JP6910880B2 - Organic photoelectric conversion elements, materials for organic photoelectric conversion elements, and organic imaging devices using these - Google Patents

Description

The present invention relates to an organic photoelectric conversion element, a material for an organic photoelectric conversion element, and an organic imaging element using these. More specifically, an organic photoelectric conversion element using [2,3-b: 2', 3'-f] thieno [3,2-b] thiophene (hereinafter referred to as "DNT") having a substituent, organic photoelectric. The present invention relates to a material for a conversion element and an organic imaging element.

Organic electronics devices have been researched and developed in recent years because they do not contain rare metals in their raw materials and can be stably supplied, as well as being flexible and can be manufactured by a wet film formation method, which are not found in inorganic materials. ing. Specific examples of organic electronic devices include organic EL elements, organic solar cell elements, organic photoelectric conversion elements, organic transistor elements, etc. In addition to their performance as devices, there are various applications that take advantage of the characteristics of organic compounds. It is being considered.

Among the above devices, the organic photoelectric conversion element is used for an optical sensor or the like, and its use as an image sensor, for example, is being studied. Currently, three-plate and single-plate image sensors using existing inorganic materials are known. Of these, the three-plate type separates the light into the three primary colors of red, green, and blue by a prism, and the light is separately photoelectrically converted by an imaging device. Therefore, while the sensitivity is excellent, it is difficult to miniaturize the device. On the other hand, the single plate type has a structure in which a color filter is provided in the imaging device, and can be miniaturized, but the resolution is inferior. From the above background, an organic imaging device in which a photoelectric conversion film using an organic compound is laminated has been studied today (Patent Documents 1 and 2). Such an organic imaging element has a structure in which organic materials that selectively absorb one of the above three primary colors and transmit the other light are laminated, and select red, green, and blue wavelength regions. It consists of a laminated structure of organic thin films that absorbs light. That is, the red photoelectric conversion layer in which the absorption band of the organic material when formed into a thin film is in the range of 600 nm or more and 700 nm or less, the green photoelectric conversion layer having 500 nm or more and 600 nm or less, and the blue photoelectric conversion layer having 400 nm or more and 500 nm or less. It consists of a laminated structure. Such an organic image sensor is attractive in that it can be expected to be smaller and have higher resolution, and is expected to be applied to the next generation image sensor.

Among the materials used for the photoelectric conversion unit, the blue photoelectric conversion material includes merocyanine dye (Patent Document 2), coumarin 6 (Non-Patent Document 1), porphyrin derivative (Non-Patent Document 2), anthraquinone derivative (Patent Document 3), and DNTT. (Patent Document 4, Non-Patent Document 3) and the like have been studied, but none of them can be said to have sufficient performance in terms of photoelectric conversion characteristics, durability against process temperature, light resistance of the material itself, and the like. .. In addition, the photoelectric conversion unit aims to reduce the leakage current from the photoelectric conversion unit from the viewpoint of improving the performance of the image sensor by reducing the dark current in order to increase the contrast and power saving of the organic image sensor. Attempts have been made to insert a hole block layer or an electron block layer as a carrier block layer between the electrode portion and the electrode portion. Insertion of such a carrier block layer is a widely known method in the field of organic electronics. The carrier block layer arranged at the interface between the electrode or the conductive film and the other film in the constituent film of the device controls the reverse movement of carriers such as holes or electrons to prevent unnecessary carrier leakage. Although it plays a role of adjusting, when the carrier block layer is used for a photoelectric conversion element, it is necessary to consider the transmission wavelength, durability, heat resistance, film forming method, etc. according to the application of the device, the manufacturing process, and the like.

Japanese Unexamined Patent Publication No. 2003-158254 Japanese Unexamined Patent Publication No. 2005-303266 Japanese Unexamined Patent Publication No. 2011-238781 Japanese Unexamined Patent Publication No. 2011-192966

Journal of the Institute of Image Information and Television Engineers 2006, 60 (3), 291-294 JPn. J. Apple. Phys. , 2005,44 (6A), 3743-3747 Org. Electron. , 2015, 20, 63-68

Among the above-mentioned prior arts, for example, the porphyrin derivative described in Non-Patent Document 2 has been shown to have specific photoelectric conversion performance, but has a problem that the quantum efficiency is not improved even under high voltage conditions. ..
In view of the above situation, when used in the photoelectric conversion unit, it functions efficiently at a low voltage by selectively absorbing blue light with a maximum absorption of 400 nm or more and 500 nm or less, and when used in other than the photoelectric conversion unit. There is a demand for a photoelectric conversion element material for an imaging element, which exhibits good carrier leak prevention characteristics or carrier transport characteristics and also has excellent heat resistance to a process temperature, and an organic photoelectric conversion element using the photoelectric conversion material. There is.

