Photoelectric conversion element having an organic thin film made of a compound having an indenocarbazole ring

Abstract

The main objective of the present invention is to provide a photoelectric conversion device using a compound having excellent heat resistance and charge transportability, and an image capturing device using the photoelectric conversion device.　The present invention provides a photoelectric conversion device comprising an organic thin film containing a compound having an indenocarbazole ring structure represented by the following general formula (1). (In the formula, A represents a single bond, a divalent substituted or unsubstituted aromatic hydrocarbon group, etc.; Ar1, Ar2 and Ar3 each represent a substituted or unsubstituted aromatic hydrocarbon group etc.; R1 to R9 each represent a hydrogen atom or an optionally substituted linear or branched alkyl group having 1-6 carbon atoms; and R10 and R11 each represent an optionally substituted linear or branched alkyl group having 1-6 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, etc.)

Description

[Technical field]

[0001] The present invention relates to an organic thin film suitable for various photoelectric conversion elements, and more particularly to a photoelectric conversion element, particularly an imaging element, having an organic thin film made of a compound having an indenocarbazole ring structure. [Background technology]

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

[0003] Previous imaging elements have used inorganic materials such as Si and Se films, and the two mainstream imaging methods were a three-plate type that uses a prism to separate light into the three primary colors, and a single-plate type that uses a color filter. However, the three-plate type has a high light utilization rate but is difficult to miniaturize because it uses a prism, while the single-plate type does not use a prism and is relatively easy to miniaturize, but instead uses a color filter, resulting in poor resolution and low light utilization rate (Non-Patent Document 2).

[0004] Compared to inorganic materials, organic materials absorb light of specific wavelengths better, so by combining materials that match each wavelength, it is possible to construct an imaging element that can efficiently use each of the three primary colors without using a prism. This makes it possible to create a compact imaging element with high light utilization efficiency. In addition, there is a possibility that value can be added, such as flexibility that cannot be achieved with inorganic materials, and the ability to increase the area by coating during the manufacturing process (Non-Patent Document 1).

[0005] For this reason, photoelectric conversion elements using organic materials are expected to be developed into next-generation imaging elements, and several groups have reported on them. For example, there are examples in which quinacridone and quinazoline derivatives are used in photoelectric conversion elements (Patent Document 3), benzothiebenzothiophene derivatives are used in photoelectric conversion elements (Patent Document 4), and indolocarbazole is used in photoelectric conversion elements (Patent Document 5). In general, organic imaging elements are intended to achieve high contrast and power saving, and it is believed that performance can be improved by aiming to reduce dark current. Therefore, in order to reduce leakage current from the conversion unit in the dark, a method of inserting a hole blocking layer or an electron blocking layer between the photoelectric conversion unit and the electrode unit is sometimes used.

[0006] The provision of hole-blocking layers and electron-blocking layers is a technique commonly used in the field of organic electronics. These layers are disposed at the interfaces between electrodes or conductive films and other films in the constituent films of devices, respectively, to control the reverse movement of holes or electrons while allowing the rapid movement of necessary charges.

[0007] In addition, a photoelectric conversion element characterized by containing a blocking material with a Tg of 140°C or higher has been proposed (Patent Document 1). Unlike other organic electronic devices such as organic electroluminescence (EL), high thermal stability is required for photoelectric conversion element applications, but it has not been said that such devices have had sufficient performance to date. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US9085537 [Patent Document 2] US9196837 [Patent Document 3] JP 2007-234651 A [Patent Document 4] JP 2018-170487 A [Patent Document 5] US20190288040 [Patent Document 6] US20190081251 [Non-patent literature]

[0009] [Non-Patent Document 1] Adv. Mater. 28, 4766 (2016) [Non-Patent Document 2] Journal of the Institute of Image Information and Communications Technology, 60,3,291 (2006) Summary of the Invention

[0010] The present invention has been made in view of the above circumstances, and has as its main object to provide a photoelectric conversion element that utilizes a compound having excellent heat resistance and charge transport properties, and an imaging element that uses the same.

[0011] In order to achieve the above object, the present inventors have focused on the fact that a carbazole skeleton has high charge transport properties and also has excellent heat resistance, and have conducted extensive research aimed at further improving heat resistance. As a result, they have found that an organic thin film containing a specific compound having an indenocarbazole ring structure can solve the above problems, and have thus completed the present invention.

[0012] That is, the present invention relates to the following items. 1) A photoelectric conversion element having an organic thin film containing a compound having an indenocarbazole ring structure represented by the following general formula (1):

[0013] [ka] (In the formula, A represents a single bond, a divalent substituted or unsubstituted aromatic hydrocarbon group, a divalent substituted or unsubstituted aromatic heterocyclic group, or a divalent substituted or unsubstituted condensed polycyclic aromatic group; Ar1, Ar2, and Ar3 may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. A and Ar2, or Ar2 and Ar3 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. R1 to R9 may be the same or different from each other and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. R 10 and R 11may be the same or different, and represent a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0014] 2) The photoelectric conversion element according to 1), wherein the compound having an indenocarbazole ring structure is a compound represented by the following general formula (2):

[0015] [ka] (In the formula, Ar1 and Ar4 may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. R1 to R9, R 12 ~R 18may be the same or different, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, an optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms, a cycloalkyloxy group of 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. R 10 and R 11 may be the same or different, and represent a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0016] 3) The photoelectric conversion element according to 1), wherein the compound having an indenocarbazole ring structure is a compound represented by the following general formula (3):

[0017] [ka] (In the formula, Ar1 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. R1 to R9, R 19 ~R 26 may be the same or different, and represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, an optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, an optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms, an optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms, a cycloalkyloxy group of 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring. R 10 and R 11 may be the same or different, and represent a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group, and may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0018] 4) The photoelectric conversion element according to any one of 1) to 3), in which a first electrode, a first buffer layer, a photoelectric conversion layer, and a second electrode are laminated in this order, and the first buffer layer is an organic thin film containing the compound having the indenocarbazole ring structure.

[0019] 5) An imaging element comprising the photoelectric conversion element according to any one of 1) to 4). [Brief description of the drawings]

[0020] [Figure 1] 1 shows an example of the configuration of a photoelectric conversion element of the present invention. [Diagram 2] 1 shows an example of the configuration of a photoelectric conversion element of the present invention. [Diagram 3] 1 is a (log J-V) graph of Example 16 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention is a photoelectric conversion element characterized by using an organic thin film containing a compound having an indenocarbazole ring structure represented by the above general formula (1).

[0022] In the above general formula (1), the "divalent aromatic hydrocarbon group", the "divalent substituted or unsubstituted aromatic heterocyclic group", or the "divalent substituted or unsubstituted condensed polycyclic aromatic group" in the "divalent aromatic hydrocarbon group", the "divalent aromatic heterocyclic group", or the "divalent condensed polycyclic aromatic group" can include a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, an anthracenylene group, a thienylene group, a furanylene group, and a phenanthrenylene group. Furthermore, it can also be selected from an arylene group having 6 to 30 carbon atoms and a heteroarylene group having 2 to 30 carbon atoms.

[0023] Specific examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" in the above general formula (1) include a phenyl group, a biphenylyl group, a terphenylyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a fluorenyl group, a spirobifluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, group, triphenylenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group, acridinyl group, carbolinyl group, etc. Furthermore, it can also be selected from aryl groups having 6 to 30 carbon atoms and heteroaryl groups having 2 to 30 carbon atoms.

