WO2012111811A1

WO2012111811A1 - Organic photoelectric conversion element and solar cell

Info

Publication number: WO2012111811A1
Application number: PCT/JP2012/053836
Authority: WO
Inventors: 大久保　康; 貴宗服部
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2011-02-18
Filing date: 2012-02-17
Publication date: 2012-08-23
Also published as: JPWO2012111811A1; JP5838975B2

Abstract

[Problem] The purpose of the present invention is to provide: an organic photoelectric conversion element having high photoelectric conversion efficiency and excellent durability; and a solar cell equipped with the organic photoelectric conversion element. [Solution] An organic photoelectric conversion element which comprises a transparent first electrode, a photoelectric conversion layer comprising a p-type organic semiconductor material and an n-type organic semiconductor material and a second electrode which are arranged in this order on a transparent substrate, and which is characterized in that the photoelectric conversion layer contains a compound having a partial structure represented by general formula (1) or (1') as the p-type organic semiconductor material. (In the formulae, X₁'s independently represent -S-, -O- or -NR₂-; Y₁'s independently represent -CR₃= or -N=; R₁-R₃ independently represent a hydrogen atom, an alkyl group which may have a substituent, a fluorinated alkyl group which may have a substituent, or a cycloalkyl group which may have a substituent; L₁'s independently represent a single bond or a substituent selected from an arylene group, a heteroarylene group, a carbonyl group, -COO- and -CONR'- (wherein R' represents a hydrogen atom or an alkyl group); A represents a bivalent acceptor unit; D₁ and D₂ independently represent a donor unit; and m and n independently represent an integer of 0-2.)

Description

Organic photoelectric conversion element and solar cell

The present invention relates to an organic photoelectric conversion element and a solar cell, and more particularly to a bulk heterojunction type organic photoelectric conversion element and a solar cell using the organic photoelectric conversion element.

Due to the recent rise in fossil energy, a system that can generate electric power directly from natural energy has been demanded. Solar cells using single-crystal / polycrystal / amorphous Si, GaAs, CIGS (copper (Cu), indium (In) ), Semiconductor materials such as gallium (Ga) and selenium (Se)), and dye-sensitized photoelectric conversion elements (Gretzel cells) have been proposed and put to practical use.

However, the cost of generating electricity with these solar cells is still higher than the price of electricity generated and transmitted using fossil fuels, which has hindered the spread. In addition, since heavy glass must be used for the substrate, reinforcement work is required at the time of installation, which is one of the causes that increase the power generation cost.

For such a situation, as a solar cell that can achieve a power generation cost lower than that of fossil fuel, an electron donor layer (p-type semiconductor layer) and an electron acceptor layer (p-type semiconductor layer) are provided between the transparent electrode and the counter electrode. A bulk heterojunction photoelectric conversion element sandwiching a photoelectric conversion layer mixed with an n-type semiconductor layer) has been proposed, and an efficiency exceeding 5% has been reported (for example, see Non-Patent Document 1).

Solar cells using these bulk heterojunction type photoelectric conversion elements can be formed by coating other than the anode and cathode, so that they can be manufactured at high speed and at low cost, and the above-mentioned problem of power generation cost can be solved. There is sex. Furthermore, unlike the Si-based solar cells, semiconductor-based solar cells, and dye-sensitized solar cells described above, there is no manufacturing process at a temperature higher than 160 ° C., so that it can be formed on a cheap and lightweight plastic substrate. Is done.

However, further photoelectric conversion efficiency improvement is required to reduce power generation costs. In order to obtain a photoelectric conversion efficiency of 10% or more in an organic thin film solar cell, Non-Patent Document 2 requires a compound having a specific band gap (bg) and LUMO level as a p-type semiconductor. According to this document, the band gap is required to be 1.3 to 1.7 eV, and the LUMO level is required to be −3.9 to −4.0 eV (Non-patent Document 2).

Moreover, this condition is a necessary condition, and it is necessary to satisfy other conditions in order to actually obtain a photoelectric conversion efficiency of 10%. In the said nonpatent literature 2, two conditions that an external quantum efficiency (EQE) is 65% and a fill factor (FF) are 65% are set as a precondition.

Here, the external quantum efficiency (EQE) is a value indicating how many electrons can be generated from one photon of sunlight decomposed into a spectrum, and the fill factor (FF) is the resistance inside the solar cell. This value is the ratio of the actual maximum power on the IV characteristic and the product of the open circuit voltage and the short circuit current.

This curve factor and external quantum efficiency are said to be related to the mobility of the semiconductor material in the power generation layer. If the mobility is high, the series resistance inside the solar cell is low, and the fill factor can be improved. In addition, since the length of the carrier that can be taken out is the product of mobility, carrier life, and built-in electric field, ideally a material with higher mobility can produce a thicker power generation layer and can increase absorbance, High external quantum efficiency can be aimed at.

Therefore, one of the important conditions is to have high mobility. However, since the mobility is generally higher in a crystalline material than amorphous, it is important to select a crystalline p-type semiconductor material. In particular, in the case of an organic compound as in the present invention, it is important that the material be as flat as possible in order to improve crystallinity.

That is, as a material for the power generation layer of the organic thin-film solar cell, a compound having a deeper LUMO level and a larger π conjugate length (small band gap and high crystallinity) is required.

In order to obtain such a deep LUMO level, as in Non-Patent Document 1, a donor unit (thiophene, etc.) having a high electron donating property and an acceptor unit (nitrogen-containing aromatic ring, etc.) having a high electron attractive property are used. Many copolymers have been studied.

Also, an attempt has been made to obtain a p-type polymer material having a deep LUMO level and a low band gap by adding an electron-withdrawing group to thiophene known as a high mobility mother nucleus.

Non-Patent Document 3 discloses a structure in which a dicyanomethylene group is added to a thiophene ring, but the dicyanomethylene group causes steric hindrance with the adjacent thiophene ring and twists the π-conjugated surface, or the mobility is insufficient. The conversion efficiency was also low, less than 1%.

Non-Patent Document 4 discloses a structure in which an ester group is added to thiophene. Similarly, an ester group also causes steric hindrance with the adjacent thiophene ring and twists the π-conjugated surface, so that a vinylene group is sandwiched between them. To ensure flatness. However, the level was not deep enough and the conversion efficiency was as low as 2%.

Non-Patent Document 5 discloses a p-type polymer material into which a thiazolothiazole group, which is known as an acceptor nucleus of relatively high mobility even in organic TFTs, is introduced as a donor-acceptor type polymer. However, the level was not deep enough and the conversion efficiency was as low as 2%.

The present inventors paid attention to polythiophene having a thiophene group substituted with an alkynyl group as disclosed in Non-Patent Document 5 and Patent Document 2. As disclosed in Non-Patent Document 5, the alkynyl group does not cause twisting of the main chain even in a structure in which thiophene is continuous, and is a weak electron-withdrawing substituent, so that the LUMO level is slightly deepened. It is a structure that can. With such a structure, it is expected that the above requirement (a crystalline compound having a deeper LUMO level and a larger π-conjugated area) will be observed. Properties have not been evaluated. In these documents, only polymerization with thiophenes and benzenes is carried out. Further, donor-acceptor type polymers are not synthesized, and polymers with deep LUMO levels as described above are obtained. There wasn't.

In addition, there is a problem that the durability needs to be improved for practical use of organic thin-film solar cells, but a metal having a high work function that is unlikely to cause deterioration of electrodes and the like is used, and the sunlight incident side is used as a cathode. Since it is known that durability is improved in a solar cell of a type (so-called reverse layer type solar cell) (Patent Document 1), a material capable of providing high photoelectric conversion efficiency in a reverse layer structure has been demanded.

JP 2009-146981 A US Patent Application Publication No. 2004/127592

The present invention has been made in view of the above problems, and an object thereof is to provide an organic photoelectric conversion element having high photoelectric conversion efficiency and excellent durability, and a solar cell using the organic photoelectric conversion element.

The above object of the present invention is achieved by the following means.

An organic photoelectric conversion element having a transparent first electrode, a photoelectric conversion layer containing a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode in this order on a transparent substrate, An organic photoelectric conversion element, wherein the photoelectric conversion layer contains a compound having a partial structure represented by the following general formula 1 or general formula 1 ′ as the p-type organic semiconductor material.

(In the formula, each X ₁ independently represents —S—, —O—, —NR ₂ —, and each Y ₁ independently represents —CR ₃ ═ or —N═. R ₁ -R ₃ each independently represents a hydrogen atom, an alkyl group that may have a substituent, a fluorinated alkyl group that may have a substituent, or a cycloalkyl group that may have a substituent. L ₁ is independently selected from a single bond, an arylene group, a heteroarylene group, a carbonyl group, —COO—, and —CONR′— (wherein R ′ represents a hydrogen atom or an alkyl group). A represents a divalent acceptor unit, D ₁ and D ₂ represent a donor unit, and m and n represent an integer of 0 to 2.)

The above-described means of the present invention can provide an organic photoelectric conversion element having high photoelectric conversion efficiency and excellent durability, and a solar cell using the organic photoelectric conversion element.

The schematic sectional drawing which shows the example of a structure of the organic photoelectric conversion element of this invention. The schematic sectional drawing which shows the other example of a structure of the organic photoelectric conversion element of this invention. The schematic sectional drawing which shows the example of the organic photoelectric conversion element of this invention provided with the tandem type photoelectric conversion layer.

The present invention is an organic photoelectric conversion element having a transparent first electrode, a photoelectric conversion layer containing a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode in this order on a transparent substrate. The photoelectric conversion layer contains a compound having a partial structure represented by the general formula 1 as a p-type organic semiconductor material.

In the present invention, a compound having a partial structure represented by the above general formula 1 is used as a p-type organic semiconductor material of a bulk heterojunction photoelectric conversion layer that contains a p-type organic semiconductor material and an n-type organic semiconductor material. Thus, an organic photoelectric conversion element having a high fill factor value, high photoelectric conversion efficiency, and excellent durability can be provided.

(Configuration of organic photoelectric conversion element)
FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the organic photoelectric conversion element of the present invention.

The organic photoelectric conversion element 10 has a transparent first electrode 12 on a transparent substrate 11, a photoelectric conversion layer 14 on the first electrode 12, and a first electrode on the photoelectric conversion layer 14. Two electrodes 13 are provided.

