Semiconductor film, light detection element, and image sensor

Abstract

Provided is a semiconductor film including an aggregate of semiconductor quantum dots including indium and a group 15 element, and a ligand coordinated to the semiconductor quantum dots, wherein the group 15 element includes antimony, the ligand includes a ligand containing halogen, the semiconductor film includes nitrogen, and the molar ratio of nitrogen to indium is 0.01 to 0.10. Also provided is a light detection element and an image sensor using the semiconductor film.

Description

Semiconductor film, photodetector element and image sensor

[0001] The present invention relates to a semiconductor film containing semiconductor quantum dots, and also to a photodetector and an image sensor.

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

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

[0004] Furthermore, InGaAs-based semiconductor materials, which are known as near-infrared light receiving elements, have the problem of requiring very costly processes, such as epitaxial growth and substrate bonding processes, to achieve high quantum efficiency, and this has prevented them from becoming widely used.

[0005] In recent years, the use of quantum dots in photodetectors has also been considered.

[0006] Patent Document 1 describes the use of PbS quantum dots in the photoelectric conversion layer of a PbS quantum dot photodetector element.

[0007] Patent Document 2 describes the use of InSb quantum dots in the photoelectric conversion layer of a photodetector element.

[0008] JP 2020-150251 A U.S. Pat. No. 1,581,501

[0009] In recent years, with the demand for improved performance of image sensors and the like, further improvements are being demanded in the characteristics required of the photodetector elements used therein. For example, one of the characteristics required of a photodetector element is that it has a high external quantum efficiency for light of the target wavelength to be detected by the photodetector element, and that the external quantum efficiency of the photodetector element has little variation within its surface. By increasing the external quantum efficiency of the photodetector element, it is possible to improve the light detection accuracy of the photodetector element. Furthermore, by reducing the variation within the surface of the external quantum efficiency of the photodetector element, it is possible to suppress the generation of noise and the like.

[0010] Furthermore, it is preferable for the dark current of the photodetector element to be small. By reducing the dark current of the photodetector element, a higher signal-to-noise ratio (S / N ratio) can be obtained in the image sensor. Dark current is the current that flows when no light is irradiated.

[0011] The present inventors have conducted further studies on a photodetector element using semiconductor quantum dots containing In and a Group 15 element in a photoelectric conversion layer, and have found that there is room for further improvement in these characteristics.

[0012] Therefore, an object of the present invention is to provide a semiconductor film, a photodetector, and an image sensor that have high external quantum efficiency, excellent in-plane uniformity of the external quantum efficiency, and reduced dark current.

[0013] The present invention provides the following:

[0014] <1> A semiconductor film including an aggregate of semiconductor quantum dots containing In and a Group 15 element, and ligands coordinated to the semiconductor quantum dots, wherein the Group 15 element includes Sb, the ligands include a ligand containing a halogen element, and the semiconductor film includes nitrogen, wherein a molar ratio of nitrogen to In is 0.01 to 0.10. <2> The semiconductor film according to <1>, wherein the molar ratio of nitrogen to halogen in the semiconductor film is 0.01 to 0.20. <3> The semiconductor film according to <1>, wherein the molar ratio of nitrogen to halogen in the semiconductor film is 0.01 to 0.10. <4> The semiconductor film according to any one of <1> to <3>, wherein the molar ratio of Sb to halogen in the semiconductor film is 0.30 to 3.20. <5> The semiconductor film according to any one of <1> to <4>, wherein the ligand containing a halogen is a ligand containing iodine. <6> The semiconductor film according to any one of <1> to <5>, wherein the ligand includes a ligand containing a sulfur element. <7> The semiconductor film according to any one of <1> to <6>, wherein the ligand containing a halogen element includes an In element. <8> The semiconductor film according to any one of <1> to <7>, wherein the semiconductor quantum dots have a band gap of 1.0 eV or less. <9> A photodetector including the semiconductor film according to any one of <1> to <8>. <10> An image sensor including the photodetector according to <9>.

