Photoelectric conversion element material, and photoelectric conversion element using same

Abstract

The present invention provides: a material which enables a photoelectric conversion element for image pickup to have higher sensitivity and higher resolution; and a photoelectric conversion element for image pickup using the same.　Specifically, provided are: an image-pickup photoelectric conversion element material comprising a compound represented by general formula (1); and a photoelectric conversion element including said photoelectric conversion element material. L1 represents a C6-18 aromatic hydrocarbon group or the like, ring B represents a 6-membered ring represented by (1B), ring C represents a 5-membered ring represented by (1C), X represents N-Ar6 or the like, and Ar1 to Ar6 represent a C6-18 aromatic hydrocarbon group or the like. However, Ar6 includes one or more structures represented by general formula (2). a to e represent the number of substitutions, a to d represent an integer of 0-4, and e represents an integer of 0-2. Y is N-Ar9 or the like, and Ar7 to Ar11 are a C6-18 aromatic hydrocarbon group or the like. f and g represent the number of substitutions, and represent an integer of 0-4.

Description

Material for photoelectric conversion element and photoelectric conversion element using the same

[0001] The present invention relates to a material for a photoelectric conversion element and a photoelectric conversion element using the same, and particularly to a material for a photoelectric conversion element that is useful for an imaging device.

[0002] In recent years, the development of organic electronics devices using thin films formed from organic semiconductors has progressed. Examples include electroluminescent elements, solar cells, transistor elements, and photoelectric conversion elements. In particular, the development of organic electroluminescent elements, which are electroluminescent elements made of organic materials, has progressed the most. As their application to smartphones, TVs, and the like progresses, development aimed at further increasing their functionality is also ongoing.

[0003] Among these, photoelectric conversion elements for imaging have been developed and commercialized using PN junctions of inorganic semiconductors such as silicon. Studies are being conducted to improve the functionality of digital cameras and smartphone cameras, as well as for applications such as surveillance cameras and automotive sensors. However, challenges to meeting these diverse applications include increasing sensitivity and miniaturizing pixels (higher resolution). Photoelectric conversion elements using inorganic semiconductors typically employ a method of placing color filters corresponding to the three primary colors of light, RGB, on the light-receiving section of the photoelectric conversion element to obtain color images. This method, which places the RGB color filters on a flat surface, poses challenges in terms of the efficiency of incident light utilization and resolution (Non-Patent Documents 1 and 2).

[0004] As one solution to these problems with photoelectric conversion elements, development is underway to use organic semiconductors instead of inorganic semiconductors (Non-Patent Documents 1 and 2). This takes advantage of the property of organic semiconductors, which allows them to selectively absorb only light in a specific wavelength range with high sensitivity, and it has been proposed to solve the problems of high sensitivity and high resolution by stacking photoelectric conversion elements made of organic semiconductors corresponding to the three primary colors of light. In addition, a device has been proposed in which a photoelectric conversion element made of an organic semiconductor and a photoelectric conversion element made of an inorganic semiconductor are stacked (Non-Patent Document 3).

[0005] Here, a photoelectric conversion element using an organic semiconductor is an element configured by having a photoelectric conversion layer made of a thin film of an organic semiconductor between two electrodes, with a hole-blocking layer and / or an electron-blocking layer disposed between the photoelectric conversion layer and the two electrodes as needed. In a photoelectric conversion element, excitons are generated by absorbing light of a desired wavelength in the photoelectric conversion layer, and then holes and electrons are generated by charge separation of the excitons. The holes and electrons then migrate to the respective electrodes, converting light into an electrical signal. To accelerate this process, a bias voltage is typically applied between the two electrodes, but reducing the leakage current from the two electrodes caused by the application of the bias voltage presents a challenge. For these reasons, controlling the movement of holes and electrons within the photoelectric conversion element is key to achieving the desired characteristics of the photoelectric conversion element.

[0006] Organic semiconductors used in each layer of a photoelectric conversion element can be roughly divided into P-type organic semiconductors and N-type organic semiconductors, with P-type organic semiconductors being used as hole transport materials and N-type organic semiconductors being used as electron transport materials. In order to control the movement of holes and electrons in a photoelectric conversion element, various organic semiconductors having appropriate physical properties, such as hole mobility, electron mobility, energy value of the highest occupied molecular orbital (HOMO), and energy value of the lowest unoccupied molecular orbital (LUMO), have been developed, but the current situation is such that they cannot be said to have sufficient properties.

[0007] Furthermore, various compounds have been disclosed that are excellent as hole transport materials or electron blocking materials for organic electroluminescent elements and organic solar cells, but these are not necessarily excellent as hole transport materials or electron blocking materials for imaging. Specifically, one of the important properties required for hole transport materials in photoelectric conversion elements for imaging is, for example, to increase the difference between the current value when the shutter is closed and the current value when the shutter is open (light-to-dark ratio), so that a lower current value in a dark place is preferable, and a higher current value in a bright place is preferable. In other words, a high "light-to-dark ratio" is important. On the other hand, in organic electroluminescent elements, the characteristics to be improved include the voltage required to pass a certain current, luminous efficiency, and device life, and the required properties are significantly different from those of photoelectric conversion elements for imaging. Furthermore, it is important for organic solar cells to generate a large amount of current in both dark and bright places, which differs from the required properties of photoelectric conversion elements for imaging, in which a lower current value in a dark place is preferable. As described above, the hole transport materials and electron blocking materials for organic electroluminescent devices and organic solar cells differ in the properties required for the hole transport materials and electron blocking materials for image-capturing photoelectric conversion elements. Therefore, it is unclear until confirmation by experiment whether a material that is excellent as a hole transport material and electron blocking material for organic electroluminescent devices and organic solar cells is also excellent as a hole transport material and electron blocking material for image-capturing photoelectric conversion elements.

