Photoelectric conversion element and image sensor

Abstract

To provide various photoelectric conversion elements to which organic thin films are applied by using compounds with deep HOMO levels, excellent heat resistance and hole transport properties, particularly imaging elements, and optical sensors using the same.SOLUTION: An organic photoelectric conversion element includes a conductive thin film, an organic photoelectric conversion layer, a blocking layer, and a transparent conductive thin film, and the blocking layer contains a blocking material having the following properties. (1) The glass transition temperature (Tg) is 110°C or higher. (2) The highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV. (3) The hole mobility (μh) at the electric field strength of 0.25 MV / cm is 1.0x10-7<μh<1.0x10-2(cm2 / Vs).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion element, particularly to a photoelectric conversion element including an organic thin film containing a compound that satisfies specific physical property values, and to an imaging device including the photoelectric conversion element. [Background technology]

[0002] Photoelectric conversion elements are widely used in, for example, solar cells and optical sensors. Among them, image sensors, which are imaging elements, are not only used in television cameras and cameras mounted on smartphones, but are also beginning to be used in driving assistance systems, and both their applications and the market are expanding.

[0003] Until now, imaging elements have been made of inorganic materials such as Si films and Se films, and the two main imaging methods were a three-plate type that uses a prism to separate colors, and a single-plate type that uses a color filter. However, although the three-plate type has a high light utilization rate, it is difficult to make it compact because it uses a prism, while the single-plate type does not use a prism and is relatively easy to make compact, but instead uses a color filter, resulting in poor resolution and light utilization (Non-Patent Document 1).

[0004] Compared to inorganic materials, organic materials absorb light of specific wavelengths better. Therefore, by combining materials tailored to each wavelength, it is possible to construct an imaging element that can efficiently utilize light for each of the three primary colors without using a prism. This makes it possible to create a compact imaging element with high light utilization efficiency. Furthermore, there is the possibility of adding value, such as flexibility and the ability to increase the area by coating during the manufacturing process, which cannot be achieved with inorganic materials (Non-Patent Document 2).

[0005] For these reasons, photoelectric conversion elements using organic materials are expected to be developed into next-generation imaging elements, and several reports have been published. For example, there are examples using quinacridone and quinazoline derivatives in photoelectric conversion elements (Patent Document 1), examples using benzothienobenzothiophene derivatives in photoelectric conversion elements (Patent Document 2), and examples using indolocarbazole in photoelectric conversion elements (Patent Document 3). Generally, organic imaging elements are designed to achieve high contrast and low power consumption, and it is believed that performance can be improved by reducing dark current. To reduce dark current, a technique of inserting a hole-blocking layer or electron-blocking layer between the photoelectric conversion unit and the electrode unit is sometimes used.

[0006] Hole-blocking layers and electron-blocking layers are commonly used in the field of organic electronics, and are disposed at the interface between an electrode or conductive film and other films in the constituent films of a device, respectively, to control the reverse movement of holes or electrons while allowing the necessary charges to move quickly. Patent Document 4 proposes that compounds with a highest occupied molecular orbital (HOMO) level of -4.7 to -5.8 eV as electron-blocking materials are effective in efficiently transferring charges to electrodes.

[0007] High sensitivity is required for the photoelectric conversion layer, and there are several methods for achieving this. Since photoelectric conversion occurs at the interface between p-type and n-type semiconductors, the active layer has a bulk heterostructure to increase the interface area. In order to efficiently separate holes and electrons from excitons generated by light absorption, a compound with strong acceptor properties is used in the active layer.

[0008] In devices with electron blocking layers, if the active layer has a bulk heterostructure, an interface is formed between the electron blocking layer and the n-type semiconductor. When a compound with strong acceptor properties is used as the n-type semiconductor, unless a compound with an appropriate energy level is used as the electron blocking layer, electrons will transfer from the highest occupied molecular orbital (HOMO) of the organic semiconductor material to the lowest unoccupied molecular orbital (LUMO) of the strong acceptor compound (fullerene derivative in Patent Document 5), resulting in poor dark current characteristics. In the HOMO-level electron blocking layer proposed in Patent Document 4, if a material with strong acceptor properties and a deep LUMO level, such as a fullerene derivative, is used in the active layer, the energy levels of the HOMO level of the electron blocking layer and the LUMO level of the n-type semiconductor in the active layer will be close, resulting in electron transfer from the n-type semiconductor material in the active layer to the electron blocking layer, resulting in poor dark current characteristics.

[0009] In order to prevent the above electron transfer, it is necessary to deepen the HOMO level of the material used in the electron blocking layer.

[0010] Furthermore, when photoelectric conversion elements are used as optical sensors or organic imaging elements, a high response speed is also required. To increase the response speed, it is necessary to increase the mobility of the materials used in the elements, but until now, no compounds with a deep HOMO level and suitable hole mobility have been investigated as electron blocking materials for photoelectric conversion elements. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent No. 4945146 [Patent Document 2] Japanese Patent Application Publication No. 2018-170487 [Patent Document 3] Japanese Patent Application Publication No. 2018-085427 [Patent Document 4] Japanese Patent Application Publication No. 2011-187937 [Patent Document 5] Japanese Patent No. 5624987 [Patent Document 6] International Publication No. 2017 / 159684 [Non-patent literature]

[0012] [Non-Patent Document 1] Journal of the Institute of Image Information and Communications Technology, 60, 3, 291(2006) [Non-patent document 2] Adv. Mater.28,4766(2016) Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made in view of the above-mentioned current situation, and aims to provide an organic thin film for use in a photoelectric conversion element, by utilizing a compound having a deep HOMO level and excellent heat resistance and hole transport properties, and thereby to provide various photoelectric conversion elements, particularly image pickup elements, to which the organic thin film is applied, and optical sensors using the same. [Means for solving the problem]

[0014] The properties of electron-blocking materials suitable for photoelectric conversion elements include (1) excellent thermal stability, (2) a deep HOMO level, (3) hole transport ability, and (4) the ability to form films by vacuum deposition.

[0015] In order to achieve the above object, the present inventors have conducted extensive research and discovered a compound having the following properties for forming an organic thin film with the above properties. They have succeeded in creating an organic thin film that can be formed into a stable thin film by vacuum deposition, has a high glass transition temperature, and is capable of suppressing electron transfer from an n-type semiconductor, thereby completing the present invention. (1) A glass transition temperature (Tg) of 110°C or higher. (2) The highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV. (3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is 1.0x10 -7 <μh<1.0x10 -2 (cm 2 / Vs).

