WO2025018227A1 - Photoelectric conversion element material, and photoelectric conversion element using same - Google Patents

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

The present invention relates to a material for a photoelectric conversion element and a photoelectric conversion element using the same, and in particular to a material for a photoelectric conversion element that is useful for an imaging device.

In recent years, there has been progress in the development of organic electronics devices that use thin films formed from organic semiconductors. Examples include electroluminescent elements, solar cells, transistor elements, and photoelectric conversion elements. In particular, among these, the development of organic EL elements, which are electroluminescent elements made from organic materials, has progressed the most, and as applications in smartphones, TVs, and other devices progress, development aimed at further increasing functionality is also ongoing.

Among these, photoelectric conversion elements for imaging have traditionally been developed and put to practical use using P-N junctions of inorganic semiconductors such as silicon, and studies are being conducted to improve the functionality of digital cameras and smartphone cameras, as well as applications in surveillance cameras and automotive sensors. However, challenges to responding to these various uses include increasing sensitivity and miniaturizing pixels (increasing resolution). Photoelectric conversion elements that use inorganic semiconductors mainly employ a method in which color filters corresponding to the three primary colors of light, RGB, are placed on the light receiving part of the photoelectric conversion element to obtain color images. With this method, RGB color filters are placed on a flat surface, which poses problems in terms of the efficiency of incident light utilization and resolution (Non-Patent Documents 1 and 2).

As one solution to these problems with photoelectric conversion elements, photoelectric conversion elements that use organic semiconductors instead of inorganic semiconductors are being developed (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 problem of high sensitivity and high resolution by stacking photoelectric conversion elements made of organic semiconductors that correspond to the three primary colors of light. An element has also 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).

Here, a photoelectric conversion element using an organic semiconductor is an element that has a photoelectric conversion layer made of a thin film of an organic semiconductor between two electrodes, and a hole blocking layer and/or an electron blocking layer is disposed between the photoelectric conversion layer and the two electrodes as necessary. In a photoelectric conversion element, excitons are generated by absorbing light having 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 move to each electrode, converting the light into an electrical signal. In order to promote this process, a method of applying a bias voltage between both electrodes is generally used, but one of the challenges is to reduce the leakage current from both electrodes that occurs when the bias voltage is applied. For this reason, it can be said that controlling the movement of holes and electrons within a photoelectric conversion element is the key to expressing the characteristics of the photoelectric conversion element.

The organic semiconductors used in each layer of a photoelectric conversion element can be broadly 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 efforts have been made to develop organic semiconductors with 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), but the current situation is such that they cannot be said to have sufficient characteristics.

In addition, various compounds have been disclosed that are excellent as hole transport materials or electron blocking materials for organic electroluminescent devices 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 of photoelectric conversion elements for imaging is that, for example, in order for a camera to capture clear images in a dark place, it is important to increase the difference between the current value when the shutter is closed and the current value when the shutter is open (light-dark ratio), so the lower the current value in a dark place, the better, and the higher the current value in a bright place, the better. In other words, it is important to have a "high light-dark ratio."
On the other hand, in organic electroluminescent devices, the characteristics to be improved include the voltage required to pass a constant current, the luminous efficiency, and the device lifespan, which are significantly different from the characteristics required for photoelectric conversion devices for imaging.
In addition, it is important for an organic solar cell to generate a large amount of current both in a dark place and in a light place, and the required properties are different from those of an imaging photoelectric conversion element, for which a low current value in a dark place is preferable. As described above, the required properties are different between the hole transport material and electron blocking material of an organic electroluminescent element or organic solar cell and the hole transport material and electron blocking material of an imaging photoelectric conversion element, so whether a material that is excellent as a hole transport material and electron blocking material of an organic electroluminescent element or organic solar cell is also excellent as a hole transport material and electron blocking material of an imaging photoelectric conversion element is not clear until it is confirmed by experiment.

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

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

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

Patent Documents 5 and 6 propose organic EL devices that use indolocarbazole derivatives as the light-emitting layer material.