[0008] Patent Document 1 proposes a device that uses quinacridone as a P-type organic semiconductor in a photoelectric conversion layer, subphthalocyanine chloride as an N-type organic semiconductor, and an indolocarbazole derivative in a first buffer layer disposed between the photoelectric conversion layer and an electrode.

[0009] Patent Document 2 proposes a photoelectric conversion element that uses a carbazole derivative in an electron blocking layer disposed between a photoelectric conversion layer and an electrode.

[0010] Patent Documents 3 and 4 propose photoelectric conversion elements that use an indolocarbazole derivative in an electron blocking layer disposed between a photoelectric conversion layer and an electrode.

[0011] Patent Documents 5 and 6 propose organic EL devices using indolocarbazole derivatives as light-emitting layer materials.

[0012] JP 2018-85427 A JP 2011-228614 A WO2022114065 WO2022114067 US20170271598 WO2011099374

[0013] NHK Giken R&D No.132, pp.4-11 (2012.3) NHK Giken R&D No.174, pp.4-17 (2019.3) 2019 IEEE International Electron Devices Meeting (IEDM), pp.16.6.1-16.6.4 (2019)

[0014] In order to advance the application of imaging photoelectric conversion elements to digital cameras, smartphone cameras, surveillance cameras, automotive sensors, and the like, organic conversion is key to achieving even higher sensitivity and resolution. To increase the contrast of images, materials that exhibit a high contrast ratio, having both a low dark current value and a high bright current value, are required. In light of this current situation, the present invention aims to provide a material that achieves high sensitivity and resolution in imaging photoelectric conversion elements, and an imaging photoelectric conversion element using the same.

[0015] As a result of extensive research, the present inventors have found that by using the compound of the present invention, it is possible to control the behavior of holes and electrons in a photoelectric conversion element, thereby realizing a photoelectric conversion element that exhibits a high brightness / dark ratio, and have thus completed the present invention.

[0016] The present invention provides a material for a photoelectric conversion device, comprising a compound represented by the following general formula (1): In general formula (1), L １ represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 6 of these aromatic groups. Ring B is fused with an adjacent ring at any position and represents a 6-membered ring represented by formula (1B). Ring C is fused with an adjacent ring at any position and represents a 5-membered ring represented by formula (1C). X is O, S, N-Ar ６ It is expressed as: Ar１ ~Ar ６ each independently represents deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 10 of these aromatic groups, provided that X is N-Ar ６ When represented by ６ contains one or more structures represented by the following general formula (2): a to e represent the number of substitutions, a to d each independently represent an integer of 0 to 4, and e represents an integer of 0 to 2. In the general formula (2), each Y is independently N-Ar ９ , O, S, C-Ar １０ Ar １１ Ar is represented by either ７ ~Ar １１ each independently represents deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 5 of these aromatic groups. f and g represent the number of substitutions, and each independently represents an integer of 0 to 4. ６ When the general formula (2) is included, the one bonded to N in the general formula (1) is Ar ７ ~Ar １１ The N in the general formula (1) may be directly bonded to the fused ring represented by the formula (2). ６ where Ar ６ refers to N bonded to

[0017] The material for a photoelectric conversion device represented by the general formula (1) is preferably a material for a photoelectric conversion device for imaging, and the photoelectric conversion device is preferably a photoelectric conversion device for imaging.

[0018] The photoelectric conversion element material represented by the general formula (1) preferably has a highest occupied molecular orbital (HOMO) energy level of −4.3 eV or less, and a lowest unoccupied molecular orbital (LUMO) energy level of −2.5 eV or more, as obtained by a structural optimization calculation using density functional theory calculation B3LYP / 6-31G(d).

[0019] The material for a photoelectric conversion element for imaging represented by the general formula (1) is 1×10 －６ cm ２ It is preferable that the material for a photoelectric conversion element for imaging represented by the general formula (1) is amorphous.

[0020] The material for a photoelectric conversion element for imaging represented by the general formula (1) can be used as a hole transport material.

[0021] The present invention also relates to an imaging photoelectric conversion element having a photoelectric conversion layer and an electron blocking layer between two electrodes, wherein at least one of the photoelectric conversion layer and the electron blocking layer contains a material for an imaging photoelectric conversion element represented by general formula (1).

[0022] The photoelectric conversion element of the present invention can contain the material for a photoelectric conversion element for imaging represented by the general formula (1) in the electron blocking layer, and can contain an electron transporting material such as a fullerene derivative in the photoelectric conversion layer.

