JP2009076683A - Organic thin-film solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin-film solar cell which is excellent in photoelectric conversion efficiency by using a C<SB>70</SB>fullerene derivative. <P>SOLUTION: The organic thin-film solar cell has: a substrate; a first electrode layer formed on the substrate; a photoelectric conversion layer formed on the first electrode layer and containing the C<SB>70</SB>fullerene derivative and an electron-donative material; and a second electrode layer formed on the photoelectric conversion layer. The C<SB>70</SB>fullerene derivative has one substituent and two kinds of position isomers, and either of the two kinds of position isomers of the C<SB>70</SB>fullereren derivative contained in the photoelectric conversion layer has a content of 95% or larger. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an organic thin film solar cell using the C ₇₀ fullerene derivatives.

  An organic thin film solar cell is a solar cell in which an organic thin film having an electron donating function and an electron accepting function is disposed between two different electrodes, and has a manufacturing process compared to an inorganic solar cell represented by silicon or the like. It has an advantage that it is easy and can be enlarged at low cost. However, organic thin-film solar cells are difficult to put into practical use because of their lower photoelectric conversion efficiency than inorganic solar cells, and increasing the photoelectric conversion efficiency is the biggest issue.

  Recently, in order to improve the photoelectric conversion efficiency of organic thin film solar cells, attempts have been made to make use of the characteristics of organic materials used in organic thin films (see Non-Patent Document 1 and Non-Patent Document 2).

  For example, as a method of expanding a pn junction portion in order to improve photoelectric conversion efficiency, a method of mixing a p-type organic semiconductor having electron donating properties and an n-type organic semiconductor having electron accepting properties is known. By mixing the p-type organic semiconductor and the n-type organic semiconductor, a pn junction at the molecular level is widely formed in the film, so that the volume that can contribute to photoelectric conversion increases.

As an example of such a mixed organic thin film solar cell, Non-Patent Document 1 uses a polyphenylene vinylene-based p-type conjugated polymer (MEH-PPV) and an n-type organic semiconductor fullerene derivative (C ₆₀ PCBM). Organic thin film solar cells.
Fullerenes and derivatives thereof can be suitably used in mixed-type organic thin-film solar cells because the charge separation state can be kept relatively long in the film.

C ₆₀ is mainly studied as fullerene. Further, since the C ₇₀ is relatively easy to obtain among the higher fullerenes other than C _60, and are (for example, see Patent Document 1) that is attracting attention C ₇₀ recently.
In general, it is known that in fullerene, as the number of carbons increases, the rise of absorption in the absorption spectrum shifts to the longer wavelength side. That, C ₆₀ C ₇₀ compared to can absorb the energy of a longer wavelength side of sunlight. Therefore, it becomes possible to cause more electricity in C _70.

In addition, it is known that removal of impurities in an organic material is effective for improving photoelectric conversion efficiency. However, depending on the type of organic material, sufficient photoelectric conversion efficiency may not be obtained even if the purity is relatively high.
Furthermore, in order to improve the photoelectric conversion efficiency, there is also known a method in which an additive is positively mixed with an organic material instead of increasing the purity of the organic material.
As described above, improvement in the photoelectric conversion efficiency is still desired.

MATERIAL STAGE vol.2, No.9 2002 p.37-42 Junichi Nakamura et al. "Organic thin-film solar cells-utilization of donor-acceptor interaction" Applied Physics Vol.71 No.4 (2002) p.425-428 Akinori Kuno "Current Status and Prospects of Organic Solar Cells" JP-T-2006-518110

  In order to further improve the photoelectric conversion efficiency, it is necessary to optimize the configuration of the photoelectric conversion layer. In particular, control of the dispersion state in a film of an organic material having a strong correlation with electrical conductivity is important for improving photoelectric conversion efficiency.

  It is known that the dispersion state of the electron-accepting material in the film affects the electron conductivity. In the region where a plurality of molecules are aggregated (aggregated), the conductivity becomes high, and the distance between the molecules increases. There is a tendency for the conductivity to be low in a remote region. For this reason, it is important to prepare conditions under which the electron-accepting materials are likely to aggregate (aggregate) in the photoelectric conversion layer.

The present invention has been made in view of the above circumstances, with C ₇₀ fullerene derivative, a main object thereof is to provide an organic thin film solar cell having excellent photoelectric conversion efficiency.

To achieve the above object, the present invention includes a substrate, a first electrode layer formed on the substrate, is formed on the first electrode layer contains a C ₇₀ fullerene derivative and the electron donating material a photoelectric conversion layer, an organic thin film solar cell and a second electrode layer formed on the photoelectric conversion layer, the C ₇₀ fullerene derivative having one substituent, two regioisomeric An organic substance characterized in that the ratio of any one of the two positional isomers of the C ₇₀ fullerene derivative contained in the photoelectric conversion layer is 95% or more. A thin film solar cell is provided.

