JP2022129432A - Boron chelate compound, near-infrared light absorbing material, thin film, photoelectric conversion element, and imaging element - Google Patents

Abstract

To provide an organic compound, an organic thin film, and a photoelectric conversion element that have high thermal stability, have a main absorption band in a near-infrared region of 900 nm or more, and exhibit high photoelectric conversion characteristics even in the wavelength region of 1,000 nm or more.SOLUTION: There is provided a compound represented by the following formula (1) (R1 to R4 each independently represent a hydrogen atom, an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom. m represents an integer from 1 to 3, and A represents a benzene ring or a naphthalene ring).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to novel compounds having a boron chelate structure, photoelectric conversion devices, photosensors, and imaging devices. In particular, it relates to a photoelectric conversion element having a main absorption band in the near-infrared region and its use.

Near-infrared light absorbing materials having an absorption band in the wavelength region of 700 to 2,500 nm are used in optical information recording media such as CD-R (Compact Disk-Recordable); thermal CTP (Computer To Plate), flash toner fixing, laser Printing applications such as thermal recording; It is used in various applications such as heat shielding films, and is also used in PDPs (Plasma Display Panels), etc., using the property of selectively absorbing light in a specific wavelength range. It is also used in near-infrared light cut filters and films for controlling plant growth. Furthermore, printed matter using near-infrared light-absorbing ink in which near-infrared light-absorbing dyes are dissolved or dispersed in a solvent is difficult to recognize visually, and can only be read with a near-infrared light detector or the like. is possible, it is used, for example, for printed matter for the purpose of preventing counterfeiting.

In addition, unlike ultraviolet light and X-rays, near-infrared light is safe light with almost no adverse effects on the human body. , it is possible to image invisible information in vivo without being affected by hemoglobin or water. Furthermore, by using near-infrared light with a wavelength exceeding 1,000 nm, it is possible to apply it to foreign matter diagnosis in the fields of food and agriculture, and defect observation of silicon wafers.

Inorganic materials and organic materials are known as near-infrared light absorbing materials for such invisible image formation. Since it has an absorption band not only in light but also in the near-infrared region of about 780 to 950 nm, sensors using this are widely used.
On the other hand, since silicon does not have a light absorption band at wavelengths of 1,000 nm or more, indium gallium arsenide (InGaAs) is a typical example for the development of sensors that utilize near-infrared light with wavelengths over 1,000 nm. compound semiconductors are used as near-infrared absorbing materials. However, these inorganic materials generally have a low ability to absorb light in the near-infrared region, and a large amount of infrared light-absorbing material per unit area is required to form an invisible image. Therefore, when forming a visible image on top of an invisible image formed using an inorganic infrared light absorbing material, the unevenness of the surface of the invisible image affects the surface shape of the visible image. Met.

On the other hand, organic near-infrared light absorbing materials have a high ability to absorb light in the near-infrared region, and can form an invisible image with a small amount of near-infrared absorbing material per unit area. This does not cause the inconvenience that occurs when using a near-infrared light absorbing material. In addition, since the molecular structure of organic near-infrared absorbing materials can be flexibly designed, it is possible to create materials that have an absorption band at the wavelength of the target light, so interference of light with unnecessary wavelengths is possible. can be suppressed. Therefore, up to now, many organic near-infrared light absorbing materials have been investigated.

If an organic material that efficiently absorbs near-infrared light can be developed, the range of applications for electronic devices using near-infrared light as described above will expand. Therefore, organic near-infrared light absorbing materials have a sufficient absorption band in the near-infrared light region, and are necessary for processes such as electrode formation during organic electronic device manufacturing and introduction of semiconductor sealing layers. Sufficient robustness to accommodate temperatures (usually 120-180° C.) is required. However, cyanine dyes, squarylium dyes, diimmonium dyes, and the like, which exhibit an absorption band in the near-infrared region, are all poor in fastness, and their applications are limited.

Under such circumstances, in recent years, studies on boron-dipyrromethene (hereinafter referred to as "BODIPY") compounds showing an absorption band in the near-infrared wavelength region have been actively conducted. Non-Patent Documents 1 and 2 show that a dibenzo-BODIPY compound in which a benzene ring is fused to the pyrrole ring of the BODIPY skeleton exhibits an absorption band shifted to a longer wavelength than a non-fused BODIPY compound, and that the BO chelate It is described that a longer wavelength shift can be achieved by forming a condensed ring structure by chemistry, and Patent Document 1 describes that the compound can be used in optical recording media as a near-infrared light absorbing material. In addition, Patent Documents 2 to 4 report on organic thin films using compounds having the condensed ring structure.

Furthermore, Patent Document 5 describes a near-infrared light-absorbing dye that exhibits photoelectric conversion characteristics with respect to light with a wavelength of 900 nm or more and that can be sublimated. However, the above-mentioned dyes have low photoelectric conversion characteristics for light with a wavelength exceeding 1,000 nm, and the absorption wavelength of near-infrared light is limited. be done. Therefore, there is a demand for the development of near-infrared photoelectric conversion materials that exhibit high light absorption and photoelectric conversion characteristics even at wavelengths exceeding 1,000 nm.

JP-A-1999-255774 JP 2012-199541 A JP 2016-166284 A WO2013/035303 WO2020/162345

Chem. Soc. Rev. , 2014, 43, 4778-4823 Chem. Rev. , 2007, 107, 4891-4932

It is an object of the present invention to provide a photocatalyst that has high thermal stability, has a main absorption band in the near-infrared region of 900 nm or more that can be easily used in organic electronic devices, etc., and has high photoelectric properties even in the wavelength region exceeding 1,000 nm. An object of the present invention is to provide a compound, an organic thin film, and a photoelectric conversion device that exhibit conversion characteristics.