[0024] Specific examples of the "linear or branched alkyl group having 1 to 6 carbon atoms", "cycloalkyl group having 5 to 10 carbon atoms", or "linear or branched alkenyl group having 2 to 6 carbon atoms" in the "linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent", "cycloalkyl group having 5 to 10 carbon atoms which may have a substituent", or "linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent" in the above general formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, a vinyl group, an allyl group, an isopropenyl group, and a 2-butenyl group.

[0025] Specific examples of the "linear or branched alkyloxy group having 1 to 6 carbon atoms" or "cycloalkyloxy group having 5 to 10 carbon atoms" in the "linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent" or the "cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent" in the above general formula (1) include a methyloxy group, an ethyloxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, an n-hexyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a 1-adamantyloxy group, and a 2-adamantyloxy group.

[0026] Specific examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the above general formula (1) include aryloxy groups having 6 to 30 carbon atoms, such as a phenyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthioxyl group, an anthracenyloxy group, and a phenanthrenyloxy group.

[0027] Specific examples of the "substituents" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "substituted methylene group", "linear or branched alkyl group of 1 to 6 carbon atoms which may have a substituent", "cycloalkyl group of 5 to 10 carbon atoms which may have a substituent", "linear or branched alkenyl group of 2 to 6 carbon atoms which may have a substituent", "linear or branched alkyloxy group of 1 to 6 carbon atoms which may have a substituent", or "cycloalkyloxy group of 5 to 10 carbon atoms which may have a substituent" in the above general formula (1) include a deuterium atom, a cyano group, a nitro group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a silyl group such as a trimethylsilyl group or a triphenylsilyl group; a linear or branched alkyl group of 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group; linear or branched alkyloxy groups; alkenyl groups such as vinyl and allyl; aryloxy groups such as phenyloxy and tolyloxy; arylalkyloxy groups such as benzyloxy and phenethyloxy; aromatic carbonyl groups such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenanthrenyl, fluorenyl, spirobifluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl, and triphenylenyl; Examples of the substituent include a hydrogen atom or a condensed polycyclic aromatic group; and aromatic heterocyclic groups such as a pyridyl group, a thienyl group, a furyl group, a pyrrolyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and a carbolinyl group, and these substituents may be further substituted with the substituents exemplified above.

[0028] In the present invention, it is preferable that R1 to R9 in the above general formula (1) are hydrogen atoms because of ease of synthesis. From the viewpoint of heat resistance and charge mobility, it is preferable that Ar1, Ar2, and Ar3 are substituted or unsubstituted aromatic hydrocarbon groups, and R 10 and R 11 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituted or unsubstituted aromatic hydrocarbon group. 10 and R 11 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0029] From the viewpoint of heat resistance and charge mobility, one of the preferred embodiments of the present invention is a compound in which A is a substituted or unsubstituted aromatic hydrocarbon group. In this case, it is preferable that Ar2 is a substituted or unsubstituted aromatic hydrocarbon group, and A and Ar2 are bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0030] Specific examples of the compound in which A in the above general formula (1) is a substituted or unsubstituted aromatic hydrocarbon group include the compound represented by the above general formula (2).

[0031] Examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group", or "substituted or unsubstituted condensed polycyclic aromatic group" in the above general formula (2) include the groups exemplified in the explanation of the above general formula (1).

[0032] In the above general formula (2), the "linear or branched alkyl group having 1 to 6 carbon atoms", the "cycloalkyl group having 5 to 10 carbon atoms", or the "linear or branched alkenyl group having 2 to 6 carbon atoms" in the "linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted", "cycloalkyl group having 5 to 10 carbon atoms which may be substituted", or "linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted" includes the groups exemplified in the explanation of the above general formula (1).

[0033] In the above general formula (2), the "linear or branched alkyloxy group having 1 to 6 carbon atoms" or the "cycloalkyloxy group having 5 to 10 carbon atoms" in the "linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted" or the "cycloalkyloxy group having 5 to 10 carbon atoms which may be substituted" includes the groups exemplified in the explanation of the above general formula (1).

[0034] Examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the above general formula (2) include the groups exemplified in the explanation of the above general formula (1).

[0035]

[0043] In the above general formula (2), examples of the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "substituted methylene group", "C 1 to C 6 linear or branched alkyl group which may have a substituent", "C 5 to C cycloalkyl group which may have a substituent", "C 2 to C 6 linear or branched alkenyl group which may have a substituent", "C 1 to C 6 linear or branched alkyloxy group which may have a substituent", or "C 5 to C cycloalkyloxy group which may have a substituent" include the groups exemplified in the explanation of the above general formula (1).

[0036] In the present invention, from the viewpoints of heat resistance and charge mobility, Ar1 and Ar4 in the above general formula (2) are preferably substituted or unsubstituted aromatic hydrocarbon groups, more preferably aryl groups having 6 to 30 carbon atoms, and particularly preferably aryl groups having 6 to 18 carbon atoms. From the same viewpoint, R in the above general formula (2) 10 and R 11 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituted or unsubstituted aromatic hydrocarbon group, and more preferably a linear or branched alkyl group having 1 to 6 carbon atoms, or an unsubstituted aromatic hydrocarbon group. 10 and R 11 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0037] In addition, R1 to R9 and R in the above general formula (1) are easily synthesized. 12 ~R 18 is preferably a hydrogen atom.

[0038] From the viewpoint of heat resistance and charge mobility, one of the preferred embodiments of the present invention is a compound in which A in the above general formula (1) is a single bond. In this case, it is preferable that Ar2 and Ar3 are substituted or unsubstituted aromatic hydrocarbon groups and are bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring, and it is more preferable that Ar2 and Ar3 are unsubstituted aromatic hydrocarbon groups and are bonded to each other via a single bond to form a ring.

[0039] A specific example of the compound in which A in the above general formula (1) is a single bond is the compound represented by the above general formula (3).

[0040] Examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group", or "substituted or unsubstituted condensed polycyclic aromatic group" in the above general formula (3) include the groups exemplified in the explanation of the above general formula (1).

[0041] In the above general formula (3), the "linear or branched alkyl group having 1 to 6 carbon atoms", the "cycloalkyl group having 5 to 10 carbon atoms", or the "linear or branched alkenyl group having 2 to 6 carbon atoms" in the "linear or branched alkyl group having 1 to 6 carbon atoms which may be substituted", "cycloalkyl group having 5 to 10 carbon atoms which may be substituted", or "linear or branched alkenyl group having 2 to 6 carbon atoms which may be substituted" includes the groups exemplified in the explanation of the above general formula (1).

[0042] In the above general formula (3), the "linear or branched alkyloxy group having 1 to 6 carbon atoms" or the "cycloalkyloxy group having 5 to 10 carbon atoms" in the "linear or branched alkyloxy group having 1 to 6 carbon atoms which may be substituted" or the "cycloalkyloxy group having 5 to 10 carbon atoms which may be substituted" includes the groups exemplified in the explanation of the above general formula (1).

[0043] Examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the above general formula (3) include the groups exemplified in the explanation of the above general formula (1).

[0044]

[0043] In the above general formula (3), examples of the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "substituted methylene group", "optionally substituted linear or branched alkyl group of 1 to 6 carbon atoms", "optionally substituted cycloalkyl group of 5 to 10 carbon atoms", "optionally substituted linear or branched alkenyl group of 2 to 6 carbon atoms", "optionally substituted linear or branched alkyloxy group of 1 to 6 carbon atoms", or "optionally substituted cycloalkyloxy group of 5 to 10 carbon atoms" include the groups exemplified in the explanation of the above general formula (1).

