WO2022071444A1

WO2022071444A1 - Organic thin film to be used in photoelectric conversion element, and said photoelectric conversion element

Info

Publication number: WO2022071444A1
Application number: PCT/JP2021/035999
Authority: WO
Inventors: 大和島; 俊二望月; 直朗樺澤; 優太三枝
Original assignee: 保土谷化学工業株式会社
Priority date: 2020-10-01
Filing date: 2021-09-29
Publication date: 2022-04-07
Also published as: JPWO2022071444A1; KR20230078587A

Abstract

The main purpose of the present invention is to provide: an organic thin film which utilizes a compound that has excellent heat resistance and charge transport properties, and which is applicable to various photoelectric conversion elements; a photoelectric conversion element which uses this organic thin film; and an imaging element.　The present invention provides: an organic thin film which contains a compound that has an indenophenanthrene ring structure represented by general formula (1); and a photoelectric conversion element which uses this organic thin film. (In the formula, A represents a single bond, a divalent substituted or unsubstituted aromatic hydrocarbon group, or the like; each of Ar₁ and Ar₂ represents a substituted or unsubstituted aromatic hydrocarbon group or the like; each of R₁ to R₁₁ represents a hydrogen atom, an optionally substituted linear or branched alkyl group having from 1 to 6 carbon atoms, or the like; and each of R₁₂ and R₁₃ represents an optionally substituted linear or branched alkyl group having from 1 to 6 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, or the like.)

Description

Organic thin films used for photoelectric conversion elements and their photoelectric conversion elements

The present invention relates to an organic thin film used for a photoelectric conversion element and a photoelectric conversion element thereof. Specifically, the present invention relates to an organic thin film containing a compound having an indenophenanthrene ring structure, and various photoelectric conversion elements using the organic thin film. In particular, it relates to an image pickup device.

Photoelectric conversion elements are widely used in, for example, solar cells and optical sensors. Among them, the image sensor, which is an image sensor, is expanding not only for TV cameras and cameras equipped with smartphones, but also for driving support systems and other applications and markets.

Inorganic materials such as Si film and Se film have been used as materials for conventional image sensors, and there are two imaging methods: a three-plate type that uses a prism to separate colors and a single-plate type that uses a color filter. It was mainstream. However, although the three-plate type has a high light utilization rate, it is difficult to miniaturize because it uses a prism, and the single-plate type is relatively easy to miniaturize because it does not use a prism, but because a color filter is used instead. The resolution and the utilization rate of light were poor (Non-Patent Document 1).

Since organic matter absorbs light of a specific wavelength better than inorganic matter, an image sensor that can efficiently use each of the three primary colors without using a prism by combining materials suitable for each wavelength. Can be built. Therefore, the efficiency of light utilization is high, and it is possible to manufacture a small image sensor. In addition, there is a possibility of adding value such as flexibility and large area by coating in the manufacturing process, which cannot be achieved by inorganic substances (Non-Patent Document 2).

For these reasons, photoelectric conversion elements using organic substances are expected to be applied to next-generation image sensors, and several groups have reported. For example, an example in which a quinacdrine derivative or a quinazoline derivative is used in a photoelectric conversion element (Patent Document 1), an example in which a benzothiebenzothiophene derivative is used in a photoelectric conversion element (Patent Document 2), and an example in which indrocarbazole is used in a photoelectric conversion element. (Patent Document 3) and the like.

Generally, it is considered that the performance of an organic image sensor is improved by aiming at reduction of dark current for the purpose of high contrast and power saving. In order to reduce the dark current, a method of inserting a hole block layer or an electron block layer between the photoelectric conversion unit and the electrode unit may be used.

The hole block layer and the electron block layer are methods generally used in the field of organic electronics, and are arranged at the interface between an electrode or a conductive film and another film in the constituent film of the device, respectively. It has the function of rapidly moving the required charge while controlling the reverse movement of holes or electrons.

In addition, thermal stability is one of the characteristics required for electron blocking materials. In particular, the image sensor has higher thermal stability than other organic electronic devices because it is applied to manufacturing processes that have a heating process such as color filter installation, protective film installation, and element soldering, and is considered to improve storage stability. Desired. Patent Document 4 reports that the thermal stability of a device is improved by using an electron blocking material having a glass transition temperature (Tg) of 140 ° C. or higher. However, the compound proposed here has a problem of a decrease in hole transport ability due to steric hindrance.

Japanese Unexamined Patent Publication No. 2007-234651 Japanese Unexamined Patent Publication No. 2018-170487 US10886335 US90855537 US2020 / 0365513

The present invention has been made in view of such a situation, and provides an organic thin film used for a photoelectric conversion element using a compound having excellent heat resistance and charge transport property, and uses the organic thin film. It is an object of the present invention to provide various photoelectric conversion elements, particularly an image pickup element, and an optical sensor using the same.

