JP2013187501A - Photoelectric conversion element and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having a higher photoelectric conversion efficiency and a higher heat resistance, and capable of being encapsulated adequately.SOLUTION: The photoelectric conversion element comprises at least one pair of electrodes 101 and 105, and an active layer 103. The active layer 103 includes a high-molecule p-type semiconductor compound having an energy band gap of 1.0 eV or more and 1.8 eV or less, a fullerene compound and an aromatic compound. The boiling point of the aromatic compound is 140°C or more and 330°C or less under a standard condition (one atmospheric pressure and 25°C). The solubility of the fullerene compound to the aromatic compound is 1 wt.% or larger at 25°C. The concentration of the aromatic compound in the active layer 103 is 0.2 mg/cmor more and 20 mg/cmor less.

Description

  The present invention relates to a photoelectric conversion element and a solar cell module.

  Various methods for forming an active layer containing a p-type semiconductor compound and an n-type semiconductor compound have been studied in order to improve the performance of the photoelectric conversion element.

  Non-Patent Document 1 discloses a bulk heterojunction having an active layer containing a specific polymer p-type semiconductor compound (low band gap polymer) as a p-type semiconductor compound and PCBM which is a fullerene derivative as an n-type semiconductor compound in a mixed state. Type solar cells are described. As a method for producing a bulk heterojunction active layer, a solution in which a low band gap polymer and PCBM are dissolved (solvent: a mixed solvent of chlorobenzene and diiodooctane (DIO)) is applied by spin coating, and then heat treatment (80 ° C. , 30 minutes).

  Patent Document 1 describes a bulk heterojunction solar cell having an active layer containing P3HT as a p-type semiconductor compound and a bisindene adduct fullerene compound as an n-type semiconductor compound in a mixed state. Further, as a method for producing a bulk heterojunction active layer, a solution (solvent: mixed solvent of orthoxylene and tetralin) in which P3HT and a bisindene adduct fullerene compound are dissolved is applied by a spin coating method, followed by heat treatment (175 ° C., 30 Min)) is described.

International Publication No. 2010/021921

Journal of the American Chemical Society (2011), 133 (26), 1000062-10065.

  In general, the photoelectric conversion element is sealed with a sealing material such as a resin in order to avoid contact with water or oxygen in the air, but heating is often performed at the time of sealing. However, when the heat resistance of the photoelectric conversion element is low, the element deteriorates due to heating, and the photoelectric conversion efficiency decreases. If the heating temperature is lowered to prevent this, the sealing effect cannot be sufficiently achieved or the usable sealing material (resin or the like) is limited and the sealing effect is lowered.

  On the other hand, since a low band gap polymer generally has low heat resistance, when forming a bulk heterojunction type active layer using the low band gap polymer, it is usually not heat-treated or described in Non-Patent Document 1. The heat treatment is performed at a low temperature such as the above conditions (80 ° C., 30 minutes). Here, it is found that when a photoelectric conversion element having a bulk heterojunction type active layer containing a low band gap polymer as in Non-Patent Document 1 is subjected to a heat treatment at 130 ° C. for 60 minutes, the photoelectric conversion characteristics are significantly reduced. It was.

  Moreover, the photoelectric conversion element described in Patent Document 1 has not yet sufficient conversion efficiency, and a photoelectric conversion element having more excellent photoelectric conversion characteristics has been demanded.

  An object of this invention is to provide the photoelectric conversion element which has higher photoelectric conversion efficiency and higher heat resistance, and can be sealed enough.

  As a result of intensive studies to solve the above problems, the present inventors have found that when the active layer contains a specific aromatic compound within a specific concentration range, high photoelectric conversion efficiency and high heat resistance can be achieved at the same time. The present invention has been completed.

（式（１Ａ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１はヘテロ原子を有していてもよい炭化水素基を表す。）

（式（１Ｂ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｘ^１及びＸ^２は各々独立して酸素原子又は硫黄原子を表し、Ｒ^２〜Ｒ^５は各々独立して、水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭化水素基を表し、Ｒ^２〜Ｒ^５は隣接するもの同士で互いに結合して環を形成していてもよい。）
［３］太陽電池であることを特徴とする、［１］又は［２］に記載の光電変換素子。
［４］［３］に記載の光電変換素子を備えることを特徴とする、太陽電池モジュール。 That is, the gist of the present invention is as follows.
[1] Photoelectric conversion comprising at least a pair of electrodes and an active layer, wherein the active layer includes a polymer p-type semiconductor compound, a fullerene compound, and an aromatic compound having an energy band gap of 1.0 eV to 1.8 eV An element,
The boiling point of the aromatic compound is 140 ° C. or higher and 330 ° C. or lower in a standard state (1 atm, 25 ° C.)
The solubility of the fullerene compound in the aromatic compound is 1% by weight or more at 25 ° C .;
The photoelectric conversion element, wherein the concentration of the aromatic compound in the active layer is 0.2 mg / cm ³ or more and 20 mg / cm ³ or less.
[2] The polymer p-type semiconductor compound is a copolymer including a repeating unit represented by the following formula (1A) and a repeating unit represented by the formula (1B): [1] The photoelectric conversion element as described.

(In the formula (1A), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

(In Formula (1B), Q represents an atom selected from Group 14 elements of the periodic table, X ¹ and X ² each independently represent an oxygen atom or a sulfur atom, and R ^{2 to} R ⁵ each independently A hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ^{2 to} R ⁵ may be adjacent to each other to form a ring.
[3] The photoelectric conversion element according to [1] or [2], which is a solar cell.
[4] A solar cell module comprising the photoelectric conversion element according to [3].

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the photoelectric conversion element which has higher photoelectric conversion efficiency and higher heat resistance, and can fully be sealed.

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. The thin film absorption spectrum of an example of the p-type semiconductor compound which concerns on this invention is shown.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist.

<1. Photoelectric conversion element>
The photoelectric conversion element according to the present invention has at least a pair of electrodes and an active layer, and the active layer has a polymer p-type semiconductor compound having an energy band gap of 1.0 eV to 1.8 eV (hereinafter referred to as the present invention). May be referred to as such p-type semiconductor compounds), fullerene compounds (hereinafter sometimes referred to as fullerene compounds according to the present invention), and aromatic compounds (hereinafter sometimes referred to as aromatic compounds according to the present invention). It is a photoelectric conversion element containing.

  The photoelectric conversion element according to the present invention has an advantage of high photoelectric conversion efficiency. Moreover, since the heat resistance is also high, the photoelectric conversion element according to the present invention can be manufactured using a manufacturing process including a heating step. Furthermore, the photoelectric conversion element according to the present invention has an advantage of excellent durability and long-term storage stability. Although the details are unknown, the dispersion stability of the fullerene compound according to the present invention and the p-type semiconductor compound according to the present invention is improved by coexisting with the aromatic compound according to the present invention in the active layer. In addition, it is presumed that it is difficult to cause aggregation or separation, and as a result, a stable phase separation structure is formed in the active layer.

  As an example of the photoelectric conversion element according to the present invention, a photoelectric conversion element used in a general organic thin film solar cell is shown in FIG. In FIG. 1, the photoelectric conversion element 107 includes a substrate 106, an electrode 101, a hole extraction layer 102, an active layer 103, an electron extraction layer 104, and an electrode 105 in this order. The electrode 101 is preferably an electrode 101 suitable for collecting holes (hereinafter sometimes referred to as an anode), and the electrode 105 is preferably an electrode suitable for collecting electrons (hereinafter referred to as a cathode). (It may be described) is preferably used. Between these layers, another layer may exist so as not to affect the function of each layer described later. Further, the substrate 106, the hole extraction layer 102, and / or the electron extraction layer 104 may not exist depending on the use of the photoelectric conversion element 107. In the example of FIG. 1, the substrate 106 is disposed on the anode 101 side, but the substrate 106 may be disposed on the cathode 105 side.

<1.1 Active layer (103)>
The active layer 103 refers to a layer in which photoelectric conversion is performed, and includes a p-type semiconductor compound according to the present invention, an n-type semiconductor compound according to the present invention, and an aromatic compound according to the present invention. When the photoelectric conversion element 107 receives light, the light is absorbed by the active layer 103, electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is extracted from the electrodes 101 and 105.

  The active layer 103 may contain either an inorganic compound or an organic compound. The active layer 103 is preferably formed by a simple coating process, and the active layer 103 is more preferably an organic active layer made of an organic compound. In the following description, it is assumed that the active layer 103 is an organic active layer.

[1.1.1 Configuration of Active Layer]
The active layer 103 may be a thin film stacked active layer in which a p-type semiconductor layer and an n-type semiconductor layer are stacked. The active layer 103 may be a bulk heterojunction type active layer having a layer (i layer) in which a p-type semiconductor compound and an n-type semiconductor compound are mixed. In particular, the active layer 103 is preferably a bulk heterojunction type active layer.

  When the active layer 103 is a thin film stacked type active layer, the active layer 103 includes a p-type semiconductor layer including the p-type semiconductor compound according to the present invention and an n-type semiconductor layer including the fullerene compound according to the present invention. It has a laminated structure. Moreover, at least one of the p-type semiconductor layer and the n-type semiconductor layer contains the aromatic compound according to the present invention. Such a p-type semiconductor layer and an n-type semiconductor layer can be formed by any method including a coating method and an evaporation method (for example, a co-evaporation method).

  When the active layer 103 is a bulk heterojunction type active layer, the active layer 103 includes the p-type semiconductor compound according to the present invention, the n-type semiconductor compound according to the present invention, and the aromatic compound according to the present invention. It has i layer. The i layer has a structure in which a p-type semiconductor compound and an n-type semiconductor compound are phase-separated. Carrier separation occurs by light absorption at the phase interface in the i layer, and the generated carriers (holes and electrons) are transported to the electrode.

  There is no restriction | limiting in the film thickness of i layer. However, it is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 200 nm or less. When the film thickness of the i layer is 500 nm or less, it is preferable in that the series resistance is lowered. When the film thickness of the i layer is 5 nm or more, it is preferable in that more light can be absorbed.

  The i layer can be formed by any method including a coating method and a vapor deposition method (for example, a co-evaporation method). However, it is preferable to use the coating method because the i layer can be formed more easily. That is, a coating liquid containing a p-type semiconductor layer containing a p-type semiconductor compound according to the present invention, an n-type semiconductor layer containing a fullerene compound according to the present invention, and an aromatic compound according to the present invention is prepared. The i layer can be formed by applying a coating solution. As another method, after forming an i layer by applying a coating liquid containing a p-type semiconductor layer containing a p-type semiconductor compound according to the present invention and an n-type semiconductor layer containing a fullerene compound according to the present invention, The aromatic compound according to the present invention can be added to the i layer by exposing the i layer to the vapor of the aromatic compound according to the present invention.

  The coating liquid containing the p-type semiconductor compound according to the present invention and the fullerene compound according to the present invention may be prepared by preparing and mixing a solution containing the p-type semiconductor compound and a solution containing the fullerene compound, respectively. Alternatively, a p-type semiconductor compound and a fullerene compound may be dissolved in the solution. As an application method, any method can be used. For example, a slot die method or a spin coating method can be used.

  Examples of the solvent for the coating solution containing the p-type semiconductor compound, the coating solution containing the n-type semiconductor compound, and the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound include p-type semiconductor compounds and / or n-type. There is no particular limitation as long as it can dissolve the semiconductor compound uniformly. For example, the aromatic compound according to the present invention can be used as a solvent, and a mixture of the aromatic compound according to the present invention and another solvent can also be used as a solvent. When a mixture of the aromatic compound according to the present invention and another solvent is used as a solvent, the ratio of the aromatic compound according to the present invention to the solvent is usually 0.1% by weight or more, preferably 5% by weight or more. . On the other hand, it is usually 99% by weight or less, preferably 50% by weight or less.

