JP2012099632A - Organic photoelectric conversion element, solar battery using the organic photoelectric conversion element, and optical sensor array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar battery and an optical array sensor which use an organic photoelectric conversion element having a high fill factor and photoelectric conversion efficiency, which is a reverse-layer type organic photoelectric conversion element having high photoelectric conversion efficiency and durability.SOLUTION: An organic photoelectric conversion element has at least a first electrode, a bulk hetero junction layer made of a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode on a substrate. The substrate and the first electrode are transparent and the organic photoelectric conversion element includes a structure as the p-type organic semiconductor material represented by a general formula (1) shown below.

Description

  The present invention relates to an organic photoelectric conversion element, a solar cell, and an optical sensor array. More specifically, the present invention relates to a bulk heterojunction type organic photoelectric conversion element, a solar cell using the organic photoelectric conversion element, and an optical array sensor.

  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 widespread use. In addition, since heavy glass must be used for the substrate, reinforcement work is required at the time of installation, which is one of the causes that increase the power generation cost.

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

  Since these bulk heterojunction solar cells are formed by a coating process except for the anode and cathode, it is expected that they can be manufactured at high speed and at low cost, and may solve the above-mentioned problem of power generation cost. . Furthermore, unlike the Si-based solar cells, compound 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 can be formed on a cheap and lightweight plastic substrate. Is done.

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

  Here, the external quantum efficiency (EQE) is a value indicating how many electrons can be generated from one photon of sunlight decomposed into a spectrum, and the fill factor (FF) is the resistance inside the solar cell. 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) x short circuit current density (mA / cm ² ) x 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 a characteristic relating to the fill factor and the external quantum efficiency, mobility of the p-type semiconductor material can be mentioned.

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

  Therefore, having high mobility is one important condition. However, since mobility is generally higher in a crystalline material than amorphous, it is important to select a crystalline p-type semiconductor material. Become. In order to improve the crystallinity of the organic material, it is important that the material be as flat as possible.

  From the above viewpoint, the present inventors paid attention to one material. It paid attention to the nonpatent literature 3 that the organic thin-film solar cell using the low molecular-type p-type organic-semiconductor material containing an isoindigo structure was disclosed. This material has a band gap of 1.65 EV (750 NM) and a LUMO level of -3.8 to -3.9 EV, which is close to the level condition necessary for achieving the photoelectric conversion efficiency of 10%. ing. However, since the fill factor is as low as 0.36 to 0.38, the photoelectric conversion efficiency is only 1.7%.

JP 2009-146981 A

Nature Mat. , Vol. 6 (2007), p497, A.I. Heeger etc. Adv. Mater. 2006, Vol. 18, p789 (CJ Brabec et al.) ORGANIC LETTERS, 2010, Vol. 12, no. 4, p660 (JR Reynolds, etc.) APPLIED PHYSICS LETTERS 89, p143517, NREL Shahen, etc.

  This invention is made | formed in view of the said subject, The objective is the solar which used the organic photoelectric conversion element with a high fill factor and a high photoelectric conversion efficiency in the photoelectric conversion efficiency and the reverse layer type organic photoelectric conversion element with high durability. It is to provide a battery and an optical array sensor.

  The present inventors analyzed the reason why the fill factor is low by using molecular orbital calculation, and as a result, the ketone structure of the isoindigo mother nucleus became a steric hindrance and moved due to taking a twisted structure. The degree was low and it was estimated that the fill factor (FF) might be low.

  Therefore, when searching for a structure that can provide an equivalent level, has no twist, and has high planarity, the compound of the present invention can satisfy these requirements and provide a high fill factor, and thus achieve high photoelectric conversion efficiency. I found out that I can do it.

  In particular, since a stable metal electrode having a deep work function can be used, it is advantageous from the viewpoint of durability, and the so-called reverse layer configuration using the transparent electrode side as a cathode (see Patent Document 1 and Non-Patent Document 4) is transparent. It has been found that the fill factor is likely to be lower than that of a normal layer configuration in which the electrode is an anode, but a high fill factor and photoelectric conversion efficiency can be provided even in such a reverse layer configuration.

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

(1)
An organic photoelectric conversion element having at least a first electrode, a bulk heterojunction layer made of a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode on a substrate,
The substrate and the first electrode are transparent;
And the organic photoelectric conversion element characterized by containing the structure represented by following General formula (1) as said p-type organic-semiconductor material.

(In the formula, X _{1 to} X ₈ represent —CR ₁ ═ or —N═. R ₁ is 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.)
(2)
The p-type organic semiconductor material having a structure represented by the general formula (1) has a number average molecular weight of 15,000 to 50,000, and the organic photoelectric conversion device according to (1).