[0023] The photoelectric conversion element of the present invention uses the material for a photoelectric conversion element for imaging represented by general formula (1), which allows for appropriate movement of holes and electrons within the photoelectric conversion element for imaging, thereby making it possible to reduce the leakage current that occurs when a bias voltage is applied during the conversion of light into electrical energy, and as a result, it is believed that a photoelectric conversion element that achieves a low dark current value and a high light-to-dark ratio can be obtained. Therefore, the material of the present invention is useful as a material for a photoelectric conversion element in a photoelectric conversion film stack-type imaging device.

[0024] 1 is a cross-sectional view showing a structural example of a photoelectric conversion element used in the present invention.

[0025] The imaging photoelectric conversion element of the present invention is a photoelectric conversion element that has at least one organic layer between two electrodes and converts light into electrical energy. The organic layer contains a material for an imaging photoelectric conversion element comprising a compound represented by the following general formula (1). More specifically, in an imaging photoelectric conversion element having a photoelectric conversion layer and an electron blocking layer between two electrodes, at least one of the photoelectric conversion layer and the electron blocking layer contains a material for a photoelectric conversion element represented by the following general formula (1). Hereinafter, the material for an imaging photoelectric conversion element comprising a compound represented by general formula (1) will simply be referred to as a material for a photoelectric conversion element. It may also be referred to as the material of the present invention or the compound represented by general formula (1).

[0026] The compound represented by the general formula (1) will be explained below.

[0027] In the general formula (1), L １ represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 6 of these aromatic groups, but is preferably a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, or a substituted or unsubstituted terphenyl group, and more preferably a substituted or unsubstituted phenyl group or a substituted or unsubstituted biphenyl group. The substituted or unsubstituted terphenyl group may be linear or branched. Ring B is fused to an adjacent ring at any position and represents a 6-membered ring represented by formula (1B). Ring C is fused to an adjacent ring at any position and represents a 5-membered ring represented by formula (1C). X is O, S, N-Ar ６ Although N-Ar ６ a to e represent the number of substitutions, a to d each independently represent an integer of 0 to 4, and e represents an integer of 0 to 2, but it is preferable that all of them are 0. However, Ar ６ contains one or more structures represented by the following general formula (2).

[0028] In the general formula (2), each Y is independently N-Ar ９ , O, S, C-Ar １０ Ar １１Although N-Ar ９ , O, or S. f and g represent the number of substitutions, and each independently represents an integer of 0 to 4, but both are preferably 0.

[0029] Ar １ ~Ar ６ each independently represents deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 10 of these aromatic groups; however, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms is preferred, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms is more preferred, and a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 6 to 12 carbon atoms is even more preferred. ７ ~Ar １１ each independently represents deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 5 of these aromatic groups; however, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms is preferred, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms is more preferred, and a substituted or unsubstituted aromatic hydrocarbon group having 6 to 13 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 6 to 12 carbon atoms is even more preferred. １ ~Ar ６ When Ar represents the above-mentioned linking aromatic group, the number of links is preferably 2 to 6, more preferably 2 to 4. ７ ~Ar １１When Ar represents the above-mentioned linking aromatic group, the number of links is preferably 2 to 4, more preferably 2 to 3. ３ , Ar ４ , Ar ６ ~Ar １１ When Ar is the above-mentioned aromatic heterocyclic group or the above-mentioned linking aromatic group containing an aromatic heterocyclic group, it is preferable that it does not contain a nitrogen-containing six-membered ring, and quinoline, isoquinoline, quinazoline, quinoxaline, benzimidazole, aza-triphenylene, phenanthroline, aza-pyrene, aza-anthracene, aza-fluorene, aza-dibenzofuran, aza-dibenzothiophene, aza-dibenzoselenophene, or aza-carbazole. Specific examples of the nitrogen-containing six-membered ring include pyridine, pyrimidine, pyrazine, pyridazine, triazine, and tetrazine. １ ~Ar １１ When is a group having a hydrogen atom, the hydrogen atom may be substituted with deuterium or halogen.

[0030] The general formula (1) is represented by the following formulas (3) to (8), and the compound is preferably represented by any one of these formulas.

[0031] Ar １ ~Ar １１ When is a halogen, specific examples include a fluoro group, a chloro group, a bromo group, and an iodo group.

[0032] Ar １ ~Ar １１ is an alkyl group having 1 to 20 carbon atoms, it may be any of a linear, branched, or cyclic alkyl group, and is preferably a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. Specific examples thereof include linear saturated hydrocarbon groups such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-dodecyl group, an n-tetradecyl group, or an n-octadecyl group; branched saturated hydrocarbon groups such as an isopropyl group, an isobutyl group, a neopentyl group, a 2-ethylhexyl group, or a 2-hexyloctyl group; and saturated alicyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, or a 4-butylcyclohexyl group.

