Photoelectric conversion elements, optical sensors, image sensors, and flexible sensors

Abstract

To provide a photoelectric conversion element having sensitivity to light of a wavelength range with high biological transparency and to provide an optical sensor, an image sensor, and a flexible sensor using the same.SOLUTION: A photoelectric conversion element 20 includes a photoelectric conversion layer 14 containing a conjugated polymer compound. The conjugated polymer compound has on a main chain a squarylium structure represented by the following general formula (1) or a croconium structure represented by the following general formula (2).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion element, an optical sensor, an image sensor, and a flexible sensor. More specifically, the present invention relates to a photoelectric conversion element or the like that is sensitive to light in a wavelength range that is highly transmissive to living organisms. [Background technology]

[0002] Biosensing using light from the second biological window (near-infrared wavelength range of 1000-1350 nm), which has higher biological transmittance than light from the first biological window (near-infrared wavelength range of 650-1000 nm), is attracting attention. Furthermore, light above 1400 nm is known as the eye-safe band, and is low-energy light that does not damage the retina, making biosensing using strong laser light possible. To enable such biosensing, a photoelectric conversion element capable of detecting light with wavelengths above 1000 nm is required.

[0003] InGaAs photodiodes have traditionally been used as photoelectric conversion elements capable of detecting light with wavelengths of 1000 nm or longer. However, inorganic photoelectric conversion elements such as InGaAs photodiodes have been limited in their applications and fields due to issues such as thinness, flexibility, large area, and cost.

[0004] On the other hand, the problems of inorganic photoelectric conversion elements can be solved by using an organic photoelectric conversion element such as that disclosed in Patent Document 1. However, the organic materials used in conventional organic photoelectric conversion elements do not have sufficient detectability for light with wavelengths of 1000 nm or more, and therefore are not suitable for photoelectric conversion elements that are sensitive to light in a wavelength range that is highly permeable to living organisms. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-21848 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a photoelectric conversion element that is sensitive to light in a wavelength range that is highly permeable through living organisms, as well as an optical sensor, an image sensor, and a flexible sensor that use the same. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors have investigated the causes of the above problems and have found that by using a conjugated polymer compound having a squarylium structure or a croconium structure in the main chain in a photoelectric conversion layer, it is possible to provide a photoelectric conversion element or the like that is sensitive to light in a wavelength range that is highly permeable to living organisms, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. A photoelectric conversion element having a photoelectric conversion layer containing a conjugated polymer compound, The conjugated polymer compound has a structure represented by the following structural formulas (1) to (71): Any one of the following have A photoelectric conversion element characterized by: [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0011] 2. A photoelectric conversion element having a photoelectric conversion layer containing a conjugated polymer compound, The conjugated polymer compound is a squarylium compound having a structure represented by the following general formula (3) or a croconium compound having a structure represented by the following general formula (4): , or The conjugated polymer compound is a squarylium compound having a structure represented by the following general formula (5) or a croconium compound having a structure represented by the following general formula (6): It is characterized by Light Electrical conversion element. [ka] [In the general formulas (3) and (4), R1 to R4 each independently represent an alkyl group, Phenyl group, or Pyridyl L1 and L2 each independently represent an arylene group, a heteroarylene group, an ethynylene group, a vinylene group, or a combination thereof. [ka] [In general formulas (5) and (6), L 1 and L 2 each independently represents an arylene group, a heteroarylene group, an ethynylene group, a vinylene group, or a combination thereof. 3. The molecular terminals of the conjugated polymer compound are capped. 3. The photoelectric conversion element according to claim 1 or 2, 4. Detects and operates on light with wavelengths of 1000 nm or more 4. The photoelectric conversion element according to any one of items 1 to 3, characterized in that:

[0012] 5. An optical sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of items 1 to 4. An optical sensor characterized by:

[0013] 6. An image sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of items 1 to 4. An image sensor characterized by:

[0014] 7. A flexible sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of items 1 to 4. A flexible sensor characterized by: [Effects of the Invention]

[0015] According to the above-mentioned means of the present invention, it is possible to provide a photoelectric conversion element that is sensitive to light in a wavelength range that is highly transmissive to living organisms, as well as an optical sensor, an image sensor, and a flexible sensor that use the same.

[0016] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0017] The photoelectric conversion layer provided in the photoelectric conversion element of the present invention contains a conjugated polymer compound having a squarylium structure or a croconium structure in its main chain. Such conjugated polymer compounds are highly planar and therefore suitable as materials for thin-film photoelectric conversion layers. Furthermore, because the conjugated polymer compound is a two-dimensionally extended conjugated compound having a squarylium structure or a croconium structure in its main chain, it has sufficient light absorption properties for light in a wavelength range with high biological permeability. It is believed that this mechanism allows the photoelectric conversion element of the present invention to be sensitive to light in a wavelength range with high biological permeability. [Brief explanation of the drawings]

[0018] [Figure 1] Schematic cross-sectional view of a photoelectric conversion element with a normal layered, single structure [Figure 2] Schematic cross-sectional view of a photoelectric conversion element with a reversed layer and single structure [Figure 3] Schematic cross-sectional view of a photoelectric conversion element with a normal layered tandem structure DETAILED DESCRIPTION OF THE INVENTION

[0019] The photoelectric conversion element of the present invention is a photoelectric conversion element including a photoelectric conversion layer containing a conjugated polymer compound, characterized in that the conjugated polymer compound has a squarylium structure represented by the above general formula (1) or a croconium structure represented by the above general formula (2) in its main chain. This feature is a technical feature common to or corresponding to the following embodiments.

[0020] In an embodiment of the photoelectric conversion element of the present invention, the molecular terminals of the conjugated polymer compound are preferably capped. In polymer compounds synthesized by a condensation reaction of multiple molecules, the terminal structure is usually unclear and reactive activity remains. If the molecular terminals are capped with reactively inactive terminals and the terminal structure is clarified and inactivated, domain expansion is suppressed and carrier mobility is improved. Due to this effect, a photoelectric conversion element containing a conjugated polymer compound with a capped molecular terminal has improved light detectability.

[0021] In an embodiment of the photoelectric conversion element of the present invention, it is preferable that the element operates by detecting light having a wavelength of 1000 nm or more, which makes it possible to detect light in a wavelength range that is particularly highly permeable to living organisms.

[0022] In an embodiment of the photoelectric conversion element of the present invention, the conjugated polymer compound is preferably a squarylium compound having a structure represented by the above general formula (3) or a croconium compound having a structure represented by the above general formula (4), thereby achieving higher detectability for light in a wavelength range that is highly permeable through living organisms.

[0023] The optical sensor of the present invention is an optical sensor using a photoelectric conversion element, characterized in that the photoelectric conversion element is the photoelectric conversion element of the present invention.

[0024] The image sensor of the present invention is an image sensor using a photoelectric conversion element, characterized in that the photoelectric conversion element is the photoelectric conversion element of the present invention.

[0025] The flexible sensor of the present invention is a flexible sensor using a photoelectric conversion element, characterized in that the photoelectric conversion element is the photoelectric conversion element of the present invention.

[0026] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0027] 1. Overview of the photoelectric conversion element of the present invention The photoelectric conversion element of the present invention is a photoelectric conversion element including a photoelectric conversion layer containing a conjugated polymer compound, characterized in that the conjugated polymer compound has a squarylium structure represented by the following general formula (1) or a croconium structure represented by the following general formula (2) in its main chain:

[0028] In the present invention, the term "conjugated polymer compound" refers to a polymer compound that is a conjugated system. Here, the term "conjugated system" refers to a state in which the π electrons of the multiple bonds are delocalized due to the repetition of multiple bonds and single bonds. Furthermore, in the present invention, the term "polymer compound" refers to a compound having a number average molecular weight of 3000 or more.

[0029] The photoelectric conversion element of the present invention has sensitivity to light in a wavelength range with high biological permeability because the conjugated polymer compound contained in the photoelectric conversion layer has a squarylium structure represented by the following general formula (1) or a croconium structure represented by the following general formula (2) in its main chain. Specifically, the photoelectric conversion element of the present invention preferably operates by detecting light with a wavelength of 1000 nm or more. This makes it possible to detect light in a wavelength range with particularly high biological permeability. Here, "operate" means being able to convert light energy into electrical energy, and means, for example, that the external quantum efficiency is 0.1% or more.

