Photodetection element and image sensor

Abstract

This photodetection element comprises: a first electrode layer 11, a second electrode layer 12, a photoelectric conversion layer 13 located between the first electrode layer 11 and the second electrode layer 12, and an electron transport layer 21 located between the first electrode layer 11 and the photoelectric conversion layer 13, wherein the photoelectric conversion layer 13 includes quantum dots, the electron transport layer 21 contains a polymer that has a polymer chain including a structural unit derived from an n-type organic semiconductor.

Description

Photodetector and Image Sensor

[0001] The present invention relates to a photodetector and an image sensor.

[0002] In recent years, in areas such as smartphones, surveillance cameras, and in-vehicle cameras, attention has been focused on photodetectors capable of detecting light in the infrared region.

[0003] Conventionally, silicon photodiodes using silicon wafers as the material of the photoelectric conversion layer have been used for photodetectors used in image sensors and the like. However, silicon photodiodes have low sensitivity in the infrared region with a wavelength of 900 nm or more.

[0004] In addition, InGaAs-based semiconductor materials known as near-infrared light receiving elements require a very high-cost process such as an epitaxial growth process or a substrate bonding process in order to achieve high quantum efficiency, which is an issue, and their spread has not advanced.

[0005] In recent years, research on quantum dots has been underway. Patent Documents 1 and 2 describe optical sensors having a photoelectric conversion film containing quantum dots.

[0006] International Publication No. 2022 / 054736 International Publication No. 2021 / 161941

[0007] In recent years, with the demand for performance improvement of image sensors and the like, further improvement has been demanded for various characteristics required for the photodetectors used therein. For example, one of the characteristics required for a photodetector is to have a high external quantum efficiency with respect to light of the wavelength to be detected by the photodetector. By increasing the external quantum efficiency of the photodetector, the detection accuracy of light in the photodetector can be increased.

[0008] In addition, in a photodetector, it is preferable that the dark current is small. By reducing the dark current of the photodetector, a higher signal-to-noise ratio (S / N ratio) can be obtained in the image sensor. The dark current is the current that flows when light is not irradiated.

[0009] When the present inventors intensively studied the optical sensors described in Patent Documents 1 and 2, it was found that these optical sensors had a large decrease in external quantum efficiency when irradiated with light for a long time.

[0010] An object of the present invention is to provide a photodetector and an image sensor with less decrease in external quantum efficiency when irradiated with light for a long time.

[0011] According to the study by the present inventors, it has been found that the above object can be achieved by adopting the following configuration, and the present invention has been completed. The photodetector of the present invention includes a first electrode layer, a second electrode layer, a photoelectric conversion layer located between the first electrode layer and the second electrode layer, and an electron transport layer located between the first electrode layer and the photoelectric conversion layer. The photoelectric conversion layer contains quantum dots, and the electron transport layer contains a polymer having a polymer chain containing a structural unit derived from an n-type organic semiconductor.

[0012] According to the present invention, a photodetector with a small decrease in external quantum efficiency when irradiated with light for a long time can be obtained.

[0013] It is a cross-sectional schematic view of the photodetector of the present embodiment. It is a diagram showing an example of an imaging system using the photodetector according to the present embodiment. It is a diagram showing the configuration of the imaging system and the moving body according to the present embodiment. It is a diagram showing the configuration of the imaging system and the moving body according to the present embodiment.

[0014] <<Photodetector>> The photodetector of the present embodiment includes a first electrode layer, a second electrode layer, a photoelectric conversion layer located between the first electrode layer and the second electrode layer, and an electron transport layer located between the first electrode layer and the photoelectric conversion layer. The photoelectric conversion layer contains quantum dots, and the electron transport layer contains a polymer having a polymer chain containing a structural unit derived from an n-type organic semiconductor. The photodetector of the present embodiment may be a photoelectric conversion element.

[0015] Here, according to the study by the present inventors, the reasons for being able to provide a photodetector and an image sensor that can maintain a high external quantum efficiency even when irradiated with light for a long time are considered as follows.

[0016] The inventors believe that the reason why high external quantum efficiency can be maintained even when light is irradiated for a long time is as follows: The material that becomes the charge transport site in the electron transport layer is an n-type organic semiconductor that is less likely to cause oxidative degradation of quantum dots and less likely to reduce external quantum efficiency, and furthermore, because the n-type organic semiconductor is polymerized and fixed, there is no bias in the charge transport sites in the electron transport layer.

[0017] It is presumed that the external quantum efficiency is maintained because there is no bias in the electron transport sites, resulting in fewer charge traps in the electron transport layer and fewer charge traps at the interface between the quantum dots and the electron transport layer.

[0018] The details of the photodetector element of this embodiment will be described below with reference to Figure 1. Figure 1 is a schematic cross-sectional view of the photodetector element of this embodiment, and shows one embodiment of a photodiode type photodetector element. The arrows in the figure represent incident light to the photodetector element. The photodetector element 1 shown in Figure 1 includes a first electrode layer 11, a second electrode layer 12 facing the first electrode layer 11, a photoelectric conversion layer 13 provided between the first electrode layer 11 and the second electrode layer 12, an electron transport layer 21 provided between the first electrode layer 11 and the photoelectric conversion layer 13, and a hole transport layer 22 provided between the second electrode layer 12 and the photoelectric conversion layer 13. The first electrode layer 11 may be a cathode electrode layer, and the second electrode layer 12 may be an anode electrode layer.

[0019] At least one of the first electrode layer 11 and the second electrode layer 12 is a transparent electrode, and the photodetector element 1 shown in Figure 1 is used so that light is incident from the transparent electrode side. Although not shown, a transparent substrate may be placed on the surface on the light incident side. Examples of transparent substrates include glass substrates, resin substrates, ceramic substrates, etc.

[0020] <First electrode layer 11, second electrode layer 12> Of the first electrode layer 11 and the second electrode layer 12, the material of the electrode layer on the side where transparency is not required is not particularly specified, but it is preferably composed of a metallic material containing at least one metal atom selected from Au, Pt, Ir, Pd, Cu, Pb, Sn, Zn, Ti, W, Mo, Ta, Ge, Ni, Cr, and In. The film thickness is not particularly limited, but is preferably 0.01 μm or more and 100 μm or less, more preferably 0.01 μm or more and 1 μm or less, and particularly preferably 0.01 μm or more and 1 μm or less.

[0021] The electrode layer on the side requiring transparency is preferably a transparent electrode formed of a conductive material that is substantially transparent to the wavelength of light intended to be detected by the photodetector. In this specification, "substantially transparent" means that the light transmittance is 50% or more, preferably 60% or more, and particularly preferably 80% or more. Examples of transparent electrode materials include metals formed with a light-transmitting film thickness, as well as conductive metal oxides. Specific examples include tin oxide, zinc oxide, indium oxide, indium tungsten oxide, indium zinc oxide (IZO), indium tin oxide (ITO), and fluorine-doped tin oxide (FTO). The film thickness is not particularly limited, but is preferably 0.01 μm or more and 100 μm or less, more preferably 0.01 μm or more and 1 μm or less, and particularly preferably 0.01 μm or more and 1 μm or less.

[0022] In this invention, the film thickness of each layer can be measured by observing the cross-section of the photodetector using a scanning electron microscope (SEM) or the like.

[0023] <Electron Transport Layer 21> As shown in Figure 1, the electron transport layer 21 is provided between the first electrode layer 11 and the photoelectric conversion layer 13. The electron transport layer 21 is a layer that has the function of transporting electrons generated in the photoelectric conversion layer 13 to the electrode layer. The electron transport layer 21 is also called a hole blocking layer. The electron transport layer 21 contains a polymer (hereinafter sometimes simply referred to as "polymer") having a polymer chain containing structural units derived from an n-type organic semiconductor that can perform this function.

