reported by Tang (Non-Patent Document 1). Generally, an organic semiconductor thin film used for an organic thin film solar cell is divided into two types: a thin film using a low molecular weight organic material and a thin film using a high molecular weight organic material. As a method for producing a thin film using a low molecular weight organic material, vacuum deposition is generally used. However, in the vapor deposition method, since the film is formed in a vacuum, it is difficult to increase the area, and the material utilization efficiency is not sufficient.

  On the other hand, various printing methods can be used as a method for producing a thin film using a polymer organic material. Examples of various printing methods include letterpress printing, gravure printing, screen printing, offset printing, ink jet, and spray. According to these, it is possible to form a film at atmospheric pressure, and it is easy to increase the area as compared with the vapor deposition method. Moreover, since the utilization efficiency of material is also high, it is advantageous in terms of cost.

  In recent years, a bulk heterostructure in which a p-type organic semiconductor and an n-type organic semiconductor are mixed has been actively studied. In the case of using a low molecular organic material, a bulk heterostructure can be produced mainly by co-evaporation. For example, as described in Non-Patent Document 2, conversion efficiency of 3.6% is achieved with zinc phthalocyanine and C60 fullerene.

  Research on solar cells using acene-based compounds has also been conducted. For example, Patent Documents 1 and 2 describe solar cells using acene-based compounds, but describe specific conditions for forming a p-type semiconductor film and an n-type semiconductor film by a coating method. Absent.

International Publication No. WO2005 / 119794 Pamphlet JP 2007-335760 A

C. W. Tang, Appl. Phys. Lett. , 48, p. 183 (1986) T. T. et al. Tajima, S .; Toyoshima, K .; Hara, K .; Saito, and K.K. Yase, Jpn. J. et al. Appl. Phys. , 45, L217 (2006)

  The present invention relates to a method for producing a thin film for an organic thin film solar cell that provides an efficient organic thin film solar cell by a coating method using an acene-based compound, which is easy to increase the area and enables cost reduction. The issue is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is as follows.

[1] A method for producing a thin film for an organic thin film solar cell comprising a substrate on which an electrode is formed, a p-type organic semiconductor, and an n-type organic semiconductor,
1) A p-type organic semiconductor coating solution containing one or more acene-based compounds is applied directly or via an organic layer on the electrode on which the electrode is formed, and the substrate is coated and / or after coating. A p-type layer forming step of forming a p-type organic semiconductor layer by setting the temperature to 40 ° C. or higher, and 2) an n-type containing at least one n-type organic semiconductor on the p-type organic semiconductor layer The manufacturing method of the thin film for organic thin film solar cells including the thin film formation process which apply | coats an organic-semiconductor coating liquid and produces a thin film.

｛式中、Ｒ₁〜Ｒ₁₀は、各々独立して、水素原子を表すか、又は、脂肪族炭化水素基、芳香族炭化水素基、アルコキシ基、ハロゲン基、アシル基、エステル基、エーテル基、アミノ基、アミド基、シアノ基、シリル基及び光反応性基からなる群から選択される１つ以上の基を含む官能基を表し、Ｒ₁〜Ｒ₁₀のうち少なくとも１つは水素原子以外であり、そしてｎは２〜７の整数である。｝で表される１種以上の化合物である、上記［１］に記載の有機薄膜太陽電池用薄膜の製造方法。 [2] The acene compound has the following chemical formula (1):

{Wherein R _{1 to} R ₁₀ each independently represents a hydrogen atom, or an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alkoxy group, a halogen group, an acyl group, an ester group, an ether group. Represents a functional group containing one or more groups selected from the group consisting of amino groups, amide groups, cyano groups, silyl groups and photoreactive groups, and at least one of R _{1 to} R ₁₀ is other than a hydrogen atom And n is an integer from 2 to 7. } The manufacturing method of the thin film for organic thin-film solar cells as described in said [1] which is 1 or more types of compounds represented by these.

  [3] The thin film for organic thin-film solar cells according to [1] or [2], wherein the acene compound is one or more compounds selected from the group consisting of pentacene, pentacene derivatives, tetracene and tetracene derivatives. Manufacturing method.

  By producing a thin film for a solar cell using a coating solution according to the production method of the present invention, a highly efficient solar cell can be produced easily at low cost using the thin film.