In the example of FIG. 1, a hole transport layer 17 described later is provided between the first electrode 12 and the photoelectric conversion layer 14, and an electron transport layer described later is provided between the photoelectric conversion layer 14 and the second electrode 13. 18

In the present invention, the substrate 11 and the first electrode 12 are transparent, and light used for photoelectric conversion enters from the direction of the arrow in FIG.

The photoelectric conversion layer 14 is a layer that converts light energy into electric energy, and contains a p-type semiconductor material and an n-type semiconductor material.

The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor).

Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

In FIG. 1, light incident from the first electrode 12 through the substrate 11 is absorbed by the electron acceptor or the electron donor in the photoelectric conversion layer 14, and electrons move from the electron donor to the electron acceptor. A pair of holes and electrons (charge separation state) is formed.

The generated electric charge is generated between the electron acceptors due to the internal electric field, for example, when the work functions of the first electrode 12 and the second electrode 13 are different, due to the potential difference between the first electrode 12 and the second electrode 13. And the holes pass between the electron donors and are carried to different electrodes, and a photocurrent is detected.

In the example of FIG. 1, the work function of the first electrode 12 is deeper (larger) than the work function of the second electrode 13, so that holes are transported to the first electrode 12 and electrons are transported to the second electrode 13. Is done. In this case, the second electrode 13 is made of a metal that has a shallow (small) work function and is easily oxidized. In this case, the first electrode functions as an anode (anode) and the second electrode functions as a cathode (cathode).

Figure 2 shows an example of another configuration.

In FIG. 2, in contrast to the case of FIG. 1, the work function of the second electrode 13 is made larger than the work function of the first electrode 12, so that electrons are transferred to the first electrode 12. The case where it designed so that it might convey to the 2nd electrode 13 was shown. In this case, an electron transport layer 18 is provided between the first electrode 12 and the photoelectric conversion layer 14, and a hole transport layer 17 described later is provided between the photoelectric conversion layer 14 and the second electrode 13. The first electrode functions as a cathode (cathode) and the second electrode functions as an anode (anode).

In the present invention, particularly from the viewpoint of durability, the configuration shown in FIG. 2, that is, the first electrode is a cathode (cathode) and the second electrode is an anode (anode) is a preferred embodiment.

Although not shown in FIGS. 1 and 2, the organic photoelectric conversion element of the present invention has a layer such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer. You may have.

Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). FIG. 3 is a cross-sectional view illustrating an organic photoelectric conversion element including a tandem photoelectric conversion layer.

In the case of the tandem configuration, the first electrode 12 and the first photoelectric conversion layer 14 ′ are stacked on the substrate 11, the charge recombination layer 15 is stacked, the second photoelectric conversion layer 16, and then the second photoelectric conversion layer 15. By stacking the electrodes 13, a tandem configuration can be obtained.

The second photoelectric conversion layer 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion layer 14 'or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. is there.

Further, a hole transport layer 17 and an electron transport layer 18 may be provided between the first photoelectric conversion layer 14 'and the second photoelectric conversion layer 16 and each electrode. Also in the configuration, each photoelectric conversion layer preferably has a configuration as shown in FIG.

The materials that make up these layers are described below.

[P-type organic semiconductor materials]
In the present invention, the photoelectric conversion layer contains a compound having a partial structure represented by the following

general formula

1 or 1 ′ as a p-type organic semiconductor material. Such a compound can provide an organic photoelectric conversion element having high photoelectric conversion efficiency, excellent durability, and preferably a high fill factor, and a solar cell using the organic photoelectric conversion element.

In the

general formula

1 or 1 ′, X ₁ , Y ₁ , R ₁ to R ₃ , L ₁ and A, and D ₁ , D ₂ , m and n (general formula 1 ′) in each partial structure are the same as each other It may be different or different.

In addition, the compound includes one or more partial structures represented by the

general formula

1 or 1 ′. When there are two or more partial structures, X ₁ and Y ₁ between the partial structures are present. , R ₁ to R ₃ , L ₁ and A, and D ₁ , D ₂ , m and n (general formula 1 ′) may be the same as or different from each other.

(In the formula, each X ₁ independently represents —S—, —O—, —NR ₂ —, and each Y ₁ independently represents —CR ₃ ═ or —N═. R ₁ -R ₃ each independently represents a hydrogen atom, an alkyl group that may have a substituent, a fluorinated alkyl group that may have a substituent, or a cycloalkyl group that may have a substituent. L ₁ represents a substituent independently selected from a single bond, an arylene group, a heteroarylene group, a carbonyl group, —COO—, and —CONR′— (wherein R ′ is a hydrogen atom or an alkyl group). A represents a divalent acceptor unit, D ₁ and D ₂ represent a donor unit, and m and n represent an integer of 0 to 2.)
In the formula, the position of substitution with the adjacent unit in the unit represented by the

chemical formula

1 or 1 ′ represents that it is substituted at either the 2-position or 5-position, respectively. That is, the partial structure of the general formula 1 includes the following acceptor unit -A- and left and right X ₁ :

This means that the bonding position is not limited, and actually includes all of the following four isomers, and any of these may be used.

The partial structure of the general formula 1 ′ includes the following structure including a left donor unit —D ₁ — and left X ₁ and Y ₁ :

This means that the bonding position of is not limited, and actually includes all of the following two isomers, and any of these may be used. The same applies to the structure containing the right donor unit -D ₂ -and the right X ₁ and Y ₁ .

Since the p-type semiconductor material in the photoelectric conversion layer has a compound having a partial structure represented by the

general formula

1 or 1 ′, (1) an electron-withdrawing alkynyl group is substituted. The HOMO / LUMO level is deepened and the open circuit voltage is expected to be improved. (2) The π-conjugated area is increased by the alkynyl group, the crystallinity is improved, and the mobility is improved. (3) The alkynyl group is linear. The steric hindrance to other aromatic rings connected to the

general formula

1 or 1 ′ in the state is less likely to occur, so that the planarity of the main chain is maintained, and further improvement in crystallinity and mobility is expected. It is estimated that high photoelectric conversion efficiency can be provided by the effect. In addition, these alkynyl group-substituted heteroaryl groups include an acceptor unit in the DA type polymer and are preferably present at a position adjacent to the acceptor unit (the partial structure represented by the general formula 1 or the general formula (Partial structure when m = 0 at 1 ′), the effects (1) to (3) are more exhibited.

As described above, the oligomer and polymer of the present invention have a very high planarity, and are easily π-stacked between molecules as described above. Therefore, donor materials also form a network structure by interaction with each other in the bulk heterojunction layer. However, it is presumed that even with a thick film thickness, it is possible to form a highly continuous morphology without a dead end (a region where carriers cannot be extracted).

In

General Formulas

1 and 1 ′, R ₁ to R ₃ may have a hydrogen atom, an alkyl group that may have a substituent, a fluorinated alkyl group that may have a substituent, or a substituent. Represents a cycloalkyl group. In

general formulas

1 and 1 ′, there are two R _{1 s} , and each R ₁ may be the same or different, but the same from the viewpoint of symmetry and synthesis. Preferably there is.

The alkyl group represented by R ₁ to R ₃ is preferably a linear or branched alkyl group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. It is. The alkyl group is not particularly limited, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, Isopentyl, tert-pentyl, neopentyl, 1,2-dimethylpropyl, n-hexyl, isohexyl, 1,3-dimethylbutyl, 1-isopropylpropyl, 1,2-dimethylbutyl, n -Heptyl group, 1,4-dimethylpentyl group, 3-ethylpentyl group, 2-methyl-1-isopropylpropyl group, 1-ethyl-3-methylbutyl group, n-octyl group, 2-ethylhexyl group, 3-methyl -1-isopropylbutyl group, 2-methyl-1-isopropyl group, 1-t-butyl-2-methylpropyl group, n-noni Group, 3,5,5-trimethylhexyl group, n-decyl group, isodecyl group, n-undecyl group, 1-methyldecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, Examples thereof include n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, 2-hexyldecyl group, 2-decyltetradecyl group and the like.

The fluorinated alkyl group is a fluorinated alkyl group in which part or all of the alkyl group is fluorinated. In addition, since the solubility of a fully fluorinated alkyl group is likely to be lowered, it may be a fluorinated alkyl group in which the position close to the mother nucleus is an alkyl group and the terminal portion is a fluorinated alkyl group. preferable. For example, — (CH ₂ CH ₂ ) —C ₄ F ₉ , — (CH ₂ CH ₂ ) —C ₇ F ₁₅ , etc.

The cycloalkyl group preferably has 4 to 8 carbon atoms, and examples thereof include cyclopropyl, cyclopentyl, cyclohexyl, norbornyl, adamantyl and the like.

Among these substituents, R ₁ and R ₂ are preferably C ₆ or more and C ₁₆ or less alkyl groups. This is because the p-type semiconductor material to be obtained needs to have a certain level of solubility in order to be formed with a sufficiently thick film, and in terms of imparting solubility, a material substituted with these substituents It is preferable that In particular, in the case of a polymer material, in addition to imparting solubility, a linear alkyl group may provide alignment and may provide high mobility (also referred to as a fastener effect). A p-type material substituted with an alkyl group is preferred.

Substituents optionally present in the alkyl group, fluorinated alkyl group, or cycloalkyl group include alkyl groups, fluorinated alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, acyl groups, alkoxycarbonyl groups, (Alkyl) amino group, alkoxy group, cycloalkyloxy group, aryloxy group, aryloxycarbonyl group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, Arylthio group, silyl group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, halogen atom, hydroxyl group, mercapto group, cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfur group Inomoto, mention may be made of a hydrazino group, an imino group, and the like.

In addition, the substituent which exists depending on the case is not the same as the substituent to be substituted. For example, when R ₁ or R ₂ is an alkyl group, it is not further substituted with an alkyl group.

The alkyl group preferably has 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and specific examples thereof include the alkyl groups described above.

Specific examples of the fluorinated alkyl group include the fluorinated alkyl groups described above.

The alkenyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8 carbon atoms, and examples thereof include vinyl, allyl, 2-butenyl, and 3-pentenyl. .

The alkynyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, and examples thereof include propargyl and 3-pentenyl.

The aryl group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples thereof include a phenyl group, a biphenyl group, and a terphenyl group. Non-condensed hydrocarbon group: pentarenyl group, indenyl group, naphthyl group, azulenyl group, heptalenyl group, biphenylenyl group, fluorenyl group, acenaphthylenyl group, preadenenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl And condensed polycyclic hydrocarbon groups such as a group, an acephenanthrenyl group, an aceanthrylenyl group, a triphenylenyl group, a pyrenyl group, a chrycenyl group, and a naphthacenyl group.