(3)
A p-type organic semiconductor material having a structure represented by the general formula (1), wherein X ₁ = X ₅ , X ₂ = X ₆ , X ₃ = X ₇ , X ₄ = X ₈ The organic photoelectric conversion device according to (1) or (2), wherein

(4)
A p-type organic semiconductor material having a structure represented by the general formula (1), wherein at least one of X _{1 to} X ₄ and X _{5 to} X ₈ is a nitrogen atom (1 ) Or the organic photoelectric conversion device according to (2).

(5)
The structure represented by the general formula (1) is a structure represented by the following general formula (2), wherein the organic photoelectric conversion device according to any one of (1) to (3) .

(Wherein X _{11 to} X ₁₃ represent —CR ₂ ═ or —N═, and at least one is —N═. R ₂ represents an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, It represents a substituent selected from a heteroaryl group and an alkylsilyl group, and may further have a substituent, or may be bonded to each other to form a ring.
(6)
In the general formula (2), an organic photoelectric conversion device according to, characterized in that X ₁₂ is -N = (5).

(7)
The structure represented by the general formula (2) is a structure represented by the following general formula (3), wherein the organic photoelectric conversion element according to (5) or (6) is characterized.

(In the formula, Z ₁ represents an atom selected from carbon, silicon, and germanium, and R ₃ and R ₄ are selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a substituent, may further have a substituent, and may be bonded to each other to form a ring.)
(8)
In the general formula (3), an organic photoelectric conversion element according to Z ₁ is characterized in that it is a carbon atom (7).

(9)
The p-type organic semiconductor material having the structure of any one of the general formulas (1) to (3) further includes a p-type organic semiconductor material that is a copolymer with the structure represented by the following general formula (4). The organic photoelectric conversion element according to any one of (1) to (8), wherein

(In the formula, Z ₂ represents an atom selected from carbon, silicon, and germanium, and R ₅ or R ₆ is selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a substituent, may further have a substituent, and may be bonded to each other to form a ring.)
(10)
The p-type organic semiconductor material having a structure in which the atom represented by Z ₂ in the general formula (4) is a silicon atom includes the structure according to any one of (1) to (9), Organic photoelectric conversion element.

(11)
The organic photoelectric conversion element according to any one of (1) to (10), wherein the work function of the first electrode is a reverse layer configuration smaller than the work function of the second electrode .

(12)
A solar cell comprising the organic photoelectric conversion element according to any one of (1) to (11).

  According to the present invention, an organic photoelectric conversion element having high photoelectric conversion efficiency and durability, a solar cell using the organic photoelectric conversion element, and an optical array sensor can be provided.

Sectional drawing which shows the solar cell which consists of a bulk heterojunction type organic photoelectric conversion element of a normal layer structure. Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with the photoelectric converting layer of a reverse layer structure. Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with the tandem type photoelectric conversion layer.

  Hereinafter, the present invention will be described in detail.

  The organic photoelectric conversion element of the present invention is characterized in that the photoelectric conversion layer contains a compound having a structure represented by the general formula (1), and the present invention will be described in more detail below.

(Configuration of organic photoelectric conversion element and solar cell)
FIG. 1 is a cross-sectional view illustrating a conventional normal layer type bulk heterojunction type organic photoelectric conversion element. In FIG. 1, a bulk heterojunction type organic photoelectric conversion element 10 includes a transparent electrode (generally an anode) 12, a hole transport layer 17, a photoelectric conversion layer 14, an electron transport layer 18 and a counter electrode (generally, on one surface of a substrate 11. Cathode) 13 is sequentially laminated.

  The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion layer 14, and the counter electrode 13 that are sequentially stacked. In the present embodiment, since light photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light subjected to photoelectric conversion, that is, transparent to the wavelength of the light to be photoelectrically converted. It is an important member. As the substrate 11, for example, a glass substrate or a resin substrate is used. The substrate 11 is not essential. For example, the bulk heterojunction type organic photoelectric conversion element 10 may be configured by forming the transparent electrode 12 and the counter electrode 13 on both surfaces of the photoelectric conversion layer 14.

  The photoelectric conversion layer 14 is a layer that converts light energy into electric energy, and includes a photoelectric conversion layer in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed. 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 transparent electrode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the photoelectric conversion layer of the photoelectric conversion layer 14, and electrons move from the electron donor to the electron acceptor. Thus, a hole-electron pair (charge separation state) is formed. In the case where the generated electric charges have different internal electric fields, for example, when the work functions of the transparent electrode 12 and the counter electrode 13 are different, the electrons pass between the electron acceptors and the holes are between the electron donors due to the potential difference between the transparent electrode 12 and the counter electrode 13. And is carried to different electrodes, and photocurrent is detected.