JP 2018-85427 A JP 2011-228614 A WO2022114065 WO2022114067 US20170271598 WO2011099374

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

　To advance the application of imaging photoelectric conversion elements to digital cameras, smartphone cameras, surveillance cameras, automotive sensors, and the like, organicization is key to achieving even higher sensitivity and resolution. In order to increase the contrast of images, a material that has both a low dark current value and a high bright current value and exhibits a high light-to-dark ratio is 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 that uses this material.

As a result of extensive research, the inventors discovered 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 light-to-dark ratio, and thus completed the present invention.

　一般式（１）において、Ｌ^１は、置換若しくは未置換の炭素数６～１８の芳香族炭化水素基、又はこれらの芳香族基が２～６個連結してなる置換若しくは未置換の連結芳香族基を表す。環Ｂは、隣接環と任意の位置で縮合し、式（１Ｂ）で表される６員環を表す。環Ｃは、隣接環と任意の位置で縮合し、式（１Ｃ）で表される５員環を表す。ＸはО、Ｓ、Ｎ-Ａｒ^６で表される。Ａｒ^１～Ａｒ^６は、それぞれ独立して、重水素、ハロゲン、炭素数１～２０のアルキル基、置換若しくは未置換の炭素数１２～３６の芳香族アミノ基、置換若しくは未置換の炭素数６～１８の芳香族炭化水素基、置換若しくは未置換の炭素数３～１８の芳香族複素環基、又はこれらの芳香族基が２～１０個連結してなる置換若しくは未置換の連結芳香族基を表す。ただし、ＸがＮ-Ａｒ^６で表される場合、Ａｒ^６は下記一般式（２）で表される構造を一つ以上含む。ａ～ｅは置換数を表し、a～ｄはそれぞれ独立に０～４の整数を表し、ｅは０～２の整数を表す。

　一般式（２）において、Ｙはそれぞれ独立してＮ-Ａｒ^９、Ｏ、Ｓ、Ｃ-Ａｒ^１０Ａｒ^１１のいずれかで表される。Ａｒ^７～Ａｒ^１１は、それぞれ独立に、重水素、ハロゲン、炭素数１～２０のアルキル基、置換若しくは未置換の炭素数１２～３６の芳香族アミノ基、置換若しくは未置換の炭素数６～１８の芳香族炭化水素基、置換若しくは未置換の炭素数３～１８の芳香族複素環基、又はこれらの芳香族基が２～５個連結してなる置換若しくは未置換の連結芳香族基を表す。ｆ、ｇは置換数を表し、それぞれ独立に０～４の整数を表す。なお、Ａｒ^６に前記一般式（２）を含むとき、前記一般式（１）に記載のＮと結合するのは、Ａｒ^７～Ａｒ^１１であってもよく、前記式（２）で表される縮合環と直接結合してもよい。なお、前記一般式（１）に記載のNとは、前記式（１Ｃ）で表されるＸがＮ-Ａｒ^６で表され、このときＡｒ^６が結合しているNのことを指す。 The present invention provides a material for a photoelectric conversion element, 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 represented by O, S, or N-Ar ^{6. Ar 1} to Ar ⁶ each independently represent 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, when X is represented by N- ^Ar6 , ^Ar6 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), Y is independently represented by any one of N-Ar ⁹ , O, S, and C-Ar ¹⁰ and Ar ^11. Ar ⁷ to Ar ¹¹ are independently represented by 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 represent an integer of 0 to 4. When Ar ⁶ contains the general formula (2), it may be Ar ⁷ to Ar ¹¹ that are bonded to N described in the general formula (1), or it may be directly bonded to the fused ring represented by the formula (2). Incidentally, N in the general formula (1) refers to N to which Ar ⁶ is bonded when X in the formula (1C) is represented by N-Ar ⁶ .

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

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

The material for an imaging photoelectric conversion element represented by the general formula (1) preferably has a hole mobility of 1×10 ⁻⁶ cm ² /Vs or more, and is preferably amorphous.