  Examples of the solvent capable of uniformly dissolving the p-type semiconductor compound and / or the n-type semiconductor compound include aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane or decane; toluene, xylene, mesitylene, cyclohexylbenzene, Aromatic hydrocarbons such as chlorobenzene or orthodichlorobenzene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; lower alcohols such as methanol, ethanol or propanol; Aliphatic ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; ethyl acetate, butyl acetate or Esters such as methyl acid; halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene; ethers such as ethyl ether, tetrahydrofuran or dioxane; or amides such as dimethylformamide or dimethylacetamide .

  In particular, since fullerene compounds often have relatively low solubility, it is preferable to select a solvent having high solubility of the fullerene compound according to the present invention. When the preferable range of the solubility is raised, the solubility of the fullerene compound at 25 ° C. is usually 0.1% by weight or more, preferably 0.4% by weight or more, more preferably 0.7% by weight or more. It is preferable that the solubility of the fullerene compound is 0.1% by weight or more because the dispersion stability of the fullerene compound is increased and aggregation, sedimentation, separation, and the like are less likely to occur.

[1.1.2 Aromatic Compound According to the Present Invention]
The boiling point of the aromatic compound according to the present invention is 140 ° C. or higher, preferably 160 ° C. or higher, more preferably 180 ° C. or higher in the standard state (1 atm, 25 ° C.). On the other hand, it is 330 ° C. or lower, preferably 300 ° C. or lower, more preferably 250 ° C. or lower. It is preferable that the boiling point of the aromatic compound according to the present invention is in the above range in that volatilization from the active layer can be prevented.

  The solubility of the fullerene compound in the aromatic compound according to the present invention is 1.0% by weight or more, preferably 1.5% by weight or more, more preferably 2.0% by weight or more at 25 ° C. On the other hand, the upper limit is not particularly limited, but is usually 20% by weight or less, preferably 10% by weight or less. It is preferable that the solubility of the fullerene compound in the aromatic compound according to the present invention is in the above range at 25 ° C. in that the dispersion stability of the fullerene compound in the active layer is improved and aggregation, separation, and the like are less likely to occur. .

  Specifically, the solubility can be measured as follows. The powder of the fullerene compound according to the present invention and the aromatic compound according to the present invention are mixed at 40 ° C. The amount of the aromatic compound used at this time is the minimum amount at which it can be confirmed that the fullerene compound is dissolved at 40 ° C. Then, it cools to 25 degreeC, confirms that there is no precipitation of a compound, and makes the density | concentration of the solution at this time solubility. When precipitation is observed at 25 ° C., an aromatic compound is further added until dissolution, and the concentration of the solution at the time when dissolution is finally confirmed is taken as solubility.

The concentration of the aromatic compound according to the present invention in the active layer is 0.2 mg / cm ³ or more, preferably 0.3 mg / cm ³ or more. On the other hand, it is 20 mg / cm ³ or less, preferably 10 mg / cm ³ or less, more preferably 5 mg / cm ³ or less. By setting the concentration of the aromatic compound according to the present invention to 0.2 mg / cm ³ or more, it becomes possible to stabilize the phase separation and phase morphology in the active layer and to produce a highly efficient photoelectric conversion element. . By setting the concentration of the aromatic compound according to the present invention to 20 mg / cm ³ or less, problems with the upper electrode caused by evaporation of the aromatic compound according to the present invention can be prevented.

The concentration of the aromatic compound according to the present invention in the active layer can be measured as follows. That is, the element with the active layer exposed is cut to an appropriate size, and the aromatic compound according to the present invention is extracted using a solvent such as acetone. Then, the supernatant liquid after centrifugation is analyzed by gas chromatography (GC), and when the sensitivity in gas chromatography (GC) is low, a mass spectrometer is used to analyze the fragrance according to the present invention using an absolute calibration curve method. Quantify group compounds. Finally, the remaining amount of the aromatic compound according to the present invention is calculated as the weight per 1 cm ³ of the active layer film.

  Examples of the method for controlling the concentration of the aromatic compound in the active layer according to the present invention include the following methods. For example, when the active layer is formed by a coating method, the concentration of the aromatic compound according to the present invention can be controlled by the drying conditions after coating. Examples of drying conditions include temperature, atmosphere, degree of vacuum, and air volume.

  As a specific example, a case where the i layer is formed by a coating method will be described. When drying in a nitrogen atmosphere, the temperature during heating is usually 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and usually 170 ° C. or lower, preferably 145 It is below ℃. Also, the heating time is usually 1 minute or more, preferably 5 minutes or more, while usually 25 minutes or less, preferably 15 minutes or less. Specific heating means include a hot plate, an oven, and a dryer. The p-type semiconductor compound according to the present invention has a relatively narrow band gap and usually has low heat resistance. However, when the coating liquid contains the aromatic compound according to the present invention, heat drying can be performed at a relatively high temperature. This is because the aromatic compound according to the present invention in the coating solution improves the dispersion stability of the fullerene compound according to the present invention and the p-type semiconductor compound according to the present invention and makes it difficult to cause aggregation, separation, and the like. It is considered a thing.

When drying is performed under vacuum, the pressure is usually 10 ⁻⁸ MPa or more, preferably 10 ⁻⁷ MPa or more, and usually 0.1 MPa or less, preferably 0.01 MPa or less. The time for vacuum drying is usually 1 minute or more, preferably 10 minutes or more, while it is usually 20 hours or less, preferably 10 hours or less. Specific examples of the vacuum drying apparatus include a rotary pump type and a cryopump type.

  As another method, as described above, the aromatic compound according to the present invention can be added to the i layer by exposing the i layer to the vapor of the aromatic compound according to the present invention. In this case, the exposure time is usually 1 minute or longer, preferably 5 minutes or longer, while usually 120 minutes or shorter, preferably 60 minutes or shorter.

  As a further method, when the active layer is formed by a coating method, the concentration of the aromatic compound according to the present invention in the active layer is controlled by controlling the concentration of the aromatic compound according to the present invention in the coating solution. Can also be controlled. For example, by reducing the concentration of the aromatic compound according to the present invention in the coating solution, the concentration of the aromatic compound according to the present invention in the active layer can be decreased.

  The aromatic compound according to the present invention is not particularly limited as long as the above-described conditions are satisfied, but specific examples include aromatic hydrocarbon compounds and aromatic heterocyclic compounds. The carbon number of the aromatic compound according to the present invention is usually 2 or more, preferably 3 or more, more preferably 6 or more. On the other hand, it is usually 20 or less, preferably 15 or less, more preferably 12 or less.

  Examples of the aromatic hydrocarbon compound include halogenated aromatic hydrocarbon compounds such as orthodichlorobenzene; mesitylene, 1,2,4-trimethylbenzene, 1,2,3,5-tetramethylbenzene, cyclohexylbenzene, tetralin and the like. Non-halogen aromatic hydrocarbon compounds; and the like.

  Examples of aromatic heterocyclic compounds include pyrrole derivatives such as 2,5-dimethylpyrrole; thiophene derivatives such as 3-butylthiophene and 3-hexylthiophene; furan derivatives such as 2-butylfuran; 2,6-dimethylpyridine and the like. Examples thereof include pyridine derivatives.

  Of these, non-halogen aromatic hydrocarbon compounds such as mesitylene, 1,2,4-trimethylbenzene, 1,2,3,5-tetramethylbenzene, cyclohexylbenzene, and tetralin are preferable from the viewpoint of thermal stability.

  Furthermore, in order to achieve both high interaction with the semiconductor compound and solubility of the semiconductor compound, the aromatic hydrocarbon compound according to the present invention has both an aromatic ring and an aliphatic hydrocarbon group. Preferably it is. For example, the aromatic hydrocarbon compound according to the present invention is preferably benzene or condensed polycyclic hydrocarbon having two or more alkyl groups having 1 to 6 carbon atoms. Here, two or more alkyl groups may be bonded to each other. More preferred is benzene having two or more alkyl groups having 1 to 6 carbon atoms.

  The aromatic compound according to the present invention may be a mixture of two or more aromatic compounds.

  The viscosity of the aromatic compound according to the present invention is not particularly limited, but is usually 0.8 cP or more, preferably 1.0 cP or more in the standard state (25 ° C., 1 atm). On the other hand, it is usually 20 cP or less, preferably 10 cP or less. It is preferable that the viscosity of the aromatic compound according to the present invention is in the above-mentioned range because the aromatic compound according to the present invention does not adversely affect the layer adjacent to the active layer 103. The viscosity of the aromatic compound according to the present invention can be measured by a method described in known literature (Macromolecules (2009), 42 (13), 4661-4666.).

<1.2 p-type semiconductor compound>
The active layer 103 includes a polymer p-type semiconductor compound (p-type semiconductor compound according to the present invention) having an energy band gap of 1.0 eV or more and 1.8 eV or less. Since the p-type semiconductor compound according to the present invention has a relatively narrow energy band gap as compared with existing p-type semiconductor compounds, the p-type semiconductor compound according to the present invention is referred to as a low band gap polymer.

  Since the viscosity of the coating solution containing the polymer p-type semiconductor compound is relatively high, the active layer containing the p-type semiconductor compound according to the present invention can be easily produced by a coating method such as a slot die method or a spin coating method. Therefore, it is preferable that the p-type semiconductor compound according to the present invention is a polymer p-type semiconductor compound. In particular, when the active layer 103 is a bulk hetero active layer, the p-type semiconductor compound according to the present invention is a high molecular p-type semiconductor compound. This indicates that the p-type semiconductor compound and the n-type semiconductor compound are phase-separated. This is preferable because the structure is easy to obtain. Hereinafter, the polymer p-type semiconductor compound included in the active layer 103 will be described.

  The energy band gap of a p-type semiconductor compound refers to the lowest energy required to generate excitons. The energy band gap of the p-type semiconductor compound according to the present invention is 1.0 eV or more, preferably 1.1 eV or more, more preferably 1.2 eV or more, while 1.8 eV or less, preferably 1. 7 eV or less. A wide energy band gap is preferable in that the open circuit voltage Voc tends to increase. Moreover, a narrow energy band gap is preferable in that the wavelength region that can be absorbed increases and the short-circuit current density Jsc tends to increase.

  The p-type semiconductor compound according to the present invention is preferably used together with the fullerene compound which is an n-type semiconductor compound in terms of conversion efficiency. This is presumably because the energy band gap of the p-type semiconductor compound according to the present invention is relatively narrow, the LUMO energy level is also low, and charge transfer with the fullerene compound proceeds smoothly.

In this specification, the energy band gap of a p-type semiconductor compound shall be determined from the absorption edge of the thin film ultraviolet visible absorption spectrum (UV-vis spectrum) of a p-type semiconductor compound. Specifically, (ahν) ^1/2 is plotted against the light energy hν, and the intersection of the extrapolated line of the linear region near the absorption edge and the base line is defined as the energy band gap. Here, a is absorbance, h is Planck's constant, and ν is light frequency.

  The thin film ultraviolet visible absorption spectrum of the p-type semiconductor compound can be measured according to a method described in a known document (Adv. Funct. Mater. 2009, 19, 1913-1921). Specifically, a thin film of a p-type semiconductor compound is formed on a glass substrate by a coating method or a vapor deposition method, and an ultraviolet-visible absorption spectrum obtained by transmitting ultraviolet-visible light through the thin film is measured. The ultraviolet-visible absorption spectrum can be measured using, for example, a spectrophotometer (Ocean Optics, USB2000).

  The p-type semiconductor compound according to the present invention preferably has an absorption maximum wavelength in the wavelength range of 400 nm to 1000 nm in the thin film ultraviolet-visible absorption spectrum of 600 nm to 1000 nm. The absorption maximum wavelength being in this range means that the p-type semiconductor compound according to the present invention can absorb light having a longer wavelength, and the photoelectric conversion element using the p-type semiconductor compound according to the present invention. The conversion efficiency is expected to improve.