  Here, since the work function of the transparent electrode 12 is usually larger than that of the counter electrode 13, holes are transported to the transparent electrode 12 and electrons are transported to the counter electrode 13. That is, the counter electrode 13 needs to use a metal having a small work function and easily oxidized. When this metal is oxidized, the electrical properties of the device deteriorate due to the loss of conductivity or, conversely, the work function increases and the correlated contact resistance increases significantly. It was a big factor with low nature.

  Therefore, in the present invention, it is preferable to have a structure of an organic photoelectric conversion element having a reverse layer structure as shown in FIG. That is, the counter electrode 13 is less likely to be oxidized by designing the counter electrode 13 to be larger than the work function of the transparent electrode 12 so as to transport electrons to the transparent electrode 12 and holes to the counter electrode 13. Stable, high work function metals can be used. That is, as described above, the work function relationship is reversed (configuration in which the transparent electrode 12 is a cathode and the counter electrode 13 is an anode), and the positions of the hole transport layer 17 and the electron transport layer 18 in FIG. By using an organic photoelectric conversion element having a reverse layer structure as shown in FIG. 2, deterioration of the element due to oxidation of the counter electrode can be significantly suppressed, and high stability can be provided.

  Although not shown in FIGS. 1 and 2, a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, a smoothing layer, or the like may be included.

  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 transparent electrode 12 and the first photoelectric conversion layer 14 ′ are sequentially stacked on the substrate 11, the charge recombination layer 15 is stacked, the second photoelectric conversion layer 16, and then the counter electrode 13. By stacking layers, a tandem configuration can be obtained. The second photoelectric conversion layer 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion layer 14 'or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. is there.

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

  Below, the material which comprises these layers is described.

[P-type semiconductor materials]
In the present invention, the p-type semiconductor material preferably includes a biindenylidene structure represented by the general formula (1). Such a quinoid structure can provide an acceptor property that is almost equivalent to the isoindigo structure, that is, a deep LUMO level, and can be absorbed to a low band gap material, that is, a long wavelength by copolymerizing with a donor monomer. Can be a material. In addition, unlike an isoindigo structure, since there is no molecular twist, high crystallinity and mobility, that is, high fill factor and photoelectric conversion efficiency can be expected.

_Wherein, X 1 to X ₈ represents -CR ₁ = or -N =. R ₁ 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 may further have a substituent or may be bonded to each other. A ring may be formed.

The alkyl group represented by R ₁ preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. For example, methyl, ethyl, iso-propyl, tert -Butyl, n-octyl, n-decyl, n-hexadecyl, 2-ethylhexyl and the like. These may be fluorinated alkyl groups partially or wholly fluorinated.

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

  The aryl group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, phenanthryl, and pyrenyl. It is done.

  The heteroaryl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom, specifically, for example, imidazolyl, Examples include pyridyl, quinolyl, furyl, piperidyl, benzoxazolyl, benzimidazolyl, benzthiazolyl, thienyl, furyl, pyrrole, thiazolyl and the like.

  The alkylsilyl group preferably has 3 to 15 carbon atoms, and examples thereof include trimethylsilyl, triethylsilyl, triisopropylsilyl, tricyclopentyl, tris (trimethylsilyl) silyl and the like.

  The p-type organic semiconductor material having the structure represented by the general formula (1) is preferably a polymer material. This is because a polymer is more likely to form a continuous domain between p-type semiconductor materials in the power generation layer, and a phase separation of an n-type semiconductor material that is a low-molecular fullerene derivative is easier. From these two points, a polymer material is preferable. As a result, higher short circuit current density and fill factor can be obtained.

  As the molecular weight, the number average molecular weight is preferably at least 5,000 to 500,000. If the molecular weight is lower than this, the effect of improving the above-mentioned fill factor is lowered. If the molecular weight is higher than this, the solubility is low and the productivity may be lowered.

  More preferably, it is 10,000 or more and 100,000 or less, More preferably, it is 15000 or more and 50000 or less.

  The molecular weight can be measured by gel permeation chromatography (GPC). Purification according to molecular weight can also be performed by preparative gel permeation chromatography (GPC).

As a more preferable structure, in order to obtain higher crystallinity, the structure represented by the general formula (1) is preferably a target structure. That is, X ₁ = X ₅ , X ₂ = X ₆ , X ₃ = X ₇ , and X ₄ = X ₈ are preferable.