It is a schematic diagram which shows an example of a structure of the organic thin film solar cell produced using the manufacturing method of this invention.

  Hereinafter, typical modes for carrying out the present invention will be described in detail. The present invention is a method for producing a thin film for an organic thin film solar cell having a substrate on which an electrode is formed, a p-type organic semiconductor, and an n-type organic semiconductor, and 1) the electrode on the substrate on which the electrode is formed. By applying a p-type organic semiconductor coating solution containing one or more acene compounds directly or through an organic layer, and setting the substrate temperature at and / or after coating to 40 ° C. or higher. A p-type layer forming step for forming a p-type organic semiconductor layer, and 2) forming a thin film by applying an n-type organic semiconductor coating solution containing one or more n-type organic semiconductors on the p-type organic semiconductor layer The manufacturing method of the thin film for organic thin film solar cells including the thin film formation process to perform is provided.

<P-type organic semiconductor and n-type organic semiconductor>
The acene-based compound contained in the p-type organic semiconductor coating solution used in the present invention is a compound having a structure formed by condensing a plurality of benzene rings. Preferred examples of the acene compound used in the present invention include the following chemical formula (1):

｛式中、Ｒ₁〜Ｒ₁₀は、各々独立して、水素原子を表すか、又は、脂肪族炭化水素基、芳香族炭化水素基、アルコキシ基、ハロゲン基、アシル基、エステル基、エーテル基、アミノ基、アミド基、シアノ基、シリル基及び光反応性基からなる群から選択される１つ以上の基を含む官能基を表し、Ｒ₁〜Ｒ₁₀のうち少なくとも１つは水素原子以外であり、そしてｎは２〜７の整数である。｝で表される１種以上の化合物が挙げられる。

{Wherein R _{1 to} R ₁₀ each independently represents a hydrogen atom, or an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alkoxy group, a halogen group, an acyl group, an ester group, an ether group. Represents a functional group containing one or more groups selected from the group consisting of amino groups, amide groups, cyano groups, silyl groups and photoreactive groups, and at least one of R _{1 to} R ₁₀ is other than a hydrogen atom And n is an integer from 2 to 7. } One or more types of compounds represented by these are mentioned.

  In the chemical formula (1), examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group. Examples of the aromatic hydrocarbon group include a phenyl group and a naphthyl group. Examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the halogen group include a fluorine group, a chlorine group, a bromine group, and an iodine group. A benzoyl group etc. are mentioned as an acyl group. Examples of the photoreactive group include acryloyloxy group, methacryloyloxy group, cinnamyl group, butadiynyl group, styryl group, isopentadienyl group, cyclopentadienyl group, and cyclohexadienyl group. The functional group may include one or more of the above-described groups, and examples of the functional group including two or more of the groups include a group including a benzyl group or a triisopropylsilylethynyl group. Can be mentioned.

  The acene-based compound is preferably at least one compound selected from the group consisting of pentacene, pentacene derivatives, tetracene and tetracene derivatives, in that a thin film for an organic thin film solar cell having high conversion efficiency can be produced. Particularly preferred acene compounds include tetracene (molecular weight 228), pentacene (molecular weight 278), 6,13-bis (triisopropylsilylethynyl) pentacene (the following chemical formula (2):

で表される構造、分子量６３９）、２−ヘキシルペンタセン（分子量３６２）、２−ヘキシルテトラセン（分子量３１２）等が挙げられる。これらは変換効率が高い有機薄膜太陽電池用薄膜を製造できる点で特に好ましい。

And a structure represented by the formula: molecular weight 639), 2-hexylpentacene (molecular weight 362), 2-hexyltetracene (molecular weight 312), and the like. These are particularly preferable in that a thin film for an organic thin film solar cell having a high conversion efficiency can be produced.

  The p-type organic semiconductor coating liquid used in the present invention may contain a p-type organic semiconductor other than the above-described acene-based compound. Examples of the p-type organic semiconductor include N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (NPD, molecular weight 588), N, N ′. -Diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (TPD, molecular weight 516), 1,3,5-tris (3-methyldiphenylamino) Examples thereof include aromatic amine-based materials such as benzene (m-MTDATA, molecular weight 788). In addition, phthalocyanine complexes such as copper phthalocyanine (CuPc, molecular weight 576), zinc phthalocyanine (ZnPc, molecular weight 578), polyphyrin compounds, perylene derivatives, imidazole derivatives, triazole derivatives, pyrazoline derivatives, oxazole derivatives, oxalate derivatives Examples include diazole derivatives, stilbene derivatives, polyarylalkane derivatives, and the like. In addition, derivatives of thiophene, derivatives of polyphenylvinylene (PPV), and the like can be given. Specific examples of thiophene derivatives include P3HT (Poly (3-hexylthiophene-2,5-diyl)), P3OT (Poly (3-octylthiophene-2,5-diyl)), P3DDT (Poly (3-dodecylthiophene- 2,5-diyl)).