The inventors of the present invention have studied to solve the above problems, and as a result, have found that the above problems can be solved by using a BODIPY compound having a specific structure, and have completed the present invention.
That is, the present invention
[1] General formula (1) below

(In Formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom. m represents an integer of 1 to 3. A represents benzene represents a ring or a naphthalene ring),
[2] The compound according to [1] above, wherein at least one of R ¹ to R ⁴ is an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom;
[3] The compound according to [2] above, wherein at least one of R ¹ to R ⁴ is a halogen atom;
[4] The compound according to [2] above, wherein at least two of R ¹ to R ⁴ are an aromatic hydrocarbon group or a halogen atom;
[5] The compound according to any one of [1] to [4] above, wherein A is a benzene ring;
[6] A near-infrared light absorbing material containing the compound according to any one of [1] to [5] above,
[7] An organic thin film containing the compound according to any one of [1] to [5] above,
[8] A photoelectric conversion device comprising the organic thin film according to [7] above,
[9] An optical sensor comprising the photoelectric conversion device according to [8] above, and [10] An imaging device comprising the photoelectric conversion device according to [8] above,
Regarding.

An organic thin film containing the novel compound of the present invention has a main absorption band in the near-infrared region. A near-infrared photoelectric conversion device is realized by using the compound and/or the thin film. The compound can be used for various organic electronic devices.

FIG. 1 shows a cross-sectional view illustrating an embodiment of the photoelectric conversion element of the present invention. FIG. 2 shows the measurement results of the absorption spectrum of the organic thin film obtained using the compound of the present invention.

The present invention will be described in detail below. The descriptions of the constituent elements described herein are based on representative embodiments and examples of the invention, but the invention is not limited to such embodiments and examples. In this specification, the near-infrared region means a light wavelength region in the range of 750 to 2500 nm, and the near-infrared light absorbing material has an absorption band mainly in the near-infrared region. means material.

The compound of the present invention is represented by the following formula (1).

In formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom.

The alkyl group represented by R ¹ to R ⁴ in formula (1) is not limited to any of linear, branched and cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms.
Specific examples of alkyl groups represented by R ¹ to R ⁴ in formula (1) include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, iso-butyl group, t-butyl group and n-pentyl. group, n-hexyl group, n-octyl group, n-decyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-cetyl group, n-heptadecyl group, 2-ethylhexyl group, 3 -ethylheptyl group, 4-ethyloctyl group, 2-butyloctyl group, 3-butylnonyl group, 4-butyldecyl group, 2-hexyldecyl group, 3-octylundecyl group, 4-octyldodecyl group, 2-octyldodecyl group, 2-decyltetradecyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group and cyclohexyl group. The alkyl group represented by R ¹ to R ⁴ in formula (1) may have a substituent, and the substituent that may have is not particularly limited.
Alkyl groups represented by R ¹ to R ⁵ in formula (1) include methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, t-butyl, n-pentyl, n -hexyl group, 2-ethylhexyl group or cyclohexyl group is preferred, and methyl group, ethyl group, t-butyl group or cyclohexyl group is more preferred.

The aromatic hydrocarbon group represented by R ¹ to R ⁴ in formula (1) is a residue obtained by removing one hydrogen atom from an aromatic ring of an aromatic hydrocarbon compound. Specific examples thereof include a phenyl group, biphenyl group, tolyl group, indenyl group, naphthyl group, anthryl group, fluorenyl group, pyrenyl group, phenanthyl group, mestyle group and the like. The aromatic hydrocarbon group represented by R ¹ to R ⁴ in Formula (1) may have a substituent, and the substituent that may have is not particularly limited.
The aromatic hydrocarbon group represented by R ¹ to R ⁴ in formula (1) is preferably a phenyl group, a biphenyl group, a naphthyl group, a tolyl group or a mestyle group, more preferably a phenyl group or a tolyl group.

The heterocyclic group represented by R ¹ to R ⁴ in formula (1) is a residue obtained by removing one hydrogen atom from the heterocyclic ring of a heterocyclic compound, and specific examples thereof include furanyl group, thienyl group, thienothienyl pyrrolyl group, imidazolyl group, thiazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, indolyl group, benzopyrazyl group, benzopyrimidyl group, benzothienyl group, benzothiazolyl group, pyridinothiazolyl group, benzimidazolyl group, pyri dinoimidazolyl group, benzoxazolyl group, pyridinooxazolyl group, benzothiadiazolyl group, pyridinothiadiazolyl group, benzoxadiazolyl group, pyridinooxadiazolyl group, carbazolyl group, phenoxazinyl group and pheno A thiazinyl group and the like can be mentioned. The heterocyclic group represented by R ¹ to R ⁴ in Formula (1) may have a substituent, and the substituent that may have is not particularly limited.
The heterocyclic group represented by R ¹ to R ⁴ in formula (1) is preferably a thienyl group, a thienotienyl group, a pyrrolyl group, a pyridyl group, a pyrazyl group or a benzothienyl group, more preferably a thienyl group, a pyridyl group or a benzothienyl group. preferable.

Halogen atoms represented by R ¹ to R ⁴ in formula (1) include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, preferably a fluorine atom or a chlorine atom.
R ¹ to R ⁴ in formula (1) are all hydrogen atoms, or R ¹ and R ⁴ are hydrogen atoms and one of R ² and R ³ is a hydrogen atom, an alkyl group, or an aromatic hydrocarbon A hydrogen group, a heterocyclic group or a halogen atom and the other is preferably an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom, all of which are hydrogen atoms, or R ¹ and R ⁴ are More preferably, one of R ² and R ³ is a hydrogen atom, an aromatic hydrocarbon group or a halogen atom and the other is an aromatic hydrocarbon group or a halogen atom.

m in formula (1) represents an integer of 1 to 3, preferably 1 or 2;

In Formula (1), A represents a benzene ring or a naphthalene ring. The benzene ring or naphthalene ring represented by A may have a substituent, and the substituent that may have is not particularly limited. Examples of the substituent include an aromatic hydrocarbon group, a heterocyclic A group and a halogen atom are preferred, and a halogen atom is more preferred.
A in formula (1) is preferably a benzene ring, more preferably an unsubstituted benzene ring.