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

The present invention also provides an imaging photoelectric conversion element 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 imaging photoelectric conversion elements represented by the general formula (1).

The photoelectric conversion element of the present invention can contain a material for photoelectric conversion elements 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.

The photoelectric conversion element of the present invention uses a material for photoelectric conversion elements 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 caused by application of a bias voltage when converting light into electrical energy. As a result, it is believed that a photoelectric conversion element that achieves a low dark current value and a high light-dark ratio can be obtained. Therefore, the material of the present invention is useful as a material for photoelectric conversion elements in photoelectric conversion film stacked imaging devices.

1 is a schematic cross-sectional view showing an example of the structure of a photoelectric conversion element used in the present invention.

The imaging photoelectric conversion element of the present invention is a photoelectric conversion element having at least one organic layer between two electrodes and converting 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 be simply 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).

The compound represented by the general formula (1) is described below.

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 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 represented by any of O, S, and N-Ar ⁶ , but is preferably represented by 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 is preferably 0 in each case. Here, ^Ar6 contains one or more structures represented by the following general formula (2).

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

Ar ¹ to Ar ⁶ each independently represent 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; 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. Ar ⁷ to Ar ¹¹ each independently represent 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; preferably 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, more preferably 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, and even more preferably 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. Furthermore, when Ar ¹ to Ar ⁶ represent the linked aromatic group, the number of links is preferably 2 to 6, and more preferably 2 to 4. Furthermore, when Ar ⁷ to Ar ¹¹ represent the linked aromatic group, the number of links is preferably 2 to 4, and more preferably 2 to 3. Furthermore, when Ar ³ , Ar ⁴ , and Ar ⁶ to Ar ¹¹ represent the linked aromatic group containing an aromatic heterocyclic group, it is preferable that they do 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, tetrazine, etc. When Ar ¹ to Ar ¹¹ are groups having a hydrogen atom, the hydrogen atom may be substituted with deuterium or a halogen.

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

Specific examples of when Ar ¹ to Ar ¹¹ are halogen include a fluoro group, a chloro group, a bromo group, and an iodo group.

When Ar ¹ to Ar ¹¹ are alkyl groups having 1 to 20 carbon atoms, they may be any of linear, branched, and cyclic alkyl groups, and are preferably linear, branched, or cyclic alkyl groups 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.

When Ar ¹ to Ar ¹¹ are unsubstituted aromatic amino groups 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 are preferably 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 benzothienodibenzothi Examples of such groups 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.

When Ar ¹ to Ar ¹¹ are unsubstituted aromatic hydrocarbon groups having 6 to 18 carbon atoms, examples of the groups include those obtained by removing one hydrogen atom from known aromatic hydrocarbon groups. However, when Ar ⁶ includes the general formula (2) and Ar ⁷ to Ar ¹¹ are bonded to N in the general formula (1), examples of the groups include those obtained by removing two hydrogen atoms from known aromatic hydrocarbon groups. Specifically, examples of the groups 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. Preferred are benzene, naphthalene, anthracene, triphenylene, and pyrene.

When Ar ¹ to Ar ¹¹ are unsubstituted aromatic heterocyclic groups having 3 to 18 carbon atoms, examples of the groups include aromatic heterocyclic groups having one hydrogen atom removed therefrom, provided that when Ar ⁶ includes the general formula (2) and Ar ⁷ to Ar ¹¹ are bonded to N in the general formula (1), examples of the groups include known aromatic heterocyclic groups having two hydrogen atoms removed therefrom. Specific examples of such compounds 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, benzothienodibenzothiophene, dinaphthothiophene; Examples of the aromatic compounds 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.
However, when Ar ³ , Ar ⁴ , and Ar ⁶ to Ar ¹¹ are the above-mentioned aromatic heterocyclic groups and the above-mentioned linking aromatic groups containing aromatic heterocyclic groups, it is preferred that they do 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.