[0015] According to the present invention, it is possible to provide a semiconductor film, a photodetector, and an image sensor that have high external quantum efficiency, excellent in-plane uniformity of the external quantum efficiency, and reduced dark current.

[0016] FIG. 2 illustrates an embodiment of a photodetector element.

[0017] The present invention will be described in detail below. In this specification, the term "to" is used to mean that the numerical values ​​before and after it are included as the lower and upper limits. In the description of groups (atomic groups) in this specification, a notation that does not specify whether they are substituted or unsubstituted includes both groups (atomic groups) that have no substituents and groups (atomic groups) that have substituents. For example, the term "alkyl group" includes not only alkyl groups that have no substituents (unsubstituted alkyl groups) but also alkyl groups that have substituents (substituted alkyl groups).

[0018] <Semiconductor Film> The semiconductor film of the present invention is a semiconductor film comprising an aggregate of semiconductor quantum dots each containing an In element and a Group 15 element, and ligands coordinated to the semiconductor quantum dots, wherein the Group 15 element includes an Sb element, the ligands include a ligand containing a halogen element, and the semiconductor film contains a nitrogen element, and the molar ratio of the nitrogen element to the In element is 0.01 to 0.10.

[0019] The semiconductor film of the present invention has high external quantum efficiency, excellent in-plane uniformity of the external quantum efficiency, and suppressed dark current. Although the detailed reasons for such effects are unknown, they are presumed to be due to the following.

[0020] The semiconductor film contains a halogen-containing ligand and a predetermined amount of nitrogen, which is believed to maintain an appropriate distance between the semiconductor quantum dots and reduce surface defects of the semiconductor quantum dots, resulting in a semiconductor film with high external quantum efficiency, excellent in-plane uniformity of the external quantum efficiency, and suppressed dark current.

[0021] The semiconductor film of the present invention contains nitrogen, and the nitrogen-containing component contained in the semiconductor film of the present invention is, for example, a ligand. The semiconductor film of the present invention preferably contains a ligand containing nitrogen, and the molar ratio of nitrogen to In is preferably 0.01 to 0.10.

[0022] In the semiconductor film of the present invention, the molar ratio of nitrogen element to In element (number of moles of nitrogen element / number of moles of In element) is preferably 0.01 to 0.07, and more preferably 0.01 to 0.03.

[0023] In the semiconductor film of the present invention, the molar ratio of nitrogen element to halogen element (moles of nitrogen element / moles of halogen element) is preferably 0.01 to 0.20, and more preferably 0.01 to 0.10.

[0024] In the semiconductor film of the present invention, the molar ratio of Sb to halogen elements (moles of Sb element / moles of halogen element) is preferably 0.30 to 3.20, and more preferably 0.50 to 3.00. The lower limit of the molar ratio of Sb to halogen elements is preferably 0.60 or more, and more preferably 1.00 or more. The upper limit of the molar ratio of Sb to halogen elements is preferably 2.90 or less, and more preferably 2.80 or less.

[0025] In this specification, the "molar ratio of nitrogen element to In element," "molar ratio of nitrogen element to halogen element," and "molar ratio of Sb element to halogen element" for a semiconductor film can be calculated by measuring the elemental composition ratio of the semiconductor film by X-ray photoelectron spectroscopy.

[0026] The semiconductor film of the present invention can be used in a photodetector or an image sensor. More specifically, the semiconductor film can be used as a photoelectric conversion layer of a photodetector or an image sensor. Therefore, the semiconductor film of the present invention is preferably used for the photoelectric conversion layer of a photodetector or an image sensor.

[0027] Since the semiconductor film of the present invention has excellent sensitivity to light with wavelengths in the infrared region, an image sensor using the semiconductor film of the present invention as a photoelectric conversion layer can be particularly preferably used as an infrared sensor. Therefore, the semiconductor film of the present invention is preferably used for the photoelectric conversion layer of an infrared sensor.

