JP2014027269A - Photoelectric conversion element, solar cell, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which exhibits higher photoelectric conversion efficiency, a solar cell, and a solar cell module.SOLUTION: The photoelectric conversion element includes a pair of electrodes, an active layer located between the electrodes, and an electron extraction layer located between the active layer and one of the electrodes. The electron extraction layer includes a mixture layer containing at least one alkali metal element selected from the group consisting of lithium, sodium, and potassium, and an oxide of a metal element different from alkali metal elements. In the mixture layer, the total number of lithium atoms, sodium atoms, and potassium atoms is 0.3 to 30% inclusive with respect to the number of atoms of the metal element.

Description

  The present invention relates to a photoelectric conversion element, a solar cell using the photoelectric conversion device, and a solar cell module.

  In recent years, organic thin-film solar cells have been actively developed as next-generation solar cells. Organic thin-film solar cells usually have a configuration in which an active layer is sandwiched between a pair of electrodes. In order to improve the efficiency of transporting electrons from the active layer to the electrode, an electron extraction layer may be provided between the active layer and the electrode.

  Conventionally, metal oxides such as titanium oxide (TiOx) or zinc oxide (ZnO) have been used as a material for the electron extraction layer. For example, Non-Patent Documents 1, 2, and 3 describe using zinc oxide containing aluminum, zinc oxide containing gallium, and titanium oxide containing cesium as materials for the electron extraction layer, respectively. ing.

Sol. Energy Mater. Sol. Cells 2011, 95, 2194-2199. J. et al. Phys. Chem. C 2010, 114, 15782-1785. Adv. Funct. Mater. 2009, 19, 1241-1246.

  In order to put the organic photoelectric conversion element into practical use, it is required to further improve the photoelectric conversion efficiency. As described in Non-Patent Documents 1 and 2, the present inventors have disclosed an organic photoelectric conversion element having a zinc oxide layer containing an atom (aluminum or gallium) selected from Group 13 elements of the periodic table, and Non-Patent Document 3 Thus, the open circuit voltage and photoelectric conversion efficiency of the organic photoelectric conversion element having a titanium oxide layer containing cesium were considered to have room for improvement.

  An object of this invention is to provide the photoelectric conversion element, solar cell, and solar cell module which show higher photoelectric conversion efficiency.

  As a result of intensive studies in view of the above situation, the inventors of the present application are highly efficient by using an electron extraction layer containing an alkali metal element that is at least one selected from the group consisting of lithium, sodium, and potassium. It discovered that a photoelectric conversion element was obtained and came to this invention.

That is, the gist of the present invention is as follows.
[1] A pair of electrodes, an active layer between the electrodes, and an electron extraction layer between the active layer and one of the electrodes,
The electron extraction layer includes a mixed layer containing at least one alkali metal element selected from the group consisting of lithium, sodium, and potassium, and an oxide of a metal element different from the alkali metal element,
The total number of lithium atoms, sodium atoms, and potassium atoms in the mixed layer is 0.3% or more and 30% or less with respect to the number of atoms of the metal element.
[2] The photoelectric conversion element according to claim 1, wherein the oxide is zinc oxide or titanium oxide.
[3] A solar cell comprising the photoelectric conversion element according to claim 1 or 2.
[4] A solar cell module comprising the solar cell according to claim 3.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element, solar cell, and solar cell module which show higher photoelectric conversion efficiency can be provided.

It is sectional drawing which shows typically the structure of the photoelectric conversion element as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell module as one Embodiment of this invention.

  Embodiments of the present invention will be described in detail below, but the following descriptions are examples (representative examples) of the embodiments of the present invention and are not specified in these contents unless they exceed the gist of the present invention.

<1. Photoelectric conversion element>
The photoelectric conversion element according to the present invention includes a pair of electrodes, an active layer between the electrodes, and an electron extraction layer between the active layer and one of the electrodes. A photoelectric conversion element according to an embodiment of the present invention is shown in FIG. FIG. 1 shows a photoelectric conversion element used for a general organic thin film solar cell, but the photoelectric conversion element according to the present invention is not limited to the configuration of FIG.

  In the photoelectric conversion element 107, a base 106, an electrode (cathode) 101, a buffer layer (electron extraction layer) 102, an active layer 103, a buffer layer (hole extraction layer) 104, and an electrode (anode) 105 are sequentially formed. It has a layered structure. But the photoelectric conversion element which concerns on this invention does not need to have the hole extraction layer 104 and the base material 106. FIG. Further, the electrode (cathode) and the electrode (anode) may be disposed in reverse, and in this case, the electron extraction layer and the hole extraction layer are also disposed in reverse. Hereinafter, each of these parts will be described.

[1.1 Electron extraction layer (102)]
The electron extraction layer 102 has a function of transporting electrons from the active layer 103 to the electrode (cathode) 101. In order to improve the electron transport efficiency, the electron extraction layer 102 is usually in contact with the active layer 103. In addition, the electron extraction layer 102 is usually in contact with the electrode (cathode) 101. However, the electron extraction layer 102 may be in contact with the active layer 103 and the electrode (cathode) 101 through another layer. Furthermore, the electron extraction layer 102 may be composed of a plurality of layers.

  The electron extraction layer 102 includes a mixed layer containing an alkali metal element that is at least one selected from the group consisting of lithium, sodium, and potassium, and an oxide of a metal element that is different from the alkali metal element. Only one mixed layer may be used as the electron extraction layer 102. On the other hand, when the electron extraction layer 102 includes a plurality of layers, at least one of the plurality of layers is the mixed layer.

  The total number of lithium atoms, sodium atoms, and potassium atoms in the mixed layer is usually 0.3 atomic% or more, preferably 0.5 atomic%, more preferably with respect to the number of metal elements constituting the metal oxide. On the other hand, it is usually 30 atomic% or less, preferably 20 atomic% or less, more preferably 15% atom or less, and further preferably 10 atomic% or less. It is preferable that the composition ratio of the elements is in the above range in that the photoelectric conversion efficiency is improved and uniform film formation can be facilitated. When the composition ratio is in the above range, lithium, sodium and potassium are likely to be included in the porous (porous) structure of the metal oxide, which is considered to improve the photoelectric conversion efficiency. In particular, when the composition ratio is 0.3 atomic% or more, the dopant effect by the alkali metal element can be obtained better. On the other hand, when the composition ratio is 30 atomic% or less, a uniform film can be easily formed.

  The composition ratio of the lithium atom, sodium atom, potassium atom, and metal atom of the metal oxide in the mixed layer can be measured using XPS (X-ray photoelectron spectroscopy). Specifically, in the case where the active layer and the mixed layer are in contact with each other, when XPS measurement is performed, it is separated from the interface between the active layer and the mixed layer by 1/4 of the thickness of the mixed layer. The composition ratio of the part was examined. When the electron extraction layer is composed of a plurality of layers including a mixed layer, another layer constituting the electron extraction layer is formed between the active layer and the mixed layer, and the interface between the active layer and the mixed layer is formed. May not exist. In this case, among the other layers constituting the electron extraction layer formed between the mixed layer and the active layer, the thickness of the mixed layer is determined from the interface between the layer directly in contact with the mixed layer and the mixed layer. What is necessary is just to investigate the composition ratio of the part separated by 1/4. This method is preferable in that the composition can be measured in the vicinity of the interface with the active layer which is not easily affected by adjacent layers and has a large influence on the electron extraction performance.

  The thickness of the mixed layer is not particularly limited, but is usually 0.2 nm or more, preferably 0.5 nm or more, more preferably 1 nm or more, still more preferably 5 nm or more, and particularly preferably 10 nm or more. On the other hand, it is usually 1 μm or less, preferably 700 nm or less, more preferably 400 nm or less, and particularly preferably 200 nm or less. When the thickness of the mixed layer is 0.2 nm or more, the function as the electron extraction layer is satisfactorily exhibited, and when the thickness of the mixed layer is 1 μm or less, electrons are easily extracted and the photoelectric conversion efficiency is improved. To do.

  The total film thickness of the electron extraction layer 102 is not particularly limited, but is usually 0.2 nm or more, preferably 0.5 nm or more, more preferably 1 nm or more, still more preferably 5 nm or more, and particularly preferably 10 nm or more. On the other hand, it is usually 1 μm or less, preferably 700 nm or less, more preferably 400 nm or less, and particularly preferably 200 nm or less. When the thickness of the electron extraction layer 102 is 0.2 nm or more, the function as the electron extraction layer is satisfactorily exhibited, and when the thickness of the electron extraction layer 102 is 1 μm or less, electrons are easily extracted, Conversion efficiency is improved.

The electron mobility of the mixture layer is not particularly limited, but is usually 1.0 × 10 ⁻⁶ cm ² / Vs or more, preferably 1.0 × 10 ⁻⁵ cm ² / Vs or more, 5.0 × 10 ⁻⁵ cm ² / Vs or more is more preferable, and 1.0 × 10 ⁻⁴ cm ² / Vs or more is more preferable. On the other hand, it is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 5.0 × 10 ² cm ² / Vs or less. It is preferable that the electron mobility of the mixture layer is 1.0 × 10 ⁻⁶ cm ² / Vs or more from the viewpoint of improving the electron extraction performance and improving the conversion efficiency.

[1.1.1 Metal Element Oxides]
An oxide of a metal element (hereinafter referred to as a metal oxide) contained in the mixed layer is not particularly limited, but includes an oxide of a metal element different from an alkali metal element. Specific examples include metal oxides having n-type semiconductor characteristics such as zinc oxide, titanium oxide, aluminum oxide, silicon oxide, cerium oxide, lead oxide, zirconium oxide, or gallium oxide.

Examples of the metal oxide having n-type semiconductor characteristics include metal oxides whose electron mobility is within a predetermined range. The electron mobility of the metal oxide is not particularly limited, but is usually 1.0 × 10 ⁻⁶ cm ² / Vs or more, preferably 1.0 × 10 ⁻⁵ cm ² / Vs or more, 5.0 × 10 ⁻⁵ cm ² / Vs or more is more preferable, and 1.0 × 10 ⁻⁴ cm ² / Vs or more is more preferable. On the other hand, it is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 5.0 × 10 ² cm ² / Vs or less. It is preferable that the electron mobility of the metal oxide is 1.0 × 10 ⁻⁶ cm ² / Vs or more from the viewpoint that the electron extraction performance can be improved and the conversion efficiency can be improved.

  Among these, from the viewpoint of high electron extraction performance, an oxide of a periodic table group 4 element such as titanium oxide and an oxide of a periodic table group 12 element such as zinc oxide are preferable, and titanium oxide or zinc oxide is preferable. More preferred. Zinc oxide is particularly preferable in that it has a strong ionic bond and has a wurtzite type crystal structure, so that it easily coexists with a lithium compound, a sodium compound, and a potassium compound. In this specification, the periodic table refers to the IUPAC 2005 recommended version (Recommendations of IUPAC 2005).

  As the metal oxide, one kind of oxide may be used alone, or two or more kinds may be used in combination.

[1.1.2 Alkali metal elements]
Lithium, sodium, and potassium contained in the mixed layer may be present in the mixed layer in any form. The mixed layer as an example contains one or more compounds selected from the group consisting of a lithium compound, a sodium compound, and a potassium compound. There is no special restriction | limiting in the kind of compound, A compound includes carboxylate, such as an oxide, a hydroxide, a peroxide, carbonate, acetate, phosphate, nitrate, sulfate. Among these, an oxide is preferable because it can be obtained simultaneously with a metal oxide and is stable.

  One compound may be sufficient as the lithium compound, sodium compound, and potassium compound which are contained in a mixed layer, and a 2 or more types of mixture may be sufficient as it. For example, the sodium compound can be a mixture of sodium oxide, sodium hydroxide, sodium carbonate, sodium acetate, and the like. Such a mixture of sodium compounds can be obtained, for example, by performing a heat treatment using sodium acetate as a raw material.

[1.1.3 Formation Method of Electron Extraction Layer 102]
The method for forming the electron extraction layer 102 is not particularly limited. Specific examples include dry film formation methods such as vacuum deposition and sputtering, and wet film formation methods such as sol-gel methods and coating methods. In particular, when forming a mixed layer, it is preferable to use a sol-gel method or a coating method in terms of simplifying the process, and it is more preferable to use a coating method in terms of forming a film in a short time.

(Sol-gel method)
The sol-gel method refers to a method for producing a metal oxide by applying an external stimulus to the metal oxide precursor. Usually, a metal oxide precursor is converted into a metal oxide in a gel state through a sol-state metal hydroxide which is a hydrolyzate.

  When using the sol-gel method, an ink containing a metal oxide precursor, at least one alkali metal element selected from the group consisting of lithium, sodium, and potassium, and a solvent is prepared, and this ink is applied. Thus, an external stimulus is applied to convert the metal oxide precursor into a metal oxide (hereinafter referred to as a conversion step), thereby forming a mixed layer containing the metal oxide and the alkali metal element.

  The metal oxide precursor contained in the ink used in the sol-gel method is not particularly limited, but metal hydroxide, metal alkoxide such as metal ethoxide and metal isopropoxide, metal carboxylate such as metal acetate, Examples thereof include organic metal complexes such as metal acetylacetone salts and metal carbonyl salts, metal carbonates, metal phosphates, metal nitrates and metal sulfates. It is preferable that the metal oxide precursor can be easily converted into a metal oxide. In terms of easier conversion, the metal oxide precursor is preferably a metal hydroxide, metal alkoxide, metal carboxylate or metal carbonate, more preferably a metal carboxylate, and particularly preferably a metal carboxylate. Acid salt hydrate.

