Fused ring compound, and material for photoelectric conversion element for image pickup device, organic thin film, and photoelectric conversion element for image pickup device containing the fused ring compound

Abstract

To provide a material for a photoelectric converter for an imaging element that can achieve a photoelectric converter having a sufficiently suppressed dark current.SOLUTION: A material for a photoelectric converter for an imaging element contains a fused ring compound represented by the formula (1). [In the formula (1), R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 and R16 independently represent a hydrogen atom or a substituent, L is a single bond, an optionally substituted aromatic hydrocarbon group or an optionally substituted heteroaromatic group, and RA is an optionally substituted aromatic hydrocarbon group or an optionally substituted heteroaromatic group].SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fused ring compound, and a material for a photoelectric conversion element for an imaging device, an organic thin film, and a photoelectric conversion element for an imaging device, each containing a fused ring compound. [Background technology]

[0002] In recent years, there has been a growing expectation for the development of organic photoelectric conversion elements as photoelectric conversion elements for image sensors. For example, Patent Document 1 discloses a material for photoelectric conversion elements for image sensors, which contains a compound having a benzothienobenzothiophene skeleton. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 163349 Summary of the Invention [Problem to be solved by the invention]

[0004] Photoelectric conversion elements for image sensors are required to suppress dark current, which is a cause of image degradation. However, it has been difficult to realize photoelectric conversion elements with sufficient dark current suppression using conventional organic materials.

[0005] The present invention aims to provide a fused ring compound capable of realizing a photoelectric conversion element that exhibits sufficiently suppressed dark current and high external quantum efficiency, as well as a material for a photoelectric conversion element for an imaging element, an organic thin film, and a photoelectric conversion element for an imaging element that contain the fused ring compound. [Means for solving the problem]

[0006] The present inventors have found that a specific tetrabenzo[a,c,g,i]carbazole derivative is useful as a hole acceptor in a photoelectric conversion element for an image sensor, and that the use of the derivative can realize a photoelectric conversion element that sufficiently suppresses dark current and exhibits high external quantum efficiency, and have completed the present invention.

[0007] A first aspect of the present invention is a tetrabenzo[a,c,g,i]carbazole derivative (hereinafter also referred to as a fused ring compound) represented by the following formula (1). [ka] [In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 and R 16 each independently represents a hydrogen atom or a substituent, L represents a single bond, an aromatic hydrocarbon group which may have a substituent, or a heteroaromatic group which may have a substituent; R A represents an aromatic hydrocarbon group which may have a substituent or a heteroaromatic group which may have a substituent.]

[0008] A second aspect of the present invention is a material for a photoelectric conversion element for an imaging element, which comprises the fused ring compound according to the first aspect.

[0009] A third aspect of the present invention is an organic thin film including the material for a photoelectric conversion element for an imaging element according to the second aspect.

[0010] A fourth aspect of the present invention is a photoelectric conversion element for an imaging device, including the material for a photoelectric conversion element for an imaging device according to the second aspect. [Effects of the Invention]

[0011] According to the present invention, there are provided a fused ring compound capable of realizing a photoelectric conversion element that exhibits sufficient suppression of dark current and high external quantum efficiency, as well as a material for a photoelectric conversion element for an imaging element, an organic thin film, and a photoelectric conversion element for an imaging element, each containing the fused ring compound. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing an example of a layered structure of a photoelectric conversion element for an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described in detail.

[0014] <Fused ring compounds> The fused ring compound of this embodiment is a fused ring compound represented by the following formula (1). [ka]

[0015] In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 and R 16 (Hereinafter, R 1 ~R 16) each independently represent a hydrogen atom or a substituent. L represents a single bond, an aromatic hydrocarbon group which may have a substituent, or a heteroaromatic group which may have a substituent. R A represents an aromatic hydrocarbon group which may have a substituent or a heteroaromatic group which may have a substituent.

[0016] The fused ring compound of this embodiment has a specific fused ring skeleton and a specific substituent on N, and therefore has a high glass transition temperature and a wide band gap, making it suitable as a material for organic semiconductor devices.

[0017] The fused ring compound of this embodiment is particularly useful as a hole acceptor in a photoelectric conversion element for an imaging device, and use of the fused ring compound of this embodiment realizes a photoelectric conversion element that sufficiently suppresses dark current and exhibits high external quantum efficiency.

[0018] R 1 ~R 16 R each independently represents a hydrogen atom or a substituent. 1 ~R 16 The substituents in are alkyl groups, aromatic hydrocarbon groups, heteroaromatic groups, or -N(Ar 1 )2 group (Ar 1 represents an aromatic hydrocarbon group or a heteroaromatic group. ) is preferred, and an aromatic hydrocarbon group or a heteroaromatic group is more preferred.

[0019] R 1 ~R 16 The substituent in R may further have a substituent. 1 ~R 16 Examples of the substituent that the substituent in may further have include an alkyl group, an aromatic hydrocarbon group, a heteroaromatic group, -N(Ar 1 )2 group (Ar 1 represents an aromatic hydrocarbon group or a heteroaromatic group.

[0020] R 1 ~R 16The alkyl group in may be a linear, branched, or cyclic alkyl group. The number of carbon atoms in the alkyl group may be, for example, 1 to 18, preferably 1 to 12, more preferably 1 to 10, and even more preferably 1 to 6. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a cyclopropyl group, and a cyclohexyl group.