[0024] Polymers can be formed, for example, by polymerization of n-type organic semiconductors having polymerizable functional groups, polymerization of an n-type organic semiconductor having polymerizable functional groups, a crosslinking agent having polymerizable functional groups that can polymerize with the n-type organic semiconductor, and a resin having polymerizable functional groups that can polymerize with the crosslinking agent.

[0025] [n-type organic semiconductors] Examples of polymerizable functional groups in n-type organic semiconductors include functional groups containing active hydrogen groups (highly reactive hydrogen atoms bonded to oxygen, sulfur, nitrogen, etc.) such as hydroxyl groups, carboxyl groups, amino groups, and thiol groups, and functional groups polymerizable with them; unsaturated hydrocarbon groups (hydrocarbon groups containing double or triple bonds as carbon-carbon bonds in the carbon skeleton) such as acryloyloxy groups and methacryloyloxy groups, and functional groups polymerizable with them; cyclic ether groups such as epoxy groups, and functional groups polymerizable with them. Among these, hydroxyl groups, amino groups, and carboxyl groups are preferred.

[0026] Various forms of bonding are known to be formed by the polymerization of polymerizable functional groups. Examples of bonds formed by the polymerization of polymerizable functional groups in n-type organic semiconductors include urethane bonds (-NH-CO-O-) formed by the reaction of isocyanate groups and hydroxyl groups, urea bonds formed by the reaction of isocyanate groups and amino groups, amide bonds formed by the reaction of isocyanate groups and carboxyl groups, and >N-CH2 bonds formed by the reaction of N-methylol groups with hydroxyl or carboxyl groups. ２Examples include -O- bonds, bonds formed by addition polymerization of unsaturated hydrocarbon groups, and bonds formed by ring-opening polymerization or addition polymerization of cyclic ether groups. Among these, urethane bonds (-NH-CO-O-) and >N-CH ２ -O- bonds are preferred.

[0027] Examples of n-type organic semiconductors include perylenediimide derivatives, fullerene derivatives, naphthalenediimide derivatives, anthraquinone derivatives, fluorenone derivatives, phenanthrenequinone derivatives, benzimidazoperylene derivatives, benzimidazonaphthalene derivatives, diphenoquinone derivatives, and naphthoquinone derivatives. Among these, perylenediimide derivatives, naphthalenediimide derivatives, and fullerene derivatives are particularly preferred, with perylenediimide derivatives being even more preferred.

[0028] Perylenediimide derivatives can be synthesized using known synthesis methods described in, for example, the Journal of the American Chemical Society, Vol. 129, No. 49, 15259-78 (2007), the New Journal of Chemistry, Vol. 34, No. 11, 2337-2684 (2010), and can be synthesized by the reaction of perylenetetracarboxylic dianhydride, which can be purchased as a reagent from companies such as Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co., Ltd., and Johnson Matthey Japan, Inc., with a monoamine derivative.

[0029] Methods for introducing polymerizable functional groups into derivatives include, for example, directly introducing polymerizable functional groups into the synthesized skeleton, as well as introducing a structure having a polymerizable functional group or a functional group that can serve as a precursor to a polymerizable functional group (for example, a method using a palladium catalyst and a base in a cross-coupling reaction based on a perylenediimide derivative halide, FeCl ３ Methods for synthesizing perylenediimide derivatives include using a cross-coupling reaction with a catalyst and a base, and using perylenetetracarboxylic dianhydride derivatives or monoamine derivatives having polymerizable functional groups or functional groups that can act as precursors to polymerizable functional groups as raw materials.

[0030] Naphthalene diimide derivatives can be synthesized using known synthesis methods described, for example, U.S. Patent No. 4,442,193, U.S. Patent No. 4,992,349, U.S. Patent No. 5,468,583, Chemistry of Materials, Vol. 19, No. 11, 2703-2705 (2007), and can be synthesized by the reaction of naphthalenetetracarboxylic dianhydride, which can be purchased as a reagent from companies such as Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co., Ltd., and Johnson Matthey Japan, Inc., with a monoamine derivative.

[0031] Methods for introducing polymerizable functional groups into derivatives include, for example, directly introducing polymerizable functional groups into the synthesized skeleton, as well as introducing structures having polymerizable functional groups or functional groups that can serve as precursors to polymerizable functional groups (for example, a method of introducing functional group-containing aryl groups using a cross-coupling reaction with a palladium catalyst and a base, based on a halide of a naphthalene diimide derivative, FeCl ３ A method using a cross-coupling reaction with a catalyst and a base to introduce a functional group-containing alkyl group, followed by lithiation and then epoxy compound or CO ２ One method involves introducing hydroxyalkyl groups or carboxyl groups by applying a chemical agent, while another method uses naphthalenetetracarboxylic dianhydride derivatives or monoamine derivatives having polymerizable functional groups or functional groups that can serve as precursors to polymerizable functional groups as raw materials for synthesizing naphthalene dianhydride derivatives.

[0032] Fullerene derivatives can be purchased as reagents from companies such as Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co., Ltd., and Johnson Matthey Japan, Inc. They can also be synthesized using methods described in, for example, International Publication No. 2010 / 101241.

[0033] The following are specific examples of n-type organic semiconductors having polymerizable functional groups, but the invention is not limited to these examples.

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] [Crosslinking agents having polymerizable functional groups that can polymerize with n-type organic semiconductors] Crosslinking agents having polymerizable functional groups that can polymerize with n-type organic semiconductors are not particularly limited as long as they are compounds that can react with the polymerizable functional groups of n-type organic semiconductors, but compounds having multiple polymerizable functional groups are preferred, and low molecular weight compounds or oligomers are preferred. Examples of crosslinking agents having polymerizable functional groups that can polymerize with n-type organic semiconductors include compounds containing isocyanate groups or blocked isocyanate groups, compounds containing N-methylol groups or alkyl etherified N-methylol groups, compounds containing unsaturated hydrocarbon groups, and compounds containing epoxy groups.

[0048] Compounds containing isocyanate groups or blocked isocyanate groups are preferably compounds having multiple isocyanate groups or blocked isocyanate groups. Examples include triisocyanate benzene, triisocyanate methylbenzene, triphenylmethane triisocyanate, lysine triisocyanate, as well as isocyanurate modified, biuret modified, allophanate modified, and adduct modified with trimethylolpropane or pentaerythritol.

[0049] Examples of products available for purchase include Asahi Kasei's Duranate MFK-60B and SBA-70B, and Sumika Bayer Urethane's Desmodule BL3175 and BL3475.

[0050] Compounds containing an N-methylol group or an alkyl etherified N-methylol group are preferably compounds having multiple N-methylol groups or alkyl etherified N-methylol groups. Examples include methylolated melamine, methylolated guanamine, methylolated urea derivatives, methylolated ethyleneurea derivatives, methylolated glycoluryl, and these compounds and their derivatives in which the methylol moiety is alkyl etherified.

[0051] Examples of items available for purchase include Super Melami No. Examples include 90 (manufactured by Nippon Oil & Fats Co., Ltd.), Super Beccamine(R) TD-139-60, L-105-60, L127-60, L110-60, J-820-60, G-821-60 (manufactured by DIC Corporation), Yuban 2020 (Mitsui Chemicals), Sumitex Resin M-3 (Sumitomo Chemical Industries), Nikalac MW-30, MW-390, MX-750LM (manufactured by Nippon Carbide Co., Ltd.), Super Beccamine(R) L-148-55, 13-535, L-145-60, TD-126 (manufactured by DIC Corporation), Nikalac BL-60, BX-4000 (manufactured by Nippon Carbide Co., Ltd.), Nikalac MX-280, Nikalac MX-270, Nikalac MX-290 (manufactured by Nippon Carbide Co., Ltd.), and others.

