JP5440208B2 - Organic photoelectric conversion element, solar cell, and optical sensor array - Google Patents

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 sensor array.

  Due to the recent rise in fossil energy, there is a demand for a system that can generate power directly from natural energy. Solar cells using single-crystal / polycrystalline / amorphous Si, compound-based solar cells such as GaAs and CIGS, or Dye-sensitized photoelectric conversion elements (Gretzel cells) have been proposed and put into 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.

  In 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 (n-type) are provided between the anode and the cathode. A bulk heterojunction photoelectric conversion element sandwiching a bulk heterojunction layer mixed with a semiconductor layer) (for example, see Non-Patent Document 1 and Patent Document 1) has been proposed.

  These bulk heterojunction solar cells are formed by a coating process except for the anode and cathode, and are expected to be able to be manufactured at high speed and at low cost. There is. Furthermore, unlike the above Si-based solar cells, compound semiconductor-based solar cells, dye-sensitized solar cells, etc., there is no process at a temperature higher than 160 ° C., so it is expected that it can be formed on a cheap and lightweight plastic substrate. Is done.

  In addition to the initial manufacturing cost, the power generation cost must be calculated including the power generation efficiency and the durability of the element. In Non-Patent Document 1, in order to efficiently absorb the solar spectrum, the power generation cost is about 900 nm. By using a low band gap organic polymer (PCPDTBT) that can absorb up to 6%, conversion efficiency of 6.5% has been achieved.

  On the other hand, the lifetime is low for inorganic solar cells such as silicon, GaAs, and CIGS. Even in the organic photoelectric conversion element of Non-Patent Document 1, it has been reported that the photoelectric conversion efficiency has decreased to about 60% in 100 hours.

  As one of the causes of such a decrease in photoelectric conversion efficiency, the acidic component from PEDOT: PSS of the hole transport layer formed between the transparent electrode and the photoelectric conversion layer (bulk heterojunction layer, BHJ layer) (See Non-Patent Document 2) that the cause is that the metal electrode is diffused and corroded. As a countermeasure, a solution that can be suppressed by converting the hole transport layer from PEDOT: PSS to molybdenum oxide is also shown. However, molybdenum oxide is formed by a vacuum process, and is manufactured at low cost. There is a problem that it is difficult to form a film, and a hole transport layer made of PEDOT: PSS is practically essential.

  In response to such problems, the present inventors cannot suppress the corrosion of the metal electrode by trapping the diffusion component from such a hole transport layer and improve the lifetime of the organic thin film solar cell. I thought.

  In other words, by introducing alkylamino groups and cycloalkylamino groups having high basicity into fullerene derivatives with a high compounding ratio in the photoelectric conversion layer, diffusion of acidic components from these hole transport layers to the metal electrode can be achieved. It was found that the lifetime of the organic photoelectric conversion element can be improved. Such an effect is an effect that cannot be expected with a triarylamine-substituted fullerene as in Non-Patent Document 3, in which an unshared electron pair of an amino group is incorporated into a conjugated system and cannot exhibit basicity.

  In addition, Patent Document 1 discloses a fullerene derivative substituted with an aniline derivative, but there is no description on application to a bulk heterojunction organic photoelectric conversion device by mixing with a conjugated polymer. The life improvement effect cannot be assumed.

  Further, as disclosed in Non-Patent Document 3 and the like, the LUMO level of the fullerene derivative becomes shallow due to the electron donating effect by the amino group, and the open-circuit voltage (Voc) of the organic photoelectric conversion element is improved, thereby improving the photoelectric conversion efficiency. It was also found that improvement can be expected.

JP-A-7-188129

Science, v317 (2008), p222 Molecular Electronics and Bioelectronics, (2008), 19 (4), 231 Chem. Mater. 2009, 21 (13), pp2598.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic photoelectric conversion element that contains a fullerene derivative capable of providing high durability, has a high open-circuit voltage, and has high photoelectric conversion efficiency. It is to provide a solar cell and an optical sensor array.

