Photodetection element and image sensor

Abstract

Provided are: a photodetection element comprising a first electrode (11), a second electrode (12), a photoelectric conversion layer (13) that includes an aggregate of quantum dots provided between the first electrode (11) and the second electrode (12), a first charge transport layer (21) that is provided between the photoelectric conversion layer (13) and the first electrode (11), and a second charge transport layer (22) that is provided between the photoelectric conversion layer (13) and the second electrode (12), wherein the first electrode (11) is provided on the light incidence side relative to the second electrode (12), the relationship in expression (1) is satisfied by the wavelength λ of target light detected by the photodetection element and the optical path length L1 of the light having the wavelength λ, said optical path length extending from the photoelectric conversion layer-side surface (12a) of the second electrode (12) to the light incidence-side surface (11a) of the photodetection element; and an image sensor including said photodetection element. (1): 0.59 < L1 / λ < 0.84

Description

Photodetector and image sensor

[0001] The present invention relates to a photodetector and an image sensor having a photoelectric conversion layer containing quantum dots.

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

[0003] Conventionally, silicon photodiodes, which use silicon wafers as the material for the photoelectric conversion layer, have been used as photodetectors in image sensors and other applications. However, silicon photodiodes have low sensitivity in the infrared region with wavelengths above 900 nm.

[0004] Furthermore, InGaAs-based semiconductor materials, known as near-infrared light receiving elements, require extremely costly processes such as epitaxial growth and substrate bonding to achieve high quantum efficiency, which has hindered their widespread adoption.

[0005] Furthermore, research on quantum dots has been progressing in recent years. For example, Patent Document 1 describes an invention relating to a photodetector that uses semiconductor inorganic nanoparticles such as PbS quantum dots as a photoactive layer.

[0006] Special table 2016-532301 publication

[0007] In recent years, with the increasing demand for improved performance in image sensors and other devices, there has been a growing need for further improvements in the various characteristics required of the photodetectors used in them. For example, one characteristic required of photodetectors is a high light absorption rate for the wavelength of light to be detected. By increasing the light absorption rate of a photodetector, the accuracy of light detection by the photodetector can be improved.

[0008] However, photodetectors with photoelectric conversion layers using quantum dots still had room for improvement in terms of light absorption rate.

[0009] Therefore, the object of the present invention is to provide a photodetector and an image sensor having a high light absorption rate.

[0010] According to studies by the present inventor, it has been found that the above object can be achieved by adopting the following configuration, and the present invention has been completed. Accordingly, the present invention provides the following.

[0011] <1> A photodetection element comprising: a first electrode; a second electrode; a photoelectric conversion layer including an aggregate of quantum dots provided between the first electrode and the second electrode; a first charge transport layer provided between the photoelectric conversion layer and the first electrode; and a second charge transport layer provided between the photoelectric conversion layer and the second electrode, wherein the first electrode is provided closer to a light incident side than the second electrode, and wherein the wavelength λ of target light to be detected by the photodetection element, and the optical path length L of the light of the wavelength λ from a surface of the second electrode on the photoelectric conversion layer side to a surface of the photodetection element on the light incident side １ satisfy the relationship of formula (1). 0.59 < L １ / λ < 0.84 (1) In formula (1), λ is the wavelength of the target light to be detected by the photodetection element, and L １ is the optical path length of the light of the wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the photodetection element on the light incident side. <2> The photodetection element according to <1>, wherein the first electrode is disposed on an outermost layer of the photodetection element on the light incident side, and the optical path length L １ is the optical path length of the light of the wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to a surface of the first electrode on the light incident side. <3> The photodetection element according to <1>, further comprising an optical path length adjustment layer on the light incident side of the first electrode, wherein the optical path length adjustment layer is disposed on an outermost layer of the photodetection element on the light incident side, and the optical path length L １ is the optical path length of the light of the wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to a surface of the optical path length adjustment layer on the light incident side. <4> The optical path length adjustment layer comprises SiO ２ , SiON, TiO ２ , Ta ２ O ５ , ZrO ２ , HfO ２ , Y ２ O ３ , and Al ２ O ３A photodetector according to <3>, comprising at least one selected from the above. <5> The above photodetector is a photodetector according to any one of <1> to <4> that satisfies the relationship of formula (2); 0.10 <L ２ / λ < 0.50 ... (2) In equation (2), λ is the wavelength of the light to be detected by the photodetector, L ２ From the surface of the photoelectric conversion layer on the second electrode, L of the photoelectric conversion layer ３ L is the optical path length of light of the above wavelength λ up to 2 / 2. ３ This is the optical path length of the photoelectric conversion layer for light of the above wavelength λ. <6> The above photodetector is a photodetector described in any one of <1> to <5> that satisfies the relationship in equation (3). 0.05 <L ３ / λ ... (3) In equation (3), λ is the wavelength of the light to be detected by the photodetector, L ３ is the optical path length of the photoelectric conversion layer for light of the above wavelength λ. <7> The light to be detected by the above photodetector is light in the wavelength range of 700 to 2500 nm, as described in any one of <1> to <6>. <8> An image sensor including the photodetector described in any one of <1> to <7>.

[0012] According to the present invention, it is possible to provide a photodetector and an image sensor having a high light absorption rate.

[0013] This is a diagram showing a first embodiment of the photodetector. This is a diagram showing a second embodiment of the photodetector.

[0014] The present invention will be described in detail below. In this specification, "~" is used to mean that the numerical values ​​before and after it are included as the lower and upper limits. In the notation of groups (atomic groups) in this specification, notations that do not specify substitution or unsubstituted include both groups (atomic groups) with substituents and groups (atomic groups) without substituents. For example, "alkyl group" includes not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups).

[0015] <Photodetector> The photodetector of the present invention comprises: a first electrode; a second electrode; a photoelectric conversion layer including an aggregate of quantum dots between the first electrode and the second electrode; a first charge transport layer between the photoelectric conversion layer and the first electrode; and a second charge transport layer between the photoelectric conversion layer and the second electrode, wherein the first electrode is provided on the light incident side of the second electrode, and the wavelength λ of the light to be detected by the photodetector, and the optical path length L of the light with wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the photodetector on the light incident side. １ It is characterized by satisfying the relationship in equation (1).

[0016] 0.59 < L １ / λ < 0.84 ... (1) In equation (1), λ is the wavelength of the light to be detected by the photodetector, L １ This is the optical path length of the light of the above wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the photodetector on the light incident side.

[0017] The photodetector of the present invention has a high light absorption rate. More specifically, the photodetector of the present invention has a high light absorption rate for light of the above wavelength λ. The reason for this effect is presumed to be the following: namely, the above wavelength λ and the above optical path length L １ Because the relationship described in (1) above is satisfied, the phases of the light incident on the photodetector (incident light) and the reflected light from the surface of the second electrode can be aligned. As a result, the electric field in the photoelectric conversion layer is enhanced by the optical interference effect, and it is presumed that a high light absorption rate can be obtained for light of the above wavelength λ.

[0018] Here, the optical path length refers to the product of the physical thickness of the material through which light passes and its refractive index. To explain using a photoelectric conversion layer as an example, if the thickness of the photoelectric conversion layer is d ａ１ , wavelength λ of the photoelectric conversion layer ａ１ The refractive index for N ａ１ In this case, the wavelength λ transmitted through the photoelectric conversion layer ａ１ The optical path length of the light is N ａ１ ×d ａ１In cases where the photoelectric conversion layer is composed of two or more laminated films, or where an intermediate layer exists between the photoelectric conversion layer and the second electrode layer, the integrated value of the optical path lengths of each layer is the optical path length L. １ That is the case.