[0052] Compounds containing unsaturated hydrocarbon groups are preferably those having multiple acrylic or methacrylic groups. Examples of commercially available products include Hitachi Chemical's Funcryl FA-129AS and FA-731A.

[0053] Compounds containing epoxy groups are preferably those having multiple epoxy groups. Examples of commercially available products include Epiclon 840 manufactured by DIC Corporation.

[0054] [Resin having polymerizable functional groups that can be polymerized with a crosslinking agent] In addition to the above, resins having polymerizable functional groups that can be polymerized with a crosslinking agent can be used for the electron transport layer of this embodiment. The resin having polymerizable functional groups that can be polymerized with a crosslinking agent may also be polymerized with an n-type organic semiconductor. Preferred polymerizable functional groups of the resin having polymerizable functional groups that can be polymerized with a crosslinking agent include hydroxyl groups, thiol groups, amino groups, carboxyl groups, methoxy groups, and the like. Examples of resins having polymerizable functional groups that can be polymerized with a crosslinking agent include polyether polyol resins, polyester polyol resins, polyacrylic polyol resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyamide resins, carboxyl group-containing resins, polyamine resins, polythiol resins, and the like.

[0055] Examples of the crosslinking agent that can be purchased and the resin having a polymerizable functional group include polyether polyol resins such as AQD-457 and AQD-473 manufactured by Nippon Polyurethane Industry Co., Ltd., and Sunnex GP-400 and GP-700 manufactured by Sanyo Chemical Industries, Ltd.; polyester polyol resins such as Phthal Kid W2343 manufactured by Hitachi Chemical Co., Ltd., Waterzol S-118, CD-520 manufactured by DIC Corporation, and Halidep WH-1188 manufactured by Harima Chemicals Group Inc.; polyacrylic polyol resins such as Vernoc WE-300 and WE-304 manufactured by DIC Corporation; polyvinyl alcohol resins such as Kuraray Poval PVA-203 manufactured by Kuraray Co., Ltd.; polyvinyl acetal resins such as Esrec BX-1, BM-1, KS-1, and KS-5 manufactured by Sekisui Chemical Co., Ltd.; polyamide resins such as Trezine FS-350 manufactured by Nagase ChemteX Corporation; carboxyl group-containing resins such as Aqualic manufactured by Nippon Catalyst Co., Ltd., Finelex SG2000 manufactured by Enshi Co., Ltd., and Alphon UC3920 and UF5080 manufactured by Toagosei Co., Ltd.; polyamine resins such as Lacquamide manufactured by DIC Corporation; and polythiol resins such as QE-340M manufactured by Toray Industries, Inc.

[0056] [Partial Structure] The polymer preferably has a partial structure represented by any of the following formulas (1) to (3).

[0057]

[0058] In formula (1), R １ , R ２ are each independently selected from a bonding site, a substituted or unsubstituted aryl group, and a substituted or unsubstituted alkyl group.

[0059] In formula (1), R ３ to R １０ are each independently selected from a bonding site, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted thiol group, a substituted or unsubstituted amino group, a substituted sulfonyl group, and a substituted sulfinyl group.

[0060]

[0061] In formula (2), R １１ , R １２ Each of these is independently selected from the bonding site, a substituted or unsubstituted aryl group, and a substituted or unsubstituted alkyl group.

[0062] In formula (2), R １３ ~R １６ Each of these is independently selected from a bonding site, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted thiol group, a substituted or unsubstituted amino group, a substituted sulfonyl group, or a substituted sulfinyl group.

[0063]

[0064] In formula (3), R ２１ , R ２２ This is a binding site.

[0065] R ２３ , R ２４ Each of these is independently selected from substituted or unsubstituted alkyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted aryl groups, and substituted or unsubstituted heteroaryl groups.

[0066] Only one hemispherical portion of the spherical fullerene structure is shown, and the other hemispherical portion is omitted. ２１ , R ２３ A first substituent including and R ２２ , R ２４ The position in which the second substituent, including the compound, attaches to the fullerene structure is arbitrary, and the second substituent may be omitted.

[0067] In formulas (1) to (3), the "binding site" refers to the site of binding to the polymerization chain. The substructures shown in formulas (1) to (3) correspond to structural units derived from n-type organic semiconductors. In other words, n-type organic semiconductors have polymerizable functional groups or groups having polymerizable functional groups at the sites corresponding to the binding sites.

[0068] The polymer content in the electron transport layer is preferably 50% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the electron transport layer. Furthermore, the n-type organic semiconductor content in the polymer is preferably 25% by mass or more, and more preferably 50% by mass or more, relative to the total mass of the polymer.

[0069] In addition to polymers, the electron transport layer may also contain other resins (resins without polymerizable functional groups), organic particles, inorganic particles, leveling agents, etc., to enhance film-forming properties and electrical characteristics. However, the content of these in the electron transport layer 21 is preferably 50% by mass or less, and more preferably 20% by mass or less, relative to the total mass of the electron transport layer 21.

[0070] The electron transport layer may be a single layer or a laminate of two or more layers. The thickness of the electron transport layer is preferably 10 nm or more and 1000 nm or less. The upper limit of the electron transport layer thickness is preferably 800 nm or less. The lower limit of the electron transport layer thickness is preferably 20 nm or more, and more preferably 50 nm or more. Furthermore, the thickness of the electron transport layer is preferably 0.05 times or more and 10 times or less the thickness of the photoelectric conversion layer 13, more preferably 0.1 times or more and 5 times or less, and even more preferably 0.2 times or more and 2 times or less.

[0071] The electron transport layer can be formed by a solution process. For example, an electron transport layer can be formed by forming a coating film of a solution containing an n-type organic semiconductor having polymerizable functional groups (a coating liquid for the electron transport layer) and then drying this coating film. After the coating film is formed, the compound having polymerizable functional groups polymerizes through a chemical reaction. Applying energy such as heat at this time is preferable because it accelerates the chemical reaction and promotes polymerization. Examples of solvents used in the coating liquid for the electron transport layer include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents.

[0072] <Photoelectric Conversion Layer 13> The photoelectric conversion layer 13 contains quantum dots. Preferably, the photoelectric conversion layer 13 contains an aggregate of semiconductor quantum dots containing metal atoms and ligands that coordinate to the semiconductor quantum dots. That is, preferably, the photoelectric conversion layer 13 is composed of a semiconductor film containing an aggregate of semiconductor quantum dots containing metal atoms and ligands that coordinate to the semiconductor quantum dots. Note that the aggregate of semiconductor quantum dots is a large number (for example, 1 μm) ２ This refers to a configuration in which semiconductor quantum dots (more than 100 per unit area) are arranged in close proximity to each other. Furthermore, in this specification, "semiconductor" refers to a semiconductor with a resistivity of 10 －２ Ωcm or more 10 ８ This refers to substances that are less than or equal to Ωcm.

[0073] Semiconductor quantum dots are semiconductor particles having metal atoms. In this invention, metal atoms also include semimetallic atoms, such as Si atoms. Examples of semiconductor quantum dot materials that constitute semiconductor quantum dots include nanoparticles (particles with a size of 0.5 nm or more and less than 100 nm) of general semiconductor crystals [a) group IV semiconductors, b) compound semiconductors of group IV-IV, group III-V, or group II-VI, c) compound semiconductors consisting of a combination of three or more elements from group II, group III, group IV, group V, and group VI].