[0045] In the present invention, from the viewpoints of heat resistance and charge mobility, Ar1 in the above general formula (3) is preferably a substituted or unsubstituted aromatic hydrocarbon group, more preferably an aryl group having 6 to 30 carbon atoms, and particularly preferably an aryl group having 6 to 18 carbon atoms. From the same viewpoint, R in the above general formula (3) 10 and R 11 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituted or unsubstituted aromatic hydrocarbon group, and more preferably a linear or branched alkyl group having 1 to 6 carbon atoms, or an unsubstituted aromatic hydrocarbon group. 10 and R 11 may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0046] In addition, R1 to R9 and R in the above general formula (1) are easily synthesized. 19 ~R 26 is preferably a hydrogen atom.

[0047] Among the compounds having an indenocarbazole ring structure represented by the above general formula (1), specific examples of preferred compounds are shown below, but the present invention is not limited to these compounds.

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] The above-mentioned compound having an indenocarbazole ring structure can be synthesized according to a method known per se (for example, Patent Document 2).

[0054] These compounds can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization using a solvent, crystallization, etc. The compounds can be identified by NMR analysis. As physical property values, it is preferable to measure the glass transition point (Tg) and work function. The glass transition point (Tg) is an index of stability in a thin film state, and the work function is an index of hole transportability.

[0055] The glass transition point (Tg) can be measured using a powder with a high-sensitivity differential scanning calorimeter (DSC3100S, manufactured by Bruker AXS).

[0056] The work function can be measured, for example, by forming a 100 nm thin film on an ITO substrate and using an ionization potential measuring device (PYS-202, manufactured by Sumitomo Heavy Industries, Ltd.).

[0057] The compound having an indenocarbazole ring structure represented by the above general formula (1) can be used to form an organic thin film by known methods such as vapor deposition, spin coating, and inkjet. The compound having an indenocarbazole ring structure represented by the above general formula (1) can be used to form a film alone, or can be used to form a film by mixing a plurality of types. Furthermore, the compound can be used to form a film by mixing with other compounds within a range that does not impair the effects of the present invention.

[0058] The organic thin film containing the compound having the indenocarbazole ring structure represented by the above general formula (1) is suitable for use in photoelectric conversion elements, particularly imaging elements. The photoelectric conversion element may have, for example, a first electrode (anode), a first buffer layer, a photoelectric conversion layer, and a second electrode (cathode) in this order, and the first buffer layer is an organic thin film containing the compound having the indenocarbazole ring structure represented by the above general formula (1). In such a multilayer structure, it is possible to add a layer, and for example, it may have a first electrode, a first buffer layer, a photoelectric conversion layer, a second buffer layer, and a second electrode in this order. Moreover, the organic thin film containing the compound having an indenocarbazole ring structure represented by the above general formula (1) can also be used in a photoelectric conversion layer.

[0059] The photoelectric conversion layer in the photoelectric conversion element of the present invention may be an organic material or an inorganic material, as long as it can generate a signal charge according to the amount of light received. When the photoelectric conversion layer is an organic material, the organic semiconductor film may be a single layer or multiple layers. When the photoelectric conversion layer is a single layer, a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film of a p-type organic semiconductor and an n-type organic semiconductor (bulk heterostructure) is used. When the photoelectric conversion layer is a multiple layer, it is a structure in which two or more of a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film of a p-type organic semiconductor and an n-type organic semiconductor are laminated, and a buffer layer can be inserted between the layers.

[0060] The photoelectric conversion element of the present invention can obtain stability against thermal load by using an organic thin film containing a compound having an indenocarbazole ring structure represented by the above general formula (1) in the first buffer layer included in the element.

[0061] 1 and 2 show examples of the configuration of the photoelectric conversion element of the present invention. In the photoelectric conversion element of Fig. 1 and Fig. 2, when light is irradiated, the photoelectric conversion layer 3 is photoexcited, and holes and electrons are separated as carriers. Thereafter, the first electrode from which the holes are extracted is the anode 1, and the second electrode from which the electrons are extracted is the cathode 5. Fig. 1 and Fig. 2 show a configuration in which a first buffer layer 2 is provided between the photoelectric conversion layer 3 and the anode 1, and a second buffer layer 4 is provided between the photoelectric conversion layer 3 and the cathode 5. Although not shown in the figure, a different layer can be further inserted between the photoelectric conversion layer 3 and the first buffer layer 2.

[0062] A p-type organic semiconductor is a donor organic semiconductor, and is mainly represented by an organic compound with a hole transporting property, which is a compound that has a tendency to easily donate electrons. Examples of p-type organic semiconductors include, but are not limited to, acene-based materials such as naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, pentacene derivatives, quinacridone derivatives, chrysene derivatives, fluoranthene derivatives, phthalocyanine derivatives, subphthalocyanine derivatives, metal complexes having a heterocyclic compound as a ligand, benzothiophene derivatives, dinaphthothienothiophene derivatives, dianthracenothienothiophene derivatives, benzobisbenzothiophene derivatives, thienobisbenzothiophene, dibenzothienobisbenzothiophene derivatives, dithienobenzodithiophene derivatives, dibenzothienodithiophene derivatives, benzodithiophene derivatives, naphthodithiophene derivatives, anthracenodithiophene derivatives, tetracenodithiophene derivatives, and pentacenodithiophene derivatives; triarylamine compounds; amine-based derivatives such as carbazole compounds; and indenocarbazole derivatives.

[0063] An n-type organic semiconductor is an acceptor organic semiconductor, and is mainly represented by an electron transporting organic compound, which is an organic compound that has a tendency to accept electrons. More specifically, when two organic compounds are contacted, the organic compound that has a larger electron affinity is the acceptor organic compound. Therefore, any organic compound that has electron accepting properties can be used as the acceptor organic compound. For example, condensed aromatic carbon ring compounds (naphthalene, anthracene, fullerene, phenanthrene, tetracene, pyrene, perylene, fluoranthene, or derivatives thereof), 5- to 7-membered heterocyclic compounds containing nitrogen atoms, oxygen atoms, and sulfur atoms (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, Examples of the metal complexes having, as a ligand, an oxazole, an indazole, a benzimidazole, a benzotriazole, a benzoxazole, a benzothiazole, a carbazole, a purine, a triazolopyridazine, a triazolopyrimidine, a tetrazaindene, an oxadiazole, an imidazopyridine, a pyrazine, a pyrrolopyridine, a thiadiazolopyridine, a dibenzazepine, a tribenzazepine, etc.), a polyarylene compound, a fluorene compound, a cyclopentadiene compound, a silyl compound, or a nitrogen-containing heterocyclic compound include metal complexes having such a ligand. However, the present invention is not limited to this, and as described above, any organic compound having a larger electron affinity than the organic compound used as the donor organic compound can be used as the acceptor organic semiconductor.

[0064] The anode and cathode are not particularly limited as long as they are conductive materials that are generally used as electrodes, and examples thereof include metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, and mixtures thereof. Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), and titanium oxide, titanium oxynitride (TiN x Ox ), metal nitrides such as titanium nitride (TiN), metals such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), and aluminum (Al), as well as mixtures or laminates of these metals with conductive metal oxides, organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, and laminates of these with ITO.