[0033] Ar １ ~Ar １１ is an unsubstituted aromatic amino group having 12 to 36 carbon atoms, specific examples of the aryl group of the aromatic amino group include groups in which one hydrogen atom has been removed from a phenyl group, a biphenyl group, a terphenyl group, a quaterphenyl group, a naphthyl group, a phenanthrenyl group, an anthracenyl group, a triphenylenyl group, a pyrenyl group, a fluorenyl group, a spirobifluorenyl group, etc., and preferred are a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a phenanthrenyl group, a fluorenyl group, or a triphenylenyl group. Specific examples of the heteroaryl group of the aromatic amino group include pyrrole, pyrrolopyrrole, indole, pyrroloindole, benzoindole, naphthopyrrole, isoindole, pyrroloisoindole, benzisoindole, naphthoisopyrrole, carbazole, benzocarbazole, indoloindole, carbazolocarbazole, benzofurocarbazole, benzothienocarbazole, carboline, thiophene, benzothiophene, naphthothiophene, dibenzothiophene, benzothienonaphthalene, benzothienobenzothiophene, and benzothienodibenzothienyl. Examples of the alkyl group include groups in which one hydrogen atom has been removed from thiophene, dinaphthothiophene, dinaphthothienothiophene, naphthobenzothiophene, furan, benzofuran, naphthofuran, dibenzofuran, benzofuronaphthalene, benzofurobenzofuran, benzofurodibenzofuran, dinaphthofuran, dinaphthofuranofuran, naphthobenzofuran, pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, quinoxaline, and the like, and preferably dibenzofuran, dibenzothiophene, carbazole, benzofurocarbazole, or benzothienocarbazole.

[0034] Ar １ ~Ar １１ When Ar is an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, examples of the group include a group in which one hydrogen atom has been removed from a known aromatic hydrocarbon. ６ The general formula (2) is included in the formula (1), and the N bonded to the general formula (1) is Ar ７ ~Ar １１In the case of (I), examples thereof include groups in which two hydrogen atoms have been removed from a known aromatic hydrocarbon group. Specific examples include monocyclic aromatic hydrocarbons such as benzene, bicyclic aromatic hydrocarbons such as naphthalene, tricyclic aromatic hydrocarbons such as indacene, biphenylene, phenalene, anthracene, phenanthrene, and fluorene, and tetracyclic aromatic hydrocarbons such as fluoranthene, acephenanthrylene, aceanthrylene, triphenylene, pyrene, chrysene, tetraphene, tetracene, and pleiadene. Benzene, naphthalene, anthracene, triphenylene, and pyrene are preferred.

[0035] Ar １ ~Ar １１ When Ar is an unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, examples thereof include a group in which one hydrogen atom has been removed from an aromatic heterocyclic group. ６ The general formula (2) is included in the formula (1), and the N bonded to the general formula (1) is Ar ７ ~Ar １１In the case where the aromatic heterocyclic group is a benzothienone, examples of the aromatic heterocyclic group include a group in which two hydrogen atoms have been removed from a known aromatic heterocyclic group. Specific examples include nitrogen-containing aromatic compounds having a pyrrole ring such as pyrrole, pyrrolopyrrole, indole, pyrroloindole, benzoindole, naphthopyrrole, isoindole, pyrroloisoindole, benzisoindole, naphthoisopyrrole, carbazole, benzocarbazole, indoloindole, carbazolocarbazole, indolocarbazole, or carboline; thiophene, benzothiophene, naphthothiophene, dibenzothiophene, benzothienonaphthalene, benzothienobenzothiophene, benzothienodibenzothiophene, dinaphthothiophene; Examples of the aromatic compound include sulfur-containing aromatic compounds having a thiophene ring such as dinaphthothienothiophene, naphthobenzothiophene, or benzothienocarbazole, oxygen-containing aromatic compounds having a furan ring such as furan, benzofuran, naphthofuran, dibenzofuran, benzofuronaphthalene, benzofurobenzofuran, benzofurodibenzofuran, dinaphthofuran, dinaphthofuranofuran, naphthobenzofuran, or benzofurocarbazole, and nitrogen-containing aromatic compounds such as pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, and quinoxaline. Preferably, dibenzofuran, dibenzothiophene, or carbazole is used. However, Ar ３ , Ar ４ , Ar ６ ~Ar １１ is the above-mentioned aromatic heterocyclic group and the above-mentioned linking aromatic group containing an aromatic heterocyclic group, it is preferable that it does not contain a nitrogen-containing six-membered ring, and quinoline, isoquinoline, quinazoline, quinoxaline, benzimidazole, aza-triphenylene, phenanthroline, aza-pyrene, aza-anthracene, aza-fluorene, aza-dibenzofuran, aza-dibenzothiophene, aza-dibenzoselenophene, aza-carbazole. Specific examples of the nitrogen-containing six-membered ring include pyridine, pyrimidine, pyrazine, pyridazine, triazine, and tetrazine.

[0036] In this specification, a linking aromatic group refers to an aromatic group in which the aromatic rings of two or more aromatic groups are linked by a single bond. These linking aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para, but is preferably para- or meta-linked. The aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and the multiple aromatic groups may be the same or different. Note that the aromatic groups constituting the linking aromatic group do not include aromatic amino groups.

[0037] Ar １ ~Ar １１ When Ar is an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linking aromatic group, it may have a substituent, and examples of the substituent include deuterium, halogen, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, a nitro group, and an alkylsilyl group having 3 to 12 carbon atoms. １ ~Ar １１ When the aromatic group is an aromatic amino group, the aromatic group may have a substituent, and the substituent in this case is the same as when the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group has a substituent.

