JP2019080052A - Material for photoelectric conversion element and photoelectric conversion element - Google Patents

Abstract

To provide a material for a photoelectric conversion element which is a material of a block layer excellent in hole or electron leak prevention characteristics, hole or electron transport characteristics, heat resistance to process temperature, visible light transparency and the like, and to provide various electronic devices including a photoelectric conversion element containing the photoelectric conversion element material.SOLUTION: The material for photoelectric conversion elements contains a compound represented by the following Formula (1). (In Formula (1), Rand Reach independently represents an aromatic group or a heterocyclic group. One of Xand Xrepresents a sulfur atom or an oxygen atom, and the other represents a methine group.)SELECTED DRAWING: None

Description

  The present invention relates to a material for a photoelectric conversion element containing an organic compound having a specific structure, and a photoelectric conversion element containing the material for a photoelectric conversion element.

  BACKGROUND ART In recent years, there has been increasing interest in organic electronic devices characterized by having flexibility, being able to increase the area, and being able to be manufactured by an inexpensive and high-speed printing method. Representative organic electronic devices include organic EL elements, organic solar cell elements, organic photoelectric conversion elements, organic transistor elements, etc. Among them, organic EL elements are portable devices whose main target is next-generation display applications Applications to telephone displays and TVs are expected, and development aimed at further functional enhancement is continuing. Research and development have been conducted on organic solar cell elements and the like as flexible and inexpensive energy sources, and organic transistor elements and the like have been researched and developed for application to flexible displays and inexpensive IC applications.

  Development of each material which constitutes a device is very important for development of an organic electronic device, and for this reason, in the field of each material, examination and development of still useful materials are carried out energetically. Among them, a compound having naphthodithiophene as a mother skeleton is also studied as an organic electronic material, and application to an organic transistor (Non-Patent Document 1, Patent Documents 1 and 2) has been reported. In addition, a polymer having a naphthodithiophene skeleton is also used as an organic electronic material, and is applied to an organic transistor (non-patent document 2) and a solar cell (non-patent document 3). From this, it can be said that naphtho dithiophene derivatives are molecules suitable for organic electronics.

  On the other hand, organic photoelectric conversion devices are expected to be applied to next-generation imaging devices, and some groups report such applications. For example, an example using a quinacridone derivative or a quinazoline derivative for a photoelectric conversion element (Patent Document 3), an example applying a photoelectric conversion element using a quinacridone derivative to an imaging device (Patent Document 4), a diketopyrrolopyrrole derivative Examples thereof (Patent Document 5) and examples in which a benzodithiophene derivative is used for a photoelectric conversion element (Patent Document 6) can be given. In general, it is considered that the performance of the imaging device is improved by reducing the dark current for the purpose of achieving high contrast and power saving. Therefore, in order to reduce the leak current from the photoelectric conversion portion in the dark, a method of inserting a hole blocking layer or an electron blocking layer between the photoelectric conversion portion and the electrode portion is used.

  A hole blocking layer and an electron blocking layer which are respectively disposed at the interface between an electrode or a film having conductivity and other films in the component film of the device and which are generally used in the field of organic electronic devices are unnecessary. It is a layer (film) that has the function of controlling the reverse movement of holes or electrons by adjusting the leakage of holes or electrons, and taking into consideration characteristics such as heat resistance, transmission wavelength, and film formation method for each application of the device. Above, the material is selected and used. However, the performance required for materials especially in photoelectric conversion device applications is high, and conventionally known materials for the hole blocking layer and the electron blocking layer have aspects such as leakage current prevention characteristics, heat resistance to process temperature, and visible light transparency. Therefore, it can not be said that it has sufficient characteristics, and has not been used commercially.

International Publication No. 2010/058692 Patent No. 5284677 Patent No. 4972288 gazette Patent No. 4945146 Patent No. 50 22 573 International Publication No. 2017/159684 JP 2008-290963 A

J. Am. Chem. Soc., 2011, 133 (13), 5024. J. Am. Chem. Soc., 2011, 133 (17), 6852. J. Am. Chem. Soc., 2013, 135 (24), 8834.

  The present invention has been made in view of such a situation, and is a material of a block layer excellent in hole or electron leak prevention characteristics, hole or electron transport characteristics, heat resistance to process temperature, visible light transparency, etc. It is an object of the present invention to provide various photoelectric conversion element materials including photoelectric conversion element materials and photoelectric conversion elements including the photoelectric conversion element materials.