[0065] A second buffer layer may be inserted between the second electrode (cathode) and the photoelectric conversion layer, and the material used therefor is preferably a material with a work function deeper than that of the material used for the first buffer layer. For example, organic molecules and organometallic complexes containing nitrogen-containing heterocycles such as pyridine, quinoline, acridine, indole, imidazole, benzimidazole, and phenanthroline are preferred, as are materials with low absorption in the visible light region. When forming a thin film of about 5 nm to 20 nm, fullerenes and their derivatives that have absorption in the visible light region can also be used. EXAMPLES

[0066] Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

[0067] Example 1 <Synthesis of 12,12-dimethyl-10-phenyl-7-(9-phenyl-9H-carbazol-3-yl)-10,12-dihydroindeno[2,1-b]carbazole; compound (1-1)> In a nitrogen-substituted reaction vessel, 18.5 g of N-(9,9-dimethyl-9H-fluoren-2-yl)-2-bromoaniline, 6.98 g of potassium acetate, and 95 ml of DMF were added, and nitrogen gas was passed through for 1 hour. 1.18 g of tetrakis(triphenylphosphine)palladium was added, and the mixture was heated and stirred at 100°C for 11 hours. The reaction solution was cooled to room temperature, poured into 300 ml of water, and then extracted with 300 ml of toluene. The organic layer was washed twice with 200 ml of water, dehydrated with anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane) to obtain 7.9 g of pale yellow powder of 12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole (yield: 55.2%).

[0068] The obtained 12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole (7.8 g), iodobenzene (3.7 ml), sodium hydrogen sulfite (0.43 g), copper powder (0.17 g), 3,5-di(tert-butyl)salicylic acid (0.69 g), potassium carbonate (5.71 g), and dodecylbenzene (10 ml) were added to a nitrogen-substituted reaction vessel and heated and stirred at 170° C. for 10 hours. The mixture was cooled to 100° C., extracted with toluene (100 ml), concentrated under reduced pressure, and crystallized from n-hexane (30 ml) to obtain 12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole (8.73 g, yield 88.3%) as a pale yellow powder.

[0069] 7.5 g of the obtained 12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole and 53 ml of DMF were added to a reaction vessel. Under ice cooling, 3.72 g of N-bromosuccinimide was added and stirred for 9 hours, and then left overnight. 260 ml of water was added and filtration was performed to obtain 8.67 g (yield 94.6%) of brownish white powder of 7-bromo-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole.

[0070] 2.0 g of the obtained 7-bromo-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole, 1.68 g of 9-phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole, 15 ml of a mixed solvent of toluene / ethanol (4 / 1, v / v), and 3.4 ml of a 2M aqueous potassium carbonate solution were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through the vessel while irradiating with ultrasonic waves for 30 minutes. 0.26 g of tetrakis(triphenylphosphine)palladium was added, and the mixture was heated and stirred at 73°C for 5 hours. After cooling to room temperature, 30 ml of toluene and 20 ml of water were added, and the mixture was separated to collect the organic layer. The organic layer was washed with saturated saline, dehydrated with anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane) to obtain 1.5 g (yield 54.7%) of white powder of 12,12-dimethyl-10-phenyl-7-(9-phenyl-9H-carbazol-3-yl)-10,12-dihydroindeno[2,1-b]carbazole.

[0071] The structure of the resulting white powder was identified by NMR. 1 The following 32 hydrogen signals were detected by H-NMR (THF-d8). δ(ppm)=8.66(1H), 8.64(1H), 8.59(1H), 8.23-8.29(1H), 7.88-7.90(1H), 7.83-7.85(1H), 7.78-7.80(1H), 7 .66-7.71(8H), 7.42-7.53(7H), 7.37-7.40(1H), 7.31-7.33(1H), 7.26-7.29(1H), 7.21-7.24(1H), 1.51(6H)

[0072] Example 2 <Synthesis of 7-[4-{(biphenyl-4-yl)-phenylamino}-phenyl]-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole; compound (1-3)> In a nitrogen-substituted reaction vessel, 3.0 g of 7-bromo-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole synthesized in Example 1, 3.7 g of (biphenyl-4-yl)-[4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborane-2-yl)phenyl]-phenylamine, 50 ml of a mixed solvent of toluene / ethanol (4 / 1, v / v), and 10 ml of a 2M aqueous potassium carbonate solution were added, and nitrogen gas was passed through for 30 minutes while irradiating with ultrasound. 0.4 g of tetrakis(triphenylphosphine)palladium was added, heated, and stirred at 73°C for 8 hours. The mixture was cooled to room temperature, and the precipitated crude product was collected by filtration. 140 ml of 1,2-dichlorobenzene was added to the crude product, which was dissolved while heating, and the insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure. By purifying the product by recrystallization using 100 ml of 1,2-dichlorobenzene, 2.7 g (yield 57.8%) of white powder of 7-[4-{(biphenyl-4-yl)-phenylamino}-phenyl]-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole was obtained.

[0073] The structure of the resulting white powder was identified by NMR. 1 The following 38 hydrogen signals were detected by H-NMR (THF-d8). δ(ppm)=8.60(1H), 8.50(1H), 7.85(1H), 7.72-7.65(7H), 7.61(2H), 7.55(2H) , 7.52(1H), 7.47(1H), 7.43-7.37(4H), 7.31-7.16(11H), 7.03(1H), 1.49(6H)

[0074] Example 3 <Synthesis of 7-[4-{bis(biphenyl-4-yl)amino}-phenyl]-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole; compound (1-4)> In a nitrogen-substituted reaction vessel, 3.0 g of 7-bromo-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole synthesized in Example 1, 4.3 g of bis(biphenyl-4-yl)-[4-(4,4,5,5-tetramethyl[1,3,2]dioxaborane-2-yl)phenyl]amine, 50 ml of a mixed solvent of toluene / ethanol (4 / 1, v / v), and 10 ml of a 2M aqueous potassium carbonate solution were added, and nitrogen gas was passed through for 30 minutes while irradiating with ultrasound. 0.4 g of tetrakis(triphenylphosphine)palladium was added, heated, and stirred at 73°C for 8 hours. The mixture was cooled to room temperature, and the precipitated crude product was collected by filtration. 140 ml of 1,2-dichlorobenzene was added to the crude product, which was dissolved while heating, and the insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure. By purifying the product by recrystallization using 100 ml of 1,2-dichlorobenzene, 3.7 g (yield 71.6%) of white powder of 7-[4-{bis(biphenyl-4-yl)amino}-phenyl]-12,12-dimethyl-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole was obtained.

[0075] The structure of the resulting white powder was identified by NMR. 1 The following 42 hydrogen signals were detected by H-NMR (THF-d8): δ (ppm) = 8.60 (1H), 8.52 (1H), 7.85 (1H), 7.75-7.57 (15H), 7.53 (1H), 7.47 (1H), 7.43-7.38 (6H), 7.32-7.22 (10H), 1.49 (6H).

[0076] Example 4 <Synthesis of 10-(biphenyl-4-yl)-12,12-dimethyl-7-(9-phenyl-9H-carbazol-3-yl)-10,12-dihydroindeno[2,1-b]carbazole; compound (1-5)> In a nitrogen-substituted reaction vessel, 35.5 g of 12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole synthesized in Example 1, 35.0 g of 4-bromobiphenyl, 6.0 g of sodium hydrogen sulfite, 2.4 g of copper powder, 9.4 g of 3,5-di(tert-butyl)salicylic acid, 31.2 g of potassium carbonate, and 52 ml of dodecylbenzene were added and heated, and stirred at 190°C for 26 hours. The mixture was cooled to 120°C, 35 ml of toluene was added and stirred, and the crude product was collected by filtration. 1.6 L of toluene was added to the crude product, heated, and extracted at 110°C, then cooled to room temperature and concentrated under reduced pressure. Crystallization from 120 ml of methanol gave 48.5 g (yield 88.1%) of white powder of 10-(biphenyl-4-yl)-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole.