[0019] The photodetector of the present invention has a wavelength λ of light to be detected by the photodetector and the optical path length L. １ It is preferable that the relationship in equation (1-1) is satisfied, and it is more preferable that the relationship in equation (1-2) is satisfied. 0.63 < L １ / λ<0.84...(1-1) 0.70<L １ / λ < 0.81 ... (1-2)

[0020] The photodetector of the present invention preferably satisfies the relationship of formula (2), more preferably satisfies the relationship of formula (2-1), and even more preferably satisfies the relationship of formula (2-2). According to this embodiment, a higher light absorption rate can be obtained. 0.10 < L ２ / λ<0.50...(2) 0.13<L ２ / λ<0.45...(2-1) 0.17<L ２ / λ < 0.40 ... (2-2)

[0021] In equation (2), λ is the wavelength of the light to be detected by the photodetector, and L ２ From the surface of the second electrode on the photoelectric conversion layer side, L of the photoelectric conversion layer ３ L is the optical path length of light of the above wavelength λ up to 2 / 2. ３ This is the optical path length of the light with the above wavelength λ in the photoelectric conversion layer.

[0022] The photodetector of the present invention preferably satisfies the relationship of formula (3), more preferably satisfies the relationship of formula (3-1), and even more preferably satisfies the relationship of formula (3-2). According to this embodiment, a higher light absorption rate can be obtained. In the following formula, "L ３ The upper limit of the value of / λ is preferably less than 0.7. 0.05 < L ３ / λ...(3) 0.10<L ３ / λ...(3-1) 0.15<L ３ / λ...(3-2)

[0023] In equation (3), λ is the wavelength of the light to be detected by the photodetector, and L ３ This is the optical path length of the light with the above wavelength λ in the photoelectric conversion layer.

[0024] The light intended to be detected by the photodetector is preferably light with a wavelength in the infrared region. That is, the wavelength λ is preferably a wavelength in the infrared region. Furthermore, the light intended to be detected by the photodetector is preferably light with a wavelength in the range of 700 to 2500 nm. The lower limit of the wavelength of the above light is preferably 800 nm or more, and more preferably 900 nm or more. The upper limit of the wavelength of the above light is preferably 2000 nm or less, more preferably 1800 nm or less, and even more preferably 1600 nm or less. The light intended to be detected by the photodetector is preferably light with a wavelength in the range of 900 to 2000 nm, and more preferably light with a wavelength in the range of 900 to 1600 nm.

[0025] The light detection element of the present invention is preferably an infrared light detection element.

[0026] The photodetector of the present invention may selectively detect only light of the above wavelength λ, or it may simultaneously detect light of the above wavelength λ and light of a different wavelength. For example, if the above wavelength λ is light in the infrared region, it may simultaneously detect light of the above wavelength λ, which is light in the infrared region, and light of the visible region (preferably light in the range of wavelengths from 400 to less than 700 nm).

[0027] The photodetector element of the present invention can also be used in combination with a support such as a glass substrate. That is, the photodetector element of the present invention may be placed on the support, or the support may be placed on the photodetector element of the present invention. Note that a thick member such as a support (for example, a member with a thickness of 100 μm or more) is different from the member constituting the photodetector element of the present invention. Therefore, for example, even when a support such as a glass substrate is placed on the first electrode of a photodetector element having the first electrode on the outermost layer on the light incident side, the optical path length of light with wavelength λ from the surface on the photoelectric conversion layer side of the second electrode to the surface on the light incident side of the first electrode is the optical path length L.１ That is the case.

[0028] <<First Embodiment>> The details of the photodetector element of the present invention will be described below with reference to the drawings. Figure 1 shows a first embodiment of the photodetector element. The arrows in the figure represent incident light to the photodetector element. The photodetector element 1 shown in Figure 1 includes a second electrode 12, a first electrode 11 provided opposite to the second electrode 12, a photoelectric conversion layer 13 provided between the second electrode 12 and the first electrode 11, a first charge transport layer 21 provided between the first electrode 11 and the photoelectric conversion layer 13, and a second charge transport layer 22 provided between the second electrode 12 and the photoelectric conversion layer 13. In the photodetector element 1 shown in Figure 1, the first electrode 11 is located on the outermost surface of the photodetector element on the light incident side.

[0029] In the photodetector element 1 shown in Figure 1, the optical path length of the light of wavelength λ from the surface 12a of the second electrode layer 12 on the photoelectric conversion layer 13 side to the surface 11a of the first electrode 11 on the light incidence side is the optical path length L. １ This corresponds to the following. In the photodetector element 1 shown in Figure 1, the wavelength λ of the light to be detected by the photodetector element 1 and the optical path length L of the light of the above wavelength λ from the surface 12a on the photoelectric conversion layer 13 side of the second electrode layer 12 to the surface 11a on the light incident side of the first electrode 11 are... １ It is preferable that the above equation (1) satisfies the relationship, the above equation (1-1) satisfies the relationship, and it is more preferable that the above equation (1-2) satisfies the relationship.

[0030] The photodetector 1 shown in Figure 1 detects the wavelength λ of the light to be detected by the photodetector 1, and the L of the photoelectric conversion layer from the surface 12a of the second electrode 12 on the photoelectric conversion layer 13 side. ３ The optical path length L of light with the above wavelength λ up to / 2 ２ It is preferable that the relationship in formula (2) above is satisfied, more preferably that the relationship in formula (2-1) above is satisfied, and even more preferably that the relationship in formula (2-2) above is satisfied. ３ L is the optical path length of the light of the above wavelength λ in the photoelectric conversion layer 13. ３It is preferable that the above equation (3) satisfies the relationship, more preferably that the above equation (3-1) satisfies the relationship, and even more preferably that the above equation (3-2) satisfies the relationship.

[0031] (First Electrode) The first electrode 11 is preferably a transparent electrode formed of a conductive material that is substantially transparent to the wavelength of light 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 more preferably 80% or more. Examples of materials for the first electrode 11 include conductive metal oxides. Specific examples include tin oxide, zinc oxide, indium oxide, indium tungsten oxide, indium zinc oxide (IZO), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and the like.

[0032] The film thickness of the first electrode 11 is not particularly limited, but is preferably 0.01 to 50 μm, more preferably 0.01 to 10 μm, and even more preferably 0.01 to 1 μm. The film thickness of each layer can be measured by observing the cross-section of the photodetector element 1 using a scanning electron microscope (SEM) or the like.

[0033] (Second Electrode) The material for forming the second electrode 12 can be a metallic material containing at least one metal atom selected from Ag, Au, Pt, Ir, Pd, Cu, Pb, Sn, Zn, Ti, W, Mo, Ta, Ge, Ni, Al, Cr, and In, a conductive metal oxide as listed in the section on the first electrode 11, a carbon material, or a conductive polymer. The carbon material can be any conductive material, such as fullerene, carbon nanotube, graphite, or graphene.

[0034] The film thickness of the second electrode 12 is not particularly limited, but is preferably 0.01 to 50 μm, more preferably 0.01 to 10 μm, and even more preferably 0.01 to 1 μm.