  The present inventors have found that the amino group-containing fullerene derivative of the present invention is useful as a material for preventing the diffusion of acidic components from the hole transport layer to the metal electrode in order to improve the durability of the organic thin film solar cell. I found it.

  It was also found that some fullerene compounds can further improve the open-circuit voltage (Voc), and can further increase the efficiency.

  That is, the above object of the present invention can be achieved by the following configuration.

  1. An organic photoelectric conversion element comprising an organic layer containing at least a compound represented by the following general formula (1) between a counter electrode and a transparent electrode.

(In the formula, A ₁ represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, R ₁ represents an alkyl group or a cycloalkyl group. R _{2 to} R ₃ each independently represents a hydrogen atom, Or an unsubstituted alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an amino group, an ether group, a thioether group, or a substituent in which a plurality of these are linked, and R _{2 to} R. ₃ may combine with each other to form a ring, and m and n each represent an integer of 1 to 3. A spherical structure to which these substituents are bonded represents a C60 to C540 fullerene structure. )
2. _2. The organic photoelectric conversion device as described in 1 above, wherein R ₂ in the general formula (1) is an alkyl group or a cycloalkyl group.

3. _3. The organic photoelectric conversion device as described in 1 or 2 above, wherein R ₃ in the general formula (1) is an alkyl group or a cycloalkyl group.

  4). 2. The organic photoelectric conversion device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2) or (3).

(In the formula, A ₂ represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, and R _{4 to} R ₇ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, or an alkynyl group. , A cycloalkyl group, an aryl group, a heteroaryl group, an amino group, an ether group, a thioether group, or a substituent in which a plurality of these are connected, and R _{4 to} R ₇ may be bonded to each other to form a ring. N represents an integer of ₁ to _3. L ₁ and L _{2 each} represents a single bond, an alkylene group, an amino group, an ether group, a thioether group, a silylene group, a ketone group, a phosphino group, a phosphoryl group, or a plurality of these. (It represents a divalent linking group selected from substituents, and the spherical structure to which these substituents are bonded represents a C60-C540 fullerene structure.)
5. 5. The organic photoelectric conversion device as described in 4 above, wherein L ₁ or L ₂ of the compound represented by the general formula (2) is an alkylene group.

  6). 2. The organic photoelectric conversion device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (4).

(Wherein, X is a substituted or unsubstituted nitrogen atom, an oxygen atom, a sulfur atom, and _{CR 15 = CR 16 -, -} CR 17 = N -, - N = can form an aromatic ring selected from N- R _{8 to} R ₁₇ each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, heteroaryl group, amino group, or a linking group or a chalcogen atom. A group, an ether group, a thioether group, a ketone group, an ester group, an amide group, or a substituent in which a plurality of these groups are connected, n represents an integer of 1 to 3. In addition, a sphere to which these substituents are bonded Represents a fullerene structure of C60 to C540.)
7). X of the compound represented by the said General formula (4) is -CR < ₁₅ > = CR < ₁₆ >-, The organic photoelectric conversion element of said 6 characterized by the above-mentioned. R _{15, R 16} has the same meaning as _{R 15, R 16} in the general formula (4).

8). 8. The organic photoelectric conversion element as described in 6 or 7 above, wherein R _{9 of the} compound represented by the general formula (4) is an alkyl group.

  9. 9. The organic photoelectric conversion element according to any one of 1 to 8, wherein the organic layer is formed by a solution process.

  10. 1 to 9 above, wherein the organic layer is a bulk heterojunction layer containing a compound represented by any one of the general formulas (1) to (3) and a conjugated polymer material. The organic photoelectric conversion element of any one of Claims 1.

  11. It consists of the organic photoelectric conversion element of any one of said 1-10, The solar cell characterized by the above-mentioned.

  12 The organic photoelectric conversion element of any one of said 1-10 is arrange | positioned at array form, The optical sensor array characterized by the above-mentioned.

  According to the present invention, an organic photoelectric conversion element, a solar cell, and an optical sensor array that contain a fullerene derivative capable of providing high durability, have a high open-circuit voltage, and have high photoelectric conversion efficiency can be provided.

