Condensed polycyclic aromatic compounds

Abstract

To provide a fused polycyclic aromatic compound that has small variations in absorption and photoresponsive current within the wavelength range from 400 to 500 nm, an organic thin film including the compound, and an organic semiconductor device including the organic thin film (e.g. an optical sensor and an organic photoelectric converter).SOLUTION: A fused polycyclic aromatic compound is represented by the following formula (1) (where, R1 to R4 independently represent a hydrogen atom or a substituted / unsubstituted aromatic group, and X represents an oxygen atom or a sulfur atom).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a novel fused polycyclic aromatic compound and its use. More specifically, the present invention relates to a fused polycyclic aromatic compound that is a benzothieno[3,2-b][1]benzothiophene (hereinafter abbreviated as "BTBT") derivative, an organic thin film containing the compound, and an organic semiconductor device (photosensor, organic photoelectric conversion element) having the organic thin film. [Background technology]

[0002] Organic electronics devices have been the subject of vigorous research and development in recent years because they can be supplied stably as they do not contain rare metals or other such raw materials, and because they have flexibility not found in inorganic materials and can be manufactured using wet film formation methods. Specific examples of organic electronics devices include organic EL elements, organic solar cell elements, organic photoelectric conversion elements, and organic transistor elements. In addition to these, various applications that take advantage of the characteristics of organic compounds, as well as the performance of the devices themselves, are also being considered.

[0003] Among the above devices, organic photoelectric conversion elements are used in optical sensors and the like, and their use as image sensors is being considered. Three-chip and single-chip imaging elements using inorganic materials are known. While three-chip imaging elements have excellent sensitivity because they separate light into the three primary colors of red, green, and blue using a prism and then perform photoelectric conversion in the imaging device for each wavelength range, miniaturization of the device is difficult. On the other hand, single-chip imaging elements, which have a color filter structure, can be miniaturized, but have inferior resolution compared to three-chip imaging elements. Given these circumstances, organic imaging elements with stacked photoelectric conversion films using organic compounds are currently being considered (Patent Document 1, Patent Document 2). Organic imaging elements with a stacked structure are attractive because they can achieve both miniaturization and high resolution, and are expected to be next-generation imaging devices.

[0004] Materials under consideration for use in the blue photoelectric conversion layer of an organic imaging element having a laminated structure include coumarin 30 (Non-Patent Document 1), porphyrin derivatives (Non-Patent Document 2), and dinaphthothienothiophene derivatives (Patent Document 3, Patent Document 4, Non-Patent Document 3). However, these materials have a problem in that their absorption is not uniform in the wavelength region of 400 to 500 nm, and there is variation in photoelectric conversion efficiency within the blue wavelength region. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-158254 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-303266 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-192966 [Patent Document 4] Japanese Patent Application Publication No. 2018-26559 [Non-patent literature]

[0006] [Non-Patent Document 1] Jpn.J.Appl.Phys,2010,49,111601.1-11160.4 [Non-patent document 2] Jpn.J.Appl.Phys.,2005,44(6A),3743-3747 [Non-patent document 3] Org.Electron.,2015,20,63-68 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to provide a fused polycyclic aromatic compound that exhibits small variations in photoresponse current within a wavelength region of 400 to 500 nm, an organic thin film containing the compound, and an organic semiconductor device (photosensor, organic photoelectric conversion element) having the organic thin film. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to overcome such problems, they discovered that the above problems can be solved by using a novel fused polycyclic aromatic compound having a specific structure, and thus completed the present invention. That is, the present invention (1) The following formula (1)