More preferably, at least one of X _{1 to} X ₄ and X _{5 to} X ₈ is a nitrogen atom. When a part of the biindenylidene structure is substituted with nitrogen, the LUMO level of the polymer becomes deeper and a high open circuit voltage can be provided.

  More preferably, the structure represented by the general formula (1) is preferably a structure represented by the general formula (2).

_Wherein, X 11 _{to X 13} represents -CR ₂ = or -N =, at least one is -N =. R ₂ 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, as in R _1, and may further have a substituent, They may be bonded to each other to form a ring.

  The polymers including the structure represented by the general formula (2) are linear structures, and considering that these are crystallized and packed, nitrogen atoms (-N =) that are electron-withdrawing structures are linear. It is considered that it is more advantageous for the packing to be aligned with the object.

It should be noted that at least one of X _{11 to} X ₁₃ may be a nitrogen atom (-N =), but when two or more are nitrogen atoms, it is ideal for achieving the above-described photoelectric conversion efficiency of 10% or more. It is preferable that one of X _{11 to} X ₁₃ is a nitrogen atom and two are carbon atoms because it tends to be deeper than the typical LUMO level or the band gap becomes too long. Of these it is preferred _{X 12} is -N =.

  More preferably, the structure represented by the general formula (2) is a p-type organic semiconductor material including a structure represented by the following general formula (3).

In the formula, Z ₁ represents an atom selected from carbon, silicon, and germanium, and R _{3 to} R ₄ are similarly selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. And may further have a substituent or may be bonded to each other to form a ring.

  Since such a structure has high planarity and high solubility, it is possible to suppress the restriction of the degree of polymerization due to lack of solubility during the polymerization reaction of the polymer. That is, it is easy to obtain a high molecular weight polymer, and as a result, a high fill factor and photoelectric conversion efficiency can be obtained.

Among these, it is preferable that Z ₁ is a carbon atom and R ₃ and R ₄ are linear alkyl groups.

  The structure represented by the general formulas (1) to (3) becomes a donor-acceptor type polymer by copolymerizing with a donor monomer, and can absorb a target deep LUMO level and a long wavelength. Therefore, the p-type organic semiconductor material of the present invention preferably includes a donor unit together with the structures represented by the general formulas (1) to (3).

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

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

  Specific examples include fluorene, silafluorene, carbazole, dithienocyclopentadiene, dithienosylcyclopentadiene, dithienopyrrole, and benzodithiophene.

  More preferably, it is a structure represented by the general formula (4).

In the formula, Z ₂ represents an atom selected from carbon, silicon, and germanium, and R ₅ or R ₆ is similarly selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. And may further have a substituent or may be bonded to each other to form a ring.

  Since such a structure has high planarity and high solubility, it is possible to suppress the restriction of the degree of polymerization due to lack of solubility during the polymerization reaction of the polymer. That is, it is easy to obtain a high molecular weight polymer, and as a result, a high fill factor and photoelectric conversion efficiency can be obtained.

Among these, it is preferable that Z ₂ is a silicon atom, and R ₃ and R ₄ are linear alkyl groups.

  Hereinafter, although the specific example of the compound which has a structure represented by general formula (1)-(3) and (4) of this invention is given, this invention is not limited to these.

  Compounds having such a structure are described in J. Org. AM. CHEM. SOC. 2009, 131, 14374, US3091568A, DE12892217B or the like can be used as a reference.

  Specifically, it can be synthesized by the following synthesis route.

  As an example, a synthetic route for compound 14 of the present invention is described.

  J. et al. Am. Chem. Soc. Compound 14-1 was synthesized with reference to 1999, 121, 1851. 28.2 g (100 mmol) of dinonyl ketone manufactured by Tokyo Chemical Industry, 31.8 g (30 mmol) of trimethyl orthoformate manufactured by Kanto Chemical, 0.3 g (1.5 mmol) of p-toluenesulfonic acid monohydrate, 250 ml of methanol and tetrahydrofuran (THF) After refluxing 500 ml for 12 hours, 0.3 g (3 mmol) of triethylamine was added to stop the reaction. After allowing to cool, the solution was poured into an ice-cooled saturated aqueous sodium carbonate solution, and the organic phase was extracted with ethyl acetate. The organic phase was dried over magnesium sulfate and then concentrated to obtain dinonyl ketone dimethyl acetal (Compound 14-1). Yield 26.2 g (80%), MS (p) = 329

