Material for photoelectric conversion element for imaging, and photoelectric conversion element for imaging using same

Abstract

Provided are: a material with which the high sensitivity and high resolution of a photoelectric conversion element for imaging are achieved; and a photoelectric conversion element for imaging using the same.　This material for a photoelectric conversion element for imaging is characterized by being composed of an indolocarbazole compound represented by general formula (1), and this photoelectric conversion element for imaging uses the same. In general formula (1), a ring B represents a 6-membered ring represented by formula (1B) and condensed with an adjacent ring at an arbitrary position. A ring C represents a 5-membered ring represented by formula (1C) and condensed with an adjacent ring at an arbitrary position. At least one among Ar1-Ar5 is represented by general formula (2) or the like. Moreover, * in general formula (2) represents a bonding point to general formula (1).

Description

Material for photoelectric conversion element for imaging and photoelectric conversion element for imaging 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] In the field of photoelectric conversion elements, progress has been made in the development and practical application of elements 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, in which the RGB color filters are placed 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 within 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. However, these do not have sufficient properties and have not yet been put to commercial use.

[0007] 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.

[0008] Patent Document 2 proposes a device in which a chrysenodithiophene derivative is used as a P-type organic semiconductor in a photoelectric conversion layer, and a fullerene or a subphthalocyanine derivative is used as an N-type organic semiconductor.

[0009] Patent Documents 3 and 4 propose devices using a carbazole derivative in an electron blocking layer disposed between a photoelectric conversion layer and an electrode. Patent Document 5 proposes a device using a pyrene derivative or a triphenylene derivative in an electron blocking layer disposed between a photoelectric conversion layer and an electrode. Patent Document 6 proposes a device using a condensed aromatic compound such as benzothienodibenzothiophene or benzofuranyldibenzofuran in a photoelectric conversion layer.

[0010] On the other hand, Patent Document 7 discloses an organic EL device using an indolocarbazole compound substituted with a nitrogen-containing six-membered ring structure. Patent Document 8 discloses an organic EL device using an indolocarbazole compound substituted with a carbazole structure. However, these documents all relate to organic EL devices and do not specifically disclose that the compounds exhibit excellent properties as materials for photoelectric conversion devices.

[0011] Japanese Patent Publication No. 2018-85427 Japanese Patent Publication No. 2019-54228 Japanese Patent Publication No. 2011-228614 Japanese Patent Publication No. 2021-77888 Japanese Patent Publication No. 2015-153910 WO2021 / 090619 WO2008 / 056746 WO2009 / 136595

[0012] 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)

[0013] Further improvements in sensitivity and resolution are required for imaging photoelectric conversion elements to improve the functionality of digital cameras and smartphone cameras, and to be applied to surveillance cameras, automotive sensors, etc. In light of this current situation, the present invention aims to provide a material that achieves high sensitivity and high resolution in imaging photoelectric conversion elements, and an imaging photoelectric conversion element using the same.

[0014] As a result of extensive research into the above-mentioned problems, the present inventors have discovered that the process of generating holes and electrons by charge separation of excitons in the photoelectric conversion layer of a photoelectric conversion element, and the process of transferring holes and electrons within the photoelectric conversion element, can be efficiently carried out by using an indolocarbazole compound having a specific carbazole compound as a substituent, and have thus completed the present invention. In particular, the present inventors have newly discovered that the use of an indolocarbazole compound having a specific carbazole structure as a substituent controls the processes of charge generation and charge transfer within the photoelectric conversion element, thereby improving the light-to-dark ratio, which leads to higher sensitivity of the photoelectric conversion element.

[0015] The present invention provides a material for a photoelectric conversion element for imaging, comprising an indolocarbazole compound represented by the following general formula (1): In the general formula (1), ring B is fused to an adjacent ring at any position to form a 6-membered ring represented by formula (1B). Ring C is fused to an adjacent ring at any position to form a 5-membered ring represented by formula (1C). １ ~Ar ５ each independently represents deuterium, a cyano group, a halogen atom, a nitro group, 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 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 20 of these aromatic groups, １ ~Ar ５ At least one of Ar is represented by any one of the following general formulas (2) to (8). １ ~Ar ５ is a group having a hydrogen atom, the hydrogen atom may be substituted with deuterium or halogen. a, b, and c represent the number of substitutions, a and b each independently represent an integer of 0 to 4, and c represents an integer of 0 to 2. In the general formulae (2) to (8), * represents the point of attachment to the general formula (1), and L １ ~L ４ represents a direct bond, 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 3 of these aromatic rings. ６ ~Ar １６ are each independently deuterium, a cyano group, a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino 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 3 aromatic rings thereof; d to k represent the number of substitutions, d, g, h, j, and k each independently represent an integer of 0 to 4, and e, f, and i each independently represent an integer of 0 to 3.