[0030] The upper limit of the wavelength of the light to be detected is not particularly limited and is determined depending on the components of the contained conjugated polymer compound, etc. The upper limit can be, for example, 3000 nm, which is the upper limit of short-wavelength infrared light, or 1400 nm, which is the upper limit of near-infrared light.

[0031] 2. Conjugated polymer compounds The conjugated polymer compound according to the present invention is characterized by having a squarylium structure represented by the following general formula (1) or a croconium structure represented by the following general formula (2) in the main chain.

[0032] [ka]

[0033] The squarylium structure represented by the general formula (1) and the croconium structure represented by the general formula (2) are both structures in which π electrons are delocalized.

[0034] The conjugated polymer compound according to the present invention has the above-described squarylium structure or croconium structure in its main chain, and thus has sufficient light absorption properties for light in a wavelength range that is highly permeable to living organisms. Furthermore, because it is a conjugated polymer, it is suitable for forming a thin film with a heterojunction structure that is suitable for charge generation.

[0035] The conjugated polymer compound according to the present invention is preferably a squarylium compound having a structure represented by the following general formula (3) or a croconium compound having a structure represented by the following general formula (4), which allows for higher detectability for light in a wavelength range that is highly permeable to living organisms. [ka]

[0036] [In general formulas (3) and (4), R1 to R4 each independently represent an alkyl group, an aryl group, or a heteroaryl group. L1 and L2 each independently represent an arylene group, a heteroarylene group, an ethynylene group, a vinylene group, or a combination thereof.]

[0037] Examples of the alkyl group represented by R1 to R4 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an isohexyl group, a 1,3-dimethylbutyl group, a 1-isopropylpropyl group, a 1,2-dimethylbutyl group, an n-heptyl group, a 1,4-dimethylpentyl group, a 3-ethylpentyl group, a 2-ethylhexyl group, a 1-ethylhexyl group, a 2 ... Examples of alkyl groups that can be used include methylpentyl, 2-methyl-1-isopropylpropyl, 1-ethyl-3-methylbutyl, n-octyl, 2-ethylhexyl, 3-methyl-1-isopropylbutyl, 2-methyl-1-isopropyl, 1-t-butyl-2-methylpropyl, n-nonyl, 3,5,5-trimethylhexyl, n-decyl, isodecyl, n-undecyl, 1-methyldecyl, n-dodecyl, n-hexadecyl, and 2-hexyldecyl. The alkyl groups represented by R1 to R4 may further have a substituent.

[0038] Examples of the aryl group represented by R1 to R4 include non-condensed hydrocarbon groups such as phenyl, biphenyl, and terphenyl. Further examples include condensed polycyclic hydrocarbon groups such as pentalenyl, indenyl, naphthyl, azulenyl, heptalenyl, biphenylenyl, fluorenyl, acenaphthylenyl, pleiadenyl, acenaphthenyl, phenalenyl, phenanthryl, anthryl, fluoranthenyl, acephenanthrylenyl, aceanthrylenyl, triphenylenyl, pyrenyl, chrysenyl, and naphthacenyl. The aryl groups represented by R1 to R4 may further have a substituent.

[0039] Examples of the heteroaryl group represented by R1 to R4 include groups derived from a heterocycle containing no nitrogen atom, such as a furanyl group (furyl group), a thiophenyl group (thienyl group), a silafluorenyl group, a benzofuranyl group, a dibenzofuranyl group, a benzothiophenyl group, a dibenzothiophenyl group, a dithienopyrrolyl group, a benzodithiophenyl group, a dithienosilacyclopentadienyl group, a dithienocyclopentadienyl group, a chromonyl group, and an indazironyl group. Furthermore, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a triazinyl group, a pyrrolyl group, a quinolyl group, a piperidyl group, a coumarinyl group, a benzimidazolyl group, a benzoxazolyl group, a benzthiazolyl group, an indolyl group, a carbazolyl group, a pyrazolyl group, an imidazolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, an indazolyl group, a benzothiazolyl group, a pyridazinyl group, a cinnolyl group, a quinazolyl group, a quinazolyl group, a quinoxalyl group, a quinoxalonyl group, a quinazolinedionyl group, a quinoxalinedionyl group, a phthalazinyl group, Examples of the heteroaromatic ring include a group derived from a heteroaromatic ring containing a nitrogen atom (a nitrogen-containing aromatic ring), such as a phthalazinedionyl group, a phthalazonyl group, a phthalamidyl group, a quinolonyl group, an isoquinolonyl group, an isoquinolinyl group, a benzimidazolonyl group, a benzoxazolonyl group, a benzisoxazolyl group, a benzothiazolonyl group, a benzothiazothionyl group, a benzisothiazolyl group, a naphthalimidyl group, a dioxopyrimidinyl group, an acridinyl group, an acridonyl group, a benzoxazinedionyl group, a benzoxazinonyl group, a pyridonyl group, a naphthalidinyl group, or a naphtholactamyl group. The heteroaryl group represented by R1 to R4 may further have a substituent.

[0040] Examples of the arylene group represented by L1 and L2 include an o-phenylene group, an m-phenylene group, a p-phenylene group, a fluorenediyl group, a naphthalenediyl group, an anthracenediyl group, a naphthacenediyl group, a pyrenediyl group, a naphthylnaphthalenediyl group, a biphenyldiyl group (e.g., a [1,1'-biphenyl]-4,4'-diyl group, a 3,3'-biphenyldiyl group, a 3,6-biphenyldiyl group, etc.), a terphenyldiyl group, a quaterphenyldiyl group, a quinquephenyldiyl group, a sexiphenyldiyl group, a septiphenyldiyl group, an octyphenyldiyl group, a nobiphenyldiyl group, a deciphenyldiyl group, etc. The arylene group represented by L1 and L2 may further have a substituent.

[0041] Examples of the heteroarylene group representing L1 and L2 include heterocycles not containing a nitrogen atom, such as furan, thiophene, benzofuran, dibenzofuran, benzothiophene, dibenzothiophene, benzodithiophene, dithienopyrrole, silafluorene, dithienosilacyclopentadiene, dithienocyclopentadiene, chromone, and intanedione.Furthermore, pyridine, pyrimidine, pyrazine, triazine, carbazole, carboline, diazacarbazole, pyrrole, quinoline, isoquinoline, quinolone, isoquinolone, piperidine, coumarin, benzimidazole, benzimidazolone, benzoxazole, benzisoxazole, benzoxazolone, benzothiazole, benzothiazolethione, benzothiazolone, benzisothiazolone, indole, carbazole, pyrazole, imidazole, oxazole, isoxazole, thiazolone ... and divalent groups derived from the group consisting of heteroaromatic rings containing a nitrogen atom (nitrogen-containing aromatic rings), such as azole, isothiazole, indazole, pyridazine, cinnoline, quinazoline, quinazolone, quinoxaline, quinoxalone, phthalazine, acridine, acridone, benzoxazinedione, benzoxazinone, naphthalidine, naphtholactam, quinazolinedione, quinoxalinedione, phthalazinedione, pyridone, phthalazone, phthalamidine, naphthalimidine, and dioxopyrimidine. The heteroarylene groups representing L1 and L2 may further have a substituent.

[0042] L1 and L2 may be a combination of an arylene group, a heteroarylene group, an ethynylene group, and a vinylene group, and examples thereof include the following combinations. Ethynylene group-arylene group-ethynylene group Ethynylene group-heteroarylene group-ethynylene group Vinylene group-arylene group-vinylene group Vinylene group-heteroarylene group-vinylene group Arylene group - Arylene group Vinylene group-arylene group-arylene group-vinylene group Ethynylene group-arylene group-arylene group-ethynylene group Heteroarylene group - Heteroarylene group Vinylene group-heteroarylene group-heteroarylene group-vinylene group Ethynylene group-heteroarylene group-heteroarylene group-ethynylene group

[0043] Examples of conjugated polymer compounds according to the present invention are shown below. In the chemical structural formulas of the exemplified conjugated polymer compounds, n represents a degree of polymerization in the range of 5 to 10,000. However, the conjugated polymer compounds according to the present invention are not limited to these.