[0021] R 1 ~R 16 The aromatic hydrocarbon group in the formula (I) represents a monovalent group obtained by removing one hydrogen atom from an aromatic hydrocarbon. The aromatic hydrocarbon group may have, for example, 6 to 30 carbon atoms, preferably 6 to 15 carbon atoms, and more preferably 6 to 12 carbon atoms. The aromatic hydrocarbon group may be a monocyclic aromatic hydrocarbon group, an aromatic hydrocarbon group in which two or more aromatic rings are linked together, or a condensed-ring aromatic hydrocarbon group. The aromatic hydrocarbon group may be, for example, a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, or the like, and is preferably a phenyl group, a biphenyl group, or a naphthyl group.

[0022] R 1 ~R 16 The heteroaromatic group in the formula (I) represents a monovalent group obtained by removing one hydrogen atom from a heteroaromatic compound. The number of carbon atoms in the heteroaromatic group may be, for example, 3 to 36, preferably 3 to 22, and more preferably 3 to 10. The heteroaromatic group may be a monocyclic heteroaromatic group, a heteroaromatic group having two or more linked aromatic rings, or a fused heteroaromatic group. Examples of heteroaromatic groups include groups obtained by removing one hydrogen atom from a heteroaromatic compound such as furan, benzofuran, dibenzofuran, thiophene, benzothiophene, dibenzodiphene, pyrrole, indole, carbazole, imidazole, benzimidazole, pyridine, pyrimidine, and triazine. The heteroaromatic group is preferably a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, or a pyridyl group, and more preferably a carbazolyl group.

[0023] R 1 ~R16 Ar in 1 represents an aromatic hydrocarbon group or a heteroaromatic group, and two Ar 1 may be the same or different. 1 The aromatic hydrocarbon group in 1 ~R 16 Examples of the aromatic hydrocarbon groups include the same groups as those in Ar 1 The heteroaromatic group in the formula (I) is the same as the above-mentioned R 1 ~R 16 Examples of the heteroaromatic groups are the same as those in R 1 ~R 16 In Ar 1 is preferably an aromatic hydrocarbon group, more preferably a phenyl group, a biphenyl group or a naphthyl group.

[0024] R 1 ~R 16 The alkyl group, aromatic hydrocarbon group, heteroaromatic group and Ar 1 As for R 1 ~R 16 alkyl groups, aromatic hydrocarbon groups, heteroaromatic groups, and Ar 1 Examples include the same groups as those shown in the above.

[0025] From the viewpoint of ease of synthesis, the fused ring compound of this embodiment is 1 and R 16 and R 8 and R 9 are preferably the same group, and R 1 , R 8 , R 9 and R 16 In addition, from the viewpoint of ease of synthesis, the fused ring compound of this embodiment is preferably 2 and R 15 and R 7 and R 10 are preferably the same group, and R 2 , R 7 , R 10 and R 15In addition, from the viewpoint of ease of synthesis, the fused ring compound of this embodiment is preferably 3 and R 14 and R 6 and R 11 are preferably the same group, and R 3 , R 6 , R 11 and R 14 In addition, in the fused ring compound of this embodiment, R 4 and R 13 and R 5 and R 12 are preferably the same group, and R 4 , R 5 , R 12 and R 13 It is more preferred that these are the same group.

[0026] R 1 ~R 16 is preferably a hydrogen atom, from the viewpoint of obtaining the above-mentioned effects more significantly.

[0027] L represents a single bond, an aromatic hydrocarbon group which may have a substituent, or a heteroaromatic group which may have a substituent. L represents a bond between the tetrabenzo[a,c,g,i]carbazole skeleton and R A It should be noted that L is a single bond when it is a divalent group connecting the tetrabenzo[a,c,g,i]carbazole skeleton and R A This means that the and are directly bonded.

[0028] Examples of the substituent that the aromatic hydrocarbon group in L may have include an alkyl group, an aromatic hydrocarbon group, a heteroaromatic group, -N(Ar 1 ) 2 and the like.

[0029] Examples of the substituent that the heteroaromatic group in L may have include an alkyl group, an aromatic hydrocarbon group, a heteroaromatic group, -N(Ar 1 ) 2 and the like.

[0030] The aromatic hydrocarbon group in L represents a divalent group obtained by removing two hydrogen atoms from an aromatic hydrocarbon. The aromatic hydrocarbon group may have, for example, 6 to 30 carbon atoms, preferably 6 to 15, and more preferably 6 to 12. The aromatic hydrocarbon group may be a monocyclic aromatic hydrocarbon group, an aromatic hydrocarbon group in which two or more aromatic rings are linked, or a fused-ring aromatic hydrocarbon group. Examples of the aromatic hydrocarbon group include a phenylene group, a biphenylene group, and a naphthylene group.

[0031] The heteroaromatic group represented by L represents a divalent group obtained by removing two hydrogen atoms from a heteroaromatic compound. The number of carbon atoms in the heteroaromatic group may be, for example, 3 to 36, preferably 3 to 22, and more preferably 3 to 10. The heteroaromatic group may be a monocyclic heteroaromatic group, a heteroaromatic group having two or more linked aromatic rings, or a fused-ring heteroaromatic group. Examples of heteroaromatic groups include groups obtained by removing two hydrogen atoms from heteroaromatic compounds such as furan, benzofuran, dibenzofuran, thiophene, benzothiophene, dibenzodiphene, pyrrole, indole, carbazole, imidazole, benzimidazole, pyridine, pyrimidine, and triazine. The heteroaromatic group is preferably a group obtained by removing two hydrogen atoms from a heteroaromatic compound selected from the group consisting of dibenzofuran, dibenzothiophene, carbazole, and thiophene, and more preferably a group obtained by removing two hydrogen atoms from carbazole (carbazolylene group).