  The HOMO energy level of the p-type semiconductor compound according to the present invention is usually −6.0 eV or higher, preferably −5.7 eV or higher, more preferably −5.5 eV or higher. On the other hand, it is usually −4.4 eV or less, preferably −4.6 eV or less, more preferably −5.0 eV or less, and particularly preferably −5.2 eV or less. It is preferable that the HOMO energy level of the p-type semiconductor compound be in this range from the viewpoint that the open-circuit voltage of the photoelectric conversion element can be improved and the photoelectric conversion efficiency can be improved, and that it can be stable to the atmosphere.

  The LUMO energy level of the p-type semiconductor compound according to the present invention is usually −4.0 eV or more, preferably −3.9 eV or more. On the other hand, it is usually −3.3 eV or less, preferably −3.5 eV or less. When the LUMO energy level of the p-type semiconductor compound is −3.3 eV or less, the energy band gap is adjusted, and light energy having a long wavelength can be effectively absorbed, and the short-circuit current density can be improved. When the LUMO energy level of the p-type semiconductor compound is −4.0 eV or more, electron transfer to the n-type semiconductor is likely to occur, and the short-circuit current density can be improved.

In this specification, the HOMO energy level and the LUMO energy level of a p-type semiconductor compound refer to values measured and calculated as follows. That is, the ionization potential is measured for the p-type semiconductor compound sample formed on the ITO substrate. The ionization potential can be measured using, for example, an ionization potential measuring device (manufactured by OPTEL, PCR-101). From the obtained ionization potential and the energy band gap calculated as described above, the LUMO energy level and the HOMO energy level are calculated according to the following formulas (b1) and (b2).
LUMO energy level (eV) =
-(Ionization potential (eV) -energy band gap (eV)) (b1)
HOMO energy level (eV) = − (ionization potential (eV)) (b2)

  The p-type semiconductor compound according to the present invention is not particularly limited as long as it is a polymer p-type semiconductor compound having an energy band gap of 1.0 eV or more and 1.8 eV or less, but specifically, two or more types of monomer units are shared. Polymerized semiconducting polymers, eg, Nature Material, (2006) vol. 5, p. 328, a polythiophene-thienothiophene copolymer described in WO 2008/000664, a polythiophene-diketopyrrolopyrrole copolymer described in WO 2008/000664, Adv Mater, 2007, p. 4160, a polythiophene-thiazolothiazole copolymer, Nature Mat. vol. 6 (2007), p. 497, a polythiophene copolymer such as PCPDTBT, a copolymer containing imidothiophene described in International Publication No. 2011/028827, a copolymer of thienothiophene and benzodithiophene described in International Publication No. 2011/011545 A polymer etc. are mentioned. In addition, derivatives of these polymers and polymers that can be synthesized by combinations of the monomers listed here can also be used. These polymer and monomer substituents can be selected as appropriate in order to control solubility, crystallinity, film formability, HOMO level, LUMO level, and the like.

[1.2.1 Copolymer]
The p-type semiconductor compound according to the present invention is preferably a copolymer containing a repeating unit represented by the following formula (1A) and a repeating unit represented by the formula (1B). Such a copolymer is preferable in that it has a good balance between solubility and crystallinity. Such a copolymer is preferable in that it can absorb light having a longer wavelength and has high light absorption.

[1.2.1.1 Repeating unit represented by formula (1A)]

In formula (1A), R ¹ represents a hydrocarbon group which may have a hetero atom. Examples of R ¹ include an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an aromatic group which may have a substituent. It is preferable to use R ¹ as these groups because the copolymer tends to have excellent solubility in an organic solvent and can be advantageous in a coating film forming process. More preferably, R ¹ is an alkyl group which may have a substituent or an aromatic group which may have a substituent. The alkyl group may be linear, branched or cyclic, but is preferably a linear or branched alkyl group. A linear alkyl group is preferable in that the crystallinity of the polymer can be improved, so that mobility can be increased, and a branched alkyl group is preferable in that the solubility of the polymer can be improved. From these viewpoints, the alkyl group is more preferably an alkyl group having 1 to 12 carbon atoms, and particularly preferably an alkyl group having 4 to 12 carbon atoms. In addition, R ¹ is an aromatic group which may have a substituent. This indicates that the copolymer can absorb light having a longer wavelength, and the crystallinity of the polymer can be improved, so that mobility is increased. This is preferable in that it can be increased.

  In the present specification, as the substituent that may be included, as long as the copolymer including the repeating unit represented by the formula (1A) and the repeating unit represented by the formula (1B) has conductivity, Although there is no limitation, preferably a halogen atom, hydroxyl group, cyano group, amino group, carboxyl group, carbamoyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group, silyl group, boryl group, Examples include a cyano group, a nitro group, a nitrile group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, or an aromatic group. Adjacent substituents may be linked to form a ring.

  The carbon number of the alkyl group is usually 1 or more, preferably 3 or more, more preferably 4 or more, particularly preferably 6 or more, and usually 30 or less, preferably 25 or less, more preferably 20 or less. Examples of the alkyl group include a methyl group, ethyl group, n-propyl group, iso-propyl group, cyclopropyl group, n-butyl group, iso-butyl group, tert-butyl group, 3-methylbutyl group, cyclobutyl group, Pentyl group, cyclopentyl group, hexyl group, 2-ethylhexyl group, cyclohexyl group, heptyl group, cycloheptyl group, octyl group, cyclooctyl group, nonyl group, cyclononyl group, decyl group, cyclodecyl group, lauryl group, cyclolauryl group, Alternatively, 1- (2-ethyl) hexyl-3-ethylheptyl group and the like can be mentioned.

  Among them, n-propyl group, iso-propyl group, cyclopropyl group, n-butyl group, iso-butyl group, tert-butyl group, 3-methylbutyl group, cyclobutyl group, pentyl group, cyclopentyl group, hexyl group, 2 -Ethylhexyl group, cyclohexyl group, heptyl group, cycloheptyl group, octyl group, cyclooctyl group, nonyl group, cyclononyl group, decyl group, cyclodecyl group, lauryl group, cyclolauryl group, or 1- (2-ethyl) hexyl- A 3-ethylheptyl group is preferred, and a butyl group, pentyl group, hexyl group, 2-ethylhexyl group, nonyl group, decyl group, or 1- (2-ethyl) hexyl-3-ethylheptyl group is more preferred.

  The carbon number of the alkenyl group is usually 2 or more, preferably 3 or more, more preferably 4 or more, and is usually 20 or less, preferably 16 or less, more preferably 12 or less, and even more preferably 10 or less. Examples of such alkenyl groups include vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl. Group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group, icocenyl group or geranyl group. A propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group or a dodecenyl group, more preferably a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group An octenyl group, a nonenyl group or a decenyl group.

  The carbon number of the aromatic group is usually 2 or more, and is usually 60 or less, preferably 20 or less, more preferably 14 or less. Examples of such an aromatic group include an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, an indanyl group, an indenyl group, a fluorenyl group, an anthracenyl group, or an azulenyl group; a thienyl group, a furyl group, a pyridyl group, and a pyrimidyl group. , Aromatic heterocyclic groups such as thiazolyl group, oxazolyl group, triazolyl group, benzothienyl group, benzofuryl group, dibenzothienyl group, benzothiazolyl group, benzoxazolyl group or benzotriazolyl group. Of these, a phenyl group, a naphthyl group, a thienyl group, a pyridyl group, a pyrimidyl group, a thiazolyl group, or an oxazolyl group is preferable.

  A represents an atom selected from Group 16 elements of the Periodic Table. In this specification, the periodic table means an IUPAC 2005 recommended version. Specific examples include an oxygen atom, a sulfur atom, and a selenium atom. Of these, an oxygen atom or a sulfur atom is preferable. An oxygen atom is preferable in that the open circuit voltage (Voc) of the photoelectric conversion element is improved, and a sulfur atom is preferable in that an intermolecular interaction between the copolymers is improved.

[1.2.1.2 Repeating unit represented by formula (1B)]

  In formula (1B), Q represents an atom selected from Group 14 elements of the periodic table. Specifically, a carbon atom, a silicon atom, a germanium atom, or a tin atom is mentioned. Among these, a carbon atom, a silicon atom or a germanium atom is preferable, and a carbon atom or a silicon atom is more preferable. A carbon atom is preferable in terms of crystallinity, and a silicon atom is preferable in terms of solubility.

X ¹ and X ² each independently represent an oxygen atom or a sulfur atom. X ¹ and X ² are preferably the same, and X ¹ and X ² are more preferably sulfur atoms. It is preferable that X ¹ and X ² are sulfur atoms from the viewpoint of increasing resonance energy, spreading the main chain conjugated system, and absorbing light having a longer wavelength.

R ^{2 to} R ⁵ are not particularly limited as long as they have conductivity, but each independently represents a hydrocarbon group which may have a hydrogen atom, a halogen atom, or a hetero atom. The hydrocarbon group which may have a hetero atom includes an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an aromatic which may have a substituent. Represents a group. As the alkyl group, alkenyl group, and aromatic group, the same groups as those described above for R ¹ can be used. Examples of the substituent that the alkyl group, alkenyl group, and aromatic group may have include the same substituents as those described above for R ¹ . R ^{2 to} R ⁵ may be bonded together to form a ring.

Especially, it is preferable that at least one of R ⁴ and R ^{5 is} an alkyl group or an aromatic group which may have a substituent, and both R ⁴ and R ⁵ may have a substituent. More preferably, it is a good alkyl group or aromatic group. It is preferable that the alkyl group is linear because the mobility can be increased by improving the crystallinity of the polymer, and that the alkyl group is branched is because the solubility of the polymer is improved. This is preferable in that film formation by a coating process is easy.

It is preferable that at least one of R ⁴ and R ⁵ is an alkyl group in that the copolymer can absorb light having a longer wavelength. In this respect, at least one of R ⁴ and R ⁵ is preferably an alkyl group having 1 to 20 carbon atoms, and particularly preferably an alkyl group having 6 to 20 carbon atoms. In addition, it is preferable that at least one of R ⁴ and R ⁵ is an aromatic group in that the mobility tends to increase because the interaction between molecules is improved by the interaction between π electrons. 1B) is preferable in that the condensed ring structure represented by 1B) tends to be improved in stability.

From the viewpoint of improving the durability of the copolymer by increasing the steric hindrance around the atom Q, R ⁴ and R ⁵ may have an alkyl group which may have a substituent or a substituent. It is preferably a good alkenyl group or an aromatic group which may have a substituent.

Further, it is preferable that at least one of R ² and R ³ is a halogen atom in terms of improving the heat resistance, weather resistance, chemical resistance, water / oil repellency, etc. of the copolymer.

(Composition of copolymer)
The ratio of the repeating unit represented by the formula (1A) in the copolymer is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 30. % Or more. On the other hand, it is usually 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, and still more preferably 70% or less.

  The ratio of the repeating unit represented by the formula (1B) in the copolymer is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 30. % Or more. On the other hand, it is usually 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, and still more preferably 70% or less.

  The ratio of the repeating unit represented by the formula (1B) to the repeating unit represented by the formula (1A) in the copolymer is not particularly limited, but is usually 0.01 or more, preferably 0.1 or more, More preferably, it is 0.5 or more. On the other hand, it is usually 100 or less, preferably 10 or less, more preferably 2 or less.

  The arrangement state of the repeating units (1A) and (1B) may be alternating, block, or random. Preferably, they are arranged alternately.

  Moreover, you may contain another repeating unit in the range which does not impair the effect of this invention. Examples thereof include aromatic heterocycles such as thienyl group and thizazolyl group.