As a result of diligent studies to overcome such problems, the present inventors have found that a group of DNTT derivatives having substituents has a selective absorption band in the blue wavelength region, and the derivatives are converted into photoelectric conversion of a photoelectric conversion element. Based on these findings, it was found that when it is used in a part, it shows an excellent optical response current at a low voltage, and when the derivative is used in a part other than the photoelectric conversion part, it significantly improves the light-dark ratio of the photoelectric conversion element. The present invention has been completed as a means for solving the above problems. That is, the present invention

（上記式（１）中のＲ_１とＲ_２は水素原子又は置換基を有してもよい芳香族基を表す。複数存在するＲ_１、Ｒ_２はそれぞれ同一であっても異なってもよいが、Ｒ_１とＲ_２はいずれも水素原子を有する場合を除く。）
［２］式（１）中、Ｒ_１が置換基を有してもよい芳香族基を表し、Ｒ_２が水素原子である前項［１］に記載の有機光電変換素子、
［３］式（１）中、Ｒ_１が水素原子を表し、Ｒ_２が置換基を有してもよい芳香族基である前項［１］に記載の有機光電変換素子、
［４］薄膜又は固体状態において、光吸収帯の極大吸収が４００ｎｍ以上５００ｎｍ以下にある前項［１］〜［３］記載の有機光電変換素子、
［５］下記式（１）で表される有機化合物を含む有機光電変換素子用材料、

（上記式（１）中のＲ_１とＲ_２は水素原子又は置換基を有してもよい芳香族基を表す。複数存在するＲ_１、Ｒ_２はそれぞれ同一であっても異なってもよいが、Ｒ_１とＲ_２はいずれも水素原子を有する場合を除く。）
［６］薄膜又は固体状態において、光吸収帯の吸収極大が４００ｎｍ以上５００ｎｍ以下にある前項［５］に記載の有機光電変換素子用材料、
［７］前項［５］又は［６］に記載の有機光電変換素子用材料を含む有機薄膜、
［８］前項［５］又は［６］に記載の有機光電変換素子用材料、又は前項［７］に記載の有機薄膜を含む有機光電変換素子、
［９］前項［１］〜［４］並びに［８］のいずれか一項に記載の有機光電変換素子を用いた光センサ、
［１０］前項［１］〜［４］並びに［８］のいずれか一項に記載の有機光電変換素子を用いた有機撮像素子、
に関する。 [1] An organic photoelectric conversion element containing an organic compound represented by the following formula (1).

_{(R 1} and R ₂ in the above formula (1) represent aromatic groups that may have a hydrogen atom or a substituent. A plurality of R ₁ and R ₂ may be the same or different from each other. However, _{except when both R 1} and R ₂ have a hydrogen atom.)
[2] In the formula (1), the organic photoelectric conversion element according to the previous _{item [1], wherein R 1} represents an aromatic group which may have a substituent and R _{2 is a hydrogen atom.}
[3] In the formula (1), _{the organic photoelectric conversion element according to the previous item [1], wherein R 1} represents a hydrogen atom and R ₂ is an aromatic group which may have a substituent.
[4] The organic photoelectric conversion element according to the above items [1] to [3], wherein the maximum absorption of the light absorption band is 400 nm or more and 500 nm or less in a thin film or solid state.
[5] A material for an organic photoelectric conversion element containing an organic compound represented by the following formula (1).