[0016] It is preferable that the general formula (1) is represented by any one of the following general formulas (9) to (13). That is, the indolocarbazole compound represented by the general formula (1) is preferably represented by the following general formula (9), preferably represented by the following general formula (10), preferably represented by the following general formula (11), preferably represented by the following general formula (12), and preferably represented by the following general formula (13). The form of the general formula (1) can be appropriately selected from the indolocarbazole compounds represented by the general formulas (9) to (13). For example, the general formula (1) is preferably represented by any one of the following general formulas (9) to (11), and (13), or preferably represented by any one of the following general formulas (10), (11), and (13), or preferably represented by any one of the following general formulas (9), (11) to (13). In these general formulas (9) to (13), Ar １ ~Ar ５ and a to c are the same as those described in the general formula (1).

[0017] Moreover, the general formulas (5) to (8) are preferably represented by the following general formulas (5A) to (8C). １ ~L ４ , Ar １２ ~Ar １６ , h to k are the same as those described in the general formulae (5) to (8).

[0018] Ar in the above general formula (1) １ or Ar ５ At least one of the groups is preferably represented by any one of the general formulas (2) to (8). １ or Ar ５ At least one of the above general formulas (5A) to (8C) is preferably represented by any one of the above general formulas (2) to (8). １ , and L ３ is preferably a single bond.

[0019] The photoelectric conversion element material preferably has a highest occupied molecular orbital (HOMO) energy level of −4.5 eV or less, and a lowest unoccupied molecular orbital (LUMO) energy level of −2.5 eV or more, as determined by a geometry optimization calculation using density functional theory calculation B3LYP / 6-31G(d).

[0020] The material for the photoelectric conversion element is 1×10 －６ cm ２ It is preferable that the material for a photoelectric conversion element has a hole mobility of 1 / Vs or more. In addition, it is preferable that the material for a photoelectric conversion element is amorphous.

[0021] The material for a photoelectric conversion element can be used as a hole transport material.

[0022] The present invention also provides 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 the above-described material for photoelectric conversion elements.

[0023] The photoelectric conversion element of the present invention may contain the above-mentioned material for a photoelectric conversion element in the electron blocking layer, and may contain an electron transporting material such as a fullerene derivative in the photoelectric conversion layer.

[0024] The use of the material for a photoelectric conversion element for imaging of the present invention 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 due to the application of a bias voltage when converting 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 brightness / 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.

[0025] 1 is a cross-sectional view showing a structural example of a photoelectric conversion element used in the present invention.

[0026] 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 general formula (1) above. Specifically, in an imaging photoelectric conversion element having a photoelectric conversion layer and an electron blocking layer between two electrodes, the material for a photoelectric conversion element represented by general formula (1) above is contained in at least one of the photoelectric conversion layer and the electron blocking layer. Hereinafter, the material for an imaging photoelectric conversion element comprising a compound represented by general formula (1) will simply be referred to as a photoelectric conversion element material. It may also be referred to as the material of the present invention or the compound represented by general formula (1).

[0027] The compound represented by the above general formula (1) will be explained below.

[0028] In the general formula (1), ring B is fused to an adjacent ring at any position to form a 6-membered ring represented by formula (1B), and ring C is fused to an adjacent ring at any position to form a 5-membered ring represented by formula (1C).

[0029] Preferred forms of the general formula (1) are represented by the general formulas (9) to (13). That is, the indolocarbazole compound represented by the general formula (1) is preferably represented by the general formula (9), preferably represented by the following general formula (10), preferably represented by the following general formula (11), preferably represented by the following general formula (12), and preferably represented by the following general formula (13). The form of the general formula (1) can be appropriately selected from the indolocarbazole compounds represented by the general formulas (9) to (13). For example, the general formula (1) is preferably represented by any of the following general formulas (9) to (11), and (13), or is preferably represented by any of the following general formulas (10), (11), and (13), or is preferably represented by any of the following general formulas (9), (11) to (13).