According to the present invention, since the ratio of one of the two positional isomers of the C ₇₀ fullerene derivative is not less than a predetermined value, the position of one of the positional isomers in the photoelectric conversion layer can be reduced. Aggregation is promoted and conductivity is considered to increase. Thereby, the photoelectric conversion efficiency can be improved.

  In the above invention, the electron donating material is preferably polythiophene. This is because the energy level difference when the charge separation reaction proceeds is appropriate.

  In the present invention, it is preferable that a hole extraction layer is formed between the first electrode layer and the photoelectric conversion layer. This is because, when the first electrode layer is a hole extraction electrode, the hole extraction efficiency from the photoelectric conversion layer to the hole extraction electrode is increased by providing the hole extraction layer.

The present invention includes a substrate, a first electrode layer formed on the substrate, is formed on the first electrode layer, a photoelectric conversion layer containing a C ₇₀ fullerene derivative and the electron donating material, the photoelectric and a second electrode layer formed on the conversion layer, the C ₇₀ fullerene derivative having one substituent, two of the manufacturing method of the organic thin-film solar cell in which with regioisomer a is, from among a plurality of kinds of fullerene derivative compositions containing the C ₇₀ fullerene derivatives, most often the proportion of one of the positional isomers of the two types of position isomers of the C ₇₀ fullerene derivative And a photoelectric conversion layer forming step of forming the photoelectric conversion layer using the selected fullerene derivative composition. The method for producing an organic thin film solar cell is provided.

According to the present invention, a composition having the highest proportion of any one of the two types of positional isomers of the C ₇₀ fullerene derivative is selected from the plurality of types of fullerene derivative compositions. Since the photoelectric conversion layer is formed using the fullerene derivative composition, aggregation of one of the positional isomers is promoted in the obtained photoelectric conversion layer, and a highly conductive photoelectric conversion layer can be obtained. As a result, it is possible to produce an organic thin film solar cell that is excellent in photoelectric conversion efficiency.

  In the above invention, the electron donating material is preferably polythiophene. This is because the energy level difference when the charge separation reaction proceeds is appropriate.

In the present invention, the photoelectric conversion efficiency can be improved by setting the ratio of one of the two positional isomers of the C ₇₀ fullerene derivative to a predetermined value or more. .

C ₇₀ is not a perfect sphere, C ₇₀ fullerene derivative, if it has one substituent, have a two regioisomers by the binding position of the substituent (alpha-position isomers and β-position isomer) It has been known. The α-position isomer refers to an isomer having a substituent on the long axis of the fullerene skeleton, and the β-position isomer refers to an isomer having a substituent on the short axis of the fullerene skeleton. On the other hand, C ₆₀ is a perfect sphere, and it is known that a C ₆₀ fullerene derivative does not have a regioisomer when it has one substituent.
In addition, fullerene derivatives have a property of being easily aggregated.
Furthermore, in a photoelectric conversion layer containing a fullerene derivative that is an electron-accepting material and an electron-donating material, the dispersion state of the fullerene derivative in the layer affects the electron conductivity. In the region where the fullerene derivatives are aggregated, the conductivity tends to be high, and in the region where the distance between the fullerene derivatives is large, the conductivity tends to be low.

Accordingly, the present inventors focused on the relationship between the positional isomers and the conductive C ₇₀ fullerene derivatives, to form the photoelectric conversion layer using two mixing ratio different C ₇₀ fullerene derivative regioisomers, When the organic thin-film solar cell was produced, it turned out that a difference arises in the performance of a solar cell by the mixing ratio of two types of positional isomers. And it discovered that photoelectric conversion efficiency became high by increasing the ratio of one position isomer among two types of position isomers, and came to complete this invention.

  The reason why the photoelectric conversion efficiency is increased by increasing the proportion of one of the positional isomers is not clear in detail, but the same type of positional isomers aggregate more easily than the different types of positional isomers. This is considered to be because the conductivity of the photoelectric conversion layer is increased. Thereby, it is considered that the charge generated in the photoelectric conversion layer can be extracted to the outside with high efficiency.

  Hereinafter, the organic thin-film solar cell and the manufacturing method thereof of the present invention will be described in detail.

A. Organic thin film solar cell The organic thin film solar cell of the present invention comprises a substrate, a first electrode layer formed on the substrate, a C ₇₀ fullerene derivative and an electron donating material formed on the first electrode layer. a photoelectric conversion layer, an organic thin film solar cell and a second electrode layer formed on the photoelectric conversion layer, the C ₇₀ fullerene derivative having one substituent, two position are those having isomers, one fraction of one regioisomer of the two types of position isomers of the C ₇₀ fullerene derivative contained in the photoelectric conversion layer is characterized in that 95% or more Is.

