JP2011035258A - Organic thin-film solar cell and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin-film solar cell which is reducible in manufacturing cost by simplifying manufacturing processes. <P>SOLUTION: The organic thin-film solar cell includes a metal electrode substrate 10, a conductive film 12 containing a compound such that metal atoms are bonded to each other through an oxygen atom, and are each bonded at least to an oxygen atom of any of an alkoxyl group and a hydroxyl group, and provided on a surface of the metal electrode substrate 10, a photoelectric conversion film 14 containing an electron donative material and an electron receptive material and provided on a surface of the conductive film 12, and a transparent electrode 16 provided on a surface of the photoelectric conversion film 14. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic thin film solar cell and a method for manufacturing the same.

  The organic thin film solar cell manufacturing method is still mostly occupied by dry processes such as vapor deposition. The dry process is often adopted when constructing the transparent electrode, the electron transport layer, and the back surface metal electrode not only in the low molecular vapor deposition type but also in the polymer coated type organic thin film solar cell. The dry process requires a vacuum film-forming environment and makes the process of manufacturing an organic thin-film solar cell complicated in the process. Therefore, the manufacturing cost is higher than that of the wet process. Therefore, in recent years, there is a demand for a method for manufacturing an organic thin-film solar cell that can reduce the manufacturing cost without using a dry process.

  However, as one method, considering the formation of the electron transport layer and the backside metal electrode on the photoelectric conversion layer by a method other than vapor deposition, it is possible to obtain a good contact interface between layers and an electrochemically good contact interface. It becomes difficult. For example, in the case of forming by a coating method, the metal material must be dispersed with a limited solvent that is not compatible with the lower photoelectric conversion layer, and the method does not hinder the action of the electron transport layer and the back surface metal electrode. There must be. Thus, in the conventional method for manufacturing an organic thin-film solar cell in which necessary layers are stacked on a substrate with a transparent electrode, a method other than vapor deposition and generally a dry process can be employed for the electron transport layer and the back surface metal electrode. It was difficult to reduce the manufacturing cost.

  In view of the above problems, an object of the present invention is to provide an organic thin-film solar cell capable of reducing the manufacturing cost by changing and simplifying the manufacturing process and partially moving away from the dry process, and a manufacturing method thereof. There is.

  According to the first aspect of the present invention, a compound in which a metal electrode substrate is bonded to metal atoms via oxygen atoms, and each metal atom is bonded to at least one of an alkoxyl group and a hydroxyl group. A conductive film provided on the surface of the metal electrode substrate, a photoelectric conversion film provided on the surface of the conductive film, including an electron donating material and an electron accepting material, and provided on the surface of the photoelectric conversion film An organic thin film solar cell comprising a transparent electrode is provided.

  According to the second aspect of the present invention, a metal alkoxide-containing solution is applied to the surface of the metal foil, the metal atoms are bonded through oxygen atoms, and each of the metal atoms is at least an alkoxyl group and a hydroxyl group. A step of forming a conductive film containing a compound bonded to any of the oxygen atoms, a step of applying a photoelectric conversion film containing an electron-donating material and an electron-accepting material to the surface of the conductive film, and a surface of the photoelectric conversion film A method for producing an organic thin-film solar cell including a step of forming a transparent electrode is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the organic thin-film solar cell and its manufacturing method with which manufacturing cost was reduced by changing and simplifying a manufacturing process and trying to escape from a partial dry process.

It is sectional drawing which shows an example of the organic thin film solar cell which concerns on embodiment of this invention. It is process sectional drawing (the 1) which shows an example of the manufacturing method of the organic thin-film solar cell which concerns on embodiment of this invention. It is process sectional drawing (the 2) which shows an example of the manufacturing method of the organic thin film solar cell which concerns on embodiment of this invention. It is process sectional drawing (the 3) which shows an example of the manufacturing method of the organic thin film solar cell which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments of the present invention exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention is based on the material and shape of component parts. The structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  As shown in FIG. 1, the organic thin film solar cell according to the embodiment of the present invention includes a metal electrode substrate 10, a conductive film 12 provided on the surface of the metal electrode substrate 10, and a photoelectric conversion film provided on the surface of the conductive film 12. 14. A transparent electrode 16 provided on the surface of the photoelectric conversion film 14 is provided. The conductive film 12 includes a compound in which metal atoms are bonded through oxygen atoms, and each metal atom is bonded to at least one of an alkoxyl group and a hydroxyl group. The photoelectric conversion film 14 includes an electron donating material and an electron accepting material.