Although the preferable specific example of a copolymer is shown below, the p semiconductor compound which concerns on this invention is not restricted to the following illustrations. _{C 4 H 9, C 6 H} 13, C 8 H 17, and _C 12 _{H 25,} respectively, represent a linear alkyl group. Bu, Hex, and Oct represent an n-butyl group, an n-hexyl group, and an n-octyl group, respectively. When the copolymer of the present invention includes a plurality of repeating units, the ratio between the plurality of repeating units included is arbitrary.

[1.2.1.1 Copolymer Production Method]
There is no particular limitation on the production method of the copolymer containing the repeating unit represented by the formula (1A) and the repeating unit represented by the formula (1B). For example, the compound represented by the following formula (2A) and (2B) The method of superposing | polymerizing the compound represented with presence of a suitable catalyst if necessary may be mentioned.

In formulas (2A) and (2B), R ^{1 to} R ⁵ , X ^{1 to} X ² , A, and Q are the same as those described above.

Y ¹ and Y ² are each independently a halogen atom, an alkylstannyl group, an alkylsulfo group, an arylsulfo group, an arylalkylsulfo group, a boric acid ester residue, a sulfonium methyl group, a phosphonium methyl group, a phosphonate methyl group, It represents a monohalogenated methyl group, a boric acid residue (—B (OH) ₂ ), a formyl group, an alkenyl group or an alkynyl group. From the viewpoints of synthesis and ease of reaction of the compounds represented by formulas (2A) and (2B), X and Y are each independently a halogen atom, an alkylstannyl group, a borate ester residue, Or it is preferable that it is a boric acid residue (-B (OH) ₂ ).

As the reaction method used for the polymerization of the compounds represented by (2A) and (2B), a Suzuki-Miyaura cross-coupling reaction method, a Stille coupling reaction method, a Yamamoto coupling reaction method, a Grignard reaction method, a Heck reaction method, Examples include Sonogashira reaction method, reaction method using an oxidizing agent such as FeCl ₃ , method using electrochemical oxidation reaction, reaction method by decomposition of an intermediate compound having an appropriate leaving group, and the like. Among these, the Suzuki-Miyaura coupling reaction method, the Stille coupling reaction method, the Yamamoto coupling reaction method, and the Grignard reaction method are preferable in terms of easy structure control. In particular, the Suzuki-Miyaura cross-coupling reaction method, the Stille coupling reaction method, and the Grignard reaction method are preferable from the viewpoint of easy availability of materials and easy reaction operation. These reactions are described in "Cross Coupling-Fundamentals and Industrial Applications (CMC Publishing)", "Transition Metal Catalyzed Reactions for Organic Synthesis (edited by Jiro Jiro: edited by Organic Synthetic Chemistry Association)", "For Organic Synthesis" The reaction can be carried out according to a method described in known literature such as “catalytic reaction 103 (Teijiro Hatakeyama: Tokyo Kagaku Dojin)”.

[1.2.2 Other p-type semiconductor compounds]
The active layer 103 may contain a p-type semiconductor compound different from the p-type semiconductor compound according to the present invention. However, the amount is in a range that does not significantly impair the effect of the p-type semiconductor compound according to the present invention. Specifically, among the p-type semiconductor compounds contained in the active layer 103, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more is the p-type semiconductor compound according to the present invention. .

  Another p-type semiconductor compound that can be included in the active layer 103 is not particularly limited, but specifically, a conjugated polymer semiconductor such as polythiophene, polyfluorene, polyphenylene vinylene, polythienylene vinylene, polyacetylene, polyaniline, or the like; an alkyl group And polymer p-type semiconductor compounds having an energy band gap larger than 1.8 eV, such as polymer semiconductors such as oligothiophene substituted with other substituents. Examples of further p-type semiconductor compounds that can be included in the active layer 103 include condensed aromatic hydrocarbons such as naphthacene, pentacene, and pyrene; oligothiophenes including four or more thiophene rings such as α-sexithiophene; Rings, benzene rings, fluorene rings, naphthalene rings, anthracene rings, thiazole rings, thiadiazole rings, benzothiazole rings in total 4 or more; phthalocyanine compounds and metal complexes thereof, and porphyrin compounds such as tetrabenzoporphyrins and metal complexes thereof And low molecular organic semiconductor compounds such as macrocyclic compounds. For example, as another p-type semiconductor compound that can be included in the active layer 103, compounds described in International Publication No. 2011/016430 can be given.

  When using a low molecular organic semiconductor compound, as described in International Publication No. 2011/016430, a low molecular organic semiconductor compound is converted into a low molecular organic semiconductor compound after coating a low molecular organic semiconductor compound precursor. An active layer 103 containing may be formed.

<1.3 Fullerene compounds>
The active layer 103 includes the fullerene compound according to the present invention. The active layer 103 may include one type of fullerene compound or may include a plurality of types of fullerene compounds. The fullerene compound according to the present invention is fullerene or a fullerene derivative. Here, the fullerene is a carbon cluster having a closed shell structure, and the carbon number of the fullerene is not particularly limited as long as it is usually an even number of 60 or more and 130 or less. 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 nonmetal atom, or an atomic group composed of these may be included in the fullerene cage.

  In order for the fullerene compound to be applicable to a coating method, the fullerene compound itself may be applied in a liquid state, or the fullerene compound may be applied as a solution with high solubility in some solvent. preferable. As a preferable range of solubility, the solubility in toluene at 25 ° C. is usually 0.1% by weight or more, preferably 0.4% by weight or more, more preferably 0.7% by weight or more. It is preferable that the solubility of the fullerene compound is 0.1% by weight or more because the dispersion stability of the fullerene compound is increased and aggregation, sedimentation, separation, and the like are less likely to occur.

In particular, the fullerene compound according to the present invention preferably has a partial structure represented by the following general formulas (n1), (n2), (n3), and (n4).

In the formula, FLN represents fullerene. 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 in (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 ⁶ and — (CH ₂ ) _L are respectively 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 ¹⁰ ) (R ¹¹ ) -N (R ¹² ) -C with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. (R ¹³ ) (R ¹⁴ ) — are bonded to form a 5-membered ring. In the general formula (n3), —C (R ¹⁵ ) (R ¹⁶ ) —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. ^{17) (R 18)} - is bonded to form a 6-membered ring. In the general formula (n4), —C (R ¹⁹ ) (R ²⁰ ) — is bonded 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.

R ⁶ in the general formula (n1) 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. Is an aromatic group which may have

  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 even more preferably a methyl group or an ethyl group. .

  The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 6 carbon atoms, and particularly preferably a methoxy group or an ethoxy 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. More preferred are groups or thienyl groups.

  The substituent that the alkyl group, alkoxy group and aromatic group may have is preferably a halogen atom or a silyl group. 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.

R ^{7 to} R ⁹ in the general formula (n1) each independently represent a substituent, and have 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 the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, or an 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. Or a thienyl group is more preferable. 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 3 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 still more 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.

R ^{10 to} R ¹⁴ in the general formula (n2) are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 14 carbon atoms, or an optionally substituted aromatic group. 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 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 or a pyridyl group, and even more preferably a phenyl 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.

  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, 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, but are preferably the same.

Ar ¹ in the general formula (n3) 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 as a substituent which may have, an amino group which may be substituted with a fluorine atom, a chlorine atom, a hydroxyl group, a cyano group, a silyl group, a boryl group or an alkyl group, having 1 to 14 carbon atoms An alkyl group, an alkoxy group having 1 to 14 carbon atoms, an alkylcarbonyl group having 2 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 An alkynyl group, an ester group having 2 to 14 carbon atoms, an arylcarbonyl group having 3 to 20 carbon atoms, an arylthio group having 2 to 20 carbon atoms, an aryloxy group having 2 to 20 carbon atoms, and 6 or more carbon atoms An aromatic hydrocarbon group having 20 or less or a heterocyclic group having 2 to 20 carbon atoms is preferable, a fluorine atom, an alkyl group having 1 to 14 carbon atoms, 1 or less carbon atoms 1 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 1 to 2 or more fluorine atoms.

  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.

  When it has a substituent, the number is not limited, but it is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less. When there are a plurality of substituents, the types may be different, but are preferably the same.

R ^{15 to} R ¹⁸ in the general formula (n3) each independently have a hydrogen atom, an alkyl group which may have a substituent, an amino group which may have a substituent, or a substituent. It is an optionally substituted alkoxy group or an optionally substituted alkylthio group. R ¹⁵ or R ¹⁶ may form a ring with either of R ¹⁷ or R ¹⁸ . The structure in the case of forming a ring can be represented by, for example, the general formula (n5) which is a bicyclo structure in which an aromatic group is condensed.

F in the general formula (n5) is the same as c, and X ³ is an oxygen atom, a sulfur atom, an amino group, an alkylene group or an arylene group. The alkylene group preferably has 1 to 2 carbon atoms. The arylene group preferably has 5 to 12 carbon atoms, such as 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 formula (n5) is particularly preferably a structure represented by the following formula (n6) or formula (n7). Of these, Ar ¹ is particularly preferably a phenyl group which may have a substituent.

R ^{19 to} R ²⁰ in the general formula (n4) each independently have a hydrogen atom, an alkoxycarbonyl group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group that may be used.

  The alkoxy group in 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, a methoxy group, an ethoxy group 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 are more preferable, 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 of the alkoxycarbonyl group is preferably an alkoxy group having 1 to 14 carbon atoms or a fluorinated alkoxy group, more preferably a hydrocarbon group having 1 to 14 carbon atoms, a methoxy group, an ethoxy group, or an 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-butoxy group The 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. 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.

As the structure of the general formula (n4), R ¹⁹ and R ²⁰ are preferably both alkoxycarbonyl groups, R ¹⁹ and R ²⁰ are both aromatic groups, or R ¹⁹ is an aromatic group and R ²⁰ is 3- (alkoxycarbonyl) propyl group.

  The lowest unoccupied molecular orbital (LUMO) energy level of the n-type semiconductor compound is not particularly limited. For example, the value with respect to the vacuum level calculated by the cyclic voltammogram measurement method is usually −3.85 eV or more, preferably − 3. 80 eV or more. In order to efficiently move electrons from the electron donor layer (p-type semiconductor layer) to the electron acceptor layer (n-type semiconductor layer), the minimum vacancy of the materials used for each electron donor layer and electron acceptor layer is required. The relative relationship of the orbit (LUMO) is important. Specifically, the LUMO of the material of the electron donor layer is higher than the LUMO of the material of the electron acceptor layer by a predetermined energy, in other words, the electron affinity of the electron acceptor is higher than the electron affinity of the electron donor. It is preferable that the energy is larger by a predetermined energy. Since the open circuit voltage (Voc) is determined by the difference between the highest occupied orbit (HOMO) of the electron donor layer material and the LUMO of the electron acceptor layer material, increasing the LUMO of the electron acceptor increases the Voc. Tend. On the other hand, the LUMO energy level 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. Lowering the LUMO of the electron acceptor tends to cause electron migration and increase the short-circuit current (Jsc).

  As a method for calculating the LUMO energy level of an n-type semiconductor compound, 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. Specifically, it can measure by the method as described in well-known literature (International Publication 2011/016430), for example.

  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. The HOMO energy level of the n-type semiconductor compound is preferably −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 ³ cm ² / Vs or less, preferably 1.0 × 10 ² cm ² / Vs or less, and more preferably 5.0 × 10 ¹ cm ² / Vs or less. When the electron mobility of the compound is 1.0 × 10 ⁻⁶ cm ² / Vs or more, the effects of improving the electron diffusion rate, the short-circuit current, the conversion efficiency, etc. of the photoelectric conversion element tend to increase. Therefore, it is preferable. An example of a method for measuring electron mobility is the FET method, which can be performed by a method described in a known document (Japanese Patent Application Laid-Open No. 2010-045186).

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

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

  Synthesis of a fullerene compound 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 and WO 2009/086212.

  Synthesis of fullerene compounds 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 and J. Org. Org. Chem. It can be carried out according to the description of known documents such as 1995, 60, 532-538.