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[0010] (In formula (1), R1 to R4 each independently represent a hydrogen atom or a substituted or unsubstituted aromatic group, and X represents an oxygen atom or a sulfur atom.) a condensed polycyclic aromatic compound represented by (2) The condensed polycyclic aromatic compound according to the above item (1), wherein R1 to R4 are each independently a hydrogen atom or a substituted or unsubstituted phenyl group. (3) The condensed polycyclic aromatic compound according to the above item (2), wherein R1 and R3 are substituted or unsubstituted phenyl groups, and R2 and R4 are hydrogen atoms. (4) The condensed polycyclic aromatic compound according to the above item (2), wherein R2 and R4 are substituted or unsubstituted phenyl groups, and R1 and R3 are hydrogen atoms. (5) The condensed polycyclic aromatic compound according to the above (2), wherein R1 to R4 are hydrogen atoms. (6) A material for a photoelectric conversion element, comprising the compound according to any one of (1) to (5). (7) An organic thin film containing the compound according to any one of (1) to (5). (8) An optical sensor having the organic thin film according to the preceding item (7). (9) An organic photoelectric conversion element having the organic thin film according to the above item (7), and (10) The organic photoelectric conversion element according to the above (9), which is an organic imaging element. Regarding. [Effects of the Invention]

[0011] By using the fused polycyclic aromatic compound represented by formula (1) of the present invention, it is possible to provide an organic semiconductor device (photosensor, organic photoelectric conversion element) having small variations in photoresponse current within a wavelength range of 400 to 500 nm. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 shows a cross-sectional view illustrating an embodiment of the organic photoelectric conversion element of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. The description of the constituent elements described herein is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples.

[0014] The compound of the present invention is represented by the following formula (1). In formula (1), R1 to R4 each independently represent a hydrogen atom or a substituted or unsubstituted aromatic group, and X represents an oxygen atom or a sulfur atom.

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[0016] The aromatic group represented by R1 to R4 in formula (1) is a residue obtained by removing one hydrogen atom from the aromatic ring of an aromatic compound. Specific examples of the aromatic group include aromatic hydrocarbon groups such as a phenyl group, a biphenyl group, and a naphthyl group; heterocyclic groups such as a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, an isoquinolyl group, a pyrrolyl group, an indolenyl group, an imidazolyl group, a carbazolyl group, a thienyl group, a furyl group, a pyranyl group, and a pyridonyl group; and condensed heterocyclic groups such as a benzoquinolyl group, a benzofuranyl group, and a benzothienyl group. The aromatic group represented by R1 to R4 in formula (1) is preferably an aromatic hydrocarbon group or a condensed heterocyclic group, more preferably a phenyl group, a biphenyl group, a naphthyl group, a benzothienyl group or a benzofuranyl group, still more preferably a phenyl group or a benzothienyl group, and particularly preferably a phenyl group.

[0017] The "substituted or unsubstituted aromatic group" represented by R1 to R4 in formula (1) means an aromatic group in which a hydrogen atom of the aromatic group is substituted with a substituent, a monovalent atom, etc., or an aromatic group in which a hydrogen atom of the aromatic group is not substituted with a substituent, a monovalent atom, etc. The number and substitution positions of the substituents of the aromatic group are not particularly limited. The substituents possessed by the aromatic group represented by R1 to R4 in formula (1) are not limited, and examples thereof include an alkyl group (preferably an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an aromatic group (specific examples are the same as those described above in the "specific examples of the aromatic group represented by R1 to R4 in formula (1)"), a halogen atom, a hydroxy group, a mercapto group, a nitro group, an alkyl-substituted amino group (a mono- or di-alkyl-substituted amino group having the alkyl group described above), an aryl-substituted amino group (a mono- or di-aromatic-substituted amino group having the aromatic group described above), an unsubstituted amino group (NH group), an acyl group (a substituent in which the alkyl group or the aromatic hydrocarbon group is bonded to a carbonyl group), an alkoxycarbonyl group (a substituent in which the alkoxy group is bonded to a carbonyl group described above), a cyano group, an isocyano group, and the like.

[0018] In formula (1), it is preferable that R1 to R4 are both hydrogen atoms and R2 and R4 are both the same substituted or unsubstituted aromatic group, or that R1 and R3 are both the same substituted or unsubstituted aromatic group and R2 and R4 are both hydrogen atoms. In another embodiment, it is preferable that all of R1 to R4 are hydrogen atoms. It should be noted that formula (1) merely shows one resonance structure, and the fused polycyclic aromatic compound of the present invention is not limited to the resonance structure shown in formula (1).

[0019] Specific examples of the fused polycyclic aromatic compound represented by formula (1) are shown below, but the compounds of the present invention are not limited to these. Note that the structural formula shown as a specific example merely represents one of the resonance structures, and the compounds are not limited to the resonance structure shown.