Next, a method for synthesizing the compound of the present invention will be described. The compound represented by formula (1) can be synthesized, for example, by the synthesis method shown in the scheme below. First, a hydroxythiophene compound represented by formula (S-1) is methylated using methyl iodide to obtain a methoxythiophene intermediate represented by formula (M-1). Subsequently, a hydrazide intermediate represented by the formula (M-2) is obtained by reaction with hydrazine monohydrate. The intermediate represented by formula (M-2) and the acetophenone derivative represented by formula (S-2) are subjected to dehydration condensation to obtain a hydrazone intermediate represented by formula (M-3). Thereafter, a diketone intermediate represented by the formula (M-4) is obtained by a denitrification rearrangement reaction using iodobenzene diacetate, and the intermediate (M-4) is reacted with ammonium acetate to form the formula (M-5). ) as a dipyrromethene intermediate. Finally, the methyl group on the hydroxyl group is deprotected to form an intramolecular BO bond to synthesize the compound represented by formula (1). Starting compounds represented by formulas (S-1) and (S-2) can be synthesized by using known methods.
R ¹ to R ⁴ , m and A in the following synthesis schemes have the same meanings as R ¹ to R ⁴ , m and A in Formula (1).

Specific examples of the compound represented by formula (1) are shown below, but the present invention is not limited thereto. It should be noted that the structural formula shown as a specific example merely represents one resonance structure, and is not limited to the illustrated resonance structure.

The near-infrared light absorbing material of the present invention contains the compound represented by the above formula (1).
The content of the compound represented by formula (1) in the near-infrared light-absorbing material of the present invention is as long as the near-infrared light absorption ability required in the application using the near-infrared light-absorbing material is expressed. Although not particularly limited, it is usually 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.
The near-infrared light-absorbing material of the present invention includes a compound other than the compound represented by formula (1) (for example, a near-infrared light-absorbing material (dye) other than the compound represented by formula (1), etc.) or an additive You may use an agent etc. together. The compounds, additives, and the like that can be used in combination are not particularly limited as long as they exhibit the near-infrared light absorbing ability required in the application using the near-infrared light absorbing material.

The organic thin film of the present invention contains the compound represented by the above formula (1).
The organic thin film of the present invention can be produced by a general dry film-forming method or wet film-forming method. Vacuum processes such as resistance heating vapor deposition, electron beam vapor deposition, sputtering and molecular lamination, solution processes such as casting, spin coating, dip coating, blade coating, wire bar coating, spray coating, and inkjet printing. , printing methods such as screen printing, offset printing, letterpress printing, and soft lithography techniques such as microcontact printing.
For the formation of an organic thin film of a general near-infrared light-absorbing material, a process in which a compound is applied in a solution state is desired from the viewpoint of ease of processing. From such a point of view, the development of highly soluble organic materials that can be applied to solution processes is desired.

On the other hand, in the case of organic electronic devices in which organic films are laminated, it is often difficult to select solvent conditions in which the coating solution does not attack the underlying organic films. In order to realize such a layered structure, it is suitable to use a vapor deposition material that can be used in dry film formation methods such as resistance heating vapor deposition. Therefore, a near-infrared light-absorbing material that has a main absorption wavelength in the near-infrared region and that can be vapor-deposited is preferably used as an organic electronic material.

When stacking organic films, a method combining a plurality of the above methods may be employed for forming each layer. The thickness of each layer cannot be limited because it depends on the resistance value and charge mobility of each substance, but it is usually in the range of 0.5 to 5,000 nm, preferably in the range of 1 to 1,000 nm. More preferably, it is in the range of 5 to 500 nm.

The molecular weight of the compound represented by the formula (1) is, for example, 1,500 or less when the organic layer containing the compound represented by the formula (1) is intended to be formed by a vapor deposition method and used. is preferably 1,200 or less, and even more preferably 1,000 or less. The lower limit of the molecular weight is the minimum molecular weight value that formula (1) can take.
Incidentally, the compound represented by the formula (1) may be formed into a film by a coating method regardless of the molecular weight. If a coating method is used, it is possible to form a film even with a compound having a relatively large molecular weight.
Incidentally, the molecular weight in this specification means the value calculated by the EI-GCMS method.

[Photoelectric conversion element]
Since the compound represented by the above formula (1) is a compound having near-infrared light absorption properties, it is suitably used in a near-infrared photoelectric conversion device. In particular, the compound represented by formula (1) above can be used for the photoelectric conversion layer in the photoelectric conversion element of the present invention. In the device, it is preferable to use a material having sufficient light absorption characteristics and photoelectric conversion characteristics with respect to the light wavelength of the light source. The wavelength range of the irradiation light used as the light source is preferably 800 to 1,400 nm, more preferably 900 to 1,400 nm, even more preferably 1,000 to 1,400 nm. Here, the near-infrared photoelectric conversion element includes a near-infrared light sensor, an organic image sensor, a near-infrared light image sensor, and the like.
In addition, the maximum absorption of the absorption band in this specification means the value of the wavelength at which the absorbance is maximum in the absorbance spectrum measured by the absorption spectrum measurement, and the maximum absorption wavelength (λmax) is the highest among the maximum absorption. It means maximum absorption on the long wavelength side.