[0016] That is, the present invention provides an organic thin film for use in a photoelectric conversion element that satisfies the following physical properties and composition. 1) An organic photoelectric conversion element comprising a conductive thin film, an organic photoelectric conversion layer, a blocking layer, and a transparent conductive thin film, wherein the blocking layer contains a blocking material having the following properties: (1) A glass transition temperature (Tg) of 110°C or higher; (2) The highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV, (3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is 1.0x10 -7 <μh<1.0x10 -2 (cm 2 / Vs). [Effects of the Invention]

[0017] The organic thin film of the present invention, which has a deep HOMO level and hole transport capability, can be applied to various photoelectric conversion elements, thereby providing a photoelectric conversion element, particularly an image sensor, with good dark current characteristics, and a photosensor using the same. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows an example of the configuration of a photoelectric conversion element of the present invention. [Figure 2] FIG. 2 shows the structures of compounds (1-1) to (1-15) as examples of the compound represented by general formula (1). [Figure 3] FIG. 3 shows the structures of compounds (1-16) to (1-30) as examples of the compound represented by general formula (1). [Figure 4]FIG. 4 shows the structures of compounds (1-31) to (1-44) as examples of the compound represented by general formula (1). [Figure 5] FIG. 5 shows the structures of compounds (1-45) to (1-56) as examples of the compound represented by general formula (1). [Figure 6] FIG. 6 shows the structures of compounds (1-57) to (1-66) as examples of the compound represented by general formula (1). [Figure 7] FIG. 7 shows the structures of compounds (1-67) to (1-78) as examples of the compound represented by general formula (1). [Figure 8] FIG. 8 shows the structures of compounds (1-79) to (1-89) as examples of the compound represented by general formula (1). [Figure 9] FIG. 9 shows the structures of compounds (1-90) to (1-103) as examples of the compound represented by general formula (1). [Figure 10] FIG. 10 shows the structures of compounds (1-104) to (1-122) as examples of the compound represented by general formula (1). DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail.

[0020] In this specification, the term "to" is used to indicate a range. For example, "5 to 10" means "5 or more and 10 or less," and indicates a range that includes the numerical values ​​written before and after "to."

[0021] <Photoelectric conversion element> A photoelectric conversion element is an element capable of converting light energy into electrical energy, and is configured, for example, to include a conductive thin film, an organic photoelectric conversion layer, a blocking layer, and a transparent conductive thin film. The blocking layer is a hole-blocking layer or an electron-blocking layer, or the photoelectric conversion element may include both of these blocking layers. It is preferable that the photoelectric conversion element includes an electron-blocking layer as the blocking layer.

[0022] The photoelectric conversion element can reduce the dark current value by using a compound represented by the general formula (1) described later in the electron blocking layer. The thickness of the electron blocking layer is preferably smaller than the thickness of the photoelectric conversion layer, more preferably 5 to 100 nm, and even more preferably 5 to 50 nm.

[0023] <<Blocking layer>> The blocking layer contains an electron blocking material that has at least the following properties: (1) A glass transition temperature (Tg) of 110°C or higher; (2) The highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV, (3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is 1.0x10 -7 <μh<1.0x10 -2 (cm 2 / Vs).

[0024] <<<Electron Blocking Materials>>> The electron-blocking material is an organic compound forming an organic film, and the glass transition temperature of the organic compound is preferably 110°C or higher, more preferably 120°C or higher. This allows for application to a manufacturing process that includes a heating step and improves storage stability. Furthermore, the organic film formed from the organic compound of the electron-blocking material preferably has a deep HOMO level of -5.8 to -7.0 eV, more preferably -5.8 to -6.5 eV. This can suppress the transfer of charges from the n-type semiconductor contained in the bulk heterostructure photoelectric conversion layer to the electron-blocking layer. It can also reduce the leakage current of the photoelectric conversion element. Furthermore, in order to efficiently transport holes generated in the photoelectric conversion layer, the electron-blocking material should have a hole mobility (μh) of 1.0x10 at an electric field strength of 0.25 MV / cm. -6 <μh<1.0x10 -3 (cm 2 / Vs).

[0025] The electron-blocking material is not particularly limited, but is preferably a compound containing two or more fused heterocyclic groups each consisting of a five-membered heterocycle. More preferably, it is a compound represented by the following general formula (1). Specific examples of preferred compounds represented by general formula (1) are shown in Figures 2 to 10, but the electron-blocking material is not limited to these compounds.

[0026] [ka]

[0027] (In the formula, Ar1 and Ar2 may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, L1 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted triarylamine; a represents an integer of 2 to 4, b represents an integer of 0 to 2.

[0028] Specific examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" in the general formula (1) include a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrid ... Examples include a pyridinyl group, a triazinyl group, a furyl group, a thienyl group, a selenenyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, a benzoselenonyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzoselenozolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzoselenonyl group, a dibenzothienyl group, a naphthyridinyl group, a phenanthrolinyl group, an acridinyl group, a carbolinyl group, etc. Furthermore, the alkyl group may be selected from an aryl group having 6 to 30 carbon atoms and a heteroaryl group having 2 to 30 carbon atoms.

[0029] Specific examples of the "substituent" in the "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," "substituted fused polycyclic aromatic group," or "substituted triphenylamines" in general formula (1) include deuterium atoms, cyano groups, nitro groups; halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; silyl groups such as trimethylsilyl groups and triphenylsilyl groups; linear or branched alkyl groups having 1 to 6 carbon atoms such as methyl groups, ethyl groups, and propyl groups; linear or branched alkyloxy groups having 1 to 6 carbon atoms such as methyloxy groups, ethyloxy groups, and propyloxy groups; alkenyl groups such as vinyl groups and allyl groups; aryloxy groups such as phenyloxy groups and tolyloxy groups; arylalkyloxy groups such as benzyloxy groups and phenethyloxy groups. Examples of the substituent include an oxy group; an aromatic hydrocarbon group or a condensed polycyclic aromatic group such as a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, or a triphenylenyl group; and an aromatic heterocyclic group such as a pyridyl group, a furyl group, a thienyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbolinyl group, and these substituents may be further substituted with the substituents exemplified above.

[0030] In general formula (1), L1 may be a divalent to pentavalent group, which may have a substituent, such as benzene, biphenyl, ο-terphenyl, m-terphenyl, p-terphenyl, 1,3,5-triphenylbenzene, naphthyl, phenanthrene, triphenylene, furan, thiophene, dibenzofuran, dibenzothiophene, 9,9-spirobi[9H-fluorene], 9,9-dimethylfluorene, 9,9-diphenylfluorene, triphenylamine, 9-phenylcarbazole, pyridine, pyrimidine, 1,3,5-triazine, 2,6-diphenylpyridine, or 2,4,6-triphenylpyrimidine.