In order to achieve the above object, the present inventors have focused on the fact that a compound having an indenophenanthrene ring structure has high charge transportability and further excellent heat resistance, and aim to further improve the heat resistance. As a result of diligent development, it was found that an organic thin film containing a specific compound represented by the following general formula (1) solves the above-mentioned problems, and the present invention has been completed.

That is, the present invention relates to the following items.
1) An organic thin film used for a photoelectric conversion element, the organic thin film containing a compound having an indenophenanthrene ring structure represented by the following general formula (1).

(In the formula, A is a single-bonded, divalently substituted or unsubstituted aromatic hydrocarbon group, a divalent substituted or unsubstituted aromatic heterocyclic group, or a divalent substituted or unsubstituted condensed polycyclic aromatic group. Represents the group
Ar ₁ and Ar ₂ may be the same or different from each other, and may be a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. Represent,
A, Ar ₁ and Ar ₂ may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.
R ₁ to R ₁₁ may be the same or different from each other, and may have a hydrogen atom, a hydrocarbon atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, and a substituent, and have 1 to 6 carbon atoms. Linear or branched alkyl group, cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, and linear chain having 2 to 6 carbon atoms which may have a substituent. Alternatively, a branched alkenyl group, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, and a carbon atom having 5 to 10 which may have a substituent may have a substituent. Represents a cycloalkyloxy group, 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.
R ₁ to R ₁₁ may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.
R ₁₂ and R ₁₃ may be the same or different from each other, and may have a substituent. Even if they have a linear or branched alkyl group having 1 to 6 carbon atoms and a substituent. A good cycloalkyl group having 5 to 10 carbon atoms, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, and a carbon atom which may have a substituent. 1-6 linear or branched alkyloxy groups, 5-10 cycloalkyloxy groups optionally having substituents, substituted or unsubstituted aromatic hydrocarbon groups, substituted or absent Represents a substituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group or a substituted or unsubstituted aryloxy group.
R ₁₂ and R ₁₃ may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring. )

2) The organic thin film according to 1), wherein the compound having an indenophenanthrene ring structure represented by the general formula (1) is a compound having an indenophenanthrene ring structure represented by the following general formula (2). ..

(In the formula, A and R ₁ to R ₁₃ are the same as the definitions of A and R ₁ to R ₁₃ in the general formula (1), and R ₁₄ to R ₂₁ are R ₁ to R in the general formula (1). It is the same as the definition of _11. )

3) The organic thin film according to 1), wherein the compound having an indenophenanthrene ring structure represented by the general formula (1) is a compound having an indenophenanthrene ring structure represented by the following general formula (3). ..

(In the formula, R ₁ to R ₁₃ are the same as the definitions of R ₁ to R ₁₃ in the general formula (1), and R ₁₄ to R ₂₀ are the definitions of R ₁ to R ₁₁ in the general formula (1). It is the same, and Ar is the same as the definition of Ar ₁ and Ar ₂ in the general formula (1).)

4) A photoelectric conversion element in which at least an anode, a buffer layer, a photoelectric conversion layer, and a cathode are laminated in this order, and a photoelectric conversion element having a layer made of an organic thin film according to any one of 1) to 3). ..

5) The photoelectric conversion element according to 4), wherein the layer made of the organic thin film is a buffer layer.

6) The photoelectric conversion element according to 4), wherein the layer made of the organic thin film is a photoelectric conversion layer.

7) An image pickup device having the photoelectric conversion element according to any one of 4) to 6).

The organic thin film containing a compound having an indenophenanthrene ring structure represented by the general formula (1) of the present invention is an organic thin film having excellent heat resistance and charge transport property, and can be applied to various photoelectric conversion elements. Thereby, it is possible to provide a photoelectric conversion element having good dark current characteristics and conversion efficiency, particularly an image pickup element, and an optical sensor using the image pickup element.

This is a configuration example of the photoelectric conversion element of the present invention.

The present invention is a photoelectric conversion element used for a photoelectric conversion element, which comprises an organic thin film containing a compound having an indenophenanthrene ring structure represented by the above general formula (1) and an organic thin film thereof.

"Divalent substituted or unsubstituted aromatic hydrocarbon group", "divalent substituted or unsubstituted aromatic heterocyclic group", or "divalent substituted or unsubstituted aromatic heterocyclic group" in the above general formula (1). Examples of the "divalent aromatic hydrocarbon group", "divalent aromatic heterocyclic group" or "divalent condensed polycyclic aromatic group" in the "fused polycyclic aromatic group" include a phenylene group and a biphenylene group. Examples thereof include a terphenylene group, a naphthylene group, an anthrasenylene group, a thienylene group, a furanylene group and a phenanthrenylene group. Further, it is also possible to select from an arylene group having 6 to 30 carbon atoms and a heteroarylene group having 2 to 30 carbon atoms.