[0074] The semiconductor quantum dot preferably contains at least one metal atom selected from Pb, In, Ge, Si, Cd, Zn, Hg, Al, Sn, and Ga atoms, and more preferably contains at least one metal atom selected from Pb, In, Ge, and Si atoms. It is even more preferable that it contains a Pb atom because the effects of the present invention are more easily obtained. Furthermore, lead-free In atoms are also preferred from a safety standpoint.

[0075] Specific examples of semiconductor quantum dot materials that constitute semiconductor quantum dots include PbS, PbSe, PbTe, InN, InAs, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, and Ag. ２ S, Ag ２ Se, Ag ２ Examples of semiconductor materials with relatively narrow band gaps include Te, SnS, SnSe, SnTe, Si, and InP. Among these, semiconductor quantum dots are preferably made of PbS or PbSe, and more preferably of PbS, because they efficiently convert infrared light (preferably light with wavelengths of 700 nm to 2500 nm) into electrons. In addition, InAs and Ag are safe semiconductor quantum dots that efficiently convert infrared light into electrons and do not contain lead. ２ S, Ag ２ It is preferable that it contains Se, and more preferably that it contains InAs.

[0076] In this embodiment of the photodetector element configuration, the detailed reason why semiconductor quantum dots containing PbS and InAs can be converted into electrons more efficiently is unknown. However, we believe that this is because the interaction between the n-type organic semiconductor contained in the electron transport layer adjacent to the photoelectric conversion layer and the quantum dots is strong, and electron transfer at the interface is smooth.

[0077] A semiconductor quantum dot may be a core-shell structure material in which a semiconductor quantum dot material serves as the core and the semiconductor quantum dot material is covered with a coating compound. Examples of coating compounds include ZnS, ZnSe, ZnTe, ZnCdS, CdS, and GaP.

[0078] The band gap Eg1 of the semiconductor quantum dot is preferably between 0.5 eV and 2.0 eV. If the band gap Eg1 of the semiconductor quantum dot is within the above range, it can be used as a photodetector capable of detecting light of various wavelengths depending on the application. For example, it can be used as a photodetector capable of detecting light in the infrared region. The upper limit of the band gap Eg1 of the semiconductor quantum dot is preferably 1.9 eV or less, more preferably 1.8 eV or less, and even more preferably 1.5 eV or less. The lower limit of the band gap Eg1 of the semiconductor quantum dot is preferably 0.5 eV or more.

[0079] The average particle size of the semiconductor quantum dots is preferably between 2 nm and 15 nm. The average particle size of the semiconductor quantum dots is the average value of the particle sizes of 10 arbitrarily selected semiconductor quantum dots. A transmission electron microscope can be used to measure the particle size of the semiconductor quantum dots.

[0080] Generally, semiconductor quantum dots contain particles of various sizes ranging from a few nanometers to tens of nanometers. When the average particle size of semiconductor quantum dots is reduced to a size smaller than the Bohr radius of the electrons inherent in the semiconductor quantum dot, a phenomenon occurs in which the band gap of the semiconductor quantum dot changes due to the quantum size effect. If the average particle size of semiconductor quantum dots is 15 nm or less, it is easier to control the band gap using the quantum size effect.

[0081] The photoelectric conversion layer 13 of the photodetector in this embodiment preferably contains ligands that coordinate to semiconductor quantum dots. Examples of ligands include ligands containing carboxyl groups, thiol groups, amino groups, etc., and polydentate ligands containing two or more coordinating parts. The ligand may be an aromatic compound. Specific examples of ligands include aromatic compounds having thiol groups such as 1,3-benzenedithiol. The photoelectric conversion layer 13 may contain only one type of ligand, or it may contain two or more types.

[0082] Examples of semiconductor quantum dots that are generally available for purchase include QDots™ manufactured by Quantum Solutions.

[0083] <Hole Transport Layer 22> In this embodiment, the photodetector element preferably has a hole transport layer 22 between the photoelectric conversion layer 13 and the second electrode layer 12. Examples of materials for the hole transport layer 22 include inorganic semiconductors such as molybdenum oxide and nickel oxide, and organic compounds such as PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid)), triarylamines, and poly-TPD. The hole transport layer 22 is preferably a layer containing a p-type organic semiconductor.

[0084] The thickness of the hole transport layer 22 is preferably 5 nm or more and 100 nm or less. The lower limit of the thickness of the hole transport layer 22 is preferably 10 nm or more. The upper limit of the thickness of the hole transport layer 22 is preferably 50 nm or less, and more preferably 30 nm or less.

[0085] ≪Image Sensor≫ The image sensor of this embodiment includes the photodetector element of this embodiment described above. If the photodetector element of this embodiment has excellent sensitivity to light in the infrared region, it can be used particularly preferably as an infrared image sensor. The configuration of the image sensor is not particularly limited as long as it includes the photodetector element of this embodiment and functions as an image sensor.

[0086] The image sensor may include an infrared transmission filter layer. The infrared transmission filter layer preferably has low transmittance of light in the visible wavelength range, more preferably an average transmittance of 10% or less, even more preferably 7.5% or less, and particularly preferably 5% or less for light in the wavelength range of 400 nm to 650 nm.

[0087] Examples of infrared transmission filter layers include those composed of a resin film containing a colorant. Examples of colorants include chromatic colorants such as red, green, blue, yellow, purple, and orange, as well as black colorants. Preferably, the colorant contained in the infrared transmission filter layer is formed by a combination of two or more chromatic colorants to form black, or contains a black colorant. When black is formed by a combination of two or more chromatic colorants, examples of combinations of chromatic colorants include the following embodiments (C1) to (C7): (C1) Embodiment containing a red colorant and a blue colorant. (C2) Embodiment containing a red colorant, a blue colorant, and a yellow colorant. (C3) Embodiment containing a red colorant, a blue colorant, a yellow colorant, and a purple colorant. (C4) Embodiment containing a red colorant, a blue colorant, a yellow colorant, a purple colorant, and a green colorant. (C5) Embodiment containing a red colorant, a blue colorant, a yellow colorant, and a green colorant. (C6) An embodiment containing a red colorant, a blue colorant, and a green colorant. (C7) An embodiment containing a yellow colorant and a purple colorant.

[0088] The above-mentioned chromatic colorants may be pigments or dyes. They may contain both pigments and dyes. The black colorant is preferably an organic black colorant. Examples of organic black colorants include bisbenzofuranone compounds, azomethine compounds, perylene compounds, and azo compounds.

[0089] The infrared transmission filter layer may further contain an infrared absorbent. By including an infrared absorbent in the infrared transmission filter layer, the wavelength of transmitted light can be shifted to a longer wavelength side. Examples of infrared absorbents include pyrrolopyrrole compounds, cyanine compounds, squarylium compounds, phthalocyanine compounds, naphthalocyanine compounds, quaterylene compounds, merocyanine compounds, crokonium compounds, oxonol compounds, iminium compounds, dithiol compounds, triarylmethane compounds, pyromethene compounds, azomethine compounds, anthraquinone compounds, dibenzofuranone compounds, dithiolene metal complexes, metal oxides, and metal borides.

[0090] The spectral characteristics of the infrared transmission filter layer can be appropriately selected depending on the application of the image sensor. For example, a filter layer that satisfies any of the spectral characteristics (1) to (5) below can be used.