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 single bonds. These linking aromatic groups may be linear or branched. The linking position when the benzene rings are linked together may be ortho, meta, or para, but is preferably a para or meta linking. 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. The aromatic groups that constitute the linking aromatic group do not include aromatic amino groups.

When Ar ¹ to Ar ¹¹ are an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linking aromatic group, they 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. When Ar ¹ to Ar ¹¹ are aromatic amino groups, the aromatic group may have a substituent, and examples of the substituent in this case are the same as those in the case where the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group has a substituent.

The alkyl group having 1 to 20 carbon atoms as the substituent may be any of linear, branched, and cyclic alkyl groups, and is preferably a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. Specific examples 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.

Specific examples of the halogen as the 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.

Preferred specific examples of the compound represented by general formula (1), which is the material for the photoelectric conversion element of the present invention, are shown below, but are not limited to these. In the following formula, D represents deuterium, and the numbers represent the number of deuterium substitutions.

 

The compound represented by the general formula (1) of the present invention can be obtained by synthesizing it using various organic synthesis reactions 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, and then purifying it using known methods such as recrystallization, column chromatography, and sublimation purification, but is not limited to this method.

The photoelectric conversion element material of the present invention preferably has an energy level of the highest occupied molecular orbital (HOMO) obtained by structural optimization calculation using density functional 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.

The photoelectric conversion element material of the present invention preferably has an energy level of the lowest unoccupied molecular orbital (LUMO) obtained by structural optimization calculation using density functional 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.

The material for photoelectric conversion elements of the present invention preferably has a difference (absolute value) between the HOMO energy level and the LUMO energy level 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.

The material for photoelectric conversion devices of the present invention preferably has a hole mobility of 1×10 ⁻⁶ cm ² /Vs or more, more preferably has a hole mobility of 1×10 ⁻⁴ cm ² /Vs to 1×10 ⁻¹ cm ² /Vs, and further preferably has a hole mobility of 2.2×10 ⁻⁴ cm ² /Vs to 1×10 ⁻² cm ² /Vs. The hole mobility can be evaluated by known methods such as a method using a FET transistor element, a method using a time-of-flight method, or an SCLC method.

The material for photoelectric conversion elements of the present invention is preferably amorphous. The fact that it is amorphous can be confirmed by various methods, for example, by the absence of detection of a peak by the XRD method or the absence of detection of an endothermic peak by the DSC method.

Next, an imaging photoelectric conversion element using the material for photoelectric conversion elements of the present invention will be described, but the structure of the imaging photoelectric conversion element of the present invention is not limited thereto.
Fig. 1 is a cross-sectional view showing a schematic 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 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 is not limited to that shown in Fig. 1, and layers can be added or omitted as necessary.

-electrode-
The electrode used in the imaging photoelectric conversion element using the imaging photoelectric conversion element material of the present invention has a function of collecting holes and electrons generated in the photoelectric conversion layer. In addition, a function of allowing light to enter the photoelectric conversion layer is also required. 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 has conductivity, and examples thereof include conductive transparent materials such as ITO, IZO, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO ₂ and FTO, metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel and tungsten, inorganic conductive materials such as copper iodide and copper sulfide, conductive polymers such as polythiophene, polypyrrole and polyaniline, etc. These materials may be mixed and used as necessary. In addition, two or more layers may be laminated.

- 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. The photoelectric conversion layer may be formed of a single photoelectric conversion material, but may also be formed in combination with a P-type organic semiconductor material that is a hole transport material or an N-type organic semiconductor material that is an electron transport material. Two or more types of P-type organic semiconductors may be used, or two or more types of N-type organic semiconductors may be used. It is desirable to use a dye material having a function of absorbing light of a desired wavelength in the visible region as one or more of these P-type organic semiconductors and/or N-type semiconductors. As the P-type organic semiconductor material that is a hole transport material, the compound represented by the general formula (1) of the present invention can be used.

The P-type organic semiconductor material may be any material having hole transport properties. It is preferable to use 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 be mixed and used. Furthermore, a compound represented by general formula (1) may be mixed with other P-type organic semiconductor materials.