  As commercially available fullerene compounds, for example, PCBM (manufactured by Frontier Carbon Co.), PCBNB (Frontier Carbon Co., Ltd.) and the like can be suitably used.

[1.3.2 Other n-type semiconductor compounds]
The active layer 103 may contain an n-type semiconductor compound different from the fullerene compound according to the present invention in an amount that does not significantly inhibit the effect of the fullerene compound according to the present invention. Specifically, among the n semiconductor compounds contained in the active layer 103, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more is the fullerene compound according to the present invention.

  Another n-type semiconductor compound that can be included in the active layer 103 is not particularly limited, but specifically, a quinolinol derivative metal complex represented by 8-hydroxyquinoline aluminum; naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid Condensed ring tetracarboxylic acid diimides such as diimide; perylene diimide derivatives, terpyridine metal complexes, tropolone metal complexes, flavonol metal complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, oxa Diazole derivatives, thiadiazole derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoli Derivatives, bipyridine derivatives, borane derivatives, anthracene, pyrene, total fluoride condensed polycyclic aromatic hydrocarbons such as naphthacene or pentacene; single-walled carbon nanotubes, n-type polymer semiconductor compounds, and the like.

[1.3.2.1 N-alkyl substituted perylene diimide derivatives]
The N-alkyl-substituted perylene diimide derivative that can be included in the active layer 103 is not particularly limited, and specifically, International Publication No. 2008/063609, International Publication No. 2009/115513, International Publication No. 2009 / Examples include compounds described in 098250, WO2009 / 000756 and WO2009 / 091670. N-alkyl-substituted perylene diimide derivatives are preferable in that they have high electron mobility and absorption in the visible region, and thus contribute to both charge transport and power generation.

[1.3.2.2 Naphthalenetetracarboxylic acid diimide]
The naphthalenetetracarboxylic acid diimide that can be contained in the active layer 103 is not particularly limited, and specifically, described in International Publication No. 2008/063609, International Publication No. 2007/16250, and International Publication No. 2009/000756. The compound currently made is mentioned. Naphthalenetetracarboxylic acid diimide is preferable because it has high electron mobility, high solubility, and excellent coating properties.

[1.3.2.3 n-type polymer semiconductor compound]
The n-type polymer semiconductor compound that can be included in the active layer 103 is not particularly limited, but condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide and perylene tetracarboxylic acid diimide, perylene diimide derivatives, and benzimidazole derivatives. , Benzoxazole derivatives, thiazole derivatives, benzothiazole derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, bipyridine derivatives and borane derivatives as constituent units N-type polymer semiconductor compound to be used.

  Among them, polymers having at least one of borane derivatives, thiazole derivatives, benzothiazole derivatives, benzothiadiazole derivatives, N-alkyl-substituted naphthalenetetracarboxylic acid diimides and N-alkyl-substituted perylene diimide derivatives as constituent units are provided. Preferably, an n-type polymer semiconductor compound having at least one of N-alkyl-substituted perylene diimide derivative and N-alkyl-substituted naphthalenetetracarboxylic acid diimide as a constituent unit is more preferable. You may contain 1 type, or 2 or more types of these compounds.

  Specific examples thereof 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. Since n-type polymer semiconductor compounds have absorption in the visible range, they contribute to power generation, have high viscosity, and are excellent in terms of coating properties.

<1.4 Buffer layer (102, 104)>
The photoelectric conversion element 107 according to this embodiment preferably further includes one or more buffer layers in addition to the pair of electrodes (101, 105) and the active layer 103 disposed therebetween. The buffer layer can be classified into an electron extraction layer 104 and a hole extraction layer 102, and can be provided between the active layer 103 and the electrodes (101, 105), respectively. By providing the buffer layer, there are advantages that the mobility of electrons and holes between the active layer and the electrode is increased, and that a short circuit between the electrodes can be prevented.

  The electron extraction layer 104 and the hole extraction layer 102 are disposed so as to sandwich the active layer 103 between a pair of electrodes (101, 105). That is, when the photoelectric conversion element 107 according to this embodiment includes both the electron extraction layer 104 and the hole extraction layer 102, the electrode 101, the hole extraction layer 102, the active layer 103, the electron extraction layer 104, and the electrode 105 Arranged in order. The stacking order of the electron extraction layer 104 and the hole extraction layer 102 may be reversed, or at least one of the electron extraction layer 104 and the hole extraction layer 102 may be composed of a plurality of different films. .

[1.4.1 Electron extraction layer (104)]
The material of the electron extraction layer 104 is not particularly limited as long as the efficiency of extracting electrons from the active layer 103 containing the p-type semiconductor compound and the n-type semiconductor compound to the electrode 105 can be improved. Specifically, an inorganic compound or an organic compound is mentioned.

[1.4.1.1 Inorganic compounds]
Examples of the inorganic compound used as the material of the electron extraction layer 104 include salts of alkali metals such as Li, Na, K, and Cs; n-type semiconductor metal oxides such as titanium oxide (TiOx) and zinc oxide (ZnO); Is desirable.

  As the alkali metal salt, a fluoride salt such as LiF, NaF, KF or CsF is preferable. Although the operation mechanism of such a material is unknown, it is conceivable to reduce the work function of the cathode 105 in combination with an electron extraction electrode (cathode 105) such as Al and increase the voltage applied to the inside of the photoelectric conversion element. It is done.

  Examples of the metal oxide include zinc oxide, titanium oxide, tin oxide, aluminum oxide, silicon oxide, cerium oxide, lead oxide, zirconium oxide, and gallium oxide. Of these, zinc oxide, titanium oxide or tin oxide is preferable. Moreover, a metal oxide may be used individually by 1 type, or may use 2 or more types together. The metal oxide desirably has a porous (porous) structure.

  Further, the metal oxide is preferably in the form of particles, and the average primary particle size is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, while usually 100 nm or less, preferably 60 nm or less, more Preferably it is 40 nm or less. When the average primary particle size is 5 nm or more, the primary particles of the metal oxide hardly aggregate and a metal oxide having a suitable average secondary particle size can be obtained. Further, it is preferable that the average primary particle size 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 to 100 nm (sometimes referred to as metal oxide nanoparticles) include Nanozinc 60 (Honjo Chemical Co., Ltd.), FINEX-30, FINEX-50. (Manufactured by Sakai Chemical Industry Co., Ltd.).

  Further, the metal oxide particles may be surface-treated with a surface treatment agent to facilitate dispersion. 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) Acetic acid or carboxylic acid compound such as 6-hydroxyhexanoic acid; Organic phosphorus compound such as lauryl ether phosphoric acid or trioctylphosphine; Vine such as polyimine, polyester, polyamide, polyurethane, polyurea Over compounds; and the like. In addition, a surface treating agent may be used individually by 1 type, or may use 2 or more types together.

[1.4.1.2 Organic compounds]
Specific examples of the organic compound used as the material of the electron extraction layer 104 include bathocuproin (BCP), bathophenanthrene (Bphen), (8-hydroxyquinolinato) aluminum (Alq3), boron compound, oxadiazole compound, Double between an atom selected from group 16 such as a benzimidazole compound, naphthalenetetracarboxylic anhydride (NTCDA), perylenetetracarboxylic anhydride (PTCDA), or a phosphine oxide compound or phosphine sulfide compound, and a phosphorus atom. Phosphine compounds having a bond; and the like.

  Preferably, a phosphine having a double bond between an atom selected from the group 16 substituted with an aryl group such as a phosphine oxide compound substituted with an aryl group or a phosphine sulfide compound substituted with an aryl group and a phosphorus atom More preferably a triarylphosphine oxide compound, a triarylphosphine sulfide compound, an aromatic hydrocarbon compound having two or more diarylphosphine oxide units, an aromatic hydrocarbon compound having two or more diarylphosphine sulfide units, Alternatively, it is an aromatic hydrocarbon compound having two or more diarylphosphine oxide units. The aryl group may be substituted with a fluorine atom or a fluorine atom-substituted alkyl group such as a perfluoroalkyl group. Further, these materials may be doped with an alkali metal or an alkaline earth metal.

  The LUMO energy level of the material of the electron extraction layer 104 is not particularly limited, but is usually −5.0 eV or more, preferably −4.5 eV or more. On the other hand, it is usually −1.9 eV or less, preferably −2.0 eV or less. Although it is somewhat affected by the work function of the electrode used and the LUMO energy level of the n-type semiconductor, since the LUMO energy level of the material of the electron extraction layer 104 is within this range, electrons generated in the active layer are selectively used. In addition, since the loss of the open circuit voltage is eliminated, it leads to high photoelectric conversion efficiency.

  The HOMO energy level of the material of the electron extraction layer 104 is not particularly limited, but is usually −9.0 eV or more, preferably −8.0 eV or more. On the other hand, it is usually −5.5 eV or less, preferably −6.0 eV or less. When the HOMO energy level of the material of the electron extraction layer 104 is −5.5 eV or less, it is preferable in that the movement of holes can be prevented.

  As a method for calculating the HOMO and LUMO energy levels of the material of the electron extraction layer 104, a cyclic voltammogram measurement method can be given. For example, the measurement can be carried out with reference to a method described in a known document (International Publication No. 2011/016430).

  When the material of the electron extraction layer 104 is an organic compound, the glass transition temperature (hereinafter also referred to as Tg) of this compound by the DSC method is not particularly limited but is not observed or 55 ° C. The above is preferable. That the glass transition temperature by DSC method is not observed means that there is no glass transition temperature. Specifically, the determination is made based on the presence or absence of a glass transition temperature of 400 ° C. or lower. A material in which the glass transition temperature by the DSC method is not observed is preferable in that it has high thermal stability.

  Among compounds having a glass transition temperature by DSC of 55 ° C. or higher, compounds having a glass transition temperature of 65 ° C. or higher, more preferably 80 ° C. or higher, more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. desirable. On the other hand, the upper limit of the glass transition temperature is not particularly limited, but is usually 400 ° C. or lower, preferably 350 ° C. or lower, more preferably 300 ° C. or lower. The material of the electron extraction layer 104 is preferably a material whose glass transition temperature by DSC method is not observed to be 30 ° C. or higher and lower than 55 ° C.

  The glass transition temperature in the present specification is a temperature at which local molecular motion is initiated by thermal energy in an amorphous solid of a compound, and is defined as a point at which specific heat changes. When the temperature rises further than Tg, the solid structure changes and crystallization occurs (the temperature at this time is defined as the crystallization temperature (Tc)). When the temperature rises further, it generally melts at the melting point (Tm) and changes to a liquid state. However, these phase transitions may not be observed due to molecular decomposition or sublimation at high temperatures. What is necessary is just to measure a glass transition temperature by a well-known method, for example, DSC method is mentioned.

  The DSC method is a thermophysical property measurement method (differential scanning calorimetry method) defined in JIS K-0129 “General Rules for Thermal Analysis”. The glass transition temperature is a temperature at which molecular motion starts from a glass state, and can be measured by DSC as a temperature at which specific heat changes. In order to determine the glass transition temperature more clearly, it is desirable to measure after rapidly cooling a sample once heated to a temperature higher than the glass transition temperature. For example, the measurement can be carried out by a method described in a known document (International Publication No. 2011/016430).

  When the glass transition temperature of the compound used for the electron extraction layer is 55 ° C. or higher, the structure of this compound is difficult to change against external stress such as applied electric field, flowing current, stress due to bending or temperature change. It is preferable in terms of durability. Furthermore, since there is a tendency that the crystallization of the thin film of the compound does not proceed easily, the stability of the electron extraction layer is improved by making the compound difficult to change between the amorphous state and the crystalline state in the operating temperature range. Therefore, it is preferable in terms of durability. This effect becomes more prominent as the glass transition temperature of the material is higher.