[0091] (1) A filter layer in which the maximum value of the light transmittance in the thickness direction of the film in the wavelength range of 400 nm to 750 nm is 20% or less (preferably 15% or less, more preferably 10% or less), and the minimum value of the light transmittance in the thickness direction of the film in the wavelength range of 900 nm to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0092] (2) A filter layer in which the maximum value of the light transmittance in the thickness direction of the film in the wavelength range of 400 nm to 830 nm is 20% or less (preferably 15% or less, more preferably 10% or less), and the minimum value of the light transmittance in the thickness direction of the film in the wavelength range of 1000 nm to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0093] (3) A filter layer in which the maximum value of the light transmittance in the thickness direction of the film in the wavelength range of 400 nm to 950 nm is 20% or less (preferably 15% or less, more preferably 10% or less), and the minimum value of the light transmittance in the thickness direction of the film in the wavelength range of 1100 nm to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0094] (4) A filter layer in which the maximum value of the light transmittance in the thickness direction of the film in the wavelength range of 400 nm to 1100 nm is 20% or less (preferably 15% or less, more preferably 10% or less), and the minimum value in the wavelength range of 1400 nm to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0095] (5) A filter layer in which the maximum value of the light transmittance in the thickness direction of the film in the wavelength range of 400 nm to 1300 nm is 20% or less (preferably 15% or less, more preferably 10% or less), and the minimum value in the wavelength range of 1600 nm to 2000 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0096] Furthermore, the infrared transmission filter can use films described in Japanese Patent Publication No. 2013-077009, Japanese Patent Publication No. 2014-130173, Japanese Patent Publication No. 2014-130338, International Publication No. 2015 / 166779, International Publication No. 2016 / 178346, International Publication No. 2016 / 190162, International Publication No. 2018 / 016232, Japanese Patent Publication No. 2016-177079, Japanese Patent Publication No. 2014-130332, and International Publication No. 2016 / 027798. In addition, the infrared transmission filter may be a combination of two or more filters, or a dual bandpass filter that transmits two or more specific wavelength regions with a single filter may be used.

[0097] The image sensor may include an infrared shielding filter to improve various performance aspects such as noise reduction. Specific examples of infrared shielding filters include those described in International Publication No. 2016 / 186050, International Publication No. 2016 / 035695, Japanese Patent No. 6248945, International Publication No. 2019 / 021767, Japanese Patent Application Publication No. 2017-067963, and Japanese Patent No. 6506529.

[0098] The image sensor may include a dielectric multilayer film. Examples of dielectric multilayer films include those in which multiple layers of high-refractive-index dielectric thin films (high-refractive-index material layers) and low-refractive-index dielectric thin films (low-refractive-index material layers) are alternately stacked. While there are no particular limitations on the number of dielectric thin films stacked in the dielectric multilayer film, it is preferably 2 to 100 layers, more preferably 4 to 60 layers, and even more preferably 6 to 40 layers. As the material used to form the high-refractive-index material layer, a material with a refractive index of 1.7 to 2.5 is preferred. A specific example is Sb ２ O ３ Sb ２ S ３ , Bi ２ O ３ , CeO, CeF ３ , HfO ２ La ２ O ３ , Nd ２ O ３ , Pr ６ O １１ , Sc ２ O, SiO, Ta ２ O ５ , TiO ２ ,TlCl,Y ２ O ３ , ZnSe, ZnS, ZrO ２ Examples include the following. Materials with a refractive index of 1.2 or higher and 1.6 or lower are preferred for forming the low refractive index layer. Specific examples include Al ２ O ３ BiF ３ CaF ２ LaF ３ , PbCl ２ PbF ２ LiF, MgF ２ MgO, NdF ３ SiO ２ Si ２ O ３ NaF, ThO ２ , ThF ４ Na ３ AlF ６These are some examples. There are no particular restrictions on the method for forming the dielectric multilayer film, but examples include ion plating, vacuum deposition methods such as ion beam deposition, physical vapor deposition (PVD) methods such as sputtering, and chemical vapor deposition (CVD) methods. The thickness of each layer of the high refractive index material layer and the low refractive index material layer is preferably 0.1λ or more and 0.5λ or less when the wavelength of light to be blocked is λ (nm). Specific examples of dielectric multilayer films include, for example, the dielectric multilayer films described in Japanese Patent Application Publication No. 2014-130344 and Japanese Patent Application Publication No. 2018-010296.

[0099] The dielectric multilayer film preferably has a transmission wavelength band in the infrared region (preferably a wavelength region exceeding 700 nm, more preferably a wavelength region exceeding 800 nm, and even more preferably a wavelength region exceeding 900 nm). The maximum transmittance in the transmission wavelength band is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. The maximum transmittance in the light-shielding wavelength band is preferably 20% or less, and more preferably 10% or less. The average transmittance in the transmission wavelength band is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. The wavelength range of the transmission wavelength band is centered on the wavelength that shows the maximum transmittance, λ. ｔ１ In that case, the central wavelength λ ｔ１ Preferably, the center wavelength is ±100 nm, and the center wavelength is λ ｔ１ It is more preferable that the central wavelength is ±75 nm. ｔ１ A more preferable value is ±50 nm.

[0100] The dielectric multilayer film may have only one transmission wavelength band (preferably a transmission wavelength band with a maximum transmittance of 90% or more), or it may have multiple transmission wavelength bands.

[0101] The image sensor may include a color separation filter layer. An example of a color separation filter layer is a filter layer containing colored pixels. Examples of colored pixels include red pixels, green pixels, blue pixels, yellow pixels, cyan pixels, and magenta pixels. The color separation filter layer may contain two or more colored pixels, or only one color. This can be appropriately selected depending on the application and purpose. For example, a filter described in International Publication No. 2019 / 039172 can be used as the color separation filter layer.

[0102] Furthermore, if the color separation filter layer includes two or more colored pixels, the colored pixels of each color may be adjacent to each other, and partitions may be provided between each colored pixel. There are no particular limitations on the material of the partitions. Examples include organic materials such as siloxane resin and fluororesin, and inorganic particles such as silica particles. The partitions may also be made of metals such as tungsten and aluminum.

[0103] When an image sensor includes an infrared transmission filter layer and a color separation filter layer, it is preferable that the color separation filter layer is located on a separate optical path from the infrared transmission filter layer. It is also preferable that the infrared transmission filter layer and the color separation filter layer are arranged in two dimensions. Two-dimensional arrangement of the infrared transmission filter layer and the color separation filter layer means that at least a portion of both lies on the same plane.

[0104] The image sensor may include intermediate layers such as a planarization layer, a base layer, and an adhesion layer, an anti-reflective coating, and a lens. As the anti-reflective coating, for example, a film made from the composition described in International Publication No. 2019 / 017280 can be used. As the lens, for example, a structure described in International Publication No. 2018 / 092600 can be used.

[0105] If the photodetector element of this embodiment has excellent sensitivity to light in the infrared wavelength range, the image sensor of this embodiment can be preferably used as an infrared image sensor. Furthermore, the image sensor of this embodiment can be preferably used to sense light with wavelengths of 900 nm to 2000 nm, and more preferably to sense light with wavelengths of 900 nm to 1600 nm.

[0106] ≪Imaging Device≫ The photodetector according to one embodiment of the present invention may be used in an imaging device. The imaging device has an optical system having a plurality of lenses and an image sensor that receives light transmitted through the optical system, and the image sensor has a photodetector. Specifically, the imaging device may be a digital still camera or a digital video camera.