  The alkali metal element contained in the ink used in the sol-gel method can be in any form. The ink as an example contains an alkali metal compound that is at least one selected from the group consisting of a lithium compound, a sodium compound, and a potassium compound. There is no special restriction | limiting in the kind of compound, It may be the same as that illustrated about the mixed layer. In order to suppress the generation of by-products, it is preferable to use a metal salt or metal complex having the same form as the metal oxide precursor. For example, when the metal oxide precursor and the alkali metal compound are salts, the metal oxide precursor and the alkali metal compound preferably have a common counter anion. As an example, when forming a metal oxide using a metal carboxylate as a metal oxide precursor, the ink preferably contains the above-mentioned alkali metal carboxylate.

  As described above, the lithium compound, sodium compound and potassium compound contained in the mixed layer are preferably oxides (alkali metal oxides). In this case, the ink used for the sol-gel method may contain an alkali metal oxide or may contain an alkali metal oxide precursor. The precursor of an alkali metal oxide refers to a compound that is converted into an alkali metal oxide by a conversion step. Although it does not restrict | limit especially as a precursor of an oxide, For example, an alkali metal hydroxide, an alkali metal alkoxide, an alkali metal carbonate, an alkali metal nitrate, or an alkali metal carboxylate etc. are mentioned. It is more preferable to use an alkali metal carboxylate in that a mixed layer in which a metal oxide and an alkali metal element are uniformly mixed can be obtained more easily.

  The solvent used in the ink used in the sol-gel method is not particularly limited. For example, water; aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane or decane; toluene, xylene, chlorobenzene, or orthodichlorobenzene Aromatic hydrocarbons; alcohols such as methanol, ethanol, isopropanol, 2-methoxyethanol or 2-butoxyethanol; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; ethyl acetate, butyl acetate or methyl lactate Esters of: halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene; propylene glycol monomethyl ether acetate (PGMEA), ethyl ether , Ethers such as tetrahydrofuran or dioxane; amides such as dimethylformamide or dimethylacetamide; ethanol amines include amines such as diethylamine addition of triethylamine. Among these, water; alcohols such as methanol, ethanol, isopropanol, 2-methoxyethanol or 2-butoxyethanol; ethers such as propylene glycol monomethyl ether acetate (PGMEA), ethyl ether, tetrahydrofuran or dioxane. More preferred is water, ethanol, isopropanol, 2-methoxyethanol, 2-butoxyethanol or propylene glycol monomethyl ether acetate (PGMEA).

  The ink used for the sol-gel method may contain one type of solvent, or may contain two or more types of solvents in any combination and ratio. Moreover, the solvent may remain in the electron extraction layer, and there is no regulation on the boiling point of the solvent.

  The concentration of the metal oxide precursor in the ink used in the sol-gel method is not particularly limited, but is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more. On the other hand, it is usually 70% by mass or less, preferably 50% by mass or less, and more preferably 20% by mass or less. It is preferable that the concentration of the metal oxide precursor in the ink is within the above range in that the metal oxide precursor can be uniformly applied.

  The total concentration of the lithium compound, the sodium compound and the potassium compound in the ink used in the sol-gel method is not particularly limited, but is usually 0.003% by mass or more, preferably 0.005% by mass or more, more preferably 0.00. On the other hand, it is usually 25% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less. It is preferable that the concentration of the metal oxide and its precursor in the ink is in the above range from the viewpoint that the alkali metal compound or its precursor can be applied uniformly.

  The total number of lithium atoms, sodium atoms, and potassium atoms in the ink used for the sol-gel method is usually 0.3 atom% or more, preferably 0.5 atoms, relative to the number of metal elements constituting the metal oxide. % Or more, more preferably 1 atom% or more. On the other hand, it is usually 30 atom% or less, preferably 20 atom% or less, more preferably 15% atom or less, and further preferably 10 atom% or less. It is preferable that the composition ratio of the elements is in the above range in that the conversion efficiency of the obtained photoelectric conversion element can be improved. As a method for determining the composition ratio of lithium atoms, sodium atoms, potassium atoms, and metal atoms of the metal oxide in the ink, there is ICP (inductively coupled plasma) measurement. Since the sol-gel method is a film forming method that requires external stimulation as described below, the total number of lithium atoms, sodium atoms, and potassium atoms with respect to the number of atoms of the metal element constituting the metal oxide is: The ink and the element do not necessarily match.

  The ink can be applied by any method. Examples thereof include spin coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor method, impregnation / coating method, curtain coating method and the like. Moreover, 1 type may be used independently among these methods, and 2 or more types can also be used in arbitrary combinations.

  In the conversion step, what kind of external stimulus is given to the metal oxide precursor is arbitrary, but usually heat treatment, light treatment, etc. are performed. It is preferable to perform heat treatment in that the drying process can be performed simultaneously.

  Other specific treatments in the sol-gel method can be performed with reference to known techniques. For example, it is also preferable to add an amine such as ethanolamine to the ink in that the ink can be stabilized.

(Coating method)
The coating method refers to a method of forming a layer containing a compound by applying an ink containing the compound. For example, a metal oxide and an alkali metal element are contained by applying a coating liquid containing a metal oxide and at least one alkali metal element selected from the group consisting of lithium, sodium, and potassium. Layer can be formed.

  The ink used for the coating method is not particularly limited as long as it contains a metal oxide, an alkali metal element, and a solvent.

  The metal oxide contained in the ink used in the coating method is preferably in the form of particles in that an electron extraction layer having a uniform thickness can be formed.

  The average primary particle size of the metal oxide particles is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, and is usually 100 nm or less, preferably 60 nm or less, more preferably 40 nm or less. The average primary particle size of 5 nm or more is preferable because the metal oxide is less likely to aggregate and a metal oxide having a suitable average secondary particle size can be obtained. Moreover, it is preferable that the average primary particle diameter is 100 nm or less because each of the secondary particles of the metal oxide has an appropriate size and an electron extraction layer having a uniform film thickness is formed.

  The average primary particle size of the metal oxide can be measured with a dynamic light scattering particle size measuring device, a transmission electron microscope (TEM), or the like. Specific examples of metal oxides having an average primary particle size of 5 nm or more and 100 nm or less (sometimes referred to as metal oxide nanoparticles) include nano zinc 60 (Honjo Chemical Co., Ltd.), FINEX-30 (Sakai Chemical Industry). And ZINCOX SUPER F-2 (manufactured by Hakusui Tech Co., Ltd.).

  In addition, the metal oxide particles may be surface-treated with a surface treatment agent to facilitate dispersion in a solvent. The surface treatment agent is not particularly limited, but is a polysiloxane compound such as methylhydrogenpolysiloxane, polymethoxysilane, dimethylpolysiloxane, or dimethicone PEG-7 succinate and a salt thereof; a silane compound or the like (methyldimethoxysilane) , Dimethyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, 3-aminopropyltriethoxysilane or 3-carboxypropyltrimethyltrimethoxysilane); organosilicon compounds; lauric acid, stearic acid, 2- (2-methoxy) Ethoxy) Carboxylic acid compounds such as acetic acid or 6-hydroxyhexanoic acid; Organophosphorus compounds such as lauryl ether phosphoric acid or trioctylphosphine; Dimethylamine, tributylamine, trimethylamine, cyclohexylamino Or amine compounds such as ethylenediamine; polyimines, polyesters, polyamides, binder resin such as polyurethane or polyurea. In addition, as a surface treating agent, 1 type of compounds may be used independently, or 2 or more types may be used together.

  The alkali metal element contained in the ink used for the coating method can be in any form. The ink as an example contains an alkali metal compound that is at least one selected from the group consisting of a lithium compound, a sodium compound, and a potassium compound. There is no special restriction | limiting in the kind of compound, It may be the same as that illustrated about the mixed layer. Moreover, as a lithium compound, a sodium compound, and a potassium compound which a mixed layer contains as mentioned above, an oxide (alkali metal oxide) is preferable. In this case, the ink used for the coating method may contain an alkali metal oxide or a precursor of an alkali metal oxide. As the precursor of the alkali metal oxide, the same ones as mentioned for the sol-gel method can be used.

  The solvent contained in the ink used for the coating method is not particularly limited, and the same solvents as those mentioned for the sol-gel method can be used.

  The concentration of the metal oxide in the ink used for the coating method is not particularly limited, but is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more. Usually, it is 70 mass% or less, preferably 50 mass% or less, more preferably 20 mass% or less. It is preferable that the concentration of the metal oxide in the ink is within the above range from the viewpoint that the metal oxide can be uniformly applied.

  The total concentration of the lithium compound, sodium compound, and potassium compound in the ink used for the coating method is not particularly limited, and can be the same as that of the ink used for the sol-gel method. Further, the ratio of the total number of lithium atoms, sodium atoms and potassium atoms in the ink used for the coating method to the number of atoms of the metal element constituting the metal oxide can be the same as that of the ink used for the sol-gel method.

  The ink can be applied by any method. Specific examples are the same as those mentioned for the sol-gel method.

[1.1.4 Action of electron extraction layer]
The electron extraction layer 102 includes a mixed layer containing an alkali metal element that is at least one selected from the group consisting of lithium, sodium, and potassium, and an oxide of a metal element that is different from the alkali metal element.

  Generally, in an electronic device, an alkali-free glass that does not contain alkali metal elements such as sodium and potassium, which cause a decrease in durability and an increase in leakage current, is used. However, according to the study by the present inventors, the metal oxide contains at least one alkali metal element selected from the group consisting of lithium, sodium, or potassium, so that the conversion efficiency in the photoelectric conversion element is improved. found. The reason for this is that lithium, sodium and potassium have electronegativity lower than that of zinc, so in the mixed layer, lithium, sodium or potassium atoms are well dispersed in the metal oxide, and the mixed layer has higher electron extraction performance. Is considered to have been obtained.

  On the other hand, as described above, a technique is known in which a zinc oxide layer containing an atom (particularly aluminum or gallium) selected from Group 13 elements of the periodic table is used as an electron extraction layer. However, it is not easy to well disperse atoms (particularly aluminum or gallium) selected from Group 13 elements of the periodic table in a metal oxide such as zinc oxide. That is, the group 13 element of the periodic table has an electronegativity close to that of the metal element constituting the metal oxide, so that atoms selected from the group 13 element of the periodic table are dispersed in the metal oxide such as zinc oxide. This is because it is considered necessary to substitute a metal atom with an atom selected from Group 13 elements of the periodic table.

  Cesium also has a smaller electronegativity than zinc, but has a larger atomic radius than lithium, sodium and potassium. For this reason, it is considered that cesium hardly enters the metal oxide. For this reason, it is considered that the metal oxide containing cesium shows lower electron extraction performance than the metal oxide containing lithium, sodium or potassium.

  In addition, when a metal such as aluminum or cesium is added, it is difficult to handle a metal salt or metal complex, and it is difficult to use a salt or complex having the same form as the metal oxide precursor. For example, when zinc acetate is used as the metal oxide precursor, examples of the salt in the same form include cesium acetate and aluminum acetate hydroxide, which are more stable and less soluble than potassium acetate and sodium acetate. There are challenges. Cesium carbonate is often used as the cesium compound, and aluminum nitrate is often used as the aluminum compound. However, zinc carbonate and zinc nitrate, which are salts in the same form as these, are unstable and difficult to handle. In this case, different forms of salts can be used, such as carbonate and acetate, nitrate and acetate, but the complexity increases in terms of decomposition temperature and by-products generated, so for example only acetate is used. There is a possibility that problems in terms of ease of handling, control of film quality to be generated, and costs related to these may be greater than in the case of using them. On the other hand, since lithium, sodium, and potassium salts or complexes have a wide variety of stable compounds, it is easy to use a salt or complex in the same form as the metal oxide precursor, which is advantageous in terms of cost. is there.

In particular, when zinc oxide is used as the metal oxide, 3d electrons of Zn (1s ² 2s ² 2s ⁶ 3s ² 3s ⁶ 3d ¹⁰ 4s ² ) and 2p electrons of O (1s ² 2s ² 2p ⁴ ) and Are strongly hybridized, Li (1s ² 2s ¹ ), Na (1s ² 2s ² 2p ⁶ 3s ¹ ), K (1s ² 2s ² 2p ⁶ 3s ² 3p ⁶ 4s ¹ ) which do not have 3d electrons are Zn Modify the -O bond and induce local dipoles. Thus, it is considered that the zinc oxide film containing lithium, sodium or potassium shows higher electron extraction performance.

[1.2 Hole Extraction Layer (104)]
The material of the hole extraction layer 104 is not particularly limited as long as it is a material that can improve the efficiency of extracting holes from the active layer 103 to the electrode (anode) 105. Specifically, conductive organic compounds such as polythiophene, polypyrrole, polyacetylene, triphenylenediamine polypyrrole or polyaniline doped with sulfonic acid and / or iodine, polythiophene derivatives having a sulfonyl group as a substituent, and conductive organic compounds such as arylamine And metal oxides such as copper oxide, nickel oxide, manganese oxide, molybdenum oxide, vanadium oxide, and tungsten oxide, and p-type semiconductor compounds described later. Among them, a conductive polymer doped with sulfonic acid is preferable, and more preferably, poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: polythiophene derivative doped with polystyrene sulfonic acid). PSS). A thin film of metal such as gold, indium, silver or palladium can also be used. Further, a thin film of metal or the like can be used alone or in combination with the above organic material.

