WO2012099000A1

WO2012099000A1 - Organic photoelectric conversion element and solar cell

Info

Publication number: WO2012099000A1
Application number: PCT/JP2012/050549
Authority: WO
Inventors: 貴宗服部; 大久保　康
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2011-01-18
Filing date: 2012-01-13
Publication date: 2012-07-26
Also published as: JPWO2012099000A1; JP5686141B2

Abstract

[Problem] The purpose of the present invention is to provide an organic photoelectric conversion element having excellent photoelectric conversion efficiency, and a solar cell using the organic photoelectric conversion element. [Solution] Provided is an organic photoelectric conversion element that has, in this order on a transparent substrate, 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. The organic photoelectric conversion element is characterized in that the photoelectric conversion layer contains, as the p-type organic semiconductor material, a compound having a partial structure expressed by general formula (1).

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 Patent Document 1 and Non-Patent Document 1).

In solar cells using these bulk heterojunction type photoelectric conversion elements, it is expected that they can be manufactured at high speed and at low cost because they are formed by a coating process except for the anode and cathode. There is a possibility that it can be solved. Furthermore, unlike the Si-based solar cells, semiconductor-based solar cells, and dye-sensitized solar cells described above, there is no process at a temperature higher than 160 ° C., so that it is expected to be formed on a cheap and lightweight plastic substrate. The

However, in order to reduce the power generation cost, further improvement in efficiency is required. In order to obtain a photoelectric conversion efficiency of 10% or more in the organic thin film solar cell, Non-Patent Document 2 discloses a specific band gap (p-type semiconductor). There is a need for compounds having bg) and LUMO levels.

However, this condition is a necessary condition, and in order to actually achieve a photoelectric conversion efficiency of 10%, it is necessary to satisfy a plurality of conditions. 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. It is a value concerned and 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. In other words, by setting a coefficient called a curve factor, if the irradiation light is sunlight, the efficiency of the solar cell is expressed by the following simple expression.

Photoelectric conversion efficiency (%) = open circuit voltage (V) × short circuit current density (mA / cm ² ) × fill factor (FF)
Since the integration of external quantum efficiency × theoretical Jsc is the short-circuit current density, it can be seen that the external quantum efficiency (EQE) and the fill factor (FF) are very important factors for the efficiency of the solar cell.

As the characteristics relating to the fill factor and the external quantum efficiency, the mobility of the p-type semiconductor material can be mentioned.

In order to obtain high photoelectric conversion efficiency, it is necessary to obtain a high open-circuit voltage. In general, the open-circuit voltage is a difference between the HOMO level of the p-type semiconductor material used for the bulk heterojunction layer and the LUMO level of the n-type semiconductor material. It is said that there is a correlation, and it is considered that a higher open circuit voltage is obtained as the value of the difference is larger.

Further, since it is required to absorb light having a wide wavelength in order to obtain a high short-circuit current, it is considered that a higher short-circuit current can be obtained as the band gap of the p-type semiconductor material is narrower.

It is considered that a suitable morphology is preferably formed in the bulk heterojunction layer in order to obtain higher power generation efficiency.

As materials for organic photoelectric conversion elements, materials containing thienopyrazine compounds are known (see Non-Patent Documents 3 and 4).

However, even in these organic photoelectric conversion elements, the photoelectric conversion efficiency was not sufficient.

International Publication No. 08/066933

This invention is made | formed in view of the said subject, The objective is to provide the organic photoelectric conversion element excellent in photoelectric conversion efficiency, and a solar cell using the same.

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

1. 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 following general formula (1) as the p-type organic semiconductor material.

(Wherein Z ₁ and Z ₂ are each independently a cyano group, a fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN ₂ ] —R ₃ , —C (R ₄ ) ═N—SO ₂ R ₅ , —C (R ₆ ) ═N—CN, represents an alkyl group, an aryl group or an alkoxy group, and represents at least _one of Z ₁ and Z ₂ One is a cyano group, a fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN) ₂ ] —R ₃ , —C (R ₄ ) = N—SO ₂ R ₅ , or —C (R ₆ ) = N—CN.

Z ₁ and Z ₂ may be bonded to each other to form a ring. R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, —OH, —NHR ₇ (R ₇ represents a hydrogen atom or an alkyl group), or monovalent Represents an organic group.

Y ₁ and Y ₂ represent CH or N, and X represents a sulfur, oxygen or selenium atom.

2. 2. The organic photoelectric conversion device as described in 1 above, wherein the compound having the structure represented by the general formula (1) has a number average molecular weight of 15,000 to 50,000.

3. R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ in the general formula (1) are each independently a hydrogen atom, —OH, —NHR ₇ (R ₇ is a hydrogen atom or an alkyl group) The organic photoelectric conversion device as described in 1 or 2 above, wherein the organic photoelectric conversion device is an alkyl group.

4. 4. The organic photoelectric conversion device according to any one of 1 to 3, wherein X in the general formula (1) is a sulfur atom.

5. In the above general formula (1), at least one of Z ₁ and Z ₂ is —C (═O) —OR ₂ (R ₂ represents an alkyl group). The organic photoelectric conversion element of any one of these.

6. 5. The organic photoelectric conversion element as described in any one of 1 to 4, wherein the partial structure represented by the general formula (1) is a partial structure represented by the following general formula (2).

(In the formula, A represents a saturated divalent linking group, Q ₁ and Q ₂ represent oxygen or a biscyanomethylene group. Y ₁ and Y ₂ represent CH or N.)
7. 7. The organic photoelectric conversion device as described in 6 above, wherein in the general formula (2), Y ₁ and Y ₂ represent a nitrogen atom.

8). 8. The organic photoelectric conversion device as described in 6 or 7 above, wherein in the general formula (2), -A- represents -N (R ₁₀ )-(R ₁₀ represents a substituent).

9. 9. The organic photoelectric conversion device as described in 8 above, wherein in the general formula (2), R ₁₀ is an alkyl group having 6 to ₁₀ carbon atoms.

10. In the general formula (2), an organic photoelectric conversion element described in the 8 or 9, characterized in that R ₁₀ is a branched alkyl group.

11. 11. The compound according to any one of 1 to 10 above, wherein the compound having a partial structure represented by the general formula (1) is a compound having a partial structure represented by the following general formula (3): Organic photoelectric conversion element.

(In the formula, Z represents an atom selected from carbon, silicon, and germanium, and R ₁₅ and R ₁₆ represent a substituent selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a group, may further have a substituent, and may be bonded to each other to form a ring.)
12 12. The organic photoelectric conversion device according to any one of 1 to 11, wherein the photoelectric conversion layer is a photoelectric conversion layer produced by a solution coating method.

13. 13. The organic photoelectric conversion element as described in any one of 1 to 12, wherein the first electrode is a cathode.