[0030] In the general formulas (9) to (13), Ar １ ~Ar ５ and a to c are the same as those described in the general formula (1).

[0031] In the above general formula (1), Ar １ ~Ar ５ At least one of the above is represented by any one of the general formulas (2) to (8), but Ar １ , or Ar ５ At least one of the above is preferably represented by any one of general formulas (2) to (8), and more preferably represented by any one of (2), (3), (5) and (8).

[0032] In addition, in the general formula (1), Ar １ ~Ar ５ At least one of the general formulas (2) to (8) is preferably represented by any one selected from the group consisting of the general formulas (5A), (5B), (5C), (6A), (6B), (6C), (7A), (7B), (7C), (8A), (8B), and (8C). Among these, the general formulas (5A), (5B), (5C), (8A), (8B), and (8C) are more preferably represented by any one of the general formulas (5A), (5B), (5C), (8A), (8B), and (8C).

[0033] In the general formulae (5A) to (8C), L １ ~L ４ , Ar １２ ~Ar １６ , h to k are the same as those described in the general formulae (5) to (8).

[0034] Ar １ ~Ar ５ each independently represents deuterium, a cyano group, a halogen atom, a nitro group, 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 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 20 of these aromatic groups, １ ~Ar ５ At least one of the above is represented by any one of the general formulae (2) to (8). Preferably, it is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 6 to 18 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 20 of these aromatic groups. When these groups contain a hydrogen atom, the hydrogen atom may be substituted with deuterium or halogen.

[0035] The alkyl group having 1 to 20 carbon atoms 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 methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-dodecyl, n-tetradecyl, and n-octadecyl groups; branched saturated hydrocarbon groups such as isopropyl, isobutyl, neopentyl, 2-ethylhexyl, and 2-hexyloctyl groups; and saturated alicyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, cyclooctyl, and 4-butylcyclohexyl groups.

[0036] Specific examples of aralkyl groups having 7 to 38 carbon atoms include benzyl, phenethyl, phenylpropyl, phenylbutyl, naphthylmethyl, and triphenylenylmethyl. Specific examples of alkenyl groups having 2 to 20 carbon atoms include ethylene, propylene, butylene, pentene, cyclopentene, hexene, cyclohexene, and octene. Specific examples of alkynyl groups having 2 to 20 carbon atoms include acetylene, propyne, butyne, and pentyne. Specific examples of acyl groups having 2 to 20 carbon atoms include formyl, acetyl, propionyl, and benzoyl. Specific examples of alkoxy groups having 1 to 20 carbon atoms include methoxy, ethoxy, propoxy, and butoxy.

[0037] Ar １ ~Ar ５ When Ar represents a linking aromatic group, the number of links is preferably 2 to 12, more preferably 2 to 6. １ ~Ar ５ When represents a linking aromatic group, the number of linkages includes two carbazole (CBZ) groups described in formulas (2) to (8).

[0038] a, b, and c represent the number of substitutions, and a and b each independently represent an integer of 0 to 4, preferably 0 to 2, and more preferably 0 to 1. c represents an integer of 0 to 2, preferably 0 to 1, and more preferably 0.

[0039] L１ ~L ４ represents a direct bond, 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 or 3 of these aromatic rings, and preferably represents a direct bond.

[0040] Ar ６ ~Ar １６ are each independently deuterium, a cyano group, a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino 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 two or three of these aromatic rings; d to k represent the number of substitutions; d, g, h, j, and k each independently represent an integer of 0 to 4, preferably 0 to 2, and more preferably 0 to 1. e, f, and i each independently represent an integer of 0 to 3, preferably 0 to 2, and more preferably 0.

[0041] Specific examples of the aryl group of the aromatic amino group include 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, and a spirobifluorenyl group, and preferred are a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a phenanthrenyl group, a fluorenyl group, and 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, phenylcarbazole, biphenylcarbazole, benzocarbazole, indoloindole, carbazolocarbazole, benzofurocarbazole, benzothienocarbazole, carboline, thiophene, benzothiophene, naphthothiophene, dibenzothiophene, benzothienonaphthalene, benzothienobenzothiophene, benzothienodibenzoyl Examples include groups in which one hydrogen atom has been removed from benzothiophene, dinaphthothiophene, dinaphthothienothiophene, naphthobenzothiophene, furan, benzofuran, naphthofuran, dibenzofuran, benzofuronaphthalene, benzofurobenzofuran, benzofurodibenzofuran, dinaphthofuranofuran, naphthobenzofuran, pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, quinoxaline, and the like, and among these, preferred are groups derived from dibenzofuran, dibenzothiophene, carbazole, benzofurocarbazole, or benzothienocarbazole.