[0107] Figure 2 shows an example of an imaging system using a photodetector according to one embodiment of the present invention. As shown in Figure 2, the imaging system 200 includes an image sensor 201, an imaging optical system 202, a CPU 210, a lens control unit 212, an image sensor control unit 214, an image processing unit 216, an aperture shutter control unit 218, a display unit 220, an operation switch 222, and a recording medium 224.

[0108] The imaging optical system 202 is an optical system for forming an optical image of a subject, and includes a lens group, an aperture 204, etc. The aperture 204 has the function of adjusting the amount of light during shooting by adjusting its aperture diameter, and also functions as a shutter for adjusting the exposure time when shooting still images. The lens group and the aperture 204 are held so as to be able to move back and forth along the optical axis, and their coordinated movement realizes a variable magnification function (zoom function) and a focus adjustment function. The imaging optical system 202 may be integrated into the imaging system, or it may be an imaging lens that can be attached to the imaging system.

[0109] An image sensor 201 is positioned in the image space of the imaging optical system 202 such that its imaging plane is located there. The image sensor 201 has a photodetector element according to one embodiment of the present invention and is composed of a CMOS sensor (pixel portion) and its peripheral circuit (peripheral circuit region). The image sensor 201 is configured as a two-dimensional single-chip color sensor by arranging pixels, each having a plurality of photoelectric conversion units, in a two-dimensional arrangement, and arranging color filters for these pixels. The image sensor 201 photoelectrically converts the subject image formed by the imaging optical system 202 and outputs it as an image signal and a focus detection signal.

[0110] The lens control unit 212 controls the forward and backward movement of the lens group of the imaging optical system 202 to perform magnification and focus adjustment, and is composed of circuits and processing devices configured to realize this function. The aperture shutter control unit 218 adjusts the amount of light to be photographed by changing the aperture diameter of the aperture 204 (making the aperture value variable), and is composed of circuits and processing devices configured to realize this function.

[0111] The CPU 210 is an in-camera control unit that manages various aspects of the camera body, and includes an arithmetic unit, ROM, RAM, A / D converter, D / A converter, communication interface circuit, etc. The CPU 210 controls the operation of each part of the camera according to a computer program stored in the ROM, etc., and executes a series of shooting operations such as autofocus (AF), imaging, image processing, and recording, including detection of the focus state of the imaging optical system 202 (focus detection). The CPU 210 also functions as a signal processing unit.

[0112] The image sensor control unit 214 controls the operation of the image sensor 201 and performs A / D conversion on the signal output from the image sensor 201 and transmits it to the CPU 210. It is composed of circuits and control devices configured to realize these functions. The A / D conversion function may be provided by the image sensor 201. The image processing unit 216 generates an image signal by performing image processing such as gamma conversion and color interpolation on the A / D converted signal. It is composed of circuits and control devices configured to realize this function. The display unit 220 is a display device such as a liquid crystal display device (LCD) and displays information related to the camera's shooting mode, a preview image before shooting, a confirmation image after shooting, the focus status when focus is detected, etc. The operation switches 222 consist of a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, etc. The recording medium 224 is for recording captured images, etc., and may be built into the imaging system or may be a removable one such as a memory card.

[0113] In this way, by configuring an imaging system 200 to which an image sensor 201 having a photodetector element according to one embodiment of the present invention is applied, a high-performance imaging system can be realized.

[0114] ≪Mobile Body≫ An imaging device according to one embodiment of the present invention may be used in a mobile body. The mobile body has a body on which the imaging device is installed and means for moving the body. Specific examples of mobile bodies include automobiles, aircraft, ships, and drones. By installing an imaging device on the mobile body, the surrounding situation can be imaged to support the operation of the mobile body. The body can be made of metal or carbon fiber. Polycarbonate or the like may be used as the carbon fiber. Examples of means for moving include tires, magnetic levitation, and a mechanism for vaporizing and injecting fuel.

[0115] Figures 3A and 3B show the configuration of the imaging system and mobile body according to this embodiment. Figure 3A shows an example of an imaging system 300 related to an in-vehicle camera. The imaging system 300 has an imaging device 310. The imaging device 310 is an imaging device described in one embodiment of the present invention. The imaging system 300 has an image processing unit 312, which is an image processing device that performs image processing on a plurality of image data acquired by the imaging device 310, and a parallax acquisition unit 314, which is an image processing device that calculates parallax (phase difference of parallax images) from a plurality of image data acquired by the imaging device 310. The imaging system 300 also has a distance acquisition unit 316, which is an image processing device that calculates the distance to an object based on the calculated parallax, and a collision determination unit 318, which is an image processing device that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax acquisition unit 314 and the distance acquisition unit 316 are examples of information acquisition means that acquire information such as distance information to an object. That is, distance information is information such as parallax, defocus amount, distance to an object. The collision determination unit 318 may use any of this distance information to determine the possibility of a collision. The various processing units described above may be implemented by specially designed hardware, or by general-purpose hardware that performs calculations based on software modules. Furthermore, the processing units may be implemented by FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc., or by a combination thereof.

[0116] The imaging system 300 is connected to a vehicle information acquisition device 320 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The imaging system 300 is also connected to a control ECU 330, which is a control device that outputs a control signal to generate braking force on the vehicle based on the judgment result of the collision judgment unit 318. In other words, the control ECU 330 is an example of a mobile body control means that controls a moving object based on distance information. The imaging system 300 is also connected to a warning device 340 that issues a warning to the driver based on the judgment result of the collision judgment unit 318. For example, if the collision judgment unit 318 determines that there is a high probability of collision, the control ECU 330 performs vehicle control to avoid a collision or mitigate damage by applying the brakes, releasing the accelerator, or suppressing engine output. The warning device 340 warns the user by sounding a warning, displaying warning information on a screen such as a car navigation system, or vibrating the seat belt or steering wheel.

[0117] In this embodiment, the imaging system 300 captures images of the area around the vehicle, for example, in front of or behind it. Figure 3B shows the imaging system 300 when capturing images of the area in front of the vehicle (imaging range 350). The vehicle information acquisition device 320 sends an instruction to the imaging system 300 to operate and perform imaging. By using the imaging device according to one embodiment of the present invention as the imaging device 310, the imaging system 300 of this embodiment can further improve the accuracy of distance measurement.

[0118] The above explanation described an example of control to prevent collisions with other vehicles, but it can also be applied to control systems that automatically follow other vehicles, or control systems that automatically stay within their lanes. Furthermore, the imaging system can be applied not only to vehicles such as automobiles, but also to mobile objects (transportation equipment) such as ships, aircraft, or industrial robots. The moving devices in mobile objects (transportation equipment) include various means of movement such as engines, motors, wheels, and propellers. In addition, it can be applied not only to mobile objects, but also to a wide range of devices that utilize object recognition, such as intelligent transportation systems (ITS).

[0119] The present invention will be further described in detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. Note that "parts" means "parts by mass".

[0120] <Preparation of Exemplary Compound E101> To 100 parts of dimethylacetamide, 1.96 parts of 1,6,7,12-tetrachloroperylene 3,4,9,10-tetracarboxylic dianhydride (manufactured by Sigma-Aldrich Japan LLC) and 1.93 parts of L-tyrosine tert-butyl ester (manufactured by Tokyo Chemical Industry Co., Ltd.) were added under a nitrogen atmosphere. The mixture was stirred at room temperature for 1 hour to prepare a suspension, refluxed for 8 hours, the precipitate was filtered off, and recrystallized with ethyl acetate to obtain 2.50 parts of Exemplary Compound E101.