[0035] (Photoelectric Conversion Layer) The photoelectric conversion layer 13 contains an aggregate of quantum dots. Note that the aggregate of quantum dots is a large number of dots (for example, 1 μm) ２ This refers to a configuration in which quantum dots (more than 100 per unit area) are arranged in close proximity to each other. The quantum dots are preferably semiconductor particles containing metal atoms. In this specification, metal atoms also include semimetallic atoms, such as Si atoms. Furthermore, in this specification, "semiconductor" refers to a semiconductor with a resistivity of 10⁻¹⁰ －２ Ωcm or more 10 ８ This refers to substances that are less than or equal to Ωcm.

[0036] Examples of materials that constitute 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].

[0037] The quantum dot preferably contains at least one element selected from the group consisting of Ga, Ge, P, As, Se, In, Sn, Sb, Te, Pb, Bi, Ag, Cu, and Hg, more preferably contains at least one element selected from the group consisting of Ga, P, As, Se, In, Sb, Te, and Bi, and even more preferably contains at least one element selected from the group consisting of P, As, Sb, and In.

[0038] The quantum dot is preferably a group III-V quantum dot or a group IV-VI quantum dot, and more preferably a group III-V quantum dot.

[0039] III-V quantum dots are quantum dots made of compound semiconductors containing Group III elements (Group 13 elements) and Group V elements (Group 15 elements). IV-VI quantum dots are quantum dots made of compound semiconductors containing Group IV elements (Group 14 elements) and Group VI elements (Group 16 elements).

[0040] Examples of Group III elements included in Group III-V quantum dots include boron (B), aluminum (Al), gallium (Ga), and indium (In), with the inclusion of In being preferable. Examples of Group V elements included in Group III-V quantum dots include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), with the inclusion of at least one element selected from As and Sb being preferable. Group III-V quantum dots may further contain elements other than Group III and Group V elements. Examples of other elements include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), and mercury (Hg).

[0041] Examples of Group IV elements included in Group IV-VI quantum dots include silicon (Si), germanium (Ge), tin (Sn), and lead (Pb), with Pb being preferred. Examples of Group VI elements included in Group IV-VI quantum dots include oxygen (O), sulfur (S), selenium (Se), and tellurium (Te), with at least one element selected from S and Se being preferred, and S being more preferred. Group IV-VI quantum dots may further contain elements other than Group IV and Group VI elements. Examples of other elements include Mg, Ca, Sr, Ba, Zn, Cd, and Hg.

[0042] Specific examples of quantum dots include PbS, PbSe, PbSeS, inN, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, InPAs, InAsSb, InPSb, HgTe, HgCdTe, and Ag. ２ S, Ag ２ Se, Ag ２ Te, SnS, SnSe, SnTe, Si, InP, AgBiS ２Examples include AgBiSTe, and it is preferable that it be at least one selected from PbS, InAs, InSb, InPAs, InAsSb, InPSb, PbS, and PbSe, and more preferably at least one selected from PbS, InAs, InSb, InPAs, and InAsSb.

[0043] The band gap of the quantum dot is preferably 0.5 to 2.0 eV. If the band gap of the quantum dot is within the above range, it can be used as a photodetector capable of detecting light with wavelengths in the infrared region. The upper limit of the band gap of the quantum dot is preferably 1.5 eV or less, more preferably 1.35 eV or less, even more preferably 1.1 eV or less, and particularly preferably 1.0 eV or less. The band gap of the quantum dot can be calculated from the energy at the maximum absorption wavelength of the absorption spectrum obtained by measuring light absorption in the visible to infrared region using an ultraviolet-visible-near-infrared spectrophotometer. In the case of a quantum dot that does not have a maximum absorption wavelength, it can be determined from a Tauc plot, as described in Japanese Patent Publication No. 5949567.

[0044] The quantum dots preferably have a maximum absorbance in the wavelength range of 900 to 1700 nm, and more preferably have a maximum absorbance in the wavelength range of 1000 to 1600 nm.

[0045] It is also preferable that the quantum dots have high absorption for light of any wavelength in the range of 900 to 1700 nm (preferably in the range of 1000 to 1600 nm). By using such quantum dots, it is possible to form a quantum dot film that has a higher external quantum efficiency for light of infrared wavelengths.

[0046] The average primary particle diameter of the quantum dots is preferably 2 nm to 15 nm. In this specification, the average primary particle diameter of the quantum dots is the average value (arithmetic mean) of the equivalent circle diameters of the primary particles of 500 randomly selected quantum dots. The equivalent circle diameter of the primary particle of a quantum dot is determined by measuring the area S of one particle in an electron microscope image taken with a transmission electron microscope, and calculating the diameter of the circle corresponding to this area S (equivalent circle diameter = 2(S / π)). ０．５ ) can be calculated.

[0047] The photoelectric conversion layer 13 preferably contains ligands that coordinate to the quantum dots. Examples of ligands include organic ligands and inorganic ligands.

[0048] The organic ligand may be a monodentate organic ligand having one coordinating moiety, or a polydentate organic ligand containing two or more coordinating moieties. Examples of coordinating moieties included in the organic ligand are thiol groups, amino groups, hydroxyl groups, carboxyl groups, sulfo groups, phospho groups, and phosphonic acid groups.

[0049] Examples of polydentate ligands include ligands represented by any of the formulas (A) to (C).

[0050] In formula (A), X Ａ１ and X Ａ２ Each of these independently represents a thiol group, amino group, hydroxyl group, carboxyl group, sulfo group, phospho group, or phosphonic acid group, L Ａ１ This represents a hydrocarbon group.

[0051] In formula (B), X Ｂ１ and X Ｂ２ Each of these independently represents a thiol group, amino group, hydroxyl group, carboxyl group, sulfo group, phospho group, or phosphonic acid group, X Ｂ３ represents S, O, or NH, and L Ｂ１ and L Ｂ２ Each of these independently represents a hydrocarbon group.

[0052] In formula (C), X Ｃ１ ~X Ｃ３each independently represent a thiol group, an amino group, a hydroxy group, a carboxy group, a sulfo group, a phospho group or a phosphonic acid group, and X Ｃ４ represents N, and L Ｃ１ to L Ｃ３ each independently represent a hydrocarbon group.

[0053] X Ａ１ , X Ａ２ , X Ｂ１ , X Ｂ２ , X Ｃ１ , X Ｃ２ and X Ｃ３ include, but are not limited to -NH ２ , and also include substituted amino groups and cyclic amino groups. Examples of the substituted amino group include a monoalkylamino group, a dialkylamino group, a monoarylamino group, a diarylamino group, and an alkylarylamino group. Among the amino groups represented by these groups, -NH ２ , a monoalkylamino group, and a dialkylamino group are preferred, and -NH ２ is more preferred.

[0054] In formula (A), at least one of X Ａ１ and X Ａ２ is preferably a thiol group. The other may be a thiol group or a group other than a thiol group. The group other than a thiol group is preferably a carboxy group, an amino group or a hydroxy group.

[0055] In formula (B), at least one of X Ｂ１ and X Ｂ２ is preferably a thiol group. The other may be a thiol group or a group other than a thiol group. The group other than a thiol group is preferably a carboxy group, an amino group or a hydroxy group.

[0056] In formula (C), at least one of X Ｃ１ to X Ｃ３ is preferably a thiol group. The other may be a thiol group or a group other than a thiol group. The group other than a thiol group is preferably a carboxy group, an amino group or a hydroxy group.