  Then ORGANIC LETTERS 2004, Vol. 6, no. The compound 14-2 was synthesized with reference to 22, p3981. Into a flask filled with nitrogen, 4.36 g (100 mmol) of sodium hydride (55% oil dispersion) and 10 ml of dehydrated tetrahydrofuran were added, and then 50 ml of dehydrated THF solution containing 6.7 g (100 mmol) of pyrrole was dropped. Stirring was continued for 2 h until hydrogen evolution ceased. Next, 200 ml (100 mmol) of a zinc chloride solution dissolved in dehydrated THF at 0.5 M was added dropwise and stirred for 10 minutes, and then 112 mg (0.5 mmol) of palladium acetate, 150 mg (0.5 mmol) of 2-di-t-butylphosphinobiphenyl. ), And then 6.9 g (33 mmol) of iodothiophene was added and heated at 100 ° C. for 20 hours. After allowing to cool, ethyl acetate is added to extract the organic phase, and the organic phase is dried over magnesium sulfate and then distilled off, and the resulting crude product is purified by silica gel column chromatography to obtain compound 14-2 (2-thienopyrrole). It was. Yield 3.44 g (70%), MS (p) = 150

  J. et al. AM. CHEM. SOC. Compounds 14-3 to 14-4 were synthesized with reference to 2009, 131, 14374. 7.24 g (22 mmol) of Compound 14-1 and 3.0 g (20 mmol) of Compound 14-2 and 0.5 g (2 mmol) of pyridinium p-toluenesulfonic acid were sequentially dissolved in 200 ml of methylene chloride and reacted at room temperature for 24 hours. I let you. After completion of the reaction, ethyl acetate was added and the mixture was filtered through celite, and then the organic phase was extracted. The organic phase was dried over magnesium sulfate and evaporated. The crude product was further dissolved in methylene chloride and purified by silica gel column chromatography to obtain compound 14-3. Yield 8.4 g (75%), MS (p) = 563.

  After dissolving 2.81 g (5 mmol) of Compound 14-3 in 50 ml of dehydrated THF and cooling with liquid nitrogen, 5.6 ml (10 mmol) of 1.8M phenyllithium dibutyl ether solution was added dropwise, and the temperature was returned to room temperature for 2 hours. Stir.

  Separately, a solvent in which 1.58 g (11 mmol) of silver chloride was dispersed in 200 ml of THF was prepared and cooled with liquid nitrogen, and the reaction solution in which the reaction with phenyllithium was completed was dropped. After completion of the dropwise addition, the reaction was continued for 24 hours after returning to room temperature. After completion of the reaction, the reaction solution was filtered through Celite to remove metallic silver, the organic phase was extracted with methylene chloride, dried over magnesium sulfate and evaporated to purify the crude product by silica gel column chromatography. Compound 14-4 was obtained. Yield 0.83 g (30%), MS (p) = 559

  0.56 g (1 mmol) of Compound 14-4 was dissolved in 10 ml of methylene chloride, 0.36 g (2 mmol) of N-bromosuccinimide was added, and the mixture was stirred for 24 hours. After separation with an aqueous KOH solution, the organic phase was extracted and dried over magnesium sulfate, and then the solvent was distilled off to obtain a crude product. The crude product was purified by silica gel column chromatography to give compound 14-5. Yield 0.64 g (90%), MS (p) = 717

  Compound 14-5, 360 mg (0.5 mmol), bis- (5,5′-trimethylstannyl) -3,3′-di-n-hexyl-silylene synthesized by the method described in JP-T 2010-507233 372 mg (0.5 mmol) of -2,2'-dithiophene was dissolved in 20 ml of anhydrous toluene. After purging the solution with nitrogen, 12.55 mg (0.014 mmol) of tris (dibenzylideneacetone) dipalladium (0) and 28.80 mg (0.110 mmol) of triphenylphosphine were added. The solution was purged with nitrogen for an additional 15 minutes. Thereafter, the solution was heated to 110 to 120 ° C. and reacted for 40 hours. After completion of the reaction, the solvent was distilled off, and the resulting residue was washed with methanol (50 ml × 3) and then with acetone (3 × 50 ml).

  The recovered polymer product was heated and dissolved in chloroform (30 ml) and filtered through a 0.45 μm membrane. A 3 ml portion of the solution was loaded on a recycle HPLC (Nihon Analytical Chemical Industries) for purification. The high molecular weight portion was collected to give 120 mg of pure polymer (Mn = 21,000).

[N-type semiconductor materials]
The n-type semiconductor material used in the photoelectric conversion layer according to the present invention is not particularly limited. For example, a perfluoro compound (perfluoropentacene) in which hydrogen atoms of a p-type semiconductor such as fullerene and octaazaporphyrin are substituted with fluorine atoms. And perfluorophthalocyanine), naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide and other aromatic carboxylic acid anhydrides and imidized polymers thereof as a skeleton A compound etc. can be mentioned.