[0031] In the general formula (1), Ar1 may have a structure selected from the group consisting of the following general formulae (2-a) to (2-t).

[0032] [ka]

[0033] (In the formula, X represents S, O, Se, C—R1R2, Si—R1R2, or N—Ar3; Y represents S, O, Se, Si—R1R2, or N—Ar3; Z represents N or C-R3; R1 to R3 may be the same or different and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, an optionally substituted linear or branched alkyl group of 1 to 8 carbon atoms, an optionally substituted cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 8 carbon atoms, an optionally substituted cycloalkyloxy group of 2 to 10 carbon atoms, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group; Adjacent groups of R1 to R3 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring; Ar3 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group; The dashed line indicates the binding site.)

[0034] Specific examples of the "C-C linear or branched alkyl group," "C-C cycloalkyl group," or "C-C linear or branched alkenyl group" in the "C-C linear or branched alkyl group which may have a substituent," "C-C cycloalkyl group which may have a substituent," or "C-C linear or branched alkenyl group which may have a substituent" in the general formulae (2-a) to (2-t) include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl, isopropenyl, and 2-butenyl.

[0035] Specific examples of the "C1 to C6 straight-chain or branched alkyloxy group" or "C5 to C10 cycloalkyloxy group" in the "C1 to C6 straight-chain or branched alkyloxy group which may have a substituent" or "C5 to C10 cycloalkyloxy group which may have a substituent" in the general formulae (2-a) to (2-t) include a methyloxy group, an ethyloxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, an n-hexyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a 1-adamantyloxy group, and a 2-adamantyloxy group.

[0036] Specific examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the general formulae (2-a) to (2-t) include aryloxy groups having 6 to 30 carbon atoms, such as a phenyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthyloxy group, an anthracenyloxy group, and a phenanthrenyloxy group.

[0037] Specific examples of the "aromatic hydrocarbon group," "aromatic heterocyclic group," or "fused polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted fused polycyclic aromatic group" in the general formulae (2-a) to (2-t) are the same as the specific examples given in the general formula (1).

[0038] Specific examples of the "substituent" in the "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," "substituted fused polycyclic aromatic group," "substituted methylene group," "optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms," "optionally substituted cycloalkyl group of 5 to 10 carbon atoms," "optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms," "optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms," or "optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms" in the general formulae (2-a) to (2-t) are the same as the specific examples given in the general formula (1).

[0039] From the viewpoint of heat resistance, it is preferable that R1 and R2 in the above general formulae (2-a) to (2-t) are methyl groups or phenyl groups.

[0040] For ease of synthesis, R3 in the above general formulae (2-a) to (2-t) is preferably hydrogen or a phenyl group.

[0041] In view of ease of synthesis, Ar3 in the above general formulae (2-a) to (2-t) is preferably a substituted or unsubstituted aromatic hydrocarbon group, and a phenyl group is particularly preferred.

[0042] In the general formula (1), Ar2 may have a structure selected from the group consisting of the following general formulae (3-a) to (3-v).

[0043] [ka]

[0044] (In the formula, R4 is the same as R1 to R3 in the general formulae (2-a) to (2-t), The dashed line indicates the binding site. d represents an integer of 0 to 4, e represents an integer of 0 to 3; f represents an integer of 0 to 2.

[0045] Specific examples of the "aromatic hydrocarbon group," "aromatic heterocyclic group," or "fused polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group," "substituted or unsubstituted aromatic heterocyclic group," or "substituted or unsubstituted fused polycyclic aromatic group" in the general formulae (3-a) to (3-v) are the same as the specific examples given in the general formulae (2-a) to (2-t).

[0046] Specific examples of the "C-C linear or branched alkyl group," "C-C cycloalkyl group," or "C-C linear or branched alkenyl group" in the "C-C linear or branched alkyl group which may have a substituent," "C-C cycloalkyl group which may have a substituent," or "C-C linear or branched alkenyl group which may have a substituent" in the "C-C linear or branched alkyl group which may have a substituent," "C-C cycloalkyl group which may have a substituent," or "C-C linear or branched alkenyl group which may have a substituent" in the general formulae (3-a) to (3-v) are the same as the specific examples given in the general formulae (2-a) to (2-t).

[0047] Specific examples of the "C 1 to C 6 linear or branched alkyloxy group" or "C 5 to C 10 cycloalkyloxy group" in the "C 1 to C 6 linear or branched alkyloxy group which may have substituents" or "C 5 to C 10 cycloalkyloxy group which may have substituents" in the general formulae (3-a) to (3-v) are the same as the specific examples given in the general formulae (2-a) to (2-t).

[0048] Specific examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the general formulae (3-a) to (3-v) are the same as the specific examples given in the general formulae (2-a) to (2-t).

[0049] Specific examples of the "substituent" in the "substituted aromatic hydrocarbon group," "substituted aromatic heterocyclic group," "substituted fused polycyclic aromatic group," "substituted methylene group," "optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms," "optionally substituted cycloalkyl group of 5 to 10 carbon atoms," "optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms," "optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms," or "optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms" in the general formulae (3-a) to (3-v) are the same as the specific examples given in the general formulae (2-a) to (2-t).

[0050] From the viewpoint of heat resistance, R4 in the above general formulae (3-a) to (3-v) is preferably a hydrogen atom or a phenyl group.

[0051] From the viewpoint of hole transport properties, Ar1 in general formula (1) is preferably a carbazolyl group, a carbolinyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzoxazolyl group, an indenoindolyl group, a benzofuranocarbazolyl group, or an indenocarbazolyl group, and more preferably a carbazolyl group or a carbolinyl group.

[0052] In view of ease of synthesis, L1 in general formula (1) is preferably benzene, biphenyl, 9,9-spirobi[9H-fluorene], 9,9-dimethylfluorene, 9,9-diphenylfluorene, or triphenylamine, and more preferably benzene or triphenylamine.

[0053] From the viewpoint of the HOMO level, Ar2 in general formula (1) is preferably a pyridyl group, a pyrimidinyl group, a triazinyl group, or a benzonitrile group.

[0054] In view of hole mobility, a in the general formula (1) is preferably an integer of 2 or 3, and b is preferably an integer of 0 or 1.