MEANS TO SOLVE THE PROBLEM As a result of earnest efforts in order to solve the said subject, this inventor discovers that the said subjects are solved by applying the material for photoelectric conversion elements containing the compound of a specific structure to a photoelectric conversion element, This invention It came to complete.
That is, the present invention is as follows.
[1] The following formula (1)

(In formula (1), R ₁ and R ₂ each independently represent an aromatic group or a heterocyclic group. Either _one of X ₁ and X ₂ represents a sulfur atom or an oxygen atom, and the other represents a methine group A material for a photoelectric conversion element containing a compound represented by
[2] The material for a photoelectric conversion element according to the above item [1], wherein one of X ₁ and X ₂ is a sulfur atom, and the other is a methine group,
[3] The photoelectric conversion element material as recited in the aforementioned Item [1] or [2], wherein each of R ₁ and R ₂ independently is an aromatic group.
[4] The material for a photoelectric conversion element according to the preceding item [3], wherein R ₁ and R ₂ are a phenyl group,
[5] The material for a photoelectric conversion element according to the above item [4], wherein each of R ₁ and R ₂ is a phenyl group having a phenyl group,
[6] An organic thin film containing the material for a photoelectric conversion element according to any one of the above [1] to [5],
[7] A photoelectric conversion device comprising the organic thin film according to the preceding item [6],
[8] An imaging device in which a plurality of photoelectric conversion devices according to the previous paragraph [7] are arranged in an array, and [9] a light including the photoelectric conversion device according to the previous paragraph [7] or the imaging device according to the previous paragraph [8] sensor.

  A photoelectric conversion element excellent in the required characteristics such as the leak prevention property and transportability of holes or electrons, and further the heat resistance and visible light transparency by using the material for photoelectric conversion element of the present invention containing the compound of the specific structure Can be provided.

FIG. 1 shows a cross-sectional view illustrating an embodiment of the photoelectric conversion element of the present invention. FIG. 2 shows a dark current-voltage graph of the photoelectric conversion element obtained in Example 1 and Comparative Example 1. FIG. 3 shows a bright current-voltage graph of the photoelectric conversion element obtained in Example 1 and Comparative Example 1.

  The contents of the present invention will be described in detail. Although the description of the configuration requirements described below is based on typical embodiments and examples of the present invention, the present invention is not limited to such embodiments and examples.

  The photoelectric conversion element material of the present invention contains a compound represented by the following formula (1).

R ₁ and R ₂ in the above formula (1) each independently represent an aromatic group or a heterocyclic group.
The aromatic group represented by R ₁ and R _{2 in} the formula (1) is a residue obtained by removing one hydrogen atom from the aromatic ring of the aromatic compound.
The aromatic group represented by R ₁ and R _{2 in} the formula (1) is not particularly limited as long as it is a residue obtained by removing one hydrogen atom from the aromatic ring of an aromatic compound, and examples thereof include phenyl group, biphenyl group, ter Phenyl group, quarter phenyl group, tolyl group, indenyl group, naphthyl group, anthryl group, fluorenyl group, pyrenyl group, phenanthenyl group, mestil group, etc., and phenyl group, biphenyl group, terphenyl group, quarter phenyl group, naphthyl A group or an anthryl group is preferable, and a phenyl group, a biphenyl group, a terphenyl group or a naphthyl group is more preferable.

The aromatic group represented by R ₁ and R _{2 in} Formula (1) may have a substituent.
The substituent which the aromatic group represented by R ₁ and R ₂ of Formula (1) has is not limited, and examples thereof include an alkyl group, an alkoxy group, an aromatic group, a heterocyclic group, a halogen atom, a hydroxyl group, a mercapto group, and nitro Group, alkyl substituted amino group, aryl substituted amino group, unsubstituted amino group (NH ₂ group), cyano group, isocyano group and the like are preferable, and alkyl group, aromatic group, heterocyclic group and halogen atom are more preferable, and aromatic Groups and heterocyclic groups are more preferred.