A photoelectric conversion element is an element in which a photoelectric conversion portion (film) is arranged between a pair of opposing electrode films, and light is incident on the photoelectric conversion portion from above the electrode films. The photoelectric conversion portion generates electrons and holes in response to the incident light, and a semiconductor device reads out a signal corresponding to the charge and indicates the amount of incident light corresponding to the absorption wavelength of the photoelectric conversion film portion. is. A readout transistor may be connected to the electrode film on the side where light does not enter. If a photoelectric conversion element placed closer to the light source does not block (transmit) the absorption wavelength of the photoelectric conversion element placed behind it when viewed from the light source side, a plurality of photoelectric conversion elements are stacked. may be used.

The photoelectric conversion element of the present invention uses the compound represented by the formula (1) as a constituent material of the photoelectric conversion portion.
The photoelectric conversion part includes one or more selected from the group consisting of a photoelectric conversion layer, an electron transport layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an anti-crystallization layer, an interlayer contact improving layer, and the like. It is often composed of an organic thin film layer other than the photoelectric conversion layer. Although the compound represented by the formula (1) of the present invention can be used in a layer other than the photoelectric conversion layer, it is preferably used as an organic thin film layer of the photoelectric conversion layer. The photoelectric conversion layer may be composed only of the compound represented by the formula (1), but in addition to the compound represented by the formula (1), it may contain a known near-infrared light absorbing material or others. You can

The electrode film used in the photoelectric conversion element of the present invention is formed when the photoelectric conversion layer included in the photoelectric conversion part described later has a hole-transport property, or when the organic thin film layer other than the photoelectric conversion layer has a hole-transport property. When it is a hole-transporting layer, it plays a role of extracting and collecting holes from the photoelectric conversion layer or other organic thin film layer, and when the photoelectric conversion layer contained in the photoelectric conversion part has an electron-transporting property. Alternatively, when the organic thin film layer is an electron transport layer having an electron transport property, it plays a role of extracting electrons from the photoelectric conversion layer or other organic thin film layers and ejecting them. Therefore, the material that can be used as the electrode film is not particularly limited as long as it has a certain degree of conductivity. is preferably selected in consideration of Examples of materials that can be used as electrode films include conductive metal oxides such as tin oxide (NESA), indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); gold, silver, platinum, chromium, and aluminum. , metals such as iron, cobalt, nickel and tungsten; inorganic conductive substances such as copper iodide and copper sulfide; conductive polymers such as polythiophene, polypyrrole and polyaniline; and carbon. If necessary, a plurality of these materials may be mixed and used, or two or more layers of electrode films made of different materials may be laminated. The conductivity of the material used for the electrode film is also not particularly limited as long as it does not interfere with the light reception of the photoelectric conversion element more than necessary. For example, a conductive ITO film with a sheet resistance value of 300 Ω/□ or less functions well as an electrode film, but substrates with an ITO film having a conductivity of several Ω/□ are also available on the market. Therefore, it is desirable to use a substrate having such high conductivity. Although the thickness of the ITO film (electrode film) can be arbitrarily selected in consideration of conductivity, it is usually about 5 to 500 nm, preferably about 10 to 300 nm. Methods for forming a film such as ITO include conventionally known vapor deposition methods, electron beam methods, sputtering methods, chemical reaction methods, coating methods, and the like. If necessary, the ITO film provided on the substrate may be subjected to UV-ozone treatment, plasma treatment, or the like.

Materials for the transparent electrode film used for at least one of the light incident sides of the electrode film include ITO, IZO, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, and AZO (Al-doped zinc oxide). , GZO (gallium-doped zinc oxide), TiO ₂ , FTO (fluorine-doped tin oxide), and the like. The transmittance of light incident through the transparent electrode film at the absorption peak wavelength of the photoelectric conversion layer is preferably 60% or more, more preferably 80% or more, and particularly preferably 95% or more. .

When a plurality of photoelectric conversion layers with different wavelengths to be detected are stacked, the electrode film (this is an electrode film other than the pair of electrode films described above) used between each photoelectric conversion layer is the same as that of each photoelectric conversion layer It is necessary to transmit light other than light having a wavelength to be detected by the electrode film, and it is preferable to use a material that transmits 90% or more of the incident light for the electrode film, and a material that transmits 95% or more of the light is used. is more preferred.

The electrode film is preferably produced plasma-free. By forming these electrode films in a plasma-free manner, the influence of plasma on the substrate on which the electrode films are provided is reduced, and the photoelectric conversion characteristics of the photoelectric conversion element can be improved. Here, "plasma-free" means that plasma is not used when forming the electrode film, or the distance from the plasma generation source to the substrate is 2 cm or more, preferably 10 cm or more, and more preferably 20 cm or more, so that the plasma reaches the substrate. means a state in which the generated plasma is reduced.

Examples of apparatuses that do not use plasma when forming an electrode film include an electron beam vapor deposition apparatus (EB vapor deposition apparatus) and a pulse laser vapor deposition apparatus. A method of forming a transparent electrode film using an EB vapor deposition device is called an EB vapor deposition method, and a method of forming a transparent electrode film using a pulse laser vapor deposition device is called a pulse laser vapor deposition method.

As an apparatus capable of realizing a state in which plasma can be reduced during film formation, for example, a facing target type sputtering apparatus, an arc plasma vapor deposition apparatus, and the like can be considered.

When a transparent conductive film is used as an electrode film (for example, a first conductive film), a DC short circuit or an increase in leakage current may occur. One of the reasons for this is that fine cracks generated in the photoelectric conversion layer are covered with a dense film such as TCO (Transparent Conductive Oxide), and the electrode film on the opposite side of the first conductive film (second conductive film ) is considered to be due to an increase in conduction between Therefore, when a material such as Al having a relatively inferior film quality is used for the electrode, an increase in leakage current is less likely to occur. By controlling the film thickness of the electrode film according to the film thickness (crack depth) of the photoelectric conversion layer, an increase in leakage current can be suppressed.