_{(R 1} and R ₂ in the above formula (1) represent aromatic groups that may have a hydrogen atom or a substituent. A plurality of R ₁ and R ₂ may be the same or different from each other. However, _{except when both R 1} and R ₂ have a hydrogen atom.)
[6] The material for an organic photoelectric conversion element according to the previous item [5], wherein the absorption maximum of the light absorption band is 400 nm or more and 500 nm or less in a thin film or solid state.
[7] An organic thin film containing the material for an organic photoelectric conversion element according to the preceding item [5] or [6].
[8] The material for an organic photoelectric conversion element according to the previous item [5] or [6], or the organic photoelectric conversion element containing the organic thin film according to the previous item [7].
[9] An optical sensor using the organic photoelectric conversion element according to any one of the above items [1] to [4] and [8].
[10] An organic imaging device using the organic photoelectric conversion element according to any one of the above items [1] to [4] and [8].
Regarding.

The organic photoelectric conversion element using the organic compound represented by the general formula (1) of the present invention can selectively absorb blue light having a maximum absorption of 400 nm or more and 500 nm or less in the light absorption band, and has a low voltage. Since it exhibits an excellent optical response current, it can be used for an organic photoelectric conversion element for blue light, an organic imaging element, a material thereof, and the like.

A cross-sectional view illustrating an embodiment of the organic photoelectric conversion element of the present invention is shown.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described here is based on the typical embodiments and specific examples of the present invention, while the present invention is not limited to such embodiments and specific examples.

（上記式（１）中のＲ_１とＲ_２は水素原子又は置換基を有してもよい芳香族基を表す。複数存在するＲ_１、Ｒ_２はそれぞれ同一であっても異なってもよいが、Ｒ_１とＲ_２はいずれも水素原子を有する場合を除く。） The organic photoelectric conversion element of the present invention is characterized by containing an organic compound represented by the following formula (1).

_{(R 1} and R ₂ in the above formula (1) represent aromatic groups that may have a hydrogen atom or a substituent. A plurality of R ₁ and R ₂ may be the same or different from each other. However, _{except when both R 1} and R ₂ have a hydrogen atom.)

In the general formula (1), the _{aromatic group represented by R 1} and R ₂ is not limited to either an aromatic group having a substituent or an unsubstituted aromatic group, and is substituted when it has a substituent. The position and the number of substituents are not particularly limited.
In the present invention, the aromatic group having a substituent is an aromatic group in which one or more of the hydrogen atoms of the aromatic group are substituted with a substituent, and the unsubstituted aromatic group is an aromatic group. It means an aromatic group in which the hydrogen atom of the group is not substituted with a substituent.
_{Specific examples of the aromatic group represented by R 1} and R ₂ of the formula (1) include an aromatic hydrocarbon group such as a phenyl group, a biphenyl group, an indenyl group, a naphthyl group, an anthryl group, a fluorenyl group and a pyrenyl group. Examples thereof include a fused heterocyclic group such as a furanyl group, a thienyl group, a thienotienyl group, a pyrrolyl group, an imidazolyl group, a pyridyl group, a pyrazil group, a pyrimidyl group, a quinolyl group, an indolyl group and a carbazolyl group, and are aromatic hydrocarbon groups. It is preferable to have. Further, it is preferable that R ₁ and R _{2 are} different, and further, it is preferable that R ₁ is an aromatic group and R ₂ is a hydrogen atom or an aromatic group different from _{R 1.}
The equation (1) shows only one of the resonance structures, and is not limited to the illustrated resonance structure.

The substituent that the aromatic group can have is not particularly limited, but for example, an alkyl group, an alkoxy group, an alkylthio group, an aromatic group, a halogen atom, a hydroxyl group, a mercapto group, a nitro group, a substituted amino group, or an unsubstituted amino group. , Cyano group, sulfo group, acyl group, sulfamoyl group, alkylsulfamoyl group, carbamoyl group, alkylcarbamoyl group and the like.