Specific examples of the alkyl group as a substituent which the aromatic group represented by R ₁ and R ₂ of Formula (1) has include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, iso-butyl group, t-butyl group, n-pentyl group, iso-pentyl group, t-pentyl group, sec-pentyl group, n-hexyl group, iso-hexyl group, n-heptyl group, sec-heptyl group, n-octyl group, n-nonyl group, sec-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, It is preferable that it is a C1-C20 alkyl group such as n-heptadecyl group, n-octadecyl group, n-nonadecyl group and n-eicosyl group, and is an alkyl group having 1 to 12 carbon atoms More preferably in, more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably an alkyl group having 1 to 4 carbon atoms.

The alkoxy group as a substituent that the aromatic group represented by R ₁ and R _{2 in} Formula (1) has is a substituent in which an oxygen atom and an alkyl group are bonded, and specific examples of the alkyl group that the alkoxy group has For example, the same one as the alkyl group described in the section of the alkyl group as a substituent which the aromatic group represented by R ₁ and R ₂ of the formula (1) has is mentioned, and preferable ones are also mentioned.

Specific examples of the aromatic group as a substituent which the aromatic group represented by R ₁ and R ₂ of Formula (1) has are described in the section of the aromatic group represented by R ₁ and R ₂ of Formula (1) The same thing as an aromatic group is mentioned, and a preferable thing is also mentioned.
Specific examples of the heterocyclic group as a substituent which the aromatic group represented by R ₁ and R ₂ of Formula (1) has are described in the section of the heterocyclic group represented by R ₁ and R ₂ of Formula (1) The same thing as a heterocyclic group is mentioned, A preferable thing is also mentioned.
Specific examples of the halogen atom as the substituents of the aromatic group represented by R ₁ and R ₂ of formula (1), a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, a fluorine atom or a chlorine atom Preferably, a fluorine atom is more preferable.
The alkyl-substituted amino group as a substituent which the aromatic group represented by R ₁ and R ₂ of Formula (1) has is not limited to any of a monoalkyl-substituted amino group and a dialkyl-substituted amino group, and these alkyl-substituted amino groups Examples of the alkyl group in the above include the same as the alkyl group described in the section of the alkyl group as a substituent which the aromatic group represented by R ₁ and R _{2 in} Formula (1) has, and preferred examples are also the same It can be mentioned.

The aryl-substituted amino group as a substituent that the aromatic group represented by R ₁ and R ₂ of Formula (1) has is not limited to either a monoaryl-substituted amino group or a diaryl-substituted amino group, and these aryl-substituted amino groups Examples of the aryl group in the same group as the aromatic group and heterocyclic group described in the item of the aromatic group and the heterocyclic group as a substituent which the aromatic group represented by R ₁ and R _{2 in} formula (1) has And preferred ones are also the same.
The substituents of the aromatic group represented by R ₁ and R ₂ of formula (1), an aromatic group or a heterocyclic group. The aromatic group and heterocyclic group may have a substituent, organic and may have substituents as substituents of the aromatic group represented by R ₁ and R ₂ of formula (1) As the same ones as the substituents which the aromatic group represented by R ₁ and R ₂ of the formula (1) has, the same ones can be mentioned as preferable ones.

The heterocyclic group represented by R ₁ and R _{2 in} the formula (1) is a residue obtained by removing one hydrogen atom from the heterocyclic ring of the heterocyclic compound.
The heterocyclic group represented by R ₁ and R _{2 in} the formula (1) is not particularly limited as long as it is a residue obtained by removing one hydrogen atom from the heterocyclic ring of the heterocyclic compound, for example, a furanyl group, a thienyl group, a thienothienyl Group, pyrrolyl group, imidazolyl group, N-methylimidazolyl group, thiazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolyl group, indolyl group, benzopyrazyl group, benzopyrimidyl group, benzothienyl group, naphthothenyl group, benzofuranyl group , Benzothiazolyl group, pyridino thiazolyl group, benzoimidazolyl group, pyridino imidazolyl group, N-methylbenzoimidazolyl group, pyridino-N-methylimidazolyl group, benzooxazolyl group, pyridino oxazolyl group, benzothiadiazolyl Group, pyridinothiadiazolyl group, benzo Thiaxyl group, thienothienyl group, benzothienyl group, naphthothienyl group, benzofuranyl group or pyridyl group are preferable, thienyl group, benzothienyl group, and the like. Groups, naphthothienyl groups or benzofuranyl groups are more preferred.
Heterocyclic group represented by R ₁ and R ₂ of formula (1) may have a substituent, an aromatic Examples of the organic and each may be a substituent represented by R ₁ and R ₂ of formula (1) The same thing as the substituent which a group group has is mentioned, and a preferable thing is also mentioned.
Further, in the above-mentioned preferred embodiment, R ₁ and R ₂ are preferably the same.

