JP2022115832A - Photoelectric conversion element and imaging element - Google Patents

Abstract

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

Description

TECHNICAL FIELD The present invention relates to a photoelectric conversion device, and more particularly to a photoelectric conversion device including an organic thin film containing a compound that satisfies specific physical property values, and an imaging device including the photoelectric conversion device.

Photoelectric conversion elements are widely used, for example, in solar cells and optical sensors. Among them, image sensors, which are imaging elements, are beginning to be used not only for television cameras and smartphone cameras, but also for driving support systems. Both markets are expanding.

Until now, inorganic materials such as Si films and Se films have been used as materials for image sensors, and there are two main imaging methods: a three-plate type that uses a prism to separate colors, and a single-plate type that uses color filters. rice field. However, although the three-plate type has a high utilization rate of light, it is difficult to miniaturize because it uses a prism. , resolution, and light utilization rate were poor (Non-Patent Document 1).

Organic materials absorb light of specific wavelengths better than inorganic materials, so by combining materials that match each wavelength, we constructed an image sensor that can efficiently use light for each of the three primary colors without using a prism. can do. Therefore, light utilization efficiency is high, and it is possible to manufacture a small-sized imaging device. In addition, it is possible to add values such as flexibility and large area by coating in the production process, which cannot be achieved with inorganic materials (Non-Patent Document 2).

For this reason, photoelectric conversion elements using organic substances are expected to be developed into next-generation imaging elements, and several reports have been made. For example, an example of using a quinacridone or quinazoline derivative in a photoelectric conversion device (Patent Document 1), an example of using a benzothienobenzothiophene derivative in a photoelectric conversion device (Patent Document 2), an example of using indolocarbazole in a photoelectric conversion device ( Patent Document 3) and the like. It is generally believed that the performance of an organic image pickup device is improved by aiming at high contrast and power saving, and aiming at reduction of dark current. In order to reduce dark current, a method of inserting a hole blocking layer or an electron blocking layer between the photoelectric conversion portion and the electrode portion may be used.

A hole-blocking layer and an electron-blocking layer are methods commonly used in the field of organic electronics. The required charge moves rapidly while controlling the back migration of holes or electrons. Patent Document 4 discloses that a compound having a highest occupied molecular orbital (HOMO) level of −4.7 to −5.8 eV as an electron blocking material is effective in improving the efficiency of charge transfer to an electrode. is suggesting.

A photoelectric conversion layer is required to have high sensitivity, and the following methods are available for increasing the sensitivity.
・Since photoelectric conversion occurs at the interface between a p-type semiconductor and an n-type semiconductor, the active layer has a bulk heterostructure to increase the area of the interface.
・In order to efficiently separate holes and electrons from excitons generated by light absorption, a compound with strong acceptor properties is used in the active layer.

In a device having an electron-blocking layer, when the active layer has a bulk heterostructure, an interface occurs between the electron-blocking layer and the n-type semiconductor. When a compound with a strong acceptor property is used as an n-type semiconductor, the highest occupied molecular orbital (HOMO ) to the lowest unoccupied molecular orbital (LUMO) of a compound having a strong acceptor property (fullerene derivative in Patent Document 5), resulting in poor dark current characteristics. In the HOMO level electron blocking layer proposed in Patent Document 4, when a material such as a fullerene derivative that has a strong acceptor property and a deep LUMO level is used for the active layer, the HOMO level and the activity of the electron blocking layer are different. The energy level becomes close to the LUMO level of the n-type semiconductor in the layer, electrons move from the n-type semiconductor material in the active layer to the electron blocking layer, and dark current characteristics deteriorate.

In order to prevent the electron transfer, the HOMO level of the material used for the electron blocking layer must be deepened.

Further, when the photoelectric conversion element is used as an optical sensor or an organic imaging element, a response speed is also required. In order to increase the response speed, it is necessary to increase the mobility of the materials used in the device. was not considered.

Japanese Patent No. 4945146 Japanese Patent Application Laid-Open No. 2018-170487 Japanese Patent Application Laid-Open No. 2018-085427 Japanese Patent Application Laid-Open No. 2011-187937 Japanese Patent No. 5624987 WO2017/159684

ITE Media Association Journal, 60, 3, 291 (2006) Adv. Mater. 28, 4766 (2016)

The present invention has been made in view of the above-mentioned current situation, and provides an organic thin film for use in a photoelectric conversion device by utilizing a compound having a deep HOMO level, excellent heat resistance, and hole transport properties. , an object of the present invention is to provide various photoelectric conversion elements, particularly imaging elements, to which the organic thin film is applied, and optical sensors using the same.

The properties of an electron blocking material suitable for a photoelectric conversion device include (1) excellent thermal stability, (2) deep HOMO level, (3) possessing hole transport ability, and (4) ) It is possible to form a film by a vacuum vapor deposition method.

Therefore, in order to achieve the above object, the present inventors conducted intensive research and found a compound having the following characteristics for forming an organic thin film having the above characteristics, and a stable thin film can be formed by a vacuum deposition method. In addition, the inventors have realized the formation of an organic thin film which has a high glass transition temperature and can suppress electron transfer from an n-type semiconductor, thereby completing the present invention.
(1) having a glass transition temperature (Tg) of 110° C. or higher;
(2) the highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV;
(3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is
1.0×10 ⁻⁷ <μh<1.0×10 ⁻² (cm ² /Vs).