Specific examples of the above alkyl group include a linear or branched group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group and a dodecyl group. Examples thereof include a cyclic alkyl group such as a chain alkyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group and a cyclohexyl group. Of these, an alkyl group having 1 to 6 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms is more preferable. Examples of the alkoxy group include those in which an alkyl group is bonded to an oxygen atom, but the number, position, and number of branches of the oxygen atom do not matter. Examples of the alkylthio group include those in which an alkyl group is bonded to a sulfur atom, but the number, position, and number of branches of the sulfur atom do not matter. Specific examples of the aromatic group include the same _{aromatic groups represented by R 1} and R ₂ in the formula (1), and among them, a phenyl group and a biphenyl group are preferable. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and among them, a fluorine atom and a chlorine atom are preferable. Examples of the substituted amino group include those in which the hydrogen atom of the amino group is substituted with the above substituent. Examples of the acyl group include those in which the aromatic group or the alkyl group is bonded to the carbonyl group. Examples of the alkyl sulfamoyl group include those in which the hydrogen atom of the sulfamoyl group is replaced with the alkyl group. Examples of the alkylcarbamoyl group include those in which the hydrogen atom of the carbamoyl group is replaced with the alkyl group.

_{That is, as R 1} and R ₂ in the general formula (1), an aromatic group having one or more substituents independently selected from the group consisting of an alkyl group, an aromatic hydrocarbon group and a halogen atom, respectively. Alternatively, an unsubstituted aromatic group is preferable, and an aromatic hydrocarbon group having one or more substituents independently selected from the group consisting of an alkyl group and an aromatic hydrocarbon group is more preferable. More specifically, in the above preferred embodiment, it is preferable that _one of R 1 and R ₂ is an aromatic group having or not substituted as described above and the other is a hydrogen atom, and R ₁ is It is more preferable that the aromatic group has a substituent or is unsubstituted and R _{2 is a hydrogen atom.}

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

The method for synthesizing the organic compound represented by the formula (1) can be synthesized by the same reaction step as known methods (for example, Japanese Patent No. 59017732 and Japanese Patent No. 5674916). The purification method of these compounds is not particularly limited, and for example, washing, recrystallization, column chromatography, vacuum sublimation and the like can be adopted, and these methods can be combined as necessary.

As the organic thin film of the present invention, a material for an organic photoelectric conversion element containing an organic compound represented by the general formula (1) can be used. The organic thin film of the present invention may be composed only of the material for the organic photoelectric conversion element, but a separately known organic semiconductor material may be added. Further, regardless of the configuration, when the material for an organic photoelectric conversion element containing the organic compound represented by the general formula (1) is contained and the organic thin film is measured for wavelength-absorbance by a spectrophotometer, it is 400 nm. If it absorbs blue light of 500 nm or more, it is an organic thin film that absorbs blue light and can be used as a photoelectric conversion layer.

Examples of the method for forming an organic thin film in the present invention include a general dry film forming method and a wet film forming method. Specifically, it is a vacuum process such as resistance heating vapor deposition, electron beam deposition, sputtering, molecular lamination method, solution process casting, spin coating, dip coating, blade coating, wire bar coating, spray coating and other coating methods, and inkjet printing. , Screen printing, offset printing, printing methods such as letterpress printing, soft lithography methods such as microcontact printing, and the like, and a method in which a plurality of these methods are combined may be adopted for film formation of each layer. The thickness of each layer cannot be limited because it depends on the resistance value and charge mobility of each substance, but is usually in the range of 0.5 to 5000 nm, preferably in the range of 1 to 1000 nm, and more preferably 5. It is in the range of to 500 nm.

An organic electronic device can be manufactured by using the organic compound represented by the general formula (1), or the material or thin film for the organic photoelectric conversion element. Examples of the organic electronics device include a thin film, an organic photoelectric conversion element, an organic solar cell element, an organic EL element, an organic light emitting transistor element, an organic semiconductor laser element, and the like. In the present invention, particular attention is paid to the organic photoelectric conversion element. .. Here, an organic photoelectric conversion element (including an optical sensor and an organic image sensor) will be described.

As the organic photoelectric conversion element of the present invention, an organic compound represented by the formula (1), a material for an organic photoelectric conversion element containing the organic compound, or an organic thin film containing the material can be used. In particular, it can be used as a photoelectric conversion layer in an organic photoelectric conversion element. As a photoelectric conversion element for blue light, the wavelength-absorbance is measured by a spectrophotometer in an organic thin film formed by a general dry film forming method or a wet film forming method, which is the method for forming an organic thin film described above. Of the band that absorbs light in the visible light region (380 nm to 780 nm) observed when The maximum absorption is 400 nm or more and 500 nm or less, preferably 420 nm or more and 480 nm or less, and more preferably 430 nm or more and 470 nm or less.