[0042] Examples of the aromatic hydrocarbon group having 6 to 18 carbon atoms include groups obtained by removing one hydrogen atom from a known aromatic hydrocarbon. Examples of the aromatic hydrocarbon include groups derived from 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. Preferred are groups derived from benzene, naphthalene, anthracene, triphenylene, or pyrene.

[0043] Examples of the aromatic heterocyclic group having 3 to 18 carbon atoms include a group obtained by removing one hydrogen atom from an aromatic heterocyclic group. Examples of the aromatic heterocyclic group 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, and carboline, thiophene, benzothiophene, naphthothiophene, dibenzothiophene, benzothienonaphthalene, benzothienobenzothiophene, and benzothienodibenzothiophene. Examples include sulfur-containing aromatic compounds having a thiophene ring such as dinaphthothiophene, dinaphthothienothiophene, naphthobenzothiophene, and benzothienocarbazole, oxygen-containing aromatic compounds having a furan ring such as furan, benzofuran, naphthofuran, dibenzofuran, benzofuronaphthalene, benzofurobenzofuran, benzofurodibenzofuran, dinaphthofuranofuran, naphthobenzofuran, and benzofurocarbazole, pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, and quinoxaline. Preferred are groups derived from dibenzofuran, dibenzothiophene, carbazole, benzothienodibenzothiophene, benzofurodibenzofuran, indolocarbazole, benzofurocarbazole, or benzothienocarbazole.

[0044] In this specification, the term "linked aromatic group" refers to an aromatic group in which two or more aromatic groups are linked by single bonds. These linking aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para, but para- or meta-linking is preferred. 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.

[0045] Ar １ ~Ar １６When 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, an alkyl group having 1 to 20 carbon atoms, a cyano group, an alkylsilyl group, etc. The alkyl group having 1 to 20 carbon atoms may be any of a linear, branched, or cyclic alkyl group, and is preferably deuterium, a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms, or a cyano group. Specific examples thereof include linear saturated hydrocarbon groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-dodecyl, n-tetradecyl, and n-octadecyl groups; branched saturated hydrocarbon groups such as isopropyl, isobutyl, neopentyl, 2-ethylhexyl, and 2-hexyloctyl groups; and saturated alicyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, cyclooctyl, 4-butylcyclohexyl, and 4-dodecylcyclohexyl groups.

[0046] Preferred specific examples of the compound represented by formula (1) which is the material for the photoelectric conversion element of the present invention are shown below, but the invention is not limited to these.

[0047]

[0048] 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.

[0049] The material for photoelectric conversion elements of the present invention preferably has an energy level of the highest occupied molecular orbital (HOMO) obtained by a geometry optimization calculation using density functional theory calculation B3LYP / 6-31G(D) of −4.5 eV or less, more preferably in the range of −6.0 eV to −4.5 eV, and even more preferably in the range of more than −5.0 eV and less than −4.5 eV.

[0050] 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 −2.5 eV to −0.5 eV, and even more preferably in the range of more than −1.5 eV and less than −0.5 eV.

[0051] 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 in the range of 2.5 eV to 4.5 eV, and even more preferably in the range of 3.5 eV to 4.5 eV.

[0052] The material for a photoelectric conversion element of the present invention has a viscosity of 1×10 －６ cm ２ / Vs or more, and preferably 1×10 －６ cm ２ / Vs~1cm ２ / Vs, and more preferably 1×10 －５ cm ２ / Vs~1×10 －１ cm ２The 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.

[0053] The material for a photoelectric conversion element of the present invention is preferably amorphous. The amorphous nature can be confirmed by various methods, for example, by the absence of a peak detected by XRD or the absence of an endothermic peak detected by DSC.

[0054] Next, an imaging photoelectric conversion element using the material for a photoelectric conversion element of the present invention will be described, but the structure of the imaging photoelectric conversion element of the present invention is not limited thereto.