One of X ₁ and X ₂ in the formula (1) represents a sulfur atom or an oxygen atom, and the other represents a methine group. That is, the compound represented by Formula (1) represents the compound represented by either following formula (1-1) or (1-2).

In the formula (1-1) and _(1-2), R _1, R 2, _{X 1} and _{X 2} are as defined _{R 1,} R 2, _{X 1} and _{X 2} in Formula (1).

  The compound represented by Formula (1-1) can be synthesized by a known method disclosed in Patent Document 1 and Non-Patent Document 1, and the like. For example, it is possible to synthesize a dichlorodiethynyl naphthalene derivative (B) using a naphthalene derivative (A) as a raw material, and subsequently obtain a desired compound by the flow shown in the following scheme in which a cyclization reaction is performed.

  The compound represented by Formula (1-2) can be synthesized by a known method disclosed in Patent Document 1 and Non-Patent Document 1, and the like. For example, it is possible to synthesize a dibromodiethynyl naphthalene derivative (D) using a naphthalene derivative (C) as a raw material, and subsequently obtain a desired compound by the flow shown in the following scheme in which a cyclization reaction is performed.

  The purification method of the compound represented by the above formula (1) is not particularly limited, and known methods such as recrystallization, column chromatography and vacuum sublimation purification can be adopted. Moreover, these methods can be combined as needed.

  Although the specific example of a compound represented by the said Formula (1) is illustrated below, the compound represented by Formula (1) which the material for photoelectric conversion elements of this invention contains is limited to these specific examples. It is not a thing.

The content of the compound represented by the formula (1) in the material for a photoelectric conversion element of the present invention is not particularly limited as long as the performance required in the application using the material for a photoelectric conversion element is exhibited. It is 80 mass% or more, 90 mass% or more is more preferable, 95 mass% or more is still more preferable.
In the photoelectric conversion element material of the present invention, a compound other than the compound represented by Formula (1) (for example, a photoelectric conversion element material other than the compound represented by Formula (1), etc.), additives, etc. are used in combination May be The compound which can be used together, an additive, etc. are not specifically limited as long as the performance required in the use which uses a photoelectric conversion element material expresses.

The organic thin film of the present invention contains the material for a photoelectric conversion element of the present invention.
The organic thin film of the present invention can be produced by a general dry film forming method or a wet film forming method. Specifically, vacuum processes such as resistance heating evaporation, electron beam evaporation, sputtering and molecular lamination, solution processes casting, spin coating, dip coating, blade coating, wire bar coating, wire coating, spray coating, etc., inkjet printing Printing methods such as screen printing, offset printing and letterpress printing, and methods of soft lithography such as microcontact printing.
In general, it is desirable that the photoelectric conversion element material can be used in a process of applying a compound in a solution state from the viewpoint of ease of processing, but in the case of an organic electronic device such as laminating an organic film, a coating solution Is not suitable because it may attack the underlying organic film.

  In order to realize such a multilayer laminated structure, it is appropriate to use a material that can be used in a dry deposition method, for example, a deposition process such as resistance heating deposition. Therefore, the material for photoelectric conversion elements which can be deposited is preferable.

  You may employ | adopt the method which combined multiple said methods for film-forming of each layer. The thickness of each layer depends on the resistance value / charge mobility of each material and can not be limited, but is usually in the range of 0.5 to 5000 nm, preferably in the range of 1 to 1000 nm, more preferably 5 To 500 nm.

[Organic electronics device]
The photoelectric conversion element of the present invention comprises the organic thin film of the present invention. The photoelectric conversion element is an element in which a photoelectric conversion portion (film) is disposed between a pair of opposing electrode films, and light is incident on the photoelectric conversion portion from above the electrode film. The photoelectric conversion unit generates electrons and holes in response to the incident light, and a signal corresponding to the charge is read by the semiconductor, and an element showing an incident light amount in accordance with the absorption wavelength of the photoelectric conversion film unit. It is. There are also cases where a transistor for readout is connected to the electrode film on the side where light does not enter. When a large number of photoelectric conversion elements are arranged in the form of an array, in addition to the amount of incident light, incident position information is also displayed, and thus the image sensor is obtained. When the photoelectric conversion element arranged closer to the light source does not block (transmit) the absorption wavelength of the photoelectric conversion element arranged behind it as viewed from the light source side, a plurality of photoelectric conversion elements are stacked. You may use.