  As the metal electrode substrate 10, a metal foil such as aluminum (Al), titanium (Ti), stainless steel (SUS) is used. In particular, Al that is easy to process is preferable as the material of the metal electrode substrate 10.

The conductive film 12 is formed by a sol-gel method using a metal alkoxide (M (OR) _x : M is a metal, O is oxygen, R is an alkyl group, and x is a valence of the metal) as a raw material. As the metal M, metals such as titanium (Ti 2), zinc (Zn), and zirconium (Zr) are used. Titanium alkoxide includes titanium tetraethoxide, titanium tetraisopropoxide, titanium tetranormal isopropoxide, titanium tetraisobutoxide, titanium tetra-t-butoxide, titanium tetranormal butoxide, tetranormal butyl titanate dimer, titanium tetra-2 -Ethylhexoxide, diisopropoxy bistriethanolaminate titanium, tetrastearyl titanate, etc. are used. As the zinc alkoxide, zinc tetraethoxide, zinc tetraisopropoxide, zinc tetranormal propoxide, zinc tetraisobutoxide, zinc tetra-t-butoxide, zinc tetranormal butoxide and the like are used. Examples of the zirconium alkoxide include zirconium tetraethoxide, zirconium tetraisopropoxide, zirconium tetranormal propoxide, zirconium tetraisobutoxide, zirconium tetra-t-butoxide, zirconium tetranormal butoxide and the like.

  For example, a metal alkoxide solution diluted with a solvent such as isopropyl alcohol (IPA) is prepared. A metal alkoxide solution is applied to the surface of the metal foil in the air. On the surface of the metal foil, hydrolysis and polycondensation reaction of the metal alkoxide occur due to moisture in the atmosphere. For example, hydrolysis of a metal alkoxide is represented by the following formula.

M (OR) _x + H ₂ O → M (OR) _x-1 (OH) + ROH (1)

When the reaction further proceeds, the alkoxyl group (—OR) is hydrolyzed to a hydroxyl group (—OH), and finally a metal hydroxide (M (OH) _x ) is generated.

  The polycondensation reaction between the organometallic compound or metal hydroxide produced by hydrolysis is represented by the following formula, for example.

2M (OR) _x-1 (OH) → (OR) _x-1 MOM (OR) _x-1 + H ₂ O (2)

2M (OH) _x → (OH) _x-1 MOM (OH) _x-1 + H ₂ O (3)

A colloidal solution (sol) is generated by the dehydration condensation polymerization reaction represented by the chemical formulas (1) to (3). Further, when the dehydration condensation polymerization reaction is accelerated, the particles in the colloidal solution lose fluidity and form a solid (gel). In this way, the conductive film 12 is formed.

  In the conductive film 12, metal atoms are bonded to each other through oxygen atoms, and each metal atom is bonded to at least one of an alkoxyl group and a hydroxyl group. The conductive film 12 has conductivity. In addition, the photoelectric conversion film 14 can be uniformly applied to the surface of the conductive film 12 with good adhesion.

  The film thickness of the conductive film 12 is, for example, in the range of 5 nm to 50 nm, preferably in the range of 10 nm to 30 nm. If the thickness of the conductive film 12 is less than 5 nm, it is difficult to uniformly apply the photoelectric conversion film 14 with good adhesion. If the thickness of the conductive film 12 is greater than 50 nm, the resistance increases and the photoelectric conversion efficiency decreases.

  The photoelectric conversion film 14 has a bulk heterojunction in which an electron donating material and an electron accepting material are mixed, or a heterojunction in which an electron accepting material film is stacked on the electron donating material film. In order to increase the photoelectric conversion efficiency, a bulk heterojunction is desirable.

  The film thickness of the photoelectric conversion film 14 is, for example, in the range of 0.2 nm to 3000 nm, and preferably in the range of 1 nm to 600 nm. If the film thickness of the photoelectric conversion film 14 is thicker than 3000 nm, the volume resistance of the photoelectric conversion film 14 may increase. On the other hand, if the film thickness is less than 0.2 nm, light may not be sufficiently absorbed or a short circuit may occur between the electrodes.