[0057] L Ａ１ , L Ｂ１ , L Ｂ２ , L Ｃ１ , L Ｃ２ and L Ｃ３ The hydrocarbon group represented is preferably an aliphatic hydrocarbon group or a group containing an aromatic ring, and more preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The number of carbon atoms in the hydrocarbon group is preferably 1 to 20. The upper limit of the number of carbon atoms is preferably 10 or less, more preferably 6 or less, and even more preferably 3 or less. Specific examples of hydrocarbon groups include alkylene groups, alkenylene groups, alkylene groups, and arylene groups.

[0058] Examples of the alkylene group include linear alkylene groups, branched alkylene groups and cyclic alkylene groups, and the alkylene group is preferably a linear alkylene group or a branched alkylene group, and more preferably a linear alkylene group. Examples of the alkenylene group include linear alkenylene groups, branched alkenylene groups and cyclic alkenylene groups, and the alkenylene group is preferably a linear alkenylene group or a branched alkenylene group, and more preferably a linear alkenylene group. Examples of the alkynylene group include linear alkynylene groups and branched alkynylene groups, and the alkynylene group is preferably a linear alkynylene group. The arylene group may be monocyclic or polycyclic. It is preferably a monocyclic arylene group. Specific examples of the arylene group include a phenylene group and a naphthylene group, and the arylene group is preferably a phenylene group. The alkylene group, alkenylene group, alkynylene group and arylene group may further have a substituent. The substituent is preferably a group having 1 to 10 atoms. Preferable specific examples of the group having 1 to 10 atoms include: alkyl groups having 1 to 3 carbon atoms [a methyl group, an ethyl group, a propyl group, and an isopropyl group]; alkenyl groups having 2 to 3 carbon atoms [an ethenyl group and a propenyl group]; alkynyl groups having 2 to 4 carbon atoms [an ethynyl group, a propynyl group, etc.]; a cyclopropyl group; alkoxy groups having 1 to 2 carbon atoms [a methoxy group and an ethoxy group]; acyl groups having 2 to 3 carbon atoms [an acetyl group and a propionyl group]; alkoxycarbonyl groups having 2 to 3 carbon atoms [a methoxycarbonyl group and an ethoxycarbonyl group]; an acyloxy group having 2 carbon atoms [an acetyloxy group]; an acylamino group having 2 carbon atoms [an acetylamino group]; hydroxyalkyl groups having 1 to 3 carbon atoms [a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group]; an aldehyde group, a hydroxy group, a carboxy group, a sulfo group, a phospho group, a carbamoyl group, a cyano group, an isocyanate group, a thiol group, a nitro group, a nitroxy group, an isothiocyanate group, a cyanate group, a thiocyanate group, an acetoxy group, an acetamido group, a formyl group, a formyloxy group, a formamido group, a sulfamino group, a sulfino group, a sulfamoyl group, a phosphono group, an acetyl group, a halogen atom, an alkali metal atom, and the like.

[0059] In formula (A), X Ａ１and X Ａ２ is L Ａ１ Preferably, the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms.

[0060] In equation (B), X Ｂ１ and X Ｂ３ is L Ｂ１ It is preferable that the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms. Also, X Ｂ２ and X Ｂ３ is L Ｂ２ Preferably, the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms.

[0061] In equation (C), X Ｃ１ and X Ｃ４ is L Ｃ１ It is preferable that the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms. Also, X Ｃ２ and X Ｃ４ is L Ｃ２ It is preferable that the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms. Also, X Ｃ３ and X Ｃ４ is L Ｃ３Preferably, the atoms are separated by 1 to 10 atoms, more preferably by 1 to 6 atoms, even more preferably by 1 to 4 atoms, even more preferably by 1 to 3 atoms, and particularly preferably by 1 or 2 atoms.

[0062] Specific examples of polydentate ligands include 3-mercaptopropionic acid, thioglycolic acid, 2-aminoethanol, 2-aminoethanethiol, 2-mercaptoethanol, glycolic acid, ethylene glycol, ethylenediamine, aminosulfonic acid, glycine, aminomethyl phosphate, guanidine, diethylenetriamine, tris(2-aminoethyl)amine, 4-mercaptobutanoic acid, 3-aminopropanol, 3-mercaptopropanol, N-(3-aminopropyl)-1,3-propanediamine, 3-(bis(3-aminopropyl)amino)propan-1-ol, 1-thioglycerol, dimercaprol, 1-mercapto-2-butanol, 1-mercapto-2-pentanol, 3-mercapto-1-propanol, 2,3-dimercapto-1-propanol, diethanolamine, 2-(2 Examples include (-aminoethyl)aminoethanol, dimethylenthriamine, 1,1-oxybismethylamine, 1,1-thiobismethylamine, 2-[(2-aminoethyl)amino]ethanethiol, bis(2-mercaptoethyl)amine, 2-aminoethane-1-thiol, 1-amino-2-butanol, 1-amino-2-pentanol, L-cysteine, D-cysteine, 3-amino-1-propanol, L-homoserine, D-homoserine, aminohydroxyacetic acid, L-lactic acid, D-lactic acid, L-malic acid, D-malic acid, glyceric acid, 2-hydroxybutyric acid, L-tartaric acid, D-tartaric acid, tartaric acid, 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2-mercaptobenzoic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, and derivatives thereof.

[0063] The inorganic ligand is preferably an inorganic ligand containing a halogen element. Inorganic ligands containing halogen elements readily coordinate to quantum dots and can suppress the generation of surface defects.

[0064] Examples of halogen elements included in the inorganic ligands mentioned above include fluorine, chlorine, bromine, and iodine, with bromine being preferred.

[0065] Specific examples of inorganic ligands include zinc iodide, zinc bromide, zinc chloride, indium iodide, indium bromide, indium chloride, cadmium iodide, cadmium bromide, cadmium chloride, gallium iodide, gallium bromide, gallium chloride, tetrabutylammonium iodide, tetramethylammonium iodide, and ammonium sulfide.

[0066] Furthermore, in inorganic ligands containing halogen elements, halogen ions may dissociate from the aforementioned inorganic ligand and coordinate to the surface of the quantum dot. In addition, parts of the inorganic ligand other than the halogen atom may also coordinate to the surface of the quantum dot. To give a specific example, in the case of indium bromide, the indium bromide may coordinate to the surface of the quantum dot, or bromide ions or indium ions may coordinate to the surface of the quantum dot.

[0067] The total content of quantum dots and ligands in the photoelectric conversion layer 13 is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0068] The thickness of the photoelectric conversion layer 13 is preferably 10 to 600 nm, more preferably 50 to 600 nm, even more preferably 100 to 600 nm, and even more preferably 150 to 600 nm. The upper limit of the thickness of the photoelectric conversion layer 13 is preferably 550 nm or less, more preferably 500 nm or less, and even more preferably 450 nm or less.

[0069] The optical path length L of the light of the above wavelength λ in the photoelectric conversion layer 13 ３ The wavelength is preferably 50 to 2000 nm. The upper limit is preferably 1500 nm or less, and more preferably 1000 nm or less. The lower limit is preferably 70 nm or more, and more preferably 100 nm or more.

[0070] (First charge transport layer and second charge transport layer) Examples of charge transport layers include hole transport layers and electron transport layers. Preferably, one of the first charge transport layer 21 and the second charge transport layer 22 is a hole transport layer and the other is an electron transport layer.

[0071] The electron transport layer is also called the hole blocking layer. The electron transport layer is formed from an electron transport material that can perform this function.