  Next, the n-type organic semiconductor contained in the n-type organic semiconductor coating solution used in the present invention includes fluorinated acene compounds, fullerene compounds, naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, perylene. Examples thereof include tetracarboxylic acid diimide derivatives, oxadiazole derivatives, triazole derivatives, triazine derivatives, and quinoline derivatives. Fullerene compounds and perylenetetracarboxylic acid diimide derivatives are particularly preferred in that good efficiency can be exhibited in the solar cell. More specifically, C60 fullerene (molecular weight 721), C60 fullerene derivative, C70 fullerene (molecular weight 841), C70 fullerene derivative, perylenetetracarboxylic acid diimide derivative, and fluorinated acene-based compound have good efficiency for solar cells. It is particularly preferable in that it can be expressed.

  As the C60 fullerene derivative, the following chemical formula (3):

で表されるもの（[６，６]−ＰｈｅｎｙｌＣ₆₁ｂｕｔｙｒｉｃ ａｃｉｄ ｍｅｔｈｙｌ ｅｓｔｅｒ、分子量９１１）が好ましく、Ｃ７０フラーレン誘導体としては、下記化学式（４）：

In those represented by _{([6,6] -PhenylC 61 butyric acid} methyl ester, molecular weight 911) it is preferred, as the C70 fullerene derivative, the following chemical formula (4):

で表されるもの（[６，６]−ＰｈｅｎｙｌＣ₇₁ｂｕｔｙｒｉｃ ａｃｉｄ ｍｅｔｈｙｌ ｅｓｔｅｒ、分子量１０３１）が好ましく、ペリレンテトラカルボン酸ジイミド誘導体としては、下記化学式（５）：

([6,6] -PhenylC ₇₁ butyric acid methyl ester, molecular weight 1031) is preferable, and the perylenetetracarboxylic acid diimide derivative is represented by the following chemical formula (5):

で表されるもの（Ｎ、Ｎ‘−Ｄｉｏｃｔｙｌ−３，４，９，１０−ｐｅｒｙｌｅｎｅｄｉｃａｒｂｏｘｉｍｉｄｅ，分子量６１７）が好ましい。

(N, N′-Dioctyl-3,4,9,10-perylene carbonate, molecular weight 617) is preferable.

で表されるものが好ましい。 As the fluorinated acene compound, fluorinated pentacene (molecular weight 530) is preferable, and the following chemical formula (6):

The thing represented by these is preferable.

<P-type organic semiconductor coating solution and n-type organic semiconductor coating solution>
The p-type organic semiconductor coating solution used in the present invention is a coating solution containing one or more acene-based compounds in a state of being dissolved or dispersed or a mixture of dissolved and dispersed. More specifically, the acene compound preferably contains one or more selected from the group consisting of pentacene, a pentacene derivative, tetracene and a tetracene derivative, from the viewpoint of expressing good efficiency of the solar cell.

  The n-type organic semiconductor coating solution used in the present invention is a coating solution containing one or more n-type organic semiconductors in a dissolved or dispersed state or a mixture of dissolved and dispersed states. Specifically, although not particularly limited, examples of the n-type organic semiconductor include a fluorinated acene compound, C60 fullerene (molecular weight 721), C60 fullerene derivative, C70 fullerene (molecular weight 841), C70 fullerene derivative, perylenetetracarboxylic acid diimide. Including at least one selected from the group consisting of derivatives is preferable in terms of expressing good efficiency of the solar cell.