The heteroaryl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom, specifically, for example, a pyridyl group. , Pyrimidyl group, pyrazinyl group, triazinyl group, furanyl group, pyrrolyl group, thiophenyl group (thienyl group), quinolyl group, furyl group, piperidyl group, comarinyl group, silafluorenyl group, benzofuranyl group, benzimidazolyl group, benzoxazolyl group , Benzthiazolyl group, dibenzofuranyl group, benzothiophenyl group, dibenzothiophenyl group, indolyl group, carbazolyl group, pyrazolyl group, imidazolyl group, oxazolyl group, isoxazolyl group, thiazolyl group, indazolyl group, benzothiazolyl group, pyridazinyl group, cinnolin Group, quinazolyl group, quinoxalyl group, phthalazinyl group, phthalazine dionyl group, phthalamidyl group, chromonyl group, naphtholactamyl group, quinolonyl group, naphthalidinyl group, benzimidazolonyl group, benzoxazolonyl group, benzothiazolonyl Group, benzothiazothionyl group, quinazolonyl group, quinoxalonyl group, phthalazonyl group, dioxopyrimidinyl group, pyridonyl group, isoquinolinyl group, isoquinolinyl group, isothiazolyl group, benzisoxazolyl group, benzisothiazolyl group, indazironyl group, Acridinyl group, acridonyl group, quinazoline dionyl group, quinoxaline dionyl group, benzoxazine dionyl group, benzoxazinonyl group, naphthalimidyl group, dithienocyclopentadienyl group, dithienosilacyclopentadi Group, Jichienopiroriru group, etc. benzodithiolium phenyl group.

The acyl group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms. Specifically, the acyl group is represented by the formula: —C (O) R. In this case, R is preferably an alkyl group having 1 to 24 carbon atoms, and examples of the alkyl group include the alkyl groups described above.

The alkoxycarbonyl group preferably has 2 to 25 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 12 carbon atoms. Specifically, the alkoxycarbonyl group is represented by the formula: —C (O) OR. In this case, R is preferably an alkyl group having 1 to 24 carbon atoms, and examples of the alkyl group include the alkyl groups described above.

The (alkyl) amino group preferably has 0 to 24 carbon atoms, more preferably 0 to 10 carbon atoms, and particularly preferably 0 to 6 carbon atoms. For example, amino, methylamino, dimethylamino, diethylamino, dibenzylamino Etc.

The alkoxy group is preferably a group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, specifically a group represented by the formula: —OR; In this case, R is preferably an alkyl group having 1 to 24 carbon atoms, and examples of the alkyl group in this case include the alkyl groups described above.

The cycloalkyloxy group preferably has 4 to 8 carbon atoms, and examples thereof include cyclopentyloxy and cyclohexyloxy.

The aryloxy group preferably has 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, and particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyloxy and 2-naphthyloxy.

The aryloxycarbonyl group preferably has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, and particularly preferably 7 to 10 carbon atoms, and examples thereof include phenyloxycarbonyl.

The acylamino group preferably has 2 to 21 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 10 carbon atoms. Specifically, the acylamino group is a group represented by the formula: —NHCOR; In this case, R is preferably an alkyl group having 1 to 24 carbon atoms, and examples of the alkyl group in this case include the alkyl groups described above.

The alkoxycarbonylamino group preferably has 2 to 24 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino.

The aryloxycarbonylamino group preferably has 7 to 24 carbon atoms, more preferably 7 to 16 carbon atoms, and particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino.

The sulfonylamino group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include methanesulfonylamino and benzenesulfonylamino.

The sulfamoyl group preferably has 0 to 24 carbon atoms, more preferably 0 to 16 carbon atoms, and particularly preferably 0 to 12 carbon atoms. For example, sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamo Moyl etc. are mentioned.

The carbamoyl group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl and the like.

The alkylthio group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include methylthio and ethylthio.

The arylthio group preferably has 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenylthio.

The sulfonyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include mesyl and tosyl.

The sulfinyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include methanesulfinyl and benzenesulfinyl.

The ureido group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include ureido, methylureido, and phenylureido.

The phosphoric acid amide group preferably has 1 to 24 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include diethyl phosphoric acid amide and phenyl phosphoric acid amide. .

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

L ₁ represents a substituent selected from a single bond, an arylene group, a heteroarylene group, a carbonyl group, —COO—, and —CONR′— (wherein R ′ represents a hydrogen atom or an alkyl group). Since these substituents can deepen the HOMO / LUMO level of the structure represented by the general formula 1 and increase the π conjugate area, higher open-circuit voltage and higher mobility, that is, higher fill factor External quantum efficiency can be expected. L ₁ is preferably a single bond or —COO—, and more preferably —COO— because the photoelectric conversion efficiency is improved and the durability is also improved. In

general formulas

1 and 1 ′, there are two L _{1 s} , and each L ₁ may be the same or different, but the same from the viewpoint of symmetry and synthesis. Preferably there is.

Here, the arylene group preferably has 6 to 30 carbon atoms, more preferably 6 to 24 carbon atoms, and particularly preferably 6 to 12 carbon atoms. For example, phenylene, p-methylphenylene, naphthylene, phenanthrylene, pyrenylene. Etc.

The heteroarylene group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. Imidazolyl, pyridyl, quinolyl, furyl, piperidyl, benzoxazolyl, benzimidazolyl, benzthiazolyl, thienyl, furyl, pyrrole, thiazolyl and the like.

Examples of the alkyl group when R ′ in —CONR′— is an alkyl group include those described in the above R ₁ to R ₃ columns.

Or a linking group in which a plurality of these are bonded to each other.

In the formula, X ₁ represents —S—, —O—, —NR ₂ —. In order for the structure represented by the

general formula

1 or 1 ′ to maintain a plane without causing steric hindrance with an adjacent group, X ₁ is preferably —S— or —O—. More preferred is —S— from the viewpoint of durability. In

general formulas

1 and 1 ′, there are two X _{1 s} , and each X ₁ may be the same or different, but the same from the viewpoint of symmetry and synthesis. Preferably there is.

In the

general formulas

1 and 1 ′, the group represented by Y ₁ represents —CR ₃ ═ or —N═. Among these, from the viewpoint of photoelectric conversion efficiency, Y ₁ is preferably —CR ₃ ═, more preferably —CH═. Especially when _{X 1} is -S-, _{since Y 1} is -CH = compound _{(R 3} is a hydrogen atom) is (thiophene) is easily obtained high mobility, improved photoelectric conversion efficiency, _{Y 1} is - It is preferable that CH =. In

general formulas

1 and 1 ′, there are two Y _{1 s} , and each Y ₁ may be the same or different, but the same from the viewpoint of symmetry and synthesis. Preferably there is.

The partial structure represented by the general formula 1 may further have a donor unit or an acceptor unit. Specific partial structures include: the partial structure of the general formula 1 -D-, -general Examples include the partial structure of formula 1 -DAD-, the partial structure of general formula 1 -A-, and the like. Here, A indicates an acceptor unit, and D indicates a donor unit.

The donor unit represented by D ₁ and D ₂ in the general formula 1 ′ will be described later. In Formula 1 ′, m and n are integers of 0 to 2, and it is preferable that m = n = 0 or m = n = 1.

The acceptor unit represented by A in the formula is generally a partial structure in which the LUMO level or the HOMO level is deeper than a hydrocarbon aromatic ring having the same number of π electrons (benzene, naphthalene, anthracene, etc.) Unit). In addition, in order to achieve higher photoelectric conversion efficiency, the acceptor unit included in the compound that is a conjugated polymer of this embodiment is a partial structure represented by the following among the acceptor units included in the conjugated polymer. It is preferable to contain. Specifically, the number of partial structures represented below is preferably 50% or more, more preferably 70% or more, based on the total number of acceptor units contained in the conjugated polymer. 90% or more, more preferably 95% or more, and most preferably 100%.

The following are specific examples of the acceptor unit represented by A.

In the formulas A1 to A41, R is a hydrogen atom, an optionally substituted alkyl group, an optionally substituted fluorinated alkyl group, an optionally substituted cycloalkyl group, an optionally substituted alkoxy group or a substituted group. The aryl group which may be sufficient is shown. Here, examples of the alkyl group, the fluorinated alkyl group, and the cycloalkyl group include those described in the above R ₁ to R ₃ columns. The aryl group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples thereof include a phenyl group, a biphenyl group, and a terphenyl group. Non-condensed hydrocarbon group: pentarenyl group, indenyl group, naphthyl group, azulenyl group, heptalenyl group, biphenylenyl group, fluorenyl group, acenaphthylenyl group, preadenenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl And condensed polycyclic hydrocarbon groups such as a group, an acephenanthrenyl group, an aceanthrylenyl group, a triphenylenyl group, a pyrenyl group, a chrycenyl group, and a naphthacenyl group. The alkoxy group is preferably a group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, specifically a group represented by the formula: —OR; In this case, R is preferably an alkyl group having 1 to 24 carbon atoms, and examples of the alkyl group in this case include those described in the above R ₁ to R ₃ column. Examples of the substituent optionally present in the alkyl group, fluorinated alkyl group, cycloalkyl group, alkoxy group or aryl group include those described in the above R ₁ to R ₃ columns. R is preferably a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted aryl group, more preferably a hydrogen atom or an optionally substituted alkyl group having 1 to 12 carbon atoms. . In the formulas A1 to A41, when there are a plurality of R, each R may be the same or different substituent.

Among the above acceptor units, a unit having a deep level is easily obtained, the photoelectric conversion efficiency is improved, and the durability is improved. Therefore, the unit represented by A is preferably a nitrogen-containing heteroaromatic ring group. . Further, in consideration of mobility, the unit is preferably a unit having a large π-conjugated area by condensation, and the unit represented by A is preferably a condensed polycyclic group in which two or more rings are condensed.

In consideration of mobility, the unit is preferably a unit having a large π-conjugated area by condensation. Specifically, the units are A-1 to A-19 and A-33 to 38.

That is, specific examples of the condensed polycyclic group in which two or more units are condensed include the following structures.

In the formula, X ₂ to X ₄ are —S—, —O—, —NR ₄ —, —CR ₅ = CR _{5 ′} —, —CR ₆ = N—, —CR _A R _B —, or — N = N-. R ₄ , R ₅ , R _{5 ′} , R ₆ , R _A and R _B are each independently a hydrogen atom, an alkyl group which may have a substituent, or a fluorinated alkyl which may have a substituent Or a cycloalkyl group which may have a substituent. The alkyl group which may have a substituent, the fluorinated alkyl group which may have a substituent, or the cycloalkyl group which may have a substituent has been described in the above R ₁ to R ₃ columns. It is the same as that.