Generally, when the conductive film is made thinner than a predetermined thickness, the resistance value abruptly increases. The sheet resistance of the conductive film in the photoelectric conversion element for a photosensor, which is one of the present embodiments, is usually 100 to 10000Ω/□, and the film thickness can be appropriately set. Also, the thinner the transparent conductive film, the less light it absorbs, and generally the higher the light transmittance. When the light transmittance is high, the amount of light absorbed by the photoelectric conversion layer is increased and the photoelectric conversion performance is improved, which is very preferable.

The photoelectric conversion part of the photoelectric conversion element of the present invention may include a photoelectric conversion layer and an organic thin film layer other than the photoelectric conversion layer. An organic semiconductor film is generally used for the photoelectric conversion layer that constitutes the photoelectric conversion part, and the organic semiconductor film may be a single layer or a plurality of layers. type organic semiconductor films, or mixed films thereof (bulk heterostructures) are used. On the other hand, in the case of a plurality of layers, the number of layers is about 2 to 10, and a structure in which either a p-type organic semiconductor film, an n-type organic semiconductor film, or a mixed film thereof (bulk heterostructure) is laminated. and a buffer layer may be inserted between the layers. When the photoelectric conversion layer is formed from the mixed film described above, the compound represented by the formula (1) of the present invention is used as the p-type semiconductor material, and general fullerene or a derivative thereof is used as the n-type semiconductor material. It is preferable to use

In the photoelectric conversion device of the present invention, the organic thin film layer other than the photoelectric conversion layer constituting the photoelectric conversion part is a layer other than the photoelectric conversion layer, such as an electron transport layer, a hole transport layer, an electron blocking layer, and a hole blocking layer. (Hereinafter, the electron blocking layer and the hole blocking layer are collectively referred to as "carrier blocking layer".), the layer is used as a crystallization prevention layer, an interlayer contact improving layer, or the like. In particular, by using one or more thin film layers selected from the group consisting of an electron-transporting layer and a hole-transporting layer, it is possible to obtain an element that efficiently converts even weak light energy into electrical signals, which is preferable.

In addition, in imaging devices, it is generally thought that performance improvement is aimed at by reducing dark current for the purpose of high contrast and power saving. These carrier block layers are generally used in the field of organic electronic devices, and each have a function of controlling the reverse transfer of holes or electrons in the constituent films of the device.

The electron transport layer plays a role of transporting electrons generated in the photoelectric conversion layer to the electrode film and a role of blocking the movement of holes from the electrode film to which the electrons are transported to the photoelectric conversion layer. The hole transport layer plays a role of transporting generated holes from the photoelectric conversion layer to the electrode film and a role of blocking the movement of electrons from the electrode film to which the holes are transported to the photoelectric conversion layer. The electron blocking layer plays a role of preventing movement of electrons from the electrode film to the photoelectric conversion layer, preventing recombination within the photoelectric conversion layer, and reducing dark current. The hole blocking layer has a function of preventing holes from moving from the electrode film to the photoelectric conversion layer, preventing recombination in the photoelectric conversion layer, and reducing dark current.

Although FIG. 1 shows a typical element structure of the photoelectric conversion element of the present invention, the present invention is not limited to this structure. In the embodiment of FIG. 1, 1 is an insulating part, 2 is one electrode film (upper electrode film), 3 is an electron blocking layer, 4 is a photoelectric conversion layer, 5 is a hole blocking layer, and 6 is the other electrode film. (lower electrode film) and 7 respectively represent an insulating substrate or other organic photoelectric conversion element. Although a readout transistor is not shown in the figure, it may be connected to two or six electrode films. may be formed outside the electrode film. Light is incident on the organic photoelectric conversion element from either the top or the bottom, provided that the components other than the photoelectric conversion layer 4 do not extremely block the incidence of light of the main absorption wavelength of the photoelectric conversion layer. It can be from

A photoelectric conversion element having such a photoelectric conversion portion can be used as an optical sensor because it can read out as a signal an electric charge corresponding to the absorption amount of light of a wavelength irradiated from a light source of the photoelectric conversion portion. In particular, examples of applications as near-infrared light sensors include the observation of in vivo information using fluorescent substances.

Further, in the above optical sensor, when a large number of photoelectric conversion elements are arranged in an array, it is possible to obtain incident position information in addition to the amount of incident light, so that the optical sensor can be used as an imaging element. The reflected light of the light irradiated to the detection object from the light source arranged on the same side as the photoelectric conversion element, or the transmitted light of the light irradiated to the detection object from the light source arranged on the opposite side of the photoelectric conversion element is used as the photoelectric conversion element. By simultaneously reading out the amount of received light and the positional information as an electric signal from the light receiving section included, it becomes an imaging device. Imaging devices that use near-infrared light as a light source can be used for observation of veins in living organisms, diagnosis of foreign substances in the fields of food and agriculture, and the like.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. The structures of the compounds described in Synthesis Examples were determined by mass spectrometry and nuclear magnetic resonance spectroscopy (NMR) as necessary. In the examples, the molecular weight was measured using ISQ LT GC-MS (manufactured by Thermo Fisher Scientific), and the absorption spectrum was measured using UV-1700 (manufactured by Shimadzu Corporation). In addition, the applied measurement of the current voltage of the organic photoelectric conversion element was performed using PVL-3300 (manufactured by Asahi Spectrosco Co., Ltd.) under the irradiation conditions of an irradiation light intensity of 130 μW and a half value width of 20 nm. was used in the range from 350 to 1100 nm. In addition, compound (S-1) and compound (S-2), which are raw materials for synthesis, were synthesized according to the method described in “Organic Letters (2016), 18(4), 804-807.”.