The other P-type organic semiconductor material may be any material having hole transport properties, and examples of such materials that can be used include compounds having a condensed polycyclic aromatic group such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene, 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 and other compounds having a π-excess aromatic group, aromatic amine derivatives, styrylamine derivatives, benzidine derivatives, porphyrin derivatives, phthalocyanine derivatives, and quinacridone derivatives.

In addition, a polymer-type P-type organic semiconductor material may be used as the other P-type organic semiconductor material. Specific examples include polyphenylenevinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole 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.

The N-type organic semiconductor material may be any material that has electron transport properties, and examples of such materials include naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid diimide, fullerenes, and azole derivatives such as imidazole, thiazole, thiadiazole, oxazole, oxadiazole, and triazole. Two or more types of N-type organic semiconductor materials may be mixed and used.

-Electron blocking layer-
The electron blocking layer is provided to suppress dark current caused by injection of electrons from one electrode into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. It also has a function as a hole transporter that transports holes generated by charge separation in the photoelectric conversion layer to the electrode, and a single layer or multiple layers can be arranged as necessary. The electron blocking layer can be made of a P-type organic semiconductor material that is a hole transport material. As the P-type organic semiconductor material, any material having hole transport properties is sufficient, and it is preferable to use a compound represented by general formula (1), but other P-type organic semiconductor materials may also be used. In addition, the compound represented by general formula (1) may be mixed with other P-type organic semiconductor materials. As the other P-type organic semiconductor material, any material having hole transport properties is sufficient, and specifically, the compounds exemplified as other P-type organic semiconductor materials at the photoelectric conversion layer are exemplified.

In addition, 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. In addition, 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.

-Hole blocking layer-
The hole blocking layer is provided to suppress dark current caused by holes being injected from one electrode into the photoelectric conversion layer when a bias voltage is applied between the two electrodes. It also has a function of transporting electrons generated by charge separation in the photoelectric conversion layer to the electrode, and a single layer or multiple layers can be arranged as necessary. The hole blocking layer can be made of an N-type organic semiconductor having electron transport properties.
The N-type organic semiconductor material may be any material having electron transport properties, and examples thereof include polycyclic aromatic polycarboxylic anhydrides and imidized products thereof, such as naphthalene tetracarboxylic diimide and perylene tetracarboxylic 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, fluorenylidene methane derivatives, anthraquinodimethane derivatives and anthrone derivatives, bipyridine derivatives, quinoline derivatives, indolocarbazole derivatives, etc. Two or more of these N-type organic semiconductor materials may be mixed and used.

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 the general formula (1), some or all of the hydrogen in the substituent may be deuterium.
Furthermore, a part or all of the hydrogen contained in the compounds used as the N-type organic semiconductor material and the P-type organic semiconductor material may be deuterium.

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

The imaging photoelectric conversion element of the present application preferably has a current value in a dark place of 5.0×10 ^-10 A/cm ² or less, more preferably 1.0×10 ^-12 A/cm ² to 5.0×10 ^-10 A/cm 2, and even more preferably 1.0×10 ^-12 A/cm ² to 4.5×10 ^-10 A/cm ² , under the measurement conditions described in Example 1 of the present application. Furthermore, the imaging photoelectric conversion element of the present application preferably has a light/dark ratio of 6.0×10 ² or more, more preferably 6.5×10 ² or more, and even more preferably 7.0×10 ² or ^more , under the measurement conditions described in Example 1 of the present application.

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

Calculation example: HOMO and LUMO calculations The HOMO and LUMO energy levels, as well as the energy difference between the HOMO and LUMO, of the above compounds A06, A28, A133, B01, B95, C07, C144, and E101 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.

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.

Below, we show a synthesis example of compound A06 as a representative example. Other compounds were also synthesized using a similar method.