"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). Examples of the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" include phenyl group, biphenylyl group, turfenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, fluorenyl group and spirobiflu. Olenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group Group, indrill group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzoimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyldinyl group, phenanthrolinyl group, acridinyl group, carbolinyl group, etc. Can be mentioned. Further, it can be selected from an aryl group having 6 to 30 carbon atoms and a heteroaryl group having 2 to 30 carbon atoms.

In the above general formula (1), "a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent" and "the number of carbon atoms which may have a substituent 5". A linear or branched alkenyl group having 1 to 6 carbon atoms in a "cycloalkyl group of ~ 10" or a "linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent". The "alkyl group", "cycloalkyl group having 5 to 10 carbon atoms", or "linear or branched alkenyl group having 2 to 6 carbon atoms" includes a methyl group, an ethyl group and an 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, 1-adamantyl group, 2-adamantyl group, vinyl Examples thereof include a group, an allyl group, an isopropenyl group and a 2-butenyl group.

In the above general formula (1), "a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent" or "the number of carbon atoms which may have a substituent". The "linear or branched alkyloxy group having 1 to 6 carbon atoms" in "5 to 10 cycloalkyloxy groups" or the "cycloalkyloxy group having 5 to 10 carbon atoms" includes a methyloxy group. Ethyloxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group, cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, cyclooctyl Examples thereof include an oxy group, a 1-adamantyloxy group and a 2-adamantyloxy group.

The "aryloxy group" in the "substituted or unsubstituted aryloxy group" in the above general formula (1) includes a phenyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthioxyl group, and an anthrasenyloxy group. And aryloxy groups having 6 to 30 carbon atoms such as phenylanthrenyloxy groups can be mentioned.

It has a "substituted aromatic hydrocarbon group", a "substituted aromatic heterocyclic group", a "substituted condensed polycyclic aromatic group", a "substituted methylene group" and a "substituted group" in the above general formula (1). It may have a linear or branched alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, and a substituent. A linear or branched alkenyl group having 2 to 6 carbon atoms may be good, a "linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent", or The "substituent" in the "cycloalkyloxy group having 5 to 10 carbon atoms which may have a substituent" includes a heavy hydrogen atom, a cyano group and a nitro group; a fluorine atom, a chlorine atom, a bromine atom and an iodine. Halogen atoms such as atoms; Cyril groups such as trimethylsilyl group and triphenylsilyl group; Linear or branched alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group and propyl group; methyloxy group and ethyloxy A linear or branched alkyloxy group having 1 to 6 carbon atoms such as a group and a propyloxy group; an alkenyl group such as a vinyl group and an allyl group; an aryloxy group such as a phenyloxy group and a trilloxy group; a benzyloxy group. , Fenetyloxy group and other arylalkyloxy groups; phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthrasenyl group, phenanthrenyl group, fluorenyl group, spirobifluorenyl group, indenyl group, pyrenyl group, peryleneyl group, fluorane Aromatic hydrocarbon group such as tenyl group, triphenylenyl group or condensed polycyclic aromatic group; pyridyl group, thienyl group, frill group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group , Benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzoimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carborinyl group and other aromatic heterocyclic groups, and these substituents are further added. It may be substituted with the above-exemplified substituent.

In the present invention, it is preferable that R ₁ to R ₁₁ in the above general formula (1) are hydrogen atoms because the synthesis is easy.

Further, from the viewpoint of heat resistance and charge mobility, it is preferable that Ar ₁ and Ar ₂ are substituted or unsubstituted aromatic hydrocarbon groups, and R ₁₂ and R ₁₃ may have a substituent. It is preferably a linear or branched alkyl group having 1 to 6 atoms or a substituted or unsubstituted aromatic hydrocarbon group. In addition, R ₁₂ and R ₁₃ may be bonded to each other via a single bond, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.

From the viewpoint of heat resistance and charge mobility, as one of the preferred embodiments of the present invention, Ar ₁ and Ar ₂ in the above general formula (1) are substituted or unsubstituted aromatic hydrocarbon groups, and are simply used. Examples thereof include compounds which are bonded to each other via a bonded, substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring. In particular, compounds in which Ar ₁ and Ar ₂ are unsubstituted aromatic hydrocarbon groups and are bonded to each other via a single bond to form a ring are preferable.

A compound in which Ar ₁ and Ar ₂ in the above general formula (1) are substituted or unsubstituted aromatic hydrocarbon groups, and Ar ₁ and Ar ₂ are bonded to each other via a single bond to form a ring. Examples thereof include the compound represented by the above general formula (2). In particular, the compound in which A in the general formula (2) is a single bond is preferable, and specifically, the exemplified compounds 1-16, 1-20, 1-39, 1-61, 1-62, 1-63 , 1-64, 1-65 and 1-66.

A and R ₁ to R ₁₃ in the general formula (2) are the same as the definitions of R ₁ to R ₁₃ in the general formula (1), and R ₁₄ to R ₂₁ are in the general formula (1). It is the same as the definition of R ₁ to R ₁₁ . That is, as all the substituents related to the general formula (2), the groups exemplified in the explanation of the general formula (1) can be mentioned.