[0055] The compound represented by general formula (1) can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, or the like, or recrystallization or crystallization using a solvent. The compound can be identified by NMR analysis. As physical property values, it is preferable to measure the glass transition temperature (Tg) and the HOMO level. The glass transition temperature (Tg) is an index of the stability of the thin film state, and the HOMO level is an index of the hole transport property. It is also preferable to evaluate the hole mobility and the light / dark current of a photoelectric conversion element as physical property values.

[0056] The glass transition temperature (Tg) can be determined using a powder with a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS).

[0057] The HOMO level can be determined by forming a 100 nm thin film on an ITO substrate and using an ionization potential measuring device (PYS-202, manufactured by Sumitomo Heavy Industries, Ltd.).

[0058] The hole mobility can be evaluated by forming a film of the organic compound to be measured with a thickness of 3 to 4 μm on an ITO-coated glass substrate and using a transient photocurrent measurement device (Optel, time-of-flight measurement device TOF-401). More specifically, the evaluation can be performed according to the method described in the examples below.

[0059] The light / dark current of the photoelectric conversion element can be evaluated using a spectral sensitivity measurement device (SM-250A, manufactured by Bunkoukeiki Co., Ltd.) In detail, it can be evaluated according to the method described in the examples below.

[0060] The compound represented by general formula (1) can be used to form an organic thin film by known methods such as vapor deposition, spin coating, and inkjet printing. The compound represented by general formula (1) may be used alone to form a film, or multiple types of compounds may be mixed to form a film. Furthermore, the compound may be mixed with other compounds to form a film, provided that the effects of the present invention are not impaired.

[0061] An organic thin film containing a compound represented by general formula (1) is suitable for use in a photoelectric conversion element, particularly an imaging element. The photoelectric conversion element may have, for example, a first electrode (anode), an electron blocking layer, a photoelectric conversion layer, and a second electrode (cathode) in this order, with the electron blocking layer being an organic thin film containing the compound represented by general formula (1). Additional layers can be added to such a multilayer structure, and a configuration can be achieved, for example, with a first electrode, an electron blocking layer, a photoelectric conversion layer, a hole blocking layer, and a second electrode in this order. The organic thin film can also be used in a photoelectric conversion layer.

[0062] <<Photoelectric conversion layer>> The photoelectric conversion layer may be made of either an organic or inorganic material, as long as it can generate signal charges according to the amount of light received. When the photoelectric conversion layer is made of an organic material, the organic semiconductor film may be a single layer or multiple layers. When the photoelectric conversion layer is made of a single layer, a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film of p-type organic semiconductor and n-type organic semiconductor (bulk heterostructure) is used. When the photoelectric conversion layer is made of multiple layers, the structure is a stack of two or more of a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film of p-type organic semiconductor and n-type organic semiconductor, and a buffer layer can be inserted between the layers.

[0063] The p-type semiconductor used in the photoelectric conversion layer is a donor organic semiconductor, which is mainly represented by a hole-transporting organic compound and is a compound that has the property of readily donating electrons. The p-type semiconductor is not particularly limited, and examples thereof include thienoacene-based materials typified by naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, pentacene derivatives, quinacridone derivatives, chrysene derivatives, fluoranthene derivatives, phthalocyanine derivatives, subphthalocyanine derivatives, metal complexes having a heterocyclic compound as a ligand, benzothiophene derivatives, dinaphthothienothiophene derivatives, dianthracenothienothiophene derivatives, benzobisbenzothiophene derivatives, thienobisbenzothiophene derivatives, dibenzothienobisbenzothiophene derivatives, dithienobenzodithiophene derivatives, dibenzothienodithiophene derivatives, benzodithiophene derivatives, naphthodithiophene derivatives, anthracenodithiophene derivatives, tetracenodithiophene derivatives, and pentacenodithiophene derivatives; amine-based derivatives such as triarylamine compounds and carbazole compounds; and indenocarbazole derivatives.

[0064] The n-type organic semiconductor used in the photoelectric conversion layer is an acceptor organic semiconductor, which is mainly represented by an electron-transporting organic compound and refers to an organic compound that has the property of easily accepting electrons. More specifically, when two organic compounds are used in contact with each other, the organic compound with the larger electron affinity is the one that is the acceptor. Therefore, any organic compound that has electron-accepting properties can be used as the acceptor organic compound. For example, fused aromatic carbocyclic compounds (naphthalene, anthracene, fullerene, phenanthrene, tetracene, pyrene, perylene, fluoranthene, or derivatives thereof), 5- to 7-membered heterocyclic compounds containing nitrogen atoms, oxygen atoms, or sulfur atoms (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, Examples of the acceptor organic semiconductor include metal complexes having, as a ligand, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyrazine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and nitrogen-containing heterocyclic compounds. However, the acceptor organic semiconductor is not limited to these, and any organic compound having a larger electron affinity than the organic compound used as the donor organic compound may be used as the acceptor organic semiconductor, as described above.

[0065] The thickness of the photoelectric conversion layer is preferably 100 to 1000 nm, and more preferably 100 to 500 nm.

[0066] <<Conductive thin film>> The conductive thin film is an anode and a cathode, and is made of a conductive material. It may be a transparent conductive thin film. The anode and the cathode may be made of any conductive material commonly used as an electrode, including metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, and mixtures thereof. Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), molybdenum oxide (MoO), and titanium oxide; metal nitrides such as titanium oxynitride (TiNxOx) and titanium nitride (TiN); metals such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), and aluminum (Al); mixtures or laminates of these metals and conductive metal oxides; organic conductive compounds such as polyaniline, polythiophene, and polypyrrole; and laminates of these compounds with ITO.

[0067] <<Hole-blocking layer>> A hole-blocking layer may be inserted between the second electrode (cathode) and the photoelectric conversion layer, and the material used therefor is preferably a material with electron transport ability. For example, organic molecules and organometallic complexes containing nitrogen-containing heterocycles such as pyridine, quinoline, acridine, indole, imidazole, benzimidazole, and phenanthroline are preferred, as are materials with low absorption in the visible light region. Furthermore, when forming a thin film of about 5 to 30 nm, fullerenes and fullerene derivatives that absorb in the visible light region can also be used.

[0068] <Image sensor> The imaging element is configured to include the photoelectric conversion element. [Example]

[0069] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. [Example]

[0070] <Synthesis of 1,3,5-tris(9H-carbazol-9-yl)benzene (Compound 1-1)> A reaction vessel purged with nitrogen gas was charged with 10.0 g of 1,3,5-tribromobenzene, 17.9 g of carbazole, 0.4 g of copper powder, 1.1 g of 1,10-phenanthroline, 1.0 g of sodium sulfite, 13.2 g of potassium carbonate, and 19 mL of dodecylbenzene, and the mixture was stirred at 190 °C for 8 hours. The mixture was allowed to cool to room temperature, and 200 mL of toluene was added. The mixture was stirred at 100 °C for 1 hour, followed by hot filtration and concentration of the filtrate to obtain a crude product. The crude product was recrystallized from toluene to obtain 5.1 g (28% yield) of a white powder of 1,3,5-tris(9H-carbazol-9-yl)benzene (Compound 1-1).