That is, the present invention is an organic thin film used for a photoelectric conversion device that satisfies the following physical properties and composition.
1) An organic photoelectric conversion device comprising a conductive thin film, an organic photoelectric conversion layer, a blocking layer and a transparent conductive thin film, wherein the blocking layer contains a blocking material having the following properties:
(1) a glass transition temperature (Tg) of 110° C. or higher;
(2) the highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV,
(3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is
1.0×10 ⁻⁷ <μh<1.0×10 ⁻² (cm ² /Vs).

The organic thin film having a deep HOMO level and hole transporting ability of the present invention can be applied to various photoelectric conversion elements. Thereby, it is possible to provide a photoelectric conversion device, particularly an imaging device, and an optical sensor using the same, which have good dark current characteristics.

FIG. 1 shows one structural example of the photoelectric conversion element of the present invention. FIG. 2 shows the structures of compounds (1-1) to (1-15) as examples of compounds represented by general formula (1). FIG. 3 shows the structures of compounds (1-16) to (1-30) as examples of compounds represented by general formula (1). FIG. 4 shows the structures of compounds (1-31) to (1-44) as examples of compounds represented by general formula (1). FIG. 5 shows the structures of compounds (1-45) to (1-56) as examples of compounds represented by general formula (1). FIG. 6 shows the structures of compounds (1-57) to (1-66) as examples of compounds represented by general formula (1). FIG. 7 shows the structures of compounds (1-67) to (1-78) as examples of compounds represented by general formula (1). FIG. 8 shows the structures of compounds (1-79) to (1-89) as examples of compounds represented by general formula (1). FIG. 9 shows the structures of compounds (1-90) to (1-103) as examples of compounds represented by general formula (1). FIG. 10 shows the structures of compounds (1-104) to (1-122) as examples of compounds represented by general formula (1).

Embodiments of the present invention are described in detail below.

In the present specification, "to" is a term representing a range, for example, the description "5 to 10" means "5 or more and 10 or less", and the numerical value itself described before and after "to" represents an inclusive range.

<Photoelectric conversion element>
A photoelectric conversion element is an element capable of converting light energy into electrical energy, and includes, for example, a conductive thin film, an organic photoelectric conversion layer, a blocking layer and a transparent conductive thin film. The blocking layer may be a hole blocking layer or an electron blocking layer, or may include both of these blocking layers. The photoelectric conversion element preferably includes an electron blocking layer as the blocking layer.

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

<<Blocking Layer>>
The blocking layer contains an electron blocking material having at least the following properties.
(1) a glass transition temperature (Tg) of 110° C. or higher;
(2) the highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV,
(3) The hole mobility (μh) at an electric field strength of 0.25 MV / cm is
1.0×10 ⁻⁷ <μh<1.0×10 ⁻² (cm ² /Vs).

<<<Electron blocking material>>>
The electron blocking material is an organic compound that forms an organic film, and preferably has a glass transition temperature of 110° C. or higher, more preferably 120° C. or higher. As a result, application to manufacturing processes having a heating step and improvement in preservability can be achieved. In addition, in the organic film formed from the organic compound of the electron blocking material, the HOMO level is preferably a deep energy level of -5.8 to -7.0 eV, and more preferably -5.8 to -6.5 eV. Preferably. Thereby, it is possible to suppress the transfer of charges from the n-type semiconductor included in the photoelectric conversion layer of the bulk heterostructure to the electron blocking layer. Also, the leak current of the photoelectric conversion element can be reduced. Furthermore, in order to efficiently transport holes generated in the photoelectric conversion layer, the hole mobility (μh) at an electric field strength of 0.25 MV/cm of the electron blocking material should be 1.0×10 ⁻⁶ <μh<1.0×10 ⁻³ (cm ² /Vs) is preferred.

Although the electron blocking material is not particularly limited, it is preferably a compound containing two or more condensed heterocyclic groups composed of a five-membered heterocyclic ring. More preferably, it is a compound represented by the following general formula (1). Specific examples of preferable compounds represented by the general formula (1) are shown in FIGS. 2 to 10, but the present invention is not limited to these compounds.

(In the formula, Ar ₁ and Ar ₂ may be the same or different, and may be substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups, or substituted or unsubstituted condensed poly represents a ring aromatic group,
L ₁ represents 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 triarylamine ,
a represents an integer of 2 to 4,
b represents an integer of 0 to 2; )

"Aromatic Specific hydrocarbon groups, "aromatic heterocyclic groups" or "condensed polycyclic aromatic groups" include phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, thienyl group, selenenyl group, pyrrolyl group, quinolyl group, isoquinolyl group , benzofuranyl group, benzothienyl group, benzoselenenyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, benzoselenazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzoselenenyl group , dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group, acridinyl group and carbolinyl group. Further, it can be selected from aryl groups having 6 to 30 carbon atoms and heteroaryl groups having 2 to 30 carbon atoms.