In the present invention, from the viewpoint of heat resistance and mobility, R ₁₂ and R ₁₃ in the above general formula (2) may have a substituent in a linear or branched form having 1 to 6 carbon atoms. Is preferably an alkyl group 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. It is preferably an unsubstituted aromatic hydrocarbon group, and particularly preferably. In addition, R ₁₂ and R ₁₃ may be bonded to each other via a single bond, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.

Further, since it is easy to synthesize, it is preferable that R ₁ to R ₁₁ and R ₁₄ to R ₂₁ in the above general formula (2) are hydrogen atoms.

From the viewpoint of heat resistance and charge mobility, as one of the preferred embodiments of the present invention, A in the above general formula (1) is a substituted or unsubstituted aromatic hydrocarbon group, and A and Ar ₁ are used. , Or a compound in which A and Ar ₂ are bonded to each other via a single bond to form a ring, and examples of such a compound include a compound represented by the above general formula (3). More specifically, Exemplified Compounds 1-2, 1-6, 1-7, 1-12, 1-23, 1-25, 1-26, 1-31, 1-44, 1-47 and 1- 48 is mentioned.

Ar in the general formula (3) has the same definition as Ar ₁ and Ar ₂ in the general formula (1), and R ₁ to R ₁₃ are R ₁ to R ₁₃ in the general formula (1). It is the same as the definition, and R ₁₄ to R ₂₀ are the same as the definition of R ₁ to R ₁₁ in the above general formula (1). That is, as all the substituents related to the general formula (3), the groups exemplified in the above explanation of the general formula (1) can be mentioned.

In the present invention, from the viewpoint of heat resistance and charge mobility, it is preferable that Ar in the above general formula (3) is a substituted or unsubstituted aromatic hydrocarbon group, and an aryl group having 6 to 30 carbon atoms is used. It is more preferable to have an aryl group having 6 to 18 carbon atoms.

From the same viewpoint, R ₁₂ and R ₁₃ in the above general formula (3) may have a substituent, and may have a linear or branched alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted alkyl group. It is preferably an aromatic hydrocarbon group, and more preferably a linear or branched alkyl group having 1 to 6 carbon atoms or an unsubstituted aromatic hydrocarbon group. In addition, R ₁₂ and R ₁₃ may be bonded to each other via a single bond, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.

Further, since it is easy to synthesize, it is preferable that R ₁ to R ₁₁ and R ₁₄ to R ₂₀ in the above general formula (3) are hydrogen atoms.

Specific examples of preferable compounds among the compounds having an indenophenanthrene ring structure represented by the above general formula (1) are shown below, but the present invention is not limited to these compounds.

The above-mentioned compound having an indenophenanthrene ring structure can be synthesized according to a method known per se (for example, Patent Document 5).

Purification of these compounds can be performed by purification by column chromatography, adsorption purification with silica gel, activated charcoal, activated white clay, etc., recrystallization with a solvent, crystallization method, or the like. Compound identification can be performed by NMR analysis. As physical property values, it is preferable to measure the glass transition point (Tg) and the work function. The glass transition point (Tg) is an index of the stability of the thin film state, and the work function is an index of the hole transport property.

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

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

The compound having an indenophenanthrene ring structure represented by the above general formula (1) can form an organic thin film by a known method such as a vapor deposition method, a spin coating method and an inkjet method. Further, the compound having an indenophenanthrene ring structure represented by the general formula (1) may be formed alone, or a plurality of types may be mixed and formed. Further, it can be mixed with other compounds to form a film as long as the effect of the present invention is not impaired.

The organic thin film containing a compound having an indenophenanthrene ring structure represented by the above general formula (1) is suitable for use in a photoelectric conversion element, particularly an image pickup element. The configuration of the photoelectric conversion element includes, 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 represented by the above general formula (1). Examples thereof include an organic thin film containing a compound having an indenophenanthrene ring structure. In such a multilayer structure, it is possible to add layers, and for example, a configuration having a first electrode, a first buffer layer, a photoelectric conversion layer, a second buffer layer, and a second electrode can be used. Further, the organic thin film containing the compound having an indenophenanthrene ring structure represented by the general formula (1) can also be used for the photoelectric conversion layer.

The photoelectric conversion layer in the photoelectric conversion element of the present invention may be made of an organic material or an inorganic material, as long as it can generate a signal charge according to the amount of received light. When the photoelectric conversion layer is made of an organic material, the organic semiconductor film may be one layer or a plurality of layers, and in the case of one layer, a p-type organic semiconductor film, an n-type organic semiconductor film, or a p-type organic. A mixed film (bulk heterostructure) of a semiconductor and an n-type organic semiconductor is used. Further, in the case of a plurality of layers, the structure is such that any 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 is laminated, and the layers are layers. It is also possible to insert a buffer layer in.