  The thickness of the electron extraction layer 104 is not particularly limited, but is usually 0.01 nm or more, preferably 0.1 nm or more, more preferably 0.5 nm or more. On the other hand, it is usually 40 nm or less, preferably 20 nm or less. When the film thickness of the electron extraction layer 104 is 0.01 nm or more, it functions as a buffer material. When the film thickness of the electron extraction layer 104 is 40 nm or less, electrons are easily extracted, and photoelectric conversion is performed. Efficiency is improved. There is no limitation on the method for forming the electron extraction layer 104. For example, when a material having sublimation property is used, it can be formed by a vacuum deposition method or the like. Further, for example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as spin coating or inkjet.

[1.4.2 Hole Extraction Layer (102)]
The material of the hole extraction layer 102 is not particularly limited as long as it is a material capable of improving the efficiency of extracting holes from the active layer 103 to the anode 101. Specifically, a conductive polymer in which polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline, or the like is doped with sulfonic acid and / or iodine, etc .; a polythiophene derivative having a sulfonyl group as a substituent, or a conductive organic material such as arylamine Compound; the above-mentioned p-type semiconductor compound; and the like.

  Among them, a conductive polymer doped with sulfonic acid is preferable, and poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: PSS) in which a polythiophene derivative is doped with polystyrene sulfonic acid is more preferable. A thin film of metal such as gold, indium, silver or palladium can also be used, and a metal oxide such as molybdenum trioxide is particularly preferable. Furthermore, a thin film of metal or the like may be formed alone or in combination with the above organic material.

  The thickness of the hole extraction layer 102 is not particularly limited, but is usually 2 nm or more. On the other hand, it is usually 40 nm or less, preferably 20 nm or less. When the film thickness of the hole extraction layer 102 is 2 nm or more, it functions as a buffer material. When the film thickness of the hole extraction layer 102 is 40 nm or less, holes are easily extracted, Conversion efficiency is improved.

  There is no limitation on the method of forming the hole extraction layer 102. For example, when a material having sublimation property is used, it can be formed by a vacuum deposition method or the like. Further, for example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as spin coating or inkjet. In the case of a coating method, the coating solution may further contain a surfactant. By using the surfactant, generation of dents due to adhesion of fine bubbles, foreign matters, etc., uneven coating in the drying process, and the like are suppressed.

  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. In addition, 1 type may be used for surfactant and it may use 2 or more types together by arbitrary combinations and a ratio.

<1.5 Electrode (101, 105)>
The electrodes (101, 105) have a function of collecting holes and electrons generated by light absorption. Any one of the pair of electrodes may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. In addition, it is preferable that the transparent electrode has a solar ray transmittance of 70% or more in order to allow light to reach the active layer through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

[1.5.1 Anode (101)]
The electrode 101 (anode) suitable for collecting holes is generally an electrode made of a conductive material having a work function larger than that of the cathode and having a function of smoothly extracting holes generated in the active layer 103. . Examples of the material of the anode 101 include conductive oxides such as nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide, and zinc oxide; Examples thereof include metals such as gold, platinum, silver, chromium, and cobalt or alloys thereof.

  These substances are preferable because they have a large work function, and more preferably, 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, the work function of the conductive polymer material is high, so that it is suitable for cathodes such as Al and Mg, even if it is not a material with a high work function as described above. Metals can also be widely used.

  A PEDOT / PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material doped with iodine or the like in polypyrrole or polyaniline can also be used as the anode material. When the anode 101 is a transparent electrode, it is preferable to use a conductive metal oxide having translucency such as ITO, zinc oxide or tin oxide, and ITO is particularly preferable.

  The film thickness of the anode 101 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. When the film thickness of the anode 101 is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the anode 101 is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. it can. When used for a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the anode 101 is not particularly limited, but is usually 1Ω / □ or more, on the other hand, 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less.

  Examples of the formation method of the anode 101 include a vacuum film formation method such as vapor deposition or sputtering, or a method of forming a film by applying an ink containing nanoparticles or a precursor.

[1.5.2 Cathode]
The electrode 105 (cathode) suitable for collecting electrons is generally an electrode made of a conductive material having a work function smaller than that of the anode and having a function of smoothly extracting electrons generated in the active layer 103. In the example of FIG. 1, the cathode 105 is adjacent to the electron extraction layer 104.

  Examples of the material of the cathode 105 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 And inorganic salts such as cesium fluoride and metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferred because they have a low work function.

  Similarly to the anode 101, a material having a large work function suitable for the anode 101 can be used for the cathode 105 by using an n-type semiconductor such as titania having conductivity for the electron extraction layer 104. From the viewpoint of electrode protection, the anode 101 material is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium, or an alloy using these metals.

  The film thickness of the cathode 105 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or less, 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. In the case of a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance. When the film thickness of the cathode 105 is 10 nm or more, sheet resistance is suppressed, and when the film thickness of the cathode 105 is 10 μm or less, light can be efficiently converted into electricity without a decrease in light transmittance. it can.

  The sheet resistance of the cathode 105 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.

  Examples of the method of forming the cathode 105 include a vacuum film formation method such as vapor deposition or sputtering, or a method of forming a film by applying an ink containing nanoparticles or a precursor.

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

<1.6 Substrate (106)>
The photoelectric conversion element 107 according to the present invention has a substrate 106 that is usually a support. That is, the electrodes 101 and 105, the active layer 103, and the buffer layers 102 and 104 are formed on the substrate.

  The material of the substrate (substrate material) is arbitrary as long as the effect is not significantly impaired. Preferable examples of the substrate material include inorganic materials such as quartz, glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin Film, polyolefin such as vinyl chloride or polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, or epoxy resin; paper materials such as paper or synthetic paper; stainless steel, titanium Alternatively, composite materials such as those obtained by coating or laminating a surface of a metal such as aluminum to provide insulation, and the like. Examples of the glass include soda glass, blue plate glass, and alkali-free glass. As for the glass material, alkali-free glass is preferred because it is better that there are fewer ions eluted from the glass.

  There is no restriction | limiting in the shape of the board | substrate 106, For example, shapes, such as a board, a film, a sheet | seat, can be used. There is no limitation on the film thickness of the substrate 106. However, it is usually 5 μm or more, particularly 20 μm or more, and on the other hand, it is usually preferably 20 mm or less, particularly preferably 10 mm or less. It is preferable that the thickness of the substrate is 5 μm or more because the possibility that the strength of the semiconductor device is insufficient is reduced. It is preferable that the film thickness of the substrate is 20 mm or less because the cost is suppressed and the weight is not increased. When the substrate is glass, the film thickness 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. When the film thickness of the glass substrate is 0.01 mm or more, the mechanical strength increases and it is difficult to break, which is preferable. When the film thickness of the glass substrate is 0.5 cm or less, it is preferable because the weight does not increase.

<1.7 Manufacturing Method of Photoelectric Conversion Element>
The manufacturing method of a photoelectric conversion element is not specifically limited. By sequentially laminating each layer by the method described above for each layer, the photoelectric conversion element according to the present invention can be manufactured. For example, a method for manufacturing a photoelectric conversion element as an example includes a step of forming one electrode, a step of forming the active layer 103, and a step of forming the other electrode. In the case of manufacturing the photoelectric conversion element 107 illustrated in FIG. 1, the electrode 101, the hole extraction layer 102, the organic active layer 103, the electron extraction layer 104, and the electrode 105 may be sequentially stacked over the substrate 106.

(Heat treatment)
A photoelectric conversion element obtained by laminating at least a pair of electrodes and the active layer 103 is further usually 50 ° C. or higher, preferably 80 ° C. or higher, and usually 250 ° C. or lower, preferably 200 ° C. or lower, more preferably 180 ° C. It is preferable to heat in the following temperature range. In this specification, this process is called a post-annealing process. It is preferable to set the temperature of the post-annealing process to 50 ° C. or higher because adhesion between the layers can be improved and conversion efficiency can be improved. It is preferable to set the temperature in the post-annealing process to 300 ° C. or lower because the possibility that the organic compound in the active layer is thermally decomposed is reduced. Heating may be performed stepwise within the above temperature range. The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and usually 3 hours or shorter, preferably 1 hour or shorter.

  The post annealing process is preferably terminated when the open circuit voltage, the short circuit current, and the fill factor, which are parameters of the solar cell performance, reach a constant value. Further, it is preferable that the annealing treatment be performed under normal pressure and in an inert gas atmosphere.

  By improving the adhesion between the layers by the post annealing process, self-organization of the active layer is promoted, and an effect of improving the conversion efficiency can be obtained. As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be put in a heating atmosphere such as an oven. Further, the heating may be a batch method or a continuous method.

<2. Solar cell>
The photoelectric conversion element 107 according to the present embodiment 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 the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.

[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 weather resistant protective film 1 is located on the outermost layer of the thin film solar cell 14, the surface covering material of the thin film solar cell 14 such as weather resistance, heat resistance, transparency, water repellency, stain resistance and / or mechanical strength is provided. It is preferable to have a property suitable for the above and to maintain it for a long period of time in outdoor exposure.

  Moreover, the weather-resistant protective film 1 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light 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 include polyethylene resin, polypropylene resin, cyclic polyolefin resin, AS (acrylonitrile-styrene) resin, ABS (acrylonitrile-butadiene-styrene) resin, polyvinyl chloride resin, fluorine resin, polyethylene terephthalate, 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, silicone 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.

  Moreover, you may perform surface treatment, such as a corona treatment and / or a plasma treatment, for the weather-resistant protective film 1 in order to improve the adhesiveness with another film.

  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. It is possible to protect the power generation and keep the power generation capacity high.

  As the degree of the ability to suppress the transmission of ultraviolet rays required for the ultraviolet cut film 2, the transmittance of ultraviolet rays (for example, wavelength 300 nm) is preferably 50% or less, and the lower limit is not limited. Further, the ultraviolet cut film 2 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light 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, the ultraviolet cut film 2 has a high softness | flexibility, its adhesiveness with an adjacent film is favorable, and what can cut water vapor | steam and oxygen is preferable.

  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, salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ones can be used. In addition, a ultraviolet absorber may use 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  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 resistance required for the gas barrier film 3 is, for example, preferably that the water vapor permeability per unit area (1 m ² ) per day is usually 1 × 10 ⁻¹ g / m ² / day or less, There is no limit on the lower limit.

The degree of oxygen permeability required for the gas barrier film 3 is, for example, that the oxygen permeability per unit area (1 m ² ) is usually 1 × 10 ⁻¹ cc / m ² / day / atm or less. Is preferred, and there is no limit to the lower limit.

  Further, the gas barrier film 3 is preferably one that transmits visible light from the viewpoint of not preventing the light absorption of the solar cell element 6. 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 the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.

[2.4 Getter material film (4)]
The getter material film 4 is a film that absorbs moisture and / or oxygen. By covering the solar cell element 6 with the getter material film 4, the solar cell element 6 and the like can be protected from moisture and / or oxygen, and the power generation capability can be kept high.

Here, unlike the gas barrier film 3 described above, the getter material film 4 does not prevent moisture permeation but absorbs moisture. By using a film that absorbs moisture, when the solar cell element 6 is covered with the gas barrier film 3 or the like, the getter material film 4 captures moisture that slightly enters the space formed by the gas barrier films 3 and 9, 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.

  Further, when the solar cell element 6 is covered with the gas barrier films 3 and 9 or the like by the getter material film 4 absorbing oxygen, the oxygen that slightly enters the space formed by the gas barrier films 3 and 9 is obtained as the getter material. The film 4 can capture and eliminate the influence of oxygen on the solar cell element 6.

  Furthermore, the getter material film 4 is preferably one that 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 moisture and / or 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, Fe, Mn, Zn, and inorganic salts such as sulfates, chlorides, and 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 obtained by bonding a fluororesin film on both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. .

[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.

  In addition, the sealing material 5 is preferably one that 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.

  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.