  The p-type organic semiconductor coating solution and the n-type organic semiconductor coating solution (hereinafter collectively referred to simply as “coating solution”) used in the present invention usually contain a solvent, and the solvent is typically an organic solvent. is there. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, butanol, hexanol, methyl cellosolve, ethyl cellosolve, glycols such as ethylene glycol and propylene glycol, ketones such as acetone and methyl ethyl ketone, ethyl acetate, butyl acetate and the like. Esters, ethers such as dioxane, tetrahydrofuran, dibutyl ether, benzene, toluene, xylene, trimethylbenzene, hexane, heptane, octane, nonane, decane, cyclohexane, decahydronaphthalene (decalin), tetralin, 1-methylnaphthalene, etc. Hydrocarbons, halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, dichlorobenzene and trichlorobenzene, and N, N-dimethylform Bromide, N, N- dimethylacetamide, dimethyl sulfoxide, polar solvents such as N- methylpyrrolidone. These organic solvents can be used alone or in admixture of two or more.

  The coating liquid used in the present invention may contain an additive for the purpose of improving dispersibility and film forming property. The additive is not particularly limited, and for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant or the like, a silicon-based additive, or the like may be used. it can. The additive is added in an amount of 0.000001% by mass to 1% with respect to 100% by mass of the p-type or n-type organic semiconductor coating solution, from the viewpoint of balance between dispersion stability and improvement in film formability and conversion efficiency. Mass% is preferred.

  Examples of the anionic surfactant include fatty acid salts such as sodium lauryl sulfate, higher alcohol sulfate esters, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether sulfates, and polyoxyethylene polycycles. Phenyl ether sulfate, polyoxynonyl phenyl ether sulfonate, polyoxyethylene-polyoxypropylene glycol ether sulfate, sulfonate group or sulfate group and polymerizable unsaturated double bond in the molecule, so-called Examples include reactive surfactants.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene nonylphenyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block copolymer, and their skeletons and polymers. Reactive nonionic surfactants having an unsaturated double bond in the molecule.

  Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts.

  Moreover, polydimethylsiloxane etc. are mentioned as a silicon-type additive.

The coating liquid used in the present invention can be prepared, for example, by any of the following methods.
1) A method of preparing a coating liquid by selecting a p-type or n-type organic semiconductor and an organic solvent suitable for the organic semiconductor, mixing and stirring the organic semiconductor and the organic solvent.
2) A method of selecting an organic semiconductor and an organic solvent suitable for the organic semiconductor, mixing the organic semiconductor and the organic solvent, and preparing a coating solution using a ball mill or a homogenizer.
3) A method of preparing a coating solution by substituting the organic solvent in the coating solution prepared by the method of 1) or 2) above with another solvent.

  In the methods 1) to 3), one type or two or more types of organic semiconductors may be used, and one type or two or more types of organic solvents may be used in combination. Moreover, the coating liquid prepared by the method of said 1) to 3) can also be mixed and used. When preparing the coating solution by the method of 1) to 3) above, the dissolution of the organic semiconductor in the solvent proceeds by setting the temperature of the organic semiconductor solution or dispersion to 40 ° C. or higher, and the coating solution for solar cells As a suitable solution. When the solution or dispersion liquid is heated, it may be during preparation of the coating liquid (for example, during stirring, during ball mill operation or during homogenizer operation) or after the completion of those operations, but it is heated from the start of preparation of the coating liquid. This is preferable because a more uniform coating solution can be prepared. The concentration of the organic semiconductor in the coating solution is preferably 0.01% by mass or more and 20% by mass or less in that a semiconductor layer having an appropriate film thickness can be produced and high efficiency of the solar cell can be obtained. The mass% is preferably 10% by mass or less.

<Configuration of organic thin film solar cell>
In FIG. 1, an example of a structure of the organic thin film solar cell produced using the manufacturing method of this invention is shown. In the organic thin film solar cell having the configuration shown in FIG. 1, an electrode 2, a p-type organic semiconductor layer 3, an n-type organic semiconductor layer 4 and an electrode 5 are formed on a substrate 1. The substrate 1 exists on the electrode 2 side in FIG. 1 (that is, the substrate 1, the electrode 2, the p-type organic semiconductor layer 3 and the n-type organic semiconductor layer 4 constitute the thin film for an organic thin film solar cell according to the present invention). The substrate may exist on both the electrode 2 side and the electrode 5 side.

  Examples of the substrate 1 include all commonly used substrates such as glass substrates, plastic substrates such as PET (polyethylene terephthalate), PC (polycarbonate), PP (polypropylene), aluminum substrates, stainless steel (SUS) substrates, and paper substrates. It is done. However, when the solar cell takes light from the substrate side, it is necessary to select a transparent substrate.