The photoelectric conversion element of the present invention is stable against a heat load by using a compound having an indenophenanthrene ring structure represented by the above general formula (1) in the organic thin film to be the first buffer layer contained in the element. Can be obtained.

The p-type organic semiconductor used in the photoelectric conversion layer is a donor organic semiconductor, and is a compound having a property of easily donating electrons represented mainly by a hole-transporting organic compound. Examples of the p-type organic semiconductor include naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, pentacene derivatives, quinacridone derivatives, chrysene derivatives, fluoranthene derivatives, phthalocyanine derivatives, subphthalocyanine derivatives, and heterocyclic compounds. Metal complex with a ligand of, benzothiophene derivative, dinaphthothiophenophen derivative, dianthracenothienotiphene derivative, benzobisbenzothiophene derivative, thienovisbenzothiophene, dibenzothienobisbenzothiophene derivative, dithienobenzodithiophene derivative , Dibenzothienodithiophene derivative, benzodithiophene derivative, naphthodithiophene derivative, anthracenodithiophene derivative; thienoacene-based material typified by tetrasenodithiophene derivative, pentasenodithiophene derivative; triarylamine compound, carbazole compound, etc. Amine-based derivatives; indenocarbazole derivatives and the like can be mentioned.

The n-type organic semiconductor used in the photoelectric conversion layer is an acceptor-type organic semiconductor, which is an organic compound having a property of easily accepting electrons, which is mainly represented by an electron-transporting organic compound. More specifically, it is the organic compound having the higher electron affinity when two kinds of organic compounds are brought into contact with each other. Therefore, as the n-type organic semiconductor, any organic compound can be used as long as it is an electron-accepting organic compound. For example, fused aromatic carbocyclic compounds (naphthalene, anthracene, fullerene, phenanthrene, tetracene, pyrene, perylene, fluorantene, or derivatives thereof); 5- to 7-membered heterocyclic compounds containing nitrogen, oxygen, and sulfur atoms. (For example, pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxalin, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, aclysine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, Benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazyneden, oxadiazol, imidazolepyridine, pyrazine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.); Examples thereof include a fluorene compound; a cyclopentadiene compound; a silyl compound; a metal complex having a nitrogen-containing heterocyclic compound as a ligand. Not limited to this, 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 anode and cathode may be any one using a conductive material generally used as an electrode, and examples thereof include metals, metal oxides, metal nitrides, metal boronides and organic conductive compounds, and mixtures thereof. Be done. Specific examples include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium tin oxide (IZO), indium tungsten oxide (IWO), molybdenum oxide (MoO) and titanium oxide. Metal nitrides such as titanium oxide (TiN _x _Ox ) and titanium nitride (TiN); gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni) and aluminum (Al). ), As well as 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.

The second buffer layer may be inserted between the second electrode (cathode) and the photoelectric conversion layer, but the material used for this is a material whose work function value is larger than that used for the first buffer layer. Is preferable. For example, organic molecules and organic metal complexes containing a nitrogen-containing heterocycle such as pyridine, quinoline, acridine, indole, imidazole benzimidazole, and phenanthroline, and materials having less absorption in the visible light region are preferable. Further, in the case of forming with a thin film having a thickness of about 5 nm to 20 nm, fullerenes having absorption in the visible light region and derivatives thereof can also be used.

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

[Example 1]
<Synthesis of 11- (3,6-diphenylcarbazole-9-yl) -13,13-diphenylindeno [1,2-I] phenanthrene (Compound 1-35)>
To the nitrogen-substituted reaction vessel, 50.0 g of methyl 3-bromoanthranilate, 124.0 g of p-toluenesulfonic acid hydrate, and 500 ml of acetonitrile were added, and the mixture was cooled to 0 ° C. 22.5 g of sodium nitrite was added, and the mixture was stirred for 1 hour. After adding 72.2 g of potassium iodide, the mixture was stirred at room temperature. The reaction mixture was concentrated, ethyl acetate was added, and the mixture was separated. The organic layer was washed with an aqueous solution of sodium thiosulfate and saturated brine, dehydrated with anhydrous sodium sulfate, and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: chloroform / n-hexane), and 71.2 g (yield 96.1%) of a light purple powder of methyl 5-bromo-2-iodobenzoate was used. Got

To a reaction vessel substituted with nitrogen, 50.0 g of 9-bromophenanthrene, 54.3 g of bispinacholate diboron, 28.6 g of potassium acetate and 500 ml of 1,4-dioxane were added, nitrogen bubbling was performed, and then 1,1'-bis. 1.59 g of (diphenylphosphino) ferrocene dichloropalladium (II) dichloromethane adduct was added, and the mixture was stirred at 90 ° C. for 6.5 hours. The reaction mixture was concentrated, toluene and water were added, the mixture was stirred at 80 ° C., and the filtrate was hot-filtered using a filtration aid, and then the filtrate was separated. The organic layer was washed with saturated brine, dehydrated with anhydrous sodium sulfate, filtered, and silica gel was added to the filtrate for adsorption and purification. After filtration, the filtrate is concentrated, and then n-hexane is added to recrystallize the 9- (4,4,5,5-tetramethyl- [1,3,2] dioxaboran-2-yl) phenanthrene. 39.4 g (yield 66.6%) of the white solid was obtained.