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[0026] The compound represented by formula (1) can be synthesized by the same reaction steps as in known methods (e.g., Japanese Patent No. 6161168). The method for purifying the compound after synthesis is not particularly limited, and for example, washing, recrystallization, column chromatography, vacuum sublimation, etc. can be employed, and these methods can be combined as necessary. An example of a synthesis flow for a compound represented by formula (1) is described below. In the following flow, R1 to R4 and X have the same meanings as R1 to R4 and X in formula (1), Me represents a methyl group, and TMS represents a trimethylsilyl group.

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[0028] The material for a photoelectric conversion device of the present invention contains the compound represented by formula (1) of the present invention. The material for photoelectric conversion elements of the present invention may contain components other than the compound represented by formula (1) as long as the effects of the present invention are not impaired. However, since the material for photoelectric conversion elements of the present invention preferably absorbs light in the blue wavelength region of 400 nm or more and 500 nm or less and has little absorption of light with wavelengths exceeding 500 nm, it is preferable that the compound used in combination has similar light absorption properties as the above. The content of the compound represented by formula (1) in the material for photoelectric conversion elements is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 98% by mass or more, and most preferably 99% by mass or more. In addition, a plurality of compounds encompassed by formula (1) may be used in combination in the material for a photoelectric conversion element.

[0029] The organic thin film of the present invention includes the material for a photoelectric conversion device of the present invention. The thickness of the organic thin film may be selected depending on the application, but is usually 1 nm to 1 μm, preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. Methods for forming organic thin films include dry processes such as vapor deposition (methods using photoelectric conversion element materials as they are) and various solution processes (methods using solutions in which photoelectric conversion element materials are dissolved in organic solvents, etc.), but solution processes are preferred. Solution processes include, for example, spin coating, drop casting, dip coating, spraying, relief printing methods such as flexographic printing and resin relief printing, offset printing, dry offset printing, and lithographic printing methods such as pad printing, intaglio printing methods such as gravure printing, screen printing, mimeograph printing, and stencil printing methods such as ring graph printing, inkjet printing, microcontact printing, and methods combining a plurality of these methods. When forming a film using a solution process, it is preferable to evaporate the solvent after the above coating and printing to form a thin film.

[0030] The organic photoelectric conversion element of the present invention includes the material for photoelectric conversion elements of the present invention or the organic thin film of the present invention. The material for photoelectric conversion elements and the organic thin film are preferably used in the photoelectric conversion layer of a blue light photoelectric conversion element. The photoelectric conversion layer of the blue light photoelectric conversion element is formed by the general dry film formation method or wet film formation method described above, and is an organic thin film having a maximum absorption of 400 nm or more and 520 nm or less, preferably 420 nm or more and 500 nm or less, which is a band that absorbs light in the visible light region (380 nm to 780 nm) observed by wavelength-absorbance measurement using a spectrophotometer, i.e., a light absorption band, and which means the wavelength position of the highest absorbance in the main light absorption band, generally called λmax.

[0031] An organic photoelectric conversion element is an element in which a photoelectric conversion unit (film) is disposed between a pair of opposing electrode films, 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 signal corresponding to the charge is read out by a semiconductor, indicating the amount of incident light corresponding to the absorption wavelength of the photoelectric conversion film. A readout transistor may be connected to the electrode film on the side where light is not incident. When multiple photoelectric conversion elements are arranged in an array, they indicate not only the amount of incident light but also the incident position information, thereby functioning as an imaging element. Furthermore, if a photoelectric conversion element located closer to the light source does not block (transmits) the absorption wavelength of a photoelectric conversion element located behind it when viewed from the light source side, multiple photoelectric conversion elements may be stacked.