14. 14. A solar cell comprising the organic photoelectric conversion device as described in any one of 1 to 13 above.

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

It is a schematic sectional drawing which shows the example of a structure of the organic photoelectric conversion element of this invention. It is a schematic sectional drawing which shows the other example of a structure of the organic photoelectric conversion element of this invention. It is a 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 this invention, the compound which has a partial structure represented by the said General formula (1) as a p-type organic-semiconductor material of the bulk heterojunction type photoelectric converting layer containing a p-type organic-semiconductor material and an n-type organic-semiconductor material especially By using this, it is possible to provide an organic photoelectric conversion element having a high fill factor value and high photoelectric conversion efficiency.

(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 of the photoelectric conversion layer 14, and from the electron donor to the electron acceptor. Electrons move and a hole-electron pair (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.

1, since the work function of the first electrode 12 is larger than the work function of the second electrode 13, holes are transported to the first electrode 12 and electrons are transported to the second electrode 13. In this case, a metal having a small work function and easily oxidized is used for the second electrode 13. 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, contrary 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, whereby 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 16. 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 or an electron transport layer 18 may be provided between the first photoelectric conversion layer 14 ′, 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]
The photoelectric conversion layer contains a compound having a partial structure represented by the general formula (1) as a p-type organic semiconductor material.

The compound is an organic compound having semiconductor characteristics. Although it may only have the partial structure of the general formula (1), in order to obtain an organic compound having more preferable semiconductor characteristics as an organic thin film solar cell, it may be a compound having a structure combined with a donor unit described later. preferable.

(Partial structure of general formula (1))
In the general formula (1), X represents an oxygen atom, a sulfur atom or a selenium atom, and Y represents —CH— or —N—.

In the formula, Z ₁ and Z ₂ each independently represent a cyano group, a fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN) ₂ ] -R ₃ , —CR ₄ ═N—SO ₂ R ₅ , —CR ₆ ═N—CN, an alkyl group, an aryl group or an alkoxy group, wherein at least one of Z ₁ and Z ₂ is a cyano group, A fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN) ₂ ] —R ₃ , —CR ₄ ═N—SO ₂ R ₅ , or -CR ₆ = is N-CN.

The fluoroalkyl group in Z ₁ and Z ₂ is an alkyl group in which any one of a straight chain or branched alkyl group having 1 to 20 carbon atoms is substituted with a fluorine atom, and preferably has 1 to 10 carbon atoms. It is an alkyl group in which any hydrogen of a linear alkyl group is substituted with a fluorine atom. Examples of the halogenated alkyl include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropyl group, a 2,2,3,3,4 , 4,4-heptafluorobutyl group, 3,3,4,4,5,5,5-heptafluoropentyl group and the like.

The alkyl group for Z ₁ and Z ₂ is preferably a linear or branched alkyl group having 1 to 20 carbon atoms. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, neopentyl group, 1,2-dimethylpropyl group, n-hexyl group, isohexyl group, 1,3-dimethylbutyl group, 1-isopropylpropyl group, 1,2-dimethylbutyl group, 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-nonyl group, 3,5,5-trimethylhexyl group n-decyl, isodecyl, n-undecyl, 1-methyldecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n- Examples include octadecyl group and n-nonadecyl group.

The aryl group in Z ₁ and Z ₂ preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. For example, a phenyl group, a p-methylphenyl group, Non-condensed hydrocarbon groups such as biphenyl group and terphenyl group; naphthyl group, pentarenyl group, indenyl group, azulenyl group, heptaenyl group, biphenylenyl group, fluorenyl group, acenaphthylenyl group, preadenenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group And condensed polycyclic hydrocarbon groups such as anthryl group, fluoranthenyl group, acephenanthrenyl group, aceantrirenyl group, triphenylenyl group, pyrenyl group, chrycenyl group, and naphthacenyl group.

The alkoxy group (—OR) in Z ₁ and Z ₂ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. For example, n-propoxy group, iso-propyloxy group, n-butoxy group, tert-butoxy group, n-pentyloxy group, n-hexyloxy group, n-octyloxy group, 2-ethylhexyloxy group, n-dodecyl Examples thereof include an oxy group, a tridecyloxy group, a tetradecyloxy group, a pentadecyloxy group, a hexadecyloxy group, a heptadecyloxy group, an octadecyloxy group, and a nonadecyloxy group.

Z ₁ and Z ₂ may be bonded to each other to form a ring.

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, —OH, —NHR ₇ (R ₇ represents a hydrogen atom or an alkyl group), or monovalent Represents an organic group.

As NHR ₇ in R ₁ to R ₆ , R ₇ is a hydrogen atom or an alkyl group. Here, the alkyl group for R ₇ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. Specific examples include the alkyl groups described above. Therefore, as NHR ₇ , for example, amino group, methylamino group, dimethylamino group, diethylamino group, diisopropylamino group, methyl-tert-butylamino group, pentylamino group, dihexylamino group, dioctylamino group, didecylamino group, Examples include dihexadecylamino group, 2-ethylhexylamino group, di2-ethylhexylamino group, di2-hexyldecylamino group, dibenzylamino group and the like.

Examples of the monovalent organic group in R ₁ to R ₆ include alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, acyl group, alkoxycarbonyl group, amino group, alkoxy group, cycloalkyloxy Group, aryloxy group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, silyl group, sulfonyl group, List 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, sulfino group, hydrazino group, imino group, etc. It can be. Among these, an alkyl group, an alkoxy group, an amino group, and a hydroxyl group are preferable. When Z ₁ and Z ₂ do not form a ring, R ₁ to R ₆ are more preferably an alkyl group or an alkoxy group, and particularly preferably an alkyl group.

The alkyl group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. Specifically, the alkyl groups described above are Examples include a methyl group, an ethyl group, an iso-propyl group, a tert-butyl group, an n-octyl group, a 2-ethylhexyl group, an n-decyl group, and an n-hexadecyl group.

The cycloalkyl group in R ₁ to R ₆ preferably has 4 to 8 carbon atoms, and examples thereof include a cyclopentyl group and a cyclohexyl group.

The alkenyl group in R ₁ to R ₆ preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8 carbon atoms. For example, a vinyl group, an allyl group, 2-butenyl group Group, 3-pentenyl group and the like.

The alkynyl group in R ₁ to R ₆ 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 a propargyl group and a 3-pentenyl group. Can be mentioned.

The aryl group in R ₁ to R ₆ preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specifically, the aryl groups described above are Examples thereof include a phenyl group, a p-methylphenyl group, and a naphthyl group.

The heteroaryl group in R ₁ to R ₆ 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, a sulfur atom, Examples thereof include imidazolyl, pyridyl, quinolyl, furyl, piperidyl, benzoxazolyl, benzimidazolyl, benzthiazolyl, thienyl and the like.

