Photoelectric conversion materials, photodiodes and image sensors

Abstract

To provide a photoelectric conversion element with excellent durability and a composition for forming a photoelectric conversion layer.SOLUTION: A photoelectric conversion material having a structure represented by a specific general formula. [In the general formula, A2 represents a nitrogen atom or a methine group; when A2 is the nitrogen atom, A1 represents an oxygen atom or a dicyanomethylene group; when A2 is the methine group, A1 represents the dicyanomethylene group. R1 represents an aryl group that may have a substituent. R11, R12, R13, and R14 each independently represent a halogen atom, a cyano group, or a hydrogen atom].SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion material, and a photodiode and an image sensor using the same. [Background technology]

[0002] Photoelectric conversion elements that convert light energy into electrical energy are used in solar cells, optical sensors, copiers, etc. Among these, optical sensors that are sensitive to near-infrared light as light energy are attracting attention for their potential applications in night vision, distance measurement, security, semiconductor wafer inspection, etc. Organic semiconductors using organic dyes are expected to be used as photoelectric conversion materials sensitive to near-infrared light because the light absorption wavelength can be adjusted by the molecular structure and they have a large light absorption coefficient.

[0003] For example, Patent Document 1 discloses an organic photoelectric conversion element having an organic compound layer containing a compound in which an aryl group having a diarylamino group and an indandione group are bonded with an ethylene structure. Patent Document 2 discloses an organic photoelectric conversion element having a photoelectric conversion section in which a thiophene group substituted with an aryl group having a diarylamino group and an indene group substituted with a monodicyanomethylene group are condensed with an ethylene group. However, the photoelectric conversion elements disclosed in Patent Documents 1 and 2 are insufficiently sensitive for applications requiring higher sensitivity to light in the near infrared region, and higher sensitivity is required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-174921 A [Patent Document 2] JP 2018-014426 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a photodiode having high sensitivity to light in the near infrared region. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention relates to a photoelectric conversion material having a structure represented by the following general formula (1). General formula (1) [ka]

[0007] [In general formula (1), A 2 represents a nitrogen atom or a methine group; A 2 When is a nitrogen atom, A 1 represents an oxygen atom or a dicyanomethylene group; A 2 When is a methine group, A 1 R represents a dicyanomethylene group. 1 R represents an aryl group which may have a substituent. 11 , R 12 , R 13 and R 14 each independently represents a halogen atom, a cyano group, or a hydrogen atom.

[0008] The present invention also provides a method for producing a 2 is a nitrogen atom, and A 1 is a dicyanomethylene group.

[0009] The present invention also provides R 1 is an arylaminoaryl group having a substituent.

[0010] The present invention also relates to a photodiode having an organic photoelectric conversion layer containing the above photoelectric conversion material.

[0011] The present invention also relates to an image sensor comprising the above-mentioned photodiode. Effect of the Invention

[0012] According to the present invention, a photodiode with excellent sensitivity can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described. <Photoelectric conversion material represented by general formula (1)> The photoelectric conversion material represented by the general formula (1) used in the present invention will be described below. The groups in the general formula (1) will be described below. R 1 The substituent in the optionally substituted aryl group represented by the following formula (I) is preferably an electron-donating group, more preferably an amino group, an alkoxy group, an aryloxy group, or the like, which may be substituted. The substituent in the amino group which may have a substituent is preferably an electron donating group, more preferably an alkyl group, an aryl group, etc. From the viewpoint of the stability of the photoelectric conversion material, the amino group is preferably a tertiary amine, and therefore, it is preferable that both of the two hydrogen atoms on the amino group are substituted by substitution. These substituents may be bonded to each other to form a ring structure. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, a decyl group, etc. From the viewpoint of stacking properties and stability of the photoelectric conversion material, an ethyl group is preferred. Examples of the aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-anthryl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 1-pyrenyl group, a 2-pyrenyl group, a 2-perylenyl group, a 3-perylenyl group, a 2-fluorenyl group, and a 3-fluorenyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a hexyloxy group, an octyloxy group, and a decyloxy group. Examples of the aryloxy group include a phenoxy group, a 1-naphthyloxy group, and a 2-naphthyloxy group. R 11 , R 12 , R 13 and R 14 Examples of the halogen atom in include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0014] To improve sensitivity to long wavelength light, A 2 is a nitrogen atom, and A 1 is preferably a dicyanomethylene group, and further preferably R 1 It is more preferable that R is an arylaminoaryl group which may have a substituent. 1 is preferably a 4-arylaminoaryl group which may have a substituent. Examples of the 4-arylaminoaryl group include a 4-diphenylaminophenyl group, a 4-[bis(4-methoxyphenyl)amino]phenyl group, a 4-[bis(4-ethylphenyl)amino]phenyl group, a 4-[bis(4-methylphenyl)amino]phenyl group, and a 4-ethyl(phenyl)aminophenyl group.