[0071] [ka]

[0072] The structure of the obtained white powder was identified using NMR.

[0073] 1 H-NMR (CDCl3) detected the following 27 hydrogen signals: δ (ppm) = 8.18-8.16 (6H), 7.96 (3H), 7.68-7.66 (6H), 7.49-7.46 (6H), 7.35-7.32 (6H). [Example]

[0074] <Synthesis of tris[3-(carbazol-9-yl)phenyl]amine (Compound 1-14)> A reaction vessel purged with nitrogen gas was charged with 5.5 g of bis[3-(carbazol-9-yl)phenyl]amine, 4.9 g of 9-(3-iodophenyl)carbazole, 2.1 g of t-butoxysodium, 0.1 g of palladium(II) acetate, and 50 mL of toluene. The mixture was heated to 71 °C with stirring, and then 0.4 g of tri(t-butyl)phosphine was added. After stirring at 100 °C for 10 hours, 300 mL of toluene was added, filtered, and the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography to obtain 5.3 g (56% yield) of a white powder of tris[3-(carbazol-9-yl)phenyl]amine (Compound 1-14).

[0075] [ka]

[0076] The structure of the obtained white powder was identified using NMR.

[0077] 1 H-NMR (CDCl3) detected the following 36 hydrogen signals: δ (ppm) = 8.13-8.08 (6H), 7.57-7.47 (6H), 7.39-7.13 (24H). [Example]

[0078] Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 1-18) A reaction vessel was charged with 3.7 g of 2-{3,5-difluoro-phenyl}-4,6-diphenyl-benzoxazole, 3.4 g of carbazole, and 12.9 g of cesium carbonate, and the mixture was heated and stirred overnight at 120°C in DMF solvent. After cooling, HO was added and the precipitated solid was collected to obtain a crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 4.8 g (30% yield) of a white powder of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 1-18).

[0079] [ka]

[0080] The structure of the obtained white powder was identified using NMR.

[0081] 1 H-NMR (CDCl3) detected the following 31 hydrogen signals: δ (ppm) = 8.81 (1H), 8.25 (4H), 8.02 (1H), 7.94 (1H), 7.69 (2H), 7.63 (1H), 7.56 (2H), 7.55 (2H), 7.48-7.29 (17H). [Example]

[0082] Synthesis of 4,6-diphenyl-2-{3,5-bis(9H-carbazol-9-yl)phenyl}pyrimidine (Compound 1-19) A reaction vessel purged with nitrogen gas was charged with 30.0 g of 4,6-diphenyl-2-chloropyrimidine, 56.0 g of 3,5-bis(9H-carbazol-9-yl)phenylboronic acid, 46.6 g of potassium carbonate, 210 mL of toluene, 52.8 mL of ethanol, 168 mL of HO, and 3.9 g of tetrakis(triphenylphosphine)palladium(0), and stirred under reflux. After the raw materials were consumed, the mixture was allowed to cool to room temperature, and 600 mL of methanol was added to precipitate a solid, which was then filtered. Monochlorobenzene was added to the solid, which was then dissolved by heating. After hot filtration, the filtrate was concentrated, acetone was added, and the solid was precipitated again. This was then filtered, yielding a crude product. The crude product was purified by recrystallization twice using monochlorobenzene to obtain 50.0 g (yield 69.6%) of white powder of 4,6-diphenyl-2-{3,5-bis(9H-carbazol-9-yl)phenyl}pyrimidine (compound 1-19).

[0083] [ka]

[0084] The structure of the obtained white powder was identified using NMR.

[0085] 1 H-NMR (CDCl3) detected the following 30 hydrogen signals: δ (ppm) = 9.06-9.05 (2H), 8.28-8.24 (4H), 8.21-8.19 (4H), 8.13 (1H), 7.95-7.94 (1H), 7.65-7.63 (4H), 7.54-7.51 (6H), 7.49-7.45 (4H), 7.36-7.32 (4H). [Example]

[0086] Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-biphenyl-4'-yl}-benzoxazole (Compound 1-24) A reaction vessel was charged with 4.0 g of 2-(4-bromophenyl)benzoxazole and 7.3 g of 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid, 80 mL of toluene, 20 mL of ethanol, and then an aqueous solution of 2.4 g of potassium carbonate dissolved in 20 mL of HO were added, and nitrogen gas was bubbled through the mixture while ultrasonically irradiating for 30 minutes. 0.3 g of tetrakis(triphenylphosphine)palladium(0) was added and the mixture was stirred overnight under reflux. After cooling, the organic layer was separated and concentrated to obtain the crude product. The crude product was purified by crystallization using a toluene / acetone mixed solvent to obtain 4.4 g (50% yield) of a white powder of 2-{(3,5-di([9H]-carbazol-9-yl)-biphenyl-4'-yl}-benzoxazole (Compound 1-24).

[0087] [ka]

[0088] The structure of the obtained white powder was identified using NMR.

[0089] 1H-NMR (CDCl3) detected the following 27 hydrogen signals: δ (ppm) = 8.42 (2H), 8.21 (4H), 8.04 (2H), 7.91 (3H), 7.82 (1H), 7.64 (5H), 7.51 (4H), 7.45-7.32 (6H). [Example]

[0090] Synthesis of 6-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenyl-benzoxazole (Compound 1-25) A reaction vessel was charged with 10.0 g of 6-chloro-2,4-diphenylbenzoxazole, 7.5 g of 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid, 0.5 g of bis(dibenzylideneacetone)palladium(0), 1.1 g of tricyclohexylphosphine, and 12.1 g of tripotassium phosphate. The mixture was refluxed overnight under a 1,4-dioxane / HO mixed solvent. After cooling, the mixture was separated and the aqueous layer was extracted with ethyl acetate and concentrated. The resulting crude product was purified by column chromatography (support: silica gel, eluent: dichloromethane / ethyl acetate) and crystallized from acetone to yield 6.8 g (61% yield) of a white powder of 6-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenylbenzoxazole (Compound 1-25).

[0091] [ka]

[0092] The structure of the obtained white powder was identified using NMR.