The organic thin-film solar cell of this invention is demonstrated referring drawings.
FIG. 1 is a schematic sectional view showing an example of the organic thin film solar cell of the present invention. In the example shown in FIG. 1, the organic thin-film solar cell 10 is obtained by sequentially laminating a first electrode layer 2, a photoelectric conversion layer 3, and a second electrode layer 4 on a substrate 1. The photoelectric conversion layer 3 contains a C ₇₀ fullerene derivative and the electron donating material.

According to the present invention, since the ratio of one of the two positional isomers of the C ₇₀ fullerene derivative contained in the photoelectric conversion layer is not less than a predetermined value, It is thought that aggregation of one regioisomer is promoted. As a result, the conductivity becomes high, the charge generated in the photoelectric conversion layer can be efficiently taken out to the outside, and the photoelectric conversion efficiency can be improved.
Hereinafter, each structure of such an organic thin-film solar cell is demonstrated.

1. The photoelectric conversion layer used in the photoelectric conversion layer present invention are those containing a C ₇₀ fullerene derivative and the electron donating material. The photoelectric conversion layer contains a C ₇₀ fullerene derivative and the electron donating material is an electron accepting material is a layer having a both electron-accepting and electron-donating function, formed in the photoelectric conversion layer Charge separation occurs using the pn junction.

The C ₇₀ fullerene derivative used in the present invention has one substituent and has two kinds of positional isomers (α-position isomer and β-position isomer).

  As said substituent, what has a linear, branched or cyclic hydrocarbon group, an aryl group, and an aryl group is mentioned, for example.

  The hydrocarbon group is preferably an alkyl group, more preferably an alkyl group having 1 to 12 carbon atoms, and still more preferably an alkyl group having 2 to 7 carbon atoms. As described above, the alkyl group may be linear, branched or cyclic. Among these, at least most of the alkyl groups are preferably linear.

  The hydrocarbon group may be substituted with one or more functional groups. Examples of the functional group include carboxylic acid ester, amide, ether, lactone, lactam, urethane, carbonate, acetal, amine, and halogen. That is, the alkyl group may be substituted with one or more functional groups, and examples of the functional group include carboxylic acid ester, amide, ether, lactone, lactam, urethane, carbonate, acetal, amine, Halogen etc. are mentioned. Among these, the alkyl group preferably includes an ether and a carboxylic acid ester having an alkyl portion of 1 to 10 carbon atoms.

Examples of the aryl group include those containing a benzene ring, a thiophene ring, a pyrrole ring, a pyrrolidine ring, and a furan ring.
In addition, the aryl group itself may be substituted with one or more side chains. The side chain is preferably an alkyl group, an alkoxy group, an alkoxycarbonyl group, a C- and / or N-alkylamide group, or an aryl group.

Especially, it is preferable that the said substituent has an aryl group substituted by the alkoxycarbonyl group as a side chain. That is, the substituent preferably has an aryl group and an esterified alkanecarboxylic acid group.
Examples of the aryl include phenyl, thiophene, indole, pyrrole, furan and the like. Of these, phenyl is preferred.
Examples of the ester include linear or branched carboxylic acids having 1 to 20 carbon atoms. Of these, carboxylic acids having 3 to 7 carbon atoms are preferred. Particularly preferred are those formed from carboxylic acids having 4 carbon atoms and alkanols having 1 to 20 carbon atoms, preferably carboxylic acids having 4 carbon atoms and 1 to 4 carbon atoms. What is formed from the alkanol which has is further preferable.

Specifically, the C ₇₀ fullerene derivative is preferably a (methano) fullerene having a substituent having an aryl group and an esterified alkanecarboxylic acid group, and a functional analog of the (methano) fullerene. Preferable examples of the (methano) fullerene include those having phenylbutyric acid methyl ester as a substituent (referred to as C ₇₀ PCBM). Specific examples include [6,6] -phenyl-C ₇₁ -butyric acid methyl ester and [5,6] -phenyl-C ₇₁ -butyric acid methyl ester.

Method for synthesizing C ₇₀ fullerene derivatives described above can be similar to the method for the synthesis of the corresponding C ₆₀ fullerene derivatives. For example, it has been reported that C ₇₀ PCBM can be synthesized in the same manner as C ₆₀ PCBM (J. Appl. Phys., 98, 054503, 2005). The method for synthesizing C ₆₀ PCBM is described in detail in J. Org. Chem., 1995, 60, 532-538.

In the present invention, the ratio of one of the two positional isomers of the C ₇₀ fullerene derivative contained in the photoelectric conversion layer is 95% or more. This is because the larger the proportion of one positional isomer, the more the aggregation of the positional isomer is promoted and the conductivity can be increased.