An organic photoelectric conversion element is an element in which a photoelectric conversion unit (film) is arranged between a pair of electrode films facing each other, and light is incident on the photoelectric conversion unit from above the electrode films. The photoelectric conversion unit generates electrons and holes in response to the incident light, and a semiconductor reads out a signal corresponding to the electric charge to indicate the amount of incident light according to the absorption wavelength of the photoelectric conversion film unit. Is. A transistor for reading may be connected to the electrode film on the side where light is not incident. When a large number of photoelectric conversion elements are arranged in an array, they are image pickup elements because they also show incident position information in addition to the amount of incident light. Further, when the photoelectric conversion element arranged closer to the light source does not shield (transmit) the absorption wavelength of the photoelectric conversion element arranged behind the photoelectric conversion element when viewed from the light source side, a plurality of photoelectric conversion elements are laminated. You may use it.

In the present invention, the organic compound represented by the general formula (1) and the material for the organic photoelectric conversion element can be used as the constituent material of the photoelectric conversion unit. The photoelectric conversion unit is one or a plurality of types 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, and the like. It often consists of an organic thin film layer other than the photoelectric conversion layer. The organic compound represented by the formula (1) and the material for the organic photoelectric conversion element are preferably used as the organic thin film layer of the photoelectric conversion layer, but in addition to the above organic thin film layer (particularly, the electron transport layer and holes). It can also be used as a transport layer, an electron block layer, a hole block layer). When used in the photoelectric conversion layer, it may be composed only of the organic compound represented by the above formula (1) and the material for the organic photoelectric conversion element, but the organic compound represented by the general formula (1) and organic. An organic semiconductor material may be contained in addition to the material for the photoelectric conversion element. These organic thin film layers may have a laminated structure, but may include an organic thin film formed by co-depositing a material, and at the same time, a co-deposited film, a single film, or another co-deposited film is formed in a plurality of layers. , It may be an organic thin film that functions.

In the electrode film used in the organic photoelectric conversion element of the present invention, the photoelectric conversion layer included in the photoelectric conversion unit described later has hole transportability, or the organic thin film layer other than the photoelectric conversion layer has hole transport property. In the case of a hole transport layer, it plays a role of extracting holes from the photoelectric conversion layer and other organic thin film layers and collecting them, and the photoelectric conversion layer included in the photoelectric conversion unit has electron transportability. In some cases, or when the organic thin film layer is an electron transporting layer having electron transporting properties, it plays a role of extracting electrons from the photoelectric conversion layer and other organic thin film layers and discharging 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, but the adhesion, electron affinity, ionization potential, and stability with the adjacent photoelectric conversion layer and other organic thin film layers are not particularly limited. It is preferable to select it in consideration of the above. Materials that can be used as the electrode film 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: Carbon and the like. If necessary, a plurality of these materials may be mixed and used, or a plurality of these materials may be laminated in two or more layers. The conductivity of the material used for the electrode film is not particularly limited as long as it does not interfere with the light reception of the photoelectric conversion element more than necessary, but it is preferably as high as possible from the viewpoint of the signal strength of the photoelectric conversion element and the power consumption. For example, an ITO film having a conductivity of 300 Ω / □ or less functions sufficiently as an electrode film, but a commercially available substrate having an ITO film having a conductivity of several Ω / □ 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 conductivity, but is usually about 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, electron beam method, sputtering method, chemical reaction method, coating method and the like. The ITO film provided on the substrate may be subjected to UV-ozone treatment, plasma treatment, or the like, if necessary.

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

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

The electrode film is preferably plasma-free. By producing these electrode films in a plasma-free manner, 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 plasma is not generated when the electrode film is formed, or the distance from the plasma generation 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 a state in which the plasma is reduced.

Examples of the device that does not generate plasma when the electrode film is formed include an electron beam vapor deposition apparatus (EB vapor deposition apparatus) and a pulse laser vapor deposition apparatus. The method of forming a transparent electrode film using an EB vapor deposition apparatus is referred to as an EB vapor deposition method, and the method of forming a transparent electrode film using a pulse laser vapor deposition apparatus is referred to as a pulse laser vapor deposition method.