The acyl group (—COR) in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, acetyl, propionyl group, Butyryl, isobutyryl, tert-butyryl, pentanoyl, valeryl, isovaleryl, hexanoyl, heptanoyl, octanoyl, decanoyl, dodecanoyl, hexadecanoyl, octadecanoyl, cyclohexanecarbonyl, benzoyl Group, 2-ethylhexylcarbonyl group, 2-hexyldecylcarbonyl group, formyl, pivaloyl and the like.

The alkoxycarbonyl group (—COOR) in R ₁ to R ₆ preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 12 carbon atoms. For example, methoxycarbonyl group, ethoxy Carbonyl group, isopropoxycarbonyl group, tert-butoxycarbonyl group, n-hexyloxycarbonyl group, n-octyloxycarbonyl group, n-decyloxycarbonyl group, n-hexadecyloxycarbonyl group, 2-ethylhexyloxycarbonyl group, Examples include 2-hexyldecyloxycarbonyl group.

The amino group in R ₁ to R ₆ preferably has 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms. Specifically, the amino groups described above are Examples include amino group, methylamino group, dimethylamino group, diethylamino group, pentylamino group, 2-ethylhexylamino group, dibenzylamino group and the like.

The alkoxy group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. Specifically, the alkoxy groups described above are Examples thereof include methoxy group, ethoxy group, n-propoxy group, n-butoxy group and the like.

The cycloalkyloxy group in R ₁ to R ₆ preferably has 4 to 8 carbon atoms, and examples thereof include cyclopentyloxy and cyclohexyloxy.

The aryloxy group in R ₁ to R ₆ preferably has 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, and particularly preferably 6 to 12 carbon atoms. For example, phenyloxy, 2-naphthyloxy and the like Is mentioned.

The aryloxycarbonyl group in the R 1 _~ R _6, preferably 7 to 20 carbon atoms, more preferably having 7 to 16 carbon atoms, particularly preferably having 7-10 carbon atoms, for example, phenyloxycarbonyl and the like .

The acyloxy group in R ₁ to R ₆ preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetoxy and benzoyloxy.

The acylamino group (—NHCOR) in R ₁ to R ₆ preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 10 carbon atoms. For example, acetylamino, benzoylamino Etc.

The alkoxycarbonylamino group in R ₁ to R ₆ preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino and the like. .

The aryloxycarbonylamino group in R ₁ to R ₆ preferably has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino and the like. Can be mentioned.

The sulfonylamino group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, methanesulfonylamino, benzenesulfonylamino, etc. Is mentioned.

The sulfamoyl group for R ₁ to R ₆ preferably has 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, and particularly preferably 0 to 12 carbon atoms, and examples thereof include sulfamoyl, methylsulfamoyl, dimethylsulfamoyl. Famoyl, phenylsulfamoyl and the like can be mentioned.

The carbamoyl group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenyl And carbamoyl.

The alkylthio group in R ₁ to R ₆ 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 methylthio and ethylthio.

The arylthio group in R ₁ to R ₆ 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 in R ₁ to R ₆ 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 in R 1 _- R _6, preferably from 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, e.g., methanesulfinyl, benzenesulfinyl, and the like .

The ureido group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include ureido, methylureido, phenylureido and the like. Can be mentioned.

The phosphoric acid amide group in R ₁ to R ₆ preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, diethylphosphoric acid amide, phenyl phosphorus Examples include acid amides.

Examples of the halogen atom in R ₁ to R ₆ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples thereof include a hydroxy group, a mercapto group, a cyano group, a sulfo group, a carboxyl group, a nitro group, a hydroxamic acid group, a sulfino group, a hydrazino group, and an imino group in R ₁ to R ₆ . These substituents may be further substituted.

In a preferred embodiment of the present invention, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, —OH, —NHR ₇ (R ₇ is a hydrogen atom or an alkyl group) Represents an alkyl group.

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ are preferably a hydrogen atom or an alkyl group, and more preferably an alkyl group, when Z ₁ and Z ₂ do not form a ring.

Z ₁ and Z ₂ are the above substituents (cyano group, fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN) ₂ ] —R ₃ , —C (R ₄ ) ═N—SO ₂ R ₅ , or —C (R ₆ ) ═N—CN), a cyano group, —C (═O) —OR ₂ , —C [ It is preferably selected from the group consisting of ═C (CN) ₂ ] —R ₃ , —C (R ₄ ) ═N—SO ₂ R ₅ , or —C (R ₆ ) = N—CN. Further, when Z ₁ and Z ₂ do not form a ring, among the above substituents, Z ₁ or Z ₂ preferably has a cyano group or —C (═O) —OR ₂ , and Z ₁ More preferably, both Z and Z ₂ are cyano groups, or both Z ₁ and Z ₂ are —C (═O) —OR ₂ .

In the present invention, when Z ₁ and Z ₂ form a ring, Z ₁ and Z ₂ can be represented by —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [ = C (CN) ₂ ] -R ₃ , -C (R ₄ ) = N-SO ₂ R ₅ and -C (R ₆ ) = N-CN are preferably selected. In this case, as —C (═O) —R ₁ , R ₁ is selected from the group consisting of a hydrogen atom, —OH, and —NHR ₇ (R ₇ represents a hydrogen atom or an alkyl group). preferable. More preferably, the two R ₁ groups of Z ₁ and Z ₂ are a combination of a hydrogen atom and —OH, and a combination of a hydrogen atom and NHR ₇ (R ₇ represents an alkyl group). As —C [═C (CN) ₂ ] —R ₃ , R ₃ is selected from the group consisting of a hydrogen atom, —NHR ₇ (R ₇ represents a hydrogen atom or an alkyl group) and an alkyl group. preferable. More preferably, two R ₃ groups of Z ₁ and Z ₂ are a combination of a hydrogen atom and an alkyl group, a combination of an alkyl group and an alkyl group, a hydrogen atom and —NHR ₇ (R ₇ represents an alkyl group), It is a combination. As —C (R ₄ ) ═N—SO ₂ R ₅ , R ₄ and R ₅ are preferably selected from the group consisting of a hydrogen atom or an alkyl group. More preferably, the two R ₄ groups of Z ₁ and Z ₂ are a combination of an alkyl group and an alkyl group. As —C (R ₆ ) ═N—CN, R ₆ is preferably selected from the group consisting of a hydrogen atom and an alkyl group. More preferably, two R ₆ of Z ₁ and Z ₂ is a combination of an alkyl group and an alkyl group. In the present specification, Z ₁ and Z ₂ form a ring means that the carbon (C1) -hydrogen bond of Z ₁ selected from the above substituents and the carbon of Z ₂ selected from the above substituents. It means that (C2) -hydrogen bond forms a ring and becomes a C1-C2 bond.

The thienobenzene and thienopyrazine structures represented by the general formula (1) have a deep HOMO level and a narrow band gap, and an element having a high open-circuit voltage and a short-circuit current can be obtained. More preferred.