[0072] Examples of electron transport materials include fullerene compounds such as [6,6]-Phenyl-C61-Butyric Acid Methyl Ester (PC61BM), perylene compounds such as perylenetetracarboxydiimide, tetracyanoquinodimethane, titanium dioxide, tin oxide, zinc oxide, indium oxide, indium tungsten oxide, indium zinc oxide, indium tin oxide, and fluorine-doped tin oxide. The electron transport material may also be in particle form. The electron transport material is preferably zinc oxide. Furthermore, zinc oxide is preferably in particle form (zinc oxide particles) from the viewpoint of reducing residual organic components and increasing the contact area with the photoelectric conversion layer.

[0073] Zinc oxide may also be zinc oxide doped with metal atoms other than Zn. Hereafter, zinc oxide doped with metal atoms other than Zn will also be referred to as doped zinc oxide.

[0074] The metal atoms other than Zn in doped zinc oxide are preferably 1- to 3-valent metal atoms, more preferably include at least one selected from Li, Mg, Al, and Ga, even more preferably Li, Mg, Al, or Ga, and particularly preferably Li or Mg.

[0075] In doped zinc oxide, the proportion of non-Zn metal atoms to the total of Zn and non-Zn metal atoms is preferably 1 atomic percent or more, more preferably 2 atomic percent or more, and even more preferably 4 atomic percent or more. The upper limit is preferably 20 atomic percent or less, more preferably 15 atomic percent or less, and even more preferably 12 atomic percent or less, from the viewpoint of suppressing the increase of crystal defects. The proportion of non-Zn metal atoms in doped zinc oxide can be measured by the inductively coupled plasma (ICP) method.

[0076] The average particle size of the zinc oxide particles is preferably 2 to 30 nm. Furthermore, the upper limit of the average particle size of the zinc oxide particles is preferably 20 nm or less, and more preferably 15 nm or less. When the average particle size of the zinc oxide particles is within the above range, a film with a large contact area with the photoelectric conversion layer and high flatness is easily obtained. In this specification, the average particle size value of the zinc oxide particles is the average value of 10 arbitrarily selected particle sizes. A transmission electron microscope can be used to measure the particle size of the zinc oxide particles.

[0077] The thickness of the electron transport layer is preferably 10 to 1000 nm. The upper limit is preferably 800 nm or less. The lower limit 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 to 20 times the thickness of the photoelectric conversion layer 13, more preferably 0.07 to 15 times, and even more preferably 0.1 to 10 times.

[0078] The optical path length L of the light with the above wavelength λ in the electron transport layer. ４ The optical path length L of the electron transport layer is preferably 6 to 600 nm. The upper limit is preferably 500 nm or less, and more preferably 450 nm or less. The lower limit is preferably 8 nm or more, and more preferably 10 nm or more. ４ The optical path length L of the photoelectric conversion layer 13 is ３ It is preferably 0.05 to 20 times, more preferably 0.07 to 15 times, and even more preferably 0.1 to 10 times.

[0079] The hole transport layer is a layer that has the function of transporting holes generated in the photoelectric conversion layer 13 to the first electrode 11 or the second electrode 12. The hole transport layer is also called the electron blocking layer. The hole transport layer is formed of a hole transport material that can perform this function. Examples of hole transport materials include PEDOT:PSS (a composite of poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonic acid)), PTB7 (poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-lt-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[ 3,4-b]thiophene-4,6-diyl}), PTB7-Th(poly([2,6'-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl l)carbonyl]thieno[3,4-b]thiophenediyl})), poly(3-hexylthiophene-2,5-diyl), poly(3-n-oct Poly(9,9'-dioctyl-fluorene-co-bithiophene), poly(3,3'''-didodecyl-quarterthiophene), poly(3,6-dioctylthiophene[3,2-b]thiophene), poly(2,5-bis(3-decylthiophene-2-yl)thieno[3,2-b]thiophene), poly(3,4-didecylthiophene-co-thieno[3,2-b]thiophene), poly(3,6-dioctylthiophene[3,2-b]thiophene-co-thieno[3,2-b]thiophene), poly(3,6-dioctylthiophene[3,2-b]thiophene-co-thiophene), poly(3,6-dioctylthiophene[3,2-b]thiophene-co-bithiophene), PC71BM ([6,6]-phenyl-C71-methyl butyrate), N ２ , N ２ , N ２’ , N ２’ , N ７ , N ７ , N ７’ , N ７’Examples include -octakis(4-methoxyphenyl)-9,9'-spirobi[9H-fluorene]-2,2',7,7'-tetraamine (Spiro-OMeTAD). Alternatively, organic hole transport materials described in paragraphs 0209 to 0212 of Japanese Patent Application Publication No. 2001-291534 can be used. Quantum dots can also be used as hole transport materials. Examples of quantum dot materials constituting quantum dots include nanoparticles (particles 0.5 nm to less than 100 nm in size) 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]. Specifically, PbS, PbSe, PbSeS, InN, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, Ag ２ S, Ag ２ Se, Ag ２ Examples include semiconductor materials with relatively narrow band gaps, such as Te, SnS, SnSe, SnTe, Si, and InP. Ligands may be coordinated to the surface of the quantum dots. For example, the use of PbS quantum dots as a hole transport layer is described in "NATURE COMMUNICATIONS (2018) 9:4267 DOI: 10.1038 / s41467-018-06399-4".

[0080] The thickness of the hole transport layer is preferably 5 to 500 nm. The lower limit is preferably 10 nm or more. The upper limit is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.

[0081] The optical path length L of the light with the above wavelength λ in the hole transport layer. ５ The optical path length L of the hole transport layer is preferably 3 to 300 nm. The upper limit is preferably 200 nm or less, and more preferably 150 nm or less. The lower limit is preferably 6 nm or more, and more preferably 8 nm or more. ５ The optical path length L of the photoelectric conversion layer 13 is ３It is preferably 0.05 to 3 times, more preferably 0.07 to 2 times, and even more preferably 0.1 to 1.5 times.

[0082] (Intermediate layer) Although not shown in the figures, the photodetector element of the present invention may have intermediate layers between the first electrode 11 and the first charge transport layer 21, and between the second electrode 12 and the second charge transport layer 22. Examples of intermediate layers include blocking layers and charge extraction layers.

[0083] The blocking layer is a layer that has the function of preventing reverse current. The blocking layer is also called a short-circuit prevention layer. Examples of materials that form the blocking layer include silicon dioxide, magnesium oxide, aluminum oxide, calcium carbonate, cesium carbonate, polyvinyl alcohol, polyurethane, titanium dioxide, tin oxide, zinc oxide, niobium oxide, tungsten oxide, molybdenum oxide, etc. The blocking layer may be a single layer film or a laminated film of two or more layers. The thickness of the blocking layer is preferably 1 to 500 nm. The upper limit is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. The lower limit is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Furthermore, the thickness of the blocking layer is preferably 0.01 to 5 times the thickness of the photoelectric conversion layer 13, more preferably 0.05 to 3 times, and even more preferably 0.1 to 1 time.

[0084] Materials for forming the charge extraction layer include metal oxides and organic semiconductors, with metal oxides being preferred. Examples of metal oxides include molybdenum oxide, titanium oxide, vanadium oxide, chromium oxide, cobalt oxide, nickel oxide, copper oxide, zirconium oxide, molybdenum oxide, silver oxide, tantalum oxide, and tungsten oxide, with molybdenum oxide being preferred. Examples of organic semiconductors include polythiophene compounds. The charge extraction layer may be a single layer or a laminate of two or more layers. The thickness of the charge extraction layer is preferably 1 to 100 nm. The lower limit is preferably 5 nm or more. The upper limit is preferably 50 nm or less.