As an apparatus capable of realizing a state in which plasma can be reduced during film formation (hereinafter referred to as a plasma-free film forming apparatus), for example, an opposed target sputtering apparatus, an arc plasma vapor deposition apparatus, or the like can be considered.

When the transparent conductive film is an electrode film (for example, the first conductive film), a DC short circuit or an increase in leakage 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 (Transient Conductive Oxide), and the conduction between the film and the electrode film on the opposite side of the transparent conductive film is increased. it is conceivable that. Therefore, when a material having a film quality inferior to that of Al, such as Al, is used for the electrode, the leakage current is unlikely to increase. 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.

Usually, when the conductive film is made thinner than a predetermined value, a rapid increase in resistance value 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 in film thickness is large. Further, 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 amount of light absorbed by the photoelectric conversion layer is increased and the photoelectric conversion ability is improved, which is very preferable.

The photoelectric conversion unit included in the organic photoelectric conversion element of the present invention may include an organic thin film layer other than the photoelectric conversion layer and the photoelectric conversion layer. An organic semiconductor film is generally used for the photoelectric conversion layer constituting the photoelectric conversion unit, but the organic semiconductor film may be one layer or a plurality of layers, and in the case of one layer, a P-type organic semiconductor film, N. A 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, there are about 2 to 10 layers, which is a structure in which any one of a P-type organic semiconductor film, an N-type organic semiconductor film, or a mixed film (bulk heterostructure) thereof is laminated, and the layers are layers. A buffer layer may be inserted in.

In the organic photoelectric conversion element of the present invention, the organic thin film layer other than the photoelectric conversion layer constituting the photoelectric conversion unit is a layer other than the photoelectric conversion layer, for example, an electron transport layer, a hole transport layer, an electron block layer, and a hole block. It is also used as a layer, a crystallization prevention layer, an interlayer contact improvement layer, and the like. In particular, by using it as one or more thin film layers selected from the group consisting of an electron transport layer, a hole transport layer, an electron block layer and a hole block layer, an element that efficiently converts even weak light energy into an electric signal can be obtained. Therefore, it is preferable.

Further, it is generally considered that the organic image sensor aims to improve the performance by reducing the dark current for the purpose of high contrast and power saving. Therefore, a method of inserting a carrier block layer into the layer structure is used, and the element has a multi-layer structure. Therefore, as a material for a photoelectric conversion color element, it is desirable that a thin film can be formed by a method such as resistance heating vapor deposition. The carrier block layer is generally used in the field of organic electronic devices, and each has a function of controlling reverse movement of holes or electrons in the constituent film 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 holes from moving 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 the movement of electrons from the electrode film of the hole transport destination to the photoelectric conversion layer. The electron block layer plays a role of hindering the movement of electrons from the electrode film to the photoelectric conversion layer, preventing recombination in the photoelectric conversion layer, and reducing dark current. The hole block layer has a function of hindering the movement of holes from the electrode film to the photoelectric conversion layer, preventing recombination in the photoelectric conversion layer, and reducing dark current.

FIG. 1 shows a typical element structure of the organic photoelectric conversion element of the present invention, but the present invention is not limited to this structure. In the example of the embodiment of FIG. 1, 1 is an insulating part, 2 is one electrode film, 3 is an electron block layer, 4 is a photoelectric conversion layer, 5 is a hole block layer, 6 is the other electrode film, and 7 is an insulating group. Represents a material or other organic photoelectric conversion element, respectively. Although the transistor for reading is not shown in the figure, it suffices if it is connected to the electrode film of 2 or 6, and if the photoelectric conversion layer 4 is transparent, the side opposite to the side on which the light is incident is opposite. It may be formed on the outside of the electrode film of. The incident of light on the organic photoelectric conversion element can be performed from either the upper part or the lower part unless the components other than the photoelectric conversion layer 4 extremely prevent the light of the main absorption wavelength of the photoelectric conversion layer from being incident. It may be from.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The current and voltage application measurement of the organic photoelectric conversion element in the examples was performed using a semiconductor parameter analyzer 4200-SCS (manufactured by Keithley Instruments). The incident light was irradiated by PVL-3300 (manufactured by Asahi Spectroscopy Co., Ltd.) with a half-value width of 20 nm. The light-dark ratio in the examples means a value obtained by dividing the current value when light irradiation is performed by the current value in a dark place when the same voltage is applied.