  In addition, the hole extraction layer 104 may be formed of a single layer or may have a stacked structure of two or more layers.

  The thickness of the hole extraction layer 104 is not particularly limited, but is usually 0.2 nm or more. On the other hand, it is usually 400 nm or less, preferably 200 nm or less. When the film thickness of the hole extraction layer 104 is 0.2 nm or more, the function as a buffer material is well exhibited, and when the film thickness of the hole extraction layer 104 is 400 nm or less, holes are easily extracted. Photoelectric conversion efficiency can be improved.

  There is no limitation on the formation method of the hole extraction layer 104. For example, when a material having sublimation property is used, it can be formed by a dry film forming method such as a vacuum evaporation method. For example, when a material soluble in a solvent is used, the film can be formed by a wet film forming method using a method such as a spin coating method or an ink jet method. In the case of using a semiconductor compound for the hole extraction layer 104, by forming a layer containing a precursor in the same manner as a low molecular organic semiconductor compound used for an active layer described later, the precursor is converted into a semiconductor compound, The hole extraction layer 104 containing a semiconductor compound can be formed.

In particular, when PEDOT: PSS is used, it is preferable to form the hole extraction layer 104 by applying a dispersion. PEDOT: The dispersion of PSS, and CLEVIOS ^TM series of Heraeus, Inc., include Agfa Corp. of ORGACON ^TM series and the like.

  When the wet film forming method is used, the coating solution may further contain a surfactant. By using the surfactant, it is possible to suppress the occurrence of at least one of minute bubbles, dents due to adhesion of foreign substances, and uneven coating in the drying process.

  Known surfactants (cationic surfactants, anionic surfactants, nonionic surfactants) can be used as the surfactant. Of these, silicon-based surfactants, acetylenic diol-based surfactants, and fluorine-based surfactants are preferable. One type of surfactant may be used alone, or two or more types of surfactants may be used in any combination and ratio.

[1.3 Active layer (103)]
The active layer 103 refers to a layer in which photoelectric conversion is performed, and usually includes a p-type semiconductor compound and an n-type semiconductor compound. A p-type semiconductor compound refers to a compound that functions as a p-type semiconductor material, and an n-type semiconductor compound refers to a compound that functions as an n-type semiconductor material. When the photoelectric conversion element 107 receives light, the light is absorbed by the active layer 103 and electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is supplied to the electrode (cathode) 101 and the electrode (anode). ) 105.

  As the material of the active layer 103, either an inorganic compound or an organic compound may be used. It is preferable that the active layer 103 can be formed by a simple coating process. From this viewpoint, it is preferable to use an organic compound as the material of the active layer 103. In this case, the active layer 103 is an organic active layer containing an organic compound. In the following description, it is assumed that the active layer 103 is an organic active layer.

  The layer structure of the active layer 103 is a thin film stacked type in which a p-type semiconductor compound layer and an n-type semiconductor compound layer are stacked, a bulk heterojunction type having a mixed layer of a p-type semiconductor compound and an n-type semiconductor compound, and a p-type semiconductor. Examples thereof include a structure having a layer (i layer) in which a compound and an n-type semiconductor compound are mixed as an intermediate layer of a thin film stack type. Among these, a bulk heterojunction active layer having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed is preferable.

  The thickness of the active layer 103 is not particularly limited, but is usually 10 nm or more, preferably 50 nm or more, and is usually 1000 nm or less, preferably 500 nm or less, more preferably 200 nm or less. The film thickness of the active layer 103 is preferably 10 nm or more because the uniformity of the film is maintained and a short circuit is less likely to occur. Further, it is preferable that the thickness of the active layer 103 is 1000 nm or less because the internal resistance is reduced and the distance between the electrodes is not increased, and the charge diffusion is improved.

  The method for forming the active layer 103 is not particularly limited, and for example, a wet film formation method or a dry film formation method can be used. Especially, it is preferable to use the wet film-forming method which forms a layer by apply | coating the coating liquid containing a semiconductor compound. More specifically, the p-type semiconductor compound layer can be formed by applying a coating solution containing a p-type semiconductor compound, and the n-type semiconductor compound layer is applied with a coating solution containing an n-type semiconductor compound. The layer in which the p-type semiconductor compound and the n-type semiconductor compound are mixed can be formed by applying a coating solution containing the p-type semiconductor compound and the n-type semiconductor compound.

  Moreover, after apply | coating the coating liquid containing a p-type semiconductor compound precursor, you may convert a p-type semiconductor compound precursor into a p-type semiconductor compound, or after apply | coating the coating liquid containing an n-type semiconductor compound precursor. The n-type semiconductor compound precursor may be converted into an n-type semiconductor compound. Here, the semiconductor compound precursor refers to a compound that is converted into a semiconductor compound by applying an external stimulus such as heat or light.

  The specific wet film forming method is arbitrary, for example, spin coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe Examples include a doctor method, an impregnation / coating method, and a curtain coating method.

  As the p-type semiconductor compound and the n-type semiconductor compound, one type of compound may be used, or two or more types of compounds may be used in combination at an arbitrary ratio.

[1.3.1 p-type semiconductor compound]
The p-type semiconductor compound contained in the active layer 103 is not particularly limited, and examples thereof include a low molecular organic semiconductor compound and a high molecular organic semiconductor compound.

[1.3.1.1 Low Molecular Organic Semiconductor Compound]
The molecular weight of the low-molecular organic semiconductor compound is not particularly limited both at the upper limit and the lower limit, but is usually 5000 or less, preferably 2000 or less, and is usually 100 or more, preferably 200 or more.

  Further, the low molecular organic semiconductor compound preferably has crystallinity. The p-type semiconductor compound having crystallinity has a strong intermolecular interaction, and efficiently generates holes generated at the interface of the mixture layer of the p-type semiconductor compound and the n-type semiconductor compound in the active layer 103 as an electrode (anode). This is because it can be expected to be transported to 105.

In the present specification, crystallinity refers to the property of a compound that takes a three-dimensional periodic array with uniform orientation due to intermolecular interaction or the like. Examples of the method for measuring crystallinity include X-ray diffraction (XRD) or field effect mobility measurement. In particular, in the field effect mobility measurement, a crystalline compound having a hole mobility of 1.0 × 10 ⁻⁵ cm ² / Vs or more is preferable, and a crystalline compound having 1.0 × 10 ⁻⁴ cm ² / Vs or more is preferable. Is more preferable. On the other hand, a crystalline compound having a hole mobility of usually 1.0 × 10 ⁴ cm ² / Vs or less is preferable, and a crystalline compound having 1.0 × 10 ³ cm ² / Vs or less is more preferable. A crystalline compound having a size of 10 ² cm ² / Vs or less is more preferable.

  The low-molecular organic semiconductor compound is not particularly limited as long as it satisfies the above-mentioned performance. Specifically, the condensed low-molecular organic hydrocarbon such as naphthacene, pentacene or pyrene; and four thiophene rings such as α-sexithiophene. Oligothiophenes containing above: those containing at least one of thiophene ring, benzene ring, fluorene ring, naphthalene ring, anthracene ring, thiazole ring, thiadiazole ring and benzothiazole ring, and a total of four or more linked; phthalocyanine compound And a metal complex thereof, or a porphyrin compound such as tetrabenzoporphyrin and a macrocycle compound thereof such as a metal complex thereof. Preferably, they are a phthalocyanine compound and its metal complex, or a porphyrin compound and its metal complex.

Examples of the porphyrin compound and its metal complex (Z ¹ in the following formula is CH), the phthalocyanine compound and its metal complex (Z ¹ in the following formula is N) used as the p-type semiconductor compound include the following structures: The compound of this is mentioned.

Here, M represents a metal or two hydrogen atoms. As the metal, in addition to a divalent metal such as Cu, Zn, Pb, Mg, Co or Ni, a trivalent or higher metal having an axial ligand. For example, TiO, VO, SnCl ₂ , AlCl, InCl, Si (OH) _2, or the like can be given.

R ^{11 to} R ¹⁴ are each independently a hydrogen atom or an alkyl group having 1 to 24 carbon atoms. The alkyl group having 1 to 24 carbon atoms is a saturated or unsaturated chain hydrocarbon group having 1 to 24 carbon atoms or a saturated or unsaturated cyclic hydrocarbon having 3 to 24 carbon atoms. . Among these, a saturated or unsaturated chain hydrocarbon group having 1 to 12 carbon atoms or a saturated or unsaturated cyclic hydrocarbon group having 3 to 12 carbon atoms is preferable.

  Among the phthalocyanine compounds and metal complexes thereof, 29H, 31H-phthalocyanine, copper phthalocyanine complex, zinc phthalocyanine complex, titanium phthalocyanine oxide complex, magnesium phthalocyanine complex, lead phthalocyanine complex or copper 4,4 ′, 4 ″, 4 '' '-Tetraaza-29H, 31H-phthalocyanine complex, more preferably 29H, 31H-phthalocyanine or copper phthalocyanine complex.

  Among the porphyrin compounds and metal complexes thereof, 5,10,15,20-tetraphenyl-21H, 23H-porphine, 5,10,15,20-tetraphenyl-21H, 23H-porphine cobalt (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine zinc (II), 5,10,15,20- Tetraphenyl-21H, 23H-porphine nickel (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide, 5,10,15,20-tetra (4-pyridyl)- 21H, 23H-porphine, 29H, 31H-tetrabenzo [b, g, l, q] porphine, 2 H, 31H-tetrabenzo [b, g, l, q] porphine cobalt (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine copper (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine zinc (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine nickel (II) or 29H, 31H-tetrabenzo [b, g, l, q] porphine vanadium (IV) oxide And preferably 5,10,15,20-tetraphenyl-21H, 23H-porphine or 29H, 31H-tetrabenzo [b, g, l, q] porphine.

  As described above, the layer containing a low molecular weight semiconductor compound is preferably formed by a wet film formation method. In particular, it is possible to form a layer containing a low molecular weight semiconductor compound by applying a coating liquid containing a low molecular weight semiconductor compound precursor and then converting the low molecular weight semiconductor compound precursor into a low molecular weight semiconductor compound. It is preferable in that the film is easy. Although there is no restriction | limiting in particular as a specific method, The method as described in Unexamined-Japanese-Patent No. 2007-324587 and Unexamined-Japanese-Patent No. 2011-119648 is mentioned.

[1.3.1.2 Polymer Organic Semiconductor Compound]
The polymer organic semiconductor compound is not particularly limited, and is a conjugated polymer semiconductor such as polythiophene, polyfluorene, polyphenylene vinylene, polythienylene vinylene, polyacetylene, or polyaniline; a polymer such as oligothiophene substituted with an alkyl group or other substituent Semiconductor; and the like. Moreover, the semiconductor polymer which copolymerized 2 or more types of monomer units is also mentioned. The conjugated polymers, ^{e.g., Handbook of Conducting Polymers, 3 rd} Ed. (2 volumes, 2007), Materials Science and Engineering, 2001, 32, 1-40, Pure Appl. Chem. 2002, 74, 2031-3044, Handbook of THIOPHENE-BASED MATERIALS (2 volumes, 2009) and other polymers described in the literature, derivatives thereof, and polymers that can be synthesized by combinations of the described monomers may be used. it can.

  Polymer monomer backbone and monomer substituents are selected to control solubility, crystallinity, film-formability, HOMO (highest occupied molecular orbital) energy level, LUMO (lowest unoccupied molecular orbital) energy level, etc. can do. In addition, it is preferable that the polymer organic semiconductor compound is soluble in an organic solvent in that a layer containing the polymer organic semiconductor compound can be formed by a wet film forming method. Specific examples of the polymer organic semiconductor compound include the following, but are not limited to the following.

  Among them, the p-type semiconductor compound is preferably a low molecular organic semiconductor compound such as condensed aromatic hydrocarbons such as naphthacene, pentacene, and pyrene, phthalocyanine compounds and metal complexes thereof, or porphyrin compounds such as tetrabenzoporphyrin (BP) and The metal complex and the polymer organic semiconductor compound is a conjugated polymer semiconductor such as polythiophene.

  At least one of the low-molecular organic semiconductor compound and the high-molecular organic semiconductor compound may have some self-organized structure in a film-formed state, or may be in an amorphous state.

  The HOMO energy level of the p-type semiconductor compound is not particularly limited, but can be selected depending on the type of the n-type semiconductor compound described later. In particular, when the fullerene compound is used as the n-type semiconductor compound, The HOMO energy level is usually −5.7 eV or more, more preferably −5.5 eV or more, and usually −4.6 eV or less, more preferably −4.8 eV or less. When the HOMO energy level of the p-type semiconductor compound is −5.7 eV or more, the characteristics as the p-type semiconductor are improved, and when the HOMO energy level of the p-type semiconductor is −4.6 eV or less, the p-type semiconductor is improved. The stability of the compound is improved, and the open circuit voltage (Voc) can be improved.

  The LUMO energy level of the p-type semiconductor compound is not particularly limited, but can be selected according to the type of the n-type semiconductor compound described later. In particular, when a fullerene compound is used as an n-type semiconductor compound, the LUMO energy level of the p-type semiconductor compound is usually −3.7 eV or more, preferably −3.6 eV or more, while usually −2.5 eV or less, preferably Is −2.7 eV or less. When the LUMO energy level of the p-type semiconductor compound is −2.5 eV or less, the band gap can be adjusted to effectively absorb long-wavelength light energy, and the short-circuit current density (Jsc) can be improved. . When the LUMO energy level of the p-type semiconductor compound is −3.7 eV or more, electron transfer to the n-type semiconductor compound is likely to occur, and the short-circuit current density (Jsc) can be improved.