The “ratio of any one of the two types of positional isomers” means the mass of either one of the positional isomers when the total mass of the two types of positional isomers is 100%. Say.
Further, the ratio of the above positional isomer can be measured by high performance liquid chromatography.

  Of the two types of positional isomers, the positional isomer satisfying the above ratio may be either the α-position isomer or the β-position isomer. That is, the ratio of the α-position isomer of the two types of positional isomers may be 95% or more, and the ratio of the β-position isomer of the two types of positional isomers may be 95% or more.

  As a method for increasing the ratio of one regioisomer, a method of isolation using high performance liquid chromatography can be employed.

Further, the electron donating material used in the present invention is not particularly limited as long as it has a function as an electron donor, but it is preferable that the material can be formed by a coating method. An electron donating conductive polymer material is preferable.
The 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 hetero atoms are alternately linked to single bonds, and exhibits semiconducting properties. It is. In the conductive polymer material, π conjugation is developed in the polymer main chain, so that charge transport in the main chain direction is basically advantageous. In addition, the conductive polymer material can be easily formed by a coating method by using a coating solution in which the conductive polymer material is dissolved or dispersed in a solvent. There is an advantage that it can be manufactured at low cost without requiring expensive equipment.

  Examples of the electron-donating conductive polymer material include polyphenylene, polyphenylene vinylene, polysilane, polythiophene, polycarbazole, polyvinyl carbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinyl pyrene, polyvinyl anthracene, and derivatives thereof. And copolymers thereof, or phthalocyanine-containing polymers, carbazole-containing polymers, organometallic polymers, and the like.

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 are because the energy level difference when the charge separation reaction proceeds is appropriate for the C ₇₀ fullerene derivative.

In particular, polythiophene such as polyalkylthiophene is preferable. As polythiophene, those showing crystallinity are known. In the photoelectric conversion layer containing polythiophene exhibiting such crystallinity, it is considered that the structure in the photoelectric conversion layer is controlled by self-organization of polythiophene. Specifically, the self-organization of the polythiophenes, C ₇₀ becomes fullerene derivatives tends to aggregate, is Shiryo polythiophene and C ₇₀ fullerene derivative can take a micro phase separation structure. Thereby, it is thought that electroconductivity increases.

The mass ratio of the C ₇₀ fullerene derivative and an electron donating material contained in the photoelectric conversion layer is suitably adjusted to the optimum ratio depending on the kind of electron donating material used. Specifically, it is preferable that the mass ratio of C ₇₀ fullerene derivatives (C ₇₀ fullerene derivative / electron donor material) is in the range of 0.1 to 2.0 electron-donating material, among others 0.2 Within the range of -1.0 is preferable. When the weight ratio is outside the above range, the balance between C ₇₀ fullerene derivative and the electron donating material is poor, there is a possibility that no sufficient photoelectric conversion efficiency.

  As the film thickness of the photoelectric conversion layer, the film thickness generally employed in bulk heterojunction organic thin film solar cells can be employed. Specifically, the film thickness of the photoelectric conversion layer is not particularly limited as long as it can achieve a desired photoelectric conversion efficiency, and can be within a range of 0.2 nm to 3000 nm. It is preferably within the range of 10 nm to 600 nm. When the film thickness is larger than the above range, the film resistance may be increased. On the other hand, when the film thickness is smaller than the above range, a short circuit may occur between the first electrode layer and the second electrode layer. Because there is.

2. First electrode layer The material for forming the first electrode layer used in the present invention is not particularly limited as long as it has conductivity, but the irradiation direction of light and the work function of the material for forming the second electrode layer described later. It is preferable to select appropriately considering the above.
For example, when the material for forming the second electrode layer is a material having a low work function, the material for forming the first electrode layer is preferably a material having a high work function. Examples of the material having a high work function include Au, Ag, Co, Ni, Pt, C, ITO, SnO ₂ , fluorine-doped SnO ₂ , and ZnO.
Further, when the substrate side is the light receiving surface, the first electrode layer is preferably a transparent electrode. In this case, what is generally used as a transparent electrode can be used. Specifically, In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, Zn—Sn—O, and the like can be given.

In the present invention, the total light transmittance of the first electrode layer is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. When the substrate side is a light-receiving surface, the first electrode layer can sufficiently transmit light because the total light transmittance of the first electrode layer is in the above range, and light is efficiently transmitted by the photoelectric conversion layer. It is because it can absorb.
The total light transmittance is a value measured using an SM color computer (model number: SM-C) manufactured by Suga Test Instruments Co., Ltd. in the visible light region.