[0015] From the viewpoint of ease of synthesis of compounds having active methylene groups and durability of dyes, R 12 and R 13 is preferably unsubstituted or substituted with a chlorine atom, a bromine atom, an iodine atom or a cyano group.

[0016] <Organic photoelectric conversion layer> The organic photoelectric conversion layer contributes to charge separation and has the function of transporting electrons and holes generated by absorption of electromagnetic waves (mainly light) toward electrodes in the opposite directions, respectively. The organic photoelectric conversion layer used in the present invention contains a photoelectric conversion material represented by general formula (1).

[0017] <Method of manufacturing organic photoelectric conversion layer> The photoelectric conversion material represented by general formula (1) can be deposited by any suitable method, optionally in the form of a blend or mixture, together with other compounds or additives. Liquid coating is more desirable than vacuum deposition techniques. Liquid deposition methods are particularly preferred. Formulations containing the photoelectric conversion material represented by general formula (1) allow the use of many liquid coating techniques. Preferred deposition techniques include, but are not limited to, dip coating, spin coating, inkjet printing, nozzle printing, letterpress printing, screen printing, gravure printing, doctor blade coating, roller printing, reverse roller printing, offset lithography printing, dry offset lithography printing, flexography printing, web printing, spray coating, curtain coating, brush coating, slot die coating or pad printing. For the production of organic photoelectric conversion layers, deposition techniques for large area coating, such as spin coating, slot die coating and spray coating, are preferred.

[0018] <Organic solvent> As the organic solvent used for liquid coating, a known organic solvent can be used, but it is preferable to use one that can dissolve or uniformly disperse the photoelectric conversion material in order to form a uniform organic photoelectric conversion layer.Specific examples include, but are not limited to, alcohol-based solvents such as 1,3-butanediol and 1,3-butylene glycol, ketone-based solvents such as methyl isobutyl ketone and cyclohexanone, and ester-based solvents such as isoamyl acetate and propylene glycol monomethyl ether acetate.The organic solvent can be used alone or in combination of two or more kinds.

[0019] <Photodiode> The photodiode of the present invention is characterized in that it has an organic photoelectric conversion layer between a pair of electrodes, and the organic photoelectric conversion layer contains a photoelectric conversion material represented by general formula (1). The photodiode can be manufactured by a known element configuration and manufacturing method. Examples of materials for the electrodes constituting the photodiode include known materials such as conductive metal oxides such as tin oxide, zinc oxide, indium oxide, and indium tin oxide (ITO), and metals such as gold, silver, platinum, chromium, nickel, lithium, indium, aluminum, calcium, and magnesium.

[0020] <Image sensor> The image sensor of the present invention arranges a large number of photodiodes of the present invention in an array and recognizes information on not only the amount of incident light but also the position of incidence by applying a voltage between a pair of electrodes from outside the photodiode. EXAMPLES

[0021] The present invention will be specifically described below based on examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass". Unless otherwise specified, all measurements were performed at 25°C.

[0022] <Synthesis of photoelectric conversion materials> The photoelectric conversion material was identified using MALDI TOF-MS spectroscopy (hereafter abbreviated as "TOF-MS"). The MALDI TOF-MS spectrum was obtained using a Bruker Daltonics MALDI mass spectrometer AutoflexIII, and the photoelectric conversion material was identified based on the agreement between the molecular ion peak of the obtained mass spectrum and the mass number obtained by calculation.

[0023] [Example 1] <Synthesis of photoelectric conversion material 1> 19 parts of 1,3-bis(dicyanomethylidene)indan as a compound having an active methylene group and 18 parts of 4-nitroso-N,N-diphenylaniline as a nitroso compound were added to 300 parts of dehydrated ethanol and heated to 75° C. for 30 minutes. After cooling, the resulting solid was filtered and purified by column chromatography to obtain photoelectric conversion material 1.

[0024] [Examples 2 to 15] <Synthesis of photoelectric conversion materials 2-15> Except for changing the compound having an active methylene group and the nitroso compound, photoelectric conversion materials 2 to 15 were synthesized in the same manner as in Example 1. The structural formulae of the compound having an active methylene group and the nitroso compound used in the synthesis are shown in Table 1.