[0032] The substituents that L may have include alkyl groups, aromatic hydrocarbon groups, heteroaromatic groups, and Ar 1 As for R 1 ~R 16 alkyl groups, aromatic hydrocarbon groups, heteroaromatic groups, and Ar 1 Examples include the same groups as those shown in the above.

[0033] L is preferably a single bond, a phenylene group, a biphenylene group, a naphthylene group or a carbazolylene group, more preferably a single bond or a carbazolylene group.

[0034] R A represents an aromatic hydrocarbon group which may have a substituent or a heteroaromatic group which may have a substituent.

[0035] R A The aromatic hydrocarbon group in the formula (I) represents a monovalent group obtained by removing one hydrogen atom from an aromatic hydrocarbon. The aromatic hydrocarbon group may have, for example, 6 to 30 carbon atoms, preferably 6 to 15 carbon atoms, and more preferably 6 to 12 carbon atoms. The aromatic hydrocarbon group may be a monocyclic aromatic hydrocarbon group, an aromatic hydrocarbon group in which two or more aromatic rings are linked together, or a condensed-ring aromatic hydrocarbon group. The aromatic hydrocarbon group may be, for example, a phenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, or the like, and is preferably a phenyl group, a biphenyl group, or a naphthyl group.

[0036] R A The heteroaromatic group in the formula (I) represents a monovalent group obtained by removing one hydrogen atom from a heteroaromatic compound. The number of carbon atoms in the heteroaromatic group may be, for example, 3 to 36, preferably 3 to 22, and more preferably 3 to 10. The heteroaromatic group may be a monocyclic heteroaromatic group, a heteroaromatic group having two or more linked aromatic rings, or a fused heteroaromatic group. Examples of heteroaromatic groups include groups obtained by removing one hydrogen atom from a heteroaromatic compound such as furan, benzofuran, dibenzofuran, thiophene, benzothiophene, dibenzodiphene, pyrrole, indole, carbazole, imidazole, benzimidazole, pyridine, pyrimidine, and triazine. The heteroaromatic group is preferably a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, or a pyridyl group, and more preferably a carbazolyl group.

[0037] R A The alkyl group, aromatic hydrocarbon group, heteroaromatic group and Ar 1 As for R 1 ~R 16 alkyl groups, aromatic hydrocarbon groups, heteroaromatic groups, and Ar 1 Examples include the same groups as those shown in the above.

[0038] Examples of the fused ring compound of this embodiment include fused ring compounds represented by the following formulae (1A-1) to (1A-12), (1B-1) to (1B-32), and (1C-1) to (1C-20).

[0039] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0040] Of the above, the fused ring compounds of this embodiment are preferably fused ring compounds represented by any one of formulas (1B-1) to (1B-32) and (1C-1) to (1C-20), and more preferably fused ring compounds represented by formulas (1C-1) to (1C-20).

[0041] In the fused ring compound of this embodiment, from the viewpoint of more significantly exhibiting the above-mentioned effects, L and R A At least one of the groups is preferably a group having a carbazole ring.

[0042] In the fused ring compound of this embodiment, the tetrabenzo[a,c,g,i]carbazole skeleton and the carbazolyl ring are preferably directly bonded, and L is a carbazolylene group, or L is a single bond and R A is more preferably a carbazolyl group. This tends to improve the amorphousness of the fused ring compound, and the above-mentioned effects tend to be more pronounced. Examples of such fused ring compounds include fused ring compounds represented by formulas (1C-1) to (1C-20).

[0043] In order to more significantly achieve the above-described effects, the fused ring compound of this embodiment may further comprise a compound in which L is a carbazolylene group and R A is particularly preferably an aromatic hydrocarbon group. Examples of such fused ring compounds include fused ring compounds represented by any one of formulas (1C-1) to (1C-10) and formulas (1C-13) to (1C-20).

[0044] The glass transition temperature of the fused ring compound of this embodiment may be, for example, 80° C. or higher, and from the viewpoint of being more suitable as a material for a photoelectric conversion element for an imaging device, it is preferably 100° C. or higher, and more preferably 130° C. or higher. The glass transition temperature of the fused ring compound of this embodiment may be, for example, 300° C. or lower, and from the viewpoint of being more suitable as a material for a photoelectric conversion element for an imaging device, it is preferably 250° C. or lower, and more preferably 200° C. or lower.

[0045] The method for producing the fused ring compound of this embodiment is not particularly limited, and it can be produced, for example, by the following synthetic route.

[0046] <Synthetic Route> The fused ring compound of the present embodiment can be produced by reacting a compound represented by Formula (P) with a compound represented by Formula (B) in the presence of a palladium catalyst, optionally using an oxidizing agent and an acid. [ka]

[0047] In formula (P), L and R A has the same meaning as above. In formula (B), R 1 ~R 8 is the same as above, and X 1 and X 2 each independently represents a halogen atom (for example, a chlorine atom, a bromine atom, or an iodine atom).

[0048] X 1 and X 2 are preferably iodine atoms from the viewpoint of reaction efficiency.

[0049] As the palladium catalyst, for example, tetrakis(triphenylphosphine)palladium(0), palladium(II) chloride, palladium(II) acetate, tetrakis(acetonitrile)palladium(II) tetrafluoroborate, etc. can be suitably used.

[0050] As the oxidizing agent, for example, silver pivalsan (AgOPiv), silver carbonate (I), etc. can be suitably used.