In the present invention, the sheet resistance of the first electrode layer is preferably 20Ω / □ or less, more preferably 10Ω / □ or less, and particularly preferably 5Ω / □ or less. This is because if the sheet resistance is larger than the above range, the generated charge may not be sufficiently transmitted to the external circuit.
The sheet resistance is measured based on JIS R1637 (low-efficiency test method for fine ceramic thin film: 4-probe method) using a surface resistance meter (Loresta MCP: 4-terminal probe) manufactured by Mitsubishi Chemical Corporation. It is the value.

The first electrode layer may be a single layer or may be laminated using materials having different work functions.
As the film thickness of the first electrode layer, when it is a single layer, the film thickness is within a range of 0.1 to 500 nm, particularly within a range of 1 nm to 300 nm when it is composed of a plurality of layers. Preferably there is. If the film thickness is smaller than the above range, the sheet resistance of the first electrode layer may become too large, and the generated charge may not be sufficiently transmitted to the external circuit. On the other hand, if the film thickness is larger than the above range, This is because the total light transmittance is lowered and the photoelectric conversion efficiency may be lowered.

  The first electrode layer may be formed on the entire surface of the substrate or may be formed in a pattern.

  Furthermore, the shape of the first electrode layer may be a flat shape, or may be an uneven shape such as a texture structure, a pyramid structure, a wave structure, a comb structure, or a nano pillow structure. For example, when the shape of the first electrode layer is uneven, incident light is scattered by the uneven shape of the first electrode layer, so that the photoelectric conversion layer described later can take in much light. Thereby, since light can be used effectively, energy conversion efficiency can be improved.

3. Second electrode layer The second electrode layer used in the present invention is an electrode facing the first electrode layer. The material for forming the second electrode layer is not particularly limited as long as it has conductivity, but may be appropriately selected in consideration of the light irradiation direction, the work function of the material for forming the first electrode layer, and the like. preferable.
For example, when the substrate side is a light receiving surface, the first electrode layer is a transparent electrode. In such a case, the second electrode layer may not be transparent.
In the case where the first electrode layer is formed using a material having a high work function, the second electrode layer is preferably formed using a material having a low work function. Specific examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, Zr, and LiF.

The second electrode layer may be a single layer or may be laminated using materials having different work functions.
When the second electrode layer is a single layer, the film thickness is in the range of 0.1 nm to 500 nm, particularly 1 nm to 500 nm. It is preferable to be within the range of 300 nm. If the film thickness is smaller than the above range, the sheet resistance of the second electrode layer may become too large, and the generated charge may not be sufficiently transmitted to the external circuit. On the other hand, if the film thickness is larger than the above range, This is because the total light transmittance is lowered and the photoelectric conversion efficiency may be lowered.

  Further, the second electrode layer may be formed on the entire surface of the photoelectric conversion layer or may be formed in a pattern.

4). Substrate The substrate used in the present invention is not particularly limited, whether it is transparent or opaque. For example, when the substrate side is a light receiving surface, it is a transparent substrate. Is preferred. The transparent substrate is not particularly limited, and for example, a non-flexible transparent rigid material such as quartz glass, Pyrex (registered trademark), synthetic quartz plate, or a transparent resin film, an optical resin plate, etc. The transparent flexible material which has flexibility can be mentioned.

  In the present invention, among the above, the substrate is preferably a flexible material such as a transparent resin film. Transparent resin films are excellent in processability, and are useful in the realization of organic thin-film solar cells that reduce manufacturing costs, reduce weight, and are difficult to break, and expand the applicability to various applications such as application to curved surfaces. is there.

5). Hole extraction layer In the present invention, a hole extraction layer is preferably formed between the photoelectric conversion layer and the hole extraction electrode. When the first electrode layer is a hole extraction electrode, a hole extraction layer 5 is formed between the first electrode layer 2 and the photoelectric conversion layer 3, for example, as shown in FIG. In general, since the organic thin-film solar cell can be more stably produced by laminating from the hole extraction electrode side, the first electrode layer is usually the hole extraction electrode, and the positive electrode layer is normally placed between the first electrode layer and the photoelectric conversion layer. A hole extraction layer is formed.

  The hole extraction layer is a layer provided so that holes can be easily extracted from the photoelectric conversion layer to the hole extraction electrode. Thereby, since the hole extraction efficiency from the photoelectric conversion layer to the hole extraction electrode is increased, the photoelectric conversion efficiency can be improved.

The material used for such a hole extraction layer is not particularly limited as long as it is a material that stabilizes the extraction of holes from the photoelectric conversion layer to the hole extraction electrode. Specifically, conductive organic compounds such as doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Also, a thin film of metal such as Au, In, Ag, Pd, etc. can be used. Furthermore, a thin film of metal or the like may be formed alone or in combination with the above organic material.
Among these, polyethylenedioxythiophene (PEDOT) and triphenyldiamine (TPD) are particularly preferably used.