As the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group" or "substituted triphenylamines" in general formula (1), Specifically, a deuterium atom, a cyano group, a nitro group; a fluorine atom, a chlorine atom, a bromine atom, a halogen atom such as an iodine atom; a trimethylsilyl group, a silyl group such as a triphenylsilyl group; a methyl group, an ethyl group, a propyl group linear or branched alkyl group having 1 to 6 carbon atoms such as; linear or branched alkyloxy group having 1 to 6 carbon atoms such as methyloxy group, ethyloxy group, propyloxy group; vinyl aryloxy groups such as phenyloxy group and tolyloxy group; arylalkyloxy groups such as benzyloxy group and phenethyloxy group; phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, Aromatic hydrocarbon groups or condensed polycyclic aromatic groups such as phenanthrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group; pyridyl group, furyl group, thienyl group, pyrrolyl 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 and aromatic heterocyclic groups such as carbolinyl groups, and these substituents may be further substituted with the substituents exemplified above.

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

In general formula (1), Ar ₁ may be a structure selected from the group consisting of general formulas (2-a) to (2-t) below.

(In the formula,
X represents S, O, Se, C—R ₁ R ₂ , Si—R ₁ R ₂ , or N—Ar ₃ ;
Y represents S, O, Se, Si—R ₁ R ₂ or N—Ar ₃ ;
Z represents N or C—R ₃ ;
R ₁ to R ₃ may be the same or different, and may be a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, or an optionally substituted straight chain having 1 to 8 carbon atoms. or a branched alkyl group, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, or an optionally substituted linear or branched 2 to 6 carbon atom alkenyl group, optionally substituted C1-8 linear or branched alkyloxy group, optionally substituted C2-10 cycloalkyloxy group , a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,
Adjacent groups of R ₁ to R ₃ may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring,
Ar ₃ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group;
Dashed lines indicate binding sites. )

In the general formulas (2-a) to (2-t), "a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent", "having a substituent ``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'' The linear or branched alkyl group of ", "C5-C10 cycloalkyl group", or "C2-C6 linear or branched alkenyl group" specifically , methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, cyclopentyl group, cyclohexyl group, Examples include 1-adamantyl group, 2-adamantyl group, vinyl group, allyl group, isopropenyl group and 2-butenyl group.

In the general formulas (2-a) to (2-t), "an optionally substituted C 1 to 6 linear or branched alkyloxy group" or "having a substituent "A linear or branched alkyloxy group having 1 to 6 carbon atoms" or "a cycloalkyloxy group having 5 to 10 carbon atoms" in "a cycloalkyloxy group having 5 to 10 carbon atoms" which may be Specific examples include methyloxy group, ethyloxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group, cyclopentyloxy group, A cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a 1-adamantyloxy group, a 2-adamantyloxy group and the like can be mentioned.

Specific examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in general formulas (2-a) to (2-t) include a phenyloxy group, a biphenylyloxy group, and terphenylyl Examples include aryloxy groups having 6 to 30 carbon atoms such as oxy, naphthyloxy, anthracenyloxy and phenanthrenyloxy groups.

"Substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group", or "substituted or unsubstituted condensed poly Specific examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "aromatic ring group" are also the same as the specific examples given in the general formula (1).

"Substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "substituted methylene 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", " optionally substituted linear or branched C 2-6 alkenyl group", "optionally substituted C 1-6 linear or branched Specific examples of the "substituent" in the "alkyloxy group of" or "optionally substituted cycloalkyloxy group having 5 to 10 carbon atoms" are also specific examples given in general formula (1) are the same.

From the viewpoint of heat resistance, R ₁ and R ₂ in general formulas (2-a) to (2-t) are preferably methyl groups or phenyl groups.

R ₃ in the general formulas (2-a) to (2-t) is preferably hydrogen or a phenyl group because of ease of synthesis.

Ar ₃ in the general formulas (2-a) to (2-t) is preferably a substituted or unsubstituted aromatic hydrocarbon group, particularly preferably a phenyl group, because of ease of synthesis.

In the general formula (1), Ar ₂ may be a structure selected from the group consisting of the following general formulas (3-a) to (3-v).

(In the formula,
R ₄ has the same definition as R ₁ to R ₃ in the general formulas (2-a) to (2-t);
The dashed line indicates the binding site,
d represents an integer of 0 to 4,
e represents an integer of 0 to 3,
f represents an integer of 0-2. )

"Substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group", or "substituted or unsubstituted condensed poly Specific examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "aromatic ring group" are also listed in general formulas (2-a) to (2-t). is the same as the specific example.

In the general formulas (3-a) to (3-v), "optionally substituted C 1 to 6 linear or branched alkyl group", "having a substituent ``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'' Specific examples of the linear or branched alkyl group of the general formula The specific examples given in (2-a) to (2-t) are the same.

In the general formulas (3-a) to (3-v), "an optionally substituted C 1 to 6 linear or branched alkyloxy group" or "having a substituent "A linear or branched alkyloxy group having 1 to 6 carbon atoms" or "a cycloalkyloxy group having 5 to 10 carbon atoms" in "a cycloalkyloxy group having 5 to 10 carbon atoms" which may be are the same as the specific examples given in general formulas (2-a) to (2-t).

Specific examples of the "aryloxy group" in the "substituted or unsubstituted aryloxy group" in general formulas (3-a) to (3-v) are listed in general formulas (2-a) to (2-t). It is the same as the specific example given.

"Substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group", "substituted condensed polycyclic aromatic group", "substituted methylene 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", " optionally substituted linear or branched C 2-6 alkenyl group", "optionally substituted C 1-6 linear or branched Specific examples of the “substituent” in the “alkyloxy group of” or “cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent” are also represented by general formulas (2-a) to (2-t ) are the same as the specific examples given in ).