In order to maintain a flat surface without causing steric hindrance with an adjacent group, X ₂ is preferably —S— or —O—, more preferably —S—. A p-type organic semiconductor material having thiazolothiazole as an acceptor unit is preferable because it can provide high mobility. The above formula _{R 7} and _{R 8} are the same as _{R 7} and _{R 8} in the following general formulas 4A and 4B, separately described in detail below.

The structure represented by the general formula 1 is preferably a structure represented by the following general formula 2 in terms of durability.

In particular, a p-type organic semiconductor material in which X ₂ is S in General Formula 2 has thiazolothiazole as an acceptor unit, and thus can provide high mobility and is preferable.

Moreover, it is preferable that the compound containing the structural unit represented by the general formula 2 further has any of the acceptor units represented by the following general formula 4A or 4B. Such a structure can absorb longer wavelengths and can provide a high short-circuit current.

In the formula, Y ³ and Y ⁴ each independently represent —O—, —NR ₁₀ —, —S—, —C (R ₁₁ ) ═C (R _{11 ′} ) —, or —N═C (R ₁₂ ) —, wherein R ₁₀ , R ₁₁ , R _{11 ′} and R ₁₂ are each independently an alkyl group, a fluorinated alkyl group or a cyclo group which may have a hydrogen atom or a substituent. Represents an alkyl group.

R ₇ to R ₈ each independently represents a hydrogen atom, a halogen atom (F, Cl, Br, or I), a substituted or unsubstituted alkyl group having 1 to 24 carbon atoms, or 1 carbon atom. -24 fluorinated alkyl groups, cycloalkyl groups having 3 to 20 carbon atoms, fluorinated cycloalkyl groups having 3 to 20 carbon atoms, alkoxy groups having 1 to 24 carbon atoms, and fluorine groups having 1 to 24 carbon atoms. Alkoxy group, fluorinated alkylthio group having 1 to 24 carbon atoms, aryl group having 6 to 30 carbon atoms, fluorinated aryl group having 6 to 30 carbon atoms, heteroaryl group having 1 to 20 carbon atoms, or Represents a fluorinated heteroaryl group having 1 to 20 carbon atoms. In general formula 4A, there are two R _{7 s} , and in general formula 4B there are two R _{8 s} . Each R ₇ , R ₈ may be the same or different, but they are symmetrical. From the viewpoints of properties and synthesis, the same is preferable. Further, the compound preferably contains one or more partial structures represented by the general formula 4A or 4B. When two or more partial structures are present, Y ₃ , Y in each partial structure ₄ and R ₁₀ to R ₁₂ may be the same as or different from each other. R ₇ to R ₈ are preferably a hydrogen atom or a halogen atom (preferably a fluorine atom). In order to maintain a plane without causing steric hindrance with adjacent groups, Y ₃ and Y ₄ are preferably —S— and —O—, and more preferably because they can provide high mobility. Is -S-.

Here, examples of the alkyl group, fluorinated alkyl group or cycloalkyl group which may be substituted in R ₇ to R ₈ and R ₁₀ to R ₁₂ include those described in the above R ₁ to R ₃ column. .

Examples of the fluorinated cycloalkyl group in R ⁷ to R ⁸ include groups in which at least one hydrogen atom contained in the cycloalkyl group exemplified above is substituted with a fluorine atom. The alkoxy group having 1 to 24 carbon atoms is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, an n-octyloxy group, an n-decyloxy group, and an n-hexadecyl group. Examples thereof include an oxy group, 2-ethylhexyloxy group, and 2-hexyldecyloxy group. Examples of the fluorinated alkoxy group include a group in which at least one hydrogen atom contained in the alkoxy group exemplified above is substituted with a fluorine atom. The aryl group having 6 to 30 carbon atoms is not particularly limited, and examples thereof include non-condensed hydrocarbon groups such as a phenyl group, a biphenyl group, and a terphenyl group; a pentarenyl group, an indenyl group, a naphthyl group, an azulenyl group, Heptalenyl group, biphenylenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylenyl group, pyrenyl group , Condensed polycyclic hydrocarbon groups such as a chrycenyl group and a naphthacenyl group. The fluorinated aryl group having 6 to 30 carbon atoms is not particularly limited, and examples thereof include a group in which at least one hydrogen atom contained in the aryl group exemplified above is substituted with a fluorine atom. The heteroaryl group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include pyridyl group, pyrimidyl group, pyrazinyl group, triazinyl group, furanyl group, pyrrolyl group, thiophenyl group (thienyl group), quinolyl group, Furyl group, piperidyl group, coumarinyl group, silafluorenyl group, benzofuranyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, dibenzofuranyl group, benzothiophenyl group, dibenzothiophenyl group, indolyl group, carbazolyl group, pyrazolyl Group, imidazolyl group, oxazolyl group, isoxazolyl group, thiazolyl group, indazolyl group, benzothiazolyl group, pyridazinyl group, cinnolyl group, quinazolyl group, quinoxalyl group, phthalazinyl group, phthalazine dionyl group, phthalamidyl group, Romonyl, naphtholactamyl, quinolonyl, naphthalidinyl, benzimidazolonyl, benzoxazolonyl, benzothiazolonyl, benzothiazothionyl, quinazolonyl, quinoxalonyl, phthalazonyl, dioxopyrimidinyl Group, pyridonyl group, isoquinolonyl group, isoquinolinyl group, isothiazolyl group, benzisoxazolyl group, benzisothiazolyl group, indazironyl group, acridinyl group, acridonyl group, quinazoline dionyl group, quinoxaline dionyl group, benzoxazine dionyl Group, benzoxazinonyl group, naphthalimidyl group, dithienocyclopentadienyl group, dithienosylcyclopentadienyl group, dithienopyrrolyl group, benzodithiophenyl group and the like. The fluorinated heteroaryl group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include groups in which at least one hydrogen atom contained in the heteroaryl group exemplified above is substituted with a fluorine atom. .

Further, the compound contained in the p-type organic semiconductor material of the present invention is preferably a copolymer of the structure represented by the general formula 1 and a donor unit. Alternatively, in General Formula 1 ′, at least one of m and n is one or more forms, which is a preferable form because it has a donor unit. In the present invention, the donor unit that can be included in the conjugated polymer compound of the present embodiment has a LUMO level or a HOMO level rather than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same number of π electrons. If it is a shallow unit, it can be used without restriction. For example, a unit including a thiophene ring, a furan ring, a pyrrole ring, a hetero 5-membered ring such as cyclopentadiene, silacyclopentadiene, and a condensed ring thereof.

Specific examples include thiophene, thienothiophene, bithiophene, fluorene, silafluorene, carbazole, dithienocyclopentadiene, dithienosylcyclopentadiene, dithienopyrrole, and benzodithiophene. Among these units, it is preferable to have a thiophene structure capable of imparting high mobility, and thus, the photoelectric conversion efficiency can be further improved. Further, the solubility and crystallinity are improved by substituting the hydrogen atom bonded to the atoms constituting the ring structure with a linear or branched alkyl group or alkoxy group having 1 to 24 carbon atoms. It is also possible.

Hereinafter, preferred forms of the donor unit will be exemplified.

Here, in the above D1 to D18, R may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, a fluorinated alkyl group which may have a substituent, or a substituent. A cycloalkyl group, an alkoxy group which may have a substituent, a fluorinated alkoxy group which may have a substituent, a cycloalkoxy group which may have a substituent, an alkoxycarbonyl which may have a substituent A group, an acyl group which may have a substituent, an alkylaminocarbonyl group which may have a substituent, or an acylamino group which may have a substituent. Among these substituents, a hydrogen atom or an alkyl group which may have a substituent is preferable. The halogen atom, an alkyl group that may have a substituent, a fluorinated alkyl group that may have a substituent, a cycloalkyl group that may have a substituent, and an alkoxy group that may have a substituent Examples of the fluorinated alkoxy group which may have a substituent and the cycloalkoxy group which may have a substituent include those described in the above R ₇ to R ₈ columns. In addition, when two or more R exists in the said donor property unit, each R may be the same substituent and may be different substituents.

In R, the alkoxycarbonyl group is preferably an alkoxycarbonyl group (—COOR) having 2 to 30 carbon atoms, more preferably 2 to 24 carbon atoms, and still more preferably 6 to 24 carbon atoms. Methoxycarbonyl group, ethoxycarbonyl group, isopropoxycarbonyl group, tert-butoxycarbonyl group, n-hexyloxycarbonyl group, n-octyloxycarbonyl group, n-decyloxycarbonyl group, n-hexadecyloxycarbonyl group, 2- Examples include an ethylhexyloxycarbonyl group and a 2-hexyldecyloxycarbonyl group.

In R, the acyl group (—COR) is preferably an alkoxycarbonyl group (—COOR) having 2 to 30 carbon atoms, more preferably 2 to 24 carbon atoms, and still more preferably 6 to 25 carbon atoms. For example, acetyl, propionyl, butyryl, isobutyryl, tert-butyryl, pentanoyl, valeryl, isovaleryl, pivaloyl, hexanoyl, heptanoyl, octanoyl, decanoyl, dodecanoyl, hexadecanoyl Group, octadecanoyl group, cyclohexanecarbonyl group, benzoyl group, 2-ethylhexylcarbonyl group, 2-hexyldecylcarbonyl group and the like.

In R, the alkylaminocarbonyl group (—CONHR or —CONRR ′) is preferably an alkylaminocarbonyl having 2 to 40 carbon atoms, more preferably 9 to 40 carbon atoms, and still more preferably 13 to 24 carbon atoms. Groups such as dimethylaminocarbonyl group, diethylaminocarbonyl group, diisopropylaminocarbonyl group, methyl-tert-butylaminocarbonyl group, dihexylaminocarbonyl group, dioctylaminocarbonyl group, didecylaminocarbonyl group, dihexadecylaminocarbonyl Group, di2-ethylhexylaminocarbonyl group, di2-hexyldecylaminocarbonyl group and the like.

In R, the acylamino group (—NHCOR) is preferably an acylamino group having 2 to 30 carbon atoms, and examples thereof include an acetamide group, an ethylamide group, and a propylamide group.

Among the donor units, a unit represented by the general formula 3 is preferable.