  As a calculation method of the HOMO energy level and the LUMO energy level, there are a theoretically calculated method and a method of actually measuring. Theoretically calculated methods include semi-empirical molecular orbital methods and non-empirical molecular orbital methods. Examples of the actual measurement method include ultraviolet-visible absorption spectrum measurement method and cyclic voltammogram measurement method. Among them, the cyclic voltammogram measurement method is preferable. In this specification, the HOMO energy level and the LUMO energy level refer to values with respect to a vacuum level calculated by a cyclic voltammogram measurement method.

[1.3.2 n-type semiconductor compound]
The n-type semiconductor compound is not particularly limited. Specifically, the fullerene compound; a quinolinol derivative metal complex represented by 8-hydroxyquinoline aluminum; a condensed ring such as naphthalenetetracarboxylic acid diimide or perylenetetracarboxylic acid diimide Tetracarboxylic acid diimides; perylene diimide derivatives, terpyridine metal complexes, tropolone metal complexes, flavonol metal complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazoles Derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives Bipyridine derivatives, borane derivatives, anthracene, pyrene, total fluoride condensed polycyclic aromatic hydrocarbons such as naphthacene or pentacene; single-walled carbon nanotubes, and the like.

  Among them, fullerene compounds, borane derivatives, thiazole derivatives, benzothiazole derivatives, benzothiadiazole derivatives, N-alkyl-substituted naphthalenetetracarboxylic acid diimides or N-alkyl-substituted perylene diimide derivatives are preferable, fullerene compounds, N-alkyl More preferred are substituted perylene diimide derivatives or N-alkyl substituted naphthalene tetracarboxylic acid diimides.

  Examples of the n-type semiconductor compound include an n-type polymer semiconductor compound. Specifically, although there is no particular limitation, condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid diimide, perylene diimide derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzothiazoles Derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, bipyridine derivatives, and borane derivatives include n-type polymer semiconductor compounds. . Among them, polymers having at least one of borane derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, N-alkyl-substituted naphthalenetetracarboxylic acid diimides and N-alkyl-substituted perylene diimide derivatives as constituent units Preferably, an n-type polymer semiconductor compound comprising at least one of the n-type polymer semiconductor compound comprising N-alkyl-substituted perylene diimide derivative and N-alkyl-substituted naphthalenetetracarboxylic acid diimide as a constituent unit Is more preferable.

  The LUMO energy level of the n-type semiconductor compound is not particularly limited, but is usually −3.85 eV or more, preferably −3.80 eV or more. In order to efficiently move electrons from a p-type semiconductor to an n-type semiconductor, the relative relationship of LUMO energy levels between the p-type semiconductor compound and the n-type semiconductor compound is important. Specifically, the LUMO energy level of the p-type semiconductor compound is higher than the LUMO energy level of the n-type semiconductor compound by a predetermined energy, in other words, the electron affinity of the n-type semiconductor compound is p-type semiconductor compound. It is preferable that a predetermined energy is larger than the electron affinity. Since the open-circuit voltage (Voc) depends on the difference between the HOMO energy level of the p-type semiconductor compound and the LUMO energy level of the n-type semiconductor compound, increasing the LUMO energy level of the n-type semiconductor compound increases the open-circuit voltage (Voc). ) Tends to be high.

  On the other hand, the LUMO energy level of the n-type semiconductor compound is usually −1.0 eV or less, preferably −2.0 eV or less, more preferably −3.0 eV or less, and further preferably −3.3 eV or less. By lowering the LUMO energy level of the n-type semiconductor compound, electron transfer tends to occur and the short circuit current (Jsc) tends to increase.

  The HOMO energy level of the n-type semiconductor compound is not particularly limited, but is usually −5.0 eV or less, preferably −5.5 eV or less. On the other hand, it is usually −7.0 eV or more, preferably −6.6 eV or more. It is preferable that the HOMO energy level of the n-type semiconductor compound is −7.0 eV or more because light absorption by the n-type semiconductor compound can also be used for power generation. It is preferable that the HOMO energy level of the n-type semiconductor compound is −5.0 eV or less from the viewpoint of preventing reverse movement of holes.

The electron mobility of the n-type semiconductor compound is not particularly limited, but is usually 1.0 × 10 ⁻⁶ cm ² / Vs or more, preferably 1.0 × 10 ⁻⁵ cm ² / Vs or more. 0 × 10 ⁻⁵ cm ² / Vs or more is more preferable, and 1.0 × 10 ⁻⁴ cm ² / Vs or more is more preferable. On the other hand, it is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 1.0 × 10 ² cm ² / Vs or less. When the electron mobility of the n-type semiconductor compound is 1.0 × 10 ⁻⁶ cm ² / Vs or more, effects such as improvement of the electron diffusion rate, improvement of short circuit current, improvement of conversion efficiency of the photoelectric conversion element tend to increase. Because there is a certain tendency, it is preferable.

  As a method for measuring electron mobility, field effect transistor (FET) measurement can be mentioned, and specifically, it can be carried out by a method described in known literature (Japanese Patent Application Laid-Open No. 2010-045186).

  The solubility of the n-type semiconductor compound in toluene at 25 ° C. is usually 0.5% by mass or more, preferably 0.6% by mass or more, and more preferably 0.7% by mass or more. On the other hand, 90 mass% or less is preferable normally, 80 mass% or less is more preferable, and 70 mass% or less is further more preferable. When the solubility of the n-type semiconductor compound is 0.5% by mass or more, the dispersion stability of the n-type semiconductor material is improved in a solution containing the n-type semiconductor compound, and aggregation, sedimentation, separation, and the like are less likely to occur. Therefore, it is preferable in that film formation by a wet film formation method is easy.

  Hereinafter, these preferable n-type semiconductor compounds will be further described.

[1.3.2.1 Fullerene Compound]
As a fullerene compound, what has the partial structure represented by general formula (n1), (n2), (n3) and (n4) is preferable.

In formulas (n1) to (n4), FLN represents fullerene which is a carbon cluster having a closed shell structure. The carbon number of fullerene is not particularly limited as long as it is usually an even number of 60 to 130. Examples of fullerenes include C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , C ₉₆ and higher carbon clusters having more carbon than these. . Among these, _C60 or _C70 is preferable. As fullerenes, carbon-carbon bonds on some fullerene rings may be broken. Some carbon atoms may be replaced with other atoms. Furthermore, a metal atom, a non-metal atom, or an atomic group composed of these may be included in the fullerene cage.

a, b, c and d are integers, and the sum of a, b, c and d is usually 1 or more, and usually 5 or less, preferably 3 or less. The partial structures represented by (n1), (n2), (n3) and (n4) are added to the same 5-membered ring or 6-membered ring in the fullerene skeleton. In the general formula (n1), —R ²¹ and — (CH ₂ ) _L are added to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. In the general formula (n2), -C (R ²⁵ ) (R ²⁶ ) -N (R ²⁷ ) -C with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. (R ²⁸ ) (R ²⁹ ) — are added to form a 5-membered ring. In the general formula (n3), —C (R ³⁰ ) (R ³¹ ) —C—C—C (R) with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. ³² ) (R ³³ ) — are added to form a 6-membered ring. In the general formula (n4), —C (R ³⁴ ) (R ³⁵ ) — is added to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton to form a 3-membered ring. Forming. L is an integer of 1 to 8. L is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.

In the general formula (n1), R ²¹ is an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkoxy group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group which may have a group.

  The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group or an isobutyl group, and further preferably a methyl group or an ethyl group.

  As an alkoxy group, a C1-C10 thing is preferable, a C1-C6 thing is more preferable, and a methoxy group or an ethoxy group is especially preferable.

  The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. A group or a thienyl group is more preferred.

  As the substituent that the alkyl group, alkoxy group and aromatic group may have, a halogen atom or a silyl group is preferable. As the halogen atom, a fluorine atom is preferable. The silyl group is preferably a diarylalkylsilyl group, a dialkylarylsilyl group, a triarylsilyl group or a trialkylsilyl group, more preferably a dialkylarylsilyl group, and even more preferably a dimethylarylsilyl group.

In the general formula (n1), R ^{22 to} R ²⁴ each independently represent a substituent, which has a hydrogen atom, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group that may be used.

  As an alkyl group, a C1-C10 thing is preferable and a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, or n-hexyl group is preferable. The substituent that the alkyl group may have is preferably a halogen atom. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. A group or a thienyl group is more preferred. Examples of the substituent that the aromatic group may have include a fluorine atom, an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, an alkoxy group having 1 to 14 carbon atoms, or An aromatic group having 2 to 10 carbon atoms is preferred, a fluorine atom or an alkoxy group having 1 to 14 carbon atoms is more preferred, and a methoxy group, n-butoxy group or 2-ethylhexyloxy group is further preferred. When the aromatic group has a substituent, the number is not limited, but is preferably 1 or more and 3 or less, and more preferably 1. When the aromatic group has a plurality of substituents, the types of the substituents may be different, but are preferably the same.

In the general formula (n2), R ^{25 to} R ²⁹ are each independently a hydrogen atom, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or an aromatic group optionally having a substituent. It is a group.

  The alkyl group is preferably a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, n-hexyl group or octyl group, and more preferably a methyl group. The substituent that the alkyl group may have is preferably a halogen atom. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, a phenyl group or a pyridyl group is more preferable, and a phenyl group is further preferable. The substituent that the aromatic group may have is not particularly limited, but is preferably a fluorine atom, an alkyl group having 1 to 14 carbon atoms, or an alkoxy group having 1 to 14 carbon atoms. The alkyl group may be substituted with a fluorine atom. More preferably, it is an alkoxy group having 1 to 14 carbon atoms, and more preferably a methoxy group. When it has a substituent, there is no limitation in the number, However, Preferably it is 1-3, More preferably, it is 1. The types of substituents may be different, but are preferably the same.

In the general formula (n3), Ar ¹ is an optionally substituted aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, preferably A phenyl group, a naphthyl group, a biphenyl group, a thienyl group, a furyl group, a pyridyl group, a pyrimidyl group, a quinolyl group or a quinoxalyl group, more preferably a phenyl group, a thienyl group or a furyl group.

  Although there is no limitation in particular as a substituent which you may have, a fluorine atom, a chlorine atom, a hydroxyl group, a cyano group, a silyl group, a boryl group, the amino group which may be substituted by the alkyl group, C1-C14 or less An alkyl group having 1 to 14 carbon atoms, an alkylcarbonyl group having 1 to 14 carbon atoms, an alkylthio group having 1 to 14 carbon atoms, an alkenyl group having 2 to 14 carbon atoms, and 2 to 14 carbon atoms. The following alkynyl groups, ester groups having 2 to 14 carbon atoms, arylcarbonyl groups having 3 to 20 carbon atoms, arylthio groups having 2 to 20 carbon atoms, aryloxy groups having 2 to 20 carbon atoms, 6 carbon atoms An aromatic hydrocarbon group having 20 to 20 carbon atoms or a heterocyclic group having 2 to 20 carbon atoms is preferable, a fluorine atom, an alkyl group having 1 to 14 carbon atoms, and 1 carbon atom. Above 14 an alkoxy group, having 2 to 14 ester groups carbons, an alkyl group or having 3 to 20 arylcarbonyl group carbons of 2 to 14 carbon atoms and more preferable. The alkyl group having 1 to 14 carbon atoms may be substituted with one or more fluorine atoms. When it has a substituent, although there is no limitation in the number, 1-4 are preferable and 1-3 are more preferable. When there are a plurality of substituents, the types may be different, but are preferably the same.

  The alkyl group having 1 to 14 carbon atoms is preferably a methyl group, an ethyl group or a propyl group. The alkoxy group having 1 to 14 carbon atoms is preferably a methoxy group, an ethoxy group, or a propoxyl group. The alkylcarbonyl group having 1 to 14 carbon atoms is preferably an acetyl group. The ester group having 2 to 14 carbon atoms is preferably a methyl ester group or an n-butyl ester group. The arylcarbonyl group having 3 to 20 carbon atoms is preferably a benzoyl group.

In General Formula (n3), R ^{30 to} R ³³ each independently have a hydrogen atom, an alkyl group that may have a substituent, an amino group that may have a substituent, or a substituent. It is an optionally substituted alkoxy group or an optionally substituted alkylthio group. R ³⁰ or R ³¹ may be bonded to R ³² or R ³³ to form a ring. As an example of the case where R ³⁰ or R ³¹ is bonded to R ³² or R ³³ to form a ring, a structure of the general formula (n5) which is a bicyclo structure in which an aromatic group is condensed can be given.

F In the general formula (n5) is the same integer and c, Z ² represents an oxygen atom, a sulfur atom, an amino group, an alkylene group or an arylene group.

  As an alkylene group, a C1-C2 thing is preferable, and a methylene group or an ethylene unit is mentioned. As the arylene group, those having 5 to 12 carbon atoms are preferable, and examples thereof include a phenylene group. The amino group may be substituted with an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group. The alkylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted. The arylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted.

  The structure represented by the formula (n5) is particularly preferably a structure represented by the following formula (n6) or the formula (n7).