[0085] <<Second Embodiment>> Figure 2 shows a second embodiment of the photodetector element. The arrows in the figure represent incident light to the photodetector element. The difference between the photodetector element 2 shown in Figure 2 and the first embodiment described above is that an optical path length adjustment layer 31 is provided on the light incident side of the first electrode 11. That is, in the photodetector element 2 shown in Figure 2, the optical path length adjustment layer 31 is located on the outermost surface of the photodetector element on the light incident side.

[0086] In the photodetector 2 shown in Figure 2, the optical path length of the light of the wavelength λ from the surface 12a of the second electrode layer 12 on the photoelectric conversion layer 13 side to the surface 31a of the optical path length adjustment layer 31 on the light incidence side is the optical path length L. １ This corresponds to the following. In the photodetector 2 shown in Figure 2, the wavelength λ of the light to be detected by the photodetector 1 and the optical path length L of the light of the above wavelength λ from the surface 12a on the photoelectric conversion layer 13 side of the second electrode layer 12 to the surface 31a on the light incident side of the optical path length adjustment layer 31. １ It is preferable that the above equation (1) satisfies the relationship, the above equation (1-1) satisfies the relationship, and it is more preferable that the above equation (1-2) satisfies the relationship.

[0087] The optical path length adjustment layer 31 preferably has a refractive index of 1.1 to 5.0 for light of the above wavelength λ. The upper limit is preferably 4.0 or less, and more preferably 3.0 or less. The lower limit is preferably 1.2 or more, and more preferably 1.3 or more. In this specification, the refractive index is the value at 23°C.

[0088] The optical path length adjustment layer 31 is made of SiO ２ , SION, TIO ２ Ta ２ O ５ , ZrO ２ , HfO ２ , Y ２ O ３ , and Al ２ O ３ Preferably, it includes at least one selected from the following.

[0089] The optical path length adjustment layer 31 may be a single layer or a laminate of two or more layers. The thickness of the optical path length adjustment layer 31 is preferably 10 to 1000 nm. The upper limit is preferably 800 nm or less. The lower limit is preferably 20 nm or more, and more preferably 50 nm or more.

[0090] The optical path length L of the light with the above wavelength λ in the optical path length adjustment layer 31 ６ The wavelength is preferably 6 to 700 nm. The upper limit is preferably 600 nm or less, and more preferably 500 nm or less. The lower limit is preferably 15 nm or more, and more preferably 30 nm or more.

[0091] <Image Sensor> The image sensor of the present invention includes the photodetector element of the present invention described above. The photodetector element of the present invention has excellent sensitivity to light in the infrared region. For this reason, the image sensor of the present invention can be preferably used as an infrared image sensor. Furthermore, the image sensor of the present invention can be preferably used to sense light with a wavelength of 900 to 2000 nm, and more preferably to sense light with a wavelength of 900 to 1600 nm.

[0092] The configuration of the image sensor is not particularly limited, as long as it includes the light detection element of the present invention and functions as an image sensor.

[0093] The image sensor of the present invention 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 to 650 nm.

[0094] 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.

[0095] 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.

[0096] 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 the longer wave 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.

[0097] 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 satisfying any of the following spectral characteristics (1) to (5) can be used. (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 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 to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more). (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 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 to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more). (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 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 to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more). (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 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 to 1500 nm is 70% or more (preferably 75% or more, more preferably 80% or more). (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 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 to 2000 nm is 70% or more (preferably 75% or more, more preferably 80% or more).

[0098] As infrared transmission filters, 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 can be used. 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.

[0099] 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.

[0100] 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 layers of dielectric thin films in the dielectric multilayer film, 2 to 100 layers are preferred, 4 to 60 layers are more preferred, and 6 to 40 layers are even more preferred. 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 ２ CeF ３ , HfO ２ La ２ O ３ , Nd ２ O ３ , Pr ６ O １１ , Sc ２ O ３SiO, 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 to 1.6 are preferred for forming the low refractive index layer. A specific example is 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 ６ These 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 to 0.5λ when the wavelength of light to be blocked is λ (nm). Specific examples of dielectric multilayer films include, for example, the films described in Japanese Patent Application Publication No. 2014-130344 and Japanese Patent Application Publication No. 2018-010296.

[0101] 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, more preferably 10% or less, and even more preferably 5% 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.

[0102] 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.

[0103] The image sensor may include a color separation filter layer. Examples of color separation filter layers include those containing colored pixels. Examples of colored pixels include red, green, blue, yellow, cyan, 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, the filter described in International Publication No. 2019 / 039172 can be used.

[0104] Furthermore, if the color separation layer contains 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.

[0105] Furthermore, if the image sensor includes an infrared transmission filter layer and a color separation layer, it is preferable that the color separation 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 layer are arranged in two dimensions. Note that two-dimensional arrangement of the infrared transmission filter layer and the color separation layer means that at least a portion of both lies on the same plane.

[0106] 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.

[0107] The present invention will be described in more 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.

[0108] <Preparation of PbS Quantum Dot Dispersion> (PbS Quantum Dot Dispersion 1-3) Measure 6.74 mL of oleic acid, 6.3 mmol of lead oxide, and 30 mL of octadecene into a flask and heat under vacuum at 120°C for 100 minutes to obtain a precursor solution. Then, adjust the temperature of the solution to 100°C, then bring the system into a nitrogen flow state, and then inject 2.5 mmol of hexamethyldisilatian together with 5 mL of octadecene. After holding for 1 minute after injection, allow the flask to cool naturally, and when it reaches 30°C, add 40 mL of toluene and collect the solution. Add an excess amount of ethanol to the solution and centrifuge at 10,000 rpm for 10 minutes to precipitate the target particles, PbS quantum dots. Then, add octane to the precipitate to obtain PbS Quantum Dot Dispersion 1-3 (dispersion of PbS quantum dots, concentration 10 mg / mL). A quantum dot thin film was fabricated using PbS quantum dot dispersion 1. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.32 eV, and the maximum absorption wavelength was 940 nm. A quantum dot thin film was fabricated using PbS quantum dot dispersion 2. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 0.88 eV, and the maximum absorption wavelength was 1450 nm. A quantum dot thin film was fabricated using PbS quantum dot dispersion 3. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.10 eV, and the maximum absorption wavelength was 1130 nm.

[0109] <Preparation of InAs Quantum Dot Dispersions> (InAs Quantum Dot Dispersions 1-3) Measure 1 mL of an octane dispersion of InAs quantum dots (InAs quantum dot concentration 70 mg / mL, oleic acid concentration 30 mg / mL), 0.5 g of 3-mercaptopropionic acid, and 10 mL of dimethylformamide as a solvent into a centrifuge tube and stir vigorously for 10 minutes. Next, add 30 mL of hexane and stir vigorously for 1 minute, then remove the upper hexane layer. Repeat this process twice. Next, add an excess amount of toluene and centrifuge at 4000 rpm for 5 minutes. After vacuum drying the obtained precipitate for 30 minutes, add 0.6 mL of dimethylformamide and stir for 2 hours to obtain InAs quantum dot dispersions 1-3. Note that all of the above operations should be carried out under nitrogen. A quantum dot thin film was fabricated using InAs quantum dot dispersion 1. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 0.88 eV, and the maximum absorption wavelength was 1450 nm. A quantum dot thin film was fabricated using InAs quantum dot dispersion 2. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.32 eV, and the maximum absorption wavelength was 940 nm. A quantum dot thin film was fabricated using InAs quantum dot dispersion 3. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.10 eV, and the maximum absorption wavelength was 1130 nm.