  However, among these, as the n-type semiconductor material, a fullerene derivative capable of efficiently performing charge separation with various p-type semiconductor materials at high speed (up to 50 femtoseconds) is 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 (abbreviated as PCBM), [6,6] -phenyl C61-butyric acid-n-butyl ester (PCBnB) represented by the following structural formula [6,6] -phenyl C61-butyric acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n-hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, US Pat. No. 7,329,709, etc. Fullerene having a cyclic ether group such as Amer. Chem. Soc. , (2009) vol. 130, p15429, SIMEF, Appl. Phys. Lett. , Vol. 87 (2005), C60MC12 described in p203504, etc. It is preferable to use a fullerene derivative having a substituent and having improved solubility as described below.

[Method for forming photoelectric conversion layer]
Examples of the method for forming a photoelectric conversion layer in which an electron acceptor and an electron donor are mixed 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 charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. Also, the coating method is excellent in production speed.

  Although there is no restriction | limiting in the application | coating method used in this case, For example, a spin coat method, the cast method from a solution, a dip coat method, a wire bar coat method, a gravure coat method, a spray coat method etc. are mentioned. 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 coating, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and improvement of mobility and absorption longwave due to crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing 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 an electron acceptor and an electron donor are uniformly mixed, or may be composed of a plurality of layers in which the mixing ratio of the electron acceptor and the electron donor is changed. Good. In this case, it can be formed by using a material that can be insolubilized after coating as described above.

[Electron transport layer (hole blocking layer)]
In the organic photoelectric conversion element of the present invention, by forming an electron transport layer between the photoelectric conversion layer and the cathode, it becomes possible to more efficiently take out the charges generated in the photoelectric conversion layer. It is preferable to have.

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 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, in the electron transport layer having a HOMO level deeper than the HOMO level of the p-type semiconductor material used for the bulk heterojunction layer, holes generated in the bulk heterojunction layer are allowed to flow to the cathode side. A hole blocking function having a rectifying effect 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. Moreover, it is preferable to use the compound whose hole mobility is lower than 10 ^<-6> from the characteristic which blocks a hole.

  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 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 take out charges generated in the photoelectric conversion layer more efficiently. It is preferable.

  As a material constituting these layers, for example, as a hole transport layer, PEDOT (poly-3,4-ethylenedioxythiophene) -PSS (polystyrene sulfonic acid) such as Stark Vitec, trade name BaytronP, 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 a material, a triarylamine compound described in JP-A-5-271166 or a metal oxide such as molybdenum oxide, nickel oxide, or 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]
For the purpose of improving energy conversion efficiency and improving the lifetime of the element, a structure having various intermediate layers in the element may be employed. 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 at least an anode and a cathode. Moreover, when taking a tandem configuration, the tandem configuration can be achieved by using an intermediate electrode. In the present invention, an electrode through which holes mainly flow is called an anode, and an electrode through which electrons mainly flow is called a cathode.

  In addition, the translucent electrode is sometimes referred to as a transparent electrode and the non-translucent electrode is sometimes referred to as a counter electrode because of the function of whether or not it has translucency. In the present invention, from the viewpoint of durability, a reverse layer structure is preferable. In that case, a transparent electrode having translucency is used as a cathode, and a counter electrode having no translucency is used as an anode. In the case of a normal layer configuration, the opposite is true, and a transparent electrode with translucency is used as the anode, and a counter electrode without translucency is used as the cathode.

[Transparent electrode (cathode)]
The transparent electrode of the present invention is preferably an electrode that transmits light of 380 to 800 nm. Examples of the material include transparent metal oxides such as indium tin oxide (ITO), AZO, FTO, SnO ₂ , ZnO, and titanium oxide, very thin metal layers such as Ag, Al, Au, and Pt, metal nanowires, and carbon Nanowires such as nanotubes, layers containing nanoparticles, conductive polymer materials such as PEDOT: PSS, polyaniline, and 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.

[Counter electrode (anode)]
The cathode may be a single layer of a conductive material, 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 as the cathode is about −5.0 to −4.0 eV, the carriers generated in the bulk heterojunction layer diffuse and reach each electrode. It is preferable that the work function difference between the cathodes is as large as possible.

  Therefore, as the conductive material for 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.

  Among these, silver is most preferable from the viewpoints 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.

  When the anode side is made light transmissive, for example, a conductive material suitable for a cathode such as aluminum and an aluminum alloy, silver and a silver compound is made thin with a thickness of about 1 to 20 nm, and then the transparent electrode A light transmissive cathode can be obtained by providing the conductive light transmissive material film mentioned above.