Example 1 (Synthesis of the compound of the present invention represented by the following formula (1-1))
(Step 1) Synthesis of an intermediate compound represented by the following formula (M-1) In a flask, the compound represented by the formula (S-1) (15.0 g, 56.8 mmol) was added to DMF (300 mL). Dissolve and add potassium carbonate (15.7 g, 114 mmol), sodium iodide (4.26 g, 28.5 mmol) and methyl iodide (12, 1 g, 85.2 mmol) at room temperature, then stir at 80°C. and stirred for 3 hours. After the reaction solution obtained above was cooled to room temperature, it was poured into 1N hydrochloric acid (1 L) and stirred, and the resulting solid was collected by suction filtration. The obtained solid was washed with water and methanol to obtain an intermediate compound (14.5 g, 52.1 mmol, yield 91.7%) represented by formula (M-1).
The results of mass spectrometric measurement of the compound represented by formula (M-1) were as follows.
DI-MS: m/z = 278 [M] ⁺

(Step 2) Synthesis of an intermediate compound represented by the following formula (M-2) In a flask, an intermediate compound represented by the formula (M-1) synthesized in Step 1 (14.5 g, 52.1 mmol ) was suspended in ethanol (260 mL), hydrazine-hydrate (25.3 mL, 521 mmol) was added at room temperature, and the mixture was heated to 78° C. with stirring and refluxed for 6 hours. After cooling the reaction solution obtained above to room temperature, it was diluted with water (500 mL), and ethanol was distilled off by concentration under reduced pressure. Thereafter, the precipitated solid was collected by suction filtration and washed with water and methanol to obtain an intermediate compound represented by formula (M-2) (12.9 g, 46.4 mmol, yield 89.1%). got
The results of mass spectrometric measurement of the compound represented by formula (M-2) were as follows.
DI-MS: m/z = 278 [M] ⁺

(Step 3) Synthesis of an intermediate compound represented by the following formula (M-3) In a flask, an intermediate compound represented by the formula (M-2) synthesized in step 2 (12.0 g, 43.0 mmol ) and 4′-fluoro-2′-hydroxy-5′-phenylacetophenone (11.9 g, 51.6 mmol) were suspended in ethanol (215 mL), and the temperature was raised to 78° C. with stirring for 6 hours. refluxed. After cooling the reaction solution obtained above to room temperature, it was diluted with ethanol (300 mL), the resulting solid was collected by filtration under reduced pressure, and washed with water, methanol and a small amount of acetone to obtain the formula (M-3 ) was obtained (20.3 g, 41.5 mmol, yield 96.5%).
The results of mass spectrometric measurement of the compound represented by formula (M-3) were as follows.
DI-MS: m/z = 490 [M] ⁺

(Step 4) Synthesis of an intermediate compound represented by the following formula (M-4) In a flask, an intermediate compound represented by the formula (M-3) synthesized in step 3 (19.7 g, 40.2 mmol ) was suspended in toluene (400 mL) and the temperature was raised to 95° C. Then, while stirring, iodobenzene diacetate (19.4 g, 60.3 mmol) was gradually added over 10 minutes and the reaction was carried out for 1 hour. rice field. After cooling the reaction solution obtained above to room temperature, the organic solvent was distilled off under reduced pressure, and the resulting residual liquid was purified by column chromatography (mobile phase: chloroform) using silica gel as a stationary phase to obtain the formula ( An intermediate compound represented by M-4) (13.1 g, 28.5 mmol, yield 70.9%) was obtained.
The measurement results of mass spectrometry of the compound represented by formula (M-4) were as follows.
DI-MS: m/z = 460 [M] ⁺

(Step 5) Synthesis of an intermediate compound represented by the following formula (M-5) In a flask, an intermediate compound represented by the formula (M-4) synthesized in step 4 (4.88 g, 10.6 mmol ) was added to toluene (90 mL) and dissolved by heating to 60° C. with stirring, then ammonium acetate (81, 6 g, 1.06 mol) and water (10 mL) were added and the temperature was raised to reflux temperature. The reaction was further carried out for 2 hours. After the reaction solution obtained above was cooled to room temperature, water (500 mL) was added for liquid separation, and the aqueous layer was extracted twice using toluene (300 mL). Anhydrous magnesium sulfate was added to the mixture of the organic layer obtained by liquid separation and the extract obtained above to dry the mixture, and after removing the solid content by suction filtration, the organic solvent was distilled off under reduced pressure. By purifying the resulting residual solid by column chromatography using silica gel as a stationary phase, an intermediate compound represented by formula (M-5) (2.25 g, 2.59 mmol, yield 48.9%) was obtained. Obtained.
The measurement results of mass spectrometry of the compound represented by formula (M-5) were as follows.
DI-MS: m/z = 868 [M] ⁺

(Step 6) Synthesis of a compound represented by the following formula (1-1) In a flask, an intermediate compound (2.09 g, 2.41 mmol) represented by the formula (M-5) synthesized in step 5 was added. The mixture was dissolved in dichloroethane (340 mL), 1M boron tribromide dichloromethane solution (48.1 mL, 48.1 mmol) was added dropwise, and the mixture was stirred under reflux with heating for 12 hours. The reaction solution obtained above was poured into a saturated aqueous solution of sodium bicarbonate (1 L) and stirred for 1 hour. The precipitated solid was collected by suction filtration and washed with water, methanol and DMF. The resulting solid was purified by vacuum sublimation to obtain a compound represented by formula (1-1) (1.03 g, 1.22 mmol, yield 50.6%).
The measurement results of mass spectrometry of the compound represented by formula (1-1) were as follows.
DI-MS: m/z = 848 [M] ⁺