In General Formula (n4), R ^{34 to} R ³⁵ each independently have a hydrogen atom, an alkoxycarbonyl group, an alkyl group having 1 to 14 carbon atoms that may have a substituent, or a substituent. An aromatic group that may be used. When it has a substituent, the number is not limited, but it is preferably 1 or more and 3 or less, more preferably 1. The types of substituents may be different or the same, preferably the same.

  The alkoxy group constituting the alkoxycarbonyl group is preferably an alkoxy group having 1 to 12 carbon atoms or a fluorinated alkoxy group having 1 to 12 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and a methoxy group. Ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group A methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group or an n-hexoxy group is particularly preferable.

  As the alkyl group, a linear alkyl group having 1 to 8 carbon atoms is preferable, and an n-propyl group is more preferable. The substituent that the alkyl group may have is not particularly limited, but is preferably an alkoxycarbonyl group. The alkoxy group constituting the alkoxycarbonyl group is preferably an alkoxy group having 1 to 14 carbon atoms or a fluorinated alkoxy group, more preferably an alkoxy group having 1 to 14 carbon atoms, a methoxy group, an ethoxy group, or n-propoxy. Group, isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group, more preferably methoxy group or n- A butoxy group is particularly preferred.

  As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, and a phenyl group, a biphenyl group, a thienyl group, a furyl group, or a pyridyl group is preferable. More preferred are a phenyl group and a thienyl group. The substituent that the aromatic group may have is preferably an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, or an alkoxy group having 1 to 14 carbon atoms. An alkoxy group having a number of 1 or more and 14 or less is more preferable, and a methoxy group or 2-ethylhexyloxy group is particularly preferable.

Preferred examples of the structure represented by formula (n4) include those in which R ³⁴ and R ³⁵ are both alkoxycarbonyl groups, those in which R ³⁴ and R ³⁵ are both aromatic groups, and R ³⁴ is an aromatic group. And R ³⁵ is a 3- (alkoxycarbonyl) propyl group.

  In order to form a layer containing a fullerene compound using a wet film formation method, the fullerene compound itself can be applied in a liquid state, or the fullerene compound can be applied as a solution with high solubility in some solvent. It is preferable. The solubility of the fullerene compound used in toluene at 25 ° C. is usually 0.1% by mass or more, preferably 0.4% by mass or more, more preferably 0.7% by mass or more. Since the solubility of the fullerene compound is 0.1% by mass or more, the dispersion stability of the fullerene compound in the solution containing the fullerene compound is increased, and aggregation, sedimentation, separation, and the like are less likely to occur. It is preferable in that the film formation by is easy.

  In the case of forming a layer containing a fullerene compound using a wet film forming method, the solvent of the solution containing the fullerene compound is not particularly limited as long as it is a nonpolar organic solvent, but a non-halogen solvent is preferable. Although it is possible to use a halogen-based solvent such as dichlorobenzene, an alternative is demanded from the viewpoint of environmental load. Examples of non-halogen solvents include non-halogen aromatic hydrocarbons. Of these, toluene, xylene, cyclohexylbenzene, and the like are preferable.

(Method for producing fullerene compound)
Although there is no restriction | limiting in particular as a manufacturing method of a fullerene compound, For example, the synthesis | combination of fullerene which has a partial structure (n1) is international publication 2008/059771 or J.H. Am. Chem. Soc. , 2008, 130 (46), 15429-15436.

  The synthesis of fullerene having a partial structure (n2) is described in J. Org. Am. Chem. Soc. 1993, 115, 9798-9799, Chem. Mater. 2007, 19, 5363-5372 or Chem. Mater. It can be carried out according to the description of known documents such as 2007, 19, 5194-5199.

  Synthesis of fullerene having a partial structure (n3) is described in Angew. Chem. Int. Ed. Engl. 1993, 32, 78-80, Tetrahedron Lett. It can be carried out according to the description of known documents such as 1997, 38, 285-288, WO 2008/018931 or WO 2009/086212.

  The synthesis of fullerene having a partial structure (n4) is described in J. Org. Chem. Soc. Perkin Trans. 1, 1997, 1595, Thin Solid Films 489 (2005) 251-256, Adv. Funct. Mater. 2005, 15, 1979-1987 or J. Org. Org. Chem. It can be carried out according to the description of known documents such as 1995, 60, 532-538.

[1.3.2.2 N-alkyl-substituted perylene diimide derivatives]
N-alkyl-substituted perylene diimide derivatives are not particularly limited, and specifically, International Publication No. 2008/063609, International Publication No. 2009/115553, International Publication No. 2009/098250, International Publication No. Examples thereof include compounds described in 2009/000756 and International Publication No. 2009/091670. These compounds are preferable because they have high electron mobility and absorb light in the visible region, and thus can contribute to both charge transport and power generation.

[1.3.2.3 Naphthalenetetracarboxylic acid diimide]
The naphthalenetetracarboxylic acid diimide is not particularly limited, and specific examples thereof include compounds described in International Publication No. 2008/063609, International Publication No. 2007/146250 and International Publication No. 2009/000756. It is done. These compounds are preferable because they have high electron mobility, high solubility, and excellent coating properties.

[1.3.2.4 n-type polymer semiconductor compound]
The n-type polymer semiconductor compound is not particularly limited, but condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid diimide, perylene diimide derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazoles N-type polymer semiconductor comprising at least one of a derivative, a benzothiazole derivative, a benzothiadiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, a quinoxaline derivative, a bipyridine derivative and a borane derivative Compounds and the like.

  Among them, at least one of a borane derivative, a thiazole derivative, a benzothiazole derivative, a benzothiadiazole derivative, an N-alkyl-substituted naphthalenetetracarboxylic acid diimide derivative, and an N-alkyl-substituted perylenetetracarboxylic acid diimide derivative is a constituent unit. Preferred is an n-type polymer semiconductor compound having at least one of N-alkyl-substituted perylenetetracarboxylic acid diimide derivative and N-alkyl-substituted naphthalenetetracarboxylic acid diimide derivative as a constituent unit. .

  Specific examples of the n-type polymer semiconductor compound include compounds described in International Publication No. 2009/098253, International Publication No. 2009/098250, International Publication No. 2010/012710, and International Publication No. 2009/098250. Can be mentioned. These compounds are preferable in that they can contribute to power generation because they absorb light in the visible region, and have high viscosity and excellent coating properties.

[1.4 Substrate (106)]
The photoelectric conversion element 107 has a base material 106 that usually serves as a support. That is, an electrode (cathode) 101, an electron extraction layer 102, an active layer 103, and an electrode (anode) 105 are formed on the substrate 106.

  The material of the base material 106 (base material) is arbitrary as long as the effects of the present invention are not significantly impaired. Preferable examples of the base material include inorganic materials such as quartz, glass, sapphire, and titania, and flexible base materials. In the present invention, the flexible substrate is a substrate having a radius of curvature of usually 0.1 mm or more and 10,000 mm or less. In the case of producing a flexible electronic device, the radius of curvature is preferably 0.3 mm or more, more preferably 1 mm or more, in order to achieve both flexibility and characteristics as a support. It is preferably 3000 mm or less, and more preferably 1000 mm or less. Specific examples of the flexible substrate include, but are not limited to, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, vinyl chloride. Or polyolefin such as polyethylene; organic material (resin substrate) such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, or epoxy resin; paper material such as paper or synthetic paper; stainless steel, Examples thereof include composite materials such as those obtained by coating or laminating a surface of a metal foil such as titanium or aluminum to impart insulation. Examples of the glass include soda glass, blue plate glass, and non-alkali glass. As the glass, alkali-free glass is more preferable in that there are few ions eluted from the glass.

  There is no restriction | limiting in the shape of the base material 106, For example, it may be shapes, such as a board, a film, a sheet | seat. There is no limitation on the film thickness of the substrate 106. The film thickness of the substrate 106 is preferably 5 μm or more, more preferably 20 μm or more, and preferably 20 mm or less, more preferably 10 mm or less. The film thickness of the substrate 106 is preferably 5 μm or more from the viewpoint of improving the strength of the semiconductor device. It is preferable that the thickness of the substrate 106 is 20 mm or less because the manufacturing cost is suppressed and the photoelectric conversion element 107 becomes light. Further, when the material of the substrate 106 is glass, the thickness of the substrate 106 is usually 0.01 mm or more, preferably 0.1 mm or more, and is usually 1 cm or less, preferably 0.5 cm or less. . A film thickness of the glass substrate of 0.01 mm or more is preferable because the mechanical strength increases and it is difficult to break. Moreover, since the film thickness of a glass base material is 0.5 cm or less, since the photoelectric conversion element 107 becomes light, it is preferable.

[1.5 Electrodes (101, 105)]
The pair of electrodes (101, 105) has a function of collecting holes and electrons generated by light absorption. Therefore, the pair of electrodes may include an electrode 105 suitable for collecting holes (hereinafter also referred to as an anode) and an electrode 101 suitable for collecting electrons (hereinafter referred to as a cathode). ) Are preferably used.

  Any one of the pair of electrodes may be translucent, and both may be translucent. Here, having translucency means that sunlight passes through 40% or more. In order for more light to pass through the transparent electrode and reach the active layer 103, the transparent electrode preferably has a solar ray transmittance of 70% or more. The light transmittance can be measured with a normal spectrophotometer.

  Furthermore, the anode 105 and the cathode 101 may have a structure in which two or more layers are stacked. Further, the characteristics (electric characteristics, wetting characteristics, etc.) of the anode 105 and the cathode 101 may be improved by surface treatment.

[1.5.1 Anode (105)]
The anode 105 is preferably an electrode made of a material suitable for collecting holes. The material of the anode 105 is generally a conductive material having a work function larger than that of the material of the cathode 101, and has a function of smoothly extracting holes generated in the active layer 103.

  Examples of the material of the anode 105 include nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zinc oxide (IZO), conductive oxide such as titanium oxide or zinc oxide; gold, platinum , A metal such as silver, chromium or cobalt or an alloy thereof. These substances are preferable because they have a large work function, and are preferable because a conductive polymer material represented by PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be laminated. When laminating such a conductive polymer material, since the work function of the conductive polymer material is large, instead of a material having a large work function as described above, a cathode such as aluminum or magnesium is used. It is also possible to use a metal suitable for the material.

  Alternatively, PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material in which polypyrrole or polyaniline is doped with iodine or the like can be used as the material of the anode 105.

  When the anode 105 is a transparent electrode, it is preferable to use a light-transmitting conductive metal oxide such as ITO, zinc oxide, or tin oxide, and it is particularly preferable to use ITO.

  The film thickness of the anode 105 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, and more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. A film thickness of the anode 105 of 10 nm or more is preferable from the viewpoint of suppressing sheet resistance, and a film thickness of the anode 105 of 10 μm or less means that the photoelectric conversion element 107 is efficiently used for improving light transmittance. This is preferable in that light can be converted into electricity. When the anode 105 is a transparent electrode, it is desirable to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the anode 105 is not particularly limited, but is usually 1Ω / □ or more, and is usually 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less. A lower sheet resistance is preferable in that the photoelectric conversion efficiency can be improved.

  Examples of a method for forming the anode 105 include a dry film forming method such as a vacuum evaporation method or a sputtering method, or a wet film forming method in which an ink containing nanoparticles or a precursor is applied to form a film.

[1.5.2 Cathode (101)]
The cathode 101 is preferably an electrode made of a material suitable for collecting electrons. The material of the cathode 101 is generally a conductive material having a work function smaller than that of the material of the anode 105 and has a function of smoothly extracting electrons generated in the active layer 103. In order to extract electrons more smoothly, the cathode 101 is preferably adjacent to the electron extraction layer 102.

  Examples of the material of the cathode 101 include metals such as platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, and magnesium, and alloys thereof; lithium fluoride Or inorganic salts, such as cesium fluoride; Metal oxides, such as nickel oxide, aluminum oxide, lithium oxide, or cesium oxide, etc. are mentioned. These materials are preferred because they have a small work function. However, since the electron extraction layer 102 has a function of smoothly extracting electrons generated in the active layer 103, a material having a large work function suitable for the material of the anode 105 can be used as the material of the cathode 101. From the viewpoint of electrode protection, the cathode 101 is preferably made of a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium, or indium and an alloy using these metals.

  Although there is no restriction | limiting in particular in the film thickness of the cathode 101, Usually, 10 nm or more, Preferably it is 20 nm or more, More preferably, it is 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. The thickness of the cathode 101 is preferably 10 nm or more because sheet resistance is suppressed. Moreover, it is preferable that the film thickness of the cathode 101 is 10 μm or less because light transmittance is improved and light can be efficiently converted into electricity. When the cathode 101 is a transparent electrode, it is desirable to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the cathode 101 is not particularly limited, but is usually 1000Ω / □ or less, preferably 500Ω / □ or less, and more preferably 100Ω / □ or less. Although there is no restriction on the lower limit, it is usually 1Ω / □ or more. A lower sheet resistance is preferable in that the photoelectric conversion efficiency can be improved.

  Examples of the method for forming the cathode 101 include a dry film forming method such as a vacuum evaporation method or a sputtering method, or a wet film forming method in which an ink containing nanoparticles and a precursor is applied to form a film.

[1.6 Production Method of Photoelectric Conversion Element]
The photoelectric conversion element 107 can be manufactured by sequentially stacking the base material 106, the cathode 101, the electron extraction layer 102, the active layer 103, the hole extraction layer 104, and the anode 105 in accordance with the method described above. A photoelectric conversion element having a different structure, for example, a photoelectric conversion element that does not include at least one of the base 106 and the hole extraction layer 104 can be manufactured by a similar method.