It is sectional drawing which shows the solar cell which consists of a bulk hetero junction type organic photoelectric conversion element. It is sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with a tandem-type bulk heterojunction layer.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

(Configuration of organic photoelectric conversion element and solar cell)
FIG. 1 is a cross-sectional view showing an example of a solar cell having a single configuration (a configuration having one bulk heterojunction layer) composed of a bulk heterojunction type organic photoelectric conversion element. In FIG. 1, a bulk heterojunction type organic photoelectric conversion element 10 includes a transparent electrode (anode) 12, a hole transport layer 17, a photoelectric conversion unit 14 in a bulk heterojunction layer, an electron transport layer (or an electron transport layer) (Also referred to as a buffer layer) 18 and a counter electrode (cathode) 13 are sequentially stacked.

  The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 that are sequentially stacked. In the present embodiment, since light that is photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light that is photoelectrically converted, that is, with respect to the wavelength of the light to be photoelectrically converted. It is a transparent 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 unit 14.

  The photoelectric conversion unit 14 is a layer that converts light energy into electric energy, and includes a bulk heterojunction 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 bulk heterojunction layer of the photoelectric conversion unit 14, and electrons move from the electron donor to the electron acceptor. Thus, a hole-electron pair (charge separation state) is formed. The generated electric charge is caused by an internal electric field, 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 electron donors due to the potential difference between the transparent electrode 12 and the counter electrode 13. The photocurrent is detected by passing through different electrodes to different electrodes. For example, when the work function of the transparent electrode 12 is larger than the work function of the counter electrode 13, electrons are transported to the transparent electrode 12 and holes are transported to the counter electrode 13. If the work function is reversed, electrons and holes are transported in the opposite direction. In addition, by applying a potential between the transparent electrode 12 and the counter electrode 13, the transport direction of electrons and holes can be controlled.

  Although not shown in FIG. 1, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

  Further, for the purpose of further improving the sunlight utilization rate (photoelectric conversion efficiency), a tandem configuration (a configuration having a plurality of bulk heterojunction layers) in which such photoelectric conversion elements are stacked may be used. FIG. 2 is a cross-sectional view showing a solar cell composed of an organic photoelectric conversion element including a tandem type bulk heterojunction layer. In the case of the tandem configuration, the transparent electrode 12 and the first photoelectric conversion unit 14 ′ are sequentially stacked on the substrate 11, the charge recombination layer 15 is stacked, the second photoelectric conversion unit 16, and then the counter electrode 13. By stacking layers, a tandem configuration can be obtained. The second photoelectric conversion unit 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion unit 14 ′ or may be a layer that absorbs a different spectrum. In the tandem organic photoelectric conversion element, When multiple layers generate different amounts of current, the total amount of current is limited to the element with the smallest generated current. Therefore, in order to make the same amount of generated power uniform in each bulk heterojunction layer, preferably different. A layer that absorbs the spectrum is preferable. Examples of different spectral combinations include, for example, a combination in which the first bulk heterojunction layer absorbs sunlight up to 1.9 ev and the second bulk heterojunction layer absorbs sunlight up to 1.3 eV, Or a combination in which the first bulk heterojunction layer absorbs sunlight up to 1.6 ev, the second bulk heterojunction layer absorbs sunlight up to 1.1 eV, and so on.

  Hereinafter, materials that can be used for these layers will be described.

[N-type semiconductor materials]
The organic photoelectric conversion element of the present invention is characterized by having an organic layer containing at least one compound represented by the general formula (1) between the counter electrode and the transparent electrode.

In the general formula (1), A ₁ represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, and R ₁ represents an alkyl group or a cycloalkyl group. R _{2 to} R ₃ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an amino group, an ether group, a thioether group, or a plurality thereof. Represents a linked substituent. R _{2 to} R ₃ may be bonded to each other to form a ring. m and n represent an integer of 1 to 3. The spherical structure to which these substituents are bonded represents a C60 to C540 fullerene structure.