[0025] [Table 1]

[0026] [Example 16] <Synthesis of photoelectric conversion material 16> 19 parts of 1,3-bis(dicyanomethylidene)indane as a compound having an active methylene group and 18 parts of N,N-diphenylaminobenzaldehyde as a compound having a formyl group were added to 300 parts of dehydrated ethanol and heated to 75° C. for 30 minutes. After cooling, the resulting solid was filtered and purified by column chromatography to obtain photoelectric conversion material 16.

[0027] <Synthesis of comparative materials 1 to 3> Similar to the photoelectric conversion material, a compound having an active methylene group and a compound having a formyl group were condensed to synthesize comparative materials 1 to 3. The structural formulae of the compound having a formyl group and the compound having an active methylene group used are shown in Table 2.

[0028] [Table 2]

[0029] Photoelectric conversion materials 1 to 16 are listed in Table 3. [Table 3]

[0030] The structures of comparative materials 1 to 3 are shown in Table 4. [Table 4]

[0031] <Preparation of composition for making photodiode (PD)> Photoelectric conversion materials 1 to 16 and comparative materials 1 to 3 were each mixed with dichlorobenzene to a concentration of 1%, to obtain photodiode (PD) forming compositions 1 to 16 and comparative photodiode (PD) forming compositions 1 to 3.

[0032] [Examples 101 to 116] <Creating a Photodiode (PD)> On a cleaned glass plate with an ITO electrode, PEDOT:PSS (poly(3,4-ethylenedioxy)-2,5-thiophene / polystyrenesulfonic acid, Baytron P manufactured by Bayer) was formed as a charge injection buffer layer by spin coating to a thickness of 80 nm. Next, a composition for producing a photodiode shown in Table 3 was formed into a film of 80 nm by spin coating to form a photoelectric conversion layer. Furthermore, Al was vapor-deposited on the film to a thickness of 100 nm to form an electrode, and photodiodes (PD) 1 to 16 and comparative photodiodes 1 to 3 were obtained.

[0033] <Photodiode evaluation> The voltage-current curve when the manufactured photodiode was irradiated with near-infrared light was measured in the range of -2 V to 2 V. A light-emitting diode (LED) with an emission wavelength of 780 nm was used as the light source of near-infrared light, and the output was 1 mW / cm 2 The measurement was performed by irradiating the sample with a light intensity of 0.04 cm2. 2A photomask was applied so that the initial bright / dark current ratio was obtained. The current value at a voltage of -1V was read, and the initial bright / dark current ratio was determined. The bright / dark current ratio was judged according to the following criteria. The judgment results are shown in Table 5. The higher the bright / dark current ratio, the better it is, and the better the sensitivity. A criterion of 2 or more is within the practical range. (Judgment criteria) 4: 100 or more 3: 50 to less than 100 2: 20 to 50 1: Less than 20

[0034] [Table 5]

[0035] A 1 is a dicyanoethylene group, A 2 It can be seen that the current ratio is large when the R 1 It can be seen that the material in which the aryl group of A is substituted with an arylamino group is better. 1 , A 2 The R 1 The current ratio of photoelectric conversion materials that have a strong electron donating group in the part tends to be good, and the distribution of charge in the molecule is A 1 , A 2 It is considered that the current ratio increases when the capacitance is increased in the upper part.

[0036] <Fabrication and evaluation of image sensors> Sixteen photodiodes (PD1) shown in Table 3 were fabricated. Next, an image sensor was fabricated by arranging the photoelectric conversion elements (PD1) in a 4 x 4 arrangement on a flat surface. The fabricated image sensor was placed facing an image projected onto a screen installed in a darkroom using an LED with an emission wavelength of 780 nm as a light source. A voltage of -1 V was sequentially applied between the electrodes to determine the current ratio in the dark and when an image was projected. The current ratios determined for each photoelectric conversion element reproduced the brightness and darkness of the projected image, and it was confirmed that the image sensor worked.

Claims

1. A photoelectric conversion material having a structure represented by the following general formula (1): General formula (1) 【Chemistry 1】 [In general formula (1), A 2 represents a nitrogen atom, and A represents a dicyanomethylene group. 1 R represents an arylaminoaryl group having a substituent. 11 , R 12 , R 13 and R 14 each independently represents a halogen atom, a cyano group, or a hydrogen atom.

2. A photodiode comprising an organic photoelectric conversion layer containing the photoelectric conversion material according to claim 1.

3. 3. An image sensor comprising the photodiode according to claim 2.

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