[0032] The electrode film of the organic photoelectric conversion element plays a role of extracting holes from the photoelectric conversion layer or other organic thin film layers and collecting them when the photoelectric conversion layer included in the photoelectric conversion section described later has hole transport properties or when an organic thin film layer other than the photoelectric conversion layer is a hole transport layer having hole transport properties, and also plays a role of extracting electrons from the photoelectric conversion layer or other organic thin film layers and ejecting them when the photoelectric conversion layer included in the photoelectric conversion section has electron transport properties or when an organic thin film layer is an electron transport layer having electron transport properties. Therefore, materials that can be used as the electrode film are not particularly limited as long as they have a certain degree of conductivity, but are preferably selected in consideration of adhesion to adjacent photoelectric conversion layers and other organic thin film layers, electron affinity, ionization potential, stability, etc. Materials that can be used as electrode films include, for example, conductive metal oxides such as tin oxide (NESA), indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickel, and tungsten; inorganic conductive materials such as copper iodide and copper sulfide; conductive polymers such as polythiophene, polypyrrole, and polyaniline; and carbon. These materials may be used in combination, or 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 unnecessarily interfere with the light reception of the photoelectric conversion element. However, it is preferable to use a substrate with as high a conductivity as possible from the viewpoint of the signal strength and power consumption of the photoelectric conversion element. For example, an ITO film with a sheet resistance of 300 Ω / □ or less functions satisfactorily as an electrode film. However, since commercially available substrates with ITO films with conductivities of only a few Ω / □ are available, it is desirable to use a substrate with such high conductivity. The thickness of the ITO film (electrode film) can be selected arbitrarily taking into account conductivity, but is usually about 5 to 500 nm, preferably about 10 to 300 nm. Methods for forming films such as ITO include conventionally known vapor deposition methods, electron beam methods, sputtering methods, chemical reaction methods, and coating methods. The ITO film provided on the substrate may be subjected to UV-ozone treatment, plasma treatment, or the like, as needed.

[0033] Furthermore, when multiple 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 must transmit light of wavelengths other than the light detected by each photoelectric conversion layer, and it is preferable to use a material for the electrode film that transmits 90% or more of the incident light, and it is more preferable to use a material that transmits 95% or more of the light.

[0034] The electrode film is preferably produced in a plasma-free environment. By producing these electrode films in a plasma-free environment, the influence of plasma on the substrate on which the electrode film is formed is reduced, thereby improving the photoelectric conversion characteristics of the photoelectric conversion element. Here, plasma-free means a state in which no plasma is generated during the deposition of 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, thereby reducing the amount of plasma that reaches the substrate.

[0035] Examples of devices that do not generate plasma when forming an electrode film include electron beam deposition devices (EB deposition devices), pulsed laser deposition devices, etc. A method of forming a transparent electrode film using an EB deposition device is called an EB deposition method, and a method of forming a transparent electrode film using a pulsed laser deposition device is called a pulsed laser deposition method.

[0036] Apparatuses capable of realizing a state in which plasma can be reduced during film formation (hereinafter referred to as plasma-free film formation apparatuses) include, for example, facing target sputtering apparatuses and arc plasma deposition apparatuses.

[0037] When a transparent conductive film is used as an electrode film (e.g., the first conductive film), DC shorts or increased leakage current may occur. One of the reasons for this is thought to be that fine cracks that occur in the photoelectric conversion layer are covered by a dense film such as TCO (Transparent Conductive Oxide), increasing the conductivity between the transparent conductive film and the electrode film on the opposite side. Therefore, when a material with inferior film quality, such as Al, is used for the electrode, an increase in leakage current is unlikely to occur. By controlling the film thickness of the electrode film according to the film thickness (depth of the cracks) of the photoelectric conversion layer, the increase in leakage current can be suppressed.

[0038] Typically, if the conductive film is made thinner than a predetermined value, a rapid increase in resistance occurs. The sheet resistance of the conductive film in the photoelectric conversion element for a photosensor of this embodiment is typically 100 to 10,000 Ω / □, allowing for a high degree of freedom in film thickness. Furthermore, the thinner the transparent conductive film, the less light it absorbs, and generally the higher the light transmittance. Higher light transmittance is highly desirable because it increases the amount of light absorbed by the photoelectric conversion layer and improves photoelectric conversion performance.

[0039] The photoelectric conversion section of the organic 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 constituting the photoelectric conversion section, and the organic semiconductor film may be a single layer or multiple layers. In the case of a single 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 multiple layers, the organic semiconductor film may be about 2 to 10 layers, and may have 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 stacked, with a buffer layer optionally inserted between the layers.