In the general formula (1), X is preferably a sulfur atom. When X is a sulfur atom, the conductivity is improved and high mobility is provided.

In the general formula (1), both Z ₁ and Z ₂ are the above cyano group, fluoroalkyl group, —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN ) ₂ ] —R ₃ , —C (R ₄ ) ═N—SO ₂ R ₅ , and —C (R ₆ ) ═N—CN, the compound has a deeper HOMO level.

In the general formula (1), especially Z ₁ and Z ₂ are —C (═O) —R ₁ , —C (═O) —OR ₂ , —C [═C (CN) ₂ ] —R ₃ , —C When (R ₄ ) = N—SO ₂ R ₅ , or —C (R ₆ ) = N—CN, the conjugation of the compound is expanded and stacking between the compounds is increased. Therefore, high mobility is given.

This is because, in the general formula (1), when the thienobenzene ring and the thienopyrazine ring have an electron withdrawing group, but the electron withdrawing groups form a ring structure, the planar structure is further expanded, and high mobility. It is presumed that a high degree of power generation efficiency can be obtained by providing a suitable morphology by increasing the degree of stacking and providing a suitable morphology.

In the general formula (1), when Y is a nitrogen atom, the electron deficiency of the entire ring is improved and the HOMO level becomes deeper.

In the present invention, it is preferable that the partial structure represented by the general formula (1) is a partial structure represented by the following general formula (4).

(In the formula, A represents —CH ₂ CH ₂ —, a connecting group of oxygen atom or nitrogen atom, Q ₁ and Q ₂ are oxygen atoms, ═N (CN), ═N—SO ₂ R ₅ , or C (CN) ₂ is represented, Y ₁ and Y ₂ represent CH or N, and X represents sulfur, oxygen or selenium atom.)
In the present invention, the partial structure represented by the general formula (1) is more preferably a partial structure represented by the general formula (2).

The compound having a partial structure represented by the general formula (4) or (2) in the present invention will be described.

When the electron withdrawing groups are bonded to each other as in the general formula (4) or (2) to form a saturated cyclic skeleton, the stacking ability between the compounds is improved and high mobility is given.

Furthermore, when A represents a nitrogen atom in the general formula (4) or (2), the effect is improved and higher mobility is provided. That is, in the general formula (4) or (2), it is preferable that Y ₁ and Y ₂ represent a nitrogen atom.

Furthermore, as a more preferable form, in the general formula (4) or (2), -A- is represented by -N (R ₁₀ )-(R ₁₀ represents a substituent). In this case, the above effect can be further exhibited. R ₁₀ is a linear or branched alkyl group having 1 to 20 carbon atoms, preferably a linear or branched alkyl group having 6 to 10 carbon atoms, and more preferably a branched alkyl group having 6 to 10 carbon atoms. It is an alkyl group. Specific examples of the alkyl group include the alkyl groups described above, and examples thereof include n-pentyl, n-hexyl, 2-ethylhexyl and the like. Of these, 2-ethylhexyl is preferred.

In addition, when a C6 or higher alkyl group is present on the nitrogen atom, the solubility is improved and a polymer having a high molecular weight is easily obtained when a polymer containing the present compound is prepared. In this case, if the alkyl group is branched, the solubility is further improved, and a compound having a higher molecular weight can be obtained.

The structures represented by the general formulas (1), (4), and (2) are structures generally called acceptors (hereinafter, the partial structure is also referred to as an acceptor unit), and a unit that functions as a donor ( By combining with a donor unit), a narrow band gap material, that is, a material that can efficiently absorb sunlight up to a long wavelength. That is, the compound having a partial structure represented by the general formula (1) of the present invention preferably has an arbitrary donor unit.

As the donor unit, for example, any unit that has a LUMO level or a HOMO level shallower than a hydrocarbon aromatic ring (benzene, naphthalene, anthracene, etc.) having the same π electron number can be used without limitation. it can.

More preferably, a thiophene ring, a furan ring, a pyrrole ring, a hetero 5-membered ring such as cyclopentadiene, silacyclopentadiene, a benzene ring, and a structure containing these as a condensed ring.

Specific examples include fluorene, silafluorene, carbazole, dithienocyclopentadiene, dithienosilacyclopentadiene, dithienopyrrole, benzodithiophene, and structures containing these as condensed rings.

In this embodiment, the donor unit is preferably a compound having a partial structure represented by the following general formula (3), (5), or (6).

More preferred is a structure represented by the above general formula (3) or (5), and further preferred is a structure represented by the above general formula (3).

In general formula (3), Z represents an atom selected from carbon, silicon, and germanium. Of these, carbon and silicon are preferable, and silicon is more preferable. In the general formula (3), R ₁₅ and R ₁₆ each represents a substituent selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group, and further has a substituent. It may be bonded to each other to form a ring. Among these, an alkyl group is particularly preferable and used.

In the general formulas (5) and (6), R ₁₇ , R ₁₈ , R ₁₉ and R ₂₀ are each independently an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an alkoxy group, an aryl group, or a heteroaryl group. Represents a substituent selected from alkylsilyl groups, and may further have a substituent, or may be bonded to each other to form a ring. Among these, an alkyl group and an alkoxy group are preferable, and an alkoxy group is more preferably used.

The alkyl group in R ₁₅ to R ₂₀ is a linear or branched alkyl group having 1 to 20 carbon atoms, preferably a linear alkyl group having 1 to 10 carbon atoms. Specific examples include the alkyl groups described above.

The fluorinated alkyl group for R ₁₅ to R ₂₀ is an alkyl group in which any one of a straight chain or branched alkyl group having 1 to 20 carbon atoms is substituted with fluorine, and preferably has 1 to 10 carbon atoms. Any hydrogen in the linear alkyl group is an alkyl group substituted with fluorine. Specific examples include the fluorinated alkyl groups (fluoroalkyl groups) described above.

The cycloalkyl group in R ₁₅ to R ₂₀ is a cyclic alkyl group having 4 to 8 carbon atoms. Specific examples include the cycloalkyl groups described above.

The aryl group in R ₁₅ to R ₂₀ is an aromatic group having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms. Specific examples include the aryl groups described above.

The heteroaryl group in R ₁₅ to R ₂₀ is a heteroaromatic group having 3 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and the hetero atom is a nitrogen atom, an oxygen atom, or a sulfur atom. Specific examples of the alkylsilyl group in R ₁₅ to R ₂₀ include the heteroaryl groups described above are silyl groups having an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. For example, trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, triisopropylsilyl and the like can be mentioned.
Fluoromethyl, difluoromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl, 2,2,3,3,4,4,4-heptafluorobutyl, 3,3 Examples include 4,4,5,5,5-heptafluoropentyl.