In the formula, each R ₉ independently has a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, a fluorinated alkyl group which may have a substituent, or a substituent. A cycloalkyl group, an alkoxy group which may have a substituent, a fluorinated alkoxy group which may have a substituent, a cycloalkoxy group which may have a substituent, an alkoxycarbonyl which may have a substituent A group, an acyl group which may have a substituent, an alkylaminocarbonyl group which may have a substituent, or an acylamino group which may have a substituent. These substituents are the same as those described in the column of R in the above D1 to D18. In formula 3, there are two R _{9 s,} but each R ₉ may be the same or different, but is preferably the same from the viewpoint of symmetry and synthesis. In addition, the compound preferably contains one or more partial structures represented by the general formula 3, but when there are two or more partial structures, R ₉ in each partial structure is the same as each other. It may be different or different.

The donor unit having such a structure has high crystallinity and can obtain higher conversion efficiency.

Furthermore, the compound having the structure represented by the general formula 1 is preferably a polymer compound having a number average molecular weight of 10,000 or more.

This is because the low-molecular compound (fullerene derivative) is widely used as the n-type organic semiconductor which is the other component constituting the bulk heterojunction type photoelectric conversion layer. This is because a microphase-separated structure is formed, and it is easy to generate carrier paths that respectively carry holes and electrons generated in the bulk heterojunction photoelectric conversion layer.

On the other hand, if the molecular weight is too large, the solubility is lowered, so the number average molecular weight of the compound is preferably 100,000 or less. More preferably, it is in the range of 15,000 to 50,000.

The molecular weight can be measured by gel permeation chromatography (GPC).

For example, the number average molecular weight can be measured by the following method.

Water per 150C ALC / GPC (column: GMHHR-H (S) manufactured by Tosoh Corporation), solvent: 1,2,4-trichlorobenzene), by gel permeation chromatography (GPC) method, The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured. In addition, column elution volume was calibrated by the universal calibration method using Tosoh Corporation standard polystyrene.

Also, purification according to molecular weight can be performed by preparative gel permeation chromatography (GPC).

The ratio of the partial structure according to the present invention to the compound having the partial structure according to the present invention is generally preferably 20 to 80% by mass and particularly preferably 25 to 60% by mass with respect to the compound. In the present invention, the compound is preferably a high molecular weight compound as described above. In this case, the compound has a partial structure as a repeating unit, and the entire compound including a repeating unit other than the partial structure is used. , Preferably in the range of 30 to 50 mol%.

Hereinafter, examples of the compound having the partial structure represented by the general formula 1 or the general formula 1 'will be described, but the present invention is not limited thereto.

In the above compound, it is sufficient that the number of repetitions (polymerization degree) of each unit is a value that falls within the above-mentioned molecular weight. For example, in order to fall within the range of a number average molecular weight of 10,000 to 100,000, approximately 10 to 200 is required. It needs to be about.

[Method for Synthesizing Compound According to the Present Invention]
Among the compounds according to the present invention, thiophenes substituted with an alkynyl group are described in Bull. Chem. Soc. Jpn. , 2005, p1368.

In addition, thiazolothiazole ring and the like are described in Adv. Mater. Can be synthesized with reference to 2007, 19, 4160, etc.

Hereafter, the synthesis example of the compound for organic photoelectric conversion elements of this invention is described.

In addition, it can synthesize | combine also about another compound using the alkynyl group substituted heteroaryl group which comprises a unit, an acceptor unit, and a donor unit.

(Exemplary Compound 11)

Synthesis of Exemplary Compound 11-1 Org. Chem. Exemplified compound 11-1 was synthesized with reference to 2002, p4178. 3-bromo-2-carboxaldehyde 4.0 g, Pd (PPh ₃ ) ₂ Cl ₂ 0.74 g, triphenylphosphine 0.14 g, triethylamine 3.2 g, 1-tetradecine After adding 4.5 g and 150 ml of dehydrated tetrahydrofuran and stirring at room temperature for 15 minutes, 60 mg of copper iodide was added and stirring was continued for 20 hours.

After completion of the reaction, the reaction mixture was filtered through celite and the solvent was distilled off. The resulting crude product was purified by silica gel column chromatography to obtain Exemplified Compound 11-1 (5.2 g, yield 80%).

Synthesis of Exemplified Compound 11-2 Exemplified Compound 11-2 was synthesized with reference to US Patent Application Publication No. 2010137376A1.

Example Compound 11-1; 3.0 g, rubeanic acid 0.4 g, and dimethylformamide (DMF) 60 ml were added and stirred at 150 ° C. for 8 hours. After completion of the reaction, the organic phase was separated with water / ethyl acetate, and then the organic phase was distilled off to obtain a crude product. Further purification by silica gel column chromatography gave Exemplified Compound 11-2 (0.69 g, 20%).

Synthesis of Exemplary Compound 11-3 Adv. Mater. Exemplified compound 11-3 was synthesized with reference to 2007, 19, 4160.

Exemplified Compound 11-2 (0.69 g) was dissolved in 30 ml of chloroform, 0.39 g of N-bromosuccinimide was added, reacted for 5 hours under reflux, water was added and the phases were separated to extract the organic phase. The solvent was distilled off to obtain a crude product, which was then purified by silica gel column chromatography to obtain Exemplified Compound 11-3 (0.64 g, 75%).

Synthesis of Exemplary Compound 11 Phys. Chem. Exemplified compound 11 was synthesized with reference to C 2010, 114, 16843.

Exemplified Compound 11-3; 255 mg and 2,6-bis (trimethyltin) -4,8-didodecyloxybenzo [1,2-b: 4,5-b ′] dithiophene (265 mg, 0.3 mmol) After dissolving in 15 ml of dehydrated toluene and degassing with nitrogen for 30 minutes, Pd (PPh3) 4 (35 mg, 0.03 mmol) was added, and the reaction was carried out under reflux for 72 hours. In order to further endcap, 2-tributyltin-thiophene (11 mg, 0.03 mmol) was added and refluxed for another 10 hours. Further, 2-bromothiophene (10 mg, 0.06 mmol) was added, and the mixture was further refluxed for 10 hours. After completion of the reaction, the reaction solution cooled to room temperature was reprecipitated in 150 ml of methanol, and the precipitate was filtered. The obtained precipitate fractionated a high molecular weight component using a gel filtration purification apparatus manufactured by Nippon Analytical Industrial Co., Ltd. to obtain a polymer having a number average molecular weight of 18000 (200 mg, 55%).

(Exemplary Compound 12)

Synthesis of Exemplary Compound 12-1 Org. Chem. Exemplified Compound 12-1 was synthesized with reference to 2002, p4178. Manufactured by Tokyo Chemical Industry under a nitrogen atmosphere; 4.0 g of 3-bromo-2-carboxaldehyde, 0.74 g of Pd (PPh3) 2Cl2, 0.14 g of triphenylphosphine, 3.2 g of triethylamine, and 2.27 g of trimethylsilylacetylene After adding 150 ml of dehydrated tetrahydrofuran and stirring at room temperature for 15 minutes, 60 mg of copper iodide was added and stirring was continued for 20 hours.

After completion of the reaction, the reaction mixture was filtered through celite and the solvent was distilled off to purify the crude product, which was purified by silica gel column chromatography to obtain Exemplified Compound 12-1 (3.5 g, yield 80%).

Synthesis of Exemplified Compound 12-2 Exemplified Compound 12-2 was synthesized with reference to US Patent Application Publication No. 2010137611A1.

Example Compound 12-1: 2.1 g, rubeanic acid 0.4 g, and dimethylformamide (DMF) 60 ml were added and stirred at 150 degrees for 8 hours. After completion of the reaction, the organic phase was separated with water / ethyl acetate, and then the organic phase was distilled off to obtain a crude product. Further purification by silica gel column chromatography gave Exemplified Compound 12-2 (0.50 g, 20%).

Synthesis of Exemplary Compound 12-3 Journal of the American Chemical Society, 1955, vol. 77, p. Synthesis was carried out with reference to 1911.

Example Compound 12-2; 0.5 g of 1N aqueous sodium hydroxide solution 0.5 g and 10 ml of tetrahydrofuran was stirred at room temperature for 2 hours, and then ethyl acetate was added to extract the organic layer to deprotect the trimethylsilyl group. .

This compound was dissolved in 20 ml of dehydrated tetrahydrofuran, cooled to −78 ° C., 1.0 ml of 2.0 M lithium diisopropylamine solution was added dropwise, and the mixture was stirred for 1 hour. After raising the temperature of the reaction solution to 0 ° C., dodecyl chloroformate (1.33 g) was added, and the reaction was further continued at room temperature for 5 hours.

After completion of the reaction, the purified salt was filtered and the organic layer was washed with 5% carbonate solution, and the organic layer was extracted and distilled to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain 0.65 g (yield 90%) of Exemplary Compound 12-3.

Synthesis of Exemplified Compound 12-4 Adv. Mater. Exemplified compound 12-4 was synthesized with reference to 2007, 19, 4160.

Exemplified Compound 12-3 (0.65 g) was dissolved in 30 ml of chloroform, 0.35 g of N-bromosuccinimide was added and reacted for 5 hours under reflux, followed by addition of water and liquid separation to extract the organic phase. The solvent was distilled off to obtain a crude product, which was then purified by silica gel column chromatography to obtain Exemplified Compound 12-4 (0.67 g, 80%).

Synthesis of Exemplified Compound 12 Phys. Chem. Exemplified Compound 12 was synthesized with reference to C 2010, 114, 16843.

Exemplified Compound 12-4; 265 mg and 2,6-bis (trimethyltin) -4,8-didodecyloxybenzo [1,2-b: 4,5-b ′] dithiophene (265 mg, 0.3 mmol) After dissolving in 15 ml of dehydrated toluene and degassing with nitrogen for 30 minutes, Pd (PPh3) 4 (35 mg, 0.03 mmol) was added, and the reaction was carried out for 72 hours under reflux. To further endcap, 2-tributyltin-thiophene (11 mg, 0.03 mmol) was added and refluxed for another 10 hours. Further 2-bromothiophene (10 mg, 0.06 mmol) was added and refluxed for an additional 10 hours. After completion of the reaction, the reaction solution cooled to room temperature was reprecipitated in 150 ml of methanol, and the precipitate was filtered. The obtained precipitate fractionated a high molecular weight component using a gel filtration purification apparatus manufactured by Japan Analytical Industrial Co., Ltd. to obtain a polymer having a number average molecular weight of 30,000 (150 mg, 40%).