52.4 g of the obtained methyl 5-bromo-2-iodobenzoate and 39.0 g of 9- (4,4,5,5-tetramethyl- [1,3,2] dioxaboran-2-yl) phenanthrene, 26.6 g of potassium carbonate, 312 ml of toluene, 117 ml of water, and 156 ml of ethanol were added to the reaction vessel, nitrogen bubbling was performed, 0.26 g of tetrakis (triphenylphosphine) palladium was added, and the mixture was heated and stirred at 73 ° C. for 20 hours. After separating the reaction solution, the organic layer was washed with saturated brine and dehydrated with anhydrous magnesium sulfate. After filtration, the filtrate is concentrated, purified by column chromatography (carrier: silica gel, eluent: chloroform / n-hexane), and white powder of 5-bromo-2- (9-phenanthrenyl) methyl benzoate 33. 6 g (yield 67.0%) was obtained.

14.4 g of bromobenzene was dissolved in 150 ml of tetrahydrofuran, n-butyllithium (1.6 M) was added dropwise at −70 ° C., and then 13.8 g of methyl 5-bromo-2- (9-phenanthrenyl) benzoate was added. The mixture was stirred at room temperature for 18 hours. After adding water, toluene was added to separate the liquids. Anhydrous sodium sulfate was added to the organic layer to dehydrate the mixture, and the mixture was filtered. The filtrate was concentrated, and n-hexane was added to precipitate a solid, which was then filtered. By recrystallizing the obtained solid with ethyl acetate / n-hexane, 11.1 g (yield 61.2%) of white powder of [5-bromo-2- (9-phenanthrenyl) phenyl] diphenylmethanol was obtained. ) Was obtained.

13.3 g of the obtained [5-bromo-2- (9-phenanthrenyl) phenyl] diphenylmethanol, 130 ml of acetic acid and 4 ml of 35% hydrochloric acid were added to the reaction vessel, and the mixture was stirred at 110 ° C. for 3 hours. After allowing to cool to room temperature, the mixture was filtered while being washed with methanol and water. The obtained solid was reflux-dispersed and washed with methanol and water, and filtered to obtain 12.4 g of white powder of 11-bromo-13,13-diphenylindeno [1,2-I] phenanthrene (12.4 g). Yield 96.5%) was obtained.

The obtained 11-bromo-13,13-diphenylindeno [1,2-I] phenanthrene [1,2-I] phenanthrene 5.50 g, 3,6-diphenylcarbazole 3.53 g, potassium carbonate 2.29 g, copper powder 0.035 g, 3, 0.14 g of 5-di-t-butylsalicylic acid and 30 ml of dodecylbenzene were added to the reaction vessel substituted with nitrogen, and the mixture was stirred at 210 ° C. for 27 hours. The reaction solution was diluted with toluene and the insoluble material was removed by filtration. The filtrate was concentrated, n-hexane was added, and the precipitated solid was collected by filtration, and recrystallized once with toluene and once with toluene / methanol, thereby 11- (3, 6). -Diphenylcarbazole-9-yl) -13,13-diphenylindeno [1,2-I] Phenanthrene (Compound 1-35) was obtained as a white powder of 2.68 g (yield 32.9%).

The structure of the obtained white powder was identified using NMR.
¹ The following 37 hydrogen signals were detected by 1 H-NMR (CDCl ₃ ).
δ (ppm) 9.08-9.06 (1H), 8.91-8.89 (1H), 8.79-8.77 (1H), 8.69-8.66 (1H), 8. 37 (2H), 7.89-7.77 (4H), 7.73-7.70 (5H), 7.63-7.55 (3H), 7.50-7.33 (13H), 7 .26-7.19 (6H).

[Example 2]
<Synthesis of 11- (carbazole-9-yl) -13,13-diphenylindeno "1,2-I" phenanthrene (Compound 1-66)>
11-bromo-13,13-diphenylindeno "1,2-I" phenanthrene 4.48 g and carbazole 1.50 g, potassium carbonate 1.87 g, copper powder 0.057 g, 3,5-di-t-butylsalicylic acid 0.22 g, 0.19 g of sodium hydrogen sulfite and 10 ml of dodecylbenzene were added to the reaction vessel substituted with nitrogen, and the mixture was stirred at 220 ° C. for 7 hours. The reaction solution was diluted with toluene and the insoluble material was removed by filtration. By concentrating the filtrate, adding acetone, collecting the precipitated solid by filtration, and performing recrystallization with toluene / methanol, 11- (carbazole-9-yl) -13,13-diphenylindeno "1" , 2-I ”Phenanthrene (Compound 1-66) white powder 2.1 g (yield 40.0%) was obtained.