The alkoxy group for R ₁₅ and R ₁₆ is an oxyalkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and more preferably 1 to 8 carbon atoms. Specific examples include the alkoxy groups described above. For example, n-octyloxy, n-dodecyloxy and the like are preferable.

The structure represented by the above general formulas (3) and (5) has a half surface having a larger π-conjugated plane by condensation of a highly mobile thiophene structure, and a substituent capable of imparting solubility. Therefore, both solubility and high mobility can be achieved, and higher photoelectric conversion efficiency can be expected.

Among these, a structure in which the atom represented by Z is a silicon atom is preferable. This is because, as described in AdvMatter 2010p367, when Z is a silicon atom, the crystallinity is high and high mobility tends to be obtained.

In order to give a suitable morphology, it is necessary to have an appropriate molecular weight, and a polymer having a number average molecular weight of 10,000 to 100,000 is preferable, and a polymer having a number average molecular weight of 15,000 to 50,000 is more preferable.

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

Here, the number average molecular weight is 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 number average molecular weight (Mn) was measured. In addition, column elution volume was calibrated by the universal calibration method using Tosoh Corporation standard polystyrene.

Note that in this embodiment, the combination of the acceptor unit exemplified above and the donor unit is not particularly limited, and an arbitrary acceptor unit and any donor unit may be appropriately combined to form a compound (conjugated system). Molecular compounds) can be synthesized and used. In the examples described later, a compound having an acceptor unit and a donor unit is synthesized and its performance is evaluated. However, the technical scope of the present invention is not limited to these examples.

The proportion of the partial structure (1) in the compound having a partial structure according to the present invention is generally preferably 20 to 80% by mass, 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%.

In the present invention, the reason why the photoelectric conversion layer has the compound having the partial structure represented by the general formula (1) to achieve the effect of the present application is not clear, but is estimated as follows.

Although the detailed reason is unknown, it is speculated that the cause is derived from the difference in substituents on the pyrazine ring. The thienopyrazine compounds described in Non-Patent Document 3 and Non-Patent Document 4 do not have an electron withdrawing group. On the other hand, since the partial structure according to the present invention has an electron-attracting group, it is considered that the HOMO level of the compounds is lower than those of the compounds and gives a high open circuit voltage.

Especially, when the electron-withdrawing group of the thienopyrazine ring forms a ring structure, higher efficiency is given. This is considered to be because the planar structure was expanded, the stacking of the compounds increased, and the mobility was improved. Moreover, when it has a substituent with high solubility on the ring structure, the solubility of a compound will improve and the molecular weight at the time of polymerizing can be improved. Also, the solubility of the polymer itself is improved. These points affected the formation of a suitable morphology, and we believe that high power generation efficiency was obtained.

Hereinafter, examples of the compound having a partial structure represented by the general formula (1) will be given, but the present invention is not limited thereto.

In the above compound, it is sufficient that the number represented by n is a value that falls within the above-described molecular weight. For example, n needs to be about 10 to 200 in order to fall within the range of the number average molecular weight of 10,000 to 100,000. There is.

(Synthesis method of the compound according to the present invention)
The compound having the partial structure represented by the general formula (1) can be synthesized as in the following example.

Below, is a _Y 1, _{Y 2} in the general formula (1) is carbon, the compound 301 and _401, is Y 1, _{Y 2,} showing an example of the synthesis of the compounds 607,901,902 is N.

(Synthesis of Exemplified Compound 301)

Exemplified compound 301 is synthesized by a polymerization reaction of the following compound (A) and compound (B).

Synthesis of Compound (A) Compound (A) can be synthesized from compound (C) according to the following route.

Synthesis of Compound (C) J. Org. Chem. Vol. 74, no. 23, 2009, 9181 can be synthesized with reference.

Synthesis of Compound (A) 1.84 g of Compound (C) was taken in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of dichloromethane, and cooled on ice. 3.54 g of N bromosuccinimide was added to the resulting solution and stirred at room temperature for 24 hours. Dichloroethane was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 2.53 g of compound (A).

Synthesis of compound (B)

Compound (B)
Compound (B) can be synthesized with reference to Chemical Communications, 2009, 5570-5572.

Synthesis of Exemplary Compound 301 0.34 g of Compound (A) and 0.86 g of Compound (B) were placed in a 100 ml three-necked flask thoroughly substituted with nitrogen, and 20 ml of nitrogen gas was bubbled in advance into toluene. Dissolved. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.12 g of Exemplified Compound 301.

The molecular weight of Exemplified Compound 301 was measured and found to be Mn = 29000 and PDI (polydispersity index) = 1.8.

(Synthesis of Exemplified Compound 401)

Exemplified compound 401 can be synthesized by a polymerization reaction of the following compound (D) and compound (B).

Synthesis of Compound (D) Compound (D) can be synthesized from compound (E) according to the following route.

Synthesis of compound (E) Org. Chem. Vol. 74, no. 23, 2009, 9181 can be synthesized with reference.

Synthesis of Compound (D) 2.5 g of Compound (E) was taken in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of dichloromethane, and cooled on ice. 3.54 g of N bromosuccinimide was added to the resulting solution and stirred at room temperature for 24 hours. Dichloroethane was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 2.0 g of compound (D).

Synthesis of Compound (B) The compound (B) can be synthesized as described above.

(Synthesis of Exemplary Compound 401)
0.41 g of compound (D) and 0.86 g of compound (B) were placed in a 100 ml three-necked flask thoroughly purged with nitrogen, and dissolved in toluene that had been degassed by bubbling nitrogen gas in advance. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.24 g of Exemplified Compound 401.

The molecular weight of Exemplified Compound 401 was measured and found to be Mn = 31000 and PDI = 2.0.

(Synthesis of Exemplified Compound 607)

Illustrative compound 607 can be synthesized by a polymerization reaction of the following compound (F) and compound (B).

Compound (F) can be synthesized from compound (G) according to the following route.

Synthesis of Compound (G) J. Org. Chem. Vol. 73, no. 21, 2008, 8531 can be used as a reference.
Synthesis of Compound (F) 3.97 g of Compound (G) and 1.74 g of n-octylboronic acid were placed in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of toluene, and cooled on ice. 1.16 g of triphenylphosphine tetrakis palladium was added to the resulting solution, and the mixture was heated to reflux for 12 hours. Toluene was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 3.0 g of compound (F).

(Synthesis of Exemplary Compound 607)
0.43 g of compound (F) and 0.86 g of compound (B) were placed in a 100 ml three-necked flask thoroughly purged with nitrogen, and dissolved in 20 ml of degassed toluene by bubbling nitrogen gas in advance. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.30 g of Exemplified Compound 607.

The molecular weight of Exemplified Compound 607 was measured and found to be Mn = 30000 and PDI = 1.8.

(Synthesis of Exemplified Compound 610)

Illustrative compound 610 can be synthesized by a polymerization reaction of the following compound (H) and compound (B).