[0055] Figure 1 is a cross-sectional view schematically showing an example of the 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 shown in Figure 1, i.e., 1 represents an electrode, 2 represents an electron blocking layer, 3 represents a photoelectric conversion layer, 4 represents a hole blocking layer, 5 represents an electrode, and 6 represents a substrate. The structure is not limited to that shown in Figure 1, and layers can be added or omitted as necessary.

[0056] - 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 ２Examples 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.

[0057] 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 capable 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.

[0058] The P-type organic semiconductor material may be any material having hole transport properties, and is preferably a material represented by general formula (1). However, other P-type organic semiconductor materials may also be used. Two or more materials represented by general formula (1) may be mixed and used. Furthermore, a compound represented by general formula (1) may be mixed with other P-type organic semiconductor materials.

[0059] Other p-type organic semiconductor materials 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.

[0060] Examples of polymer-type p-type organic semiconductor materials include polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. Two or more selected from the compound represented by general formula (1), p-type organic semiconductor materials, and polymer-type p-type organic semiconductor materials may be mixed and used.

[0061] The N-type organic semiconductor material may be any material having electron transport properties, such as 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.

[0062] -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 two electrodes. It 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 can be arranged as needed. The electron blocking layer can be made of a P-type organic semiconductor material, which is a hole transport material. Any material with hole transport properties can be used as the P-type organic semiconductor material. The compound represented by general formula (1) is preferably used, but 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. Other p-type organic semiconductor materials 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, and carbazole derivatives; aromatic amine derivatives, styrylamine derivatives, benzidine derivatives, porphyrin derivatives, phthalocyanine derivatives, and quinacridone derivatives.

[0063] Examples of polymer-type p-type organic semiconductor materials include polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, and polythiophene derivatives. Two or more selected from the compound represented by general formula (1), p-type organic semiconductor materials, and polymer-type p-type organic semiconductor materials may be mixed and used.

[0064] -Hole Blocking Layer- The hole blocking layer is provided to suppress dark current generated when holes are 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. A single layer or multiple layers can be arranged as needed. An N-type organic semiconductor with electron transport properties can 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, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, bipyridine derivatives, quinoline derivatives, indolocarbazole derivatives, etc. Two or more of these N-type organic semiconductor materials may also be used in combination.

[0065] The hydrogen in the material of the present invention may be deuterium. That is, in addition to the hydrogen on the aromatic ring in general formula (1) or general formulas (2) to (8), 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.

[0066] 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.

[0067] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0068] Calculation Example: Calculation of HOMO and LUMO The HOMO, LUMO, and energy difference between HOMO and LUMO of the above compounds A02, A32, B05, B53, C01, C19, C23, C59, D10, D25, E09, and F02 were calculated. The calculations were performed using density functional theory (DFT), Gaussian as the 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.

[0069] The HOMO, LUMO, and energy difference between the HOMO and LUMO of comparative compounds H1, H2, H3, and H4 were calculated in the same manner. The results are shown in Table 1.

[0070]

[0071] The synthesis of compound A02 is shown below as a representative example. Other compounds were also synthesized in a similar manner.

[0072] Synthesis Example 1 (Synthesis of Intermediate R3) R1 (27.1 mmol), R2 (28.4 mmol), copper iodide (0.5 mmol), and tripotassium phosphate (81.3 mmol) were placed in a degassed, nitrogen-purged 500 ml three-neck flask. 100 ml of dehydrated dioxane was added, followed by stirring at 120°C for 3 hours. After cooling to room temperature, inorganic matter was 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, dehydrated over magnesium sulfate, and then concentrated under reduced pressure. The resulting residue was purified by column chromatography to yield R3 (a pale yellow solid).

[0073] Synthesis Example 2 (Synthesis of Intermediate R5) A 500 ml three-neck flask was charged with R4 (19.5 mmol), R3 (21.5 mmol) synthesized in Synthesis Example 1, copper iodide (2.0 mmol), and potassium carbonate (39.0 mmol), and 50 ml of dimethylimidazolidinone was added. The mixture was then stirred 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 yield R5 (a pale yellow solid).