  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 or a thermoplastic resin composition and an active energy ray curable resin composition can be mentioned. 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-based resin composition, etc., depending on the main chain, branched chain, terminal chemical modification of each polymer, adjustment of molecular weight, additives, etc., thermosetting, thermoplastic and active energy ray curable, etc. The characteristics are expressed.

  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.

  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 according to the present invention, for example, the photoelectric conversion element 107.

  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, and thus a highly safe solar cell can be obtained and can be applied to a curved surface, so that it can be used for more applications. Since it is thin and light, it is preferable in terms of distribution such as transportation and storage. Furthermore, since it is in the form of a film, it can be manufactured in a roll-to-roll manner, and the cost can be greatly reduced. 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]
Although there is no restriction | limiting in the manufacturing method of the thin film solar cell 14 of this embodiment, For example, as a solar cell manufacturing method of the form of FIG. 2, after producing the laminated body shown by FIG. Is mentioned. Since the solar cell element of the present invention is excellent in heat resistance, it is preferable in that deterioration due to the laminate sealing step is 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, thermal laminate, etc. are mentioned. Among them, the laminating method using a photo-curing adhesive having a proven record in organic EL device sealing, the hot melt laminate having a proven record in solar cells, and the thermal laminate are preferable. It is more preferable at the point which can be used.

  The heating temperature in the laminate sealing step is usually 90 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher, and is usually 180 ° C or lower, preferably 170 ° C or lower, more preferably 150 ° C or lower. The p-type semiconductor compound according to the present invention having a narrow band gap is usually low in heat resistance, but has a relatively high temperature because the active layer contains the aromatic compound according to the present invention at a predetermined concentration as described above. In this case, the active layer can be prevented from deteriorating even if the laminate sealing is performed. By performing laminate sealing at a higher temperature, the photoelectric conversion element can be more reliably protected from oxygen and moisture.

  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. By setting the pressure within this range, sealing can be reliably performed, and the sealing materials 5 and 7 from the end can be prevented from protruding or reduced in film thickness due to over-pressurization, thereby ensuring dimensional stability.

  In addition, what connected two or more solar cell elements 6 in series or in parallel can be manufactured similarly to the above.

[2.13 Applications]
There is no restriction | limiting in the use of the solar cell of this invention, especially the thin film solar cell 14 mentioned above, It can use for arbitrary uses. Examples of fields to which the thin film solar cell of the present invention is applied include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, solar cells for airplanes, solar cells for spacecraft. Batteries, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

  The solar cell of the present invention, particularly a thin film solar cell, may be used as it is, or may be used as a solar cell module by installing a solar cell 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 base material 12 is 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 solar cell element 6. Examples of the material for forming the substrate 12 include inorganic materials such as glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluorine. Organic materials such as resin, vinyl chloride, polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate and polynorbornene; paper materials such as paper and synthetic paper; metals such as stainless steel, titanium and aluminum; Examples thereof include composite materials such as those obtained by coating or laminating a surface of a metal such as stainless steel, titanium, and aluminum to impart insulation.

  In addition, 1 type may be used for the material of a base material, 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 Hereinafter, the present invention will be described more specifically with reference to examples of the present invention. However, the present invention is not limited to the following examples without departing from the gist thereof.

(Measurement method of weight average molecular weight and number average molecular weight)
The weight average molecular weight and number average molecular weight in terms of polystyrene were determined using gel permeation chromatography (GPC).

Gel permeation chromatography (GPC) measurement was performed under the following conditions.
Column: Shim-pack GPC-803 (manufactured by Shimadzu Corporation, inner diameter 8.0 mm, length 30 cm) and Shim-pack GPC-804 (manufactured by Shimadzu Corporation, inner diameter 8.0 mm, length 30 cm) (one each) (In series connection)
Pump: LC-10AT (manufactured by Shimadzu Corporation)
Oven: CTO-10A (manufactured by Shimadzu Corporation)
Detector: differential refractive index detector (manufactured by Shimadzu Corporation: RID-10A) and UV-vis detector (manufactured by Shimadzu Corporation: SPD-10A)
Sample: 5 μL of 1 mg sample dissolved in 3 mL of tetrahydrofuran (THF)
Mobile phase: Tetrahydrofuran Flow rate: 1.0 mL / min
Analysis: LC-Solution (manufactured by Shimadzu Corporation)

(Elemental analysis measurement)
After wet decomposition of the sample, the amounts of palladium (Pd) and tin (Sn) in the sample were determined by analyzing the amounts of palladium (Pd) and tin (Sn) in the decomposition solution with an ICP mass spectrometer. . In addition, the sample is burned with a sample combustion apparatus (QF-02 type, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the combustion gas is absorbed in an alkaline absorbent containing a reducing agent, so that bromine ions (Br ⁻ ) in the absorbent are absorbed. And iodine ions (I ⁻ ) were analyzed by an ICP mass spectrometer, and the amounts of bromine (Br) and iodine (I) in the sample were determined. As the ICP mass spectrometer, a 7500ce type manufactured by Agilent Technologies was used, and the analysis was performed by a calibration curve method.

(Method for measuring thin film absorption spectrum of p-type semiconductor compound)
The thin film absorption spectrum of the p-type semiconductor compound was measured as follows. That is, by spin-coating a p-type semiconductor compound solution (0.5 wt%, solvent: toluene) (0.15 mL) on a glass substrate using a spin coater, and drying at 60 ° C. to remove the solvent. A p-type semiconductor compound film (film thickness: 120 nm) was formed. The p-type semiconductor compound film was irradiated with ultraviolet-visible light, and the ultraviolet-visible absorption spectrum of the transmitted light was measured with a spectrophotometer (Ocean Optics, USB2000).

(Method for measuring energy band gap of p-type semiconductor compounds)
The energy band gap (eV) of the p-type semiconductor compound was determined from the absorption edge of the UV-vis spectrum measured as described above. Specifically, (ahν) ^1/2 was plotted against the light energy hν, and the intersection of the extrapolated line of the linear region in the vicinity of the absorption edge and the base line was defined as the energy band gap. Here, a is absorbance, h is Planck's constant, and ν is light frequency.

(Method for measuring ionization potential of p-type semiconductor compound)
A p-type semiconductor compound film is prepared by preparing a toluene solution (1.3% by weight) of a p-type semiconductor compound, spin-coating 0.5 mL of the solution on the ITO substrate, drying at 60 ° C., and removing the solvent. (Film thickness: 100 nm) was formed. The ionization potential of this p-type semiconductor compound film was measured using an ionization potential measuring device (manufactured by OPTEL, PCR-101).

(Method for calculating the orbital energy level of p-type semiconductor compounds)
The LUMO energy level and HOMO energy level of the p-type semiconductor compound were calculated according to the following formulas (b1) and (b2) using the results of the energy band gap measurement and the ionization potential measurement.
LUMO energy level (eV) =
-(Ionization potential (eV) -energy band gap (eV)) (b1)
HOMO energy level (eV) = − (ionization potential (eV)) (b2)

(Solubility of fullerene compound G1 in aromatic compounds)
The solubility of the fullerene compound G1 with respect to various aromatic compounds was measured as follows. That is, the powder of fullerene compound G1 and each aromatic compound solution were mixed at 40 ° C. The amount of the various aromatic compounds used at this time was the minimum amount at which it was confirmed that the fullerene compound G1 was dissolved at 40 ° C. Then, it cooled to 25 degreeC and it confirmed that there was no precipitation and the density | concentration of the fullerene compound G1 at this time was made into solubility. When precipitation was observed at 25 ° C., each aromatic compound was further added until the precipitate was dissolved, and the concentration of the fullerene compound G1 when dissolution was finally confirmed was taken as solubility.

(Evaluation of photoelectric conversion element)
A 4 mm square metal mask is attached to the photoelectric conversion element, a solar simulator with an air mass (AM) of 1.5 G and an irradiance of 100 mW / cm ² is used as an irradiation light source, and an ITO electrode and a source meter (type 2400, manufactured by Keithley) The current-voltage characteristic between the aluminum electrode was measured. From the measurement results, 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.

Here, the open circuit voltage Voc is a voltage value when the current value = 0 (mA / cm ² ), and the short circuit current density Jsc is a current density when the voltage value = 0 (V). The form factor FF is a factor representing the internal resistance, and is represented by the following expression when the maximum output 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

(Measurement of aromatic compound concentration in active layer)
The substrate on which the electron extraction layer and the active layer were formed was cut by the method described in Example 1 or Comparative Example 1 to produce a strip-shaped piece having a length of 2.5 cm and a width of 0.5 cm. This section was placed in a vial containing acetone (1 mL). After shaking this vial well by hand, ultrasonic treatment (Honda Electronics, ULTRASONIC MULTI CLEANER W-113) was used for 15 minutes of ultrasonic treatment (28, 45, 100 kHz repeated for 5 seconds each). went. Then, the extract was centrifuged (10 minutes, 2000 rpm) using a centrifuge (manufactured by Kubota Seisakusho, table top cooling centrifuge KUBOTA 2800), and the supernatant was separated.

For Comparative Example 1, the obtained supernatant was analyzed by gas chromatography (manufactured by Agilent Technologies, model number HP6890), and the amount of aromatic compound (tetralin amount) was quantified by the absolute calibration method.
Column: DB-1HT (inner diameter 0.25 mm, length 15 m)
Carrier gas: He
Detector: Hydrogen flame ionization detector

In the case of Example 1 having a smaller amount of aromatic compound, the obtained supernatant was analyzed with a gas chromatograph / mass spectrometer (manufactured by Agilent Technologies, model number 6890N / 5978), and the aromatic compound was analyzed by an absolute calibration curve method. The amount (tetralin amount) was quantified.
Column: DB-1HT (inner diameter 0.25 mm, length 15 m)
Detector: MSD (EI) Selected ion monitoring mode Selected ion: m / z 104
Carrier gas: He
Analysis: Absolute calibration curve method

From the quantification result, the amount of aromatic compound (tetralin amount) per 1 cm ^{3 of} the active layer film was calculated. The film thickness of the active layer was measured with a stylus type surface shape measuring instrument (manufactured by ULVAC, model number Dektak 150).

<Synthesis Example 1: Synthesis of imidothiophene monomer 1>

  Thiophenedicarboxylic acid (Compound E1, 5.3 g, 30.7 mmol) and acetic anhydride (100 mL) were added to a 500 mL eggplant flask and heated at 140 ° C. for 6 hours. The solvent was removed by distillation under reduced pressure, and 1H, 3H-thieno [3,4-c] furan-1,3-dione (Compound E2, 3.5 g) was obtained by recrystallization from toluene.

  Compound E2 (3.57 g, 0.023 mol) was dissolved in dehydrated N, N-dimethylformamide (35 mL) in a 100 mL eggplant flask under nitrogen. Subsequently, n-octylamine (4.2 mL, 0.025 mol) was added in an ice bath, followed by heating at 140 ° C. for 2 hours. After allowing to cool, the reaction solution is mixed with water, and the precipitated skin-colored powder is collected by filtration and washed with cold methanol to give 4-[[1-octylamino] carbonyl] -3-thiophenecarboxylic acid (Compound E3 , 5.3 g).

  Compound E3 (5.27 g, 18.6 mmol) and thionyl chloride (18 mL) were added to a 100 mL eggplant flask and heated in a bath set at 72 ° C. for 3 hours. After allowing to cool, the reaction solution was dropped into a 1N aqueous sodium hydroxide solution, and the precipitated brown powder was collected by filtration. By washing with cold methanol and drying, 5-octyl-4H-thieno [3,4-c] pyrrole-4,6 (5H) -dione (compound E4, 4.55 g) was obtained (yield). 91%).