[0121] <Manufacturing of Electron Transport Layer Coating Solution> The following are the crosslinking agent having a functional group polymerizable with n-type organic semiconductors and the resin having a polymerizable functional group polymerizable with the crosslinking agent used in the manufacturing of the electron transport layer coating solution: (A) Crosslinking agent having a functional group polymerizable with n-type organic semiconductors

[0122]

[0123] (B) Resins having polymerizable functional groups that can be polymerized with crosslinking agents

[0124]

[0125] [Electron transport layer coating solution 101] 6.00 parts of exemplary compound E101 as an n-type organic semiconductor having polymerizable functional groups, 8.20 parts of A-1 as a crosslinking agent, 0.10 parts of B-1 and 0.10 parts of B-2 as resins were dissolved in a mixed solvent of 670 parts THF / 330 parts orthoxylene. Then, the mixture was pressure filtered using a Teflon® filter (product name: PF020) manufactured by ADVANTEC to produce electron transport layer coating solution 101.

[0126] Table 16 shows the partial structure of the polymer when this electron transport layer coating solution is formed ("bonding sites" are the bonding sites between the n-type organic semiconductor and the crosslinking agent), and the bonding groups in the polymer (groups that bond the n-type organic semiconductor and the crosslinking agent) are urethane bonds.

[0127] [Electron transport layer coating solutions 102-112, 201-212, 301-304, 401-408] The coating solutions were manufactured in the same manner as electron transport layer coating solution 101, except that the n-type organic semiconductor, crosslinking agent, and resin were changed as shown in Tables 16 to 19. The partial structures in the polymer when this electron transport layer coating solution was formed are as shown in Tables 16 to 18, and the bonding groups in the polymer are urethane bonds or >N-CH ２ The presence or absence of -O- bonds is shown in Tables 16 to 19.

[0128]

[0129]

[0130]

[0131]

[0132] <Example 1> [Manufacturing of photodetector element] The glass substrate with an ITO film was cleaned, and the ITO film was used as the first electrode layer 11.

[0133] The electron transport layer coating solution 101 was spin-coated onto the ITO film at 2000 rpm. Then, the film was heated at 180°C for 30 minutes to form an electron transport layer 21 with a thickness of approximately 20 nm.

[0134] A PbS quantum dot dispersion with oleic acid coordinated to it (product name: QDot PbS Quantum Dots, oleic acid capped 1500-abs, manufactured by Quantum Solutions) was concentrated and then subjected to pressure filtration using a Teflon® filter manufactured by ADVANTEC (product name: PF020).

[0135] The obtained quantum dot dispersion was dropped onto the electron transport layer 21 and then spin-coated at 2500 rpm to obtain a quantum dot aggregate film (Step 1).

[0136] Next, a solution of 1,3-benzenedithiol propylene glycol 1-monomethyl ether 2-acetate (PGMEA) (concentration 3 mg / mL) was added dropwise as a ligand solution onto the quantum dot assembly membrane, and then allowed to stand for 30 seconds to exchange the ligands. After that, PEGMEA was added dropwise as a rinse solution onto the quantum dot assembly membrane while spinning at 500 rpm for 60 seconds to rinse it. Furthermore, it was spin-dried at 2500 rpm for 60 seconds. Next, PbI ２ After adding a dropwise N,N-dimethylformamide solution (concentration 9 mg / mL), the mixture was allowed to stand for 3 minutes. Then, PEGMEA was added dropwise as a rinse solution to the quantum dot aggregate membrane while spinning at 500 rpm for 60 seconds to rinse it. Furthermore, it was spin-dried at 2500 rpm for 60 seconds (step 2).

[0137] The process of combining steps 1 and 2 was repeated for six cycles to form a photoelectric conversion layer 13 with a thickness of 200 nm, in which 1,3-benzenedithiol was coordinated as a ligand to the PbS quantum dots.

[0138] Next, a hole transport layer 22 with a thickness of approximately 10 nm was formed on the photoelectric conversion layer 13 by spin-coating a toluene solution of poly-TPD (Mn20000) (concentration 10 mg / mL) at 2000 rpm for 60 seconds.

[0139] Next, a 15 nm thick layer of MoO is deposited onto the hole transport layer 22 using a vacuum deposition method via a metal mask. ３ After forming the film, a 100 nm thick Au film (second electrode layer 12) was formed to manufacture a photodiode-type photodetector element.

[0140] [Analysis] The materials used to create the element, as well as the materials and film thickness within the created element, were confirmed using the following methods.

[0141] (1) Mass spectrometry was performed using a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOF MS: ultraflex, manufactured by Bruker Daltonics, Inc.). The conditions were: acceleration voltage: 20 kV, mode: Reflector, molecular weight standard: fullerene C60, and the molecular weight was confirmed by the obtained peak top value. The material in the fabricated device can be confirmed by removing the layer above the layer being used with an organic solvent such as chloroform, and then taking a sample of the electron transport layer.

[0142] It was confirmed that the coating solution contains compounds with the same molecular weight as the n-type organic semiconductor having polymerizable functional groups as shown in its composition.

[0143] (2) The thickness element of the electron transport layer 21 was cut and fixed to an inclined sample stage, and the thickness of the electron transport layer 21 was confirmed using a cross-sectional SEM (equipment: Carl Zeiss K.K., SmartSEM).

[0144] (3) Elution Test An aluminum sheet was used instead of an ITO-coated glass substrate to form the electron transport layer, and the sheet was weighed after film formation. The sheet was immersed in THF for 10 minutes, dried at 100°C for 10 minutes, and then weighed. After that, the film was completely removed by rubbing with Silbon paper soaked in dimethylacetamide, and then weighed again. The elution rate was calculated using the following formula. The elution rate indicates the proportion of substances other than polymers in the electron transport layer. ((Mass before immersion) - (Mass after immersion)) / ((Mass before immersion) - (Mass after rubbing)) × 100 = Elution rate [%]

[0145] [Evaluation] The manufactured devices were evaluated for dark current and external quantum efficiency (EQE) using a semiconductor parameter analyzer (4156B, manufactured by Agilent).

[0146] First, the current-voltage characteristics (I-V characteristics) were measured while sweeping the voltage from 0V to -2V without light irradiation, and the dark current was evaluated. Here, the current value at -1V was defined as the dark current value. Next, the I-V characteristics were measured while sweeping the voltage from 0V to -2V with 1500nm monochrome light irradiation. The photocurrent value was obtained by subtracting the dark current value from the current value at -0.5V, and the external quantum efficiency (EQE) was calculated from this value.

[0147] Next, the same measurement was performed after irradiating the sample with 1500 nm monochromatic light for 24 hours under a -1 V applied voltage, and the external quantum efficiency (EQE) was calculated.

[0148] Table 20 shows the decrease in external quantum efficiency ΔEQE (percent points).

[0149] <Examples 2 to 36> Except for forming the electron transport layer 21 using the electron transport layer coating solution shown in Tables 20 to 23, the device was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 20 to 23. In addition, mass spectrometry confirmed that the coating solution contained compounds with the same molecular weight as the n-type organic semiconductor having polymerizable functional groups shown in its composition.

[0150]

[0151]

[0152]

[0153]

[0154] <Example 37> [Manufacturing of a photodetector element] A photodetector element was manufactured in the same manner as in Example 1, except that the quantum dot dispersion was changed to an InAs quantum dot dispersion with fatty acids coordinated (product name: QDot InAs Quantum Dots, fatty acid capped 1400-abs, manufactured by Quantum Solutions) to form the photoelectric conversion layer 13.