[0077] 42.5g of the obtained 10-(biphenyl-4-yl)-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole and 2.5L of DMF were added to a reaction vessel, heated to 70°C to dissolve, cooled to room temperature, added 17.4g of N-bromosuccinimide, and stirred for 7 hours. 2.5L of water was added, and filtration was performed to obtain 34.9g (yield 69.5%) of white powder of 10-(biphenyl-4-yl)-7-bromo-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole.

[0078] The obtained 10-(biphenyl-4-yl)-7-bromo-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole (16.5 g), 9-phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole (14.2 g), toluene / ethanol (4 / 1, v / v) mixed solvent (250 ml), and 2M potassium carbonate aqueous solution (48 ml) were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes while irradiating with ultrasonic waves. Tetrakis(triphenylphosphine)palladium (1.9 g) was added, heated, and stirred at 73°C for 5 hours. The mixture was cooled to room temperature, and the precipitated crude product was collected by filtration. 1,2-dichlorobenzene (450 ml) was added to the crude product, which was dissolved while heating. Insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure. The product was purified by crystallization using 150 ml of 1,2-dichlorobenzene and 300 ml of n-hexane to obtain 9.8 g (yield 45.2%) of white powder of 10-(biphenyl-4-yl)-12,12-dimethyl-7-(9-phenyl-9H-carbazol-3-yl)-10,12-dihydroindeno[2,1-b]carbazole.

[0079] The structure of the resulting white powder was identified by NMR. 1 The following 36 hydrogen signals were detected by H-NMR (THF-d8): δ (ppm) = 8.69 (1H), 8.64 (1H), 8.59 (1H), 8.28 (1H), 7.99 (2H), 7.89 (1H), 7.85-7.78 (6H), 7.66 (4H), 7.56-7.49 (6H), 7.44-7.37 (4H), 7.32 (1H), 7.27 (1H), 7.23 (1H), 1.52 (6H).

[0080] Example 5 <Synthesis of 10-(biphenyl-4-yl)-7-[4-bis(biphenyl-4-yl)aminophenyl]-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole; compound (1-6)> In a nitrogen-substituted reaction vessel, 13.0 g of 10-(biphenyl-4-yl)-7-bromo-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole synthesized in Example 6, 15.9 g of bis(biphenyl-4-yl)-[4-(4,4,5,5-tetramethyl[1,3,2]dioxaborane-2-yl)phenyl]amine, 250 ml of a mixed solvent of toluene / ethanol (4 / 1, v / v), and 51 ml of a 2M aqueous potassium carbonate solution were added, and nitrogen gas was passed through for 30 minutes while irradiating with ultrasound. 2.1 g of tetrakis(triphenylphosphine)palladium was added, heated, and stirred at 73°C for 10 hours. The mixture was cooled to room temperature, and the precipitated crude product was collected by filtration. 1.7 L of 1,2-dichlorobenzene was added to the crude product, which was dissolved while heating, and the insoluble matter was removed by filtration, and then cooled to room temperature. The precipitated solid was collected by filtration and purified by recrystallization using 1.7 L of 1,2-dichlorobenzene to obtain 13.4 g (yield 63.8%) of white powder of 10-(biphenyl-4-yl)-7-[4-bis(biphenyl-4-yl)aminophenyl]-12,12-dimethyl-10,12-dihydroindeno[2,1-b]carbazole.

[0081] The structure of the resulting white powder was identified by NMR. 1 The following 46 hydrogen signals were detected by H-NMR (THF-d8): δ (ppm) = 8.62 (1H), 8.54 (1H), 7.98 (2H), 7.86 (1H), 7.78 (4H), 7.75 (2H), 7.70 (1H), 7.63 (4H), 7.58 (4H), 7.55 (1H), 7.50 (3H), 7.43 (1H), 7.40 (4H), 7.33-7.21 (11H), 1.51 (6H).

[0082] Example 6 <Synthesis of 5,7-dihydro-5,7,7-triphenyl-2-(9-phenyl-9H-carbazol-3-yl)indeno[2,1-b]carbazole; compound (1-20)> In a nitrogen-substituted reaction vessel, 31.3 g of 5,7-dihydro-5,7-diphenylindeno[2,1-b]carbazole, 23.5 g of iodobenzene, 15.9 g of potassium carbonate, 1.2 g of sodium hydrogen sulfite, 1.9 g of 3,5-di-t-butylsalicylic acid, 0.5 g of copper powder, and 31 mL of dodecylbenzene were added and heated, followed by stirring at 190°C for 17 hours. The mixture was diluted with toluene and insoluble matter was removed by filtration. The filtrate was concentrated, and the precipitated solid was collected by filtration after adding heptane, yielding 35.3 g (94% yield) of yellow powder of 5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole.

[0083] 35.0 g of the obtained 5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole and 350 mL of dichloromethane were added to a nitrogen-substituted reaction vessel and cooled in an ice bath. 12.9 g of N-bromosuccinimide was slowly added, heated to 40°C, and stirred for 24 hours. The solid precipitated by adding methanol was collected by filtration, and the obtained solid was washed with methanol to obtain 39.5 g (yield 97%) of white powder of 2-bromo-5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole.

[0084] The obtained 2-bromo-5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole (39.5 g), toluene (320 mL), ethanol (50 mL), 9-phenylcarbazole-3-boronic acid (24.2 g), and then an aqueous solution of potassium carbonate (14.6 g) dissolved in water (52 mL) were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through while irradiating with ultrasonic waves for 30 minutes. Tetrakistriphenylphosphinepalladium (1.6 g) was added, heated, and stirred at 72°C for 18 hours. The mixture was cooled to room temperature, and the organic layer was collected by a separation operation. After washing with water and saturated saline, the mixture was dried with anhydrous magnesium sulfate and concentrated to obtain a crude product. The crude product was dissolved in toluene (360 mL), and adsorption purification was performed using silica gel, followed by adsorption purification using activated clay. The filtrate was concentrated, and the solid precipitated by adding acetone was collected by filtration. The obtained solid was recrystallized from toluene and acetone to obtain 32.3 g (yield 64%) of white powder of 5,7-dihydro-5,7,7-triphenyl-2-(9-phenyl-9H-carbazol-3-yl)indeno[2,1-b]carbazole.

[0085] The structure of the resulting white powder was identified by NMR. 1 The following 36 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=7.63(1H), 8.56(2H), 8.30(1H), 7.80-7.95(3H), 7.22-7.77(29H)

[0086] Example 7 <Synthesis of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9'-phenyl-9'H-carbazol-3'-yl)-10,12-dihydroindeno[2,1-b]carbazole; Compound (1-37)> In a nitrogen-substituted reaction vessel, 22.8 g of N-(9,9'-spirobi-9H-fluoren-2-yl)-2-bromoaniline, 9.19 g of potassium acetate, 200 ml of DMF, and 20 ml of water were added, and nitrogen gas was passed through for 30 minutes. 1.08 g of tetrakis(triphenylphosphine)palladium was added, and the mixture was heated and refluxed for 8.5 hours. After cooling to room temperature, 150 ml of water was added to the reaction solution, and the precipitated solid was filtered off. The obtained solid was dissolved in 300 ml of toluene, 11 g of silica gel was added, and the mixture was stirred at 100°C for 1 hour. Hot filtration was performed, and the obtained filtrate was dried and washed with hexane. After filtration, the obtained solid was dried at 50° C. for 15 hours to obtain 13.5 g (71% yield) of a white powder of 12,12′-spirobi[9H-fluorene]-10,12-dihydroindeno[2,1-b]carbazole.