[0051] As the acid, for example, trifluoromethanesulfonic acid or the like can be suitably used.

[0052] <Photoelectric conversion element materials for imaging devices> The material for a photoelectric conversion element for an imaging element of this embodiment contains the above-described fused ring compound.

[0053] The photoelectric conversion element material for an image sensor of this embodiment is a material for constituting an organic layer in a photoelectric conversion element for an image sensor. By using the photoelectric conversion element material for an image sensor of this embodiment, it is possible to fabricate a photoelectric conversion element that sufficiently suppresses dark current and exhibits high external quantum efficiency.

[0054] The material for a photoelectric conversion element for an imaging device of this embodiment may be, for example, a hole transport material, an electron blocking material, a photoelectric conversion material, etc. That is, the material for a photoelectric conversion element for an imaging device of this embodiment may be a material that constitutes a hole transport layer, an electron blocking layer, a photoelectric conversion layer, etc. in a photoelectric conversion element for an imaging device.

[0055] Since the fused ring compound of this embodiment functions favorably as a hole acceptor in a photoelectric conversion element for an imaging device, the material for a photoelectric conversion element for an imaging device of this embodiment can be particularly favorably used as a hole transport material, an electron blocking material, or a photoelectric conversion material. That is, the material for a photoelectric conversion element for an imaging device of this embodiment can be particularly favorably used as a material constituting a hole transport layer, an electron blocking layer, or a photoelectric conversion layer in a photoelectric conversion element for an imaging device.

[0056] <Photoelectric conversion element for image sensor> The photoelectric conversion element for an image sensor of this embodiment includes the above-mentioned material for a photoelectric conversion element for an image sensor. The photoelectric conversion element for an image sensor of this embodiment may include an upper electrode, a lower electrode, and one or more organic layers disposed between the upper electrode and the lower electrode, and at least one of the organic layers includes the above-mentioned material for a photoelectric conversion element for an image sensor. Note that each of the organic layers in the photoelectric conversion element for an image sensor of this embodiment can also be considered as an organic thin film.

[0057] The configuration of the photoelectric conversion element for an imaging device of this embodiment is not particularly limited, but examples thereof include the following configurations (i) to (v). (i) Lower electrode / photoelectric conversion layer / upper electrode (ii) Lower electrode / electron transport layer (hole blocking layer) / photoelectric conversion layer / upper electrode (iii) Lower electrode / photoelectric conversion layer / hole transport layer (electron blocking layer) / upper electrode (iv) Lower electrode / electron transport layer (hole blocking layer) / photoelectric conversion layer / hole transport layer (electron blocking layer) / upper electrode (v) Lower electrode / electron transport layer (hole blocking layer) / photoelectric conversion layer / hole transport layer (electron blocking layer) / buffer layer / upper electrode

[0058] The buffer layer may be replaced with a layer having a different name or function, as needed, such as a hole injection layer or a work function adjustment layer.

[0059] The photoelectric conversion element for an imaging device may contain the material for a photoelectric conversion element for an imaging device in at least one layer selected from the group consisting of an electron transport layer (hole blocking layer), a photoelectric conversion layer, a hole transport layer (electron blocking layer), and a buffer layer. Furthermore, the photoelectric conversion element for an imaging device preferably contains the material for a photoelectric conversion element for an imaging device in the photoelectric conversion layer and / or the hole transport layer (electron blocking layer), and more preferably contains the material for a photoelectric conversion element for an imaging device in the hole transport layer (electron blocking layer). The material for a photoelectric conversion element for an imaging device may be contained in multiple layers of the photoelectric conversion element for an imaging device.

[0060] Hereinafter, the conversion element for an imaging device according to this embodiment will be described in more detail using the configuration (v) above as an example, with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the layered structure of the photoelectric conversion element for an imaging device according to this embodiment.

[0061] 1 includes, in this order, a substrate 1, a lower electrode 2, an electron transport layer (hole blocking layer) 3, a photoelectric conversion layer 4, a hole transport layer (electron blocking layer) 5, a buffer layer 6, and an upper electrode 7. Note that in the photoelectric conversion element for an image sensor of this embodiment, some of these layers may be omitted, and other layers may be added.

[0062] In the photoelectric conversion element 100 for an imaging device, light is incident from below the transparent lower electrode 2. Furthermore, a voltage is applied to the photoelectric conversion element 100 for an imaging device so that, of the charges (holes and electrons) generated in the photoelectric conversion layer 4, the electrons move to the lower electrode 2 and the holes move to the upper electrode 7. That is, in the photoelectric conversion element 100 for an imaging device, the lower electrode 2 serves as an electron collecting electrode and the upper electrode 7 serves as a hole collecting electrode.

[0063] The photoelectric conversion element 100 for an imaging device contains a material for a photoelectric conversion element for an imaging device in at least one layer selected from the group consisting of an electron transport layer (hole blocking layer) 3, a photoelectric conversion layer 4, a hole transport layer (electron blocking layer) 5, and a buffer layer 6. The photoelectric conversion element 100 for an imaging device preferably contains the material for a photoelectric conversion element for an imaging device in the photoelectric conversion layer 4 and / or the hole transport layer (electron blocking layer) 5, and more preferably contains the material for a photoelectric conversion element for an imaging device in the hole transport layer (electron blocking layer) 5. The material for a photoelectric conversion element for an imaging device may be contained in multiple layers of the photoelectric conversion element 100 for an imaging device.