Example 2 (Synthesis of the compound of the present invention represented by the following formula (1-2))
(Step 7) Synthesis of an intermediate compound represented by the following formula (M-6) In a flask, the compound represented by the formula (S-2) (12.0 g, 37.5 mmol) was added to DMF (300 mL). Dissolve and add potassium carbonate (10.4 g, 75.0 mmol), sodium iodide (2.82 g, 18.8 mmol) and methyl iodide (8.00 g, 56.3 mmol) at room temperature, then stir. The temperature was raised to 80° C. and the mixture was further stirred for 3 hours. After the reaction solution obtained above was cooled to room temperature, it was poured into 1N hydrochloric acid (1 L) and stirred, and the resulting solid was collected by suction filtration. The obtained solid was washed with water and methanol to obtain an intermediate compound (11.2 g, 33.5 mmol, yield 89.2%) represented by formula (M-6).
The measurement results of mass spectrometry of the compound represented by formula (M-6) were as follows.
DI-MS: m/z = 334 [M] ⁺

(Step 8) Synthesis of an intermediate compound represented by the following formula (M-7) In a flask, an intermediate compound represented by the formula (M-6) synthesized in Step 7 (9.89 g, 29.6 mmol ) was suspended in ethanol (300 mL), hydrazine-hydrate (28.8 mL, 593 mmol) was added at room temperature, and the mixture was heated to 78° C. with stirring and refluxed for 6 hours. After cooling the reaction solution obtained above to room temperature, it was diluted with water (500 mL), and ethanol was distilled off by concentration under reduced pressure. Thereafter, the precipitated solid was collected by suction filtration and washed with water and methanol to give an intermediate compound represented by formula (M-7) (8.73 g, 26.1 mmol, yield 88.3%). got
The measurement results of mass spectrometry of the compound represented by formula (M-7) were as follows.
DI-MS: m/z = 334 [M] ⁺

(Step 9) Synthesis of an intermediate compound represented by the following formula (M-8) In a flask, an intermediate compound represented by the formula (M-7) synthesized in step 8 (7.85 g, 23.5 mmol ) and 4′-fluoro-2′-hydroxy-5′-phenylacetophenone (5.96 g, 25.9 mmol) were suspended and stirred in ethanol (400 mL), and the temperature was raised to 78° C. while stirring. Refluxed for hours. After cooling the reaction solution obtained above to room temperature, the reaction solution was diluted with ethanol (150 mL), the resulting solid was collected by vacuum filtration, and washed with water, methanol and a small amount of acetone to obtain the formula ( An intermediate compound represented by M-8) (12.2 g, 22.4 mmol, yield 95.5%) was obtained.
The results of mass spectrometric measurement of the compound represented by formula (M-8) were as follows.
DI-MS: m/z = 546 [M] ⁺

(Step 10) Synthesis of an intermediate compound represented by the following formula (M-9) In a flask, an intermediate compound represented by the formula (M-8) synthesized in Step 9 (12.2 g, 22.4 mmol ) was suspended in toluene (500 mL), the temperature was raised to 95° C., and iodobenzene diacetate (10.8 g, 33.6 mmol) was gradually added over 10 minutes, and the reaction was carried out for 1 hour. After cooling the reaction solution obtained above to room temperature, the organic solvent was distilled off under reduced pressure, and the resulting residual liquid was purified by column chromatography (mobile phase: chloroform) using silica gel as a stationary phase to obtain the formula ( An intermediate compound represented by M-9) (7.64 g, 14.8 mmol, yield 66.2%) was obtained.
The measurement results of mass spectrometry of the compound represented by formula (M-9) were as follows.
DI-MS: m/z = 516 [M] ⁺

(Step 11) Synthesis of an intermediate compound represented by the following formula (M-10) In a flask, an intermediate compound represented by the formula (M-9) synthesized in step 10 (3.23 g, 6.26 mmol ) was put into toluene (50 mL) and heated to 60° C. to dissolve, then ammonium acetate (96.3 g, 1.25 mol) and water (5 mL) were added and the temperature was raised to reflux temperature and further The reaction was carried out for 2 hours. After the reaction solution obtained above was cooled to room temperature, water (100 mL) was added for liquid separation, and the aqueous layer was extracted twice using toluene (200 mL). Anhydrous magnesium sulfate was added to the mixture of the organic layer obtained by liquid separation and the extract obtained above to dry the mixture, and after removing the solid content by suction filtration, the organic solvent was distilled off under reduced pressure. The resulting residual solid was purified by column chromatography using silica gel as a stationary phase to give an intermediate compound represented by formula (M-10) (1.44 g, 1.47 mmol, yield 47.0%). Obtained.
The results of mass spectrometric measurement of the compound represented by formula (M-10) were as follows.
DI-MS: m/z = 980 [M] ⁺

(Step 12) Synthesis of a compound represented by the following formula (1-2) In a flask, an intermediate compound (1.15 g, 1.17 mmol) represented by the formula (M-10) synthesized in step 11 was added. The mixture was dissolved in dichloroethane (100 mL), 1M boron tribromide dichloromethane solution (23.4 mL, 23.4 mmol) was added dropwise, and the mixture was stirred under reflux with heating for 12 hours. The reaction solution obtained above was poured into a saturated aqueous solution of sodium bicarbonate (500 mL) and stirred for 1 hour. The precipitated solid was collected by suction filtration and washed with water, methanol and DMF. The resulting solid was purified by vacuum sublimation to obtain a compound represented by formula (1-2) (0.32 g, 0.334 mmol, yield 28.5%).
The measurement results of mass spectrometry of the compound represented by formula (1-2) were as follows.
DI-MS: m/z = 960 [M] ⁺

Examples 3 and 4 (Preparation of organic thin film)
The compounds obtained in Examples 1 and 2 were vacuum-deposited by resistance heating on a pre-washed glass substrate to prepare an organic thin film of each compound. The thickness of the organic thin film (Example 3) obtained using the compound represented by formula (1-1) was 120 nm, and the organic thin film obtained using the compound represented by formula (1-2) ( The thickness of Example 4) was 100 nm.