[0028] The thickness of the semiconductor film is not particularly limited, but is preferably 10 to 1000 nm from the viewpoint of obtaining high electrical conductivity. The lower limit of the thickness is preferably 20 nm or more, and more preferably 30 nm or more. The upper limit of the thickness is preferably 600 nm or less, more preferably 550 nm or less, even more preferably 500 nm or less, and particularly preferably 450 nm or less.

[0029] (Aggregate of semiconductor quantum dots containing In element and Group 15 element) The semiconductor film of the present invention has an aggregate of semiconductor quantum dots containing In element and Group 15 element. The Group 15 element in the semiconductor quantum dots includes Sb element. The aggregate of semiconductor quantum dots refers to a large number (for example, 1 μm ２ In this specification, the term "semiconductor" refers to a semiconductor having a resistivity of 10 －２ Ωcm or more 10 ８ This refers to a substance with a resistivity of Ωcm or less.

[0030] Examples of semiconductor quantum dot materials that constitute semiconductor quantum dots include compound semiconductors that contain In and a Group 15 element, where the Group 15 element contains Sb. A compound semiconductor is a semiconductor that is composed of two or more elements. Therefore, in this specification, a "compound semiconductor that contains In and a Group 15 element" refers to a compound semiconductor that contains In and a Group 15 element as elements that constitute the compound semiconductor.

[0031] In the semiconductor quantum dots, the ratio of the number of In elements to the number of Group 15 elements is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. The upper limit is preferably 3.0 or less.

[0032] In this specification, the ratio of the number of In elements to the number of Group 15 elements in semiconductor quantum dots can be calculated by measuring the elemental composition ratio of the semiconductor quantum dots by X-ray photoelectron spectroscopy. For example, the ratio can be calculated by forming a film using a dispersion of semiconductor quantum dots and measuring the elemental composition ratio of the semiconductor quantum dots in this film by X-ray photoelectron spectroscopy.

[0033] Examples of means for making the ratio of the number of In elements to the number of Group 15 elements in semiconductor quantum dots 1.1 or more include: (1) a method of adjusting the mixing ratio of compound A containing In elements and compound B containing Sb elements when synthesizing semiconductor quantum dots (for example, making the molar ratio of In elements to Sb elements 2.1 or more); (2) a method of controlling the amount of reducing agent (dioctyl ether of lithium triethylborohydride, etc.) added and the injection rate when synthesizing semiconductor quantum dots; and (3) a method of controlling the temperature profile, such as the temperature reached in the reaction, the holding time, and the heating rate.

[0034] The semiconductor quantum dots may further contain elements other than In and Sb, such as Mg, Ca, Sr, Ba, Zn, Cd, Hg, B, Al, Ga, N, P, As, and Bi, with Zn, Al, Ga, P, As, and Bi being preferred.

[0035] Specific examples of semiconductor quantum dots include InSb and InSbAs.

[0036] The crystal structure of the semiconductor quantum dots is not particularly limited. Various crystal structures can be adopted depending on the type and composition ratio of elements constituting the semiconductor quantum dots, but a cubic or hexagonal crystal structure is preferred because it is easy to appropriately control the band gap as a semiconductor and to achieve high crystallinity. When the proportion of pure InSb in the particles as a whole is high, a zinc blende structure is preferred because it is easy to achieve high crystallinity. The crystal structure of the semiconductor quantum dots can be measured by X-ray diffraction or electron diffraction.

[0037] The band gap of the semiconductor quantum dots is preferably 1.2 eV or less, more preferably 1.0 eV or less. The lower limit of the band gap of the semiconductor quantum dots is not particularly limited, but is preferably 0.3 eV or more, more preferably 0.5 eV or more.