　脱気窒素置換した５００ｍｌ三口フラスコにＲ１（19.5mmol）、Ｒ２（19.5mmol）、ヨウ化銅（2mmol）、炭酸カリウム（39.0mmol）を投入し、これに脱水ジオキサン５０ｍｌを加えた後、１２０℃にて６時間撹拌した。室温まで冷却した後、無機物をろ過にて取り除き、濾液に水３００ｍｌ、ジクロロメタン３００ｍｌを加え、分液ロートへ移し、有機層と水層に分画した。有機層を２００ｍｌの水で三回洗浄し、得られた有機層を硫酸マグネシウムで脱水した後、減圧濃縮した。得られた残渣を、カラムクロマトグラフィーで精製してＲ３（淡黄色固体）を得た。収量は５．３ｇ、収率は５４．６％であった。 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 added to a 500 ml three-neck flask that had been degassed and replaced with nitrogen, and 50 ml of dehydrated dioxane was added to the mixture, followed by stirring at 120°C for 6 hours. After cooling to room temperature, inorganic matter was removed by filtration, and 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, and the resulting organic layer was dehydrated with magnesium sulfate and then concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain R3 (light yellow solid). The yield was 5.3 g and the yield was 54.6%.

　脱気窒素置換した５００ｍｌ三口フラスコに合成例１で合成したＲ３（10.0mmol）、Ｒ４（12.1mmol）、ヨウ化銅（1.0mmol）、炭酸カリウム（20.1mmol）を投入し、これにジメチルイミダゾリジノン５０ｍｌを加えた後、１８０℃にて８時間撹拌した。室温まで冷却した後、無機物をろ過にて取り除き、濾液に水２００ｍｌ、ジクロロメタン２００ｍｌを加え、分液ロートへ移し、有機層と水層に分画した。有機層を２００ｍｌの水で三回洗浄し、得られた有機層を硫酸マグネシウムで脱水した後、減圧濃縮した。得られた残渣を、カラムクロマトグラフィーで精製してＡ０６（淡黄色固体）を得た。収量は６．０ｇ、収率は８０．８％であった。得られた固体をＸＲＤ法にて評価したがピークが検出されなかったため、本化合物は非晶質であることがわかった。（APCI-TOFMS, m/z＝739[M+H]⁺） 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 put into a 500 ml three-neck flask that had been degassed and replaced with nitrogen, and 50 ml of dimethylimidazolidinone was added to the mixture, followed by stirring at 180°C for 8 hours. After cooling to room temperature, inorganic matter was removed by filtration, and 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, and the resulting organic layer was dehydrated with magnesium sulfate and then concentrated under reduced pressure. The resulting residue was purified by column chromatography to obtain A06 (light yellow solid). The yield was 6.0 g and 80.8%. 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] ⁺ )

On a glass substrate having a transparent electrode made of ITO with a thickness of 110 nm, compound A06 was formed as an organic layer with a thickness of about 3 μm by vacuum deposition. Then, a device having an electrode made of aluminum (Al) with a thickness of 70 nm was used to measure charge mobility by a time-of-flight method. The hole mobility was 1.5×10 ⁻⁴ cm ² /Vs.

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

Example 1
On an electrode made of ITO having a film thickness of 70 nm formed on a glass substrate, a film of compound A06 was formed to a thickness of 10 nm as an electron blocking layer at a vacuum degree of 4.0×10 ⁻⁵ Pa. Next, as a photoelectric conversion layer, 2Ph-BTBT, F6-SubPc-OC6F5, and fullerene (C60) were co-evaporated to a thickness of 200 nm at an evaporation rate ratio of 4:4:2 to form a film. Subsequently, dpy-NDI was evaporated to a thickness of 10 nm to form a hole blocking layer. Finally, aluminum was deposited to a thickness of 70 nm as an electrode 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 . Furthermore, when a voltage of 2.6 V was applied and light was irradiated from a height of 10 cm onto the ITO electrode side using an LED adjusted to have an irradiation light wavelength of 500 nm and 1.6 μW, the current (light current) was 2.9×10 ⁻⁷ A/cm ^2. In other words, 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.