The structure of the obtained white powder was identified using NMR.
¹ The following 29 hydrogen signals were detected by 1 H-NMR (CDCl ₃ ).
δ (ppm) 9.04-9.03 (1H), 8.86-8.84 (1H), 8.74-8.73 (1H), 8.63-8.61 (1H), 8. 11-8.10 (2H), 7.88-7.86 (1H), 7.83-7.80 (1H), 7.77-7.73 (2H), 7.66-7.64 ( 1H), 7.54-7.51 (1H), 7.43-7.42 (4H), 7.35-7.32 (5H), 7.26-7.16 (8H).

<Measurement of glass transition temperature>
The glass transition temperature of the compound (1-35) of Example 1 and the compound (1-66) of Example 2 was measured by a high-sensitivity differential scanning calorimeter (DSC3100SA, manufactured by Bruker AXS). Further, EBL-1 (see Patent Document 1) having the following structure, which is a compound having a high glass transition temperature, was also measured by the same method. The results of the measured glass transition temperature are summarized in Table 1.

The glass transition temperature of compound (1-35) is 190 ° C., and the glass transition temperature of compound (1-66) is as high as 155 ° C., indicating that the thin film state is stable. In addition, the glass transition temperature of compound (1-35) is higher than that of EBL-1, and by using compound (1-35) instead of EBL-1, a device with better thermal stability can be manufactured. Is.

<Measurement of work function>
Using the compound (1-35) of Example 1 and EBL-1, a thin-film deposition film having a thickness of 100 nm was produced on an ITO substrate, and an ionization potential measuring device (Sumitomo Heavy Industries, Ltd., PYS-202). ) The measurement results of the work function are summarized in Table 2.

The compound (1-35) of Example 1 shows a suitable energy level as compared with the work function of a hole transport material such as a carbazole compound, which is regarded as a suitable material, from 5.3 to 6.0 eV. It can be seen that it has a good hole transport capacity.

<Evaluation of hole transport characteristics>
An ITO electrode was previously formed on a glass substrate as a transparent anode, and molybdenum oxide was formed as a hole injection layer to a thickness of 50 nm by a vacuum vapor deposition method. The compound (1-35) of Example 1 was formed into a film by a vacuum vapor deposition method so as to have a diameter of 100 nm. Subsequently, 100 nm of Al was vapor-deposited as a cathode to produce a hole-only element (HOD).

This was heated in a glove box under a nitrogen atmosphere on a hot plate at 180 ° C for 3 hours, and an unheated element was created. A voltage was applied to each element, and the SCLC (space charge limiting current) equation was fitted to the current-voltage curve in which the current flowed with a forward bias, and the mobility was measured. For comparison, the EBL-1 was also manufactured and measured under the same conditions. Table 3 summarizes the mobility and the leakage current when -3V is applied.

The compound (1-35) of Example 1 has suppressed decrease in mobility due to heating as compared with EBL-1. Even at the current density when -3V is applied, the leakage current of compound (1-35) is significantly suppressed as compared with EBL-1. This is because the compound having an indenophenanthrene ring structure has a good hole transporting ability and a higher glass transition temperature.

As described above, the organic thin film containing the compound having the indenophenanthrene ring structure represented by the general formula (1) of the present invention is an organic thin film having excellent heat resistance and charge transport property, and can be used for various photoelectric conversion elements. Applicable.

[Example 3]
<Manufacturing of photoelectric conversion element>
As shown in FIG. 1, the photoelectric conversion element is formed by depositing a first buffer layer 3, a photoelectric conversion layer 4, and a metal cathode 5 in this order on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. Made.

Specifically, the glass substrate 1 on which ITO, which is a transparent anode 2, is formed, is ultrasonically cleaned in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 200 ° C. for 10 minutes. rice field. Then, after performing UV ozone treatment for 15 minutes, the glass substrate with ITO was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.0001 Pa or less. Subsequently, the compound (1-35) of Example 1 was deposited as the first buffer layer 3 so as to cover the transparent anode 2 so that the film thickness was 5 nm. On the first buffer layer 3, a p-type semiconductor (SubPC) having the following structural formula and an n-type semiconductor (C60) having the following structural formula are placed as the photoelectric conversion layer 4, and the vapor deposition rate ratio is SubPC: C60 = 50: 50. Two-way vapor deposition was performed at a thin-film deposition rate of 100 nm. Finally, gold was formed on the photoelectric conversion layer 4 as a metal cathode 5 so as to have a film thickness of 100 nm.