Compound (H) can be synthesized from compound (J) according to the following route.

Synthesis of Compound (J) Org. Chem. Vol. 73, no. 21, 2008, 8531 can be used as a reference.

Synthesis of Compound (I) Org. Chem. Vol. 73, no. 21, 2008, 8531 can be synthesized as follows.

Specifically, 2.92 g of compound (J) was taken in a 100 ml three-neck flask purged with nitrogen, dissolved in 50 ml of n-octanol, and cooled on ice. To the obtained solution, 0.65 g of potassium cyanide was added and stirred at 100 degrees for 12 hours. n-Octanol was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 2.26 g of Compound (I).

Synthesis of Compound (H) 2.26 g of Compound (I) was taken in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of dichloromethane, and ice-cooled. 2.76 g of N bromosuccinimide was added to the resulting solution, and the mixture was stirred at room temperature for 24 hours. Dichloroethane was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 2.2 g of compound (H).

(Synthesis of Exemplary Compound 610)
0.45 g of compound (H) and 0.86 g of compound (B) were placed in a 100 ml three-necked flask thoroughly purged with nitrogen, and dissolved in toluene that had been degassed by bubbling nitrogen gas in advance. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.29 g of Exemplified Compound 610.

The molecular weight of Exemplified Compound 610 was measured and found to be Mn = 28000 and PDI = 1.7.

(Synthesis of Exemplified Compound 901)

Example Compound 901 can be synthesized by a polymerization reaction of compound (K) and compound (B).

Compound (K) can be synthesized from compound (N) according to the following synthesis route.

Synthesis of Compound (N) Org. Chem. Vol. 73, no. The compound can be synthesized with reference to 21,20085331.

Synthesis of Compound (M) 1.86 g of Compound (N) was taken in a nitrogen-substituted 100 ml three-neck flask, dissolved in 50 ml of ethanol, and ice-cooled. To the obtained solution, 5.00 g of concentrated hydrochloric acid was added and stirred at room temperature for 24 hours. After completion of the reaction, the mixture was extracted with ethyl acetate and washed with saturated brine. After drying over magnesium sulfate and distilling off the solvent under reduced pressure, 2.10 g of compound (M) was obtained by purification by silica gel column chromatography.

Synthesis of Compound (L) 2.1 g of compound (M) was taken in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of toluene, and ice-cooled. To the resulting solution, 2.21 g of thionyl chloride was added and heated to reflux for 5 hours. Thionyl chloride was distilled off under reduced pressure together with toluene to obtain a yellow solid. This solid was dissolved in 50 ml of dichloromethane and cooled on ice. After 2.87 g of triethylamine was added to the resulting solution, 1.34 g of ethylhexylamine was gradually added and stirred for 5 hours. The organic layer was washed with water and further washed with saturated brine. After drying with magnesium sulfate and distilling off the solvent under reduced pressure, 1.90 g of Compound (L) was obtained by purification by silica gel column chromatography.

Synthesis of Compound (K) 1.90 g of Compound (L) was taken in a nitrogen-substituted 100 ml three-necked flask, dissolved in 50 ml of dichloromethane, and cooled on ice. 2.14 g of N bromosuccinimide was added to the resulting solution and stirred at room temperature for 24 hours. Dichloroethane was distilled off under reduced pressure and purified by silica gel column chromatography to obtain 1.84 g of compound (K).

(Synthesis of Exemplary Compound 901)
0.48 g of compound (K) and 0.86 g of compound (B) were placed in a 100 ml three-necked flask thoroughly purged with nitrogen, and dissolved in toluene that had been degassed by bubbling nitrogen gas in advance. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.38 g of Exemplified Compound 901.

The molecular weight of Exemplified Compound 901 was measured and found to be Mn = 30000 and PDI = 1.8.

(Synthesis of Exemplified Compound 902)

Exemplified compound 902 can be synthesized by a polymerization reaction of the following compound (K) and compound (P).

Synthesis of Compound (K) The compound (K) can be synthesized as described above.

Synthesis of Compound (P) Compound (P) can be synthesized with reference to Patent Document US2010078074.

(Synthesis of Exemplary Compound 902)
0.48 g of compound (K) and 0.77 g of compound (P) were placed in a 100 ml three-necked flask thoroughly purged with nitrogen, and dissolved in 20 ml of degassed toluene by bubbling nitrogen gas in advance. To the resulting solution, 0.12 g of tetrakistriphenylphosphine palladium was added and heated to reflux for 20 hours. After completion of the reaction, the reaction solution was cooled to around room temperature. The reaction solution was added to 200 ml of methanol for reprecipitation, and the precipitate was collected.

The obtained precipitate was dissolved in chloroform and filtered to remove insoluble matters. The resulting chloroform solution was purified by passing through an alumina column. The obtained chloroform solution was concentrated under reduced pressure, added to 200 ml of methanol, and reprecipitated. This precipitate was dried under reduced pressure to obtain 0.33 g of Exemplified Compound 902.

The molecular weight of Exemplified Compound 902 was measured and found to be Mn = 32000 and PDI = 1.9.

[Other p-type semiconductor materials]
In the present invention, as described above, the p-type organic semiconductor material contains a compound having a partial structure represented by the general formula (1), and preferably contains a compound having a structure combined with a donor unit.

Other p-type semiconductor materials may be added in addition to the compound having the partial structure. Examples of other p-type semiconductor materials used for the photoelectric conversion layer include various condensed polycyclic aromatic low molecular compounds and conjugated polymers.

Examples of the condensed polycyclic aromatic low molecular weight compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, circumanthanthene, bisanthene, zeslene. , Heptazethrene, pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, etc., porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene ( BEDTTTTF) -perchloric acid complexes, and derivatives and precursors thereof.

Examples of the derivative having the above condensed polycycle include WO 03/16599 pamphlet, WO 03/28125 pamphlet, US Pat. No. 6,690,029, JP 2004-107216 A. A pentacene derivative having a substituent described in JP-A No. 2003-136964, a pentacene precursor described in US Patent Application Publication No. 2003/136964, and the like; Amer. Chem. Soc. , Vol127. No. 14.4986, J. MoI. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, acene-based compounds substituted with a trialkylsilylethynyl group described in 2706 and the like.

As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and its oligomer, or a technical group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, a polythiophene-thienothiophene copolymer described in WO2008000664, a polythiophene-diketopyrrolopyrrole copolymer described in WO2008000664, a polythiophene-thiazolothiazole copolymer described in Adv Mater, 2007p4160, Nature Mat. vol. 6 (2007), p497 described in PCPDTBT, etc., polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane.

In addition, oligomeric materials, not polymer materials, include thiophene hexamer α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3 Oligomers such as -butoxypropyl) -α-sexithiophene can be preferably used.