[0064] Hereinafter, each layer will be described in detail using the photoelectric conversion element 100 for an imaging element in which the hole transport layer (electron blocking layer) 5 contains a material for a photoelectric conversion element for an imaging element as an example.

[0065] [Board 1] There are no particular limitations on the substrate 1, and examples thereof include a glass plate, a quartz plate, a plastic plate, etc. In a configuration in which light is incident from the substrate 1 side, it is preferable that the substrate 1 has high transmittance (for example, a transmittance of 80% or more, preferably a transmittance of 90% or more) for the wavelength of the incident light.

[0066] [Bottom electrode 2] A lower electrode 2 is provided on a substrate 1 . In the case of a photoelectric conversion element for an imaging device configured so that light passes through the lower electrode 2 and enters the photoelectric conversion layer, it is preferable that the lower electrode 2 has high transparency (for example, a transmittance of 80% or more, preferably a transmittance of 90% or more) to the wavelength of the incident light.

[0067] There are no particular limitations on the material forming the lower electrode 2. From the viewpoint of excellent light transmittance, the material forming the lower electrode 2 may be, for example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, aluminum-doped tin oxide, magnesium-indium oxide, nickel-tungsten oxide, other metal oxides, metal nitrides such as gallium nitride, metal selenides such as zinc selenide, or metal sulfides such as zinc sulfide.

[0068] In the case of a photoelectric conversion element for an imaging device configured so that light enters the photoelectric conversion layer only from the upper electrode 7 side, the transmission characteristics of the lower electrode 2 are not important. Therefore, the material constituting the lower electrode 2 in this case may be, for example, gold, iridium, molybdenum, palladium, platinum, etc.

[0069] [Electron transport layer (hole blocking layer) 3] An electron transport layer (hole blocking layer) 3 is provided between the lower electrode 2 and a photoelectric conversion layer 4, which will be described later. The electron transport layer (hole blocking layer) 3 has the role of transporting electrons generated in the photoelectric conversion layer 4 to the lower electrode 2 and the role of blocking holes generated in the photoelectric conversion layer 4 from moving to the lower electrode 2.

[0070] The electron transport layer (hole blocking layer) 3 may have a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions. The electron transport layer (hole blocking layer) 3 may have, for example, a two-layer structure including a layer made of a material specialized for hole blocking properties and adjacent to the photoelectric conversion layer 4, and a layer made of a material specialized for electron transport properties and adjacent to the lower electrode 2.

[0071] The electron transport layer (hole blocking layer) 3 may be a layer containing a conventionally known electron transport material, such as bis(8-hydroxyquinolinato)manganese, tris(8-hydroxyquinolinato)aluminum, tris(2-methyl-8-hydroxyquinolinato)aluminum, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), Bphen (4,7-diphenyl-1,10-phenanthroline), BAlq (bis(2-methyl-8-quinolinolato)-4-(phenylphenolato)aluminum), 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine, N,N'-diphenyl-1,4,5,8-naphthalenetetracarboxylic acid diimide, and N,N'-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide.

[0072] [Photoelectric conversion layer 4] A photoelectric conversion layer 4 is provided between the electron transport layer (hole blocking layer) 3 and a hole transport layer (electron blocking layer) 5 described later. The photoelectric conversion layer 4 contains a material having a photoelectric conversion function.

[0073] The photoelectric conversion layer 4 may have a single layer structure made of one or more materials, or may have a laminate structure made of multiple layers of the same composition or different compositions.

[0074] Examples of photoelectric conversion layers having a single layer structure made of one type of material include photoelectric conversion layers made of materials such as coumarin and its derivatives, quinacridone and its derivatives, and phthalocyanine and its derivatives.

[0075] Examples of photoelectric conversion layers having a single layer structure made of two or more materials include a photoelectric conversion layer containing (i) a first material selected from the group consisting of coumarin and its derivatives, quinacridone and its derivatives, and phthalocyanine and its derivatives, and (ii) a second material selected from the group consisting of fullerene and its derivatives. The photoelectric conversion layer may further contain (iii) a hole transport material. The photoelectric conversion layer 4 made of these materials may be formed, for example, by vapor deposition using a mixed powder obtained by mixing powders of the respective materials, or by co-evaporation of the respective materials in any ratio.

[0076] (i) Specific examples of coumarin derivatives include coumarin 6 and coumarin 30. Specific examples of quinacridone derivatives include N,N-dimethylquinacridone. Specific examples of phthalocyanine derivatives include boron subphthalocyanine chloride and boron subnaphthalocyanine chloride (SubNC).

[0077] (ii) Specific examples of fullerenes and derivatives thereof include

[60] fullerene,

[70] fullerene, and [6,6]-phenyl-C61-methyl butyrate (

[60] PCBM).

[0078] (iii) The hole transport material may be a known hole transport material. Examples of the hole transport material include aromatic tertiary amine compounds, naphthalene compounds, anthracene compounds, tetracene compounds, pentacene compounds, phenanthrene compounds, pyrene compounds, perylene compounds, fluorene compounds, carbazole compounds, indole compounds, pyrrole compounds, picene compounds, thiophene compounds, benzotrifuran compounds, benzotrithiophene compounds, naphthodithiophene compounds, naphthothienothiophene compounds, benzodifuran compounds, benzodithiophene compounds, benzothiophene compounds, naphthobisbenzothiophene compounds, chrysenodithiophene compounds, benzothienobenzothiophene compounds, and indolocarbazole compounds. Among these, fluorene compounds, naphthodithiophene compounds, naphthothienothiophene compounds, benzodifuran compounds, benzothiophene compounds, naphthobisbenzothiophene compounds, chrysenodithiophene compounds, benzothienobenzothiophene compounds, indolocarbazole compounds, and the like are preferred, and fluorene compounds, chrysenodithiophene compounds, benzothienobenzothiophene compounds, and indolocarbazole compounds are more preferred.