  Compound E4 (2.65 g, 10 mmol) was dissolved in trifluoroacetic acid (50 mL) and concentrated sulfuric acid (15 mL) in a 200 mL eggplant flask under nitrogen. In the ice bath, N-bromosuccinimide (5.33 g, 30 mmol) was further added and stirred until dissolved, then the ice bath was removed, the reaction solution was allowed to rise to room temperature, and stirred for another 20 hours. After the reaction solution was quenched by mixing with ice water, the product was extracted with chloroform, and the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (developing solvent: hexane / chloroform = 2/1 → 1/1) and suspended and washed with hexane to obtain imidothiophene monomer 1 (1,3-dibromo). -5-octyl-4H-thieno [3,4-c] pyrrole-4,6- (5H) -dione, 2.58 g) was obtained (61% yield).

<Synthesis Example 2: Synthesis of Dithienosilole Monomer 1>

  Into a 50 mL multi-necked flask was placed 4,4′-bis (2-ethylhexyl) -5,5-dibromo-dithieno [3,2-b: 2 ′, 3′-d] silole (Compound E11, 0.1 g). Using a vacuum pump and a dryer, the nitrogen was sufficiently replaced. After adding dehydrated tetrahydrofuran (5 mL) and cooling the system in a dry ice-acetone bath, an n-butyllithium hexane solution (1.6 M, 0.28 mL) was added and stirred for 15 minutes. Trimethyltin chloride (105 mg) was then added, and the reaction mixture was allowed to rise to room temperature and stirred for 2 hours. The reaction solution was quenched by adding water, and the product was extracted with hexane, dried using sodium sulfate, and the solvent was removed by distillation under reduced pressure, whereby dithienosilole monomer 1 (4,4′-bis ( 2-ethylhexyl) -5,5-bis (trimethyltin) -dithieno [3,2-b: 2 ′, 3′-d] silole, 125 mg) was obtained as a green oil.

<Synthesis Example 3: Synthesis of Copolymer A>

  In a 50 mL eggplant flask under nitrogen, imidothiophene monomer 1 obtained in Synthesis Example 1 (187 mg, 0.443 mmol), dithienosilole monomer 1 obtained in Synthesis Example 2 (340 mg, 0.443 mmol), tetrakis (triphenyl) Phosphine) palladium (valent 0) (15 mg, 0.013 mmol), copper (II) oxide (35 mg, 0.443 mmol), toluene (6.75 mL) and DMF (1.62 mL) were added, and the mixture was stirred at 100 ° C. for 20 hours. did. Then, as a terminal treatment, bromobenzene (0.1 mL) was added and heated and stirred for 3 hours. Further, trimethyl (phenyl) tin (0.1 mL) was added and heated and stirred for 3 hours, and then the reaction solution was diluted 5 times with toluene. Diluted and dropped into 400 mL of methanol. The precipitated copolymer was collected by filtration and purified by column chromatography to obtain the desired copolymer A. Specifically, using a JAL908-C60 apparatus (manufactured by Nihon Analytical Industrial Co., Ltd.) with JAIGEL-3H (40φ) and 2H (40φ) attached in series, using chloroform as a developing solution, under a flow rate of 14 mL / min. Then, the copolymer (50 to 100 mg) collected by filtration was filled with a chloroform solution (10 mL) and subjected to preparative purification.

The weight average molecular weight, number average molecular weight and molecular weight distribution (PDI) of the fractionated copolymer A were measured as described above, and were 1.6 × 10 ⁵ , 6.1 × 10 ⁴ and 2.7, respectively. It was. When elemental analysis of the copolymer A was performed as described above, the respective element amounts were Br: 73 ppm, Pd: 40 ppm, and Sn: 153 ppm.

(Results of measuring characteristics of p-type semiconductor compounds)
According to the above-mentioned method, the thin film absorption spectrum of the polymer A obtained by the synthesis example 1 and P3HT (Rieke) was measured. The results are shown in FIG.

  From FIG. 4, it was found that, unlike P3HT, polymer A, which is a p-type semiconductor compound according to the present invention, has the strongest absorption maximum wavelength at 400 nm or more at 600 nm or more and 1000 nm or less. This suggests that polymer A has a relatively narrow energy band gap and is susceptible to charge separation and carrier transfer. In addition, since the polymer A has a relatively high light absorption in the long wavelength region, the photoelectric conversion element using the polymer A can more effectively use the long wavelength light.

  Moreover, according to the above-mentioned method, the energy band gap, the HOMO energy level, and the LUMO energy level of the polymer A and P3HT were measured and calculated. The results are shown in Table 1.

  As shown in Table 1, polymer A has a narrower energy band gap than P3HT and has a lower LUMO energy level.

<Synthesis Example 4: Synthesis of fullerene compound G1>

C ₆₀ (Ind) (fullerene compound G1) was synthesized with reference to a patent document (International Publication No. 2008/018931). The fullerene compound G1 was fractionated and purified by GPC from a mixture of compounds having one or more indandiyl groups. By mass spectrometry (APCI method, negative), m / z: 836 [M ⁻ ] corresponding to the mass of the fullerene compound G1 was detected.

(Solubility measurement result of fullerene compound G1)
Table 2 shows the solubility of the fullerene compound G1 in various aromatic compounds.

  As shown in Table 1, it can be seen that tetralin, which is an aromatic compound according to the present invention, can dissolve the fullerene compound G1, which is a fullerene compound according to the present invention, more efficiently than toluene and orthoxylene. Therefore, by combining the aromatic compound according to the present invention with the fullerene compound according to the present invention, it is possible to form an active layer in which the fullerene compound hardly precipitates, and it is possible to easily form the active layer by a coating method. That is, it can be seen that the photoelectric conversion element of the present invention is a photoelectric conversion element suitable for manufacturing by a coating process.

<Example 1>
(Preparation of active layer coating solution Ink1)
The polymer A obtained in Synthesis Example 3 as a p-type semiconductor compound and the fullerene compound G1 obtained in Synthesis Example 4 as an n-type semiconductor compound are mixed so that the weight ratio is 1: 2, and the mixture is 1 It was dissolved in a mixed solvent of orthoxylene and tetralin (volume ratio 4: 1) in a nitrogen atmosphere to a concentration of 2% by weight. This solution was stirred and mixed on a hot stirrer at a temperature of 80 ° C. for 1 hour. The solution after stirring and mixing was filtered through a 1 μm polytetrafluoroethylene (PTFE) filter to obtain an active layer coating solution Ink1.

(Preparation of photoelectric conversion element 1)
A glass substrate (manufactured by Geomatic Co., Ltd.) on which an indium tin oxide (ITO) transparent conductive film was patterned was subjected to ultrasonic cleaning with acetone, followed by ultrasonic cleaning with isopropanol, and then dried with nitrogen blowing.

  Next, a dispersion obtained by diluting zinc oxide (ZnO) nanoparticle dispersion (catalog number 721107, manufactured by Adolrich) five times with propylene glycol 1-monomethyl ether 2-acetate (PGMEA, manufactured by Tokyo Chemical Industry Co., Ltd.) Prepared. 1 mL of the obtained dispersion was dropped onto the substrate washed as described above, and then applied by spin coating (5000 rpm). The substrate after application was heated on the hot plate at 150 ° C. for 10 minutes in the air. The thickness of the electron extraction layer thus formed was about 100 nm.

  The substrate on which the electron extraction layer is formed is brought into a glove box, heated at 150 ° C. for 3 minutes in a nitrogen atmosphere, and after cooling, the active layer coating liquid Ink1 (0.12 mL) prepared as described above is cooled at a speed of 80 rpm. An active layer having a thickness of 195 to 220 nm was formed by spin coating. Further, in the same glove box, heat treatment was performed at 140 ° C. for 10 minutes using a hot plate to complete the formation of the active layer.

Further, 3.0 nm of molybdenum trioxide (MoO ₃ ) as a hole extraction layer and 100 nm of silver as an electrode layer were sequentially formed by resistance heating vacuum deposition to produce a 5 mm square photoelectric conversion element. .

(Measurement of aromatic compound concentration)
About the produced photoelectric conversion element, tetralin residual amount per 1 cm ³ of the active layer film was measured as described above. Table 3 shows the measurement results. In this example, it was confirmed that no tetralin remained on the substrate, the ITO electrode, and the electron extraction layer. In addition, it has been confirmed that the polymer A and the fullerene compound G1 used in producing the active layer coating solution Ink1 do not contain tetralin.

(Evaluation of photoelectric conversion element)
About the photoelectric conversion element produced in this way, the current-voltage characteristic was measured as described above, and the open circuit voltage Voc (V), the short circuit current density Jsc (mA / cm ² ), the form factor FF, the photoelectric conversion efficiency PCE (% ) Was calculated. These measured values are hereinafter referred to as initial values. The results are shown in Table 3.

In addition, in order to evaluate the heat resistance of the device, the produced photoelectric conversion device was heat-treated on a hot plate set at 130 ° C. for 60 minutes, and the current-voltage characteristics were measured in the same manner after the substrate was cooled, and the open-circuit voltage Voc (V). , Short circuit current density Jsc (mA / cm ² ), form factor FF, photoelectric conversion efficiency PCE (%) were calculated. These measured values are hereinafter referred to as post-heat treatment values. The results are shown in Table 3.

<Comparative Example 1>
A photoelectric conversion element was produced in the same manner as in Example 1 except that the heat treatment at 140 ° C. was not performed for 10 minutes after spin coating the active layer coating solution Ink1. About the produced photoelectric conversion element, the tetralin residual amount was measured similarly to Example 1, and the current-voltage characteristic was measured. The results are shown in Table 3.

  As shown in Table 3, the photoelectric conversion elements according to the examples not only have high photoelectric conversion efficiency immediately after the element fabrication, but also have a high heat resistance with little deterioration in characteristics after heat treatment at high temperatures. Is shown. On the other hand, it can be seen that in Comparative Example 1 in which the aromatic compound remained at a specific concentration or more, there was a decrease in characteristics after heat treatment at high temperature. Thus, it can be seen that the photoelectric conversion element of the present invention has high photoelectric conversion efficiency and heat resistance.

  Thus, it was found that high photoelectric conversion efficiency can be obtained by combining a fullerene compound having a relatively low LUMO energy level and a p-type polymer semiconductor compound having a relatively narrow energy band gap. Further, a photoelectric conversion element having relatively high heat resistance even when a p-type polymer semiconductor compound having a relatively narrow energy band gap is used by further adding an aromatic compound having a specific concentration to the active layer Was found to be obtained.

DESCRIPTION OF SYMBOLS 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 101 Anode 102 Hole extraction Layer 103 Active layer 104 Electron extraction layer 105 Cathode 106 Substrate 107 Photoelectric conversion element

Claims (4)

A photoelectric conversion element comprising at least a pair of electrodes and an active layer, and the active layer includes a polymer p-type semiconductor compound, a fullerene compound, and an aromatic compound having an energy band gap of 1.0 eV to 1.8 eV. And
The boiling point of the aromatic compound is 140 ° C. or higher and 330 ° C. or lower in a standard state (1 atm, 25 ° C.)
The solubility of the fullerene compound in the aromatic compound is 1% by weight or more at 25 ° C .;
The photoelectric conversion element, wherein the concentration of the aromatic compound in the active layer is 0.2 mg / cm ³ or more and 20 mg / cm ³ or less. 2. The photoelectric device according to claim 1, wherein the polymer p-type semiconductor compound is a copolymer including a repeating unit represented by the following formula (1A) and a repeating unit represented by the formula (1B). Conversion element.

(In the formula (1A), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

(In Formula (1B), Q represents an atom selected from Group 14 elements of the periodic table, X ¹ and X ² each independently represent an oxygen atom or a sulfur atom, and R ^{2 to} R ⁵ each independently A hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ^{2 to} R ⁵ may be adjacent to each other to form a ring.   It is a solar cell, The photoelectric conversion element of Claim 1 or 2 characterized by the above-mentioned.   A solar cell module comprising the photoelectric conversion element according to claim 3.

Images