(Synthesis of Exemplified Compound 46)

The exemplified compound 11-2 was dissolved in 30 ml of dehydrated THF in a flask purged with 690 mg of nitrogen, and 2.2 ml of 1.0 M lithium diisopropylamide was added dropwise at −78 ° C. and stirred for 30 minutes. Next, 2.5 ml of a 1.0M hexane solution of trimethyltin chloride was added dropwise, followed by further stirring for 30 minutes, followed by stirring overnight at room temperature. After completion of the reaction, ethyl acetate and pure water were added and washed, and the organic layer was extracted. Purification through a thin silica gel pad with an eluent of hexane: triethylamine = 9: 1 gave 1.0 g of Exemplified Compound 46-1 (yield 99%).

In addition, Compound 46-2 was synthesized with reference to Angewante Chemie, Volume 123, Issue 13, pages 3051-3054, March 21, 2011.

In place of this compound 46-1 instead of the exemplified compound 11-3, 305 mg of 2,6-bis (trimethyltin) -4,8-didodecyloxybenzo [1,2-b: 4,5-b ′] dithiophene 340 mg of Exemplified Compound 46 (Mn = 28000) was obtained in the same manner as in the synthesis of Exemplified Compound 11 except that 280 mg (0.3 mmol) was used instead of Exemplified Compound 46-2.

(Synthesis of Exemplified Compound 49)

The exemplified compound 12-3 was dissolved in 30 ml of dehydrated THF in a flask purged with 730 mg of nitrogen, and 2.2 ml of 1.0 M lithium diisopropylamide was added dropwise at −78 ° C. and stirred for 30 minutes. Next, 2.5 ml of a 1.0M hexane solution of trimethyltin chloride was added dropwise, followed by further stirring for 30 minutes, followed by stirring overnight at room temperature. After completion of the reaction, ethyl acetate and pure water were added and washed, and the organic layer was extracted. By purifying through a thin silica gel pad with an eluent of hexane: triethylamine = 9: 1, 1.1 g of Exemplified Compound 49-1 was obtained (yield 99%).

J. Am. Chem. Soc. , 2011, 133 (25), pp 9638 was used as a reference to synthesize Exemplified Compound 49-2.

Instead of Compound 49-1, Exemplified Compound 11-3 was replaced with 372 mg of 2,6-bis (trimethyltin) -4,8-didodecyloxybenzo [1,2-b: 4,5-b ′] dithiophene. 360 mg of Exemplified Compound 49 (Mn = 31000) was obtained in the same manner as in the synthesis of Exemplified Compound 11 except that 305 mg (0.3 mmol) was used instead of Exemplified Compound 49-2.

[N-type semiconductor materials]
The n-type organic semiconductor material used for the photoelectric conversion layer according to the present invention is not particularly limited. Fluoropentacene, perfluorophthalocyanine, etc.), naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide and other aromatic carboxylic acid anhydrides and imidized compounds thereof Examples thereof include polymer compounds.

Among these, as the n-type organic semiconductor material, fullerene derivatives that can efficiently perform charge separation with various p-type semiconductor materials at high speed (up to 50 femtoseconds) are preferable.

Fullerene derivatives include fullerene C ₆₀ , fullerene C ₇₀ , fullerene C ₇₆ , fullerene C ₇₈ , fullerene C ₈₄ , fullerene C ₂₄₀ , fullerene C ₅₄₀ , mixed fullerene, fullerene nanotube, multi-wall nanotube, single-wall nanotube, nanohorn (cone Type), etc., and some of these are hydrogen atoms, halogen atoms, substituted or unsubstituted alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, cycloalkyl groups, silyl groups, ether groups, thioether groups, The fullerene derivative substituted by the amino group, the silyl group, etc. can be mentioned.

Among them, N-methylfullropyrrolidine, [6,6] -phenyl C ₆₁ -butyric acid methyl ester (abbreviated as PCBM), [6,6] -phenyl C ₆₁ -butyric acid-n-butyl ester represented by the following structural formula ( PCBnB), [6,6] -phenyl C ₆₁ -butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C ₆₁ -butyric acid-n-hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, US Pat. No. 7,329,709, etc. Fullerene having a cyclic ether group such as Amer. Chem. Soc. , (2009) vol. 130, p15429, SIMEF, Appl. Phys. Lett. , Vol. 87 (2005), C ₆₀ MC12 described in p203504, etc. It is preferable to use a fullerene derivative having a substituent and having improved solubility as described below.

[Method for forming photoelectric conversion layer]
Examples of a method for forming a photoelectric conversion layer containing a p-type organic semiconductor material and an n-type organic semiconductor material include a vapor deposition method and a coating method (including a casting method and a spin coating method).

Among these, the coating method is preferable in order to increase the area of the interface where charge and electron separation of the above-described holes is performed and to produce a device having high photoelectric conversion efficiency. Also, the coating method is excellent in production speed.

The application method used in this case is not limited, and examples thereof include spin coating, casting from a solution, dip coating, wire bar coating, gravure coating, and spray coating. Furthermore, patterning can also be performed by a printing method such as an ink jet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, or a flexographic printing method.

When coating by such a solution coating method, it is necessary to use a coating liquid composed of three types of p-type semiconductor material, n-type semiconductor material, and solvent for at least the photoelectric conversion layer coating liquid. As the solvent, a solvent capable of dissolving both the p-type semiconductor material and the n-type semiconductor material which are solutes is preferable. As such a solvent, for example, aromatic solvents such as toluene, xylene and tetralin, and halogen solvents such as chloroform, dichloroethane, chlorobenzene, dichlorobenzene and trichlorobenzene are preferable.

The total concentration of the solute in these solvents varies depending on the film thickness to be obtained and the film forming method, but is preferably about 1 to 3% by mass in the spin coating method and the blade coating method. More preferably, the content is 1.5 to 2% by mass. By setting such a dissolution amount, a photoelectric conversion layer having a film thickness of about 100 to 200 nm can be formed by spin coating and blade coating, which are typical film forming methods.

Among these, the mass ratio of the p-type semiconductor and the n-type semiconductor, which are solutes, can be any value such as 1: 4 to 4: 1, but in practice, the mass ratio is about 1: 1 to 1: 2. A value is preferred.

After application, it is preferable to perform heating in order to cause removal of residual solvent, moisture, and gas, and improvement of mobility and absorption of long wave by crystallization of the semiconductor material.

When annealing is performed at a predetermined temperature during the production process, a part of the particles is microscopically aggregated or crystallized, and the photoelectric conversion layer can have an appropriate phase separation structure.

As a result, the mobility of holes and electrons (carriers) in the photoelectric conversion layer is improved, and high efficiency can be obtained.

The photoelectric conversion layer may be composed of a single layer in which a p-type organic semiconductor material and an n-type organic semiconductor material are uniformly mixed. However, the photoelectric conversion layer may be a plurality of layers in which the mixing ratio of the electron acceptor and the electron donor is changed. It may be configured. In this case, it can be formed by using a material that can be insolubilized after application. As a p-type semiconductor material that can be insolubilized after coating, for example, the coating film is polymerized after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Materials that can be insolubilized by crosslinking, or soluble substituents react and insolubilize by applying energy such as heat, as described in US Patent Application Publication No. 2003/136964, and Japanese Patent Application Laid-Open No. 2008-16834 And porphyrin compounds to be pigmented. Examples of the n-type semiconductor material that can be insolubilized after application include Adv. Mater. , Vol. 20 (2008), p2116, phenyl-C61-glycidyl butyrate (PCBG), and the like.

(Electron transport layer)
In the organic photoelectric conversion element of the present invention, by forming an electron transport layer in the middle of the photoelectric conversion layer and the cathode, it becomes possible to more efficiently extract charges generated in the photoelectric conversion layer. It is preferable to have.

In the present invention, the present invention can be particularly preferably applied when the first electrode is a cathode.

The electron transport layer is a layer that is located between the cathode and the bulk heterojunction layer and can more efficiently transfer electrons between the bulk heterojunction layer and the electrode.

More specifically, a compound having an LUMO level intermediate between the LUMO level of the n-type semiconductor material of the bulk heterojunction photoelectric conversion layer and the work function of the cathode is suitable as the electron transporting layer.

More preferably, it is a compound having an electron mobility of 10 ⁻⁴ or more.

In the electron transport layer, the electron transport layer having a HOMO level deeper than the HOMO level of the p-type semiconductor material used in the bulk heterojunction type photoelectric conversion layer includes a hole generated in the bulk heterojunction layer as a cathode. A hole blocking function having a rectifying effect that does not flow to the side is provided.

Such an electron transport layer is also referred to as a hole blocking layer. More preferably, a material having a HOMO level deeper than the HOMO level of the n-type semiconductor is used for the electron transport layer. In addition, in view of the property of blocking holes, it is preferable to use a compound having a hole mobility lower than 10 ⁻⁶ .

As the electron transport layer, octaazaporphyrin, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), carboline compounds described in International Publication No. 04/095889, and the like can be used. The electron transport layer having a HOMO level deeper than the HOMO level of the p-type semiconductor material used for the photoelectric conversion layer has a rectifying effect so that holes generated in the photoelectric conversion layer do not flow to the cathode side. The hole blocking function is imparted. More preferably, a material deeper than the HOMO level of the n-type semiconductor is used as the electron transport layer. Moreover, it is preferable to use a compound with high electron mobility from the characteristic of transporting electrons.

Examples of such materials include phenanthrene compounds such as bathocuproine, n-type semiconductor materials such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and titanium oxide. N-type inorganic oxides such as zinc oxide and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used. Moreover, the layer which consists of a n-type semiconductor material single-piece | unit used for the photoelectric converting layer can also be used.

The means for forming these layers may be either a vacuum vapor deposition method or a solution coating method, but is preferably a solution coating method.

[Hole transport layer (electron blocking layer)]
Since the organic photoelectric conversion element of the present invention can more efficiently extract the charge generated in the photoelectric conversion layer, it may have a hole transport layer between the photoelectric conversion layer and the anode. preferable.

The present invention can be preferably applied when the second electrode is a hole transport layer.

As a material constituting these layers, for example, as a hole transport layer, PEDOT (poly-3,4-ethylenedioxythiophene) -PSS (polystyrene sulfonic acid) manufactured by Starck Vitec, trade name BaytronP, etc., Polyaniline and its doping material, cyan compounds described in International Publication No. 06/019270, and the like can be used. Note that the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the photoelectric conversion layer has a rectifying effect that prevents electrons generated in the photoelectric conversion layer from flowing to the anode side. It has an electronic block function. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function.