The photoelectric conversion element of the present invention uses the compound represented by the formula (1) as a constituent material of the photoelectric conversion unit.
The photoelectric conversion portion is one or more selected from the group consisting of a photoelectric conversion layer, an electron transport layer, a hole transport layer, an electron block layer, a hole block layer, a crystallization prevention layer, an interlayer contact improvement layer, etc. It often comprises an organic thin film layer other than the photoelectric conversion layer. In particular, the electron transport layer, the hole transport layer, the electron block layer and the hole block layer are hereinafter also referred to as a carrier block layer. The compound of the present invention can be used in addition to the carrier block layer, but is preferably used as an organic thin film layer of the carrier block layer. The carrier block layer may be composed only of the compound represented by the formula (1), but may contain known block materials and others in addition to the compound represented by the formula (1).

  The electrode film used for the photoelectric conversion element of the present invention has a hole transportability when the photoelectric conversion layer contained in the photoelectric conversion portion described later has a hole transportability, or a hole transportability in the organic thin film layer other than the photoelectric conversion layer. When it is a transport layer, it plays a role of taking out holes from the photoelectric conversion layer and other organic thin film layers and collecting the holes, and when the photoelectric conversion layer included in the photoelectric conversion portion has electron transportability When the organic thin film layer is an electron transporting layer having an electron transporting property, it plays a role of taking out electrons from the photoelectric conversion layer and the other organic thin film layer and discharging the electrons. 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, but adhesion to adjacent photoelectric conversion layers and other organic thin film layers, electron affinity, ionization potential, stability, etc. It is preferable to select in consideration of As a material which can be used as an electrode film, for example, conductive metal oxides such as tin oxide (NESA), indium oxide, indium tin oxide (ITO) and zinc indium oxide (IZO); gold, silver, platinum, chromium, 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: Carbon and the like. A plurality of these materials may be mixed and used as needed, and a plurality of these materials may be stacked and used in two or more layers. The conductivity of the material used for the electrode film is not particularly limited as long as the light reception of the photoelectric conversion element is not disturbed more than necessary, but it is preferable that it is as high as possible from the viewpoint of signal strength of the photoelectric conversion element and power consumption. For example, an ITO film having a sheet resistance value of 300 ohms / square or less functions sufficiently as an electrode film, but a commercially available substrate having an ITO film having a conductivity of several ohms / square or so is also available. Therefore, it is desirable to use a substrate having such high conductivity. The thickness of the ITO film (electrode film) can be arbitrarily selected in consideration of the conductivity, but it is usually 5 to 500 nm, preferably about 10 to 300 nm. Examples of the method for forming a film such as ITO include a conventionally known vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, a coating method and the like. The ITO film provided on the substrate may be subjected to UV-ozone treatment, plasma treatment or the like as required.

The material of the transparent electrode film used for at least one of the electrode films on the light incident side includes ITO, IZO, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide) GZO (gallium-doped zinc oxide), TiO ₂ and 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 .

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

  The electrode film is preferably made plasma free. By forming these electrode films without using plasma, the influence of plasma on the substrate on which the electrode film is provided can be reduced, and the photoelectric conversion characteristics of the photoelectric conversion element can be improved. Here, plasma-free means that no plasma is generated during deposition of the electrode film, or the distance from the plasma source to the substrate is 2 cm or more, preferably 10 cm or more, more preferably 20 cm or more, and reaches the substrate It means that the plasma can be reduced.

  As an apparatus which plasma does not generate | occur | produce at the time of film-forming of an electrode film, an electron beam vapor deposition apparatus (EB vapor deposition apparatus), a pulse laser vapor deposition apparatus, etc. are mentioned, for example. A method of forming a transparent electrode film using an EB vapor deposition apparatus is referred to as EB vapor deposition, and a method of forming a transparent electrode film using a pulsed laser vapor deposition apparatus is referred to as pulsed laser vapor deposition.