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057] [ka]

[0058] The conjugated polymer compound according to the present invention can be synthesized, for example, by reacting squaric acid or croconic acid with a monomer capable of undergoing a dehydration condensation reaction therewith.

[0059] Synthesis Example 1 and Synthesis Example 2 for obtaining the conjugated polymer compound according to the present invention are shown below.

[0060] [ka]

[0061] [ka]

[0062] The conjugated polymer compound according to the present invention is preferably end-capped. In polymer compounds synthesized by a condensation reaction of multiple molecules, the end structure is usually unclear and reactive activity remains. Here, if the molecular end is capped with a reactively inactive end, and the end structure is clarified and inactivated, domain expansion is suppressed and carrier mobility is improved. Due to this effect, a photoelectric conversion element containing a conjugated polymer compound with end-capped molecules has improved light detectability.

[0063] A conjugated polymer compound whose molecular terminals are capped with reactive inert terminals can be obtained by modifying the molecular terminals of the conjugated polymer compound with a capping agent (capping treatment).

[0064] Synthesis Examples 3 and 4, in which the molecular terminals of a conjugated polymer compound are modified with a capping agent, are shown below.

[0065] [ka]

[0066] [ka]

[0067] The capping agent can be a compound that can react with one of the two monomers used in the synthesis of the conjugated polymer compound but cannot react with the other monomer. As long as this requirement is met, the type of compound is not particularly limited, and for example, one of the two monomers used in the synthesis of the conjugated polymer compound can also be used as the capping agent.

[0068] The molecular weight of the conjugated polymer compound according to the present invention is not particularly limited as long as the number-average molecular weight is 3,000 or more. However, to impart good morphology to the conjugated polymer compound, a moderate molecular weight is preferable. On the other hand, if the molecular weight is too high, solubility may be reduced. Specifically, the number-average molecular weight of the conjugated polymer compound is preferably in the range of 5,000 to 100,000, more preferably in the range of 10,000 to 70,000, and even more preferably in the range of 15,000 to 50,000. In particular, when the conjugated polymer compound according to the present invention is used as a p-type organic semiconductor to form a bulk heterojunction photoelectric conversion layer, a low-molecular-weight compound (e.g., fullerene derivative) is widely used as an n-type organic semiconductor. However, when the molecular weight of the conjugated polymer compound used as the p-type organic semiconductor is within the above range, a microphase-separated structure is well formed, which facilitates the formation of carrier paths for carrying holes and electrons generated at the p-n junction interface.

[0069] In the present invention, the number average molecular weight of the conjugated polymer compound can be measured by gel permeation chromatography (GPC; standard material: polystyrene).

[0070] 3. Photoelectric conversion element configuration The photoelectric conversion element of the present invention is not particularly limited in its configuration other than that as long as it has the above-mentioned photoelectric conversion layer, but in a typical configuration, the photoelectric conversion element has at least a transparent electrode and a counter electrode, with the photoelectric conversion layer therebetween.

[0071] In the present invention, a configuration in which the transparent electrode is used as an anode and holes are extracted from the transparent electrode side, and the counter electrode is used as a cathode and electrons are extracted from the counter electrode side is called a "normal layer configuration." On the other hand, a configuration in which the transparent electrode is used as a cathode and electrons are extracted from the transparent electrode side, and the counter electrode is used as an anode and holes are extracted from the counter electrode side is called an "inverted layer configuration."

[0072] When distinguishing between configurations based on the number of photoelectric conversion layers, a configuration with only one photoelectric conversion layer is called a "single configuration," and a configuration with multiple photoelectric conversion layers is called a "tandem configuration."

[0073] The configuration of the photoelectric conversion element will be described below with reference to the drawings.

[0074] Fig. 1 is a cross-sectional schematic diagram showing a photoelectric conversion element having a normal layered single structure. Specifically, the photoelectric conversion element 10 in Fig. 1 has a structure in which an anode (transparent electrode) 11, a hole transport layer 26, a photoelectric conversion layer 14, an electron transport layer 27, and a cathode (counter electrode) 12 are laminated in this order on a substrate 25. The substrate 25 is an optional member that is provided mainly to facilitate the formation of the anode (transparent electrode) 11 thereon by a coating method.

[0075] 1 is operated, light is irradiated from the substrate 25 side. In this embodiment, the anode (transparent electrode) 11 is made of a transparent electrode material (e.g., ITO) so that the irradiated light can reach the photoelectric conversion layer 14. The light irradiated from the substrate 25 side reaches the photoelectric conversion layer 14 via the transparent anode (transparent electrode) 11 and the hole transport layer 26.

[0076] The hole transport layer 26 is made of a material with high hole mobility and functions to efficiently transport holes generated at the pn junction interface of the photoelectric conversion layer 14 to the anode (transparent electrode) 11. On the other hand, the electron transport layer 27 is made of a material with high electron mobility and functions to efficiently transport electrons generated at the pn junction interface of the photoelectric conversion layer 14 to the cathode (counter electrode) 12.

[0077] FIG. 2 is a cross-sectional schematic diagram illustrating a photoelectric conversion element having an inverted-layer single structure. The photoelectric conversion element 20 of FIG. 2 differs from the photoelectric conversion element 10 of FIG. 1 in that the anode 11 and cathode 12 are arranged in reverse positions, and the hole transport layer 26 and electron transport layer 27 are arranged in reverse positions. The photoelectric conversion element 20 has a configuration in which a cathode (transparent electrode) 12, an electron transport layer 27, a photoelectric conversion layer 14, a hole transport layer 26, and an anode (counter electrode) 11 are stacked in this order on a substrate 25. With this configuration, electrons generated at the pn junction interface of the photoelectric conversion layer 14 are transported to the cathode (transparent electrode) 12 via the electron transport layer 27, and holes are transported to the anode (counter electrode) 11 via the hole transport layer 26.

[0078] 3 is a cross-sectional schematic diagram showing a photoelectric conversion element having a normal layer-type tandem configuration. The photoelectric conversion element 30 of FIG. 3 differs from the photoelectric conversion element 10 of FIG. 1 in that, instead of the photoelectric conversion layer 14, a laminate of a first photoelectric conversion layer 14a, a second photoelectric conversion layer 14b, and a charge recombination layer (intermediate electrode) 38 interposed between these two photoelectric conversion layers is disposed. In the photoelectric conversion element 30, photoelectric conversion materials (a p-type organic semiconductor and an n-type organic semiconductor) having different absorption wavelengths are used for the first photoelectric conversion layer 14a and the second photoelectric conversion layer 14b, respectively, thereby enabling efficient conversion of light over a wider wavelength range into electricity.

[0079] Hereinafter, each component of the photoelectric conversion element according to the present invention will be described in detail.

[0080] [electrode] As mentioned above, carriers (holes and electrons) generated in the photoelectric conversion layer move between the electrodes, with the holes reaching the anode and the electrons reaching the cathode. In the present invention, the electrode through which holes mainly flow is called the anode, and the electrode through which electrons mainly flow is called the cathode. Furthermore, when adopting a tandem configuration, this can be achieved by using a charge recombination layer (intermediate electrode). Furthermore, depending on the functionality of the electrodes, whether they are translucent or not, translucent electrodes are sometimes called transparent electrodes, and non-translucent electrodes are sometimes called counter electrodes. In the case of a normal layer configuration, the anode is usually a translucent electrode, and the cathode is a non-translucent counter electrode.

[0081] The materials used for the electrodes of this embodiment are not particularly limited as long as they can be operated as a photoelectric conversion element, and any electrode material that can be used in this technical field can be appropriately adopted. In particular, the anode is preferably made of a material having a relatively large work function compared to the cathode, and conversely, the cathode is preferably made of a material having a relatively small work function compared to the anode.

[0082] The anode in a photoelectric conversion element having a normal layer structure is preferably made of a transparent electrode material (transmitting light of 380 to 800 nm) with a relatively large work function, while the cathode 12 has a relatively small work function (for example, 4 eV or less) and is usually made of an electrode material with low light transmittance.