Examples of the electrode 2 include zinc oxide (also referred to as ZnO and zinc oxide), tin oxide (also referred to as SnO ₂ and tin oxide), indium oxide (also referred to as In ₂ O ₃ and indium oxide), and the like. And titanium oxide (TiO ₂ , also referred to as titanium oxide). These usually have many so-called lattice defects lacking the crystal lattice. That is, the electrode 2 is normally manufactured in an oxygen defect state, thereby generating surplus electrons and exhibiting optical semiconductivity. Therefore, when the electrode 2 is manufactured, the formation of vacancies may be actively promoted by reduction firing that suppresses the supply amount of oxygen, or addition of a certain dopant.

  As the dopant, aluminum (Al) or gallium (Ga) is used when the electrode 2 is zinc oxide. When the electrode 2 is tin oxide, antimony (Sb) (or antimony oxide) is used. Niobium (Nb) is used when the electrode 2 is titanium oxide. When the electrode 2 is indium oxide, tin (Sn) (tin oxide) is used, and indium tin oxide (also referred to as ITO or indium tin oxide) formed in this case is used as a transparent conductive material. Used. All the above-mentioned metal oxides can also be preferably used. Metals such as gold and platinum can also be used. Further, a conductive polymer such as PEDOT: PSS (poly (3,4 ethylenedioxythiophene): polystyrene sulfonic acid) can also be used. When the solar cell takes in light from the electrode 2 side, the electrode 2 is preferably transparent.

  In the present invention, for example, a glass substrate with ITO can be preferably used as the substrate 1 on which the electrode 2 is formed.

  A p-type organic semiconductor layer 3 and an n-type organic semiconductor layer 4 are formed on the electrode 2. At the interface between the p-type organic semiconductor layer 3 and the n-type organic semiconductor layer 4, the p-type organic semiconductor and the n-type organic semiconductor may be mixed by mixing. Further, the p-type organic semiconductor layer 3 and the n-type organic semiconductor layer 4 may be completely mixed, and the p-type organic semiconductor and the n-type organic semiconductor may be mixed. Further, a hole-side buffer layer may be introduced between the electrode 2 and the p-type organic semiconductor layer 3. As the hole-side buffer layer, the aforementioned PEDOT: PSS or acene compound can be used. Further, an electron-side buffer layer may be introduced between the n-type organic semiconductor layer 4 and the electrode 5. As the buffer layer on the electron side, BAlq ((p-phenylphenolate) aluminum (III)), BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, or bathocuproin), TAZ (3 -(4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole) and the like.

  As the electrode 5, lithium, lithium-indium alloy, calcium, magnesium, magnesium-silver alloy, magnesium-indium alloy, indium, ruthenium, aluminum, aluminum-lithium alloy, aluminum-calcium alloy, aluminum-magnesium alloy, ITO, IZO Etc. These electrode materials may be used alone or in combination. When the solar cell takes light from the electrode 5 side, the material of the electrode 5 is preferably transparent. Further, lithium fluoride or the like may be deposited between the n-type organic semiconductor layer 4 and the electrode 5 or between the electrode 5 and the buffer layer.

<Manufacturing process of thin film for organic thin film solar cell>
In the present invention, the p-type organic semiconductor coating liquid and the n-type organic semiconductor coating liquid as described above are used, respectively, and the p-type organic semiconductor layer is formed in the p-type layer forming step. Apply to make a thin film. Examples of the application method of the coating liquid include a casting method, a spin coating method, an ink jet method, an immersion method, a spray method, a relief printing method, a gravure printing method, a gravure offset printing method, and a screen printing method. However, the application method is not limited to these, and any commonly used application method can be used.

  First, in the p-type layer forming step, a p-type organic semiconductor coating solution is applied directly or arbitrarily via an organic layer onto the electrode of the substrate on which the electrode is formed. Examples of the organic layer include PEDOT: PSS. The substrate temperature during and / or after application is set to 40 ° C. or higher. By heating the substrate to 40 ° C. or higher, a solar cell that exhibits good efficiency can be manufactured. Although not wishing to be bound by theory, it is estimated that heating the substrate changes the film quality of the p-type organic semiconductor and contributes to the good efficiency of the solar cell. Moreover, when the substrate temperature is less than 40 ° C., depending on the type of organic semiconductor, crystals are deposited before the solvent is dried, and an appropriate thin film cannot be formed. In the crystalline acene compound, the effect of heating to 40 ° C. or higher is important. Furthermore, the substrate temperature during and / or after application is preferably set to 50 ° C. or higher, and more preferably set to 100 ° C. or higher. The substrate temperature during and after application is preferably 250 ° C. or lower.