In this way, by using a compound in which at least one substituent for substituting the amino group is an alkyl group or a cycloalkyl group, the basicity of the fullerene derivative is improved, and an acidic component from the hole transport layer is effectively removed. Capturing can prevent oxidation of the metal electrode and deterioration of the organic photoelectric conversion element. More preferably, R _{2 is} also an alkyl group or a cycloalkyl group, and such a dialkylamino group or a dicycloalkylamino group is preferred because the basicity becomes higher. Further, the LUMO level of the fullerene derivative can be made shallower, and the open-circuit voltage (Voc) of the organic photoelectric conversion element can be made higher.

  As the substituted or unsubstituted 5-membered or 6-membered aromatic ring represented by A in the general formula (1), for example, as a 6-membered aromatic ring, benzene, pyridine, pyrimidine, pyridazine, pyrazine, triazine, 5-membered nitrogen-containing heteroaromatic rings such as pyrrole, furan, thiophene, pyrazole, imidazole, triazole, tetrazole, oxazole, thiazole, oxadiazole, thiadiazole, and their condensed rings naphthyl, quinolyl, benzoxazoli , Benzimidazolyl, benzthiazolyl and the like.

  Examples of the fullerene mother nucleus include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, and the like. From the viewpoint of photoelectric conversion efficiency, fullerene C60 and C70 are preferable, and production costs are further increased. From the above viewpoint, fullerene C60 is preferable.

  In the general formula (1), examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an acyl group, an alkoxycarbonyl group, an amino group, an ether group, a thioether group, a ketone group, Examples thereof include an ester group, an amide group, and a substituent in which a plurality of these groups are linked.

  The alkyl group 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 and the like.

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

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

  The cycloalkyl group preferably has 4 to 8 carbon atoms, and examples thereof include cyclopentyl and cyclohexyl.

  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, and naphthyl.

  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 and the like.

  The acyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include acetyl, benzoyl, formyl, and pivaloyl.

  The alkoxycarbonyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonyl and ethoxycarbonyl.

  The amino group preferably has 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms, and examples thereof include amino, methylamino, dimethylamino, diethylamino, dibenzylamino and the like. It is done.

In addition, as a substituent that can further substitute these substituents,
An alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and examples thereof include methoxy, ethoxy, butoxy and the like),
A cycloalkyloxy group (preferably having 4 to 8 carbon atoms, such as cyclopentyloxy, cyclohexyloxy and the like),
An aryloxy group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyloxy and 2-naphthyloxy).
An aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 10 carbon atoms, and examples thereof include phenyloxycarbonyl).
An acyloxy group (preferably having 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);
An acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino);
An alkoxycarbonylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino).
An aryloxycarbonylamino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino).
A sulfonylamino group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include methanesulfonylamino and benzenesulfonylamino).
Sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc. ),
A carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include carbamoyl, methylcarbamoyl, diethylcarbamoyl, and phenylcarbamoyl).
An alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include methylthio and ethylthio);
An arylthio group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenylthio).
A sulfonyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include mesyl and tosyl).
A sulfinyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.),
A ureido group (preferably having 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, and phenylureido).
Phosphoric acid amide group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, and examples thereof include diethyl phosphoric acid amide and phenyl phosphoric acid amide). , Hydroxy group, mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom),
An alkylsilyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include trimethylsilyl and triethylsilyl);
A triarylsilyl group (preferably having 6 to 24 carbon atoms, more preferably 12 to 21 carbon atoms, and particularly preferably 15 to 18 carbon atoms, and examples thereof include triphenylsilyl).
Examples include cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, and the like. These substituents may be further substituted.

  More preferably, the compound represented by the general formula (1) is a compound represented by the general formula (2) or (3).

In General Formula (2) or (3), A ₂ represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, and R _{4 to} R ₇ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl. Represents a group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an amino group, an ether group, a thioether group, or a substituent in which a plurality of these groups are linked. Moreover, it may combine with each other to form a ring. n represents an integer of 1 to 3. L ₁ and L _{2 each} represents a single bond, an alkylene group, an amino group, an ether group, a thioether group, a silylene group, a ketone group, a phosphino group, a phosphoryl group, or a divalent linking group selected from a substituent in which a plurality of these are linked. . The spherical structure to which these substituents are bonded represents a C60 to C540 fullerene structure.