As such materials, triarylamine compounds described in JP-A-5-271166, metal oxides such as molybdenum oxide, nickel oxide, and tungsten oxide can be used. Moreover, the layer which consists of a p-type semiconductor material single-piece | unit used for the photoelectric converting layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method. Forming a coating film in the lower layer before forming the photoelectric conversion layer is preferable because it has the effect of leveling the coating surface and reduces the influence of leakage and the like.

Similarly, it is preferable to use a compound having a hole mobility higher than 10 −4 because of the property of transporting holes, and from the property of blocking electrons, the electron mobility is higher than 10 ^−6. It is preferable to use a low compound.

[Other layers]
As a structure of the organic photoelectric conversion element of this invention, it is good also as a structure which has various intermediate | middle layers in an element for the purpose of the improvement of a photoelectric conversion efficiency, and the improvement of element lifetime.

Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

〔electrode〕
The organic photoelectric conversion element of the present invention has the first electrode and the second electrode. When the tandem configuration is adopted, the tandem configuration can be achieved by using the intermediate electrode.

In the present invention, the first electrode is a transparent electrode.

“Transparent” means that the light transmittance is 50% or more.

The light transmittance is the total light in the visible wavelength range measured by a method in accordance with “Testing method of total light transmittance of plastic-transparent material” of JIS K 7361-1: 1997 (corresponding to ISO 13468-1). It refers to transmittance.

As described above, the first electrode of the present invention is preferably a transparent cathode (cathode), and the second electrode is preferably an anode (anode).

[First electrode (transparent cathode)]
Examples of the material used for the first electrode of the present invention include transparent metal oxides such as indium tin oxide (ITO), AZO, FTO, SnO ₂ , ZnO, and titanium oxide, Ag, Al, Au, and Pt. A very thin metal layer, a metal nanowire, a nanowire such as a carbon nanotube or a layer containing nanoparticles, a conductive polymer material such as PEDOT: PSS, polyaniline, or the like can be used.

Also selected from the group consisting of derivatives of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and polynaphthalene. Conductive polymers can also be used. Further, a plurality of these conductive compounds can be combined to form a cathode.

[Second electrode (anode)]
The second electrode may be a single conductive material layer, but in addition to a conductive material, a resin that holds these may be used in combination.

Since the work function of the transparent electrode, which is the cathode, is about −5.0 to −4.0 eV, the built-in potential is necessary for carriers generated in the bulk heterojunction type photoelectric conversion layer to diffuse and reach each electrode. That is, it is preferable that the work function difference between the anode and the cathode is as large as possible.

Therefore, as the conductive material of the anode, a material having a work function (4 eV or less) metal, alloy, electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such an electrode material include gold, silver, copper, platinum, rhodium, indium, nickel, palladium, and the like.

Of these, silver is most preferable from the viewpoint of hole extraction performance, light reflectance, and durability against oxidation.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

In the case where the anode side is made light transmissive, for example, a conductive material suitable for the anode such as aluminum and aluminum alloy, silver and silver compound is made thin with a film thickness of about 1 to 20 nm, and then the transparent electrode A light-transmitting anode can be obtained by providing the conductive light-transmitting material film mentioned in the description.

In the above description, preferred materials for the second electrode material for making a so-called reverse layer type element, which is advantageous for improving the durability, have been described. However, the so-called normal layer type (the first electrode is an anode and the second electrode is a cathode) ), The relationship between the work functions of the first electrode and the second electrode may be reversed as described above, but the types of substantially transparent electrodes are limited, and the work functions are compared. In many cases, a normal layer type organic thin film solar cell can be obtained by using a metal having a shallow work function (less than −4.0 eV) on the second electrode side. Examples of such a metal include aluminum, calcium, magnesium, lithium, sodium, and potassium. In general, aluminum having high reflectivity and high conductivity is used.

[Intermediate electrode]
Further, the material of the intermediate electrode required in the case of the tandem configuration as shown in FIG. 3 is preferably a layer using a compound having both transparency and conductivity. Transparent metal oxides such as ITO, AZO, FTO, SnO ₂ , ZnO and titanium oxide, very thin metal layers such as Ag, Al, Au and Pt, or layers containing nanowires and nanoparticles such as metal nanowires and carbon nanotubes PEDOT: PSS, conductive polymer materials such as polyaniline, etc.) can be used.

In addition, in the hole transport layer and the electron transport layer described above, there is also a combination that works as an intermediate electrode (charge recombination layer) by appropriately combining and laminating. Is preferable.

〔substrate〕
In the present invention, the substrate is a transparent substrate, and the term “transparent” has the same meaning as described above for the electrodes.

As the substrate, for example, a glass substrate, a resin substrate, and the like are preferably used, but it is desirable to use a transparent resin film from the viewpoint of light weight and flexibility. There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things.

For example, polyolefins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester resin film such as modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, cyclic olefin resin, etc. Resin films, vinyl resin films such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin films, polysulfone (PSF) resin films, polyether sulfone (PES) resin films, polycarbonate (PC) resin films , Polyamide resin film, polyimide resin film, acrylic resin film, triacetyl cellulose (TAC) resin film, and the like. If the resin film transmittance of 80% or more at 80 ~ 800 nm), can be preferably applied to a transparent resin film according to the present invention.

Among them, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film. More preferred are a stretched polyethylene terephthalate film and a biaxially stretched polyethylene naphthalate film.

The transparent substrate used in the present invention can be subjected to a surface treatment or an easy adhesion layer in order to ensure the wettability and adhesion of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

Further, for the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

(Optical function layer)
The organic photoelectric conversion element of the present invention may have various optical functional layers for the purpose of more efficient reception of sunlight. As the optical functional layer, for example, a light condensing layer such as an antireflection film or a microlens array, or a light diffusion layer that can scatter light reflected by the cathode and enter the power generation layer again may be provided. .

Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the transmittance can be improved by reducing the interface reflection between the film substrate and the easy adhesion layer. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

As the condensing layer, for example, it is processed to provide a structure on the microlens array on the sunlight receiving side of the support substrate, or the amount of light received from a specific direction is increased by combining with a so-called condensing sheet. Conversely, the incident angle dependency of sunlight can be reduced.

As an example of a microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

Examples of the light scattering layer include various antiglare layers, layers in which nanoparticles or nanowires such as metals or various inorganic oxides are dispersed in a colorless and transparent polymer, and the like.

[Patterning]
The method and process for patterning each electrode, photoelectric conversion layer, hole transport layer, electron transport layer and the like according to the present invention are not particularly limited, and known methods can be appropriately applied.

If it is a soluble material such as a photoelectric conversion layer and a transport layer, only unnecessary portions may be wiped after the entire surface of die coating, dip coating, etc., or patterning is directly performed at the time of coating using a method such as an ink jet method or screen printing. May be.

In the case of an insoluble material such as an electrode material, the electrode can be patterned by a known method such as mask vapor deposition during vacuum deposition or etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

[Solar cell]
The solar cell of this invention has said organic photoelectric conversion element.

The solar cell of the present invention comprises the above-described organic photoelectric conversion element, has a structure in which optimum design and circuit design are performed for sunlight, and optimum photoelectric conversion is performed when sunlight is used as a light source. .

That is, the photoelectric conversion layer has a structure that can be irradiated with sunlight, and when the solar cell of the present invention is configured, the photoelectric conversion layer and each electrode are housed in a case and sealed, Alternatively, it is preferable to seal them entirely with resin.

As a sealing method, it is preferable to seal not only the organic photoelectric conversion element but also an organic electroluminescence element by a known method so that the produced organic photoelectric conversion element does not deteriorate due to oxygen, moisture, etc. in the environment. .

For example, a method of sealing a cap made of aluminum or glass by bonding with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed and an organic photoelectric conversion element are pasted with an adhesive. Method, spin coating of organic polymer material with high gas barrier property (polyvinyl alcohol, etc.), inorganic thin film with high gas barrier property (silicon oxide, aluminum oxide, etc.) or organic film (parylene etc.) are deposited under vacuum. Examples thereof include a method and a method of laminating these in a composite manner.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1: Evaluation of photoelectric conversion efficiency [Preparation of organic photoelectric conversion element 1]
With reference to Japanese Patent Application Laid-Open No. 2009-146981, a reverse layer type organic photoelectric conversion element was produced.

On a glass substrate, an indium tin oxide (ITO) transparent conductive film deposited with a thickness of 110 nm (surface resistivity 13 Ω / □) is patterned to a width of 2 mm using a normal photolithography technique and hydrochloric acid etching, A transparent electrode was formed.

The patterned transparent electrode was cleaned in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried by nitrogen blowing, and finally subjected to ultraviolet ozone cleaning.

Next, the substrate was brought into a glove box, and a 150 mmol / L (liter) TiO _x precursor solution prepared by the following procedure was spin-coated (rotation speed 2000 rpm, rotation time 60 s) on the transparent substrate in a nitrogen atmosphere. A predetermined pattern was wiped off.

Next, the TiO _x precursor was hydrolyzed by being left in the air. Next, the TiO _x precursor was heat-treated at 150 ° C. for 1 hour to obtain a 30 nm TiO _x layer.

(Preparation of TiO _x precursor: sol-gel method)
First, 12.5 ml of 2-methoxyethanol and 6.25 mmol of titanium tetraisopropoxide were placed in a 100 ml three-necked flask and cooled in an ice bath for 10 minutes. Next, 12.5 mmol of acetylacetone was slowly added and stirred in an ice bath for 10 minutes. Next, the mixed solution was heated at 80 ° C. for 2 hours and then refluxed for 1 hour. Finally, it was cooled to room temperature and adjusted to a predetermined concentration (150 mmol / L) using methoxyethanol to obtain a TiO _x precursor. The above steps were all performed in a nitrogen atmosphere.

Next, a bulk heterojunction layer was formed on the TiO _x layer. 0.9% by mass of Comparative Compound 1 as a p-type semiconductor material and 0.9% by mass (total solid content concentration: 1.8% by mass) of PCBM (manufactured by Frontier Carbon, Nano Spectra E100H) as an n-type semiconductor material were dissolved. A solution was prepared, and a solution filtered through a 0.45 μm filter was applied by a blade coater and dried at 100 ° C. for 30 minutes to obtain a photoelectric conversion layer having a dry film thickness of 220 nm. Comparative compound 1 was synthesized based on Non-Patent Document 3.

Next, an organic solvent-based PEDOT: PSS dispersion (Enocoat HC200, manufactured by Kaken Sangyo) was blade coated on the organic semiconductor layer and air-dried to form a hole transport layer having a dry film thickness of 30 nm.