[Intermediate electrode]
The intermediate electrode material required in the case of the tandem structure 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〕
When light that is photoelectrically converted enters from the substrate side, the substrate is preferably a member that can transmit the light that is photoelectrically converted, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. As the substrate, for example, a glass substrate, a resin substrate and the like are preferably mentioned, 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 in from zero to eight hundred nanomolar), 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 adhesiveness 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 interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. 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 so as 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 the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it is smaller than this, the effect of diffraction is generated and colored.

  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 the electrode, the power generation layer, the hole transport layer, the 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 evaporation at the time of vacuum deposition or etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

[Sealing]
Moreover, since the produced organic photoelectric conversion element is not deteriorated by oxygen, moisture, or the like in the environment, it is preferable to seal not only the organic photoelectric conversion element but also an organic electroluminescence element by a known method.

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

  EXAMPLES 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]
A reverse layer type organic photoelectric conversion element was produced.

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

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

Next, the substrate was brought into a glove box, and a 150 mM TiO _x precursor solution prepared by the following procedure was spin-coated (rotation speed 2000 rpm, rotation time 60 s) on the transparent substrate in a nitrogen atmosphere to form a predetermined pattern. Wiping was performed.

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

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

Next, a bulk heterojunction layer was formed on the TiO _x layer. 0.9% by mass of Comparative Compound 1 as a p-type semiconductor material and 0.9% by mass (total solid content concentration: 1.8% by mass) of PCBM (manufactured by Frontier Carbon, Nano Spectra E100H) as an n-type semiconductor material were dissolved. A liquid was prepared, spin-coated at 700 rpm for 60 seconds and then at 2200 rpm for 1 second while being filtered with a 0.45 μm filter, and dried at 100 ° C. for 30 minutes to obtain a photoelectric conversion layer. Comparative compound 1 was synthesized based on Non-Patent Document 3.

  Next, an organic solvent-based PEDOT: PSS dispersion (Enocoat HC200, manufactured by Kaken Sangyo Co., Ltd.) was spin-coated (2000 rpm, 60 s) on the organic semiconductor layer and air-dried to form a hole transport layer.

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

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

[Production of organic photoelectric conversion elements 2 to 4]
In the production of the organic photoelectric conversion element 1, the p-type semiconductor material is changed to the material shown in Table 1, and the p: n ratio is the composition shown in Table 1 (the total solid content concentration is fixed at 1.8% by mass). The organic photoelectric conversion elements 2 to 4 were obtained in the same manner as the comparative organic photoelectric conversion element 1 except that the organic photoelectric conversion elements 2 to 4 were replaced.

  In addition, as P3HT of the organic photoelectric conversion element 4, the plex core OS2100 made from Plectotronics was used.

[Production of organic photoelectric conversion elements 5 to 13]
In the production of the organic photoelectric conversion element 1, the p-type semiconductor material is changed to the material shown in Table 1, and the p: n ratio is the composition shown in the table (the total solid content concentration is fixed at 1.8% by mass). The organic photoelectric conversion elements 5 to 13 were obtained in the same manner as the comparative organic photoelectric conversion element 1 except that 3.0% by mass of 1,8-octanedithiol was further added. In addition, the organic photoelectric conversion elements 12 and 13 use the molecular weight difference of the material used by the organic photoelectric conversion element 11. FIG.

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

Formula 1 η (%) = Jsc (mA / cm ² ) × Voc (V) × FF

  When comparing the organic photoelectric conversion elements 1, 2 and 3 in Table 1, it can be seen that the compound of the present invention has a higher fill factor and higher photoelectric conversion efficiency when compared with the same low molecular weight compound.

  Further, looking at the organic photoelectric conversion elements 5 to 11, when a polymer material is used as the p-type semiconductor material, not only the curve factor becomes higher and high photoelectric conversion efficiency can be obtained, but also the durability is improved. It can be seen that practical durability can be obtained.

  Moreover, when the organic photoelectric conversion elements 11-13 are seen, even if it is a compound with high efficiency, it will be understood that high photoelectric conversion efficiency cannot be obtained unless the molecular weight is appropriate. In addition, the exemplary compound 14 having a molecular weight of 104000 used for the organic photoelectric conversion element 13 was poor in solubility and remained insoluble, and the uniformity of the coating film was low.

Example 2
About the organic photoelectric conversion element 11 produced in Example 1, the following normal layer type | mold elements were produced using the same raw material (Exemplary compound 14 of number average molecular weight 21000) and a composition, respectively, and durability was evaluated.

[Preparation of organic photoelectric conversion element 21]
After the same transparent substrate as in Example 1 was washed in the same process, on the ITO film, Baytron P4083 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated so as to have a film thickness of 30 nm. Heat drying at 140 ° C. for 10 minutes in the air.