As described above, when the aromatic ring A ₂ and a part of the amino group form a ring structure, even if it is an alkylamino group, the structure can be a relatively rigid structure, and the bulk heterojunction of the fullerene derivative can be obtained. The arrangement and packing in the layer are improved, and high mobility can be expected. As a result, an organic photoelectric conversion element having a high fill factor (FF) and short circuit current (Jsc) can be obtained. From such a viewpoint, a compound in which L ₁ or L _{2 of the} compound represented by the general formula (2) or (3) is an alkylene group is preferable.

  More preferably, the compound represented by the general formula (1) is a compound represented by the general formula (4).

In general formula (4), X is a substituted or unsubstituted nitrogen atom, an oxygen atom, a sulfur atom, and _{CR 15 = CR 16 -, -} CR 17 = N -, - N = an aromatic ring selected from N- It represents a linking group or a chalcogen atom that can be formed. R _{8 to} R ₁₇ are each independently a hydrogen atom or a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, heteroaryl group, amino group, ether group, thioether group, It represents a ketone group, an ester group, an amide group, or a substituent in which a plurality of these groups are linked. n represents an integer of 1 to 3. The spherical structure to which these substituents are bonded represents a C60 to C540 fullerene structure.

  In this way, when a ring structure is formed with carbon atoms bonded to fullerenes, the aromatic ring takes a molecular shape that stands substantially perpendicular to the fullerenes, and is more aligned and packing within the bulk heterojunction layer. Can be improved and high mobility can be expected.

More preferably, it is a compound in which X of the compound represented by the general formula (4) is —CR ₁₅ ═CR ₁₆ — (the aromatic ring is a benzene ring).

In order to achieve both such alignment and solubility, R ₉ is preferably an alkyl group.

  Specific examples of the compounds represented by the general formulas (1) to (4) according to the present invention include the following compounds.

  These compounds are described in J. Org. Org. Chem. , Vol. 60 (1995), p532, or J.I. Med. Chem. , (1965) p566, Non-Patent Document 3, Patent Document 1 and the like.

  The n-type semiconductor material of the present invention can be used by mixing a known n-type semiconductor material for the purpose of controlling crystallization, controlling the phase separation structure, controlling the morphology, and the like. Known n-type semiconductor materials include, for example, fullerene, octaazaporphyrin and the like, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic acid diimide, perylene. Examples thereof include aromatic carboxylic acid anhydrides such as tetracarboxylic acid anhydride and perylenetetracarboxylic acid diimide, and polymer compounds containing the imidized product thereof as a skeleton.

[P-type semiconductor materials]
Examples of the p-type semiconductor material used in the bulk heterojunction layer of the present invention include various condensed polycyclic aromatic low-molecular compounds and conjugated polymers. The tandem organic photoelectric conversion element of the present invention includes two types. Since the bulk heterojunction layer described above is included, it is preferable to use a p-type semiconductor material suitable for each layer.

  Examples of the p-type semiconductor material used for the bulk heterojunction layer of the present invention 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, thacumanthracene, 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-mentioned 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, an acene compound substituted with a trialkylsilylethynyl group described in p2706, and the like.

  As the conjugated polymer, for example, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, polysilane, polygermane, etc. Polythiophene such as poly-3-hexylthiophene (P3HT) and oligomers thereof, or polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225, Nature Materia (200) vol. 5, p328, polythiophene-thienothiophene copolymer, polythiophene-diketopyrrolopyrrole copolymer described in WO2008000664, Adv. Mater. , 2007, p4160, APPLIED PHYSICS LETTERS, vol. 92, p033307 (2008). Am. Chem. Soc. , Vol. 131, p7792 (2009). Among them, in the present invention, Adv., Which is a low band gap polymer having absorption up to a wavelength longer than 650 nm. Mater. , Vol. 19 (2007) p2295, polythiophene-carbazole-benzothiadiazole copolymer (PCDTBT), Nature Mat. , Vol. 6 (2007), p497, a polythiophene copolymer such as PCPDTBT is preferable.