[0074] Synthesis Example 3 (Synthesis of A02) R5 (6.8 mmol), R6 (101.5 mmol), copper powder (20.3 mmol), and potassium carbonate (33.8 mmol) synthesized in Synthesis Example 2 were added to a 500 ml three-neck flask degassed and purged with nitrogen, and the mixture was stirred at 180°C for 8 hours. After cooling to room temperature, the 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, dehydrated over magnesium sulfate, and concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain A02 (colorless solid). The resulting solid was evaluated by XRD, but no peaks were detected, indicating that this compound was amorphous. (APCI-TOFMS, m / z 739 [M+H] + )

[0075] Property Evaluation Example: On a glass substrate on which a transparent electrode made of ITO with a thickness of 110 nm was formed, Compound A02 was formed as an organic layer by vacuum deposition 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 the time-of-flight method. As a result, the hole mobility was 2.0 × 10 －４ cm ２ / Vs.

[0076] The hole mobility was evaluated in the same manner except that compound A02 was replaced with compound A32, B01, B05, B53, C01, C19, C59, D05, D10, D25, E09, F02, H1, H2, H3, or H4. The results are shown in Table 2.

[0077]

[0078] Example 1 A vacuum of 4.0×10 was applied to an ITO film having a thickness of 70 nm formed on a glass substrate. -５ Compound A02 was deposited as an electron blocking layer at 200 Pa to a thickness of 100 nm. Next, a thin film of quinacridone was deposited as a photoelectric conversion layer to a thickness of 100 nm. Finally, an aluminum film was deposited as an electrode to a thickness of 70 nm, thereby producing a photoelectric conversion element for imaging. When a voltage of 2 V was applied using ITO and aluminum as electrodes, the current in the dark was 4.1 × 10 －１２ A / cm ２ When a voltage of 2 V was applied to the ITO electrode (transparent conductive glass) side and light was irradiated at a wavelength of 500 nm, the current was 4.0 × 10 －６ A / cm ２ When a voltage of 2 V was applied to the transparent conductive glass side, the brightness ratio was 9.8 × 10 ５ It was.

[0079] Comparative Example 1 A vacuum chamber was placed on an electrode made of ITO with a thickness of 70 nm formed on a glass substrate. -５ Compound H1 was deposited as an electron blocking layer at 200 Pa to a thickness of 100 nm. Next, quinacridone was deposited as a photoelectric conversion layer to a thickness of 100 nm. Finally, aluminum was deposited as an electrode to a thickness of 70 nm to prepare a photoelectric conversion element for imaging. When a voltage of 2 V was applied using ITO and aluminum as electrodes, the current in the dark was 6.7 × 10 －１２ A / cm ２ When a voltage of 2 V was applied to the ITO electrode side and light was irradiated at a wavelength of 500 nm, the current was 2.2 × 10 －６ A / cm ２ When a voltage of 2 V was applied to the transparent conductive glass side, the brightness ratio was 3.3 × 10 ５ It was.

[0080] Table 3 shows the results when compound A02 (Example 1) and compound H1 (Comparative Example 1) were used as the electron blocking layer.

[0081]

[0082] Example 2 A vacuum chamber was placed on an electrode made of ITO with a thickness of 70 nm formed on a glass substrate. －５ Compound A02 was deposited as an electron blocking layer to a thickness of 10 nm at 100 Pa. Next, as a photoelectric conversion layer, 2Ph-BTBT, F6-SubPc-OC6F5, and fullerene (C60) were co-deposited to a thickness of 200 nm at a deposition rate ratio of 4:4:2 to form a film. 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 4.9 × 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 3.1 × 10 －７ A / cm ２ The light-dark ratio when a voltage of 2.6 V was applied was 6.3 × 10 ２ These results are shown in Table 4.

[0083] Examples 3 to 8 Photoelectric conversion elements were prepared in the same manner as in Example 2, except that the compounds shown in Table 4 were used for the electron blocking layer.

[0084] Comparative Examples 2 to 4 Photoelectric conversion elements were prepared in the same manner as in Example 2, except that the compounds shown in Table 4 were used for the electron blocking layer. The results of Examples 3 to 8 and Comparative Examples 2 to 4 are shown in Table 4.

[0085] The compounds used in the examples and comparative examples are listed below.

[0086]

[0087] From the above results, it is clear that the compounds of the present invention have an excellent light-to-dark ratio and are useful as materials for photoelectric conversion elements for imaging.