From the viewpoint of heat resistance, R ₄ in general formulas (3-a) to (3-v) above is preferably a hydrogen atom or a phenyl group.

From the viewpoint of hole transport properties, Ar ₁ in general formula (1) is a carbazolyl group, carbolinyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, benzoxazolyl group, indenoindolyl group, benzofurano A carbazolyl group or an indenocarbazolyl group is preferable, and a carbazolyl group or a carbolinyl group is more preferable.

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

From the viewpoint of the HOMO level, Ar ₂ in general formula (1) is preferably a pyridyl group, a pyrimidinyl group, a triazinyl group, or a benzonitrile group.

From the viewpoint of hole mobility, a in the general formula (1) is preferably an integer of 2 or 3, and b is preferably an integer of 0 or 1.

Purification of the compound represented by the general formula (1) can be carried out by purification by column chromatography, adsorption purification by silica gel, activated carbon, activated clay or the like, recrystallization or crystallization with a solvent, or the like. Identification of compounds can be performed by NMR analysis. As physical properties, it is preferable to measure the glass transition point (Tg) and the HOMO level. The glass transition point (Tg) is an index of the stability of the thin film state, and the HOMO level is an index of the hole transportability. It is also preferable to evaluate the hole mobility and the light/dark current of the photoelectric conversion element as physical property values.

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

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

The hole mobility was measured by forming a film of an organic compound to be measured with a film thickness of 3 to 4 μm on a glass substrate with ITO, and using a transient photocurrent measurement device (manufactured by Optel, time-of-flight measurement device TOF-401). can be evaluated. In detail, it can be evaluated according to the method described in the examples described later.

The light-dark current of the photoelectric conversion element can be evaluated using a spectral sensitivity measuring device (SM-250A, manufactured by Spectroscopy Co., Ltd.). In detail, it can be evaluated according to the method described in the examples described later.

The compound represented by formula (1) can be used to form an organic thin film by a known method such as vapor deposition, spin coating and inkjet. In addition, although the compound represented by the general formula (1) may be formed into a film by itself, it is also possible to form a film by mixing plural kinds of compounds. Furthermore, it can be mixed with other compounds to form a film as long as the effect of the present invention is not impaired.

An organic thin film containing a compound represented by general formula (1) is suitable for use in a photoelectric conversion device, particularly an imaging device. The structure of the photoelectric conversion element includes, for example, a first electrode (anode), an electron blocking layer, a photoelectric conversion layer, and a second electrode (cathode) in this order, and the electron blocking layer contains an organic compound represented by general formula (1). A configuration that is a thin film can be mentioned. Additional layers can be added to such a multi-layer structure, for example, the structure can have a first electrode, an electron blocking layer, a photoelectric conversion layer, a hole blocking layer, and a second electrode in that order. Moreover, it can also be used for a photoelectric conversion layer.

<<Photoelectric conversion layer>>
The photoelectric conversion layer may be made of an organic material or an inorganic material, as long as it can generate signal charges according to the amount of received light. When the photoelectric conversion layer is made of an organic material, the organic semiconductor film may be a single layer or a plurality of layers. and n-type organic semiconductor mixed films (bulk heterostructures) are used. In the case of a plurality of layers, it is a structure in which two or more of a p-type organic semiconductor film, an n-type organic semiconductor film, or a p-type organic semiconductor and n-type organic semiconductor mixed film are laminated, and a buffer is provided between the layers. It is also possible to insert layers.

The p-type semiconductor used in the photoelectric conversion layer is a donor organic semiconductor, and is mainly represented by a hole-transporting organic compound, and is a compound that easily donates electrons.
Examples of p-type semiconductors include, but are not limited to, 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 with heterocyclic compounds as ligands, benzothiophene derivatives, dinaphthothienothiophene derivatives, dianthracenothienothiophene derivatives, benzobisbenzothiophene derivatives, thienobisbenzothiophene derivatives, dibenzothienobisbenzothiophene derivatives, dithieno Thienoacene-based materials and triarylamine compounds represented by benzodithiophene derivatives, dibenzothienodithiophene derivatives, benzodithiophene derivatives, naphthodithiophene derivatives, anthracenodithiophene derivatives, tetracenodithiophene derivatives, and pentacenodithiophene derivatives , amine derivatives such as carbazole compounds, and indenocarbazole derivatives.

The n-type organic semiconductor used in the photoelectric conversion layer is an acceptor organic semiconductor, which is mainly represented by an electron-transporting organic compound, and refers to an organic compound that easily accepts electrons. More specifically, it refers to the organic compound with the larger electron affinity when two organic compounds are brought into contact with each other. Therefore, any organic compound can be used as the acceptor organic compound as long as it is an electron-accepting organic compound. For example, condensed aromatic carbocyclic compounds (naphthalene, anthracene, fullerene, phenanthrene, tetracene, pyrene, perylene, fluoranthene, or derivatives thereof), 5- to 7-membered heterocyclic compounds containing nitrogen, oxygen and sulfur atoms (e.g. pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyraridine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compounds , fluorene compounds, cyclopentadiene compounds, silyl compounds, and metal complexes having nitrogen-containing heterocyclic compounds as ligands. In addition, as described above, any organic compound having a higher electron affinity than the organic compound used as the donor organic compound may be used as the acceptor organic semiconductor.