[0038] The alkyl group having 1 to 20 carbon atoms as the substituent may be any of a linear, branched, or cyclic alkyl group, and is preferably a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. Specific examples thereof include linear saturated hydrocarbon groups such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-dodecyl group, an n-tetradecyl group, or an n-octadecyl group; branched saturated hydrocarbon groups such as an isopropyl group, an isobutyl group, a neopentyl group, a 2-ethylhexyl group, or a 2-hexyloctyl group; and saturated alicyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a 4-butylcyclohexyl group, or a 4-dodecylcyclohexyl group.

[0039] Specific examples of the halogen substituent include a fluoro group, a chloro group, a bromo group, and an iodo group. Specific examples of the aralkyl group having 7 to 38 carbon atoms include a benzyl group, a phenethyl group, a phenylpropyl group, a phenylbutyl group, a naphthylmethyl group, and a triphenylenylmethyl group. Specific examples of the alkenyl group having 2 to 20 carbon atoms as the substituent include an ethylene group, a propylene group, a butylene group, a pentene group, a cyclopentene group, a hexene group, a cyclohexene group, and an octene group. Specific examples of the alkynyl group having 2 to 20 carbon atoms as the substituent include an acetylene group, a propyne group, a butyne group, and a pentyne group. Specific examples of the acyl group having 2 to 20 carbon atoms as the substituent include a formyl group, an acetyl group, a propionyl group, and a benzoyl group. Specific examples of the alkoxy group having 1 to 20 carbon atoms as the substituent include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Specific examples of the alkoxycarbonyl group having 2 to 20 carbon atoms as the substituent include a methyl ester group, an ethyl ester group, etc. Specific examples of the alkylsilyl group having 3 to 12 carbon atoms as the substituent include a trimethylsilyl group, a triethylsilyl group, a tripropylsilyl group, etc.

[0040] Preferred specific examples of the compound represented by general formula (1) that is the material for a photoelectric conversion element of the present invention are shown below, but the invention is not limited thereto. In the following formulas, D represents deuterium, and the numbers represent the number of deuterium substitutions.

[0041]

[0042] The compound represented by general formula (1) of the present invention can be obtained by synthesis using various organic synthesis reaction methods established in the field of organic synthetic chemistry, including coupling reactions such as Suzuki coupling, Stille coupling, Grignard coupling, Ullmann coupling, Buchwald-Hartwig reaction, and Heck reaction, using commercially available reagents as raw materials, followed by purification using known methods such as recrystallization, column chromatography, and sublimation purification, but is not limited to these methods.

[0043] The material for photoelectric conversion devices of the present invention preferably has an energy level of the highest occupied molecular orbital (HOMO) obtained by a structure optimization calculation using density functional theory calculation B3LYP / 6-31G(d) of −4.3 eV or less, more preferably in the range of −5.5 eV to −4.5 eV, and even more preferably in the range of −5.2 eV to −4.8 eV.

[0044] The material for photoelectric conversion elements of the present invention preferably has an energy level of the lowest unoccupied molecular orbital (LUMO) obtained by a structural optimization calculation using density functional theory calculation B3LYP / 6-31G(d) of −2.5 eV or higher, more preferably in the range of −2.0 eV to −0.5 eV, and even more preferably in the range of −1.5 eV to −0.8 eV.

[0045] In the material for photoelectric conversion elements of the present invention, the difference (absolute value) between the HOMO energy level and the LUMO energy level is preferably in the range of 2.0 eV to 5.0 eV, more preferably 2.5 eV to 4.7 eV, and even more preferably 3.5 eV to 4.5 eV.

[0046] The material for a photoelectric conversion element of the present invention has a viscosity of 1×10 －６ cm ２ / Vs or more, and －４ cm ２ / Vs ~ 1 × 10 －１ cm ２ / Vs, and more preferably 2.2×10 －４ cm ２ / Vs~1×10 －２ cm ２It is more preferable that the material has a hole mobility of 1 / Vs / Vs. The hole mobility can be evaluated by known methods such as a method using a FET transistor element, a time-of-flight method, or an SCLC method.

[0047] The material for a photoelectric conversion element of the present invention is preferably amorphous. The amorphous nature of the material can be confirmed by various methods, for example, by detecting no peaks in an XRD method or no endothermic peaks in a DSC method.

[0048] Next, an imaging photoelectric conversion element using the photoelectric conversion element material of the present invention will be described, but the structure of the imaging photoelectric conversion element of the present invention is not limited thereto. The description will be made with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an example structure of an imaging photoelectric conversion element of the present invention, in which 1 represents an electrode, 2 represents a hole blocking layer, 3 represents a photoelectric conversion layer, 4 represents an electron blocking layer, 5 represents an electrode, and 6 represents a substrate. Note that the configuration excluding the substrate may be reversed from that of FIG. 1 , i.e., 1 represents a substrate, 2 represents an electrode, 3 represents an electron blocking layer, 4 represents a photoelectric conversion layer, 5 represents a hole blocking layer, and 6 represents an electrode. The structure of FIG. 1 is not limited thereto, and layers can be added or omitted as necessary.