[0088] REFERENCE SIGNS LIST 1 Electrode 2 Hole blocking layer 3 Photoelectric conversion layer 4 Electron blocking layer 5 Electrode 6 Substrate

Claims

1. The imaging photoelectric conversion element has a photoelectric conversion layer and an electron blocking layer between two electrodes, and is characterized in that at least one of the photoelectric conversion layer and the electron blocking layer contains a material for photoelectric conversion elements comprising an indolocarbazole compound represented by the following general formula (1): 【Chemistry 1】 In general formula (1), 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). Ar １ ~Ar ５ each independently represents deuterium, a cyano group, a halogen, a nitro group, 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 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 20 of these aromatic groups, and Ar １ ~Ar ５ At least one of Ar is represented by any one of the following general formulas (2) to (8). １ ~Ar ５ When represents a group having a hydrogen atom, the hydrogen atom may be substituted with deuterium or halogen. a, b, and c represent the number of substitutions, a and b each independently represent an integer of 0 to 4, and c represents an integer of 0 to 2. 【Chemistry 2】 In the general formulas (2) to (8), * represents the point of attachment to the general formula (1), L １ ~L ４ represents a direct bond, 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. Ar ６ ~Ar １６ each independently represents deuterium, a cyano group, a substituted or unsubstituted diarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted arylheteroarylamino group having 12 to 36 carbon atoms, a substituted or unsubstituted diheteroarylamino 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 3 of these aromatic rings, d to k represent the number of substitutions; d, g, h, j, and k each independently represent an integer of 0 to 4; and e, f, and i each independently represent an integer of 0 to 3.

2. 2. The imaging photoelectric conversion element according to claim 1, wherein the general formula (1) is represented by any one of the following general formulas (9) to (13): 【Chemistry 3】 In the general formulas (9) to (13), Ar １ ~Ar ５ and a to c are the same as those described in the general formula (1).

3. 3. The imaging photoelectric conversion element according to claim 2, wherein the general formula (1) is represented by any one of the general formulas (9) to (11) and (13).

4. 4. The imaging photoelectric conversion element according to claim 3, wherein the general formula (1) is represented by any one of the general formulas (10), (11), and (13).

5. 2. The imaging photoelectric conversion element according to claim 1, wherein the general formulas (5) to (8) are represented by the following general formulas (5A) to (8C): 【Chemistry 4】 【Chemistry 5】 In general formulae (5A) to (8C), L １ ~L ４ , Ar １２ ~Ar １６ , h to k, and * are the same as those described in the general formulas (5) to (8).

6. Ar in the general formula (1) １ Or Ar ５ 2. The image pickup photoelectric conversion element according to claim 1, wherein at least one of the above is represented by any one of general formulas (2) to (8).

7. Ar in the general formula (1) １ Or Ar ５ 6. The imaging photoelectric conversion element according to claim 5, wherein at least one of the above is represented by any one of general formulas (5A) to (8C).

8. L in the general formulas (2) to (8) １ , and L ３ The imaging photoelectric conversion element according to claim 1 , wherein is a single bond.

9. 2. The imaging photoelectric conversion element according to claim 1, wherein the indolocarbazole compound represented by the general formula (1) has an energy level of a highest occupied molecular orbital (HOMO) of −4.5 eV or less, which is obtained by a structure optimization calculation using density functional calculation B3LYP / 6-31G(d).

10. 10. The imaging photoelectric conversion element according to claim 9, wherein the indolocarbazole compound represented by the general formula (1) has an energy level of a lowest unoccupied molecular orbital (LUMO) obtained by the structural optimization calculation of -2.5 eV or more.

11. The indolocarbazole compound represented by the general formula (1) is 1×10 －６ cm ２ 2. The imaging photoelectric conversion element according to claim 1, wherein the element has a hole mobility of at least 1.0 V.

12. 2. The image capturing photoelectric conversion element according to claim 1, wherein the indolocarbazole compound represented by the general formula (1) is amorphous.

13. 2. The image capturing photoelectric conversion element according to claim 1, wherein the indolocarbazole compound represented by the general formula (1) is used as a hole transport material of the image capturing photoelectric conversion element.

14. (delete)

15. 2. The image capturing photoelectric conversion element according to claim 1, wherein the electron blocking layer contains a material for a photoelectric conversion element comprising an indolocarbazole compound represented by the general formula (1).

16. 2. The imaging photoelectric conversion element according to claim 1, wherein the photoelectric conversion layer contains an electron transporting material.

17. 2. The imaging photoelectric conversion element according to claim 1, wherein the electron blocking layer contains a material for a photoelectric conversion element comprising an indolocarbazole compound represented by general formula (1), and the photoelectric conversion layer contains a fullerene derivative.

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