Examples 2 to 9
A photoelectric conversion element was prepared in the same manner as in Example 1, except that the compound shown in Table 3 was used for the electron blocking layer.

Comparative Examples 1 to 3
A photoelectric conversion element was prepared in the same manner as in Example 1, except that the compound shown in Table 3 was used for the electron blocking layer.
The results of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 3.

The compounds used in the examples and comparative examples are shown below.

By using the material for photoelectric conversion elements for imaging represented by the general formula (1) of the present invention, appropriate movement of holes and electrons can be achieved within the photoelectric conversion element for imaging, making it possible to reduce the leakage current caused by application of a bias voltage when converting light into electrical energy. As a result, it is believed that a photoelectric conversion element of the present invention that achieves a low dark current value and a high light-dark ratio can be obtained. Therefore, the material represented by the general formula (1) of the present invention is useful as a material for photoelectric conversion elements in photoelectric conversion film stacked imaging devices.

1 Electrode 2 Hole blocking layer 3 Photoelectric conversion layer 4 Electron blocking layer 5 Electrode 6 Substrate

Claims (15)

A photoelectric conversion element comprising a material for a photoelectric conversion element, the material 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 represented by O, S, or N-Ar ^{6. Ar 1} to Ar ⁶ each independently represent 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, when X is represented by N- ^Ar6 , ^Ar6 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 general formula (2), Y is independently any one of N-Ar ⁹ , O, S, and C-Ar ¹⁰ and Ar ^11. Ar ⁷ to Ar ¹¹ are independently 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 are the number of substitutions and are each independently an integer of 0 to 4. 2. The photoelectric conversion element according to claim 1, wherein, in the general formula (1), X is represented by N- ^Ar6 . 2. The photoelectric conversion element according to claim 1, wherein, in the general formula (2), each Y is independently represented by any one of N-Ar ⁹ , O and S. 2. The photoelectric conversion element according to claim 1, wherein, in the general formula (1), ^L1 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. 2. The photoelectric conversion element according to claim 1, wherein the general formula (1) is represented by the following formulas (3) to (8).

The compound represented by the general formula (1) described in claim 1 is a material for a photoelectric conversion element for imaging, and a photoelectric conversion element for imaging, comprising the compound. The material for an imaging photoelectric conversion element represented by the general formula (1) is characterized in that the energy level of the highest occupied molecular orbital (HOMO) obtained by a structural optimization calculation using density functional calculation B3LYP/6-31G(d) is -4.3 eV or less. The material for an image-capturing photoelectric conversion element represented by the general formula (1) is characterized in that the energy level of the lowest unoccupied molecular orbital (LUMO) obtained by the structural optimization calculation is -2.5 eV or higher. The image-capturing photoelectric conversion element described in claim 6. 7. The image pickup photoelectric conversion element according to claim 6, wherein the material for an image pickup photoelectric conversion element represented by the general formula (1) has a hole mobility of 1×10 ⁻⁶ cm ² /Vs or more. The photoelectric conversion element for imaging according to claim 6, characterized in that the compound represented by the general formula (1) is amorphous. The photoelectric conversion element for imaging according to claim 6, characterized in that the compound represented by the general formula (1) is used as a hole transport material of the photoelectric conversion element for imaging. The photoelectric conversion element for imaging described in claim 6, characterized in that the photoelectric conversion element for imaging has a photoelectric conversion layer and an electron blocking layer between two electrodes, and at least one of the photoelectric conversion layer and the electron blocking layer contains the material for photoelectric conversion elements for imaging represented by the general formula (1). The photoelectric conversion element for imaging according to claim 12, characterized in that the electron blocking layer contains a material for a photoelectric conversion element for imaging represented by the general formula (1). The photoelectric conversion element for imaging according to claim 13, characterized in that the photoelectric conversion layer contains an electron transport material. 15. The image pickup photoelectric conversion element according to claim 14, wherein the electron transporting material comprises a fullerene derivative.

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