[0079] Specific examples of hole transport materials include 9,9'-(9,9'-spirobi[9H-fluorene]-2,7'-diyl)bis[9H-carbazole], 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DiPh-BTBT), benzo[1,2-b:3,4-b':5,6-b'']trifuran compounds, benzo[1,2-b:3,4-b':5,6-b'']trithiophene compounds, naphtho[1,2-b:5,6-b']dithiophene, naphtho[2,3-b]naphtho[2',3' :4,5]thieno[2,3-d]thiophene, benzo[1,2-b:4,5-b']difuran, benzo[1,2-b:4,5-b']dithiophene, benzo[1,2-b:4,5-b']bis[1]benzothiophene, naphtho[1,2-b:5,6-b']bis[1]benzothiophene, chryseno[1,2-b:8,7-b']dithiophene, [1]benzothieno[3,2-b][1]benzothiophene, compounds represented by the following formula (ic-1), compounds represented by the following formula (ic-2), and the like. [ka]

[0080] The material having the photoelectric conversion function described above may be contained only in the photoelectric conversion layer 4, or may also be contained in layers other than the photoelectric conversion layer 4. For example, layers adjacent to the photoelectric conversion layer 4 (electron transport layer (hole blocking layer) 3, hole transport layer (electron blocking layer) 5) may contain a material having the photoelectric conversion function.

[0081] [Hole transport layer (electron blocking layer) 5] A hole transport layer (electron blocking layer) 5 is provided between the photoelectric conversion layer 4 and a buffer layer 6 described later.

[0082] The hole transport layer (electron blocking layer) 5 has a role of transporting holes generated in the photoelectric conversion layer 4 toward the upper electrode 7, and a role of blocking electrons generated in the photoelectric conversion layer 4 from moving toward the upper electrode 7. The hole transport layer (electron blocking layer) 5 preferably contains the above-mentioned material for a photoelectric conversion element for an imaging element.

[0083] The hole transport layer (electron blocking layer) 5 may have a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions. The hole transport layer (electron blocking layer) 5 may have, for example, a two-layer structure including a layer made of a material specialized for electron blocking properties and adjacent to the photoelectric conversion layer 4, and a layer made of a material specialized for hole transport properties and adjacent to the buffer layer 6.

[0084] The hole transport layer (electron blocking layer) 5 may further contain a conventionally known hole transport material in addition to the above-mentioned materials for a photoelectric conversion element for an imaging device. Preferred compounds and specific examples of the conventionally known hole transport material include the same as the hole transport materials described in the section on the photoelectric conversion layer 4.

[0085] [Buffer layer 6] A buffer layer 6 is provided between the hole transport layer (electron blocking layer) 5 and the upper electrode 7, which will be described later. When the upper electrode 7 is formed by sputtering, the buffer layer 6 serves to reduce damage to the organic layer (for example, the hole transport layer (electron blocking layer) 5) during sputtering. The buffer layer 6 also serves to efficiently accept holes from the hole transport layer (electron blocking layer) 5 by adjusting the work function of the buffer layer 6, and is also called a hole injection layer or a work function adjustment layer.

[0086] The material forming the buffer layer 6 may be a known material, such as naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTCDA), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN), or the like.

[0087] [Top electrode 7] An upper electrode 7 is provided on the buffer layer 6 . The material of the upper electrode 7 is not particularly limited, and may be, for example, sodium, sodium-potassium alloy, magnesium, lithium, a magnesium / copper mixture, silver, a magnesium / silver mixture, aluminum, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, indium, a lithium / aluminum mixture, or a rare earth metal.

[0088] [How each layer is formed] Each layer other than the lower electrode 2 and the upper electrode 7 can be formed by forming the material of each layer (and, if necessary, a binder resin, a solvent, etc.) into a thin film by a known method such as vacuum deposition, spin coating, casting, or LB (Langmuir-Blodgett) method.

[0089] The thickness of each layer other than the lower electrode 2 and the upper electrode 7 is not particularly limited and can be selected appropriately depending on the situation. The thickness of each layer other than the lower electrode 2 and the upper electrode 7 is usually in the range of 5 nm to 5 μm.

[0090] The lower electrode 2 and the upper electrode 7 can be formed by thinning an electrode material by a method such as vapor deposition or sputtering.

[0091] When the lower electrode 2 and the upper electrode 7 have a pattern, the pattern can be formed, for example, by vapor deposition, sputtering, etc. through a mask of a desired shape. Alternatively, after forming a thin film by vapor deposition, sputtering, etc., a pattern of a desired shape may be formed by photolithography.

[0092] The thickness of the lower electrode 2 and the upper electrode 7 may be, for example, 1 μm or less, and is preferably 10 nm or more and 200 nm or less.

[0093] The materials constituting the lower electrode 2 and the upper electrode 7 may be interchanged as necessary (also called an inverted structure). In this case, the photoelectric conversion element for an imaging device is configured so that light passes through the upper electrode 7 and enters the photoelectric conversion layer 4.

[0094] An imaging element including the photoelectric conversion element of this embodiment can be applied to, for example, an imaging element of a digital camera, a digital video camera, an imaging element built into a mobile phone, or the like.