[0155] [Evaluation] The evaluation was performed in the same manner as in Example 1, except that the monochrome light was changed to 1400 nm monochrome light. The results are shown in Table 24. In addition, mass spectrometry confirmed that the coating solution contained compounds with the same molecular weight as the n-type organic semiconductor having polymerizable functional groups shown in the composition.

[0156] <Example 38> [Production of electron transport layer coating solution 101a] The coating solution was produced in the same manner as the electron transport layer coating solution 101, except that the amount of n-type organic semiconductor was changed to 2.8 parts.

[0157] [Manufacturing of Photodetector] The device was manufactured and evaluated in the same manner as in Example 1, except that the electron transport layer 21 was formed using the electron transport layer coating solution 101a. The results are shown in Table 24. Mass spectrometry confirmed that the coating solution contained compounds with the same molecular weight as the n-type organic semiconductor having polymerizable functional groups shown in its composition.

[0158] <Example 39> [Production of electron transport layer coating liquid 101b] The coating liquid was produced in the same manner as the electron transport layer coating liquid 101, except that 4.0 parts of polystyrene resin (manufactured by Sigma-Aldrich Japan LLC) were added.

[0159] [Manufacturing of Photodetector] The device was manufactured and evaluated in the same manner as in Example 1, except that the electron transport layer 21 was formed using the electron transport layer coating solution 101b. The results are shown in Table 24. Mass spectrometry confirmed that the coating solution contained compounds with the same molecular weight as the n-type organic semiconductor having polymerizable functional groups shown in its composition.

[0160]

[0161] <Comparative Example 1> An electron transport layer 21 with a thickness of approximately 20 nm was fabricated and evaluated in the same manner as in Example 1, except that a ZnO dispersion (product name: QDot PbS ETL-ZnO, manufactured by Quantum Solutions) as a coating liquid for the electron transport layer was spin-coated at 2000 rpm and heated at 150°C for 30 minutes. The results are shown in Table 25.

[0162] <Comparative Example 2> The device was manufactured and evaluated in the same manner as in Example 1, except that a solution of 1 g of zinc acetate dihydrate and 284 μl of ethanolamine dissolved in 10 ml of methoxyethanol was spin-coated at 3000 rpm and heated at 200°C for 30 minutes to form a zinc oxide film (electron transport layer 21) with a thickness of approximately 50 nm. The results are shown in Table 25.

[0163] <Comparative Example 3> An element was manufactured and evaluated in the same manner as in Example 1, except that a titanium oxide film was deposited by 20 nm sputtering to form the electron transport layer 21, as described in the example of Patent Document 2. The results are shown in Table 25.

[0164] <Comparative Example 4> [6,6]-phenyl C as a coating liquid for electron transport layers ６１ The device was manufactured and evaluated in the same manner as in Example 1, except that an electron transport layer 21 with a thickness of approximately 20 nm was formed by spin-coating a toluene solution (concentration 20 mg / mL) of methyl butanoate (manufactured by Sigma-Aldrich Japan) at 2000 rpm for 60 seconds. The results are shown in Table 25.

[0165] <Comparative Example 5> [Manufacturing of electron transport layer coating liquid 101c] The coating liquid was manufactured in the same manner as electron transport layer coating liquid 101, except that a crosslinking agent was not used.

[0166] [Manufacturing of Photodetector] The device was manufactured and evaluated in the same manner as in Example 1, except that the electron transport layer 21 was formed using the electron transport layer coating solution 101c. The results are shown in Table 25.

[0167]

[0168] As shown in Tables 20 to 25, it was confirmed that the photodetector elements of the examples had low dark current and high external quantum efficiency (EQE).

[0169] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0170] This application claims priority based on Japanese Patent Application No. 2024-197615, filed on November 12, 2024, and all of its contents are incorporated herein by reference.

[0171] 1. Photodetector element 11. First electrode layer 12. Second electrode layer 13. Photoelectric conversion layer 21. Electron transport layer 22. Hole transport layer

Claims

1. A photodetector comprising: a first electrode layer; a second electrode layer; a photoelectric conversion layer located between the first electrode layer and the second electrode layer; and an electron transport layer located between the first electrode layer and the photoelectric conversion layer, wherein the photoelectric conversion layer contains quantum dots, and the electron transport layer contains a polymer having a polymer chain containing structural units derived from an n-type organic semiconductor.

2. The photodetector element according to claim 1, characterized in that the n-type organic semiconductor is one of a perylenediimide derivative, a naphthalenediimide derivative, or a fullerene derivative.

3. The n-type organic semiconductor is a urethane bond (-NH-CO-O-) or >N-CH ２ The photodetector element according to claim 1 or 2, characterized in that it is bonded to the polymerization chain via an -O- bond.

4. The polymerizable compound is characterized in that the polymer has a partial structure represented by any one of the following formulas (1) to (3). The photodetector according to claim 1 or 2. In formula (1), R １ , R ２ are each independently selected from a bonding site, a substituted or unsubstituted aryl group, and a substituted or unsubstituted alkyl group. R ３ to R １０ are each independently selected from a bonding site, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted thiol group, a substituted or unsubstituted amino group, a substituted sulfonyl group, and a substituted sulfinyl group. In formula (2), R １１ , R １２ are each independently selected from a bonding site, a substituted or unsubstituted aryl group, and a substituted or unsubstituted alkyl group. R １３ to R １６ are each independently selected from a bonding site, a hydrogen atom, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, a hydroxyl group, a thiol group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted thiol group, a substituted or unsubstituted amino group, a substituted sulfonyl group, and a substituted sulfinyl group. In formula (3), R ２１ , R ２２ are bonding sites. R ２３ , R ２４ are each independently selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. Only one hemispherical portion of the spherical fullerene structure is shown, and the other hemispherical portion is omitted. The first substituent including R ２１ , R ２３ and the second substituent including R ２２ , R ２４ The position in which the second substituent, including the compound, attaches to the fullerene structure is arbitrary, and the second substituent may be omitted.

5. The photodetector element according to claim 1 or 2, characterized in that the polymer is obtained by polymerizing or crosslinking an n-type organic semiconductor having a functional group selected from a hydroxyl group, an amino group, and a carboxyl group.

6. The photodetector element according to claim 1 or 2, characterized in that the polymer is a polymer of an n-type organic semiconductor having polymerizable functional groups, a crosslinking agent having polymerizable functional groups that can polymerize with the n-type organic semiconductor, and a resin having polymerizable functional groups that can polymerize with the crosslinking agent.

7. The photodetector element according to claim 1 or 2, characterized in that the content of the polymer in the electron transport layer is 50% by mass or more with respect to the total mass of the electron transport layer.

8. The photodetector according to claim 1 or 2, characterized in that the quantum dot is a PbS quantum dot or an InAs quantum dot.

9. The photodetector according to claim 1 or 2, characterized in that the quantum dot has a ligand.

10. The photodetector according to claim 9, characterized in that the ligand is an aromatic compound having a thiol group.

11. The photodetector according to claim 1 or 2, characterized in that a hole transport layer containing a p-type organic semiconductor is provided between the photoelectric conversion layer and the second electrode layer.

12. A method for manufacturing a photodetector according to claim 1 or 2, characterized by comprising the steps of forming a coating film of a solution containing an n-type organic semiconductor having polymerizable functional groups, and drying the coating film to form the electron transport layer.

13. An image sensor characterized by including the photodetector element described in claim 1 or 2.

14. An imaging device comprising an optical system having a plurality of lenses and an image sensor that receives light transmitted through the optical system, wherein the image sensor has the photodetector element described in claim 1 or 2.

15. A mobile body comprising a body equipped with an imaging device and a means for moving the body, wherein the imaging device is the imaging device described in claim 14.

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