The thickness of the photoelectric conversion layer is preferably 100-1000 nm, more preferably 100-500 nm.

<<Conductive thin film>>
The conductive thin films are anode and cathode electrodes, which are made of a conductive material. It may be a transparent conductive thin film. The anode and cathode are not particularly limited as long as they are conductive materials 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), molybdenum oxide (MoO), and titanium oxide. , metal nitrides such as titanium oxynitride (TiNxOx) and titanium nitride (TiN), gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), aluminum (Al), etc. Examples include metals, mixtures or laminates of these metals and conductive metal oxides, organic conductive compounds such as polyaniline, polythiophene and polypyrrole, and laminates of these with ITO.

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

<Image sensor>
The imaging element is configured by including the photoelectric conversion element.

Hereinafter, the embodiments of the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

<Synthesis of 1,3,5-tris(9H-carbazol-9-yl)benzene (compound 1-1)>
1,3,5-tribromobenzene: 10.0 g, carbazole: 17.9 g, copper powder: 0.4 g, 1,10-phenanthroline: 1.1 g, sodium sulfite: 1 in a reaction vessel vented with nitrogen gas. 0 g, potassium carbonate: 13.2 g, and dodecylbenzene: 19 mL were added, and the mixture was stirred at 190° C. for 8 hours. The mixture was allowed to cool to room temperature, 200 mL of toluene was added, and the mixture was stirred at 100° C. for 1 hour, filtered hot, and the filtrate was concentrated to obtain a crude product. The crude product was recrystallized from toluene to obtain 5.1 g of white powder of 1,3,5-tris(9H-carbazol-9-yl)benzene (compound 1-1) (yield 28%).

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 27 hydrogen signals. δ (ppm) = 8.18-8.16 (6H), 7.96 (3H), 7.68-7.66 (6H), 7.49-7.46 (6H), 7.35-7 .32 (6H).

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

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 36 hydrogen signals. δ (ppm) = 8.13-8.08 (6H), 7.57-7.47 (6H), 7.39-7.13 (24H).

<Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (compound 1-18)>
2-{3,5-Difluoro-phenyl}-4,6-diphenyl-benzoxazole: 3.7 g, carbazole: 3.4 g, and cesium carbonate: 12.9 g were charged into a reaction vessel, and the temperature was adjusted to 120 under DMF solvent. The mixture was heated and stirred overnight at ℃. After standing to cool, H ₂ O was added and the precipitated solid was collected to obtain a crude product. The crude product was purified by crystallization from a mixed solvent of monochlorobenzene/acetone to give 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole ( 4.8 g of white powder of compound 1-18) was obtained (yield 30%).

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 31 hydrogen signals. δ (ppm) = 8.81 (1H), 8.25 (4H), 8.02 (1H), 7.94 (1H), 7.69 (2H), 7.63 (1H), 7.56 (2H), 7.55 (2H), 7.48-7.29 (17H).

<Synthesis of 4,6-diphenyl-2-{3,5-bis(9H-carbazol-9-yl)phenyl}pyrimidine (compound 1-19)>
4,6-diphenyl-2-chloropyrimidine: 30.0 g, 3,5-bis(9H-carbazol-9-yl)phenylboronic acid: 56.0 g, potassium carbonate: 46 .6 g, toluene: 210 mL, ethanol: 52.8 mL, H ₂ O: 168 mL, and tetrakis(triphenylphosphine)palladium(0): 3.9 g were added, and the mixture was stirred while heating under reflux. After the raw materials disappeared, the mixture was allowed to cool to room temperature, 600 mL of methanol was added to precipitate a solid, and the mixture was filtered. Monochlorobenzene was added to the solid to dissolve it by heating, and after hot filtration, the filtrate was concentrated, acetone was added to precipitate the solid again, and the solid was filtered to obtain a crude product. The crude product was purified by recrystallization twice using monochlorobenzene to obtain 4,6-diphenyl-2-{3,5-bis(9H-carbazol-9-yl)phenyl}pyrimidine (compound 1- 50.0 g (yield 69.6%) of white powder of 19) was obtained.

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 30 hydrogen signals. δ (ppm) = 9.06-9.05 (2H), 8.28-8.24 (4H), 8.21-8.19 (4H), 8.13 (1H), 7.95-7 .94 (1H), 7.65-7.63 (4H), 7.54-7.51 (6H), 7.49-7.45 (4H), 7.36-7.32 (4H).

<Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-biphenyl-4′-yl}-benzoxazole (compound 1-24)>
A reaction vessel was charged with 2-(4-bromophenyl)-benzoxazole: 4.0 g and 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid: 7.3 g, toluene 80 mL, 20 mL of ethanol and then an aqueous solution prepared by previously dissolving 2.4 g of potassium carbonate in 20 mL of H ₂ O were added, and nitrogen gas was bubbled through while applying ultrasonic waves for 30 minutes. Tetrakis(triphenylphosphine)palladium (0): 0.3 g was added and stirred overnight under reflux with heating. After standing to cool, the organic layer was separated by a liquid separation operation and concentrated to obtain a crude product. By purifying the crude product by crystallization with a mixed solvent of toluene/acetone, 2-{(3,5-di([9H]-carbazol-9-yl)-biphenyl-4′-yl}-benzoxazole (compound 1-24) was obtained as a white powder (4.4 g, yield 50%).

The structure of the resulting white powder was identified using NMR.