[0087] The obtained 12,12'-spirobi[9H-fluorene]-10,12-dihydroindeno[2,1-b]carbazole (22.5 g), iodobenzene (11.5 g), sodium hydrogen sulfite (1.17 g), copper powder (0.36 g), 3,5-di-t-butylsalicylic acid (1.41 g), potassium carbonate (11.66 g), and dodecylbenzene (21 ml) were added to a nitrogen-substituted reaction vessel and heated and stirred at 190°C for 6.5 hours. The mixture was cooled to room temperature, and toluene (200 ml) was added and stirred at 80°C for 0.5 hours. The mixture was filtered while hot, and the filtrate was dried. The dried filtrate was washed with hexane. After washing, the obtained solid was dried at 50° C. for 15 hours to obtain 21.2 g (yield 78%) of 12,12′-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0088] 14.0 g of the obtained 12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole and 130 ml of chloroform were added to a reaction vessel. 5.12 g of N-bromosuccinimide was added and stirred at room temperature for 3 hours, and then 92 mg of N-bromosuccinimide was added. After stirring at 30°C for 3 hours, 200 ml of methanol was added. The precipitated solid was collected by filtration and washed with methanol. The obtained solid was dried at 50°C for 15 hours to obtain 16.1 g (yield 99%) of 7-bromo-12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0089] 22.4g of the obtained 7-bromo-12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole, 7.99g of 9-phenylcarbazole-3-boronic acid, 4.81g of potassium carbonate, 100ml of toluene, 7.5ml of ethanol, and 9ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.38g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride dichloromethane adduct was added, and the mixture was heated and stirred at 80°C for 8 hours. After cooling to room temperature, 0.38g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride dichloromethane adduct, 7.99g of 9-phenylcarbazole-3-boronic acid, and 2.40g of potassium carbonate were added, and the mixture was stirred at 80°C for another 10 hours. After that, it was cooled to room temperature, 0.38 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride dichloromethane adduct and 2.40 g of potassium carbonate were added, and the mixture was stirred at 80°C for another 8 hours. 200 ml of toluene was added, and the mixture was stirred at 100°C for 1 hour. The mixture was filtered, and the filtrate was dried. The solid obtained was subjected to silica gel column chromatography using chloroform / hexane = 1:2 (v / v) as a developing solvent. The fourth fraction was collected and dried under reduced pressure at 50°C for 5 hours, to obtain 10.5 g (yield 57%) of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9-phenyl-9H-carbazol-3-yl)-10,12-dihydroindeno[2,1-b]carbazole as a white solid.

[0090] The structure of the resulting white powder was identified by NMR. 1 The following 34 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.68(1H), 8.53(2H), 8.27(1H), 7.99(1H), 7.83-7.65(8H), 7.55-7.33(14H), 7.19-7.03(3H), 6.80-6.78(3H), 6.64(1H)

[0091] Example 8 <Synthesis of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9-phenyl-9H-carbazol-4'-yl)-10,12-dihydroindeno[2,1-b]carbazole; Compound (1-40)> 22.4g of 7-bromo-12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole, 5.54g of 9-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-9H-carbazole, 5.98g of potassium carbonate, 50ml of toluene, 4.0ml of ethanol, and 4.5ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.20g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride dichloromethane adduct was added, heated, and stirred at 80°C for 7 hours. The mixture was cooled to room temperature, 200ml of toluene was added, and the mixture was stirred at 100°C for 1 hour. Filtration was performed, and 40g of silica gel was added to the obtained filtrate, and the mixture was stirred at room temperature for 1 hour. The silica gel was removed by filtration, and the filtrate was dried. Thermal recrystallization was performed twice using 50 ml of toluene to obtain a white solid. The obtained solid was dried under reduced pressure at 50°C for 5 hours to obtain 8.00 g (yield 48%) of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9-phenyl-9H-carbazol-4'-yl)-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0092] The structure of the resulting white powder was identified by NMR. 1 The following 34 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.66(1H), 8.56(1H), 8.18(2H), 7.98-7.97(3H), 7.82(2H), 7.70-7.68(3H), 7.52-7.03(18H), 6.79-6.78(3H), 6.65(1H)

[0093] Example 9 <Synthesis of 5,7-dihydro-5,7,7-triphenyl-2-(6',9'-diphenyl-9H-carbazol-3-yl)indeno[2,1-b]carbazole; Compound (1-69)> 19.0g of 2-bromo-5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole, 18.1g of 6,9-diphenylcarbazole-3-boronic acid, 7.00g of potassium carbonate, 150ml of toluene, 24ml of ethanol, and 25ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.78g of tetrakistriphenylphosphine palladium was added, heated, and stirred at 80°C for 7 hours. The mixture was cooled to room temperature, and 3.5g of potassium carbonate and 78mg of tetrakistriphenylphosphine palladium were added, and stirred at 80°C for 8 hours. After cooling to room temperature, 300mg of 6,9-diphenylcarbazole-3-boronic acid was added, and stirred at 80°C for 3 hours. After cooling to room temperature, 78mg of tetrakistriphenylphosphine palladium was added, and stirred at 80°C for 8 hours. 200ml of toluene was added, and the mixture was stirred at 60°C for 30 minutes. Filtration was performed, and 25 g of silica gel and 25 g of activated clay were added to the filtrate and stirred at 80°C for 1 hour. Filtration was performed, and the obtained filtrate was concentrated to obtain a white solid. The white solid was recrystallized under the conditions of THF / toluene = 1:3 (v / v). The obtained white solid was dissolved in o-dichlorobenzene, 25 g of silica gel was added, and the mixture was stirred at 160°C for 1 hour and filtered. After the filtrate was allowed to cool to room temperature, 90 mL of methanol was added to the obtained filtrate, and the precipitated white solid was filtered. By drying under reduced pressure at 60°C for 22 hours, 15.2 g of the desired 5,7-dihydro-5,7,7-triphenyl-2-(6',9'-diphenyl-9H-carbazol-3-yl)indeno[2,1-b]carbazole was obtained as a white powder (yield 56%).