  After laminating the anode 105 and the cathode 101, the photoelectric conversion element 107 is usually 50 ° C. or higher, preferably 80 ° C. or higher, and usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. It is preferable to heat. This process may be referred to as an annealing process process.

  It is preferable that the annealing process be performed at a temperature of 50 ° C. or higher because adhesion between at least one of the electron extraction layer 102 and the electrode 101 and between the electron extraction layer 102 and the active layer 103 can be improved. It is preferable to perform the annealing treatment step at a temperature of 300 ° C. or lower because it is possible to prevent the organic compound in the active layer 103 from being thermally decomposed. In the annealing process, heating may be performed stepwise at different temperatures within the above range.

  The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and is usually 180 minutes or shorter, preferably 60 minutes or shorter. The heating is preferably terminated when the open-circuit voltage, short-circuit current, and fill factor, which are parameters indicating the performance of the photoelectric conversion element, reach a constant value. Moreover, it is preferable to perform an annealing process process under a normal pressure and inert gas atmosphere.

  Although it does not specifically limit as a heating method, The method of putting the photoelectric conversion element 107 in heat sources, such as a hotplate, The method of putting the photoelectric conversion element 107 in heating atmosphere, such as oven, etc. are mentioned. Heating may be performed by a batch method or a continuous method.

[1.7 Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element can be obtained as follows. That is, the current-voltage characteristic is measured by irradiating the photoelectric conversion element with light of AM1.5G at an irradiation intensity of 100 mW / cm ^{2 using a} solar simulator. From the current-voltage curve obtained by measurement, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short circuit current (Jsc), open circuit voltage (Voc), FF (fill factor), series resistance, and shunt resistance can be obtained. .

  The photoelectric conversion efficiency of the photoelectric conversion element according to the present invention is not particularly limited, but is usually 1% or more, preferably 1.5% or more, more preferably 2% or more. On the other hand, there is no particular limitation on the upper limit, but the higher the better.

Examples of a method for measuring the durability of the photoelectric conversion element include a method for obtaining a maintenance ratio of the photoelectric conversion efficiency before and after exposing the photoelectric conversion element to the atmosphere. Specifically, the maintenance rate is obtained as follows.
(Maintenance rate) = (Photoelectric conversion efficiency after N hours of atmospheric exposure) / (Photoelectric conversion efficiency immediately before atmospheric exposure)

  In order to put the photoelectric conversion element into practical use, it is also important that the photoelectric conversion element has high photoelectric conversion efficiency and high durability, in addition to being easy and inexpensive to manufacture. The photoelectric conversion efficiency maintenance rate of the photoelectric conversion element according to the present invention is preferably 60% or more, more preferably 80% or more before and after exposure to the atmosphere for one week, and the higher the higher.

[2. Solar cell according to the present invention]
The photoelectric conversion element 107 according to the present invention is preferably used as a solar cell, particularly a solar cell element of a thin film solar cell.

  FIG. 2 is a cross-sectional view schematically showing the configuration of a thin film solar cell as one embodiment of the present invention. As shown in FIG. 2, the thin film solar cell 14 of this embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a solar cell element. 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. And light is irradiated from the side (downward in the figure) where the weather-resistant protective film 1 is formed, and the solar cell element 6 generates power. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as a back sheet 10 described later, at least one of the getter material film 8 and the gas barrier film 9 is not used depending on the application. May be.

[2.1 Weatherproof protective film (1)]
The weather-resistant protective film 1 is a film that protects the solar cell element 6 from weather changes. By covering the solar cell element 6 with the weather-resistant protective film 1, the solar cell element 6 and the like are protected from weather changes and the power generation capacity is kept high. Since the weatherproof protective film 1 is located on the outermost layer of the thin film solar cell 14, the surface of the thin film solar cell 14 has at least one of weather resistance, heat resistance, transparency, water repellency, stain resistance and mechanical strength. It is preferable to have properties suitable for a covering material and to maintain it for a long period of time in outdoor exposure.

  Moreover, it is preferable that the weather-resistant protective film 1 transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the transmittance of visible light (wavelength 360 to 830 nm) is preferably 80% or more, and the upper limit is not limited. Furthermore, since the thin-film solar cell 14 is often heated by receiving light, it is preferable that the weather-resistant protective film 1 also has heat resistance. From this viewpoint, the melting point of the constituent material of the weather-resistant protective film 1 is usually 100 ° C. or higher and 350 ° C. or lower.

  The material which comprises the weather-resistant protective film 1 is arbitrary as long as it can protect the solar cell element 6 from a weather change. Examples of the material are polyethylene resin, polypropylene resin, cyclic polyolefin resin, AS (acrylonitrile-styrene) resin, ABS (acrylonitrile-butadiene-styrene) resin, polyvinyl chloride resin, fluorine resin, polyethylene terephthalate or polyethylene. Examples thereof include polyester resins such as naphthalate, phenol resins, polyacrylic resins, polyamide resins such as various nylons, polyimide resins, polyamide-imide resins, polyurethane resins, cellulose resins, silicon resins, and polycarbonate resins.

  In addition, the weather-resistant protective film 1 may be formed with 1 type of material, and may be formed with 2 or more types of materials. Moreover, although the weather-resistant protective film 1 may be formed with the single layer film, the laminated | multilayer film provided with the film of two or more layers may be sufficient as it.

  The thickness of the weather-resistant protective film 1 is not particularly defined, but is usually 10 μm or more and 200 μm or less.

  Further, the weatherproof protective film 1 may be subjected to a surface treatment such as at least one of a corona treatment and a plasma treatment in order to improve adhesiveness with other films.

  The weatherproof protective film 1 is preferably provided on the outer side as much as possible in the thin-film solar cell 14. This is because more of the constituent members of the thin-film solar cell 14 can be protected.

[2.2 UV cut film (2)]
The ultraviolet cut film 2 is a film that prevents the transmission of ultraviolet rays. The ultraviolet cut film 2 is provided in the light receiving portion of the thin-film solar cell 14, and the ultraviolet cut film 2 covers the light receiving surface 6a of the solar cell element 6, so that the solar cell element 6 and, if necessary, the gas barrier films 3 and 9 are exposed to ultraviolet rays. The power generation capacity can be maintained at a high level.

  The degree of the ability to suppress the transmission of ultraviolet rays required for the ultraviolet cut film 2 is preferably such that the transmittance of ultraviolet rays (for example, wavelength of 300 nm) is 50% or less, and there is no limit on the lower limit. Moreover, it is preferable that the ultraviolet cut film 2 transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the transmittance of visible light (wavelength 360 to 830 nm) is preferably 80% or more, and the upper limit is not limited.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, the ultraviolet cut film 2 preferably has heat resistance. From this viewpoint, the melting point of the constituent material of the ultraviolet cut film 2 is usually 100 ° C. or higher and 350 ° C. or lower.

  Moreover, it is preferable that the ultraviolet cut film 2 is high in flexibility, has good adhesion to an adjacent film, and can cut water vapor and oxygen.

  The material which comprises the ultraviolet cut film 2 is arbitrary if the intensity | strength of an ultraviolet-ray can be weakened. Examples of the material include films formed by blending an ultraviolet absorber with an epoxy, acrylic, urethane, or ester resin. Further, a film in which a layer of an ultraviolet absorbent dispersed or dissolved in a resin (hereinafter referred to as “ultraviolet absorbing layer” as appropriate) is formed on a base film may be used.

  As the ultraviolet absorber, for example, a salicylic acid-based, benzophenone-based, benzotriazole-based, or cyanoacrylate-based one can be used. In addition, 1 type of ultraviolet absorbers may be used and 2 or more types may be used together by arbitrary combinations and ratios. As described above, a film in which an ultraviolet absorbing layer is formed on a base film can also be used as the ultraviolet absorbing film. Such a film can be produced, for example, by applying a coating solution containing an ultraviolet absorber on a substrate film and drying it.

  Although the material of a base film is not specifically limited, For example, polyester is mentioned at the point from which the balance of heat resistance and a softness | flexibility is obtained.

  Examples of specific products of the ultraviolet cut film 2 include cut ace (MKV Plastic Co., Ltd.). In addition, the ultraviolet cut film 2 may be formed with 1 type of material, and may be formed with 2 or more types of materials.

  Further, the ultraviolet cut film 2 may be formed of a single layer film, but may be a laminated film including two or more layers. The thickness of the ultraviolet cut film 2 is not particularly limited, but is usually 5 μm or more and 200 μm or less.

  Although the ultraviolet cut film 2 should just be provided in the position which covers at least one part of the light-receiving surface 6a of the solar cell element 6, Preferably it is provided in the position which covers all the light-receiving surfaces 6a of the solar cell element 6. FIG. However, the ultraviolet cut film 2 may be provided at a position other than the position covering the light receiving surface 6 a of the solar cell element 6.

[2.3 Gas barrier film (3)]
The gas barrier film 3 is a film that prevents permeation of water and oxygen. By covering the solar cell element 6 with the gas barrier film 3, the solar cell element 6 can be protected from water and oxygen, and the power generation capacity can be kept high.

The degree of moisture-proof capability required for the gas barrier film 3 varies depending on the type of the solar cell element 6 and the like. For example, the water vapor transmission rate per unit area (1 m ² ) is usually 1 × 10. It is preferably ⁻¹ g / m ² / day or less, and the lower limit is not limited.

The degree of oxygen permeability required for the gas barrier film 3 varies depending on the type of the solar cell element 6 and the like. For example, the oxygen permeability per unit area (1 m ² ) is usually 1 ×. It is preferable that it is 10 < ^-1 > cc / m < ² > / day / atm or less, and there is no restriction | limiting in a lower limit.

  Moreover, it is preferable that the gas barrier film 3 transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the transmittance of visible light (wavelength 360 to 830 nm) is usually 60% or more, and there is no upper limit.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, it is preferable that the gas barrier film 3 also has heat resistance. From this viewpoint, the melting point of the constituent material of the gas barrier film 3 is usually 100 ° C. or higher and 350 ° C. or lower.

  The specific configuration of the gas barrier film 3 is arbitrary as long as the solar cell element 6 can be protected from water. However, since the manufacturing cost increases as the amount of water vapor or oxygen that can permeate the gas barrier film 3 increases, it is preferable to use an appropriate film considering these points comprehensively.

Particularly suitable gas barrier film 3 includes, for example, a film obtained by vacuum-depositing SiO _x on a base film such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN).

  In addition, the gas barrier film 3 may be formed with 1 type of material, and may be formed with 2 or more types of materials. The gas barrier film 3 may be formed of a single layer film, but may be a laminated film including two or more layers.

  The thickness of the gas barrier film 3 is not particularly defined, but is usually 5 μm or more and 200 μm or less.

  As long as the gas barrier film 3 covers the solar cell element 6 and can be protected from moisture and oxygen, the formation position is not limited. However, the front surface of the solar cell element 6 (surface on the light receiving surface side, lower surface in FIG. 2) and It is preferable to cover the back surface (the surface opposite to the light receiving surface; the upper surface in FIG. 2). This is because the front and back surfaces of the thin film solar cell 14 are often formed in a larger area than the other surfaces. In this embodiment, the gas barrier film 3 covers the front surface of the solar cell element 6, and a gas barrier film 9 described later covers the back surface of the solar cell element 6. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as a back sheet 10 described later, at least one of the getter material film 8 and the gas barrier film 9 is not used depending on the application. May be.

[2.4 Getter material film (4)]
The getter material film 4 is a film that absorbs at least one of moisture and oxygen. By covering the solar cell element 6 with the getter material film 4, the solar cell element 6 and the like are protected from at least one of moisture and oxygen, and the power generation capacity is kept high. Here, unlike the gas barrier film 3, the getter material film 4 does not prevent moisture permeation but absorbs moisture. By using a film that absorbs moisture, the getter material film 4 captures moisture that slightly enters the space formed by the gas barrier films 3 and 9 when the solar cell element 6 is covered with the gas barrier films 3 and 9 and the like. Thus, the influence of moisture on the solar cell element 6 can be eliminated.

The degree of moisture absorption capacity of the getter material film 4 is usually 0.1 mg / cm ² or more, and although there is no upper limit, it is usually 10 mg / cm ² or less. Also, the getter material film 4 absorbs oxygen because oxygen that slightly enters the space formed by the gas barrier films 3 and 9 when the solar cell element 6 is covered with the gas barrier films 3 and 9 or the like is obtained by the getter material film 4. It is preferable because the film 4 can capture and eliminate the influence of oxygen on the solar cell element 6.

  Furthermore, it is preferable that the getter material film 4 transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the transmittance of visible light (wavelength 360 to 830 nm) is usually 60% or more, and there is no upper limit.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, the getter material film 4 preferably has heat resistance. From this viewpoint, the melting point of the constituent material of the getter material film 4 is usually 100 ° C. or higher and 350 ° C. or lower.

  The material constituting the getter material film 4 is arbitrary as long as it can absorb at least one of moisture and oxygen. Examples of the material include alkali metal, alkaline earth metal or alkaline earth metal oxides; alkali metal or alkaline earth metal hydroxides; silica gel, zeolitic compounds, magnesium sulfate. And sulfates such as sodium sulfate and nickel sulfate; and organometallic compounds such as aluminum metal complexes and aluminum oxide octylates. Specifically, examples of the alkaline earth metal include Ca, Sr, and Ba. Examples of the alkaline earth metal oxide include CaO, SrO, and BaO. In addition, Zr-Al-BaO and aluminum metal complexes are also included. Specific product names include, for example, OleDry (Futaba Electronics).