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

<Synthesis of 6-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenyl-benzoxazole (compound 1-25)>
In a reaction vessel, 6-chloro-2,4-diphenyl-benzoxazole: 10.0 g, 3,5-di([9H]-carbazol-9-yl)-phenylboronic acid: 7.5 g, bis(dibenzylidene) Acetone)palladium(0): 0.5 g, tricyclohexylphosphine: 1.1 g, and tripotassium phosphate: 12.1 g were charged and stirred under reflux overnight in a 1,4-dioxane/H ₂ O mixed solvent. After allowing to cool, the mixture was separated, the aqueous layer was extracted with ethyl acetate, and the resulting crude product was purified by column chromatography (carrier: silica gel, eluent: dichloromethane/ethyl acetate). 6-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,4-diphenyl-benzoxazole (compound 1-25 ) was obtained as a white powder (61% yield).

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 31 hydrogen signals. δ (ppm) = 8.35 (2H), 8.21 (4H), 8.11 (2H), 8.07 (2H), 7.91 (2H), 7.88 (1H), 7.66 (4H), 7.59-7.42 (10H), 7.36 (4H).

<Synthesis of 2-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (compound 1-26)>
In Example 6, 2-{3,5-dichloro-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole was substituted for 6-chloro-2,4-diphenyl-benzoxazole. 2-{(3,5-di( [9H]-carbazol-9-yl)-phenyl}-6-(biphenyl-4-yl)-4-phenyl-benzoxazole (compound 1-26), 7.9 g (yield 57%) of white powder. Obtained.

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 35 hydrogen signals. δ (ppm) = 8.68 (2H), 8.22 (4H), 8.11 (2H), 8.01 (1H), 7.87 (2H), 7.79 (4H), 7.69 (2H), 7.64 (4H), 7.57-7.47 (8H), 7.42 (2H), 7.38 (4H).

<Synthesis of 4-{(3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (compound 1-27)>
In Example 6, 6-chloro-4-{3,5-di([9H]-carbazol-9-yl)-phenyl}-2- was substituted for 6-chloro-2,4-diphenyl-benzoxazole. 4-{ 8.0 g (60% yield) of white powder of (3,5-di([9H]-carbazol-9-yl)-phenyl}-2,6-diphenyl-benzoxazole (compound 1-27) was obtained. rice field.

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 31 hydrogen signals. δ (ppm) = 8.52 (2H), 8.42 (2H), 8.21 (4H), 7.91 (1H), 7.90 (1H), 7.87 (1H), 7.85 (4H), 7.71 (2H), 7.65-7.46 (9H), 7.45-7.34 (5H).

<Synthesis of 9,9-bis(4-carbazolyl-phenyl)-fluorene (compound 1-35)>
9,9-Bis(4-iodophenyl)-fluorene: 8.9 g, carbazole: 5.5 g, potassium carbonate: 4.8 g, copper powder 0.5 g, diphenyl ether: 8 mL were charged into a reaction vessel and heated at 240°C. The mixture was heated and stirred for 4 hours. After allowing to cool, 300 mL of toluene was added, the mixture was stirred for 1 hour, hot-filtered, and the filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography to obtain 3.7 g of white powder of 9,9-bis(4-carbazolyl-phenyl)-fluorene (compound 1-35) (38% yield).

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 32 hydrogen signals. δ (ppm) = 8.12 (4H), 7.87 (2H), 7.60 (2H), 7.54-7.49 (8H), 7.47-7.41 (4H), 7.47-7.41 (4H); 43 (4H), 7.38 (4H), 7.26 (4H).

<Synthesis of 2,7-bis(5H,7H-7,7-dimethylindeno[2,1-b]carbazol-5-yl)-9,9-dimethyl-9H-fluorene (compound 1-37)>
3.0 g of 2,7-dibromo-9,9-dimethyl-9H-fluorene, 5H,7H-7,7-dimethylindeno[2,1-b]carbazole:5. 6 g, palladium(II) acetate: 0.15 g, sodium t-butoxy: 2.5 g, tri(t-butyl)phosphine: 0.55 g, and xylene: 100 mL were added, and the mixture was stirred under reflux for 6 hours. After the raw material disappeared, saturated saline and toluene were added, hot filtration was performed, and the filtrate was separated. Anhydrous magnesium sulfate was added to the organic layer for dehydration, followed by filtration, and the filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: hexane/chloroform) to give 2,7-bis(5H,7H-7,7-dimethylindeno[2,1-b]carbazole-5- 2.5 g (yield 38.5%) of white powder of yl)-9,9-dimethyl-9H-fluorene (compound 1-37) was obtained.

The structure of the resulting white powder was identified using NMR.

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

<Synthesis of bis-{4-(benzoxazol-2-yl)phenyl}-{4-(naphthalen-1-yl)phenyl}amine (compound 1-84)>
4-(Naphthalen-1-yl)phenyl-amine: 7.5 g, 2-(4-bromophenyl)benzoxazole: 20.6 g, sodium t-butoxy: 9.9 g, and toluene: 150 mL were added to a reaction vessel. Nitrogen gas was bubbled through while applying ultrasonic waves for 30 minutes. 0.9 g of tris(dibenzylideneacetone) dipalladium (0) and 0.4 mL of a 50% (w/v) toluene solution of tri-(t-butyl)phosphine were added, and the mixture was stirred under reflux with heating for 3 hours. . After allowing the reaction vessel to cool to 80° C., the insoluble matter was filtered and the filtrate was concentrated to obtain a crude product. The crude product was purified by column chromatography to give yellow powder 3 of bis-{4-(benzoxazol-2-yl)phenyl}-{4-(naphthalen-1-yl)phenyl}amine (compound 1-84). .4 g (16% yield) was obtained.