[Method of forming bulk heterojunction layer]
Examples of a method for forming a bulk heterojunction 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. The coating method is also excellent in production speed.

  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 bulk heterojunction layer can have an appropriate phase separation structure. As a result, the carrier mobility of the bulk heterojunction layer is improved and high efficiency can be obtained.

  The photoelectric conversion part (bulk heterojunction layer) 14 may be composed of a single layer in which the electron acceptor and the electron donor are uniformly mixed, but a plurality of the mixture ratios of the electron acceptor and the electron donor are changed. It may consist of layers.

  Next, the electrode which comprises an organic photoelectric conversion element is demonstrated.

  In the organic photoelectric conversion element, positive and negative charges generated in the bulk heterojunction layer are respectively taken out from the transparent electrode and the counter electrode via the p-type organic semiconductor material and the n-type organic semiconductor material, respectively. It functions as. Each electrode is required to have characteristics suitable for carriers passing through the electrode.

[Counter electrode]
In the present invention, the counter electrode (cathode) means an electrode for taking out electrons. For example, when used as a counter electrode, the conductive material may be a single layer, but in addition to a conductive material, a resin that holds these may be used in combination.

  The counter electrode material is required to have sufficient conductivity, a work function close to the extent that no Schottky barrier is formed when bonded to the n-type semiconductor material, and no deterioration. That is, it is preferably a metal having a work function 0 to 0 to 3 eV deeper than the LUMO of the n-type semiconductor material used for the bulk heterojunction layer, and the n-type semiconductor used for the second bulk heterojunction layer of the present invention. Since the preferable LUMO level of the material is −4.3 to −4.6 eV, the work function is preferably −4.3 to −4.9 eV. On the other hand, it is not preferable that the work function is deeper than that of the transparent electrode (anode) for extracting holes, and an interlayer resistance may be generated in a metal having a work function shallower than that of the n-type semiconductor material. A metal having a work function of ˜−4.8 eV is preferable. Therefore, aluminum, gold, silver, copper, indium, or oxide materials such as zinc oxide, ITO, and titanium oxide are also preferable. More preferably, they are aluminum, silver, and copper, More preferably, it is silver.

  The work function of these metals can be similarly measured using ultraviolet photoelectron spectroscopy (UPS).

An alloy may be used if necessary. For example, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, and aluminum are preferable. It is. The counter electrode 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.

  Further, when the counter electrode side is made light transmissive, for example, a conductive material suitable for the counter electrode 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 conductive light is used. By providing a film of a transmissive material, a light transmissive counter electrode can be obtained.

[Transparent electrode]
In the present invention, the transparent electrode means an electrode for extracting holes. For example, when used as a transparent electrode, it is preferably an electrode that transmits light of 380 to 800 nm. As the material, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires and carbon nanotubes 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. A plurality of these conductive compounds can be combined to form a transparent electrode.

[Intermediate electrode]
The intermediate electrode material required in the case of the tandem structure is preferably a layer using a compound having both transparency and conductivity, and the materials (ITO, AZO, FTO, etc.) used in the transparent electrode , Transparent metal oxides such as titanium oxide, very thin metal layers such as Ag, Al, Au, or layers containing nanoparticles / nanowires, conductive polymer materials such as PEDOT: PSS, polyaniline, etc.) Can do.

  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, and with such a configuration, the process of forming one layer This is preferable because it can be omitted.

  Next, materials constituting components other than the electrode and the bulk heterojunction layer will be described.

[Hole Transport Layer / Electron Blocking Layer]
In the organic photoelectric conversion element 10 of the present invention, a hole transport layer 17 is provided between the bulk heterojunction layer and the transparent electrode, and charges generated in the bulk heterojunction layer can be taken out more efficiently. Therefore, it is preferable to have these layers.

  As a material constituting these layers, for example, as the hole transport layer 17, PEDOT such as trade name BaytronP, polyaniline and its doping material, manufactured by Stark Vitec Co., Ltd., described in WO 06/019270, etc. Cyanide compounds of the above can be used. Note that electrons generated in the bulk heterojunction layer do not flow to the transparent electrode side in the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the bulk heterojunction layer. An electronic block function having such a rectifying effect is provided. 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 bulk heterojunction 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 the coating film in the lower layer before forming the bulk heterojunction layer is preferable because it has the effect of leveling the coating surface and reduces the influence of leakage and the like.