Next, vacuum deposition was performed so that the silver electrode layer had a thickness of about 200 nm on the conductive polymer layer.

Finally, a reverse layer type organic photoelectric conversion element was produced by performing a heat treatment at 150 ° C. for 10 minutes.

The obtained organic photoelectric conversion element 1 is a transparent barrier film GX made of relief printing using a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) under a nitrogen atmosphere (water vapor transmission rate 0.05 g / m 2). / D) and sealed and taken out to the atmosphere.

The obtained organic photoelectric conversion element 1 was sealed and then irradiated with solar simulator (AM1.5G) light at ^an irradiation intensity of 100 mW / cm 2 to measure voltage-current characteristics, and to obtain an initial conversion efficiency. Was measured.

[Production of organic photoelectric conversion elements 2 to 15]
Organic photoelectric conversion elements 2 to 15 were obtained in the same manner as the comparative organic photoelectric conversion element 1 except that the p-type semiconductor material was changed to the material shown in Table 1 in the production of the organic photoelectric conversion element 1.

(Evaluation of conversion efficiency)
1 of solar simulator (AM1.5G filter) is applied to the photoelectric conversion element produced above.
It was irradiated with light having an intensity of 00mW / cm ^2, a superposed mask in which the effective area 4.0 mm ² on the light receiving portion, the short circuit current density Jsc (mA / cm ²⁾ and the open-circuit voltage Voc (V), fill factor (Phil Factor) Each of the four light receiving portions formed on the same element was measured, and the average value was obtained. In addition, the photoelectric conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1.

Formula 1 η (%) = Jsc (mA / cm ² ) × Voc (V) × FF
(Durability evaluation)
Each of the organic photoelectric conversion elements 1 to 15 obtained above is placed on a hot plate maintained at a temperature of 85 ° C. while being irradiated with 1 Sun light, periodically taken and measured for IV characteristics, and an initial photoelectric conversion efficiency of 100 is obtained. The time when the initial efficiency was reduced to 80% was evaluated as LT80 [time]. It means that durability is so favorable that the value of LT80 is large. The results are shown in Table 1.

P: n in the table represents the mass ratio of the p-type semiconductor (polymer) and the n-type semiconductor (PCBM).

As can be seen from Table 1, the compound of the present invention can provide better photoelectric conversion efficiency than the comparative compound in the reverse layer solar cell. Moreover, it turns out that durability can also be improved. In particular, it can be seen that a compound having —COO— introduced has a high effect of improving durability.

Example 2: Durability evaluation About the organic photoelectric conversion elements 8 and 11 produced in Example 1, the following normal layer type | mold elements were produced using the same raw material and composition, respectively.

[Production of Organic Photoelectric Conversion Element 4 ′]
After the same transparent substrate as in Example 1 was washed in the same process, on the ITO film, Baytron P4083 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated so as to have a film thickness of 30 nm. Heat drying at 140 ° C. for 10 minutes in the air.

After this, the substrate was brought into the glove box and worked in a nitrogen atmosphere. First, the substrate was again heat-treated at 140 ° C. for 10 minutes in a nitrogen atmosphere.

As a p-type semiconductor material, 0.6% by mass of the comparative compound 4 and 0.9% by mass of PCBM as an n-type semiconductor material are dissolved in chlorobenzene to prepare a 1.2% by mass chlorobenzene solution. While being filtered through a 45 μm filter, spin coating was performed at 700 rpm for 60 seconds, then at 2200 rpm for 1 second, and left at room temperature for 30 minutes.

Next, the substrate on which the series of organic layers was formed was placed in a vacuum deposition apparatus without being exposed to the atmosphere. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 −3 Pa or less, and then 0.6 nm of lithium fluoride was deposited and 100 nm of aluminum was deposited as a counter electrode. Finally, heating was performed at 120 ° C. for 30 minutes to obtain a comparative organic photoelectric conversion element 8 ′. The deposition rate was 2 nm / second, and the size was 2 mm square.

The obtained organic photoelectric conversion element 4 ′ was obtained by using a transparent barrier film GX (water vapor transmission rate: 0.05 g / mm) using a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) under a nitrogen atmosphere. m2 / d) and sealed and taken out to the atmosphere.

[Production of organic photoelectric conversion element 12 ']
In the production of the organic photoelectric conversion element 4 ′, the organic photoelectric conversion element 12 ′ was produced in the same manner except that the exemplified compound 12 was used instead of the comparative compound 4 as the p-type semiconductor material.

(Evaluation of conversion efficiency)
Photoelectric conversion elements prepared above, was irradiated with light having an intensity of 100 mW / cm ² solar simulator (AM1.5G filter), a superposed mask in which the effective area 4.0 mm ² on the light receiving portion, the short circuit current density Jsc ( The four light-receiving portions formed on the same element were measured for mA / cm ² ), open-circuit voltage Voc (V), and fill factor (fill factor) FF, and the average value was obtained. In addition, the photoelectric conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1.

Formula 1 η (%) = Jsc (mA / cm ² ) × Voc (V) × FF (Durability Evaluation)
Store in a container kept at a temperature of 80 ° C and a humidity of 80%, periodically take it out, measure the voltage-current characteristics, set the initial conversion efficiency as 100, and reduce the time to 80% of the initial efficiency. It was evaluated as LT80.

Comparison of organic photoelectric conversion elements 4 and 12 in Table 2 shows that the compound 12 of the present invention has higher durability. In addition, when the value of LT80 increased at 4 and 4 ′ and the value of LT80 increased at 12 and 12 ′ were compared, the former value using the compound according to the present invention was significantly more durable than the latter value. It can be understood that the effect of the present invention is particularly great in a so-called reverse layer type organic photoelectric conversion element.

This application is based on Japanese Patent Application No. 2011-032923 filed on February 18, 2011, the disclosure content of which is referenced and incorporated as a whole.

DESCRIPTION OF SYMBOLS 10 Organic photoelectric conversion element 11 Board | substrate 12 1st electrode 13 2nd electrode 14 Photoelectric conversion layer 14 '1st photoelectric conversion layer 15 Charge recombination layer 16 2nd photoelectric conversion layer 17 Hole transport layer 18 Electron transport layer

Claims

An organic photoelectric conversion element having a transparent first electrode, a photoelectric conversion layer containing a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode in this order on a transparent substrate, An organic photoelectric conversion element, wherein the photoelectric conversion layer contains a compound having a partial structure represented by the following general formula 1 or general formula 1 ′ as the p-type organic semiconductor material.

(In the formula, each X 1 independently represents —S—, —O—, —NR 2 —, and each Y 1 independently represents —CR 3 ═ or —N═. R 1 -R 3 each independently represents a hydrogen atom, an alkyl group that may have a substituent, a fluorinated alkyl group that may have a substituent, or a cycloalkyl group that may have a substituent. L 1 is independently selected from a single bond, an arylene group, a heteroarylene group, a carbonyl group, —COO—, and —CONR′— (wherein R ′ represents a hydrogen atom or an alkyl group). A represents a divalent acceptor unit, D 1 and D 2 represent a donor unit, and m and n represent an integer of 0 to 2.)
The organic photoelectric conversion device according to claim 1, wherein the unit represented by A in the general formula 1 or 1 'is a nitrogen-containing heteroaromatic ring group.
The organic photoelectric conversion device according to claim 1 or 2, wherein in the general formula 1 or 1 ', the unit represented by A is a condensed polycyclic group in which two or more rings are condensed.
The organic photoelectric conversion element according to claim 3, wherein the general formula 1 is represented by the following general formula 2.

(Wherein, X 2 are each independently, -S -, - O -, - NR 4 -, - CR 5 = CR 5 '-, - CR 6 = N -, - CR A R B -, or —N═N— R 4 , R 5 , R 5 ′ , R 6 , R A and R B each independently represents a hydrogen atom, an alkyl group which may have a substituent, or a substituent. It represents a fluorinated alkyl group that may have or a cycloalkyl group that may have a substituent.)
The organic photoelectric conversion device according to any one of claims 1 to 4, wherein in the general formula 1 or 1 ', the group represented by X 1 is -S-.
The organic photoelectric conversion device according to any one of claims 1 to 5, wherein in the general formula 1 or 1 ', a group represented by Y 1 is -CH =.
The organic photoelectric conversion device according to any one of claims 1 to 6, wherein the group represented by L 1 is -COO-.
The organic photoelectric conversion device according to any one of claims 1 to 7, wherein the compound is a copolymer of a structure represented by the general formula 1 and a structure represented by the following general formula 3.

(In the formula, each R 9 independently has a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, a fluorinated alkyl group which may have a substituent, or a substituent. Good cycloalkyl group, optionally substituted alkoxy group, optionally substituted fluorinated alkoxy group, optionally substituted cycloalkoxy group, optionally substituted alkoxy A carbonyl group, an acyl group that may have a substituent, an alkylaminocarbonyl group that may have a substituent, or an acylamino group that may have a substituent.
The organic photoelectric conversion device according to any one of claims 4 to 8, wherein the compound containing the structural unit represented by the general formula 2 further contains a structure represented by the following general formula 4A or 4B.

In the formula, Y 3 and Y 4 each independently represent —O—, —NR 10 —, —S—, —C (R 11 ) ═C (R 11 ′ ) —, or —N═C (R 12 ) —, wherein each of R 10 to R 12 independently represents a hydrogen atom, an alkyl group which may have a substituent, a fluorinated alkyl group which may have a substituent, or a substituent. Represents an optionally substituted cycloalkyl group,
R 7 and R 8 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 24 carbon atoms, a fluorinated alkyl group having 1 to 24 carbon atoms, or a carbon atom. A cycloalkyl group having 3 to 20 carbon atoms, a fluorinated cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 24 carbon atoms, a fluorinated alkoxy group having 1 to 24 carbon atoms, and 1 to 24 carbon atoms. A fluorinated alkylthio group, an aryl group having 6 to 30 carbon atoms, a fluorinated aryl group having 6 to 30 carbon atoms, a heteroaryl group having 1 to 20 carbon atoms, or a fluorinated heterocycle having 1 to 20 carbon atoms Represents an aryl group.
The organic photoelectric conversion device according to any one of claims 1 to 9, wherein the compound has a number average molecular weight of 15,000 to 50,000.
The organic photoelectric conversion device according to any one of claims 1 to 10, wherein the first electrode is a cathode and the second electrode is an anode.
A solar cell comprising the organic photoelectric conversion device according to any one of claims 1 to 11.