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

¹ H-NMR (CDCl ₃ ) detected the following 27 hydrogen signals. δ (ppm) = 8.26-8.22 (4H), 8.09-8.02 (1H), 7.97-7.89 (2H), 7.83-7.77 (2H), 7 .63-7.49 (8H), 7.42-7.32 (10H).

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

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 25 hydrogen signals. δ (ppm) = 9.40 (2H), 8.55 (2H), 8.43 (4H), 8.22 (2H), 7.95 (1H), 7.84 (2H), 7.69 (4H), 7.54-7.46 (4H), 7.41-7.34 (4H).

<Synthesis of 2-{(3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole (compound 1-114)>
2-{3,4-Difluoro-phenyl}-4,6-diphenyl-benzoxazole: 3.7 g, carbazole: 3.4 g, and cesium carbonate: 12.9 g were charged in a reaction vessel, and the temperature was adjusted to 120 under DMF solvent. The mixture was heated and stirred overnight at ℃. After standing to cool, H ₂ O was added and the precipitated solid was collected to obtain a crude product. The crude product was purified by crystallization from a mixed solvent of monochlorobenzene/acetone to give 2-{(3,4-di([9H]-carbazol-9-yl)-phenyl}-4,6-diphenyl-benzoxazole ( 3.1 g of white powder of compound 1-114) was obtained (yield 60%).

The structure of the resulting white powder was identified using NMR.

¹ H-NMR (CDCl ₃ ) detected the following 31 hydrogen signals. δ (ppm) = 8.79 (1H), 8.67 (1H), 8.14 (2H), 8.04 (1H), 7.89-7.79 (6H), 7.75 (2H) , 7.56 (4H), 7.45 (2H), 7.24 (4H), 7.15-7.06 (8H).

The glass transition temperatures of the compounds of Examples 1 to 13 were measured with a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). EBL-1 (see Patent Document 4) and EBL-2 (see Patent Document 5) having the following structures, which are high glass transition temperature compounds, were also measured in the same manner, and the results of the measured glass transition temperatures are shown. 1 collectively.

The compound of the embodiment has a glass transition temperature as high as 120° C. or higher, indicating that the thin film state is stable. Further, the glass transition temperatures of the compounds of Examples 1 to 13 are higher than that of EBL-2, and by using them in place of EBL-2, it is possible to produce devices with better thermal stability.

<Measurement of HOMO level>
Using the compounds of Examples 1 to 13 and the comparative compounds EBL-1 and EBL-2, a deposited film with a thickness of 100 nm was prepared on an ITO substrate, and an ionization potential measuring device (Sumitomo Heavy Industries, Ltd. , PYS-202) are summarized in Table 2.

The compounds of the embodiments have a deep energy level of -5.90 to 6.32-eV compared to the HOMO levels of the comparative compounds EBL-1 and EBL-2, and are compatible with n-type semiconductors. It is possible to suppress the movement of interfacial charge. By using the compounds of Examples 1 to 13 in place of EBL-1 and EBL-2, devices with lower dark current values can be produced.

<Measurement of hole mobility>
Using the compounds of Examples 1 to 13 and the comparative compounds EBL-1 and EBL-2, an organic compound to be measured was formed as a film with a thickness of 3 to 4 μm on a glass substrate with ITO by a vacuum deposition method. Subsequently, an aluminum film was formed to a thickness of about 100 nm to prepare an element for hole mobility measurement. This element was sealed with a glass cap to which a moisture getter sheet for organic EL was attached in a nitrogen atmosphere so as not to cause deterioration due to adsorption of moisture and oxygen.

The device was measured using a transient photocurrent measuring device under the following conditions. Table 3 shows the measured values obtained.
(Measurement condition)
Device: Time-of-flight measurement device TOF-401 (manufactured by Optel)
Excitation light source: Nitrogen laser (337.1 nm)
Optical pulse width: 1 nsec or less Measurement area: 0.04 cm ²
Sample temperature: 25°C
Load resistance: 50Ω
Electric field strength: 0.25MV/cm

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

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

Specifically, the glass substrate 1 on which ITO, which is the transparent anode 2, was subjected to ultrasonic cleaning in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 200° C. for 10 minutes. . Then, after performing UV ozone treatment for 15 minutes, this ITO-coated glass substrate was mounted in a vacuum deposition machine, and the pressure was reduced to 0.0001 Pa or less. Subsequently, as the electron blocking layer 3, the compound (1-1) of Example 1 was vapor-deposited to a thickness of 15 nm so as to cover the transparent anode 2. On the electron blocking layer 3, a p-type semiconductor (SubPC) having the following structural formula and an n-type semiconductor (C60) having the following structural formula are deposited as the photoelectric conversion layer 4 at a vapor deposition rate ratio of SubPC:C60=50:50. Two-source vapor deposition was performed at different vapor deposition rates to form a film having a thickness of 200 nm. Gold was formed as a cathode 5 on the photoelectric conversion layer 4 so as to have a film thickness of 100 nm. Table 4 summarizes the measurement results of the produced photoelectric conversion elements.