  The film thickness of the hole extraction layer is preferably in the range of 10 nm to 200 nm when the organic material is used, and in the range of 0.1 nm to 5 nm in the case of the metal thin film. It is preferable.

6). Electron Extraction Layer In the present invention, an electron extraction layer may be formed between the photoelectric conversion layer and the electron extraction electrode. When the second electrode layer is an electron extraction electrode, an electron extraction layer is formed between the photoelectric conversion layer and the second electrode layer.

  The electron extraction layer is a layer provided so that electrons can be easily extracted from the photoelectric conversion layer to the electron extraction electrode. Thereby, since the electron extraction efficiency from the photoelectric conversion layer to the electron extraction electrode is increased, the photoelectric conversion efficiency can be improved.

  The material used for such an electron extraction layer is not particularly limited as long as it is a material that stabilizes the extraction of electrons from the photoelectric conversion layer to the electron extraction electrode. Specifically, conductive organic compounds such as doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Moreover, the metal dope layer with an alkali metal or alkaline-earth metal is mentioned. Suitable materials include bathocuproin (BCP) or bathophenantrone (Bphen) and metal doped layers such as Li, Cs, Ba, Sr.

7). Other constituent members The organic thin-film solar cell of the present invention may have constituent members to be described later as needed in addition to the constituent members described above. For example, the organic thin film solar cell of the present invention includes a protective sheet, a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an antifouling layer, a high light reflection layer, a light containment layer, an ultraviolet / infrared shielding layer, a sealing You may have functional layers, such as a material layer. In addition, an adhesive layer may be formed between the functional layers depending on the layer configuration.
These functional layers can be the same as those described in JP 2007-73717 A.

B. Next, the manufacturing method of the organic thin film solar cell of this invention is demonstrated.
The method of manufacturing an organic thin-film solar cell of the present invention contains a substrate, a first electrode layer formed on the substrate, is formed on the first electrode layer, a C ₇₀ fullerene derivative and the electron donating material a photoelectric conversion layer, and a second electrode layer formed on the photoelectric conversion layer, the C ₇₀ fullerene derivative having one substituent, those having two regioisomers a manufacturing method of an organic thin film solar cell, among a plurality of kinds of fullerene derivative compositions containing the C ₇₀ fullerene derivative, one regioisomeric one of two regioisomers of the C ₇₀ fullerene derivative It has the photoelectric conversion layer formation process which selects the thing with the largest body ratio, and forms the said photoelectric converting layer using the selected said fullerene derivative composition.

  In FIG. 3, an example of the manufacturing method of the organic thin-film solar cell of this invention is shown. As shown in FIG. 3, the manufacturing method of the organic thin-film solar cell of this invention is the 1st electrode layer formation process (FIG. 3 (a)) which forms the 1st electrode layer 2 on the board | substrate 1, for example, A photoelectric conversion layer forming step (FIG. 3 (b)) for forming a photoelectric conversion layer 3 using a predetermined fullerene derivative composition on one electrode layer 2, and forming a second electrode layer 4 on this photoelectric conversion layer 3. And a second electrode layer forming step (FIG. 3C).

In the photoelectric conversion layer forming step, for example, preparing a plurality of kinds of fullerene derivative composition initially containing C ₇₀ fullerene derivative, and then from among these fullerene derivative composition, two regioisomeric of C ₇₀ fullerene derivatives One having the largest proportion of any one of the positional isomers is selected, and then a photoelectric conversion layer is formed using the selected fullerene derivative composition.

According to the present invention, in the photoelectric conversion layer forming step, as described above, one of the two types of positional isomers of the C ₇₀ fullerene derivative is selected from the plural types of fullerene derivative compositions. Since the photoelectric conversion layer is formed using the selected fullerene derivative composition, the aggregation of one of the positional isomers is promoted in the formed photoelectric conversion layer. Conceivable. As a result, a highly conductive photoelectric conversion layer can be formed, and an organic thin film solar cell excellent in photoelectric conversion efficiency can be obtained.

The manufacturing method of the organic thin-film solar cell of this invention should just have a photoelectric converting layer formation process at least, and may have a 1st electrode layer forming process, a 2nd electrode layer forming process, etc. as mentioned above. Good.
Hereinafter, each process of the manufacturing method of the organic thin-film solar cell of this invention is demonstrated.

1. The photoelectric conversion layer forming step in the photoelectric conversion layer forming step The present invention is, among a plurality of kinds of fullerene derivative compositions containing the C ₇₀ fullerene derivative, one of the two types of position isomers of the C ₇₀ fullerene derivative In this step, the one having the largest proportion of one positional isomer is selected, and the photoelectric conversion layer is formed using the selected fullerene derivative composition.