[0095] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. [Example]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0097] (Synthesis Example 1: Synthesis of Compound (1A-1)) Compound (1A-1) was synthesized by the following method. [ka]

[0098] Under a nitrogen stream, 1-phenylpyrrole (10 mg, 0.07 mmol), 2,2'-diiodobiphenyl (83 mg, 0.21 mmol), silver pivalsan (AgOPiv) (56 mg, 0.27 mmol), and tetrakis(acetonitrile)palladium(II) tetrafluoroborate (3 mg, 7 μmol) were added to a glass tube with a screw cap. Next, 1,2-dichloroethane (1.5 mL) and trifluoroacetic acid (25 μL) were added, and the mixture was stirred at 50 °C for 1 hour. After cooling to room temperature, the mixture was passed through silica gel using chloroform, and then an aqueous sodium bicarbonate solution was added and stirred. The aqueous and organic layers were separated, and the resulting organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane to hexane:chloroform = 10:1 (v / v)) to obtain 14.6 mg (0.033 mmol) of colorless powder of compound (1A-1) (yield 47%). The sublimation temperature of compound (1A-1) was 260 °C, and it was confirmed that the sublimed product of compound (1A-1) was in powder form.

[0099] The identity of compound (1A-1) 1 This was measured by H-NMR. 1 H-NMR(CDCl3)δ(ppm):9.04-9.00(m,2H),8.78(d,2H),8.76-8.72(m,2H), 7.83-7.71(m,5H),7.65-7.59(m,4H),7.52-7.48(m,2H),7.24-7.19(m,4H)

[0100] (Synthesis Example 2: Synthesis of Compound (1B-1)) Compound (1B-1) was synthesized by the following method. [ka]

[0101] The reaction and purification were carried out in the same manner as in Synthesis Example 1, except that 1-phenylpyrrole was replaced with 1-biphenylpyrrole (15.3 mg, 0.07 mmol), to obtain 10.2 mg (0.020 mmol) of colorless powder of compound (1B-1) (yield 28%). The sublimation temperature of compound (1B-1) was 280°C, and it was confirmed that the sublimed product of compound (1B-1) was in powder form.

[0102] The identification of compound (1B-1) 1 This was measured by H-NMR. 1 H-NMR(CDCl3)δ(ppm):9.04-9.00(m,2H),8.79(d,2H),8.76-8.72(m,2H),8.01(d,2H),7.88 (d,2H),7.79(d,2H),7.66-7.57(m,6H),7.54-7.47(m,3H),7.35(dd,2H),7.26-7.21(m,2H)

[0103] (Synthesis Example 3: Synthesis of Compound (1C-17)) Compound (1C-17) was synthesized by the following method. [ka]

[0104] The reaction and purification were carried out in the same manner as in Synthesis Example 1, except that 1-phenylpyrrole was replaced with 9-phenyl-4-(pyrrol-1-yl)carbazole (21.6 mg, 0.07 mmol), to obtain 21.3 mg (0.035 mmol) of colorless powder of compound (1C-17) (yield 50%). The sublimation temperature of compound (1C-17) was 320°C, and it was confirmed that the sublimed product of compound (1C-17) was in powder form.

[0105] Compound (1C-17) was identified by 1H-NMR measurement. 1H-NMR(CDCl3)δ(ppm):9.16(dd,2H),8.74(t,4H),7.82(dd,1H),7.74-7.54(m,11H),7 .40(td,2H),7.31(d,1H),7.19(dd,2H),7.14(td,1H),7.03(td,2H),6.61-6.53(m,2H)

[0106] (Measurement of glass transition temperature) Measurements were performed using a DSC7020 manufactured by Hitachi High-Tech Science Corp. The results are shown in Table 1.

[0107] (Band gap measurement) The band gap was calculated from the HOMO value of the compound's vapor-deposited film (100 nm thick, deposited on a quartz substrate at a rate of 0.10 nm / sec) and the wavelength edge of the absorption spectrum. The HOMO value of the vapor-deposited film was measured using an airborne photoelectron spectrometer (AC-3) manufactured by Riken Keiki Co., Ltd., and the absorption spectrum was measured using a UV-Vis-NIR spectrophotometer (V-750) manufactured by JASCO Corporation. The results are shown in Table 1.

[0108] [Table 1]

[0109] [Element Example A-1] As shown in Figure 1, a photoelectric conversion element for an imaging device having a layered structure consisting of a substrate 1 / lower electrode 2 / electron transport layer (hole blocking layer) 3 / photoelectric conversion layer 4 / hole transport layer 5 / buffer layer 6 / upper electrode 7 was fabricated, and its characteristics were evaluated.

[0110] (Preparation of substrate 1 and lower electrode 2) A glass substrate with an indium-tin oxide (ITO) transparent electrode, patterned with a 2 mm wide stripe of ITO (110 nm thick), was prepared as a substrate with a lower electrode on its surface. The substrate was then washed with isopropyl alcohol and then subjected to surface treatment using ozone and ultraviolet light.