[0049] - Electrode - The electrode used in an imaging photoelectric conversion element using the imaging photoelectric conversion element material of the present invention has the function of collecting holes and electrons generated in the photoelectric conversion layer. It also needs to have the function of allowing light to enter the photoelectric conversion layer. Therefore, it is desirable that at least one of the two electrodes is transparent or semi-transparent. In addition, the material used as the electrode is not particularly limited as long as it is conductive, but examples thereof include ITO, IZO, SnO ２ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO ２ Examples of the conductive material include transparent conductive materials such as fluorine-containing tetrahydrofuran (FTO), metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel, and tungsten, inorganic conductive materials such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. A mixture of these materials may be used as needed. Two or more layers may also be laminated.

[0050] Photoelectric Conversion Layer: The photoelectric conversion layer is a layer in which holes and electrons are generated by charge separation of excitons generated by incident light. It may be formed of a single photoelectric conversion material, or may be formed in combination with a P-type organic semiconductor material, which is a hole-transporting material, or an N-type organic semiconductor material, which is an electron-transporting material. Two or more P-type organic semiconductors may be used, or two or more N-type organic semiconductors may be used. It is desirable that one or more of these P-type organic semiconductors and / or N-type semiconductors be a dye material that has the function of absorbing light of a desired wavelength in the visible range. The compound represented by general formula (1) of the present invention can be used as the P-type organic semiconductor material, which is a hole-transporting material.

[0051] The P-type organic semiconductor material may be any material having hole transport properties, and is preferably a material represented by general formula (1), but other P-type organic semiconductor materials may also be used. Two or more materials represented by general formula (1) may also be mixed and used. Furthermore, a compound represented by general formula (1) may also be mixed and used with other P-type organic semiconductor materials.

[0052] The other P-type organic semiconductor material may be any material having hole transport properties, and examples thereof include compounds having a condensed polycyclic aromatic group such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene; compounds having a π-excess aromatic group such as cyclopentadiene derivatives, furan derivatives, thiophene derivatives, pyrrole derivatives, benzofuran derivatives, benzothiophene derivatives, dinaphthothienothiophene derivatives, indole derivatives, pyrazoline derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, and indolocarbazole; aromatic amine derivatives, styrylamine derivatives, benzidine derivatives, porphyrin derivatives, phthalocyanine derivatives, and quinacridone derivatives.

[0053] Furthermore, a polymer-type P-type organic semiconductor material may be used as the other P-type organic semiconductor material. Specific examples include polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinyl carbazole derivatives, and polythiophene derivatives. Furthermore, a compound represented by general formula (1) may be used in combination with two or more compounds selected from the P-type organic semiconductor materials and the polymer-type P-type organic semiconductor materials.

[0054] The N-type organic semiconductor material may be any material having electron transport properties, and examples thereof include naphthalene tetracarboxylic acid diimide, perylene tetracarboxylic acid diimide, fullerenes, and azole derivatives such as imidazole, thiazole, thiadiazole, oxazole, oxadiazole, and triazole. Two or more N-type organic semiconductor materials may be mixed and used.

[0055] -Electron Blocking Layer- The electron blocking layer is provided to suppress dark current generated by electron injection from one electrode into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. The electron blocking layer also functions as a hole transport layer, transporting holes generated by charge separation in the photoelectric conversion layer to the electrode. A single layer or multiple layers may be arranged as needed. The electron blocking layer may be formed using a P-type organic semiconductor material, which is a hole transport material. The P-type organic semiconductor material may be any material having hole transport properties. While a compound represented by general formula (1) is preferably used, other P-type organic semiconductor materials may also be used. Furthermore, a mixture of the compound represented by general formula (1) and other P-type organic semiconductor materials may also be used. The other P-type organic semiconductor material may be any material having hole transport properties. Specific examples of the other P-type organic semiconductor material include the compounds exemplified as other P-type organic semiconductor materials in the photoelectric conversion layer section.

[0056] Furthermore, a polymer-type P-type organic semiconductor material may be used as the other P-type organic semiconductor material. Specific examples thereof include the compounds exemplified as the polymer-type P-type organic semiconductor material in the photoelectric conversion layer. Furthermore, a mixture of two or more selected from the compound represented by general formula (1) of the present invention, the P-type organic semiconductor material, and the polymer-type P-type organic semiconductor material may be used.

[0057] -Hole Blocking Layer- The hole blocking layer is provided to suppress dark current generated by holes being injected from one electrode into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. It also functions as an electron transport layer, transporting electrons generated by charge separation in the photoelectric conversion layer to the electrode, and a single layer or multiple layers may be disposed as needed. An N-type organic semiconductor having electron transport properties may be used for the hole blocking layer. The N-type organic semiconductor material may be any material having electron transport properties, and examples thereof include polycyclic aromatic polycarboxylic acid anhydrides and imidized products thereof, such as naphthalene tetracarboxylic acid diimide and perylene tetracarboxylic acid diimide, fullerenes such as C60 and C70, azole derivatives such as imidazole, thiazole, thiadiazole, oxazole, oxadiazole, and triazole, tris(8-quinolinolato)aluminum(III) derivatives, phosphine oxide derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide, fluorenylidenemethane derivatives, anthraquinodimethane derivatives, anthrone derivatives, bipyridine derivatives, quinoline derivatives, and indolocarbazole derivatives. Two or more of these N-type organic semiconductor materials may also be used in combination.