[0040] 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 part can also be used as a layer other than the photoelectric conversion layer, for example, an electron transport layer, a hole transport layer, an electron blocking layer, a hole blocking layer, a crystallization preventing layer, or an interlayer contact improving layer. 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 blocking layer, and a hole blocking layer, it is preferable to obtain an element that can efficiently convert even weak light energy into an electric signal.

[0041] In addition, organic imaging devices are generally considered to improve performance by reducing dark current in order to achieve high contrast and power savings. For this reason, a technique of inserting a carrier blocking layer into the layer structure is used, resulting in a multilayer structure for the device. Therefore, it is desirable that materials for photoelectric conversion color devices be capable of thin film formation using techniques such as resistance heating deposition. The above-mentioned carrier blocking layers are commonly used in the field of organic electronics devices and have the function of controlling the reverse migration of holes or electrons within the constituent films of the device, respectively.

[0042] The electron transport layer transports electrons generated in the photoelectric conversion layer to the electrode film and blocks holes from moving from the electrode film to which the electrons are transported to the photoelectric conversion layer. The hole transport layer transports generated holes from the photoelectric conversion layer to the electrode film and blocks electrons from moving from the electrode film to which the holes are transported to the photoelectric conversion layer. The electron blocking layer prevents electrons from moving from the electrode film to the photoelectric conversion layer, preventing recombination within the photoelectric conversion layer and reducing dark current. The hole blocking layer prevents holes from moving from the electrode film to the photoelectric conversion layer, preventing recombination within the photoelectric conversion layer and reducing dark current.

[0043] FIG. 1 shows a typical device structure of an organic photoelectric conversion element of the present invention, but the present invention is not limited to this structure. In the embodiment shown in FIG. 1, 1 represents an insulating portion, 2 represents one electrode film, 3 represents an electron blocking layer, 4 represents a photoelectric conversion layer, 5 represents a hole blocking layer, 6 represents the other electrode film, and 7 represents an insulating substrate or another organic photoelectric conversion element. Although a readout transistor is not shown in the figure, it may be connected to the electrode film 2 or 6. Furthermore, if the photoelectric conversion layer 4 is transparent, it may be formed on the outside of the electrode film on the side opposite to the light incident side. Light may be incident on the organic photoelectric conversion element from either the top or bottom, as long as the components other than the photoelectric conversion layer 4 do not excessively obstruct the incidence of light of the main absorption wavelength of the photoelectric conversion layer. [Example]

[0044] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The structures of the compounds described in the synthesis examples were determined by mass spectrometry and nuclear magnetic resonance spectrometry (NMR) as necessary. Measurements of applied current and voltage for the organic photoelectric conversion elements in the examples were carried out using a PVL-3300 (manufactured by Asahi Spectroscopy) under irradiation conditions of an irradiation light intensity of 130 μW and a half-width of 20 nm, and using a semiconductor parameter analyzer 4200-SCS (manufactured by Keithley Instruments) in the range of 380 to 550 nm.

[0045] Example 1 (Synthesis of fused polycyclic aromatic compounds of the present invention) In a nitrogen atmosphere, PdCl2(PPh3)2 (14 mg, 0.02 mmol) was added to a degassed solution of intermediate (1-6) (0.5 mmol) and NaOAc (82 mg, 1.0 mmol) in DMAc (25 ml), and the mixture was stirred at 140°C for 15 hours. The reaction solution obtained above was cooled to room temperature, and the solid was collected by filtration and washed with water and acetone. The crude product obtained above was purified by sublimation to obtain a yellow solid of a fused polycyclic aromatic compound represented by formula (A-22). (Yield: 14%) The molecular weight of the condensed polycyclic aromatic compound represented by formula (A-22) obtained above was measured, and the results were as follows. EI-MS(m / z):672[M] +