The electron donating material of the photoelectric conversion film 14 is not particularly limited as long as it has a function as an electron donor, but is preferably a film that can be formed by a wet coating method. Among these, an electron donating conductive polymer material is preferable. A conductive polymer is a so-called π-conjugated polymer, which is composed of a π-conjugated system in which double bonds or triple bonds containing carbon-carbon or heteroatoms are alternately linked to single bonds, and exhibits semiconductor properties. It is. In addition, since the conductive polymer material can be easily formed by a wet coating method by using a coating solution in which the conductive polymer material is dissolved or dispersed in a solvent, a large-area organic thin film solar cell As an electron-donating material, for example, polythiophene (P3HT), polyphenylene, polyphenylene vinylene, polysilane, polycarbazole, polyvinyl carbazole, porphyrin, polyacetylene, polypyrrole, Polymer materials such as polyaniline, polyfluorene, polyvinylpyrene, polyvinylanthracene, and derivatives thereof, and copolymers thereof, or phthalocyanine-containing polymers, carbazole-containing polymers, and organometallic polymers are used. Among the above, thiophene-fluorene copolymer, polyalkylthiophene, phenylene ethynylene-phenylene vinylene copolymer, phenylene ethynylene-thiophene copolymer, phenylene ethynylene-fluorene copolymer, fluorene-phenylene vinylene copolymer A thiophene-phenylene vinylene copolymer is preferably used. These electron donating materials can form a heterojunction in which the energy level difference of the lowest unoccupied molecular orbital (LUMO) is appropriate for many electron accepting materials.

The electron-accepting material of the photoelectric conversion film 14 is not particularly limited as long as it has a function as an electron acceptor, but it is preferable that the film can be formed by a wet coating method. Examples of the electron-accepting material include polyphenylene vinylene, polyfluorene, and derivatives thereof, and polymer materials such as copolymers thereof, carbon nanotubes (CNT), phenyl C61-butyric acid methyl ester (PCBM), and the like. Fullerene derivatives, cyano (CN) group or trifluoromethyl (CF ₃ ) group-containing polymers, and (CF ₃ ) group-substituted polymers.

The transparent electrode 16 is not particularly limited as long as it is a material having conductivity and transparency. For example, the transparent electrode 16, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO _2), SnO _2, zinc oxide doped with fluorine (F) (ZnO), Al-doped ZnO, oxide Zinc tin (ZnSnO) or the like is used.

  The total light transmittance of the transparent electrode 16 is 85% or more, preferably 90% or more, and more preferably 92% or more. If the total light transmittance of the transparent electrode 16 is 85% or more, the transparent electrode 16 can sufficiently transmit light, and the photoelectric conversion film 14 can efficiently absorb light. The transparent electrode 16 may be a single layer or a laminate of different transparent conductive materials. The film thickness of the transparent electrode 16 is in the range of 0.1 nm to 500 nm, preferably in the range of 1 nm to 300 nm. When the film thickness is less than 0.1 nm, the sheet resistance of the transparent electrode 16 becomes too large, and it becomes difficult to sufficiently transmit the generated photocharge to the external circuit. On the other hand, when the film thickness is thicker than 500 nm, the total light transmittance is lowered and the photoelectric conversion efficiency is lowered.

  In a conventional organic thin film solar cell, a photoelectric conversion film is provided on a transparent substrate on which a transparent electrode is formed, and a metal electrode is formed on the photoelectric conversion film by a vapor deposition method. On the other hand, in the organic thin film solar cell according to the embodiment of the present invention, the photoelectric conversion film 14 is formed on the surface of the conductive film 12 formed by the sol-gel method on the surface of the metal electrode substrate 10 of the aluminum metal foil. A transparent electrode is formed on the substrate. As described above, in the embodiment of the present invention, the metal electrode substrate 10 serving as a base material is provided without using a vapor deposition method.

  In addition, when the photoelectric conversion film is directly applied and formed on the metal foil, a coupling agent such as an aminosilane is previously applied to the surface of the metal foil to improve uniformity and adhesion. However, such a coupling agent is usually an insulating layer and inhibits the electrode action of the metal electrode. In the embodiment of the present invention, the conductive film 12 is formed on the surface of the metal electrode substrate 10 by the sol-gel method. The conductive film 12 has conductivity and also has a coupling agent effect. Therefore, the photoelectric conversion film 14 can be uniformly formed on the surface of the conductive film 12 with good adhesion.

  Next, the manufacturing method of the organic thin-film solar cell concerning embodiment of this invention is demonstrated using process sectional drawing shown in FIGS.

  As shown in FIG. 2, for example, the surface of an aluminum metal foil (metal electrode substrate 10) having a thickness of about 25 μm is degreased and cleaned. A solution obtained by diluting a metal alkoxide such as tetranormal butyl titanate to about 20% with IPA is applied to the surface of the cleaned metal foil by bar coating or the like. In the applied film, a sol-gel reaction of metal alkoxide occurs in the atmosphere, and a solidified conductive film 12 is formed. A trace amount of IPA remains in the conductive film 12. The thickness of the conductive film 12 is about 20 nm, for example. Note that the conductive film 12 may be formed using a spin coating method, a dipping method, or the like.