[0038] The average particle size of the semiconductor quantum dots is preferably 3 to 20 nm. The upper limit of the average particle size of the semiconductor quantum dots is preferably 15 nm or less, and more preferably 10 nm or less. If the average particle size of the semiconductor quantum dots is within the above range, a photodetector element can be obtained that has a high external quantum efficiency for light with wavelengths in the infrared region. Note that, in this specification, the value of the average particle size of the semiconductor quantum dots is the average value of the particle sizes of 10 arbitrarily selected semiconductor quantum dots. The particle size of the semiconductor quantum dots can be measured using a transmission electron microscope.

[0039] (Ligand) The semiconductor film of the present invention contains a ligand that is coordinated to the semiconductor quantum dot. The ligand includes a ligand that contains at least a halogen element. The ligand may further include an organic ligand.

[0040] The halogen-containing ligand is preferably an inorganic ligand containing a halogen element, which can be easily coordinated to the semiconductor quantum dots and can suppress the occurrence of surface defects.

[0041] The halogen-containing ligand preferably contains In. In particular, when the semiconductor quantum dots have InSb as the host crystal, the halogen-containing ligand containing In is thought to be more likely to coordinate to the Sb site of the semiconductor quantum dots, thereby further suppressing the occurrence of surface defects.

[0042] Examples of the halogen element contained in the halogen-containing ligand include fluorine, chlorine, bromine and iodine, with iodine being preferred.

[0043] Specific examples of the ligand containing a halogen element include zinc iodide, zinc bromide, zinc chloride, indium iodide, indium bromide, indium chloride, cadmium iodide, cadmium bromide, cadmium chloride, gallium iodide, gallium bromide, and gallium chloride, with indium iodide being preferred.

[0044] In addition, in the case of a ligand containing a halogen element, a halogen ion may dissociate from the ligand and be coordinated to the surface of the semiconductor quantum dot. Furthermore, a portion of the ligand other than the halogen element may also be coordinated to the surface of the semiconductor quantum dot. To give a specific example, in the case of indium iodide, indium iodide may be coordinated to the surface of the semiconductor quantum dot, or iodine ions or indium ions may be coordinated to the surface of the semiconductor quantum dot.

[0045] The organic ligand may be a monodentate organic ligand having one coordination moiety, or a polydentate organic ligand having two or more coordination moieties. Examples of the coordination moiety contained in the organic ligand include a thiol group, an amino group, a hydroxy group, a carboxy group, a sulfo group, a phospho group, and a phosphonic acid group. The organic ligand preferably contains a thiol group. The organic ligand may also contain an organic ligand containing a nitrogen element.

[0046] Specific examples of the monodentate organic ligand include oleylamine, ammonium acetate, 2-naphthylamine, 4-methylthioaniline, 4-methylbenzenethiol, 3,5-dimethylbenzenethiol, 4-chlorobenzenethiol, 4-methoxybenzenethiol, and benzoic acid.

[0047] The polydentate ligand may be a ligand represented by any one of formulas (A) to (C).

[0048] In formula (A), X Ａ１ and X Ａ２ each independently represents a thiol group, an amino group, a hydroxy group, a carboxy group, a sulfo group, a phospho group, or a phosphonic acid group; L Ａ１ represents a hydrocarbon group.

[0049] In formula (B), X Ｂ１ and X Ｂ２ each independently represents a thiol group, an amino group, a hydroxy group, a carboxy group, a sulfo group, a phospho group, or a phosphonic acid group; Ｂ３ represents S, O or NH; L Ｂ１ and L Ｂ２ each independently represents a hydrocarbon group.

[0050] In formula (C), X Ｃ１ ~X Ｃ３ each independently represents a thiol group, an amino group, a hydroxy group, a carboxy group, a sulfo group, a phospho group, or a phosphonic acid group; Ｃ４ represents N, and L Ｃ１ ~L Ｃ３ each independently represents a hydrocarbon group.