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

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

Next, the substrate on which the series of organic layers was formed was placed in a vacuum deposition apparatus without being exposed to the atmosphere. The device was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less. Finally, the heating for 30 minutes was performed at 120 degreeC, and the comparative organic photoelectric conversion element 21 was obtained. The deposition rate was 2 nm / second, and the size was 2 mm square.

The obtained organic photoelectric conversion element 21 is a transparent barrier film GX made of relief printing using a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) under a nitrogen atmosphere (water vapor transmission rate 0.05 g / m). ² · d) and sealed and taken out to the atmosphere.

  After measuring the initial conversion efficiency in the same manner as in Example 1, the following durability evaluation was performed.

(Durability evaluation)
Store in a container maintained at a temperature of 80 ° C and humidity of 80%, periodically take out and measure the voltage-current characteristics, and set the initial conversion efficiency as 100, and reduce the time to 80% of the initial efficiency. It was evaluated as LT80.

  When comparing the organic photoelectric conversion elements 11 and 21 in Table 2, when an organic thin film solar cell is manufactured with the same compound, the normal layer type is slightly more efficient, but the reverse layer type element has higher durability. You can see that

DESCRIPTION OF SYMBOLS 10 Bulk heterojunction type organic photoelectric conversion element 11 Substrate 12 Anode 13 Cathode 14 Photoelectric conversion layer 14 '1st photoelectric conversion layer 15 Charge recombination layer 16 2nd photoelectric conversion layer 17 Hole transport layer 18 Electron transport layer

Claims (12)

An organic photoelectric conversion element having at least a first electrode, a bulk heterojunction layer made of a p-type organic semiconductor material and an n-type organic semiconductor material, and a second electrode on a substrate,
The substrate and the first electrode are transparent;
And the organic photoelectric conversion element characterized by containing the structure represented by following General formula (1) as said p-type organic-semiconductor material.

(In the formula, X _{1 to} X ₈ represent —CR ₁ ═ or —N═. R ₁ is 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 claim 1, wherein the p-type organic semiconductor material having a structure represented by the general formula (1) has a number average molecular weight of 15,000 to 50,000. A p-type organic semiconductor material having a structure represented by the general formula (1), wherein X ₁ = X ₅ , X ₂ = X ₆ , X ₃ = X ₇ , X ₄ = X ₈ The organic photoelectric conversion element according to claim 1, wherein the organic photoelectric conversion element is provided. The p-type organic semiconductor material having a structure represented by the general formula (1), wherein at least one of X _{1 to} X ₄ and X _{5 to} X ₈ is a nitrogen atom. 3. The organic photoelectric conversion element according to 1 or 2. 4. The organic photoelectric conversion device according to claim 1, wherein the structure represented by the general formula (1) is a structure represented by the following general formula (2).

(Wherein X _{11 to} X ₁₃ represent —CR ₂ ═ or —N═, and at least one is —N═. R ₂ represents an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, It represents a substituent selected from a heteroaryl group and an alkylsilyl group, and may further have a substituent, or may be bonded to each other to form a ring. In the general formula (2), an organic photoelectric conversion device according to claim 5, wherein X ₁₂ is -N =. The organic photoelectric conversion element according to claim 6, wherein the structure represented by the general formula (2) is a structure represented by the following general formula (3).

(In the formula, Z ₁ represents an atom selected from carbon, silicon, and germanium, and R ₃ and R ₄ are selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a substituent, may further have a substituent, and may be bonded to each other to form a ring.) In the general formula (3), an organic photoelectric conversion device according to claim 6 or 7, characterized in that Z ₁ is a carbon atom. The p-type organic semiconductor material having the structure of any one of the general formulas (1) to (3) further includes a p-type organic semiconductor material that is a copolymer with the structure represented by the following general formula (4). The organic photoelectric conversion element according to any one of claims 1 to 8, wherein

(In the formula, Z ₂ represents an atom selected from carbon, silicon, and germanium, and R ₅ or R ₆ is selected from an alkyl group, a fluorinated alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, and an alkylsilyl group. Represents a substituent, may further have a substituent, and may be bonded to each other to form a ring.) The organic photoelectric material according to claim 1, comprising a p-type organic semiconductor material having a structure in which the atom represented by Z ₂ in the general formula (4) is a silicon atom. Conversion element.   11. The organic photoelectric conversion element according to claim 1, wherein the first electrode has a reverse layer configuration in which a work function of the first electrode is smaller than a work function of the second electrode.   It consists of the organic photoelectric conversion element of any one of Claims 1-11, The solar cell characterized by the above-mentioned.

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