[Electron transport layer, hole blocking layer, buffer layer]
In the organic photoelectric conversion element 10 of the present invention, an electron transport layer 18 is formed between the bulk heterojunction layer and the counter electrode, so that charges generated in the bulk heterojunction layer can be taken out more efficiently. Therefore, it is preferable to have these layers.

  As the electron transport layer 18, octaazaporphyrin, a p-type semiconductor perfluoro compound (perfluoropentacene, perfluorophthalocyanine, etc.) can be used. Similarly, a p-type semiconductor used for a bulk heterojunction layer. The electron transport layer having a HOMO level deeper than the HOMO level of the material is provided with a hole blocking function having a rectifying effect that prevents holes generated in the bulk heterojunction layer from flowing to the counter electrode side. The 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. An n-type inorganic oxide such as zinc oxide or gallium oxide, a layer made of a single n-type semiconductor material used for the bulk heterojunction layer, or the like can also be used.

  Alternatively, an alkali metal compound such as lithium fluoride, sodium fluoride, cesium fluoride, or the like can be used.

  Among these, it is preferable to use an alkali metal compound that has a function of further doping an organic semiconductor molecule and improving electrical junction with the metal electrode (cathode). In the case of an alkali metal compound layer, it may be called a buffer layer.

[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.

〔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, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~800nm), can be preferably applied to a transparent resin film according to the present invention. Among these, 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, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  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.

  In order to suppress permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate.

(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, an antireflection film, a condensing layer such as a microlens array, a light diffusion layer that can scatter the light reflected by the counter electrode and enter the bulk heterojunction layer again, etc. May be.

  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 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.

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

Example 1
As a p-type material for the bulk heterojunction layer, a low bandgap polymer having absorption up to about 900 nm, PCPDTBT, was synthesized and used with reference to Non-Patent Document 1 and Macromolecules 2007, 40, 1981. As the n-type material, PCBM (purchased from Frontier Carbon), TPA-PCBM (synthesized according to Non-Patent Document 3), and the fullerene derivative of the present invention were used.

[Production of Organic Photoelectric Conversion Element 1]
A transparent electrode was formed by patterning an indium tin oxide (ITO) transparent conductive film having a thickness of 140 nm on a glass substrate to a width of 2 mm using a normal photolithography technique and hydrochloric acid etching.

  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. On this transparent substrate, Baytron P4083 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated with a film thickness of 60 nm, and then heat-dried at 140 ° C. for 10 minutes in the air.

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

  As a p-type semiconductor material, 1.0 mass% of PCPDTBT is added to chlorobenzene, 2.0 mass% of PCBM (manufactured by Frontier Carbon, NANOM SPECTRA E100H) as an n-type semiconductor material, and 2.4 of 1,8-octanedithiol. A liquid in which mass% was dissolved was prepared, spin-coated at 1200 rpm for 60 seconds while being filtered through a 0.45 μm filter, and dried at room temperature for 30 minutes to obtain a photoelectric conversion layer.

Next, the substrate on which the organic layer was formed was placed in a vacuum evaporation apparatus. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 0.5 nm of lithium fluoride and 80 nm of Al were evaporated. Finally, the heating for 30 minutes was performed at 120 degreeC, and the comparative organic photoelectric conversion element 1 was obtained. The vapor deposition rate was 2 nm / second for all, and the size was 2 mm square.

  The obtained organic photoelectric conversion element 1 was sealed using an aluminum cap and a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) in a nitrogen atmosphere.

[Preparation of organic photoelectric conversion elements 2 to 10]
In the production of the organic photoelectric conversion element 1, the organic photoelectric conversion elements 2 to 10 were prepared in the same manner as the organic photoelectric conversion element 1 except that PCBM was changed to the comparative compounds described in Table 1 and the exemplary compounds of the present invention. Obtained.