[0083] In such a photoelectric conversion element having a normal layer structure, examples of electrode materials used for the anode (transparent electrode) include metals such as gold, silver, and platinum; transparent conductive metal oxides such as indium tin oxide (ITO), SnO2, and ZnO; and carbon materials such as metal nanowires and carbon nanotubes. Conductive polymers can also be used as the electrode material for the anode. Examples of conductive polymers that can be used for the anode include PEDOT:PSS, polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene, polynaphthalene, and derivatives thereof. These electrode materials may be used alone or in combination of two or more materials. Furthermore, an electrode can be constructed by stacking two or more layers of each material.

[0084] On the other hand, in photoelectric conversion elements with a normal layer structure, electrode materials used for the cathode (counter electrode) can include metals, alloys, electronically conductive compounds, and mixtures thereof. Specific examples include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, from the viewpoints of electron extraction performance and durability against oxidation, it is preferable to use mixtures of a first metal with a low work function and a second metal that is stable and has a higher work function than the first metal, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, lithium / aluminum mixtures, and stable metals such as aluminum. It is also preferable to use metals among these materials, as this allows light that enters from the anode (transparent electrode) side and is not absorbed by the photoelectric conversion layer to be reflected by the cathode (counter electrode) and reused for photoelectric conversion, thereby improving photoelectric conversion efficiency. These electrode materials may be used alone or in combination of two or more materials. It is also possible to form an electrode by laminating two or more layers made of each material. The thickness of the cathode (counter electrode) is not particularly limited, but is usually 10 nm to 5 μm, preferably 50 to 200 nm.

[0085] In a photoelectric conversion element having an inverted layer structure, a cathode (transparent electrode) is located on the substrate side where light is incident, and an anode (counter electrode) is located on the opposite side. Therefore, in an inverted layer structure, the anode preferably has a relatively large work function and is usually made of an electrode material with low light transmittance. On the other hand, the cathode has a relatively small work function and is made of a transparent electrode material.

[0086] In photoelectric conversion elements with an inverted layer structure, electrode materials used for the cathode (transparent electrode) include, for example, metals, metal compounds, and alloys such as gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, and indium; and carbon materials such as carbon nanoparticles, carbon nanowires, and carbon nanostructures. Among these, transparent conductive metal oxides such as indium tin oxide (ITO) are preferred. These electrode materials may be used alone or in combination. An electrode can also be constructed by stacking two or more layers of each material. Among these, carbon nanowires are preferred because they enable the formation of a transparent, highly conductive cathode by a coating method. When using a metal-based material, a cathode (transparent electrode) can be formed by first preparing an auxiliary electrode with a thickness of approximately 1 to 20 nm on the side facing the anode (counter electrode) using, for example, aluminum, aluminum alloy, silver, or silver compound, and then providing a conductive polymer film, such as one of the examples of the anode (transparent electrode) material for the photoelectric conversion element with the normal layer structure described above.

[0087] On the other hand, in a photoelectric conversion element having an inverted layer structure, the electrode material used for the anode (counter electrode) is preferably an electrode material having a relatively larger work function than the cathode (transparent electrode). For example, the anode (counter electrode) can be formed using a metal material such as silver, nickel, molybdenum, gold, platinum, tungsten, or copper.

[0088] The photoelectric conversion element of the present invention preferably has an inverted layer structure, in which materials that are resistant to deterioration by oxygen, moisture, etc. can be used for both the anode and the cathode. Examples of the combination of materials used for the anode and the cathode in the inverted layer structure include: 1 Cathode (ITO), Anode (Silver) 2 Cathode (PEDOT:PSS), Anode (Silver) 3 Cathode (ITO), anode (copper) 4 Cathode (PEDOT:PSS), Anode (gold) 5 Cathode (ITO), Anode (PEDOT:PSS) The following can be mentioned:

[0089] [Photoelectric conversion layer] The photoelectric conversion layer is a layer having the function of converting light energy into electrical energy by utilizing the photovoltaic effect. The photoelectric conversion element of the present invention is characterized in that the photoelectric conversion layer contains the conjugated polymer compound according to the present invention described above. Here, the photoelectric conversion element of the present invention preferably contains the conjugated polymer compound according to the present invention as a p-type organic semiconductor and further contains an n-type organic semiconductor. When light is absorbed by these photoelectric conversion materials, excitons are generated, which are charge-separated into holes and electrons at the pn junction interface.

[0090] The p-type organic semiconductor may contain other p-type organic semiconductors as needed. Examples of fused polycyclic aromatic low molecular weight compounds, polymer compounds, and oligomer compounds that may be contained as other p-type organic semiconductors are shown below.

[0091] Examples of condensed polycyclic aromatic low molecular weight compounds include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fulminene, pyrene, peropyrene, perylene, terrylene, quaterrylene, coronene, ovalene, circumanthracene, bisanthene, zethrene, heptazethrene, pyranthrene, violanthene, isoviolanthene, circobiphenyl, anthradithiophene, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF)-tetracyanoquinodimethane (TCNQ) complex, bisethylenedithiotetrathiafulvalene (BEDTTTF)-perchloric acid complex, and derivatives and precursors thereof.

[0092] Examples of the polymer compound or oligomer compound include polythiophenes such as poly3-hexylthiophene (P3HT) and oligomers thereof, polythiophenes having a polymerizable group as described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, p. 1225, polythiophene-thienothiophene copolymers as described in Nature Material, (2006) vol. 5, p. 328, polythiophene-diketopyrrolopyrrole copolymers as described in International Publication No. 2008 / 000664, polythiophene-thiazolothiazole copolymers as described in Adv Mater, 2007, p. 4160, Nature Examples include polythiophene copolymers such as PCPDTBT described in Mat. vol. 6 (2007), p. 497, polypyrrole and its oligomers, polyaniline, polyphenylene and its oligomers, polyphenylene vinylene and its oligomers, polythienylene vinylene and its oligomers, polyacetylene, polydiacetylene, polysilane, and σ-conjugated polymers such as polygermane.

[0093] Furthermore, oligomers such as α-sexithiophene, which is a thiophene hexamer, α,ω-dihexyl-α-sexithiophene, α,ω-dihexyl-α-quinquethiophene, and α,ω-bis(3-butoxypropyl)-α-sexithiophene can be suitably used.

[0094] Among these compounds, compounds that are highly soluble in organic solvents to the extent that solution processing is possible, that form a crystalline thin film after drying, and that can achieve high mobility are preferred. More preferred are compounds that have appropriate compatibility with the n-type organic semiconductor contained in the photoelectric conversion layer (compounds that can form an appropriate phase-separated structure).

[0095] In addition, a material that can be insolubilized after application by a solution process is preferred, so that even when an electron transport layer or a hole blocking layer is further formed on the photoelectric conversion layer by a solution process, the layer can be easily formed without dissolving the photoelectric conversion layer.

[0096] Examples of materials that can be insolubilized after application by a solution process include materials that can be insolubilized by polymerizing and cross-linking a coating film after application, such as polythiophenes having polymerizable groups, as described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, p. 1225; and materials that can be insolubilized (pigmented) by the application of energy such as heat through a reaction of soluble substituents, as described in U.S. Patent Application Publication No. 2003 / 136964 and JP-A No. 2008-16834.

[0097] In addition, there are no particular restrictions on the content of the conjugated polymer compound according to the present invention and other p-type organic semiconductors in the p-type organic semiconductor contained in the photoelectric conversion layer. However, from the viewpoint of the effects of the present invention, the higher the proportion of the conjugated polymer compound according to the present invention relative to the total amount of p-type organic semiconductors contained in the photoelectric conversion layer (when two or more photoelectric conversion layers are included, the total amount in all layers), the better. Specifically, the proportion of the conjugated polymer compound according to the present invention relative to the total amount of p-type organic semiconductors is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0098] The n-type organic semiconductor that can be contained in the photoelectric conversion layer is preferably an organic compound that has acceptor properties (electron-accepting properties) with respect to the p-type organic semiconductor, and materials that can be used in this technical field can be appropriately adopted. Such compounds may be compounds that are 0.2 to 0.5 eV or more deeper than the LUMO level of the p-type organic semiconductor, and examples thereof include fullerenes, carbon nanotubes, octaazaporphyrins, perfluoro compounds in which hydrogen atoms of the p-type organic semiconductors are substituted with fluorine atoms (e.g., perfluoropentacene, perfluorophthalocyanine, etc.), and polymer compounds containing aromatic carboxylic acid anhydrides or imidized products thereof as a skeleton, such as naphthalene tetracarboxylic acid anhydride, naphthalene tetracarboxylic acid diimide, perylene tetracarboxylic acid anhydride, and perylene tetracarboxylic acid diimide.