[0093] 1 H-NMR (CDCl3) detected the following 31 hydrogen signals: δ (ppm) = 8.35 (2H), 8.21 (4H), 8.11 (2H), 8.07 (2H), 7.91 (2H), 7.88 (1H), 7.66 (4H), 7.59-7.42 (10H), 7.36 (4H). [Example]

[0094] Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (Compound 1-26) In Example 6, 6-chloro-2,4-diphenyl-benzoxazole was replaced with 2-{3,5-dichloro-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole, and 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid was replaced with carbazole, and the reaction was carried out under the same conditions to obtain 7.9 g (yield 57%) of white powder of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (Compound 1-26).

[0095] [ka]

[0096] The structure of the obtained white powder was identified using NMR.

[0097] 1 H-NMR (CDCl3) detected the following 35 hydrogen signals: δ (ppm) = 8.68 (2H), 8.22 (4H), 8.11 (2H), 8.01 (1H), 7.87 (2H), 7.79 (4H), 7.69 (2H), 7.64 (4H), 7.57-7.47 (8H), 7.42 (2H), 7.38 (4H). [Example]

[0098] Synthesis of 4-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (Compound 1-27) In Example 6, 6-chloro-4-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2-phenyl-benzoxazole was used instead of 6-chloro-2,4-diphenyl-benzoxazole, and phenylboronic acid was used instead of 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid, and the reaction was carried out under the same conditions to obtain 8.0 g (yield 60%) of 4-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (Compound 1-27) as a white powder.

[0099] [ka]

[0100] The structure of the obtained white powder was identified using NMR.

[0101] 1 H-NMR (CDCl3) detected the following 31 hydrogen signals: δ (ppm) = 8.52 (2H), 8.42 (2H), 8.21 (4H), 7.91 (1H), 7.90 (1H), 7.87 (1H), 7.85 (4H), 7.71 (2H), 7.65-7.46 (9H), 7.45-7.34 (5H). [Example]

[0102] <Synthesis of 9,9-bis(4-carbazolyl-phenyl)-fluorene (Compound 1-35)> A reaction vessel was charged with 8.9 g of 9,9-bis(4-iodophenyl)-fluorene, 5.5 g of carbazole, 4.8 g of potassium carbonate, 0.5 g of copper powder, and 8 mL of diphenyl ether, and the mixture was heated and stirred at 240 °C for 4 hours. After cooling, 300 mL of toluene was added and the mixture was stirred for 1 hour. Hot filtration was performed, and the filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography to obtain 3.7 g (38% yield) of a white powder of 9,9-bis(4-carbazolyl-phenyl)-fluorene (compound 1-35).

[0103] [ka]

[0104] The structure of the obtained white powder was identified using NMR.

[0105] 1 H-NMR (CDCl3) detected the following 32 hydrogen signals: δ (ppm) = 8.12 (4H), 7.87 (2H), 7.60 (2H), 7.54-7.49 (8H), 7.47-7.41 (4H), 7.43 (4H), 7.38 (4H), 7.26 (4H). [Example]

[0106] Synthesis of 2,7-bis(5H,7H-7,7-dimethylindeno[2,1-b]carbazol-5-yl)-9,9-dimethyl-9H-fluorene (Compound 1-37) A reaction vessel purged with nitrogen gas was charged with 3.0 g of 2,7-dibromo-9,9-dimethyl-9H-fluorene, 5.6 g of 5H,7H-7,7-dimethylindeno[2,1-b]carbazole, 0.15 g of palladium(II) acetate, 2.5 g of sodium t-butoxide, 0.55 g of tri(t-butyl)phosphine, and 100 mL of xylene, and the mixture was heated and refluxed for 6 hours. After the raw materials were consumed, saturated brine and toluene were added, followed by hot filtration and separation of the filtrate. The organic layer was dehydrated with anhydrous magnesium sulfate, filtered, and the filtrate was concentrated to obtain the crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane / chloroform) to obtain 2.5 g (yield 38.5%) of white powder of 2,7-bis(5H,7H-7,7-dimethylindeno[2,1-b]carbazol-5-yl)-9,9-dimethyl-9H-fluorene (compound 1-37).

[0107] [ka]

[0108] The structure of the obtained white powder was identified using NMR.

[0109] 1H-NMR (CDCl3) detected the following 44 hydrogen signals: δ (ppm) = 8.48 (2H), 8.25-8.23 (2H), 8.09-8.07 (2H), 7.89-7.87 (2H), 7.75 (2H), 7.69-7.67 (2H), 7.51-7.49 (4H), 7.46-7.44 (4H), 7.41-7.39 (2H), 7.35-7.33 (2H), 7.32-7.29 (2H), 1.68 (6H), 1.56 (12H). [Example]

[0110] <Synthesis of bis-{4-(benzoxazol-2-yl)phenyl}-{4-(naphthalen-1-yl)phenyl}amine (Compound 1-84)> A reaction vessel was charged with 7.5 g of 4-(naphthalen-1-yl)phenylamine, 20.6 g of 2-(4-bromophenyl)benzoxazole, 9.9 g of sodium t-butoxide, and 150 mL of toluene. The mixture was then sonicated for 30 minutes while nitrogen gas was passed through. 0.9 g of tris(dibenzylideneacetone)dipalladium(0) and 0.4 mL of a 50% (w / v) toluene solution of tri-(t-butyl)phosphine were added and the mixture was heated under reflux and stirred for 3 hours. The reaction vessel was allowed to cool to 80 °C, and the insoluble matter was filtered off. The filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography to obtain 3.4 g (16% yield) of a yellow powder of bis-{4-(benzoxazol-2-yl)phenyl}-{4-(naphthalen-1-yl)phenyl}amine (Compound 1-84).

[0111] [ka]

[0112] The structure of the resulting yellow powder was identified using NMR.

[0113] 1H-NMR (CDCl3) detected the following 27 hydrogen signals: δ (ppm) = 8.26-8.22 (4H), 8.09-8.02 (1H), 7.97-7.89 (2H), 7.83-7.77 (2H), 7.63-7.49 (8H), 7.42-7.32 (10H). [Example]

[0114] Synthesis of 2,6-bis[4-(5H-pyrido[4,3-b]indol-5-yl)phenyl]pyridine (Compound 1-90) A reaction vessel was purged with nitrogen gas and charged with 5.0 g of 5-[4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)phenyl]-5H-pyrido[4,3-b]indole, 1.6 g of 2,6-dibromopyridine, 0.39 g of tetrakis(triphenylphosphine)palladium(0), 16.9 mL of 2 M aqueous potassium carbonate, 56 mL of toluene, and 14 mL of ethanol. The mixture was heated under reflux and stirred for 8.5 hours. After cooling to room temperature, 50 mL of toluene and 100 mL of HO were added. The organic layer was dehydrated over anhydrous magnesium sulfate and then concentrated under reduced pressure to obtain the crude product. The crude product was purified by column chromatography (carrier: NH silica gel, eluent: toluene) to obtain 2.3 g (yield 60%) of white powder of 2,6-bis[4-(5H-pyrido[4,3-b]indol-5-yl)phenyl]pyridine (compound 1-90).