  The obtained organic photoelectric conversion elements 2 to 10 were sealed using an aluminum cap and a UV curable resin in a nitrogen atmosphere in the same manner as the organic photoelectric conversion element 1 described above.

[Evaluation of organic photoelectric conversion elements]
(Evaluation of photoelectric conversion efficiency and open circuit voltage Voc)
The organic photoelectric conversion device 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 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 average values were obtained. Further, energy conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1.

Formula 1 Jsc (mA / cm ² ) × Voc (V) × FF = η (%)
(Measurement of durability LT80)
The produced organic photoelectric conversion element is stored in a constant temperature bath at 65 ° C. and 85% RH, returned to room temperature every 10 hours, and measured for photoelectric conversion efficiency. The photoelectric conversion efficiency is 80% of the initial photoelectric conversion efficiency. The measured time was LT80, which was used as a standard for durability evaluation.

  The evaluation results are shown in Table 1.

  From Table 1, the organic photoelectric conversion element of the present invention using the fullerene derivative according to the present invention is an organic photoelectric conversion element having higher durability, higher open-circuit voltage, and higher photoelectric conversion efficiency than the comparative example. I understand that.

10 Bulk heterojunction organic photoelectric conversion element 11 Substrate 12 Transparent electrode (anode)
13 Counter electrode (cathode)
14 Photoelectric conversion part (bulk heterojunction layer)
14 '1st photoelectric conversion part (bulk heterojunction layer)
15 Charge recombination layer 16 Second photoelectric conversion part (bulk heterojunction layer)
17 Hole transport layer 18 Electron transport layer

Claims (8)

An organic photoelectric conversion element comprising an organic layer containing at least a compound represented by the following general formula (2), (3) or (4) between a counter electrode and a transparent electrode.
(In the formula, A ₂ represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, and R _{4 to} R ₇ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, or an alkynyl group. , A cycloalkyl group, an aryl group, a heteroaryl group, an amino group, an ether group, a thioether group, or a substituent in which a plurality of these are connected, and R _{4 to} R ₇ may be bonded to each other to form a ring. N represents an integer of ₁ to _3. L ₁ and L _{2 each} represents a single bond, an alkylene group, an amino group, an ether group, a thioether group, a silylene group, a ketone group, a phosphino group, a phosphoryl group, or a plurality of these. (It represents a divalent linking group selected from substituents, and the spherical structure to which these substituents are bonded represents a C60-C540 fullerene structure.)
(Wherein, X is a substituted or unsubstituted nitrogen atom, an oxygen atom, a sulfur atom, and _{CR 15 = CR 16 -, -} CR 17 = N -, - N = can form an aromatic ring selected from N- R _{8 to} R ₁₇ each independently represent a hydrogen atom, or a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, heteroaryl group, amino group, or a linking group or a chalcogen atom. A group, an ether group, a thioether group, a ketone group, an ester group, an amide group, or a substituent in which a plurality of these groups are connected, n represents an integer of 1 to 3. In addition, a sphere to which these substituents are bonded Represents a fullerene structure of C60 to C540.) 2. The organic photoelectric conversion device according to claim 1 , wherein L ₁ or L ₂ of the compound represented by the general formula (2) is an alkylene group. The organic photoelectric conversion element according to claim 1, characterized in that the - X of the compound represented by the general formula (4) is _-CR 15 = _{CR 16.} R _{15, R 16} has the same meaning as _{R 15, R 16} in the general formula (4). The organic photoelectric conversion element according to claim 1 or 3 R ₉ of the compound represented by the general formula (4) is characterized in that the alkyl group. The organic photoelectric conversion element according to any one of claims 1 to 4 , wherein the organic layer is formed by a solution process. The organic layer comprises a compound represented by any one of formulas (2) to (4), according to claim 1 to 5, characterized in that the bulk hetero junction layer containing a conjugated polymer material The organic photoelectric conversion element of any one of these. It consists of an organic photoelectric conversion element of any one of Claims 1-6 , The solar cell characterized by the above-mentioned. Photosensor array organic photoelectric conversion device is characterized by comprising arranged in an array according to any one of claims 1-7.