[0099] Among these, fullerenes, carbon nanotubes, or derivatives thereof are preferably used from the viewpoint of enabling high-speed (up to 50 fs) and efficient charge separation with p-type organic semiconductors. More specifically, fullerene C60, fullerene C70, fullerene C76, fullerene C78, ​​fullerene C84, fullerene C240, fullerene C540, mixed fullerenes, fullerene nanotubes, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanohorns (cone-shaped), etc., and fullerene derivatives partially substituted with hydrogen atoms, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), substituted or unsubstituted alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, cycloalkyl groups, silyl groups, ether groups, thioether groups, amino groups, etc.

[0100] In particular, [6,6]-phenyl C61-butyric acid methyl ester (abbreviated as PCBM), [6,6]-phenyl C61-butyric acid-n-butyl ester (PCBnB), [6,6]-phenyl C61-butyric acid-isobutyl ester (PCBiB), [6,6]-phenyl C61-butyric acid-n-hexyl ester (PCBH), [6,6]-phenyl C71-butyric acid methyl ester (abbreviated as PCBM), It is preferable to use a fullerene derivative whose solubility is improved by a substituent, such as bis-PCBM described in Adv. Mater., vol. 20 (2008), p. 2116, aminated fullerene described in JP-A-2006-199674, metallocenated fullerene described in JP-A-2008-130889, or fullerene having a cyclic ether group described in U.S. Pat. No. 7,329,709. In the present invention, the n-type organic semiconductor may be used alone or in combination of two or more.

[0101] The junction form between the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer is not particularly limited and may be a planar heterojunction or a bulk heterojunction (bulk heterojunction). A planar heterojunction is a junction form in which a p-type organic semiconductor layer containing a p-type organic semiconductor and an n-type organic semiconductor layer containing an n-type organic semiconductor are stacked, and the surface where these two layers contact forms a p-n junction interface. On the other hand, a bulk heterojunction is formed by applying a mixture of a p-type organic semiconductor and an n-type organic semiconductor, and in this single layer, domains of the p-type organic semiconductor and the n-type organic semiconductor form a microphase-separated structure. Therefore, in a bulk heterojunction, more p-n junction interfaces exist throughout the layer than in a planar heterojunction. Therefore, many excitons generated by light absorption can reach the p-n junction interface, thereby improving the efficiency of charge separation. For these reasons, the junction between the p-type organic semiconductor and the n-type organic semiconductor in the photoelectric conversion layer of the photoelectric conversion element of the present invention is preferably a bulk heterojunction.

[0102] In addition, the bulk heterojunction layer may be composed of a single layer (i-layer) made of a mixture of a conventional p-type organic semiconductor and an n-type organic semiconductor, or may have a three-layer structure (p-i structure) in which the i-layer is sandwiched between a p-layer made of a p-type organic semiconductor and an n-layer made of an n-type organic semiconductor. Such a p-i structure has higher rectification of holes and electrons, reduces losses due to recombination of charge-separated holes and electrons, and can achieve even higher photoelectric conversion efficiency.

[0103] In the present invention, the mixing ratio of the p-type organic semiconductor to the n-type organic semiconductor contained in the photoelectric conversion layer is preferably within a range of 2:8 to 8:2 by mass, more preferably within a range of 2.5:7.5 to 7.5:2.5.

[0104] The thickness of one photoelectric conversion layer is preferably within a range of 50 to 400 nm, more preferably within a range of 80 to 300 nm, and particularly preferably within a range of 100 to 200 nm. Generally, from the viewpoint of absorbing more light, a thicker photoelectric conversion layer is preferable, but as the thickness increases, the efficiency of extracting carriers (holes and electrons) decreases, and the photoelectric conversion efficiency tends to decrease.

[0105] [substrate] The photoelectric conversion element of the present invention may include a substrate as needed. The substrate serves as a member to which the coating liquid is applied when the electrodes are formed by a coating method.

[0106] When light to be photoelectrically converted is incident from the substrate side, the substrate is preferably transparent to the wavelength of the light to be photoelectrically converted. Examples of transparent substrates include a glass plate, a quartz plate, and a transparent resin film.

[0107] Examples of materials for the glass plate include silica glass, soda-lime silica glass, lead glass, borosilicate glass, alkali-free glass, etc. If necessary, the surface of these glass materials may be subjected to physical treatment such as polishing, or may be coated with a coating made of an inorganic or organic substance, or a hybrid coating that is a combination of these coatings.

[0108] Examples of materials for the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose esters such as cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose acetate phthalate (TAC), and cellulose nitrate, or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide, polyethersulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylics or polyarylates, and cycloolefin resins such as Arton (trade name, manufactured by JSR Corporation) or Apel (trade name, manufactured by Mitsui Chemicals, Inc.).

[0109] The surface of the resin film may be formed with a coating made of an inorganic or organic substance, or a hybrid coating that combines these coatings. Such coatings and hybrid coatings have a water vapor permeability (25±0.5°C, relative humidity 90±2%RH) of 0.01 g / (m 2 It is preferable that the oxygen permeability of the film is 10 psi or less (24 hours). -3 mL / (m 2 24 hours atm) or less, water vapor permeability 10 -5 g / (m2 It is preferable that the film has a high barrier property (up to 24 hours).

[0110] The material for forming the above-described barrier film may be any material that has the function of preventing the penetration of moisture, oxygen, and other substances that cause deterioration of the device, and examples of such materials that can be used include silicon oxide, silicon dioxide, and silicon nitride. Furthermore, in order to improve the brittleness of the barrier film, it is more preferable to have a laminate structure of these inorganic layers and layers made of organic materials (organic layers). There are no particular restrictions on the order in which the inorganic and organic layers are laminated, but it is preferable to laminate the two layers alternately multiple times.

[0111] The method for forming the barrier film is not particularly limited, and for example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma polymerization, plasma CVD, laser CVD, thermal CVD, coating, etc. can be used, but the atmospheric pressure plasma polymerization method described in JP-A-2004-68143 is particularly preferred.

[0112] [Hole transport layer] The photoelectric conversion element of the present invention may optionally include a hole transport layer. The hole transport layer has the property of transporting holes and having a significantly low electron transport ability (for example, one-tenth or less of the hole mobility). The hole transport layer is provided between the photoelectric conversion layer and the anode, and transports holes to the anode while blocking the movement of electrons, thereby preventing the recombination of electrons and holes.

[0113] The hole transport material used in the hole transport layer is not particularly limited, and any material that can be used in this technical field can be appropriately adopted. Examples include PEDOT:PSS such as Baytron P (trade name) manufactured by Clevios, polythienothiophenes described in European Patent No. 1647566, sulfonated polythiophenes described in Japanese Patent Laid-Open No. 2010-206146, polyaniline and its doped material, and cyanide compounds described in International Publication No. 2006 / 019270.

[0114] In addition, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers, can also be used.

[0115] In addition, porphyrin compounds, aromatic tertiary amine compounds, styrylamine compounds, etc. can be used, and among these, aromatic tertiary amine compounds are preferably used. Furthermore, polymer materials having structural units contained in these compounds in the main chain or side chain can also be used as hole transport materials.

[0116] Furthermore, p-type hole transport materials such as those described in Japanese Patent Application Laid-Open No. 11-251067 and J. Huang et al., Applied Physics Letters, 80 (2002), p. 139 can also be used.

[0117] Also, a highly p-type hole transport material doped with impurities can be used, for example, materials described in JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Appl. Phys., 95, 5773 (2004), etc.