In addition, when an electron transport layer or a hole blocking layer is further formed on a photoelectric conversion layer (bulk hetero junction layer) by a solution process, it can be easily laminated if it can be further applied on the layer once applied. However, if a layer is further laminated by a solution process on a layer made of a material having a good solubility, there is a problem that it cannot be laminated because the underlying layer is dissolved. Therefore, the material which can be insolubilized after apply | coating with a solution process may be included.

Examples of such materials include materials that can be insolubilized by polymerizing and crosslinking the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Or a material in which soluble substituents react and become insoluble (pigmented) 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 so on.

[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 C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc. Partially by hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, etc. Examples thereof include substituted fullerene derivatives.

Among them, N-methylfullropyrrolidine, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PC61BM), [6,6] -phenyl C61-butyric acid-n-butyl ester (PC61BnB), [6,6]- Phenyl C61-butyric acid-isobutyl ester (PC61BiB), [6,6] -phenyl C61-butyric acid-n-hexyl ester (PC61BH), [6,6] -phenyl C71-butyric acid methyl ester (abbreviation) PC71BM), 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), C60MC12 described in p203504, etc. It is preferable to use a fullerene derivative having a substituent and having improved solubility as described below.

The junction form of the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer is not particularly limited, and may be a planar heterojunction or a bulk heterojunction. A planar heterojunction is a junction in which a p-type organic semiconductor layer containing a p-type organic semiconductor and an n-type organic semiconductor layer containing an n-type organic semiconductor are stacked, and the surface where these two layers contact is the pn junction interface. It is a form. On the other hand, a bulk heterojunction is formed by applying a mixture of a p-type organic semiconductor and an n-type organic semiconductor. In this single layer, a domain of the p-type organic semiconductor and a domain of the n-type organic semiconductor are formed. It has a microphase separation structure. Therefore, in a bulk heterojunction, many pn junction interfaces exist throughout the layer as compared to a planar heterojunction. Therefore, most of the excitons generated by light absorption can reach the pn junction interface, and the efficiency leading to charge separation can be increased. For these reasons, the junction between the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer is preferably a bulk heterojunction.

In addition, the photoelectric conversion layer (bulk heterojunction layer) is composed of a single layer (i layer) obtained by mixing a normal p-type organic semiconductor material and an n-type organic semiconductor layer. In some cases, it has a three-layer structure (pin structure) sandwiched between a p-layer made of a p-type organic semiconductor and an n-layer made of an n-type organic semiconductor. Such a pin structure has higher rectification of holes and electrons, reduces loss due to charge-separated hole-electron recombination, and can achieve higher photoelectric conversion efficiency. .

In the present invention, the mixing ratio of the p-type organic semiconductor and the n-type organic semiconductor contained in the photoelectric conversion layer is preferably in the range of 2: 8 to 8: 2, more preferably 4: 6 to 6: 4. Range. The film thickness of one photoelectric conversion layer is preferably 50 to 400 nm, more preferably 80 to 300 nm, and particularly preferably 100 to 200 nm. In general, from the viewpoint of absorbing more light, it is preferable that the thickness of the photoelectric conversion layer is larger. However, as the film thickness increases, the extraction efficiency of carriers (holes / electrons) decreases, so the photoelectric conversion efficiency decreases. Tend to. However, when a compound having the partial structure of the formula (1) of the present invention is used as a p-type organic semiconductor material to form a photoelectric conversion layer, it is 100 nm as compared with a photoelectric conversion layer using a conventional p-type organic semiconductor material. Even in the case of the above film thickness, since the extraction efficiency of carriers (holes / electrons) is difficult to decrease, high photoelectric conversion efficiency can be maintained.

[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. That is, the photoelectric conversion layer of the present invention is preferably produced by a solution coating method.

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.

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.

(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, it is particularly preferable and suitable 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.

Such an electron transport layer is also called a hole blocking layer, and it is preferable to use an electron transport layer having such a function. 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)]
The organic photoelectric conversion element of the present invention has a hole transport layer between the photoelectric conversion layer and the anode, and it is possible to extract charges generated in the photoelectric conversion layer more efficiently. It is 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 preferably has a hole mobility higher than 10 ⁻⁴ due to the property of transporting holes, and a compound with electron mobility lower than 10 ⁻⁶ due to the property of blocking electrons. It is preferable to use it.

[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 energy 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 transmittance in the visible light wavelength region measured by a method in accordance with “Testing method of total light transmittance of plastic-transparent material” of JIS K 7361-1 (corresponding to ISO 13468-1). Say.

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 layer containing nanowires such as carbon nanotubes or a nanoparticle, 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 anode 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, potassium, and the like. 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. That is, this invention provides the solar cell which comprises the 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 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 with an adhesive. Method of bonding, spin coating of organic polymer materials with high gas barrier properties (polyvinyl alcohol, etc.), inorganic thin films with high gas barrier properties (silicon oxide, aluminum oxide, etc.) or organic films (parylene, etc.) deposited under vacuum And a method of laminating these in a composite manner.

Note that this application is based on Japanese Patent Application No. 2011-007584 filed on January 18, 2011, the disclosure of which is incorporated by reference in its entirety.

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

Example 1
<< Production of Organic Photoelectric Conversion Element 1 >>
With reference to the description in JP-A-2009-146981, an organic photoelectric conversion element (so-called reverse layer type) was produced as follows.

In addition, AFPO-Green 5 used as a comparative example was synthesized with reference to Non-Patent Document 3.

(Preparation of TiOx layer): Preparation as an electron transport layer Indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 110 nm (surface resistivity 13 Ω / □), ordinary photolithography technology and hydrochloric acid A transparent electrode was formed by patterning to a width of 2 mm using etching.

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 (oxygen concentration 10 ppm, dew point temperature −80 ° C.), and a 150 mM TiOx precursor solution prepared by the following procedure was spin coated (rotation speed 2000 rpm) on the transparent substrate under a nitrogen atmosphere. , Rotation time 60 s), and wiped off in a predetermined pattern.

Next, the TiOx precursor was hydrolyzed by being left in the air, and then the TiOx precursor was heat-treated at 150 ° C. for 1 hour to obtain a 30 nm TiOx layer as an electron transport layer.

(Preparation of TiOx 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 ml) using methoxyethanol to obtain a TiOx precursor. The above steps were all performed in a nitrogen atmosphere.

(Preparation of photoelectric conversion layer)
Next, photoelectric conversion by dissolving AFPO-Green5 as a p-type semiconductor material in 1.0% by mass and PC71BM (manufactured by Frontier Carbon, Nano Spectra E110H) as an n-type semiconductor material in 0.8% by mass in dichlorobenzene. A layer solution was prepared. The photoelectric conversion layer solution is spin-coated so as to have a film thickness of 150 nm after drying while being filtered with a 0.45 μm filter, and dried at room temperature for 30 minutes to obtain a photoelectric conversion layer on the TiOx layer. It was.