[0094] The structure of the resulting white powder was identified by NMR. 1 The following 40 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.59(1H), 8.54(2H), 8.48(1H), 7.92(1H), 7.81(1H), 7.78-7.76(3H), 7.71-7.64(5H), 7.59-7.34(16H), 7.25-7.18(10H)

[0095] Example 10 <Synthesis of 5,7-dihydro-5,7,7-triphenyl-2-(9'-biphenyl-9'H-carbazol-3'-yl)indeno[2,1-b]carbazole; Compound (1-70)> 19.0g of 2-bromo-5,7-dihydro-5,7,7-triphenylindeno[2,1-b]carbazole, 18.1g of 9-biphenylcarbazole-3-boronic acid, 7.00g of potassium carbonate, 150ml of toluene, 24ml of ethanol, and 25ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.78g of tetrakistriphenylphosphine palladium was added, heated, and stirred at 80°C for 6 hours. The mixture was cooled to room temperature, 78mg of tetrakistriphenylphosphine palladium was added, and stirred at 80°C for 6 hours. Filtration was performed, and the filtrate was washed twice with water and once with saturated saline. The organic layer was dried over sodium sulfate. 25g of silica gel was added to the dried organic layer, and stirred at 60°C for 1 hour. Filtration was performed, and the obtained filtrate was concentrated to obtain a white solid. The obtained white solid was dissolved in o-dichlorobenzene, 25 g of silica gel was added, and the mixture was stirred at 160°C for 1 hour and filtered. After cooling to room temperature, 30 mL of methanol was added to the obtained filtrate, and the precipitated white solid was filtered. The obtained solid was dissolved in 60 ml of toluene and thermally recrystallized to obtain a white powder. The obtained white powder was dried under reduced pressure at 60°C for 22 hours to obtain the desired 5,7-dihydro-5,7,7-triphenyl-2-(9'-biphenyl-9H-carbazol-3'-yl)indeno[2,1-b]carbazole as a white powder, 15.9 g (yield 59%).

[0096] The structure of the resulting white powder was identified by NMR. 1 The following 40 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.58(1H), 8.51(2H), 8.26(1H), 7.91(1H), 7.85-7.80(3H), 7.77-7.68(5H), 7.59-7.32(17H), 7.25-7.18(10H)

[0097] Example 11 <Synthesis of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(6',9'-diphenyl-9'H-carbazol-3'-yl)-10,12-dihydroindeno[2,1-b]carbazole; Compound (1-71)> 5.00g of 7-bromo-12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole, 4.77g of 6,9-phenylcarbazole-3-boronic acid, 1.85g of potassium carbonate, 40ml of toluene, 6ml of ethanol, and 7ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.21g of tetrakistriphenylphosphine palladium was added and stirred at 80°C for 10 hours. The mixture was cooled to room temperature, 1.9g of potassium carbonate and 210mg of tetrakistriphenylphosphine palladium were added, and the mixture was stirred at 80°C for 7 hours. 100ml of toluene was added and the mixture was stirred at 100°C for 1 hour. Filtration was performed, and 35g of silica gel was added to the filtrate, and the mixture was stirred at room temperature for 1 hour. Filtration was performed, and the obtained filtrate was concentrated to obtain a white solid. The white solid was recrystallized from THF / methanol = 1:3 (v / v) and then recrystallized from toluene. The resulting white solid was dried under reduced pressure at 60 °C for 22 hours to obtain 2.16 g (yield 30%) of the desired 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(6',9'-diphenyl-9'H-carbazol-3'-yl)-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0098] The structure of the resulting white powder was identified by NMR. 1 The following 38 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.68(1H), 8.55(2H), 8.48(1H), 7.97(1H), 7.83-7.67(6H), 7.63(4H), 7.5 5-7.33(15H), 7.25(1H), 7.15(1H), 7.08(1H), 7.03(1H), 6.80-6.78(3H), 6.64(1H)

[0099] Example 12 <Synthesis of 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9'-biphenyl-9'H-carbazol-3'-yl)-10,12-dihydroindeno[2,1-b]carbazole; Compound (1-72)> 5.00g of 7-bromo-12,12'-spirobi[9H-fluorene]-10-phenyl-10,12-dihydroindeno[2,1-b]carbazole, 4.77g of 9-biphenylcarbazole-3-boronic acid, 1.9g of potassium carbonate, 40ml of toluene, 6ml of ethanol, and 7ml of water were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. 0.21g of tetrakistriphenylphosphine palladium was added, heated, and stirred at 80°C for 8 hours. After cooling to room temperature, 0.21g of tetrakistriphenylphosphine palladium and 1.9g of potassium carbonate were added, and stirred at 80°C for 9 hours. After cooling to room temperature, 100ml of methanol was added, and the precipitated solid was collected by filtration. The obtained solid (6.8 g), 9-biphenylcarbazole-3-boronic acid (2.5 g), potassium carbonate (1.9 g), toluene (40 ml), ethanol (6 ml), and water (7 ml) were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. Tetrakistriphenylphosphinepalladium (0.21 g) was added, heated, and stirred at 80°C for 6 hours. Toluene (100 ml) was added, and the mixture was stirred at 100°C for 1 hour. Filtration was performed, and the obtained filtrate was concentrated. Silica gel (14 g) was added to the filtrate, and the mixture was stirred at 80°C for 1 hour. Filtration was performed, and the filtrate was dried. The obtained solid was washed with hexane (100 ml) and methanol (100 ml). The washed solid was subjected to silica gel column chromatography using toluene / hexane = 1:3 (v / v) as a developing solvent. The fifth fraction was collected, and the white solid collected was washed with hexane. The resulting white powder was dried under reduced pressure at 50°C for 5 hours to obtain 3.6 g (yield 50%) of the desired 12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9'-biphenyl-9'H-carbazol-3'-yl)-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0100] The structure of the resulting white powder was identified by NMR. 1 The following 38 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.68(1H), 8.56(1H), 8.28(1H), 7.98(1H), 7.91-7.81(6H), 7.73-7.70( 5H), 7.60(1H), 7.55-7.33(15H), 7.10(2H), 7.05(1H), 6.81-6.78(3H), 6.64(1H)

[0101] (Example 13) <Synthesis of 12,12'-spirobi[9H-fluorene]-10-biphenyl-4-yl-7-(9'H-carbazol-9'-yl)-10,12-dihydroindeno[2,1-b]carbazole; Compound (1-73)> 7-Bromo-12,12'-spirobi[9H-fluorene]-10-biphenyl-4-yl-10,12-dihydroindeno[2,1-b]carbazole 7.00g, carbazole 2.21g, cesium carbonate 5.4g, and toluene 150ml were added to a nitrogen-substituted reaction vessel, and nitrogen gas was passed through for 30 minutes. Palladium acetate 0.12g, tri-t-butylphosphine 50wt% toluene solution 0.44g were added, and the mixture was heated and refluxed for 6 hours. The mixture was then cooled to room temperature, and palladium acetate 0.12g, tri-t-butylphosphine 50wt% toluene solution 0.44g, and cesium carbonate 5.4g were added, and the mixture was refluxed for 9 hours. After cooling to room temperature, 0.12g of palladium acetate, 0.44g of a 50wt% toluene solution of tri-t-butylphosphine, 5.4g of cesium carbonate, and 2.21g of carbazole were added and refluxed for 8 hours. 200ml of toluene was added and stirred at 100°C for 1 hour. Filtration was performed and the filtrate was concentrated. The solid obtained was subjected to silica gel column chromatography using chloroform / hexane = 1:3 (v / v) as the developing solvent. The fifth fraction was collected and a white solid was recovered. The solid obtained was recrystallized three times under the conditions of chloroform / methanol = 1:3 (v / v), tetrahydrofuran / methanol = 1:3 (v / v), and toluene. The resulting white powder was dried under reduced pressure at 50°C for 5 hours to obtain 0.8 g (yield 10%) of the desired <12,12'-spirobi[9H-fluorene]-10-phenyl-7-(9'H-carbazol-9'-yl)-10,12-dihydroindeno[2,1-b]carbazole as a white powder.

[0102] The structure of the resulting white powder was identified by NMR. 1 The following 34 hydrogen signals were detected by H-NMR (CDCl3). δ(ppm)=8.55(1H), 8.37(1H), 8.20(2H), 7.90(1H), 7.81(2H), 7.67(2H), 7.60(2H), 7 .56-7.41(10H), 7.37-7.15(7H), 7.10(1H), 7.03(1H), 6.86(1H), 6.78(2H), 6.64(1H)

[0103] Example 14 The glass transition points of the compounds having an indenocarbazole ring structure synthesized in Examples 1 to 13 were measured using a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). The results are shown in Table 1.