[0118] In some cases, the hole transport layer may be formed using inorganic compounds such as oxides of metals such as molybdenum, vanadium, tungsten, and the like, or mixtures thereof.

[0119] These hole transport materials may be used alone or in combination of two or more. It is also possible to form a hole transport layer by laminating two or more layers made of each material.

[0120] The thickness of the hole transport layer is not particularly limited, but is usually within the range of 1 to 2000 nm. From the viewpoint of further enhancing the leakage prevention effect, the thickness is preferably 5 nm or more. Furthermore, from the viewpoint of maintaining high transmittance and low resistance, the thickness is preferably 1000 nm or less, and more preferably 200 nm or less.

[0121] Generally, the conductivity of the hole transport layer is preferably high. However, if the conductivity is too high, the ability to block electrons from moving decreases, and the rectification may be reduced. Therefore, the conductivity of the hole transport layer is set to 10 -5 Preferably, the range is 1 S / cm to 1 S / cm. -4 ~10 -2 It is more preferable that the viscosity is in the range of S / cm.

[0122] [Electron transport layer] The photoelectric conversion element of the present invention may optionally include an electron transport layer. The electron transport layer has the property of transporting electrons and having a significantly low ability to transport holes. The electron transport layer is provided between the photoelectric conversion layer and the cathode, and transports electrons to the cathode while blocking the movement of holes, thereby preventing the recombination of electrons and holes.

[0123] The electron transport material used in the electron transport layer is not particularly limited, and any material available in the art can be appropriately employed. For example, octaazaporphyrin or a perfluorinated p-type organic semiconductor (such as perfluoropentacene or perfluorophthalocyanine) can be used. Similarly, an electron transport layer having a HOMO level deeper than that of the p-type organic semiconductor used in the photoelectric conversion layer is endowed with a hole-blocking function, which has a rectifying effect that prevents holes generated in the photoelectric conversion layer from flowing to the cathode. Therefore, a material having a HOMO level deeper than that of an n-type organic semiconductor is more preferably used as the electron transport material. Examples of such electron transport materials include phenanthrene-based compounds such as bathocuproine, n-type organic semiconductors such as naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic diimide, perylene tetracarboxylic anhydride, and perylene tetracarboxylic diimide, n-type inorganic oxides such as titanium oxide, zinc oxide, and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride.

[0124] Alternatively, a layer made of the n-type organic semiconductor alone used in the photoelectric conversion layer can be used. These electron transport materials may be used alone or in combination of two or more. The electron transport layer can also be formed by laminating two or more layers made of each material.

[0125] In the case of a reverse layer structure, which is advantageous from the viewpoint of durability, a compound insoluble in a coating solution containing a photoelectric conversion material is preferred as the electron transport material, since the photoelectric conversion layer is formed after the electron transport layer is formed on the cathode. From this viewpoint, the electron transport material is preferably an inorganic material such as titanium oxide or zinc oxide, or a crosslinkable organic material such as polyethyleneimine or an aminosilane coupling agent described in International Publication No. 2008 / 134492. Among these, it is preferred to use an aminosilane coupling agent (e.g., 3-(2-aminoethyl)-aminopropyltrimethoxysilane).

[0126] Examples of materials insoluble in the solvent used to apply the photoelectric conversion layer include π-conjugated polymers soluble in alcohols, and examples thereof include polyfluorenes and polythiophenes described in APPLIED PHYSICS LETTERS 95 (2009), p. 043301, Adv. Funct. Mat., 2010, p. 1977, Adv. Mater., 2011, 23, 3086, J. Am. Chem. Soc., 2011, p. 8416, and Advanced Materials, 2011 (Vol 23, no. 40), pp. 4636-4643, as well as polyfluorenes represented by the following structural formulas: These polymers are preferred because, unlike the above-mentioned silane coupling agents, they can be formed in a normal layer structure, i.e., on the photoelectric conversion layer. Furthermore, since the layer can function as an electron transport layer and hole blocking layer not only for metal oxides such as ITO but also for metal electrodes such as gold, silver, and copper, it is possible to use metals that are stable to oxidation as the cathode even in a normal layered structure, which is preferable.

[0127] [ka]

[0128] The thickness of the electron transport layer is not particularly limited, but is usually within the range of 1 to 2000 nm. From the viewpoint of further enhancing the leakage prevention effect, the thickness is preferably 2 nm or more, more preferably 5 nm or more. Furthermore, from the viewpoint of maintaining high transmittance and low resistance, the thickness is preferably 100 nm or less, more preferably 20 nm or less.

[0129] [Charge recombination layer; intermediate electrode] In a photoelectric conversion element having a tandem structure having a plurality of photoelectric conversion layers as shown in FIG. 3, a charge recombination layer (intermediate electrode) is disposed between the photoelectric conversion layers.

[0130] The material used for the charge recombination layer (intermediate electrode) is not particularly limited as long as it is both conductive and translucent. Examples of the electrode materials include transparent metal oxides such as ITO, AZO, FTO, and titanium oxide; metals such as Ag, Al, and Au; carbon materials such as carbon nanoparticles and carbon nanowires; and conductive polymers such as PEDOT:PSS and polyaniline. These materials may be used alone or in combination. It is also possible to form a charge recombination layer by stacking two or more layers of each material.

[0131] The conductivity of the charge recombination layer is preferably high from the viewpoint of obtaining high conversion efficiency, specifically, preferably in the range of 5 to 50,000 S / cm, more preferably in the range of 100 to 10,000 S / cm.

[0132] The thickness of the charge recombination layer is not particularly limited, but is preferably in the range of 1 to 1000 nm, and more preferably in the range of 5 to 50 nm. By making the thickness 1 nm or more, the film surface can be smoothed. On the other hand, by making the thickness 1000 nm or less, the short-circuit current density Jsc [mA / cm 2 ] can be reduced.

[0133] [Other layers] In addition to the above-described components (layers), the photoelectric conversion element of the present invention may further include other components (layers) to improve the photoelectric conversion efficiency and the life of the element. Examples of such other components include a hole injection layer, an electron injection layer, an exciton blocking layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer. Furthermore, a layer containing a silane coupling agent or the like may be provided to further stabilize metal oxide fine particles unevenly distributed in the upper layer. Furthermore, a metal oxide layer may be laminated adjacent to the photoelectric conversion layer.

[0134] The photoelectric conversion element of the present invention may also have various optically functional layers, such as an anti-reflection layer, a light-collecting layer, and a light-diffusing layer.

[0135] As the antireflection layer, various known antireflection layers can be provided. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, it is preferable to set the refractive index of the adhesive layer adjacent to the film within the range of 1.57 to 1.63, since this reduces the interfacial reflection between the film substrate and the adhesive layer and improves the transmittance. The refractive index can be adjusted by appropriately adjusting the ratio of an oxide sol with a relatively high refractive index, such as tin oxide sol or cerium oxide sol, to a binder resin and applying the layer. The adhesive layer may be a single layer, but may be configured to have two or more layers to improve adhesion.

[0136] The light-collecting layer can be fabricated, for example, by providing a microlens array on the light-receiving side of the substrate, or by combining it with a light-collecting sheet, to increase the amount of light received from a specific direction, or conversely, to reduce the dependency of the light on the angle of incidence.

[0137] As an example of a microlens array, square pyramids with sides ranging from 10 to 100 μm and apex angles of 90 degrees are arranged two-dimensionally on the light-receiving side of the substrate.

[0138] Examples of the light scattering layer include various anti-glare layers, and layers in which nanoparticles or nanowires of metals or various inorganic oxides are dispersed in a colorless, transparent polymer.

[0139] 4. Photoelectric conversion element manufacturing method The method for manufacturing the photoelectric conversion element of the present invention is not particularly limited, and the element can be manufactured by appropriately referring to conventionally known methods. Hereinafter, a method for manufacturing a photoelectric conversion element will be described using a single-inverted layer structure as an example. Note that each step in the manufacturing method described below can be applied to the manufacture of not only photoelectric conversion elements with a single-inverted layer structure, but also photoelectric conversion elements with a normal layer structure and photoelectric conversion elements with a tandem structure.