[Example 1] Fabrication and evaluation of an organic photoelectric conversion element using compound (1) Resistant heating of compound (1) shown in a specific example on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm). A film was formed to a film thickness of 200 nm by vacuum deposition. Next, aluminum was vacuum-deposited at 100 nm as an electrode to produce the organic photoelectric conversion element of the present invention. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in a dark place was 3.88 × ^10-11 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation having an irradiation light wavelength of 430 nm was performed, the current was 1.29 × 10 ^-5 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 330000.

[Example 2] Fabrication and evaluation of organic photoelectric conversion element using compound (4) Compound (4) shown in a specific example is heat-resisted on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm). A film was formed to a film thickness of 200 nm by vacuum deposition. Next, aluminum was vacuum-deposited at 100 nm as an electrode to produce the organic photoelectric conversion element of the present invention. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in a dark place was 1.93 × 10 ^-10 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation having an irradiation light wavelength of 430 nm was performed, the current was 1.96 × 10 ^-6 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 10000.

[Example 3] Fabrication and evaluation of organic photoelectric conversion element using compound (8) Compound (8) shown in a specific example is heat-resisted on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm). A film was formed to a film thickness of 200 nm by vacuum deposition. Next, aluminum was formed as an electrode to a film thickness of 100 nm to produce the organic photoelectric conversion element of the present invention. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in the dark was 1.16 × ^10-11 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation having an irradiation light wavelength of 430 nm was performed, the current was 3.69 × ^10-6 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 310,000.

[Comparative Example 1] Fabrication and Evaluation of Organic Photoelectric Conversion Element Using DNTT DNT was formed on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm) to a film thickness of 200 nm by resistance heating vacuum deposition. .. Next, aluminum was formed as an electrode to a film thickness of 100 nm to prepare an organic photoelectric conversion element for comparison. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in a dark place was 6.02 × 10 ^-7 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation with an irradiation light wavelength of 430 nm was performed, the current was 2.74 × 10 ^-6 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 4.5.

[Comparative Example 2] Fabrication and Evaluation of Organic Photoelectric Conversion Element Using Coumarin 30 Coumarin 30 was deposited on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm) to 200 nm by resistance heating vacuum deposition. Next, aluminum was formed as an electrode to a film thickness of 100 nm to prepare an organic photoelectric conversion element for comparison. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in a dark place was 5.19 × ^10-6 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation with an irradiation light wavelength of 430 nm was performed, the current was 1.60 × ^10-5 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 3.0.

From the above results, the organic photoelectric conversion element of the present invention of Examples 1 to 3 using the organic compound (DNTT derivative) represented by the formula (1) as the photoelectric conversion unit uses the unsubstituted DNTT as the photoelectric conversion unit. The organic photoelectric conversion element of Comparative Example 1 used and its use as a material for blue light are being studied (for example, NHK Giken R & D / No. 132 / 2012.3.) Comparative Example 2 using coumarin 30 as a photoelectric conversion unit. It is clear that the dark current value is smaller than that of the organic photoelectric conversion element of the above, and the brightness ratio is orders of magnitude higher. That is, when the unsubstituted DNTT or coumarin 30 is used as the photoelectric conversion unit, a practical organic photoelectric conversion element cannot be obtained unless various block layers and the like are used in combination, whereas the equation (1) is used. The organic photoelectric conversion element of the present invention using the represented organic compound (DNTT derivative) as a photoelectric conversion unit exhibits a high light-dark ratio without using various block layers or the like in combination.
Moreover, since the organic photoelectric conversion element of the present invention is sufficiently driven even at a low applied voltage (5V), the material for the organic photoelectric conversion element of the present invention is an organic electronics device more than the existing material for the organic photoelectric conversion element for blue. It is clear that it is useful as a material.