(Preparation of hole transport layer)
An organic solvent-based PEDOT: PSS dispersion (Enocoat HC200, manufactured by Kaken Sangyo Co., Ltd.) is spin-coated (2000 rpm, 60 s) on the obtained photoelectric conversion layer (also referred to as an organic semiconductor layer) to form a conductive polymer layer. Filmed and air dried to produce a hole transport layer.

Next, after vacuum-depositing a silver electrode layer on the hole transport layer so as to have a film thickness of about 100 nm, a heat treatment is performed at 150 ° C. for 10 minutes to produce a reverse layer type organic photoelectric conversion element 1. did.

(Evaluation of the organic photoelectric conversion element 1)
Evaluation of the obtained organic photoelectric conversion element 1 was evaluated as a solar cell as follows.

The obtained organic photoelectric conversion element 1 was irradiated with light from a solar simulator (AM1.5G) at an irradiation intensity of 100 mW / cm ² without sealing, and voltage-current characteristics were measured. Voltage), FF (fill factor) and photoelectric conversion efficiency were measured.

<< Preparation of organic photoelectric conversion elements 2-13 >>
Organic photoelectric conversion elements 2 to 13 were prepared in the same manner except that AFPO-Green 5 was changed to the compounds shown in Table 1 in the production of organic photoelectric conversion element 1.

As the compounds 301, 401, 607, 901, and 902, those described above were used. Compounds 201, 203 and 504 were synthesized in the same manner as described above. The molecular weights of the compounds 201, 203, and 504 are shown below. Here, the molecular weight is the number average molecular weight (Mn), and PDI indicates the degree of dispersion (weight average molecular weight / number average molecular weight = Mw / Mn).

The molecular weight of the compound 201 is 28000, PDI = 1.7.
Compound 203 has a molecular weight of 30,000 and PDI = 2.1.
Compound 504 has a molecular weight of 25000 and PDI = 2.0.
(Synthesis of Compound 701)
Compound 701 can be synthesized by changing ethylhexylamine used when compound 901 was synthesized to pentylamine.

The obtained compound 701 had a molecular weight of 35000 and PDI = 2.2.

(Synthesis of Compound 801)
Compound 801 can be synthesized by changing the ethylhexylamine used in the synthesis of compound 901 to hexylamine.

The obtained compound 801 had a molecular weight of 32000 and PDI = 1.9.

(Evaluation of organic photoelectric conversion elements 2 to 13)
The obtained organic photoelectric conversion elements 2 to 13 were evaluated as solar cells as follows.

The obtained organic photoelectric conversion elements 2 to 13 were each sealed with an epoxy resin and a glass cap, and irradiated with solar simulator (AM1.5G) light at an irradiation intensity of 100 mW / cm ² , and voltage-current characteristics. Were measured, and Voc (open circuit voltage), FF (fill factor) and photoelectric conversion efficiency were measured.

From Table 1, compared with the comparative organic photoelectric conversion element 1, the organic photoelectric conversion elements 2 to 13 of the present invention have high Voc (open voltage), FF (curve factor) and photoelectric conversion efficiency, and are excellent as solar cells. It was found to show the characteristics.

10 organic photoelectric conversion elements,
11 substrate,
12 first electrode,
13 Second electrode,
14 photoelectric conversion layer,
14 'first photoelectric conversion layer,
15 charge recombination layer,
16 Second 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, The photoelectric conversion layer contains a compound having a partial structure represented by the following general formula (1) as the p-type organic semiconductor material.

(Wherein Z 1 and Z 2 are each independently a cyano group, a fluoroalkyl group, —C (═O) —R 1 , —C (═O) —OR 2 , —C [═C (CN 2 ] —R 3 , —C (R 4 ) ═N—SO 2 R 5 , —C (R 6 ) ═N—CN, represents an alkyl group, an aryl group or an alkoxy group, and represents at least one of Z 1 and Z 2 One is a cyano group, a fluoroalkyl group, —C (═O) —R 1 , —C (═O) —OR 2 , —C [═C (CN) 2 ] —R 3 , —C (R 4 ) = N—SO 2 R 5 , or —C (R 6 ) = N—CN.
Z 1 and Z 2 may be bonded to each other to form a ring. R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently a hydrogen atom, —OH, —NHR 7 (R 7 represents a hydrogen atom or an alkyl group), or monovalent Represents an organic group.
Y 1 and Y 2 represent CH or N, and X represents a sulfur, oxygen or selenium atom. )
2. The organic photoelectric conversion device according to claim 1, wherein the compound having the structure represented by the general formula (1) has a number average molecular weight of 15,000 to 50,000.
In the general formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently a hydrogen atom, —OH, —NHR 7 (R 7 is a hydrogen atom or an alkyl group) The organic photoelectric conversion device according to claim 1, wherein the organic photoelectric conversion device is an alkyl group.
The organic photoelectric conversion device according to any one of claims 1 to 3, wherein X in the general formula (1) is a sulfur atom.
2. In the general formula (1), at least one of Z 1 and Z 2 is —C (═O) —OR 2 (R 2 represents an alkyl group). 5. The organic photoelectric conversion element according to any one of 4 above.
The organic photoelectric conversion device according to any one of claims 1 to 4, wherein the partial structure represented by the general formula (1) is a partial structure represented by the following general formula (2).

(In the formula, A represents a saturated divalent linking group, Q 1 and Q 2 represent oxygen or a biscyanomethylene group. Y 1 and Y 2 represent CH or N.)
In the general formula (2), an organic photoelectric conversion device according to claim 6, Y 1 and Y 2, characterized in that the representative of the nitrogen atom.
8. The organic photoelectric conversion device according to claim 6, wherein in the general formula (2), -A- represents -N (R 10 )-(R 10 represents a substituent).
In the general formula (2), R 10 is 6 or more carbon atoms, an organic photoelectric conversion device according to claim 8, wherein the alkyl group is 10 or less.
In the general formula (2), an organic photoelectric conversion device according to claim 8 or 9, characterized in that R 10 is a branched alkyl group.
11. The compound according to claim 1, wherein the compound having a partial structure represented by the general formula (1) is a compound having a partial structure represented by the following general formula (3). Organic photoelectric conversion element.

(In the formula, Z represents an atom selected from carbon, silicon, and germanium, and R 15 and R 16 represent a substituent selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a group, may further have a substituent, and may be bonded to each other to form a ring.)
The organic photoelectric conversion element according to any one of claims 1 to 11, wherein the photoelectric conversion layer is a photoelectric conversion layer produced by a solution coating method.
The organic photoelectric conversion device according to any one of claims 1 to 12, wherein the first electrode is a cathode.
A solar cell comprising the organic photoelectric conversion device according to any one of claims 1 to 13.