[0115] [ka]

[0116] The structure of the obtained white powder was identified using NMR.

[0117] 1 H-NMR (CDCl3) detected the following 25 hydrogen signals: δ (ppm) = 9.40 (2H), 8.55 (2H), 8.43 (4H), 8.22 (2H), 7.95 (1H), 7.84 (2H), 7.69 (4H), 7.54-7.46 (4H), 7.41-7.34 (4H). [Example]

[0118] Synthesis of 2-{(3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 1-114) A reaction vessel was charged with 3.7 g of 2-{3,4-difluoro-phenyl}-4,6-diphenyl-benzoxazole, 3.4 g of carbazole, and 12.9 g of cesium carbonate, and the mixture was heated and stirred overnight at 120°C in DMF solvent. After cooling, H2O was added and the precipitated solid was collected to obtain a crude product. The crude product was purified by crystallization using a monochlorobenzene / acetone mixed solvent to obtain 3.1 g (60% yield) of a white powder of 2-{(3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (Compound 1-114).

[0119] [ka]

[0120] The structure of the obtained white powder was identified using NMR.

[0121] 1 H-NMR (CDCl3) detected the following 31 hydrogen signals: δ (ppm) = 8.79 (1H), 8.67 (1H), 8.14 (2H), 8.04 (1H), 7.89-7.79 (6H), 7.75 (2H), 7.56 (4H), 7.45 (2H), 7.24 (4H), 7.15-7.06 (8H). [Example]

[0122] The glass transition temperatures of the compounds of Examples 1 to 13 were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). High glass transition temperature compounds EBL-1 (see Patent Document 4) and EBL-2 (see Patent Document 5) with the following structures were also measured using the same method. The measured glass transition temperatures are summarized in Table 1.

[0123] [ka]

[0124] [ka]

[0125] [Table 1]

[0126] The compounds of the present embodiment have a high glass transition temperature of 120°C or higher, indicating that the thin film state is stable. Furthermore, the glass transition temperatures of the compounds of Examples 1 to 13 are higher than that of EBL-2, and by using them instead of EBL-2, it is possible to fabricate elements with better thermal stability. [Example]

[0127] <HOMO level measurement> Using the compounds of Examples 1 to 13 and the comparative compounds EBL-1 and EBL-2, vapor-deposited films with a thickness of 100 nm were prepared on ITO substrates, and the HOMO levels were measured using an ionization potential measurement device (Sumitomo Heavy Industries, Ltd., PYS-202). The results are summarized in Table 2.

[0128] [Table 2]

[0129] The compounds of the present embodiment have a deeper energy level of −5.90 to 6.32 eV than the HOMO levels of the comparative compounds EBL-1 and EBL-2, and can suppress the transfer of charge at the interface with the n-type semiconductor. By using the compounds of Examples 1 to 13 instead of EBL-1 and EBL-2, it is possible to fabricate devices with lower dark current values. [Example]

[0130] <Measurement of hole mobility> Using the compounds of Examples 1 to 13 and the comparative compounds EBL-1 and EBL-2, the organic compounds to be measured were deposited on a glass substrate with an ITO coating by vacuum deposition to a thickness of 3 to 4 μm. Subsequently, an aluminum film was deposited to a thickness of approximately 100 nm to prepare a device for measuring hole mobility. This device was sealed in a nitrogen atmosphere with a glass cap to which a moisture getter sheet for organic EL was attached to prevent deterioration due to adsorption of moisture and oxygen.

[0131] The device was measured using a transient photocurrent measurement device under the following conditions. The obtained measurement values ​​are shown in Table 3. (Measurement conditions) Equipment: Time-of-flight measurement device TOF-401 (Optel) Excitation light source: Nitrogen laser (337.1 nm) Light pulse width: 1nsec or less Measurement area: 0.04cm 2 Sample temperature: 25℃ Load resistance: 50Ω Electric field strength: 0.25MV / cm

[0132] [Table 3]

[0133] The hole mobility of the compound of the embodiment is 1.5E-06 to 4.0E-04 cm 2 The / Vs and hole mobility were observed, and it was found that the compound has hole transport ability. By using an organic thin film containing the compound of the embodiment in a photoelectric conversion element, holes generated in the photoelectric conversion layer can be effectively extracted, and response and conversion efficiency can be improved. [Example]

[0134] <Evaluation of light and dark currents of photoelectric conversion elements> As shown in Figure 1, the photoelectric conversion element was fabricated by vapor-depositing an electron-blocking layer 3, a photoelectric conversion layer 4, and a cathode 5 in this order on a glass substrate 1 on which an ITO electrode was previously formed as a transparent anode 2.

[0135] Specifically, a glass substrate 1 on which an ITO film serving as a transparent anode 2 had been formed was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes, followed by drying for 10 minutes on a hot plate heated to 200°C. This was followed by 15 minutes of UV ozone treatment, after which the ITO-coated glass substrate was placed in a vacuum deposition machine and the pressure was reduced to 0.0001 Pa or less. Subsequently, compound (1-1) of Example 1 was vapor-deposited to a thickness of 15 nm to form an electron-blocking layer 3 covering the transparent anode 2. A photoelectric conversion layer 4 was formed on this electron-blocking layer 3 by binary vapor deposition of a p-type semiconductor (SubPC) having the following structural formula and an n-type semiconductor (C60) having the following structural formula at a vapor deposition rate ratio of SubPC:C60 = 50:50, resulting in a thickness of 200 nm. A gold cathode 5 was formed on this photoelectric conversion layer 4 to a thickness of 100 nm. The measurement results of the fabricated photoelectric conversion device are summarized in Table 4.

[0136] [ka]

[0137] [ka] [Example]

[0138] A photoelectric conversion element was fabricated in the same manner as in Example 17, except that compound (1-14) of Example 2 was used instead of compound (1-1) used as the material for electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4. [Example]

[0139] A photoelectric conversion element was prepared in the same manner as in Example 17, except that compound (1-18) of Example 3 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4. [Example]

[0140] A photoelectric conversion element was prepared in the same manner as in Example 17, except that compound (1-19) of Example 4 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4. [Example]

[0141] A photoelectric conversion element was prepared in the same manner as in Example 17, except that compound (1-35) of Example 9 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4. [Example]

[0142] A photoelectric conversion element was prepared in the same manner as in Example 17, except that compound (1-84) of Example 10 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4.