  As an apparatus capable of realizing a state capable of reducing plasma during film formation (hereinafter, referred to as a film forming apparatus which is free from plasma), for example, a facing target sputtering apparatus, an arc plasma deposition apparatus, etc. can be considered.

  When the transparent conductive film is an electrode film (for example, the first conductive film), DC shorting or an increase in leak current may occur. One of the causes is that fine cracks generated in the photoelectric conversion layer are covered with a dense film such as TCO (Transparent Conductive Oxide) and the conduction between the transparent conductive film and the electrode film on the opposite side is increased. it is conceivable that. Therefore, when a material such as Al, which is inferior in film quality, is used for the electrode, the increase of the leak current hardly occurs. By controlling the film thickness of the electrode film in accordance with the film thickness (depth of the crack) of the photoelectric conversion layer, it is possible to suppress an increase in leak current.

  Usually, when the conductive film is thinner than a predetermined value, a sharp increase in resistance occurs. The sheet resistance of the conductive film in the photoelectric conversion element for an optical sensor of the present embodiment is usually 100 to 10000 Ω / □, and the degree of freedom of film thickness is large. In addition, the thinner the transparent conductive film, the smaller the amount of light absorbed, and generally the higher the light transmittance. When the light transmittance is high, the light absorbed by the photoelectric conversion layer is increased to improve the photoelectric conversion ability, which is very preferable.

  The photoelectric conversion part which the photoelectric conversion element of the present invention has includes a photoelectric conversion layer, a carrier block layer, and other organic thin film layers. Although an organic semiconductor film is generally used for the photoelectric conversion layer constituting the photoelectric conversion portion, the organic semiconductor film may be a single 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 mixed film thereof (bulk heterostructure) is used. On the other hand, in the case of a plurality of layers, it is about 2 to 10 layers, and has a structure in which any of a P-type organic semiconductor film, an N-type organic semiconductor film, or a mixed film thereof (bulk heterostructure) is stacked. A buffer layer may be inserted in

  In the organic semiconductor film of the photoelectric conversion layer, a triarylamine compound, a benzidine compound, a pyrazoline compound, a styrylamine compound, a hydrazone compound, a triphenylmethane compound, a carbazole compound, a polysilane compound, a thiophene compound, a phthalocyanine according to a wavelength band to be absorbed. Compound, cyanine compound, merocyanine compound, oxonol compound, polyamine compound, indole compound, pyrrole compound, pyrazole compound, polyarylene compound, carbazole derivative, naphthalene derivative, anthracene derivative, chrysene derivative, phenanthrene derivative, pentacene derivative, phenylbutadiene derivative, styryl Derivative, quinoline derivative, tetracene derivative, pyrene derivative, perylene derivative, fluoranthene derivative, quinacridone derivative Coumarin derivatives, porphyrin derivatives, fullerene derivatives and metal complexes (Ir complexes, Pt complexes, Eu complexes, etc.), or the like can be used.

The electron transport layer of the present invention plays a role of transporting electrons generated in the photoelectric conversion layer to the electrode film and a role of blocking migration of holes from the electrode film of the electron transport destination 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 transfer of electrons from the electrode film of the hole transport destination to the photoelectric conversion layer. The electron blocking layer prevents the movement of electrons from the electrode film to the photoelectric conversion layer, prevents recombination in the photoelectric conversion layer, and plays a role in reducing dark current. The hole blocking layer has a function of blocking movement of holes from the electrode film to the photoelectric conversion layer, preventing recombination in the photoelectric conversion layer, and reducing dark current.
The hole blocking layer is formed by laminating or mixing hole blocking substances singly or in combination of two or more. The hole blocking substance is not limited as long as it is a compound capable of blocking the flow of holes from the electrode to the outside of the device. Examples of compounds that can be used in the hole blocking layer include phenanthroline derivatives such as vasophenanthroline and vasocuproin, silole derivatives, quinolinol derivative metal complexes, oxadiazole derivatives, in addition to the compounds represented by the above formula (1). An oxazole derivative, a quinoline derivative, etc. are mentioned, 1 or 2 types or more can be used among these.