  For example, when pentacene is used as the acene-based compound, the shape of the pentacene crystal changes depending on the temperature of the substrate. Therefore, temperature control is important in developing the performance of the solar cell. In the present invention, since a thin film containing an n-type organic semiconductor is also formed by a coating method, the crystal state of the p-type organic semiconductor layer serving as a base changes the area of the interface of the P / N junction. In the production method of the present invention, for example, the P / N junction interface can be increased by the following method, which can contribute to the improvement of the efficiency of the solar cell.

1) When the p-type organic semiconductor layer is dissolved in the solvent of the n-type organic semiconductor coating solution to be applied next, the surface of the p-type organic semiconductor layer film as the base is eroded by the solvent. As a result, a state like a bulk heterojunction can be formed.
2) The film quality of the p-type organic semiconductor layer can be controlled by controlling the temperature of the p-type organic semiconductor coating solution and controlling the temperature of the substrate. As a result, since the surface of the p-type organic semiconductor layer can be made nonuniform, the p-type organic semiconductor can be used when the underlying p-type organic semiconductor layer is not substantially dissolved in the solvent of the n-type organic semiconductor coating solution. The surface shape of the layer is directly reflected in the element structure. Thereby, the contact area of the P / N junction is increased, and the solar cell characteristics are improved.

  It is also possible to combine the above 1) and 2). For example, when the p-type organic semiconductor layer is slightly dissolved in the solvent of the n-type organic semiconductor coating solution, the surface of the p-type organic semiconductor layer is made non-uniform by the methods 1) and 2) above. The contact interface between the semiconductor layer and the n-type organic semiconductor layer can be increased, and a bulk heterostructure can be imparted.

  Furthermore, in this invention, a bulk heterostructure can be formed with 1 liquid by making an n-type organic-semiconductor coating liquid contain an acene type compound. Specifically, after forming a p-type organic semiconductor layer in the p-type layer forming step, a mixed liquid containing an acene compound and an n-type organic semiconductor is applied as an n-type organic semiconductor coating solution in the thin-film forming step. Then, a thin film is produced. Also in this application, the substrate is heated to 40 ° C. or more during and / or after application. Thereby, a bulk heterojunction can be formed. That is, in this embodiment, the thin film formed in the thin film forming step is a layer having a bulk heterostructure composed of a p-type region made of an acene compound and an n-type region made of an n-type organic semiconductor.

  In the present invention, the thickness of the p-type organic semiconductor layer formed in the p-type layer forming step is preferably 5 nm or more and 5 μm or less. Further, the film thickness is more preferably 5 nm or more and 3 μm or less, and further preferably 10 nm or more and 2 μm or less. When the film thickness is 5 nm or more and 5 μm or less, the efficiency is good. In addition, the total film thickness of the p-type organic semiconductor layer and the thin film after completing the thin film forming step is preferably 10 nm or more and 7 μm or less. The total film thickness is more preferably 20 nm or more and 5 μm or less, and further preferably 30 nm or more and 3 μm or less. When the total film thickness is 10 nm or more and 7 μm or less, the conversion efficiency is good. Each thickness described above is a value measured using at least one of a stylus type step thickness meter, a digital microscope, a microscope using optical interference, and a transmission electron microscope.

Hereinafter, the production method of the present invention will be described in detail by way of specific examples.
[Example 1]
(1) Step 1: Preparation of p-type organic semiconductor coating solution containing acene-based compound Pentacene (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1-methylnaphthalene were mixed to prepare a 0.08% by mass coating solution. . Further, 15 ppm of polydimethylsiloxane was added to the coating solution. This coating solution was stirred for 1 hour on a hot plate at 200 ° C. in a nitrogen atmosphere.