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

A photoelectric conversion element was produced in the same manner as in Example 17 except that the compound (1-18) of Example 3 was used instead of the compound (1-1) used as the material for the electron blocking layer 3, and the electrical characteristics evaluated. Table 4 summarizes the measurement results.

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

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

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

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

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

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

As shown in Table 4, the devices of Examples 17 to 22 realized low dark current even in the range of 1 to 5 V compared to the devices of Comparative Examples, and photoelectric conversion devices compatible with a wide range of drive voltages. can be produced. In particular, the dark current values at the time of applying 5 V are 1.4E-03A/cm ² and 2.0E-05A/cm ² for the devices of Comparative Examples 1 and 2, respectively, while the devices of Examples 17 to 22 are A low dark current value of 8.5E-08 to 9.5E-07A/cm ² was realized. In addition, bright current was also observed in the devices of Examples 17 to 22, and it can be seen that photoelectric conversion devices were produced.

From the above results, the photoelectric conversion element using the compound represented by the general formula (1) of the present embodiment as an electron blocking layer can suppress charge transfer from the acceptor organic semiconductor used in the photoelectric conversion layer. It was found that the dark current value can be greatly reduced. It was shown that the compound represented by the general formula (1) of the present embodiment has the HOMO level, high heat resistance, and sufficient hole mobility necessary for the electron blocking layer of a photoelectric conversion device. .

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

The organic thin film of the present invention, which has high heat resistance and good charge mobility, can be applied to various photoelectric conversion elements, and therefore has good dark current characteristics and conversion efficiency. An optical sensor can be provided.

1 glass substrate 2 transparent anode 3 electron blocking layer 4 photoelectric conversion layer 5 cathode

Claims (10)

An organic photoelectric conversion device comprising a conductive thin film, an organic photoelectric conversion layer, a blocking layer and a transparent conductive thin film, wherein the blocking layer contains a blocking material having the following properties:
(1) a glass transition temperature (Tg) of 110° C. or higher;
(2) the highest occupied molecular orbital (HOMO) level is -5.8 to -7.0 eV,
(3) The hole mobility (μh) at an electric field strength of 0.25 MV/cm is 1.0×10 ⁻⁷ <μh<1.0×10 ⁻² (cm ² /Vs). 2. The photoelectric conversion device according to claim 1, wherein said blocking layer is an electron blocking layer. 3. The photoelectric conversion device according to claim 2, wherein the thickness of said blocking layer is smaller than the thickness of said organic photoelectric conversion layer. 4. The photoelectric conversion device according to claim 3, wherein the blocking material is a compound containing two or more condensed heterocyclic groups consisting of a five-membered heterocyclic ring. 5. The photoelectric conversion device according to claim 4, wherein the blocking material is a compound represented by the following general formula (1).

(In the formula, Ar ₁ and Ar ₂ may be the same or different, and may be substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups, or substituted or unsubstituted condensed poly represents a ring aromatic group,
L ₁ represents 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 triarylamine ,
a represents an integer of 2 to 4,
b represents an integer of 0 to 2; ) 6. The photoelectric conversion device according to claim 5, wherein in the general formula (1), Ar ₁ has a structure selected from the group consisting of the following general formulas (2-a) to (2-t).

(In the formula,
X represents S, O, Se, C—R ₁ R ₂ , Si—R ₁ R ₂ , or N—Ar ₃ ;
Y represents S, O, Se, Si—R ₁ R ₂ or N—Ar ₃ ;
Z represents N or C—R ₃ ;
R ₁ to R ₃ may be the same or different, and may be a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, or an optionally substituted straight chain having 1 to 8 carbon atoms. or a branched alkyl group, an optionally substituted cycloalkyl group having 5 to 10 carbon atoms, or an optionally substituted linear or branched 2 to 6 carbon atom alkenyl group, optionally substituted C1-8 linear or branched alkyloxy group, optionally substituted C2-10 cycloalkyloxy group , a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,
Adjacent groups of R ₁ to R ₃ may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring,
Ar ₃ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group;
Dashed lines indicate binding sites. ) In the general formula (1), L ₁ is a divalent to pentavalent group which may have a substituent, benzene, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 1,3 ,5-triphenylbenzene, naphthyl, phenanthrene, triphenylene, furan, thiophene, dibenzofuran, dibenzothiophene, 9,9-spirobi[9H-fluorene], 9,9-dimethylfluorene, 9,9-diphenylfluorene, triphenylamine , 9-phenylcarbazole, pyridine, pyrimidine, 1,3,5-triazine, 2,6-diphenylpyridine, or 2,4,6-triphenylpyrimidine. 8. The photoelectric conversion device according to claim 7, wherein Ar ₂ in the general formula (1) is a structure selected from the group consisting of the following general formulas (3-a) to (3-v).

(In the formula,
R ₄ has the same definition as R ₁ to R ₃ in the general formulas (2-a) to (2-t);
The dashed line indicates the binding site,
d represents an integer of 0 to 4,
e represents an integer of 0 to 3,
f represents an integer of 0-2. ) The photoelectric conversion device according to any one of claims 1 to 8, wherein the organic photoelectric conversion layer contains fullerene or a fullerene derivative as the n-type semiconductor. An imaging device comprising the photoelectric conversion device according to any one of claims 1 to 9.

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