  Although the typical element structure of the photoelectric conversion element of this invention is shown in FIG. 1, this invention is not limited to this structure. In the embodiment of FIG. 1, 1 is an insulating portion, 2 is one electrode film, 3 is an electron blocking layer, 4 is a photoelectric conversion layer, 5 is a hole blocking layer, 6 is the other electrode film, 7 is an insulating group Material or other photoelectric conversion element respectively. Although a transistor for reading is not shown in the drawing, it may be connected to the electrode film of 2 or 6, and further, if the photoelectric conversion layer 4 is transparent, the side opposite to the light incident side The film may be formed on the outside of the electrode film. The incidence of light on the photoelectric conversion element can be made from any of the upper and lower parts as long as the components excluding the photoelectric conversion layer 4 do not extremely inhibit the incidence of light of the main absorption wavelength of the photoelectric conversion layer. May be.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
The blocking layer described in the examples may be either a hole blocking layer or an electron blocking layer.
Preparation of the photoelectric conversion element of an Example and a comparative example was performed with a vapor deposition machine, and the application measurement of the current voltage was performed under air | atmosphere. The produced photoelectric conversion element installed the photoelectric conversion element in a closed bottle type measurement chamber (manufactured by AEL S Technology Co., Ltd.) in a glove box under a nitrogen atmosphere, and applied voltage was measured. The application measurement of the current voltage was performed using semiconductor parameter analyzer 4200-SCS (Keithley Instruments). Irradiation of incident light was performed by irradiation light wavelength 550nm and irradiation light half width 20 nm using PVL-3300 (made by Asahi Spectroscopic). The contrast ratio in the examples indicates the current value in the case of light irradiation divided by the current value in the dark.

Example 1 (Fabrication of photoelectric conversion element and evaluation thereof)
2,7-Bis (1,1'-biphenyl-4-yl) naphtho [1,2-b: 5,6-b '] on an ITO transparent conductive glass (Diomatec Co., Ltd., ITO film thickness 150 nm) Dithiophene (the compound represented by No. 2 in the above specific example) was deposited to a thickness of 50 nm by resistance heating vacuum evaporation as a block layer. Next, on the block layer, quinacridone was vacuum deposited to 100 nm as a photoelectric conversion layer. Finally, 100 nm of aluminum was deposited as an electrode on the photoelectric conversion layer in a vacuum to form a photoelectric conversion element of the present invention. When a voltage of 5 V was applied to ITO and aluminum as electrodes, the current in the dark was 1.77 × 10 ⁻¹¹ A / cm ² . Moreover, the electric current at the time of applying the voltage of 5 V to the transparent conductive glass side and performing light irradiation was 1.14 * 10 < ^-5 > A / cm < ² >. The contrast ratio was 6.4 × 10 ⁵ when a voltage of 5 V was applied to the transparent conductive glass side.

Example 2 (Production of photoelectric conversion element and evaluation thereof)
2,7-bis (1,1′-biphenyl-4-yl) naphtho [2,1-b: 6,5-b ′] dithiophene as the block layer (the compound represented by No. 37 in the above specific example) The photoelectric conversion element was produced according to Example 1 except having used it. When a voltage of 5 V was applied to ITO and aluminum as electrodes, the current in the dark was 2.74 × 10 ⁻¹¹ A / cm ² . Moreover, the electric current at the time of applying the voltage of 5 V to the transparent conductive glass side and performing light irradiation was 4.46 * 10 < ^-5 > A / cm < ² >. The contrast ratio was 4.5 × 10 ⁵ when a voltage of 5 V was applied to the transparent conductive glass side.

Example 3 (Fabrication of photoelectric conversion element and evaluation thereof)
2,7-bis ([1,1 ′: 3 ′, 1 ′ ′-terphenyl] -4-yl) naphtho [1,2-b: 5,6-b ′] dithiophene as the block layer A photoelectric conversion element was produced according to Example 1 except that the compound represented by No. 11 was used. When a voltage of 5 V was applied with ITO and aluminum as electrodes, the current in the dark was 1.46 × 10 ⁻¹¹ A / cm ² . Moreover, the electric current at the time of applying the voltage of 5 V to the transparent conductive glass side and performing light irradiation was 3.68 * 10 < ^-5 > A / cm < ² >. The contrast ratio was 2.5 × 10 ⁵ when a voltage of 5 V was applied to the transparent conductive glass side.