  P3HT (poly (3-hexylthiophene-2,5-diyl): Aldrich) and PCBM ([6,6] -phenyl-C61-butyric acid mettric ester: Nano-C) such as bromobenzene, o-dichlorobenzene, etc. And a coating solution having a solid content concentration of about 2.5% by weight and about 1% by weight, respectively, is prepared. As shown in FIG. 3, the prepared coating solution is apply | coated on the electrically conductive film 12 with the bar coating method, and the photoelectric converting film 14 is formed. Thereafter, the conductive film 12 and the photoelectric conversion film 14 are dried at about 100 ° C. for about 2 minutes. Note that the photoelectric conversion film 14 may be formed using a spin coating method, a dipping method, or the like.

  As shown in FIG. 4, a transparent electrode 16 such as an ITO film is formed on the surface of the photoelectric conversion film 14. For example, an ITO film is formed by low-temperature ion plating under the conditions of a power of about 4 kW, a pressure of 0.1 Pa, a film formation rate of about 200 nm / hour, and a substrate temperature of about −10 ° C. The formed transparent electrode 16 has a thickness of about 160 nm and a sheet resistance of about 27Ω / □. Thus, an organic thin film solar cell is manufactured.

  The solar cell characteristics of the manufactured organic thin film solar cell were evaluated. Current-voltage characteristics were measured using a current-voltage source such as a source measure unit. The operation of the organic thin film solar cell was able to be obtained from the measured current-voltage characteristics.

  According to the method of manufacturing an organic thin film solar cell according to the embodiment of the present invention, a metal foil is used for the metal electrode substrate 10. The conductive film 12 and the photoelectric conversion film 14 are formed by a coating method. The transparent electrode 16 is formed on the photoelectric conversion film 14 by an ion plating method or the like. As described above, in the embodiment of the present invention, the steps of forming the electron transport layer and the back surface metal electrode by the conventional vapor deposition method can be omitted, and the manufacturing process can be simplified. Furthermore, it is not necessary to use a substrate on which an expensive transparent electrode is formed. Based on this, the manufacturing cost of the organic thin film solar cell can be reduced.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment of the present invention, the transparent electrode 16 is provided on the surface of the photoelectric conversion film 14. However, a hole extraction layer may be provided between the transparent electrode 16 and the photoelectric conversion film 14. The hole extraction layer is for easily extracting holes generated by the photoelectric conversion film 14 to the transparent electrode 16 that is a hole extraction electrode. Thereby, since the hole extraction efficiency from the photoelectric conversion film 14 to the transparent electrode 16 is increased, the photoelectric conversion efficiency can be improved.

  As described above, the present invention naturally includes various embodiments that are not described herein. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 10 ... Metal electrode substrate 12 ... Conductive film 14 ... Photoelectric conversion film 16 ... Transparent electrode

Claims (8)

A metal electrode substrate;
A conductive film provided on the surface of the metal electrode substrate, wherein metal atoms are bonded through oxygen atoms, and each of the metal atoms further includes a compound bonded to at least one of an alkoxyl group and a hydroxyl group. When,
A photoelectric conversion film provided on the surface of the conductive film, comprising an electron donating material and an electron accepting material;
An organic thin film solar cell comprising: a transparent electrode provided on a surface of the photoelectric conversion film.   The organic thin film solar cell according to claim 1, wherein the metal electrode substrate is an aluminum metal foil.   The organic thin film solar cell according to claim 1 or 2, wherein the conductive film contains any one of titanium, zinc, and zirconium.   The thickness of the said electrically conductive film is the range of 5 nm to 50 nm, The organic thin film solar cell of any one of Claims 1-3 characterized by the above-mentioned. A compound in which a metal alkoxide-containing solution is applied to the surface of a metal foil, metal atoms are bonded to each other through oxygen atoms, and each of the metal atoms is bonded to at least one of an alkoxyl group and a hydroxyl group. Forming a conductive film comprising:
Applying a photoelectric conversion film containing an electron donating material and an electron accepting material on the surface of the conductive film;
And a step of forming a transparent electrode on the surface of the photoelectric conversion film.   The method for producing an organic thin film solar cell according to claim 5, wherein the metal foil is an aluminum metal foil.   The method for producing an organic thin-film solar cell according to claim 5 or 6, wherein the metal alkoxide is any one of titanium alkoxide, zinc alkoxide, and zirconium alkoxide.   The method for producing an organic thin-film solar cell according to claim 5, wherein the conductive film is applied with a thickness in the range of 5 nm to 50 nm.

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