[0140] The method for manufacturing a photoelectric conversion element having a single inverted layer structure exemplified below includes the steps of forming a cathode, forming an electron transport layer, forming a photoelectric conversion layer, forming a hole transport layer, and forming an anode. Each step will be described in detail below.

[0141] [Cathode formation process] The method for forming the cathode is not particularly limited, but a method in which a liquid containing the cathode constituent material is applied to a substrate and then dried is preferred because of ease of operation and the possibility of roll-to-roll production using equipment such as a die coater. Alternatively, commercially available thin-film electrode materials may be used as they are.

[0142] [Step of forming an electron transport layer] The electron transport layer may be formed by either a vapor deposition method or a solution coating method, but the solution coating method is preferred.

[0143] When forming the electron transport layer using a solution coating method, the above-mentioned electron transport material is dissolved or dispersed in a suitable solvent, and the solution is applied to the cathode using a suitable coating method, followed by drying. Examples of coating methods that can be used include casting, spin coating, blade coating, wire bar coating, gravure coating, spray coating, dipping (immersion) coating, bead coating, air knife coating, curtain coating, inkjet printing, screen printing, letterpress printing, intaglio printing, offset printing, and flexographic printing, as well as conventional methods such as the Langmuir-Blodgett (LB) method. Among these, blade coating is particularly preferred.

[0144] The solids concentration of the solution used in the solution coating method may vary depending on the coating method and film thickness, but is preferably in the range of 1 to 15% by mass, more preferably 1.5 to 10% by mass. The temperature of the coating solution and the coating surface during coating is not particularly limited, but from the viewpoint of preventing precipitation and unevenness due to temperature fluctuations during coating and drying, it is preferably in the range of 30 to 120°C, more preferably 50 to 110°C. The specific drying method is also not particularly limited, and conventionally known knowledge can be used as appropriate. Examples of drying conditions include a temperature of approximately 80 to 140°C for several tens of seconds to several tens of minutes. Examples of drying devices include a hot plate, a warm air dryer, an infrared heater, a microwave, and a vacuum dryer, although other drying devices can also be used.

[0145] [Step of forming photoelectric conversion layer] The specific method for forming the photoelectric conversion layer is not particularly limited. For example, when forming a bulk heterojunction-type photoelectric conversion layer, a solution prepared by dissolving and dispersing a p-type organic semiconductor and an n-type organic semiconductor, either individually or together, in an appropriate solvent can be applied to the electron transport layer using an appropriate coating method and then dried. Heating is then preferably performed to remove residual solvent, moisture, and gas, and to crystallize the semiconductor to improve mobility and shift absorption to longer wavelengths. Annealing at a predetermined temperature during the manufacturing process promotes microscopic aggregation or crystallization, resulting in an appropriate phase-separated structure for the photoelectric conversion layer. As a result, the mobility of holes and electrons (carriers) in the photoelectric conversion layer is improved, enabling high efficiency. In this way, the p-type organic semiconductor and the n-type organic semiconductor are uniformly mixed to form a bulk heterojunction-type photoelectric conversion layer.

[0146] On the other hand, when forming a photoelectric conversion layer (for example, a pin structure) consisting of multiple layers with different mixing ratios of p-type organic semiconductors and n-type organic semiconductors, it is possible to form the layer by applying one layer, making the layer insolubilized (pigmented), and then applying another layer.

[0147] It should be noted that the steps after forming the photoelectric conversion layer are preferably performed in a glove box under a nitrogen atmosphere to prevent exposure to oxygen and moisture. By performing the steps under a nitrogen atmosphere, the p-type organic semiconductor can be prevented from being deteriorated by oxygen and moisture in the atmosphere, thereby improving the durability of the device. Specifically, the oxygen and moisture concentrations in the glove box are preferably 1000 ppm or less, more preferably 100 ppm or less, and most preferably 10 ppm or less.

[0148] [Step of forming a hole transport layer] The hole transport layer may be formed by either a vapor deposition method or a solution coating method, but the solution coating method is preferred. When the hole transport layer is formed by the solution coating method, the hole transport material described above is dissolved and dispersed in an appropriate solvent, and the solution is applied to the photoelectric conversion layer by an appropriate coating method, followed by drying. The details of the solution coating method are the same as those of the process for forming the electron transport layer described above.

[0149] [Process for forming the anode] There is no particular limitation on the means for forming the anode, and either a vapor deposition method or a solution coating method may be used, but a vapor deposition method (for example, a vacuum deposition method) is preferably used.

[0150] [others] The above-described steps are merely examples, and other steps can be added as needed, for example, as follows:

[0151] When the photoelectric conversion element includes layers other than the various layers described above, steps for forming these layers can be added as appropriate by using a solution coating method, a vapor deposition method, or the like.

[0152] The electrodes (cathode and anode), photoelectric conversion layer, hole transport layer, electron transport layer, and the like can be patterned as needed. The patterning method is not particularly limited, and known techniques can be appropriately employed. For example, when patterning a soluble material used in a bulk heterojunction photoelectric conversion layer, hole transport layer, or electron transport layer, the material can be applied to the entire surface by die coating, dip coating, or the like, followed by wiping off only the unnecessary portions, or the material can be patterned directly during application using methods such as inkjet printing or screen printing. On the other hand, insoluble materials used in electrodes, etc., can be patterned by mask deposition during deposition by vacuum deposition, or by known methods such as etching or lift-off. Alternatively, a pattern can be formed by transferring a pattern formed on another substrate.

[0153] Furthermore, the photoelectric conversion element of the present invention may be sealed as necessary to prevent deterioration due to oxygen, moisture, and the like in the environment. The sealing method is not particularly limited, and may be performed by a known method used for organic photoelectric conversion elements, organic electroluminescence elements, and the like. Examples include: (1) a sealing method using an adhesive to attach a cap made of aluminum or glass; (2) a method of attaching a plastic film having a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide to the photoelectric conversion element using an adhesive; (3) a method of spin-coating an organic polymer material (such as polyvinyl alcohol) with high gas barrier properties; (4) a method of depositing an inorganic thin film (such as silicon oxide or aluminum oxide) or an organic film (such as parylene) with high gas barrier properties under vacuum; and (5) a method of laminating a combination of these.

[0154] 5. Uses of photoelectric conversion elements The photoelectric conversion element of the present invention can be suitably used in an optical sensor that converts light into an electrical signal. Examples of the optical sensor include an image sensor that converts an optical image into an electrical signal and a flexible sensor that has flexibility.

[0155] The photoelectric conversion element of the present invention uses an organic semiconductor as the photoelectric conversion material, and therefore can be suitably used in flexible sensors, which have been difficult to apply to photoelectric conversion elements using inorganic semiconductors such as InGaAs.

[0156] Furthermore, by using the photoelectric conversion element of the present invention, the optical sensor, image sensor, and flexible sensor of the present invention can be suitably used for sensing using light in a wavelength range that is highly permeable to living organisms, which was difficult when using conventional organic photoelectric conversion elements, and can be particularly suitably used for biological sensing.

[0157] The photoelectric conversion element of the present invention can also be used in a solar cell. Since the photoelectric conversion element of the present invention can detect light in the near-infrared wavelength range with high sensitivity, a solar cell equipped with the photoelectric conversion element of the present invention can efficiently convert near-infrared light contained in sunlight into electric power. [Example]

[0158] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0159] 1. P-type organic semiconductor for photoelectric conversion layer Compounds A to K were prepared as p-type organic semiconductors for the photoelectric conversion layer.

[0160] (Compound A) [ka]

[0161] Monomer 1 (300 mg, 311 μmol), squaric acid (35.5 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. Monomer 1 (300 mg, 311 μmol) was then added and heated under reflux for an additional hour to perform capping. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to obtain the desired compound A as a dark green solid (yield: 287 mg, 88%).

[0162] The number average molecular weight of the obtained compound A was 3.0 × 10 4 It was.

[0163] (Compound B) [ka]

[0164] Monomer 1 (300 mg, 311 μmol), squaric acid (35.5 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to give the desired compound B as a dark green solid (yield: 310 mg, 95%).

[0165] The number average molecular weight of the obtained compound B was 2.8 × 10 4 It was.