Comparative Example 1 (Production and Evaluation of Comparative Photoelectric Conversion Element)
50 nm of tris (8-quinolinolato) aluminum was formed into a film by resistance heating vacuum evaporation as a block layer on ITO transparent conductive glass (Diomatec Co., Ltd. product, ITO film thickness 150 nm). Next, on the block layer, quinacridone was vacuum deposited to 100 nm as a photoelectric conversion layer. Lastly, aluminum was deposited in a vacuum of 100 nm as an electrode on the photoelectric conversion layer to fabricate a photoelectric conversion element for comparison. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in the dark was 9.15 × 10 ⁻⁸ A / cm ² . Moreover, the electric current at the time of applying the voltage of 5 V to the transparent conductive glass side and performing light irradiation was 1.04 * 10 < ^-5 > A / cm < ² >. The contrast ratio was 113 when a voltage of 5 V was applied to the transparent conductive glass side.

Comparative Example 2 (Production and Evaluation of Comparative Photoelectric Conversion Element)
The photoelectric conversion element was produced according to Example 1 except having used the compound represented by following formula (2) synthesize | combined by the method of patent document 6 as a block layer. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in the dark was 4.54 × 10 ⁻¹¹ A / cm ² . Moreover, the electric current at the time of applying the voltage of 5 V to the transparent conductive glass side and performing light irradiation was 1.21 * 10 < ^-5 > A / cm < ² >. The contrast ratio was 2.7 × 10 ⁵ when a voltage of 5 V was applied to the transparent conductive glass side.

  The dark current-voltage graph obtained in the evaluation of the above Example 1 and Comparative Example 1 is shown in FIG. 2, and the light current-voltage graph is shown in FIG. As shown in FIGS. 2 and 3 and the above examples and comparative examples, the photoelectric conversion element of the present invention exhibits a dark current value three or more orders of magnitude lower than that of the photoelectric conversion element for comparison, I understand that From this, it is apparent that the material for photoelectric conversion elements of the present invention has excellent block performance.

  A voltage of 15 V is applied to the photoelectric conversion elements of Examples 1 to 3 and Comparative Examples 1 and 2, and the current value and the current value when light irradiation is performed in a dark place are measured. The contrast ratio divided by was calculated, and the results are shown in Table 1.

  From the results of Table 1, it can be seen that the photoelectric conversion devices of Examples 1 to 3 exhibit higher contrast ratio than the photoelectric conversion devices of Comparative Examples 1 and 2. Also from this result, it is clear that the photoelectric conversion element material of the present invention has excellent performance as a block material.

  A photoelectric conversion element excellent in the required characteristics such as the leak prevention property and transportability of holes or electrons, and further the heat resistance and visible light transparency by using the material for photoelectric conversion element of the present invention containing the compound of the specific structure Can be provided. Therefore, not only organic imaging devices having high resolution and high responsiveness but also organic solar cells, light sensors, infrared sensors, ultraviolet sensors, devices such as X-ray sensors and photon counters, cameras using them, video cameras, infrared cameras Application to the field of etc. is expected.

Reference Signs List 1 insulating part 2 upper electrode 3 electron block layer or hole transport layer 4 photoelectric conversion layer 5 hole block layer or electron transport layer 6 lower electrode 7 insulating substrate or other photoelectric conversion element

Claims (9)

Following formula (1)

(In formula (1), R ₁ and R ₂ each independently represent an aromatic group or a heterocyclic group. Either _one of X ₁ and X ₂ represents a sulfur atom or an oxygen atom, and the other represents a methine group The material for photoelectric conversion elements containing the compound represented by these.). The material for a photoelectric conversion element according to claim 1, wherein one of X ₁ and X ₂ is a sulfur atom, and the other is a methine group. The material for a photoelectric conversion element according to claim _1, wherein R ₁ and R ₂ are each independently an aromatic group. The material for photoelectric conversion elements according to claim 3, wherein R ₁ and R ₂ are phenyl groups. The material for photoelectric conversion elements according to claim 4, wherein R ₁ and R ₂ are phenyl groups having a phenyl group. The organic thin film containing the material for photoelectric conversion elements as described in any one of Claims 1 thru | or 5. The photoelectric conversion element containing the organic thin film of Claim 6. An imaging device in which a plurality of photoelectric conversion devices according to claim 7 are arranged in an array. An optical sensor comprising the photoelectric conversion element according to claim 7 or the imaging element according to claim 8.

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