[0104] [Table 1]

[0105] The compounds synthesized in Examples 1 to 13 have glass transition points of 100° C. or higher, which indicates that they are stable in the thin film state.

[0106] Example 15 Using the compounds synthesized in Examples 1 to 13, a 100 nm thick film was formed by vapor deposition on an ITO substrate, and the work function was measured using an ionization potential measuring device (Sumitomo Heavy Industries, Ltd., PYS-202). The results are shown in Table 2.

[0107] [Table 2]

[0108] The compounds synthesized in Examples 1 to 13 show a suitable energy level compared with the work function of 5.3 to 6.0 eV of hole transport materials such as indolocarbazole, which is considered to be a suitable material, and are therefore found to have good hole transport capabilities.

[0109] (Example 16) <Mobility measurement> A PEDOT / PSS film was formed as a hole injection layer to a thickness of 50 nm by a coating method on a glass substrate on which an ITO electrode had previously been formed as a transparent anode. Subsequently, compound (1-20) of Example 6, compound (1-37) of Example 7, compound (1-69) of Example 9, and compound (1-73) of Example 13 were evaporated to a thickness of 50 nm, and further, Al was evaporated to a thickness of 100 nm as a cathode to form a laminated film, thereby producing a device. A mobility measurement element was prepared by annealing it on a hot plate at 180°C for 3 hours and an unannealed mobility measurement element was prepared. A voltage of -6V to 15V was applied to each mobility measurement element, and the mobility was measured by fitting the SCLC (space charge limited current) equation to the current-voltage curve in which a current flowed with a positive bias.

[0110] Comparative Example 1 For comparison, elements were prepared using Tris-PCz instead of the compound (1-20) of Example 6, the compound (1-37) of Example 7, the compound (1-69) of Example 9, and the compound (1-73) of Example 13, and the mobility was measured in the same manner. The results are shown in Table 3.

[0111] [ka]

[0112] [Table 3]

[0113] The devices using the compound (1-20) of Example 6, the compound (1-37) of Example 7, the compound (1-69) of Example 9, and the compound (1-73) of Example 13 were stable even after heating at 180° C. for 3 hours, and the mobility was measurable. However, leakage was observed in the device using Tris-PCz, which is widely used as an organic semiconductor, as shown in FIG. 3, and the mobility could not be calculated.

[0114] As is clear from the above results, the compound having an indenocarbazole ring structure represented by the above general formula (1) used in the present invention has a HOMO value, high heat resistance, and sufficiently high mobility required for the blocking layer of a photoelectric conversion element.

[0115] (Example 17) <Measurement of electrical characteristics in photoelectric conversion elements> As shown in FIG. 1, the photoelectric conversion element was prepared by depositing a first buffer layer 2, a photoelectric conversion layer 3, and a second electrode as a cathode 5 in this order on a glass substrate on which an ITO electrode had previously been formed as an anode 1.

[0116] Specifically, a glass substrate on which an ITO electrode was formed as the anode 1 was ultrasonically cleaned in isopropyl alcohol for 20 minutes, and then dried overnight in a clean oven heated to 100°C. After that, UV ozone treatment was performed for 5 minutes, and the glass substrate with the ITO electrode was mounted in a vacuum deposition machine and the pressure was reduced to 0.001 Pa or less. Next, the compound (1-20) of Example 6 was evaporated on the anode 1 as the first buffer layer 2 to a thickness of 15 nm. On this first buffer layer 2, SubPC and C60 having the following structure were co-evaporated at an evaporation rate such that the evaporation rate ratio was SubPC:C60=1:1, and a photoelectric conversion layer 3 was formed to a thickness of 100 nm. On this photoelectric conversion layer 3, gold was formed as the cathode 5 to a thickness of 100 nm. The electrical characteristics (light current, dark current) of the fabricated photoelectric conversion element were evaluated. The measurement results are summarized in Table 4.

[0117] [ka]

[0118] (Examples 18 to 20) Photoelectric conversion elements were prepared in the same manner as in Example 17, except that the compounds of Examples 7, 9, and 13 were used instead of the compound (1-20) of Example 6 as the material for the first buffer layer 2. The measurement results are summarized in Table 4.

[0119] Comparative Example 2 For comparison, SubPC and C60 were co-deposited on the anode 1 at a deposition rate ratio of SubPC:C60=1:1 to form a photoelectric conversion layer 3 with a film thickness of 100 nm. A photoelectric conversion element was fabricated in the same manner as above, and its electrical characteristics were evaluated. The measurement results are summarized in Table 4.

[0120] Comparative Example 3 For comparison, a photoelectric conversion element was prepared in the same manner as in Example 17, except that HTM-1 (see, for example, Patent Document 6) having the following structural formula was used as the material for the first buffer layer 2 instead of the compound (1-20) obtained in Example 6, and the electrical characteristics were evaluated. The measurement results are summarized in Table 4.

[0121] [ka]

[0122] The electrical characteristics (bright current, dark current) of the photoelectric conversion elements produced in Examples 17 to 20 and Comparative Examples 2 to 3 were measured using a source meter (Keithley, 2635B). The measurement results are summarized in Table 4. For the bright current, specifically, the photoelectric conversion element was irradiated with light from an LED light source via a green filter (HOYA, G533), and the current value was measured at a reverse bias voltage (-1 to -5 V) applied between the electrodes. For the dark current, specifically, the amount of light irradiated to the photoelectric conversion element was set to zero, and the current value was measured at a reverse bias voltage (-1 to -5 V) applied between the electrodes.

[0123] [Table 4]

[0124] As shown in Table 4, the dark current at each applied bias is significantly lower in the devices of Examples 17 to 20 than in the devices of Comparative Examples 2 to 3. In addition, the light / dark ratio when a bias of -3 V is applied is also significantly improved in the devices of Examples 17 to 20 than in the devices of Comparative Examples 2 to 3. This shows that the high electron blocking property and good hole transport property of the compound having an indenocarbazole ring structure can significantly improve the dark current characteristics of the photoelectric conversion element. [Industrial Applicability]

[0125] According to the present invention, it is possible to provide a photoelectric conversion element, particularly an imaging element, having an organic thin film that has high heat resistance and good charge mobility.

Claims

[Claim 1] An imaging element comprising a photoelectric conversion element in which a first electrode, a first buffer layer, a photoelectric conversion layer, and a second electrode are stacked in this order, the first buffer layer being an organic thin film containing a compound having an indenocarbazole ring structure represented by the following general formula (2) or (3), and the photoelectric conversion layer is a mixed film of a p-type organic semiconductor and an n-type organic semiconductor. 【Chemistry 1】 (In the formula, Ar １ and Ar ４ may be the same or different and represent a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. R １ ~R ９ , R １２ ~R １８ represents a hydrogen atom. R １０ and R １１ may be the same or different, represent a substituted or unsubstituted aromatic hydrocarbon group, and may be bonded to each other via a single bond to form a ring. 【Chemistry 2】 (In the formula, Ar １ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. R １ ~R ９ , R １９ ~R ２６ represents a hydrogen atom. R １０ and R １１ may be the same or different, represent a substituted or unsubstituted aromatic hydrocarbon group, and may be bonded to each other via a single bond to form a ring.

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