In this step, first, preparing a plurality of kinds of fullerene derivative compositions containing C ₇₀ fullerene derivatives. Since the C ₇₀ fullerene derivative has two kinds of positional isomers, the above-mentioned plural kinds of fullerene derivative compositions have different mixing ratios of the two kinds of positional isomers (α-position isomer: β-position isomer). is assumed. Next, from the plural kinds of fullerene derivative compositions having different mixing ratios of the two kinds of positional isomers, the one having the highest ratio of one of the two kinds of positional isomers is selected. To do.
For example, when preparing a fullerene derivative composition in which α-position isomer: β-position isomer = 98: 2 and a fullerene derivative composition in which α-position isomer: β-position isomer = 87: 13 are prepared, A fullerene derivative composition in which the α-position isomer: β-position isomer = 98: 2 having the highest proportion of the α-position isomer among the two types of positional isomers is selected.

Fullerene derivative composition, is not particularly limited as long as it contains a C ₇₀ fullerene derivative may be one containing, for example only C ₇₀ fullerene derivative, or dissolved C ₇₀ fullerene derivative in the solvent It may be dispersed.
Since the C ₇₀ fullerene derivative was described in detail in the section of the photoelectric conversion layer in the above “A. Organic thin film solar cell”, description thereof is omitted here.

As a method for forming the photoelectric conversion layer is not particularly limited as long as it can be uniformly formed to a predetermined thickness, a photoelectric conversion layer containing a C ₇₀ fullerene derivative and the electron donating material A method of applying a coating liquid for coating is preferably used. This is because with such a method, the photoelectric conversion layer can be formed in the atmosphere, and the cost can be reduced and the area can be easily increased.

Examples of a method for preparing a coating liquid for a photoelectric conversion layer include a method of dissolving or dispersing a selected fullerene derivative composition and an electron-donating material in a solvent, or dissolving a selected fullerene derivative composition in a solvent. Examples thereof include a method of mixing a dispersed acceptor solution and a donor solution in which an electron donating material is dispersed in a solvent.
Since the electron donating material is described in detail in the section of the photoelectric conversion layer of the above “A. Organic thin film solar cell”, description thereof is omitted here.

The method for applying the photoelectric conversion layer coating solution is not particularly limited as long as it can uniformly apply the photoelectric conversion layer coating solution. For example, a die coating method, a spin coating method, a dip coating method, and the like. Examples thereof include a coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method. Among these, a spin coating method can be preferably used. In the spin coating method, it is easy to accurately form a photoelectric conversion layer so as to have a predetermined film thickness, and the photoelectric conversion layer coating liquid can be applied with low shear stress. if C ₇₀ fullerene derivative with a layer coating liquid are aggregated it is because readily be formed while to aggregate C ₇₀ fullerene derivatives.

After application of the coating liquid for photoelectric conversion layer, a drying treatment for drying the formed coating film may be performed. It is because productivity can be improved by removing the solvent etc. which are contained in the coating liquid for photoelectric conversion layers at an early stage.
As a method for the drying treatment, for example, a general method such as heat drying, air drying, or vacuum drying can be used.

  In addition, since the other point of the photoelectric converting layer was described in detail in the section of the photoelectric converting layer of the above-mentioned “A. Organic thin film solar cell”, description here is omitted.

2. First electrode layer forming step The first electrode layer forming step in the present invention is a step of forming the first electrode layer on the substrate.
As a method for forming the first electrode layer, a general electrode forming method can be used, for example, a PVD method such as a vacuum deposition method, a sputtering method, an ion plating method, or a dry coating method such as a CVD method. Can be mentioned. Moreover, the wet coating method which apply | coats the coating liquid etc. which contain ITO microparticles | fine-particles can also be used.
Further, the patterning method of the first electrode layer is not particularly limited as long as it is a method capable of accurately forming the first electrode layer in a desired pattern, and examples thereof include a photolithography method. .
In addition, since it is the same as that of what was described in the term of the 1st electrode layer of said "A. organic thin film solar cell" about the other point of a 1st electrode layer, description here is abbreviate | omitted.

3. Second electrode layer forming step The second electrode layer forming step in the present invention is a step of forming a second electrode layer on the photoelectric conversion layer.
As a method for forming the second electrode layer, a general electrode forming method can be used, for example, a PVD method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a dry coating method such as a CVD method. be able to. Moreover, the wet coating method apply | coated using the metal paste etc. containing metal colloids, such as Ag, can also be used.
Further, the patterning method of the second electrode layer is not particularly limited as long as it can accurately form the second electrode layer in a desired pattern, and examples thereof include a photolithography method. .
In addition, since it is the same as that of what was described in the term of the 2nd electrode layer of said "A. organic thin film solar cell" about the other point of a 2nd electrode layer, description here is abbreviate | omitted.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[Example]
An SiO ₂ thin film was formed on the surface of a 125 μm thick PEN film substrate by the PVD method. Next, a reactive ion plating method using a pressure gradient plasma gun (power: 3.7 kW, oxygen partial pressure: 73%, film forming pressure: 0.3 Pa, film forming rate: 150 nm / min on the upper surface of the SiO ₂ thin film An ITO film (film thickness: 150 nm, sheet resistance: 20Ω / □), which is a transparent electrode, was formed by a substrate temperature of 20 ° C.). Thereafter, patterning was performed by etching to produce a substrate on which an ITO pattern was formed. Next, the substrate on which the ITO pattern was formed was cleaned using acetone, a substrate cleaning solution, and IPA.