[0058] The hydrogen in the material for a photoelectric conversion element of the present invention may be deuterium. That is, in addition to the hydrogen on the aromatic ring in general formula (1), some or all of the hydrogen in the substituent may be deuterium. Furthermore, some or all of the hydrogen in the compounds used as the N-type organic semiconductor material and the P-type organic semiconductor material may be deuterium.

[0059] When producing the imaging photoelectric conversion element of the present invention, the method for forming each layer is not particularly limited, and the layer may be produced by either a dry process or a wet process. The organic layer containing the material for a photoelectric conversion element of the present invention may be a multi-layer layer, if necessary.

[0060] The photoelectric conversion element for imaging of the present application has a current value of 5.0×10 in a dark place under the measurement conditions described in Example 1 of the present application. －１０ A / cm ２ It is preferably equal to or less than 1.0 × 10 －１２ A / cm ２ ~5.0 x 10 －１０ A / cm ２ , more preferably 1.0 × 10 －１２ A / cm ２ ~4.5 x 10 －１０ A / cm ２ In addition, the photoelectric conversion element for imaging of the present application has a light-to-dark ratio of 6.0×10 under the measurement conditions described in Example 1 of the present application. ２ It is preferably equal to or greater than 6.5×10 ２ More preferably, 7.0 × 10 ２ That's all.

[0061] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] Calculation Example: Calculation of HOMO and LUMO The HOMO and LUMO energy levels of the above compounds A06, A28, A133, B01, B95, C07, C144, and E101, as well as the energy difference between the HOMO and LUMO, were calculated. The calculations were performed using density functional theory (DFT), a Gaussian calculation program, and structural optimization calculations using density functional calculation B3LYP / 6-31G(d). The results are shown in Table 1. It can be said that all of the materials for photoelectric conversion elements for imaging of the present invention have preferable HOMO and LUMO values.

[0063] The HOMO and LUMO energy levels and the HOMO-LUMO energy difference of the comparative compounds H1, H2, H3, and H4 were calculated in the same manner as for the above compounds. The results are shown in Table 1.

[0064]

[0065] The synthesis of compound A06 is shown below as a representative example. Other compounds were also synthesized in a similar manner.

[0066] Synthesis Example 1 (Synthesis of Intermediate R3) R1 (19.5 mmol), R2 (19.5 mmol), copper iodide (2 mmol), and potassium carbonate (39.0 mmol) were placed in a degassed, nitrogen-purged 500 ml three-neck flask. 50 ml of dehydrated dioxane was added and the mixture was stirred at 120°C for 6 hours. After cooling to room temperature, the inorganic matter was removed by filtration. 300 ml of water and 300 ml of dichloromethane were added to the filtrate, which was then transferred to a separatory funnel and fractionated into an organic layer and an aqueous layer. The organic layer was washed three times with 200 ml of water. The resulting organic layer was dehydrated over magnesium sulfate and then concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain R3 (a pale yellow solid). The yield was 5.3 g, or 54.6%.

[0067] Synthesis Example 2 (Synthesis of Compound A06) R3 (10.0 mmol), R4 (12.1 mmol), copper iodide (1.0 mmol), and potassium carbonate (20.1 mmol) synthesized in Synthesis Example 1 were placed in a degassed, nitrogen-purged 500 ml three-neck flask. 50 ml of dimethylimidazolidinone was added, followed by stirring at 180°C for 8 hours. After cooling to room temperature, inorganic materials were removed by filtration. 200 ml of water and 200 ml of dichloromethane were added to the filtrate, which was then transferred to a separatory funnel and fractionated into an organic layer and an aqueous layer. The organic layer was washed three times with 200 ml of water. The resulting organic layer was dehydrated over magnesium sulfate and then concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain A06 (a pale yellow solid). The yield was 6.0 g, or 80.8%. The resulting solid was evaluated by XRD; no peaks were detected, indicating that this compound was amorphous. (APCI-TOFMS, m / z = 739 [M+H] + )

[0068] Property Evaluation Example: On a glass substrate on which a transparent electrode made of ITO with a thickness of 110 nm was formed, Compound A06 was formed as an organic layer by a vacuum deposition method under conditions of a thickness of about 3 μm. Then, using a device on which aluminum (Al) was formed with a thickness of 70 nm as an electrode, charge mobility was measured by a time-of-flight method. As a result, the hole mobility was 1.5×10 －４ cm ２ / Vs.

[0069] The hole mobility was evaluated in the same manner as above, except that compound A06 was replaced with compound A28, A133, B01, B95, C07, C144, E101, H1, H2, H3, and H4. The results are shown in Table 2.

[0070]

[0071] Example 1 A vacuum chamber was placed on an electrode made of ITO with a thickness of 70 nm formed on a glass substrate. －５Compound A06 was deposited as an electron blocking layer to a thickness of 10 nm at 100 Pa. Next, 2Ph-BTBT, F6-SubPc-OC6F5, and fullerene (C60) were co-deposited at a deposition rate ratio of 4:4:2 to form a 200 nm thick photoelectric conversion layer. Subsequently, dpy-NDI was deposited to a thickness of 10 nm to form a hole blocking layer. Finally, aluminum was deposited as an electrode to a thickness of 70 nm to prepare a photoelectric conversion element. When a voltage of 2.6 V was applied using ITO and aluminum as electrodes, the current in the dark (dark current) was 3.3 × 10 －１０ A / cm ２ When a voltage of 2.6 V was applied and the ITO electrode side was irradiated with light from an LED adjusted to 1.6 μW with a wavelength of 500 nm from a height of 10 cm, the current (light current) was 2.9 × 10 －７ A / cm ２ That is, the light-dark ratio when a voltage of 2.6 V was applied was 8.8 × 10 ２ These results are shown in Table 3.