[0110] <Preparation of InAs / ZnS Quantum Dot Dispersions> (InAs / ZnS Quantum Dot Dispersions 1-3) InAs / ZnS quantum dot dispersions 1-3 are obtained in the same manner as the InAs quantum dot dispersions, except that InAs / ZnS quantum dots are used instead of InAs quantum dots. A quantum dot thin film is prepared using InAs / ZnS quantum dot dispersion 1, and the band gap estimated from the wavelength at which the absorption inflection point is observed from the absorption measurement of the quantum dot thin film is approximately 0.88 eV, and the maximum absorption wavelength is 1450 nm. A quantum dot thin film is prepared using InAs / ZnS quantum dot dispersion 2, and the band gap estimated from the wavelength at which the absorption inflection point is observed from the absorption measurement of the quantum dot thin film is approximately 1.32 eV, and the maximum absorption wavelength is 940 nm. A quantum dot thin film was fabricated using InAs / ZnS quantum dot dispersion 3. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.10 eV, and the maximum absorption wavelength was 1130 nm.

[0111] <Preparation of InAs / ZnSe Quantum Dot Dispersions> (InAs / ZnSe Quantum Dot Dispersions 1-3) InAs / ZnSe quantum dot dispersions 1-3 are obtained in the same manner as the InAs quantum dot dispersions, except that InAs / ZnSe quantum dots are used instead of InAs quantum dots. A quantum dot thin film is prepared using InAs / ZnSe quantum dot dispersion 1, and the band gap estimated from the wavelength at which the absorption inflection point is observed from the absorption measurement of the quantum dot thin film is approximately 0.88 eV, and the maximum absorption wavelength is 1450 nm. A quantum dot thin film is prepared using InAs / ZnSe quantum dot dispersion 2, and the band gap estimated from the wavelength at which the absorption inflection point is observed from the absorption measurement of the quantum dot thin film is approximately 1.32 eV, and the maximum absorption wavelength is 940 nm. A quantum dot thin film was fabricated using InAs / ZnSe quantum dot dispersion 3. The band gap estimated from the wavelength at which the absorption inflection point was observed in the absorption measurement of the quantum dot thin film was approximately 1.10 eV, and the maximum absorption wavelength was 1130 nm.

[0112] <Preparation of Zinc Oxide Particle Dispersion> (Zinc Oxide Particle Dispersion 1) Measure 1.5 mmol of zinc acetate dihydrate and 15 mL of dimethyl sulfoxide (DMSO) into a flask and stir to obtain a zinc acetate solution. Prepare a TMACL solution by dissolving 4 mmol of tetramethylammonium chloride (TMACL) in 4 mL of methanol, and a KOH solution by dissolving 4 mmol of potassium hydroxide (KOH) in 4 mL of methanol. Slowly add the KOH solution to the TMACL solution while stirring vigorously, and after stirring for 30 minutes, remove insoluble components by passing the solution through a 0.45 μm pore size filter to obtain a tetramethylammonium hydroxide (TMAH) solution. Add 6 mL of TMAH solution to the zinc acetate solution in the flask at a dropping rate of 6 mL / min. After holding for 1 hour, collect the reaction mixture. An excess amount of acetone is added to the reaction mixture, and the mixture is centrifuged at 10,000 rpm for 10 minutes. The supernatant is removed, the precipitate is dispersed in methanol, and then precipitated again with acetone. 5 ml of ethanol and 80 μl of aminoethanol are added, and the mixture is dispersed ultrasonically to obtain zinc oxide particle dispersion 1 with a concentration of undoped zinc oxide particles of approximately 30 mg / mL.

[0113] <Manufacturing of Photodetector> (Example A1) A second electrode is formed by depositing an Au film on quartz glass using a sputtering method via a metal mask. Next, PbS quantum dot dispersion 1 is dropped onto the second electrode and spin-coated at 2500 rpm to obtain a PbS quantum dot aggregate film (Step 1). Next, an acetonitrile solution of 1,2-entanedithiol (concentration 0.01 v / v%) is dropped onto the PbS quantum dot aggregate film as a ligand solution, left to stand for 10 seconds, and then spin-dried at 2500 rpm for 10 seconds to replace the ligands coordinated to the PbS quantum dots with 1,2-entanedithiol. Next, acetonitrile is dropped onto the PbS quantum dot aggregate film as a rinse solution and spin-dried at 2500 rpm for 20 seconds (Step 2). The process of combining steps 1 and 2 is repeated for three cycles to form a semiconductor film with a thickness of 60 nm, consisting of a PbS film in which 1,2-entanedithiol is coordinated as a ligand to PbS quantum dots, thereby obtaining a second charge transport layer. Next, InAs quantum dot dispersion 1 is dropped onto the second charge transport layer, then spin-coated at 1000 rpm and dried at 120°C for 10 minutes to form a photoelectric conversion layer. Next, zinc oxide particle dispersion 1 is dropped onto the photoelectric conversion layer, spin-coated at 3000 rpm, and heated at 60°C for 5 minutes, and this process is repeated twice to form a zinc oxide particle film, thereby forming a first charge transport layer (electron transport layer). Next, an ITO (Indium Tin Oxide) film is formed on the first charge transport layer by sputtering to form a first electrode, and a photodiode type photodetector is manufactured.

[0114] (Examples A2-A7, Comparative Examples A1-A3) The photodetectors of Examples A2-A9 and Comparative Examples A1-A3 are manufactured in the same manner as in Example A1, except that the film thickness of each layer is changed.

[0115]

[0116] (Example B1) After forming the first electrode in the same manner as in Example A1, SiO was applied to the first electrode by sputtering. ２ A film is fabricated to form an optical path length adjustment layer, and a photodiode-type photodetector is manufactured.

[0117] (Examples B2 and B3) The photodetector elements of Examples B2 and B3 are manufactured in the same manner as in Example B1, except that the film thickness of each layer and the material of the optical path length adjustment layer are changed.

[0118]

[0119] (Example C1) A second electrode is formed by depositing an Au film on quartz glass using a sputtering method via a metal mask. Next, a toluene solution (concentration 10 mg / mL) of the compound (Spiro-OMeTAD) having the structure shown below is spin-coated onto the second electrode at 2000 rpm to form a second charge transport layer (hole transport layer). Next, an InAs quantum dot dispersion 2 is dropped onto the second charge transport layer, then spin-coated at 1000 rpm and dried at 120°C for 10 minutes to form a photoelectric conversion layer. Then, a zinc oxide particle dispersion 1 is dropped onto the photoelectric conversion layer, spin-coated at 3000 rpm, and heated at 60°C for 5 minutes. This process is repeated twice to form a zinc oxide particle film, thereby forming the first charge transport layer (electron transport layer). Next, an ITO (Indium Tin Oxide) film is formed on the first charge transport layer by sputtering to form the first electrode, and a photodiode type photodetector element is manufactured.

[0120] (Example C2) The photodetector element of Example C2 is manufactured in the same manner as in Example C1, except that InAs quantum dot dispersion 1 is used instead of InAs quantum dot dispersion 2.

[0121] (Example C3) The photodetector element of Example C3 is manufactured in the same manner as in Example C1, except that PbS quantum dot dispersion 2 is used instead of InAs quantum dot dispersion 2.