<Evaluation of photoelectric conversion element>
The spectral sensitivity and bright current of the manufactured organic photoelectric conversion element were measured using a spectral sensitivity measuring device under the following measurement conditions. The irradiation intensity at a specific wavelength at the time of measurement was calibrated using a Si photodiode (S1337-1010BQ, manufactured by Hamamatsu Photonics). For dark current, the spectral radiation intensity to the photoelectric conversion element was set to zero, and the current value was measured under the same bias conditions. The measurement results are summarized in Table 4.
(Measurement condition)
Device: Spectral sensitivity measuring device SM-250A (manufactured by Spectrometer Co., Ltd.)
Light source: Xenon 150W
Spectral irradiance: 2.0 mW / cm ² (550 nm)
Effective irradiation area: 10 x 10 mm
Light receiving area: 0.04 cm ²
In-plane non-uniformity: within ± 5% Source meter: Caseley 2635B (manufactured by KEITHLEY)
Applied bias: -1 to -3V

[Comparative Example 1]
For comparison, in Example 3, a photoelectric conversion element was produced in the same manner except that the EBL-1 was used instead of the compound (1-35) as the material of the first buffer layer 2, and the electrical characteristics were evaluated. bottom. The measurement results are summarized in Table 4.

As shown in Table 4, the dark current of the element of Example 3 when a bias of -3V is applied is 1/40, which is significantly lower than that of the element of Comparative Example 1. Also, the conversion efficiency EQE when a bias of -3V is applied is 64%, which is 6% higher than that of Comparative Example 1 of 58%. Even when a bias of -1V and -2V is applied to the device, the device of Example 3 shows a lower dark current and a higher conversion efficiency EQE than the device of Comparative Example 1. This indicates that the dark current characteristics and conversion efficiency of the photoelectric conversion element can be significantly improved due to the high electron blocking property and good hole transport property of the compound having an indenophenanthrene ring structure.

Since the organic thin film of the present invention having high heat resistance and good charge mobility can be applied to various photoelectric conversion elements, a photoelectric conversion element having good dark current characteristics and conversion efficiency, particularly an image pickup element, and an image pickup element thereof are used. Can provide an optical sensor.

Claims

It is an organic thin film used for a photoelectric conversion element, and the organic thin film is an organic thin film containing a compound having an indenophenanthrene ring structure represented by the following general formula (1).

(In the formula, A is a single-bonded, divalently substituted or unsubstituted aromatic hydrocarbon group, a divalent substituted or unsubstituted aromatic heterocyclic group, or a divalent substituted or unsubstituted condensed polycyclic aromatic group. Represents the group
Ar 1 and Ar 2 may be the same or different from each other, and may be a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group. Represent,
A, Ar 1 and Ar 2 may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.
R 1 to R 11 may be the same or different from each other, and may have a hydrogen atom, a hydrocarbon atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, and a substituent, and have 1 to 6 carbon atoms. Linear or branched alkyl group, cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, and linear chain having 2 to 6 carbon atoms which may have a substituent. Alternatively, a branched alkenyl group, a linear or branched alkyloxy group having 1 to 6 carbon atoms which may have a substituent, and a carbon atom having 5 to 10 which may have a substituent may have a substituent. Represents a cycloalkyloxy group, 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.
R 1 to R 11 may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring.
R 12 and R 13 may be the same or different from each other, and may have a substituent. Even if they have a linear or branched alkyl group having 1 to 6 carbon atoms and a substituent. A good cycloalkyl group having 5 to 10 carbon atoms, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, and a carbon atom which may have a substituent. 1 to 6 linear or branched alkyloxy groups, cycloalkyloxy groups having 5 to 10 carbon atoms which may have substituents, substituted or unsubstituted aromatic hydrocarbon groups, substituted or absent. Represents a substituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group or a substituted or unsubstituted aryloxy group.
R 12 and R 13 may be bonded to each other via a single-bonded, substituted or unsubstituted methylene group, oxygen atom or sulfur atom to form a ring. )
The organic thin film according to claim 1, wherein the compound having an indenophenanthrene ring structure represented by the general formula (1) is a compound having an indenophenanthrene ring structure represented by the following general formula (2).

(In the formula, A and R 1 to R 13 are the same as the definitions of A and R 1 to R 13 in the general formula (1), and R 14 to R 21 are R 1 to R in the general formula (1). It is the same as the definition of 11. )
The organic thin film according to claim 1, wherein the compound having an indenophenanthrene ring structure represented by the general formula (1) is a compound having an indenophenanthrene ring structure represented by the following general formula (3).

(In the formula, R 1 to R 13 are the same as the definitions of R 1 to R 13 in the general formula (1), and R 14 to R 20 are the definitions of R 1 to R 11 in the general formula (1). It is the same, and Ar is the same as the definition of Ar 1 and Ar 2 in the general formula (1).)
A photoelectric conversion element in which at least an anode, a buffer layer, a photoelectric conversion layer, and a cathode are laminated in this order, and has a layer made of an organic thin film according to any one of claims 1 to 3.
The photoelectric conversion element according to claim 4, wherein the layer made of the organic thin film is a buffer layer.
The photoelectric conversion element according to claim 4, wherein the layer made of the organic thin film is a photoelectric conversion layer.
An image pickup device having the photoelectric conversion element according to any one of claims 4 to 6.