(2) Step 2: Production of p-type organic semiconductor layer A glass substrate with an ITO electrode was placed on a hot plate at 200 ° C. Here, as the glass substrate with an ITO electrode, a glass substrate washed with 2-propanol and water and then dry-cleaned by UV ozone treatment was used. The substrate is allowed to stand on a hot plate for 5 minutes or more, and then the pentacene coating solution prepared in (1) above is dropped in a nitrogen atmosphere. After coating, the substrate is placed on a 200 ° C. hot plate for 30 minutes and made of pentacene. A p-type organic semiconductor layer was produced. When the thickness of the p-type organic semiconductor layer made of pentacene was measured with a microscope (Vert Scan 2.0 / Ryoka Systems Inc.) using optical interference, it was between 30 nm and 100 nm.

(3) Step 3: Preparation of thin film by applying n-type organic semiconductor coating solution 60PCBM (manufactured by SIGMA-ALDRICH: [6,6] -PhenylC ₆₁ butyric acid methyl ester) and chloroform are mixed. A 1% by weight coating solution was prepared. This coating solution was stirred at room temperature for 1 hour. This coating solution was applied on the p-type organic semiconductor layer prepared in (2) above at room temperature in a nitrogen atmosphere, and then a thin film was formed at room temperature. Then, it dried at 100 degreeC for 20 minute (s), and produced the thin film which consists of a pentacene (p-type organic semiconductor) and 60PCBM (n-type organic semiconductor). When the thickness of the thin film (the total thickness of the p-type organic semiconductor and the n-type organic semiconductor) was measured by the same method as in (2) above, it was between 150 nm and 250 nm. The thin film for organic thin film solar cells was produced by the above.

(4) Step 4: Formation of Electrode An aluminum electrode was vapor-deposited on the thin film formed in (3) above to produce an organic thin film solar cell.

[Comparative Example 1]
(1) Step 1: Preparation of p-type organic semiconductor coating solution containing acene-based compound Pentacene (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1-methylnaphthalene were mixed to prepare a 0.08% by mass coating solution. . Further, 15 ppm of polydimethylsiloxane was added to the coating solution. This coating solution was stirred for 1 hour on a hot plate at 200 ° C. in a nitrogen atmosphere.

(2) Step 2: Production of p-type organic semiconductor layer A glass substrate with an ITO electrode was washed with 2-propanol and water, and then dry-washed with UV ozone treatment. On the glass substrate with an ITO electrode, the coating solution (1) was dropped at room temperature. As a result, even after 2 hours from the dropping, the solvent did not dry, and a large number of pentacene microcrystals precipitated in the solvent, making it difficult to produce a continuous film covering the electrode. The battery could not be produced.

  ADVANTAGE OF THE INVENTION According to this invention, the thin film for organic thin film solar cells which gives an organic thin film solar cell with high conversion efficiency can be manufactured with the application | coating method which is easy to enlarge and cost reduction is possible.

1 substrate 2, 5 electrode 3 p-type organic semiconductor layer 4 n-type organic semiconductor layer

Claims (3)

A method for producing a thin film for an organic thin film solar cell comprising a substrate on which an electrode is formed, a p-type organic semiconductor, and an n-type organic semiconductor,
1) A p-type organic semiconductor coating solution containing one or more acene-based compounds is applied directly or via an organic layer on the electrode on which the electrode is formed, and the substrate is coated and / or after coating. A p-type layer forming step of forming a p-type organic semiconductor layer by setting the temperature to 40 ° C. or higher, and 2) an n-type containing at least one n-type organic semiconductor on the p-type organic semiconductor layer The manufacturing method of the thin film for organic thin film solar cells including the thin film formation process which apply | coats an organic-semiconductor coating liquid and produces a thin film. The acene compound has the following chemical formula (1):

{Wherein R _{1 to} R ₁₀ each independently represents a hydrogen atom, or an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alkoxy group, a halogen group, an acyl group, an ester group, an ether group. Represents a functional group containing one or more groups selected from the group consisting of amino groups, amide groups, cyano groups, silyl groups and photoreactive groups, and at least one of R _{1 to} R ₁₀ is other than a hydrogen atom And n is an integer from 2 to 7. } The manufacturing method of the thin film for organic thin-film solar cells of Claim 1 which is 1 or more types of compounds represented by these.   The method for producing a thin film for an organic thin film solar cell according to claim 1 or 2, wherein the acene compound is one or more compounds selected from the group consisting of pentacene, a pentacene derivative, tetracene and a tetracene derivative.

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