[0111] (Vacuum deposition) Each layer was laminated on the surface-treated substrate by vacuum deposition. Specifically, a glass substrate with an ITO transparent electrode was placed in a vacuum deposition chamber. -5 The pressure was reduced to Pa. Then, each layer was prepared in the following order. (1) Preparation of electron transport layer (hole blocking layer) 3 Sublimation-purified 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine was deposited at a rate of 0.10 nm / sec to form a 10 nm thick film, thereby forming an electron transport layer (hole blocking layer) 3 . (2) Preparation of photoelectric conversion layer 4 A 120 nm film was formed by mixing N,N-dimethylquinacridone and C60 in a mass ratio of 4:1 to produce photoelectric conversion layer 4. The film formation rate was 0.15 nm / second. (3) Preparation of hole transport layer (electron blocking layer) 5 The sublimation-purified compound (1A-1) was formed into a film having a thickness of 10 nm at a rate of 0.10 nm / second to form a hole transport layer 5. (4) Fabrication of buffer layer 6 Sublimation-purified 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN) was deposited at a rate of 0.10 nm / sec to form a 10 nm thick film, thereby forming a buffer layer 6 .

[0112] (Fabrication of upper electrode 7) A metal mask was placed so as to be perpendicular to the ITO stripes on the substrate, and an upper electrode 7 was formed. The upper electrode was formed by depositing a silver film to a thickness of 80 nm. The silver film deposition rate was 0.1 nm / sec.

[0113] Using the above method, an area of ​​4 mm 2 A photoelectric conversion element for an imaging device was fabricated. The thickness of each layer was measured using a stylus film thickness gauge (DEKTAK, manufactured by Bruker). The fabricated element was sealed in a nitrogen atmosphere glove box with oxygen and moisture concentrations of 1 ppm or less. Sealing was performed using a glass sealing cap and bisphenol F-type epoxy resin (manufactured by Nagase ChemteX Corporation).

[0114] [Element Example A-2] A photoelectric conversion element for an imaging device was prepared in the same manner as in Element Example A-1, except that compound (1C-17) was used instead of compound (1A-1) in the preparation of the hole transport layer (electron blocking layer) 5.

[0115] [Comparative element example X-1] A photoelectric conversion element for an imaging device was prepared in the same manner as in Element Example A-1, except that the following 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DiPh-BTBT) was used instead of compound (1A-1) in the preparation of the hole transport layer (electron blocking layer) 5. [ka]

[0116] (Measurement of dark current and external quantum efficiency) The photoelectric conversion element for an image sensor fabricated as described above was subjected to an application of a voltage of 2.5 V (absolute value) so that electrons were transported to the bottom electrode 2 side and holes to the top electrode 7 side. The current in the dark (dark current) and external quantum efficiency were evaluated. Dark current was measured using a Keithley Source Measure Unit 2636B. External quantum efficiency was measured using a solar cell spectral response measurement system (Soma Optical Co., Ltd.) with irradiated light of 560 nm wavelength and 50 μW / cm2 intensity. The results are shown in Table 2. The results shown in Table 2 are relative values, with the results for Comparative Example X-1 used as the reference values ​​(dark current: 1.0, external quantum efficiency: 100).

[0117] [Table 2]

[0118] As shown in Table 2, the elements of the examples using the specific materials for photoelectric conversion elements for imaging devices had suppressed dark current and high external quantum efficiency compared to the elements of the comparative examples. [Explanation of symbols]

[0119] 1... substrate, 2... lower electrode, 3... electron transport layer, 4... photoelectric conversion layer, 5... hole transport layer, 6... buffer layer, 7... upper electrode, 100... photoelectric conversion element for imaging device.

Claims

1. A material for a photoelectric conversion element for an imaging element, comprising a fused ring compound represented by the following formula (1): 【Chemistry 1】 [In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R １２ , R １３ , R １４ , R １５ and R １６ each independently represents a hydrogen atom or a substituent, L represents a carbazolylene group; R Ａ represents an aromatic hydrocarbon group.

2. The R １ , the R ２ , the R ３ , the R ４ , the R ５ , the R ６ , the R ７ , the R ８ , the R ９ , the R １０ , the R １１ , the R １２ , the R １３ , the R １４ , the R １５ and the R １６ and each independently represent a hydrogen atom, an aromatic hydrocarbon group which may have a substituent, or a heteroaromatic group which may have a substituent.

3. The R １ , the R ２ , the R ３ , the R ４ , the R ５ , the R ６ , the R ７ , the R ８ , the R ９ , the R １０ , the R １１ , the R １２ , the R １３ , the R １４ , the R １５ and the R １６ The material for a photoelectric conversion element for an imaging element according to claim 1 or 2, wherein is a hydrogen atom.

4. An organic thin film comprising the material for a photoelectric conversion element for an imaging element according to any one of claims 1 to 3.

5. A photoelectric conversion element for an imaging device, comprising the material for a photoelectric conversion element for an imaging device according to any one of claims 1 to 3.

6. A fused ring compound represented by the following formula (1): 【Chemistry 2】 [In formula (1), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , R １０ , R １１ , R １２ , R １３ , R １４ , R １５ and R １６ each independently represents a hydrogen atom or a substituent, L represents a carbazolylene group; R Ａ represents an aromatic hydrocarbon group.

7. The R １ , the R ２ , the R ３ , the R ４ , the R ５ , the R ６ , the R ７ , the R ８ , the R ９ , the R １０ , the R １１ , the R １２ , the R １３ , the R １４ , the R １５ and the R １６ and each independently represent a hydrogen atom, an optionally substituted aromatic hydrocarbon group, or an optionally substituted heteroaromatic group.

8. The R １ , the R ２ , the R ３ , the R ４ , the R ５ , the R ６ , the R ７ , the R ８ , the R ９ , the R １０ , the R １１ , the R １２ , the R １３ , the R １４ , the R １５ and the R １６ The fused ring compound according to claim 6 or 7, wherein is a hydrogen atom.

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