[0122] (Example C4) The photodetector element of Example C4 is manufactured in the same manner as in Example C1, except that InAs / ZnS quantum dot dispersion 1 is used instead of InAs quantum dot dispersion 2.

[0123] (Example C5) The photodetector element of Example C5 is manufactured in the same manner as in Example C1, except that InAs / ZnSe quantum dot dispersion 1 is used instead of InAs quantum dot dispersion 2.

[0124] (Example C6) The photodetector element of Example C6 is manufactured in the same manner as in Example C1, except that InAs / ZnS quantum dot dispersion 2 is used instead of InAs quantum dot dispersion 2.

[0125] (Example C7) The photodetector element of Example C7 is manufactured in the same manner as in Example C1, except that InAs / ZnSe quantum dot dispersion 2 is used instead of InAs quantum dot dispersion 2.

[0126] (Example C8) The photodetector element of Example C8 is manufactured in the same manner as in Example C1, except that InAs quantum dot dispersion 3 is used instead of InAs quantum dot dispersion 2.

[0127] (Example C9) The photodetector element of Example C9 is manufactured in the same manner as in Example C1, except that PbS quantum dot dispersion 3 is used instead of InAs quantum dot dispersion 2.

[0128] (Example C10) The photodetector element of Example C10 is manufactured in the same manner as in Example C1, except that InAs / ZnS quantum dot dispersion 3 is used instead of InAs quantum dot dispersion 2.

[0129] (Example C11) The photodetector element of Example C11 is manufactured in the same manner as in Example C1, except that InAs / ZnSe quantum dot dispersion 3 is used instead of InAs quantum dot dispersion 2.

[0130] (Comparative Example C1) The photodetector element of Comparative Example C1 is manufactured in the same manner as in Example C1, except that the film thickness of the first charge transport layer is changed.

[0131] (Example D1) The photodetector element of Example D1 is manufactured in the same manner as in Example C1, except that PbS quantum dot dispersion 1 is used instead of InAs quantum dot dispersion 2.

[0132] (Comparative Example D1) The photodetector element of Comparative Example D1 is manufactured in the same manner as in Example D1, except that the film thickness of the first charge transport layer is changed.

[0133]

[0134] <Evaluation of Light Absorption Rate> For each photodetector element, the refractive index and extinction coefficient of each layer are measured using an infrared spectroscopic ellipsometer (IR-VASE, J.A. Wollam). Using the measured refractive index and extinction coefficient, along with the film thickness of each layer listed in the table, as input data, the light absorption rate of the photoelectric conversion layer for incident light of wavelength λ, which is the light to be detected by the photodetector element, is calculated using multilayer interference simulation software (Essential Macleod, Thin Film Center Inc.). In the photodetectors of Examples A1-A7, Examples B1-B3, Examples C2-C5, and Comparative Examples A1-A3, the wavelength λ of the light to be detected by the photodetector was set to 1450 nm. In the photodetectors of Examples C1, C6, C7, Example D1, Comparative Example C1, and Comparative Example D1, the wavelength λ of the light to be detected by the photodetector was set to 940 nm, and the light absorption rate was calculated accordingly. In the photodetectors of Examples C8-C11, the wavelength λ of the light to be detected by the photodetector was set to 1130 nm, and the light absorption rate was calculated accordingly. In the table below, the value of λ represents the wavelength of the light to be detected by the photodetector (in nm). Also, in the table below, L １ Regarding the value of L in Examples A1 to A7, Examples C1 to C11, Example D1, and Comparative Examples A1 to A3, C1, and D1, it is the optical path length of light with wavelength λ from the surface on the photoelectric conversion layer side of the second electrode to the surface of the first electrode, and in Examples B1 to B3, it is the optical path length of light with wavelength λ from the surface on the photoelectric conversion layer side of the second electrode to the surface of the optical path length adjustment layer. Also, L in the table below ２ The value is measured from the surface of the photoelectric conversion layer on the second electrode to the L of the photoelectric conversion layer. ３ L is the optical path length of light with wavelengths λ up to 2 / 2.３ This value represents the optical path length of light with wavelength λ in the photoelectric conversion layer.

[0135]

[0136]

[0137]

[0138] As shown in the table above, L １ The photodetector element in the embodiment where the value of / λ is within the range defined in the claim (greater than 0.59 and less than 0.84) exhibits a high light absorption rate.

[0139] By using the photodetector element obtained in the above embodiment and fabricating an image sensor using a known method together with an optical filter prepared according to the methods described in International Publication No. 2016 / 186050 and International Publication No. 2016 / 190162, and incorporating it into a solid-state image sensor, an image sensor with good visible and infrared imaging performance can be obtained.

[0140] 1, 2: Photodetector element 11: First electrode 12: Second electrode 13: Photoelectric conversion layer 21: First charge transport layer 22: Second charge transport layer 31: Optical path length adjustment layer

Claims

1. A photodetector comprising: a first electrode; a second electrode; a photoelectric conversion layer including an aggregate of quantum dots between the first electrode and the second electrode; a first charge transport layer between the photoelectric conversion layer and the first electrode; and a second charge transport layer between the photoelectric conversion layer and the second electrode, wherein the first electrode is provided on the light incident side of the second electrode, and the wavelength λ of the light to be detected by the photodetector, and the optical path length L of the light of the wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the photodetector on the light incident side. １ A photodetector that satisfies the relationship in equation (1). 0.59 < L １ / λ < 0.84 ... (1) In equation (1), λ is the wavelength of the light to be detected by the photodetector, L １ This is the optical path length of the light of the wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the photodetector on the light incident side.

2. The first electrode is located on the outermost surface of the light-incident side of the photodetector, and the optical path length L １ The photodetector element according to claim 1, wherein is the optical path length of light of wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the first electrode on the light incidence side.

3. Furthermore, the first electrode has an optical path length adjustment layer on the light incident side, and the optical path length adjustment layer is located on the outermost layer on the light incident side of the photodetector, and the optical path length L １ The photodetector element according to claim 1, wherein is the optical path length of light of wavelength λ from the surface of the second electrode on the photoelectric conversion layer side to the surface of the optical path length adjustment layer on the light incidence side.

4. The photodetecting element according to claim 3, wherein said optical path length adjusting layer comprises at least one selected from the group consisting of SiO ２ , SiON, TiO ２ , Ta ２ O ５ , ZrO ２ , HfO ２ , Y ２ O ３ , and Al ２ O ３ .

5. The photodetector is a photodetector according to any one of claims 1 to 4, satisfying the relationship in formula (2); 0.10 < L ２ / λ < 0.50 ... (2) In equation (2), λ is the wavelength of the light to be detected by the photodetector, L ２ From the surface of the second electrode on the photoelectric conversion layer side, L of the photoelectric conversion layer ３ L is the optical path length of light of the aforementioned wavelength λ up to 2 / 2. ３ This is the optical path length of the light with wavelength λ in the photoelectric conversion layer.

6. The photodetector is the photodetector according to any one of claims 1 to 4, satisfying the relationship in formula (3). 0.05 < L ３ / λ ... (3) In equation (3), λ is the wavelength of the light to be detected by the photodetector, L ３ This is the optical path length of the light with wavelength λ in the photoelectric conversion layer.

7. The photodetector according to any one of claims 1 to 4, wherein the light to be detected by the photodetector is light in the wavelength range of 700 to 2500 nm.

8. An image sensor comprising a photodetector element according to any one of claims 1 to 4.

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