[0143] [Comparative Example 1] For comparison, a photoelectric conversion element was prepared in the same manner as in Example 17, except that the comparative compound EBL-1 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4.

[0144] Comparative Example 2 For comparison, a photoelectric conversion element was prepared in the same manner as in Example 17, except that the comparative compound EBL-2 was used instead of compound (1-1) used as the material for the electron-blocking layer 3, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4.

[0145] The spectral sensitivities and light currents of the photoelectric conversion elements fabricated in Examples 17 to 22 and Comparative Examples 1 and 2 were measured using a spectral sensitivity measurement device under the following measurement conditions. The irradiance at a specific wavelength during measurement was calibrated using a Si photodiode (S1337-1010BQ, manufactured by Hamamatsu Photonics Co., Ltd.). For the dark current, the spectral irradiance of the photoelectric conversion element was set to zero, and the current value was measured under the same bias conditions. (Measurement conditions) Equipment: Spectral sensitivity measuring device SM-250A (Bunkokeiki Co., Ltd.) Light source: Xenon 150W Spectral irradiance: 50μW / cm 2 (@550nm) Effective irradiation area: 10 x 10 mm Light receiving area: 0.04cm 2 In-plane non-uniformity: within ±5% Source meter: Keithley 2635B (Keithley) Applied bias: 1 to 5 V

[0146] [Table 4]

[0147] As shown in Table 4, the devices of Examples 17 to 22 achieve lower dark currents in the range of 1 to 5 V compared to the devices of the comparative examples, and photoelectric conversion devices compatible with a wide range of driving voltages can be fabricated. In particular, the dark current values ​​at an applied voltage of 5 V were 1.4E-03 A / cm for the devices of Comparative Examples 1 and 2, respectively. 2 , 2.0E-05A / cm 2 In contrast, the elements of Examples 17 to 22 were 8.5E-08 to 9.5E-07 A / cm 2 A low dark current value was achieved. Furthermore, bright current was also observed in the elements of Examples 17 to 22, which indicates that photoelectric conversion elements were successfully fabricated.

[0148] From the above results, it was found that a photoelectric conversion element using the compound represented by general formula (1) of this embodiment as an electron blocking layer can suppress charge transfer from the acceptor organic semiconductor used in the photoelectric conversion layer, thereby significantly reducing the dark current value. It was shown that the compound represented by general formula (1) of this embodiment has the HOMO level, high heat resistance, and sufficient hole mobility required for the electron blocking layer of a photoelectric conversion element.

[0149] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Patent Application No. 2021-12094) filed on January 28, 2021, the entire contents of which are incorporated by reference. All references cited herein are incorporated in their entirety. [Industrial Applicability]

[0150] The organic thin film of the present invention, which has high heat resistance and good charge mobility, can be applied to various photoelectric conversion elements, and therefore can provide a photoelectric conversion element, particularly an image sensor, having good dark current characteristics and conversion efficiency, and an optical sensor using the same. [Explanation of symbols]

[0151] 1. Glass substrate 2 transparent anode 3. Electron Blocking Layer 4 Photoelectric conversion layer 5 cathode

Claims

1. An organic photoelectric conversion element comprising a conductive thin film, an organic photoelectric conversion layer, a blocking layer, and a transparent conductive thin film, wherein the blocking layer contains a blocking material which is a compound containing two or more fused heterocyclic groups consisting of a five-membered heterocycle and has the following properties: (1) A glass transition temperature (Tg) of 110°C or higher; (2) The highest occupied molecular orbital (HOMO) level is −5.8 to −7.0 eV; (3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is 1.0×10 -７ < μh < 1.0 × 10 -２ (cm ２ / Vs).

2. The photoelectric conversion element according to claim 1 , wherein the blocking layer is an electron blocking layer.

3. The photoelectric conversion element according to claim 2 , wherein the blocking layer has a thickness smaller than that of the organic photoelectric conversion layer.

4. 2. The photoelectric conversion element according to claim 1, wherein the blocking material is a compound represented by the following general formula (1): 【Chemistry 1】 (In the formula, Ar １ and Ar ２ may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, L １ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a substituted or unsubstituted triarylamine, a represents an integer of 2 to 4, b represents an integer of 0 to 2.

5. In the general formula (1), Ar １ The photoelectric conversion element according to claim 4, wherein: is a structure selected from the group consisting of the following general formulas (2-a) to (2-t): 【Chemistry 2】 (In the formula, X is S, O, Se, C-R １ R ２ , Si—R １ R ２ , or N-Ar ３ represents Y is S, O, Se, Si-R １ R ２ , or N-Ar ３ represents Z is N or C-R ３ represents R １ ~R ３ are, which may be the same or different, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, an optionally substituted linear or branched alkyl group of 1 to 8 carbon atoms, an optionally substituted cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 8 carbon atoms, an optionally substituted cycloalkyloxy group of 2 to 10 carbon atoms, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group, R １ ~R ３ adjacent groups may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, Ar ３ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted fused polycyclic aromatic group, The dashed line indicates the binding site.)

6. In the general formula (1), L １ is represented by a divalent to pentavalent group optionally having a substituent, such as benzene, biphenyl, ο-terphenyl, m-terphenyl, p-terphenyl, 1,3,5-triphenylbenzene, naphthyl, phenanthrene, triphenylene, furan, thiophene, dibenzofuran, dibenzothiophene, 9,9-spirobi[9H-fluorene], 9,9-dimethylfluorene, 9,9-diphenylfluorene, triphenylamine, 9-phenylcarbazole, pyridine, pyrimidine, 1,3,5-triazine, 2,6-diphenylpyridine, or 2,4,6-triphenylpyrimidine.

7. In the general formula (1), Ar ２ The photoelectric conversion element according to claim 6, wherein: is a structure selected from the group consisting of the following general formulas (3-a) to (3-v): 【Transformation 3】 (In the formula, R ４ represents R in the general formulas (2-a) to (2-t). １ ~R ３ is identical to the definition of The dashed line indicates the binding site. d represents an integer of 0 to 4, e represents an integer of 0 to 3; f represents an integer of 0 to 2.

8. The photoelectric conversion element according to any one of claims 1 to 7, wherein the organic photoelectric conversion layer contains a fullerene or a fullerene derivative as an n-type semiconductor.

9. An imaging device comprising the photoelectric conversion element according to any one of claims 1 to 8.

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