  Next, a conductive polymer paste (poly- (3,4-ethylenedioxythiophene) dispersion) was formed on the substrate on which the ITO pattern was formed by spin coating, and then 30 ° C. at 30 ° C. It was dried for a minute to form a hole extraction layer (film thickness 100 nm).

Next, C ₇₀ PCBM ([6,6] -phenyl-C ₇₁ -butyric acid mettric ester), which was confirmed by high performance liquid chromatography to confirm that the α-isomer ratio was 98%, was prepared. This C ₇₀ PCBM and polythiophene (P3HT: poly (3-hexylthiophene-2,5-diyl)) were dissolved in chlorobenzene to prepare a coating solution for a photoelectric conversion layer having a solid content concentration of 1.4 wt%. Next, this photoelectric conversion layer coating solution was applied on the hole extraction layer by a spin coating method at a rotation speed of 600 rpm to form a photoelectric conversion layer. Subsequently, the substrate on which the photoelectric conversion layer was formed was heated and dried on a hot plate at a temperature of 150 ° C.

  Next, a Ca film (30 nm) and an Al film (80 nm) were sequentially formed on the substrate by a vacuum evaporation method to form a metal electrode. Finally, it was sealed from above the metal electrode with a sealing glass material and an adhesive sealing material to obtain an organic thin film solar cell.

[Comparative example]
The organic thin film solar cell was formed in the same manner as in Example except that C ₇₀ PCBM, in which the ratio of α-position isomer was confirmed to be 87% by high performance liquid chromatography when forming the photoelectric conversion layer, was used. Was made.

[Evaluation]
Regarding the proportion of the α-isomer, as described above, the mixing proportion of the α-isomer and the β-isomer was measured by high performance liquid chromatography.

Regarding the solar cell characteristics, A. The current-voltage characteristics were evaluated by applying voltage with a source measure unit (HP, HP4100) using M1.5 and simulated sunlight (100 mW / cm ² ) as an irradiation light source.
The photoelectric conversion efficiency of the organic thin film solar cell of the example was about 3.5%, and the photoelectric conversion efficiency of the organic thin film solar cell of the comparative example was about 3.0%. In the example, the photoelectric conversion efficiency was about 20% higher than that of the comparative example.

It is a schematic sectional drawing which shows an example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is process drawing which shows an example of the manufacturing method of the organic thin film solar cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... 1st electrode layer 3 ... Photoelectric conversion layer 4 ... 2nd electrode layer 5 ... Hole extraction layer 10 ... Organic thin film solar cell

Claims (5)

A substrate, a first electrode layer formed on the substrate, is formed on the first electrode layer, a photoelectric conversion layer containing a C ₇₀ fullerene derivative and an electron donative material, formed on the photoelectric conversion layer An organic thin film solar cell having a second electrode layer formed,
The C ₇₀ fullerene derivative has one substituent and two kinds of positional isomers;
The organic thin film solar cell, wherein the ratio of either of the regioisomers of the two regioisomers of the C ₇₀ fullerene derivative contained in the photoelectric conversion layer is 95% or more.   The organic thin film solar cell according to claim 1, wherein the electron donating material is polythiophene.   The organic thin-film solar cell according to claim 1, wherein a hole extraction layer is formed between the first electrode layer and the photoelectric conversion layer. A substrate, a first electrode layer formed on the substrate, is formed on the first electrode layer, a photoelectric conversion layer containing a C ₇₀ fullerene derivative and an electron donative material, formed on the photoelectric conversion layer A C ₇₀ fullerene derivative having one substituent and having two kinds of positional isomers, and a method for producing an organic thin-film solar cell comprising:
Among a plurality of kinds of fullerene derivative compositions containing the C ₇₀ fullerene derivatives, select the one the proportion of one of the positional isomers of two regioisomers of the C ₇₀ fullerene derivative is highest, The manufacturing method of the organic thin film solar cell characterized by having the photoelectric converting layer formation process which forms the said photoelectric converting layer using the selected said fullerene derivative composition.   The method for producing an organic thin film solar cell according to claim 4, wherein the electron donating material is polythiophene.

Images