[Example 4] Fabrication and evaluation of an organic photoelectric conversion element using the compound (1) as an organic thin film layer An ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm) is coated with the compound (1) shown in a specific example. ) Was formed to 50 nm by resistance heating vacuum deposition. Next, quinacridone as a photoelectric conversion layer was formed on the organic thin film layer to a film thickness of 100 nm by resistance heating vacuum deposition. Finally, aluminum as an electrode was formed on the photoelectric conversion layer to a film thickness of 100 nm by resistance heating vacuum deposition to produce the organic photoelectric conversion element of the present invention. When a voltage of 5 V was applied using ITO and aluminum as electrodes, the current in a dark place was 1.57 × 10 ^-10 A / cm ² . When a voltage of 5 V was applied and light irradiation was performed at a wavelength of 550 nm, which is the photoelectric conversion wavelength of quinacridone, the current was 1.23 × ^10-5 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 78,000.

[Comparative Example 3] Fabrication and Evaluation of Organic Photoelectric Conversion Element Using Quinacridone Quinacridone was deposited on ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm) to 200 nm by resistance heating vacuum deposition. Next, aluminum was formed as an electrode to a film thickness of 100 nm to prepare an organic 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 5.05 × 10 ^-9 A / cm ² . Further, when a voltage of 5 V was applied and light irradiation with an irradiation light wavelength of 550 nm was performed, the current was 9.22 × ^-6 A / cm ² . The light-dark ratio when a 5 V voltage was applied was 1800.

Examples 4 and 3 are the evaluation results of the photoelectric conversion characteristics when the light of 550 nm, which is the photoelectric conversion wavelength of quinacridone used as the photoelectric conversion unit, is irradiated. However, the compound (1) used in Example 3 is It is an organic compound that selectively absorbs the blue wavelength region of 400 to 500 nm having an absorption edge at 507 nm, and does not respond to irradiation light of 550 nm. That is, Example 3 is an embodiment in which compound (1) is used as an organic thin film layer (various block layers, etc.) other than the photoelectric conversion unit, but quinacridone is compared with Comparative Example 3 in which only quinacridone is used as the photoelectric conversion unit. In Example 4 in which the compound (1) was used as the photoelectric conversion unit and the compound (1) was used as the organic thin film layer other than each photoelectric conversion unit, the light-dark ratio was high. That is, it can be confirmed that the material for an organic photoelectric conversion element of the present invention contributes to the performance improvement of the photoelectric conversion element even when it is used as an organic thin film layer other than the photoelectric conversion layer.
From these results, the material for an organic photoelectric conversion element of the present invention is useful not only as a photoelectric conversion part (photoelectric conversion layer) of an organic photoelectric conversion element but also as an organic thin film layer other than the photoelectric conversion part such as various block layers. It is clear that.

(Fig. 1)
1 Insulation part 2 Upper electrode 3 Electronic block layer 4 Photoelectric conversion layer 5 Hole block layer 6 Lower electrode 7 Insulated base material or other photoelectric conversion element

Claims (10)

An organic photoelectric conversion element using an organic compound represented by the following formula (1).

_{(One of R 1} and R ₂ in the above formula (1) is an aromatic group having an aromatic group, and the other is a hydrogen atom .) The organic photoelectric conversion element according to claim 1, wherein in the formula (1), R ₁ is an aromatic group having an aromatic group and R _{2 is a hydrogen atom.} The organic photoelectric conversion element according to claim 1, wherein in the formula (1), R ₁ is a hydrogen atom and R ₂ is an aromatic group having an aromatic group. The organic photoelectric conversion element according to any one of claims 1 to 3, wherein the maximum absorption of the light absorption band is 400 nm or more and 500 nm or less in a thin film or solid state. A material for an organic photoelectric conversion element containing a compound represented by the following formula (1).

_{(One of R 1} and R ₂ in the above formula (1) is an aromatic group having an aromatic group, and the other is a hydrogen atom .) The material for an organic photoelectric conversion element according to claim 5, wherein the maximum absorption of the light absorption band is 400 nm or more and 500 nm or less in a thin film or solid state. An organic thin film containing the material for an organic photoelectric conversion element according to claim 5 or 6. The organic photoelectric conversion element according to claim 5 or 6, or the organic photoelectric conversion element containing the organic thin film according to claim 7. An optical sensor using the photoelectric conversion element according to any one of claims 1 to 4 and 8. An organic imaging device using the photoelectric conversion element according to any one of claims 1 to 4, and 8.

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