[0072] Examples 2 to 9 Photoelectric conversion elements were prepared in the same manner as in Example 1, except that the compounds shown in Table 3 were used for the electron blocking layer.

[0073] Comparative Examples 1 to 3 Photoelectric conversion elements were fabricated in the same manner as in Example 1, except that the compounds shown in Table 3 were used for the electron blocking layer. The results of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 3.

[0074] The compounds used in the examples and comparative examples are listed below.

[0075]

[0076] By using the material for a photoelectric conversion element for imaging represented by the general formula (1) of the present invention, it is possible to realize appropriate movement of holes and electrons within the photoelectric conversion element for imaging, thereby making it possible to reduce the leakage current that occurs due to the application of a bias voltage when converting light into electrical energy, and as a result, it is thought that a photoelectric conversion element of the present invention that realizes a low dark current value and a high light-to-dark ratio can be obtained. Therefore, the material represented by the general formula (1) of the present invention is useful as a material for a photoelectric conversion element of a photoelectric conversion film stack type imaging device.

[0077] REFERENCE SIGNS LIST 1 Electrode 2 Hole blocking layer 3 Photoelectric conversion layer 4 Electron blocking layer 5 Electrode 6 Substrate

Claims

1. A photoelectric conversion element comprising a material for a photoelectric conversion element, characterized in that the material comprises a compound represented by the following general formula (1): In the general formula (1), L １ represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 6 of these aromatic groups. Ring B is fused with an adjacent ring at any position and represents a 6-membered ring represented by formula (1B). Ring C is fused with an adjacent ring at any position and represents a 5-membered ring represented by formula (1C). X is O, S, N-Ar ６ Represented by: Ar １ ~Ar ６ each independently represents deuterium, a halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 10 of these aromatic groups, provided that X is N-Ar ６ When represented by the formula: ６ contains one or more structures represented by the following general formula (2): a to e represent the number of substitutions, a to d each independently represent an integer of 0 to 4, and e represents an integer of 0 to 2. In the general formula (2), each Y is independently N-Ar ９ , O, S, C-Ar １０ Ar １１ Ar is represented by any one of the following: ７ ~Ar １１ each independently represents deuterium, a halogen, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aromatic amino group having 12 to 36 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 5 of these aromatic groups. f and g represent the number of substitutions, and each independently represents an integer of 0 to 4.

2. In the general formula (1), X is N-Ar ６ 2. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is represented by the formula:

3. In the general formula (2), each Y is independently N-Ar. ９ 2. The photoelectric conversion element according to claim 1, wherein the element is represented by any one of the following formulas:

4. In the general formula (1), L １ 2. The photoelectric conversion element according to claim 1, wherein is represented by any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, and a substituted or unsubstituted terphenyl group.

5. The photoelectric conversion element according to claim 1, wherein the general formula (1) is represented by any one of the following formulas (3) to (8):

6. The compound represented by the general formula (1) according to claim 1 is a material for a photoelectric conversion element for imaging, and an image-capturing photoelectric conversion element comprising the compound.

7. The photoelectric conversion element for imaging according to claim 6, characterized in that the material for the photoelectric conversion element for imaging represented by the general formula (1) has an energy level of the highest occupied molecular orbital (HOMO) obtained by a structure optimization calculation using density functional calculation B3LYP / 6-31G(d) of -4.3 eV or less.

8. The photoelectric conversion element for imaging described in claim 6, characterized in that the material for the photoelectric conversion element for imaging represented by the general formula (1) has an energy level of the lowest unoccupied molecular orbital (LUMO) obtained by the structural optimization calculation of -2.5 eV or higher.

9. The material for a photoelectric conversion element for imaging represented by the general formula (1) is 1×10 －６ cm ２ 7. The image pickup photoelectric conversion element according to claim 6, wherein the element has a hole mobility of at least 1.0 V.

10. The photoelectric conversion element for imaging according to claim 6, wherein the compound represented by the general formula (1) is amorphous.

11. The photoelectric conversion element for imaging according to claim 6, wherein the compound represented by the general formula (1) is used as a hole transporting material of the photoelectric conversion element for imaging.

12. A photoelectric conversion element for imaging having a photoelectric conversion layer and an electron blocking layer between two electrodes, characterized in that at least one of the photoelectric conversion layer and the electron blocking layer contains a material for photoelectric conversion elements for imaging represented by general formula (1) as described in claim 6.

13. The image pickup photoelectric conversion element according to claim 12, characterized in that the electron blocking layer contains a material for image pickup photoelectric conversion elements represented by the general formula (1).

14. The photoelectric conversion element for imaging according to claim 13, characterized in that the photoelectric conversion layer contains an electron transporting material.

15. The photoelectric conversion element for imaging according to claim 14, characterized in that the electron transporting material contains a fullerene derivative.

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