[0166] (Compound C) [ka]

[0167] Monomer 1 (300 mg, 311 μmol), croconic acid (44.2 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. Monomer 1 (300 mg, 311 μmol) was then added and heated under reflux for an additional hour to perform capping. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to obtain the desired compound C as a dark green solid (yield: 130 mg, 39%).

[0168] The number average molecular weight of the obtained compound C was 3.2 × 10 4 It was.

[0169] (Compound D) [ka]

[0170] Monomer 1 (300 mg, 311 μmol), croconic acid (44.2 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. The solvent was removed by distillation under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to give the desired compound D as a dark green solid (yield: 224 mg, 67%).

[0171] The number average molecular weight of the obtained compound D was 3.0 × 10 4 It was.

[0172] (Compound E) [ka]

[0173] Monomer 2 (128.9 mg, 311 μmol), squaric acid (35.5 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. Monomer 2 (128.8 mg, 311 μmol) was then added and heated under reflux for an additional hour to perform capping. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to afford the desired compound E as a dark green solid (yield: 45.9 mg, 30%).

[0174] The number average molecular weight of the obtained compound E was 2.5 × 10 4 It was.

[0175] (Compound F) [ka]

[0176] Monomer 2 (128.9 mg, 311 μmol), squaric acid (35.5 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and refluxed for 2 hours. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to give compound F as a dark green solid (yield: 82.6 mg, 54%).

[0177] The number average molecular weight of the obtained compound F was 2.1 × 10 4 It was.

[0178] (Compound G) [ka]

[0179] Monomer 2 (128.9 mg, 311 μmol), croconic acid (44.2 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. Monomer 2 (128.8 mg, 311 μmol) was then added and heated under reflux for an additional hour to perform capping. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to obtain the desired compound G as a dark green solid (yield 76.1 mg, 47%).

[0180] The number average molecular weight of the obtained compound G was 2.6 × 10 4 It was.

[0181] (Compound H) [ka]

[0182] Monomer 2 (128.9 mg, 311 μmol), croconic acid (44.2 mg, 311 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. The solvent was removed under reduced pressure, and the resulting crude product was reprecipitated three times with dichloromethane / heptane to give the desired compound H as a dark green solid (yield: 123 mg, 76%).

[0183] The number average molecular weight of the obtained compound H was 2.2 × 10 4 It was.

[0184] (Compound I) [ka]

[0185] Compound I was PMDPP3T (poly[[2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-alt-[3′,3″-dimethyl-2,2′:5′,2″-terthiophene]-5,5″-diyl]).

[0186] The number average molecular weight of the compound I used was 3.2 × 10 4 It was.

[0187] (Compound J) [ka]

[0188] Monomer 1 (300 mg, 311 μmol), squaric acid (17.8 mg, 155 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. The solvent was removed under reduced pressure, and the resulting crude product was purified by silica gel column chromatography (solvent: dichloromethane / heptane) to give the desired compound J as a dark green solid (yield: 62.4 mg, 20%).

[0189] (Compound K) [ka]

[0190] Monomer 1 (300 mg, 311 μmol), croconic acid (22.1 mg, 155 μmol), toluene (30 mL), and n-butyl alcohol (10 mL) were added to a reaction vessel equipped with a Dean-Stark apparatus and heated under reflux for 2 hours. The solvent was removed under reduced pressure, and the resulting crude product was purified by silica gel column chromatography (solvent: dichloromethane / heptane) to give the desired compound K as a dark green solid (yield: 56.9 mg, 18%).

[0191] 2. Fabrication of Photoelectric Conversion Devices An ITO film was formed on a glass substrate by sputtering. The ITO film was patterned using photolithography and wet etching. This resulted in the formation of a 110 nm thick cathode (ITO transparent electrode).

[0192] The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and then subjected to UV ozone cleaning for 5 minutes. Next, a 7% ZnO solution (solvent: methoxyethanol / ethanolamine) was spin-coated onto the cathode (ITO transparent electrode). Annealing was then performed in air at 180°C for 30 minutes. This resulted in the formation of a 20 nm thick electron injection / transport layer.

[0193] A 1.5% solution (solvent: a mixed solvent of chloroform and o-dichlorobenzene) of p-type and n-type organic semiconductors mixed in a mass ratio of 1:3 was applied onto the electron injection transport layer by spin coating. The compounds listed in the table below were used for the p-type organic semiconductor in each photoelectric conversion element. C60PCBM ([6,6]-phenyl C61 butyric acid methyl ester) was used for the n-type organic semiconductor in each photoelectric conversion element. Next, annealing was performed at 100°C for 10 minutes under nitrogen. This resulted in the formation of a 280 nm-thick bulk heterojunction photoelectric conversion layer.

[0194] A 0.5% solution of PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)) in isopropanol was applied onto the photoelectric conversion layer by spin coating. The resulting layer was then annealed at 80°C for 5 minutes under nitrogen. This resulted in the formation of a 10 nm thick hole injection and transport layer.

[0195] On the hole injection transport layer, Ag was vacuum deposited to form an anode having a thickness of 80 nm.

[0196] The substrate was covered with 1 μm of parylene by chemical vapor deposition (CVD) and sealed. By the above procedure, bulk heterojunction type photoelectric conversion elements Nos. 1 to 11 were obtained.

[0197] 3. Measurement of external quantum efficiency and detection sensitivity The spectral sensitivity characteristics of each photoelectric conversion element in the near-infrared wavelength region were evaluated using a spectral sensitivity measurement device (Bunkokeiki SM-250). Monochromatic light of 1050 nm or 850 nm was irradiated, and the external quantum efficiency [%] and detection sensitivity [Jones] immediately after irradiation were evaluated. The evaluation results are shown in Table I.

[0198] [Table 1]

[0199] From the above evaluation results, it was confirmed that the photoelectric conversion element of the present invention has sensitivity to light in a wavelength range that is highly transmissive to living organisms.

[0200] Furthermore, since the photoelectric conversion element of the present invention uses an organic semiconductor, it can be suitably used in applications where it has been difficult to apply a photoelectric conversion element using an inorganic semiconductor such as InGaAs due to issues such as flexibility. [Explanation of symbols]

[0201] 10. Photoelectric conversion element with a normal layer type and single structure 20 Photoelectric conversion element with reverse layer and single structure 30 Photoelectric conversion element with normal layer and tandem structure 11 Anode 12 Cathode 14 Photoelectric conversion layer 14a First photoelectric conversion layer 14b Second photoelectric conversion layer 25 boards 26 Hole transport layer 27 Electron transport layer 38 Charge recombination layer (intermediate electrode)

Claims

1. A photoelectric conversion element including a photoelectric conversion layer containing a conjugated polymer compound, The conjugated polymer compound has any one of the structures represented by the following structural formulas (1) to (71): A photoelectric conversion element characterized by: 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】

2. A photoelectric conversion element including a photoelectric conversion layer containing a conjugated polymer compound, The conjugated polymer compound is a squarylium compound having a structure represented by the following general formula (3) or a croconium compound having a structure represented by the following general formula (4), or The conjugated polymer compound is a squarylium compound having a structure represented by the following general formula (5) or a croconium compound having a structure represented by the following general formula (6): A photoelectric conversion element characterized by: 【Chemistry 15】 [In general formulas (3) and (4), R １ ~R ４ each independently represents an alkyl group, a phenyl group, or a pyridyl group. １ and L ２ each independently represents an arylene group, a heteroarylene group, an ethynylene group, a vinylene group, or a combination thereof. 【Chemistry 16】 [In general formulas (5) and (6), L １ and L ２ each independently represents an arylene group, a heteroarylene group, an ethynylene group, a vinylene group, or a combination thereof.

3. The molecular terminals of the conjugated polymer compound are capped.

3. The photoelectric conversion element according to claim 1 or 2.

4. Detects and operates on light with wavelengths of 1000 nm or more The photoelectric conversion element according to any one of claims 1 to 3.

5. An optical sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of claims 1 to 4. An optical sensor characterized by:

6. An image sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of claims 1 to 4. An image sensor characterized by:

7. A flexible sensor using a photoelectric conversion element, The photoelectric conversion element is the photoelectric conversion element according to any one of claims 1 to 4. A flexible sensor characterized by:

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