  Examples of the substance that absorbs oxygen include activated carbon, silica gel, activated alumina, molecular sieve, magnesium oxide, and iron oxide. In addition, inorganic salts such as Fe, Mn, or Zn, or sulfates, chlorides, or nitrates of these metals are also included.

  In addition, the getter material film 4 may be formed of one type of material or may be formed of two or more types of materials. The getter material film 4 may be formed of a single layer film, but may be a laminated film including two or more layers.

  The thickness of the getter material film 4 is not particularly specified, but is usually 5 μm or more and 200 μm or less.

  The formation position of the getter material film 4 is not limited as long as it is in the space formed by the gas barrier films 3 and 9, but the front surface of the solar cell element 6 (the surface on the light receiving surface side, the lower surface in FIG. 2). And it is preferable to cover the back surface (surface opposite to the light receiving surface; upper surface in FIG. 2). This is because, in the thin film solar cell 14, the front and back surfaces are often formed in a larger area than the other surfaces, and therefore moisture and oxygen tend to enter through these surfaces. From this viewpoint, the getter material film 4 is preferably provided between the gas barrier film 3 and the solar cell element 6. In this embodiment, the getter material film 4 covers the front surface of the solar cell element 6, a getter material film 8 described later covers the back surface of the solar cell element 6, and the getter material films 4 and 8 are respectively the solar cell element 6 and the gas barrier film 3. , 9 are located between them. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as the back sheet 10 described later, at least one of the getter material film 8 and the gas barrier film 9 must be used depending on the application. Also good.

[2.5 Sealant (5)]
The sealing material 5 is a film that reinforces the solar cell element 6. Since the solar cell element 6 is thin, the strength is usually weak, and thus the strength of the thin film solar cell tends to be weak. However, the strength can be maintained high by the sealing material 5.

  Moreover, it is preferable that the sealing material 5 has high strength from the viewpoint of maintaining the strength of the thin-film solar cell 14. The specific strength is related to the strength of the weatherproof protective film 1 other than the sealing material 5 and the strength of the back sheet 10 and is generally difficult to define, but the thin film solar cell 14 as a whole has good bending workability. However, it is desirable to have a strength that does not cause peeling of the bent portion.

  Moreover, it is preferable that the sealing material 5 permeate | transmits visible light from a viewpoint which does not prevent the light absorption of the solar cell element 6. FIG. For example, the transmittance of visible light (wavelength 360 to 830 nm) is usually 60% or more, and there is no upper limit.

  The thickness of the sealing material 5 is not particularly specified, but is usually 2 μm or more and usually 700 μm or less.

  The T-type peel adhesion strength of the sealing material 5 to the substrate is usually 1 N / inch or more and usually 2000 N / inch or less. It is preferable that the T-type peel adhesive strength is 1 N / inch or more in terms of ensuring the long-term durability of the module. It is preferable that the T-type peel adhesive strength is 2000 N / inch or less in that the base material, the barrier film, and the adhesive can be separated and discarded when the solar cell module is discarded. The T-type peel adhesion strength is measured by a method according to JIS K6854-3 (1999).

  The constituent material of the sealing material 5 is not particularly limited as long as it has the above characteristics, but sealing of organic / inorganic solar cells, sealing of organic / inorganic LED elements, sealing of electronic circuit boards, etc. In general, a sealing material generally used can be used.

  Specifically, a thermosetting resin composition, a thermoplastic resin composition, or an active energy ray-curable resin composition can be used. The active energy ray-curable resin composition is, for example, a resin that is cured by ultraviolet rays, visible light, electron beams, or the like. More specifically, an ethylene-vinyl acetate copolymer (EVA) resin composition, a hydrocarbon resin composition, an epoxy resin composition, a polyester resin composition, an acrylic resin composition, and a urethane resin composition. Or a silicone resin composition, etc., and thermosetting, thermoplasticity and active energy ray curable by the main chain, branched chain, terminal chemical modification, molecular weight adjustment, or additive of each polymer. Such characteristics are developed.

  Moreover, since the thin film solar cell 14 is often heated by receiving light, it is preferable that the sealing material 5 also has heat resistance. From this viewpoint, the melting point of the constituent material of the sealing material 5 is usually 100 ° C. or higher and 350 ° C. or lower.

The density of the constituent material for sealing material in the sealing material 5 is preferably 0.80 g / cm ³ or more, and there is no upper limit. The measurement and evaluation of density can be performed by a method based on JIS K7112 (1999).

  Although there is no restriction | limiting in the position which provides the sealing material 5, Usually, it provides so that the solar cell element 6 may be inserted | pinched. This is for reliably protecting the solar cell element 6. In this embodiment, the sealing material 5 and the sealing material 7 are provided on the front surface and the back surface of the solar cell element 6, respectively.

[2.6 Solar cell element (6)]
The solar cell element 6 is the same as the photoelectric conversion element 107 described above.

  Although only one solar cell element 6 may be provided for each thin film solar cell 14, usually two or more solar cell elements 6 are provided. The specific number of solar cell elements 6 may be set arbitrarily. When a plurality of solar cell elements 6 are provided, the solar cell elements 6 are often arranged in an array.

  When a plurality of solar cell elements 6 are provided, the solar cell elements 6 are usually electrically connected to each other, and electricity generated from the connected group of solar cell elements 6 is taken out from a terminal (not shown). At this time, the solar cell elements are usually connected in series in order to increase the voltage.

  Thus, when connecting the solar cell elements 6, it is preferable that the distance between the solar cell elements 6 is small, and by extension, the gap between the solar cell element 6 and the solar cell element 6 is preferably narrow. This is because the light receiving area of the solar cell element 6 is widened to increase the amount of received light, and the amount of power generated by the thin film solar cell 14 is increased.

[2.7 Sealant (7)]
The sealing material 7 is a film similar to the sealing material 5 described above, and the same material as the sealing material 7 can be used in the same manner except that the arrangement position is different. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[2.8 Getter material film (8)]
The getter material film 8 is the same film as the getter material film 4 described above, and the same material as the getter material film 4 can be used as necessary, except for the arrangement position. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[2.9 Gas barrier film (9)]
The gas barrier film 9 is the same film as the gas barrier film 3 described above, and the same material as the gas barrier film 9 can be used as necessary except that the arrangement position is different. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[2.10 Back sheet (10)]
The back sheet 10 is the same film as the weather-resistant protective film 1 described above, and the same material as the weather-resistant protective film 1 can be used in the same manner except that the arrangement position is different. In addition, if the back sheet 10 is difficult to permeate water and oxygen, the back sheet 10 can also function as a gas barrier layer. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[2.11 Dimensions, etc.]
The thin film solar cell 14 of the present embodiment is usually a thin film member. Thus, by forming the thin film solar cell 14 as a film-like member, the thin film solar cell 14 can be easily installed in a building material, an automobile, an interior, or the like. The thin-film solar cell 14 is light and difficult to break. Therefore, a highly safe solar cell can be obtained, and can be applied to curved surfaces, so that it can be used for more applications. Furthermore, since the thin film solar cell 14 is thin and light, it is preferable in terms of distribution such as transportation and storage. Furthermore, since the thin-film solar cell 14 is in a film form, roll-to-roll manufacturing is possible, and a significant cost cut in manufacturing is possible.

  Although there is no restriction | limiting in the specific dimension of the thin film solar cell 14, The thickness is usually 300 micrometers or more and 3000 micrometers or less.

[2.12 Manufacturing method]
There is no limitation on the method for manufacturing the solar cell according to the present invention. For example, as a method for manufacturing the thin-film solar cell 14 shown in FIG. 2, a method of performing a laminate sealing step after the laminate shown in FIG. Can be mentioned. Since the solar cell element of this embodiment is excellent in heat resistance, it is preferable in that deterioration due to the laminate sealing step can be reduced.

  The laminate production shown in FIG. 2 can be performed using a known technique. The method of the laminate sealing step is not particularly limited as long as the effects of the present invention are not impaired, but for example, wet lamination, dry lamination, hot melt lamination, extrusion lamination, coextrusion molding lamination, extrusion coating, photocuring adhesive Laminate or thermal laminate may be mentioned. Of these, the laminating method using a photo-curing adhesive having a proven record in organic EL device sealing, the hot melt laminating method or the thermal laminating method having a proven record in solar cells is preferable, and the hot melt laminating method or the thermal laminating method is sheet-like sealing. It is more preferable at the point which can use material.

  The heating temperature in the laminate sealing step is usually 130 ° C or higher, preferably 140 ° C or higher, and is usually 180 ° C or lower, preferably 170 ° C or lower. The heating time in the laminate sealing step is usually 10 minutes or longer, preferably 20 minutes or longer, and is usually 100 minutes or shorter, preferably 90 minutes or shorter. The pressure in the laminate sealing step is usually 0.001 MPa or more, preferably 0.01 MPa or more, and usually 0.2 MPa or less, preferably 0.1 MPa or less. Sealing can be reliably performed by setting the pressure within this range, and dimensional stability is ensured by suppressing the protrusion of the sealing materials 5 and 7 from the end and reducing the film thickness due to over-pressurization. Yes. In addition, what connected two or more solar cell elements 6 in series or in parallel can be manufactured similarly to said method.

[2.13 Applications]
There is no restriction | limiting in the use of the solar cell which concerns on this invention, especially the thin film solar cell 14 mentioned above, It can use for arbitrary uses. Examples of fields in which the solar cell according to the present invention can be used include solar cells for building materials, automobile solar cells, interior solar cells, railroad solar cells, marine solar cells, airplane solar cells, and spacecraft solar cells. Examples include batteries, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

  The solar cell according to the present invention, in particular, the thin-film solar cell may be used as it is or may be used as a solar cell module by installing one or more solar cells on a substrate. For example, as schematically shown in FIG. 3, a solar cell module 13 including a thin film solar cell 14 on a substrate 12 can be prepared and used at a place of use. As a specific example, when a building material plate is used as the base material 12, a solar cell panel can be produced as the solar cell module 13 by providing the thin film solar cell 14 on the surface of the plate material.

  The substrate 12 is a support member that supports the thin film solar cell 14. It does not restrict | limit especially as a material which forms the base material 12, Inorganic materials, such as quartz, glass, sapphire, or titania, or a flexible base material is mentioned. Specific examples of the flexible substrate include, but are not limited to, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, vinyl chloride. Or polyolefin such as polyethylene; organic material (resin substrate) such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, or epoxy resin; paper material such as paper or synthetic paper; stainless steel, Examples thereof include composite materials such as those obtained by coating or laminating a surface of a metal foil such as titanium or aluminum to impart insulation.

  In addition, as a material of a base material, 1 type of material may be used and 2 or more types may be used together by arbitrary combinations and a ratio. Moreover, carbon fiber may be included in these organic materials or paper materials to reinforce the mechanical strength. When the example of the base material 12 is given, Alpolic (registered trademark; manufactured by Mitsubishi Plastics) and the like may be mentioned.

  Although there is no restriction | limiting in the shape of the base material 12, Usually, a board | plate material is used. Moreover, what is necessary is just to set the material of the base material 12, a dimension, etc. arbitrarily according to the use environment. This solar cell panel can be installed on the outer wall of a building.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example.

[Example 1]
Zinc acetate dihydrate (Wako Pure Chemical Industries, 1760 mg, 8.0 mmol) and sodium acetate (Wako Pure Chemical Industries, 13 mg, 0.16 mmol) were added to ethanolamine (Aldrich, 0.50 mL). And it dissolved in 2-methoxyethanol (Aldrich company make, 10 mL), and the precursor solution of the zinc oxide containing a sodium compound was prepared by stirring at 60 degreeC for 1 hour.

Next, regioregular poly-3-hexylthiophene (P3HT, manufactured by Rieke Metals) and C ₆₀ (Ind) ₂ (manufactured by Frontier Carbon Co.) at a mass ratio of 1: 0.95 and a total concentration of 3. It melt | dissolved in o-xylene (made by Wako Pure Chemical Industries Ltd.) so that it might become 5 mass%. The obtained solution was stirred and mixed using a stirrer at 80 ° C. for 1 hour under a nitrogen atmosphere. The solution after stirring was filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter to prepare an organic active layer coating solution.

  A glass substrate on which an indium tin oxide (ITO) transparent conductive film (155 nm thick) is deposited is subjected to ultrasonic cleaning with ultrapure water to which a surfactant is added, water cleaning with ultrapure water, and ultrasonic cleaning with ultrapure water. After washing in order, it was dried with nitrogen blow, and finally ultraviolet ozone cleaning was performed. On the cleaned substrate, the zinc oxide precursor solution prepared as described above is spin-coated in the air with a spin coater ACT-300DII (manufactured by Active), and then heated and dried at 150 ° C. for 60 minutes in the air. Thus, an electron extraction layer (thickness: about 40 nm) containing a sodium compound and zinc oxide was formed.

  Next, the organic active layer coating liquid prepared as described above is spin-coated on the electron extraction layer with a spin coater MS-A100 (manufactured by Mikasa) in a nitrogen atmosphere, thereby forming an organic active layer (film thickness of about 200 nm). ) Was formed.

Thereafter, an aqueous dispersion of poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) containing 1% by mass of a surfactant (manufactured by Nissin Chemical Industry, Olphine EXP4036) CLEVIOS ^™ PVP AI4083 ”) was filtered through a 0.45 μm polyvinylidene fluoride (PVDF) filter, spin-coated on the organic active layer with a spin coater ACT-300DII (manufactured by Active) in the atmosphere, and then nitrogen. A hole extraction layer (film thickness: about 100 nm) was formed on the organic active layer by heating and drying at 150 ° C. for 10 minutes.