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[0047] Example 2 (Synthesis of fused polycyclic aromatic compounds of the present invention) In a nitrogen atmosphere, PdCl2(PPh3)2 (14 mg, 0.02 mmol) was added to a degassed solution of intermediate (1-7) (0.5 mmol) and NaOAc (82 mg, 1.0 mmol) in DMAc (25 ml), and the mixture was stirred at 140°C for 15 hours. The reaction solution obtained above was cooled to room temperature, and the solid was collected by filtration and washed with water and acetone. The crude product obtained above was purified by sublimation to obtain a yellow solid of a fused polycyclic aromatic compound represented by formula (A-1). (Yield: 12%) The molecular weight of the condensed polycyclic aromatic compound represented by formula (A-1) obtained above was measured, and the results were as follows. EI-MS(m / z):704[M] +

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[0049] Example 3 (Preparation of organic photoelectric conversion element of the present invention) The fused polycyclic aromatic compound represented by formula (A-22) obtained in Example 1 was formed into a film having a thickness of 100 nm on an ITO transparent conductive glass (manufactured by Geomatec Co., Ltd., ITO film thickness 150 nm) by resistance heating vacuum deposition. Next, a 100 nm thick aluminum film was formed as an electrode under vacuum to prepare an organic photoelectric conversion element of the present invention.

[0050] Comparative Example 1 (Preparation of Comparative Organic Photoelectric Conversion Element) A comparative organic photoelectric conversion element was prepared in the same manner as in Example 3, except that a compound represented by the following formula (B-1), which was synthesized by a known method, was used instead of the fused polycyclic aromatic compound represented by formula (A-22).

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[0052] Comparative Example 2 (Preparation of Comparative Organic Photoelectric Conversion Element) A comparative organic photoelectric conversion element was prepared in the same manner as in Example 3, except that a compound represented by the following formula (B-2), which was synthesized by a known method, was used instead of the fused polycyclic aromatic compound represented by formula (A-22).

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[0054] Comparative Example 3 (Preparation of Comparative Organic Photoelectric Conversion Element) A comparative organic photoelectric conversion element was prepared in the same manner as in Example 3, except that a compound represented by the following formula (B-3), which was synthesized by a known method, was used instead of the fused polycyclic aromatic compound represented by formula (A-22).

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[0056] (Evaluation of photocurrent density at each wavelength of organic photoelectric conversion element) The photocurrent density was measured when a voltage of 5 V was applied to the organic photoelectric conversion elements of the present invention and comparative examples obtained in Example 3 and Comparative Examples 1 to 3 while irradiating them with light of 380 nm to 550 nm. The measurement results for each organic photoelectric conversion element obtained above were evaluated as "Good" if the photocurrent density value at each frequency was 75% or more of the highest photocurrent density value in the wavelength range of 400 to 500 nm, and as "Poor" if it was less than 75%. The results are shown in Table 1.

[0057] [Table 1]

[0058] From the results in Table 1, the organic photoelectric conversion element of the present invention has less variation in photoresponse current at each wavelength from 400 to 500 nm than the comparative organic photoelectric conversion element, which clearly shows that the organic photoelectric conversion element including the organic thin film of the present invention exhibits a uniform and excellent photoresponse current at any wavelength in the wavelength region of blue light. [Industrial Applicability]

[0059] By using the fused polycyclic aromatic compound represented by formula (1) of the present invention, it is possible to provide an organic semiconductor device (photosensor, organic photoelectric conversion element) having small variations in photoresponse current within a wavelength range of 400 to 500 nm. [Explanation of symbols]

[0060] (Figure 1) 1 Insulation section 2 Upper electrode 3 Electron Blocking Layer 4 Photoelectric conversion layer 5. Hole-blocking layer 6 Lower electrode 7. Insulating substrate or other photoelectric conversion element

Claims

1. The following formula (1) 【Chemistry 1】 (In formula (1), R １ ~R ４ represents a hydrogen atom, and X represents an oxygen atom or a sulfur atom. A condensed polycyclic aromatic compound represented by the formula:

2. A material for a photoelectric conversion device, comprising the compound according to claim 1.

3. An organic thin film comprising the compound of claim 1.

4. An optical sensor comprising the organic thin film according to claim 3 .

5. An organic photoelectric conversion element comprising the organic thin film according to claim 3 .

6. The organic photoelectric conversion element according to claim 5 , which is an organic imaging element.

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