(Absorption spectrum measurement of organic thin film)
The absorption spectrum of each organic thin film obtained in Examples 3 and 4 was measured. The results are shown in FIG. In addition, FIG. 2 is obtained by converting the measurement result per unit film thickness (nm). The maximum absorption wavelengths (λmax) of the organic thin films obtained in Examples 3 and 4 were 921 nm and 961 nm, respectively.

The organic thin films of the present invention obtained in Examples 3 and 4 have a maximum absorption wavelength in the long wavelength region of 900 nm or longer, and it is clear that they can efficiently absorb near infrared light in the vicinity of 800 to 1,000 nm. is.

Example 5 (Preparation of photoelectric conversion device using compound represented by formula (1-1) and evaluation thereof)
An organic thin film having a thickness of 120 nm of the compound represented by the formula (1-1) was formed on an ITO transparent conductive glass (manufactured by Geomatec, ITO film thickness of 150 nm) by resistance heating vacuum deposition to form a photoelectric conversion layer. . An aluminum film having a thickness of 100 nm was formed thereon by resistance heating vacuum deposition to produce a photoelectric conversion element of the present invention. Using ITO and aluminum as electrodes, the photocurrent responsiveness was measured when a voltage of 1 V was applied in a state where light irradiation of 1,000 nm and a half-value width of 20 nm was possible. ⁻¹⁰ A/cm ² , the current in bright light is 1.82×10 ⁻⁷ A/cm ² , and the value of the light-dark ratio (light current/dark current) calculated from the above measurement results is 1.80× was 10 ³ .

Example 6 (Preparation and Evaluation of Photoelectric Conversion Device Using Compound Represented by Formula (1-2))
A method according to Example 5 except that the compound represented by formula (1-2) was used instead of the compound represented by formula (1-1), and the thickness of the photoelectric conversion layer was 100 nm. Thus, a photoelectric conversion device of the present invention was produced. Using ITO and aluminum as electrodes, the photocurrent responsiveness was measured when a voltage of 1 V was applied in a state where light irradiation with a wavelength of 1,000 nm and a half-value width of 20 nm was possible. ⁻¹⁰ A/cm ² , the current in bright light is 3.18×10 ⁻⁷ A/cm ² , and the value of the light-dark ratio (light current/dark current) calculated from the above measurement results is 1.32× was 10 ³ .

Comparative Example 1 (Preparation of photoelectric conversion element using comparative compound and evaluation thereof)
Using a compound represented by the following formula (R-1) synthesized according to the method described in WO 2020/162345 instead of the compound represented by formula (1-1), and photoelectrically A photoelectric conversion element for comparison was produced in the same manner as in Example 5, except that the conversion layer had a thickness of 100 nm. Using ITO and aluminum as electrodes, the light-dark ratio (light current/dark current) calculated from the measurement results of the photocurrent response when a voltage of 1 V was applied in a state where light irradiation with a wavelength of 1,000 nm and a half-value width of 20 nm was possible. The value was 1.5 ^x 100.

Comparative Example 2 (Preparation and Evaluation of Photoelectric Conversion Device Using Comparative Compound)
Using a compound represented by the following formula (R-2) synthesized according to the method described in WO 2020/162345 instead of the compound represented by the formula (1-1), and photoelectrically A photoelectric conversion element for comparison was produced in the same manner as in Example 5, except that the conversion layer had a thickness of 100 nm. Using ITO and aluminum as electrodes, the light-dark ratio (light current/dark current) calculated from the measurement results of the photocurrent response when a voltage of 1 V was applied in a state where light irradiation with a wavelength of 1,000 nm and a half-value width of 20 nm was possible. The value was 8.6×10 ¹ .

Comparative Example 3 (Preparation of photoelectric conversion element using comparative compound and evaluation thereof)
Using a compound represented by the following formula (R-3) synthesized according to the method described in WO 2020/162345 instead of the compound represented by formula (1-1), and photoelectrically A photoelectric conversion element for comparison was produced in the same manner as in Example 5, except that the conversion layer had a thickness of 100 nm. Using ITO and aluminum as electrodes, the light-dark ratio (light current/dark current) calculated from the measurement results of the photocurrent response when a voltage of 1 V was applied in a state where light irradiation with a wavelength of 1,000 nm and a half-value width of 20 nm was possible. The value was 2.0×10 ¹ .

From the above results, the organic photoelectric conversion device containing the organic thin film using the compound of the present invention exhibits a higher contrast ratio in near-infrared light with a wavelength of 1,000 nm than the comparative organic photoelectric conversion device. It was found to be useful as a near-infrared light absorbing material for sensors.

The compound of the present invention exhibits good absorption properties in the near-infrared region, high heat resistance that can sufficiently withstand the device fabrication process, and good near-infrared photoelectric conversion properties, and is therefore useful as a material for organic electronic devices. is.

Claims (10)

Formula (1) below

(In Formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom. m represents an integer of 1 to 3. A represents benzene a ring or a naphthalene ring). 2. The compound according to claim 1, wherein at least one of ^R1 to ^R4 is an alkyl group, an aromatic hydrocarbon group, a heterocyclic group or a halogen atom. 3. The compound according to claim 2, wherein at least one of ^R1 to ^R4 is a halogen atom. 3. The compound according to claim 2, wherein at least two of ^R1 to ^R4 are aromatic hydrocarbon groups or halogen atoms. 5. A compound according to any one of claims 1 to 4, wherein A is a benzene ring. A near-infrared light absorbing material comprising the compound according to any one of claims 1 to 5. An organic thin film comprising the compound according to any one of claims 1 to 5. A photoelectric conversion device comprising the organic thin film according to claim 7 . An optical sensor comprising the photoelectric conversion element according to claim 8 . An imaging device comprising the photoelectric conversion device according to claim 8 .

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