  Furthermore, after providing a silver electrode (thickness: 100 nm) on the hole extraction layer by a vacuum deposition method, a 5-mm square bulk heterojunction photoelectric conversion element was produced by heating on a hot plate at 120 ° C. for 5 minutes.

The obtained photoelectric conversion element is irradiated with light of 100 mW / cm ^{2 with} a solar simulator (AM1.5G) from the ITO electrode side, and an ITO electrode and an aluminum electrode are used with a source meter 2400 type (manufactured by Keithley Instruments). The current-voltage characteristics between and were measured. Based on the measured current-voltage characteristics, an open circuit voltage Voc (V), a short circuit current density Jsc (mA / cm ² ), a form factor FF, and a photoelectric conversion efficiency PCE (%) were calculated. The measurement results are shown in Table 1.

Here, the open circuit voltage Voc is the voltage value (V) when the current value = 0 (mA / cm ² ), and the short circuit current density Jsc is the current density (mA / mA when the voltage value = 0 (V). cm ² ). The form factor (FF) is a factor representing the internal resistance, and is represented by the following expression when the maximum output point is Pmax.
FF = Pmax / (Voc × Jsc)
Further, the photoelectric conversion efficiency PCE (%) is given by the following equation when the incident energy is Pin.
PCE = Pmax / Pin = Voc × Jsc × FF / Pin × 100

<X-ray photoelectron spectroscopy (XPS) measurement>
In order to determine the composition ratio (atomic%) of the alkali metal atom (sodium atom) to the metal atom (zinc atom) of the metal oxide in the electron extraction layer formed in Example 1, the electron extraction was performed under the same conditions. Layers were prepared and X-ray photoelectron spectroscopy (XPS) measurements were performed.

  That is, the X-ray photoelectron spectroscopy (XPS) measurement of the layer (film thickness of about 40 nm) containing a sodium compound and zinc oxide produced in the same manner as in Example 1 was performed.

  Specifically, zinc acetate dihydrate (Wako Pure Chemical Industries, 1760 mg, 8.0 mmol) and sodium acetate (Wako Pure Chemical Industries, 13 mg, 0.16 mmol) were added to ethanolamine (Aldrich). , 0.50 mL) and 2-methoxyethanol (Aldrich, 10 mL) and stirred at 60 ° C. for 1 hour to prepare a zinc oxide precursor solution containing a sodium compound.

  Next, the glass substrate on which an indium tin oxide (ITO) transparent conductive film (155 nm thickness) is deposited is subjected to ultrasonic cleaning with ultrapure water to which a surfactant is added, ultrapure water, ultrapure water, and ultrapure water. After cleaning in the order of sonic cleaning, it was dried with nitrogen blow, and finally ultraviolet ozone cleaning was performed. On the cleaned substrate, the zinc oxide precursor solution prepared as described above is spin-coated in the air with a spin coater ACT-300DII (manufactured by Active), and then heated and dried at 150 ° C. for 60 minutes in the air. Thereby, the mixed layer (film thickness of about 40 nm) containing a sodium compound and zinc oxide was formed.

X-ray photoelectron spectroscopy (XPS) measurement of the mixed layer containing the prepared sodium compound and zinc oxide was performed. The XPS measurement method and measurement results are as follows.
Measuring device: Quantum2000 manufactured by PHI
X-ray source: Monochromatic Al-Kα, output 16 kV-34 W
Charge neutralization: combined use of electron gun (5 μA) and ion gun (2 V) Spectroscopic system: path energy 187.85 eV (wide spectrum)
58.70eV (depth profile)
Measurement area: 300 μm
Extraction angle: 45 ° (from surface)
Na (1s): Zn (2p)
10.04 nm from the surface 1.13: 100

  As described above, the inside of the mixed layer prepared using the zinc oxide precursor solution containing 2 atom% of sodium atoms with respect to the number of zinc atoms contains 1.13 atom% of sodium with respect to the number of zinc atoms. It can be seen that atoms exist. The results are shown in Table 1.

  In the following examples and comparative examples, the composition ratio of alkali metal atoms and the like to the metal atoms of the metal oxide in the electron extraction layer is based on the above-mentioned XPS measurement results, and the atomic radius of the alkali metal atoms and the like and the electron extraction layer This was calculated by considering the composition ratio of the precursor solution. Easiness of inclusion of lithium atoms, sodium atoms, and potassium atoms, which are the same alkali metal atoms, into the metal oxide can be approximated as being inversely proportional to the size of the atoms. The size of the atom can be approximated as being proportional to the third power of the atomic radius derived from the formula of the volume of the sphere. Therefore, for example, the composition ratio of lithium atoms to the metal atoms of the metal oxide in the electron extraction layer is the composition ratio of sodium atoms to the metal atoms of the metal oxide in the electron extraction layer obtained by XPS measurement, and the lithium atoms And the atomic radius of sodium atoms. In addition, as an atomic radius, the covalent bond radius (based on an empirical rule) described in the web element (http://www.webelements.com/) was used.

[Example 2]
In Example 1, except that 20 mg (0.24 mmol) of sodium acetate was used, a 5 mm square photoelectric conversion device was produced in the same manner as in Example 1, and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Moreover, the composition ratio of the alkali metal atom with respect to the metal atom of the metal oxide in an electron extraction layer was calculated | required by calculation from the XPS measurement result in Example 1, and the composition ratio of the precursor solution for electron extraction layers. The results are shown in Table 1.

[Example 3]
In Example 1, a 5 mm square photoelectric conversion device was prepared in the same manner as in Example 1 except that potassium acetate (Wako Pure Chemical Industries, 16 mg, 0.16 mmol) was used instead of sodium acetate. The current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atom (154 pm), And the atomic radius of the potassium atom (196 pm). The results are shown in Table 1.

[Example 4]
In Example 1, a 5 mm square photoelectric conversion device was prepared in the same manner as in Example 1 except that potassium acetate (Wako Pure Chemical Industries, 24 mg, 0.24 mmol) was used instead of sodium acetate. The current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 3. The results are shown in Table 1.

[Example 5]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (Wako Pure Chemical Industries, 4 mg. 0.04 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atom (154 pm), And calculated from the atomic radius of lithium atoms (134 pm). The results are shown in Table 1.

[Example 6]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (manufactured by Wako Pure Chemical Industries, 8 mg, 0.08 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 7]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (Wako Pure Chemical Industries, 16 mg, 0.16 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 8]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (Wako Pure Chemical Industries, 24 mg, 0.24 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 9]
In Example 1, a 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (Wako Pure Chemical Industries, 41 mg, 0.40 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 10]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd., 82 mg, 0.80 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 11]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (Wako Pure Chemical Industries, 245 mg, 2.40 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 12]
Titanium tetraisopropoxide (Wako Pure Chemical Industries, 0.2 mL, 0.68 mmol) and lithium acetate dihydrate (Wako Pure Chemical Industries, 3.5 mg, 0.034 mmol) were mixed with isopropanol ( The precursor solution of the titanium oxide containing a lithium compound was prepared by dissolving in Wako Pure Chemical Industries Ltd. (14 mL) and stirring at 60 ° C. for 1 hour. A 5 mm square photoelectric conversion element was produced in the same manner as in Example 1 except that the titanium oxide precursor solution thus prepared was used instead of the zinc oxide precursor solution, and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Example 13]
In Example 12, except that 10.4 mg (0.10 mmol) of lithium acetate dihydrate was used, a 5 mm square photoelectric conversion device was prepared and current-voltage characteristics were measured in the same manner as in Example 12. did. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, a 5 mm square photoelectric conversion element was produced in the same manner as in Example 1 except that sodium acetate was not added, and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of alkali metal atoms to metal atoms of the metal oxide in the electron extraction layer is 0 atomic% because the electron extraction layer does not contain alkali metal atoms. This is shown in Table 1.

[Comparative Example 2]
In Example 1, a 5 mm square photoelectric conversion device was produced in the same manner as in Example 1 except that cesium carbonate (manufactured by Kojundo Chemical Laboratory Co., Ltd., 26 mg, 0.08 mmol) was used instead of sodium acetate. Then, the current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of cesium atoms to metal atoms of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atoms (154 pm), and It calculated | required by calculation from the atomic radius (225 pm) of a cesium atom. The results are shown in Table 1.

[Comparative Example 3]
In Example 1, a 5 mm square photoelectric conversion element was prepared in the same manner as in Example 1 except that aluminum acetate hydroxide hydrate (Aldrich, 26 mg, 0.16 mmol) was used instead of sodium acetate. The current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of aluminum atoms to metal atoms of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atoms (154 pm), and It calculated | required by calculation from the atomic radius (118 pm) of an aluminum atom. The results are shown in Table 1.

[Comparative Example 4]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that gallium nitrate hydrate (manufactured by Kojundo Chemical Laboratory Co., Ltd., 41 mg, 0.16 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of gallium atoms to metal atoms of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atoms (154 pm), and It calculated | required by calculation from the atomic radius (126 pm) of a gallium atom. The results are shown in Table 1.

[Comparative Example 5]
In Example 1, a 5 mm square photoelectric conversion device was prepared in the same manner as in Example 1 except that indium acetate hydrate (Aldrich, 47 mg, 0.16 mmol) was used instead of sodium acetate. The current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of indium atoms to metal atoms of the metal oxide in the electron extraction layer is the XPS measurement result in Example 1, the composition ratio of the precursor solution for the electron extraction layer, the atomic radius of sodium atoms (154 pm), and It calculated | required by calculation from the atomic radius (144pm) of an indium atom. The results are shown in Table 1.

[Comparative Example 6]
In Example 1, 5 mm square photoelectric conversion was performed in the same manner as in Example 1 except that lithium acetate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd., 408 mg, 4.00 mmol) was used instead of sodium acetate. An element was fabricated and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  Further, the composition ratio of the alkali metal atom to the metal atom of the metal oxide in the electron extraction layer was determined by the same calculation method as in Example 5. The results are shown in Table 1.

[Comparative Example 7]
In Example 12, except that lithium acetate dihydrate was not added, a 5 mm square photoelectric conversion device was produced in the same manner as in Example 12, and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of alkali metal atoms to metal atoms of the metal oxide in the electron extraction layer is 0 atomic% because the electron extraction layer does not contain alkali metal atoms. This is shown in Table 1.

[Comparative Example 8]
In Example 12, a 5 mm square was obtained in the same manner as in Example 12 except that cesium carbonate (manufactured by Kojundo Chemical Laboratory Co., Ltd., 6.5 mg, 0.02 mmol) was used instead of lithium acetate dihydrate. A photoelectric conversion element was prepared, and current-voltage characteristics were measured. The measurement results are shown in Table 1.

  The composition ratio of cesium atoms to metal atoms in the metal oxide in the electron extraction layer was determined by the same calculation method as in Comparative Example 2. The results are shown in Table 1.

[Comparative Example 9]
In Example 1, a 5 mm square photoelectric conversion element was produced and current-voltage characteristics were measured in the same manner as in Example 1 except that the electron extraction layer was not formed. The measurement results are shown in Table 1.

  In Table 1, “composition ratio” represents a composition ratio of an alkali metal atom (sodium atom, potassium atom or lithium atom) to a metal atom of a metal oxide.

  As can be seen from Examples 1 to 11 and Comparative Examples 1 to 5, in the photoelectric conversion element using zinc oxide as the metal oxide in the electron extraction layer, the electron extraction layer contains sodium, potassium, or lithium in a specific ratio. In that case, higher open-circuit voltage and conversion efficiency can be obtained as compared with the case of containing an impurity selected from zinc oxide containing no impurities or an atom selected from a group 13 element such as cesium, aluminum, gallium, or indium. I can confirm. Further, as in Comparative Example 6, when the electron extraction layer contains lithium having a composition ratio larger than 30 atomic% with respect to zinc atoms, it can be confirmed that the conversion efficiency is extremely lowered. This is presumably because a uniform film could not be formed because the ratio of lithium atoms contained in the electron extraction layer was too large.

  In addition, as can be seen from Examples 12 to 13 and Comparative Examples 7 to 8, the same tendency as in the case of using zinc oxide was observed in the photoelectric conversion element using titanium oxide as the metal oxide in the electron extraction layer. It was. Therefore, it is considered that the present invention can be applied to oxides of all metals other than alkali metal elements.

DESCRIPTION OF SYMBOLS 101 Cathode 102 Electron taking-out layer 103 Active layer 104 Hole taking-out layer 105 Anode 106 Base material 107 Photoelectric conversion element 1 Weather-resistant protective film 2 UV cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealing material 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell

Claims (4)

A pair of electrodes, an active layer between the electrodes, and an electron extraction layer between the active layer and one of the electrodes,
The electron extraction layer includes a mixed layer containing at least one alkali metal element selected from the group consisting of lithium, sodium, and potassium, and an oxide of a metal element different from the alkali metal element,
The total number of lithium atoms, sodium atoms, and potassium atoms in the mixed layer is 0.3% or more and 30% or less with respect to the number of atoms of the metal element.   The photoelectric conversion element according to claim 1, wherein the oxide is zinc oxide or titanium oxide.   A solar cell comprising the photoelectric conversion element according to claim 1.   A solar cell module comprising the solar cell according to claim 3.

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