[0051] X Ａ１ , X Ａ２ , X Ｂ１ , X Ｂ２ , X Ｃ１ , X Ｃ２ and X Ｃ３ The amino group represented by is -NH ２ The amino group is not limited to the above, and also includes a substituted amino group and a cyclic amino group. Examples of the substituted amino group include a monoalkylamino group, a dialkylamino group, a monoarylamino group, a diarylamino group, and an alkylarylamino group. The amino group represented by these groups includes -NH ２ , a monoalkylamino group, or a dialkylamino group is preferred, and —NH ２ It is more preferable that:

[0052] X in formula (A) Ａ１ and X Ａ２ At least one of the groups 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.

[0053] X in formula (B) Ｂ１ and X Ｂ２At least one of the groups 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.

[0054] X in formula (C) Ｃ１ ~X Ｃ３ At least one of the groups 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] L Ａ１ , L Ｂ１ , L Ｂ２ , L Ｃ１ , L Ｃ２ and L Ｃ３ The hydrocarbon group represented by 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 hydrocarbon group preferably has 1 to 20 carbon atoms. The upper limit of the carbon number is preferably 10 or less, more preferably 6 or less, and even more preferably 3 or less. Specific examples of the hydrocarbon group include an alkylene group, an alkenylene group, an alkynylene group, and an arylene group.

[0056] Examples of the alkylene group include a linear alkylene group, a branched alkylene group, and a cyclic alkylene group, and are preferably a linear alkylene group or a branched alkylene group, and more preferably a linear alkylene group. Examples of the alkenylene group include a linear alkenylene group, a branched alkenylene group, and a cyclic alkenylene group, and are preferably a linear alkenylene group or a branched alkenylene group, and more preferably a linear alkenylene group. Examples of the alkynylene group include a linear alkynylene group and a branched alkynylene group, and are preferably a linear alkynylene group. The arylene group may be monocyclic or polycyclic. A monocyclic arylene group is preferred. Specific examples of the arylene group include a phenylene group and a naphthylene group, and are 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. Specific preferred examples of the group having 1 to 10 atoms include alkyl groups having 1 to 3 carbon atoms [methyl, ethyl, propyl, and isopropyl], alkenyl groups having 2 to 3 carbon atoms [ethenyl and propenyl], alkynyl groups having 2 to 4 carbon atoms [ethynyl, propynyl, etc.], cyclopropyl groups, alkoxy groups having 1 to 2 carbon atoms [methoxy and ethoxy], acyl groups having 2 to 3 carbon atoms [acetyl and propionyl], alkoxycarbonyl groups having 2 to 3 carbon atoms [methoxycarbonyl and ethoxycarbonyl], acyloxy groups having 2 carbon atoms [acetyloxy], Examples of such an alkyl group include an acylamino group (acetylamino group), a hydroxyalkyl group having 1 to 3 carbon atoms (hydroxymethyl group, hydroxyethyl group, 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, and an alkali metal atom.

[0057] In formula (A), X Ａ１and X Ａ２ Is L Ａ１ Preferably, they 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.

[0058] In formula (B), X Ｂ１ and X Ｂ３ Is L Ｂ１ Preferably, they are separated by 1 to 10 atoms, more preferably 1 to 6 atoms, even more preferably 1 to 4 atoms, still more preferably 1 to 3 atoms, and particularly preferably 1 or 2 atoms. Ｂ２ and X Ｂ３ Is L Ｂ２ Preferably, they 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.

[0059] In formula (C), X Ｃ１ and X Ｃ４ Is L Ｃ１ Preferably, they are separated by 1 to 10 atoms, more preferably 1 to 6 atoms, even more preferably 1 to 4 atoms, still more preferably 1 to 3 atoms, and particularly preferably 1 or 2 atoms. Ｃ２ and X Ｃ４ Is L Ｃ２ Preferably, they are separated by 1 to 10 atoms, more preferably 1 to 6 atoms, even more preferably 1 to 4 atoms, still more preferably 1 to 3 atoms, and particularly preferably 1 or 2 atoms. Ｃ３ and X Ｃ４ Is L Ｃ３Preferably, they 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 addition, X Ａ１ and X Ａ２ Is L Ａ１ The term "separated by 1 to 10 atoms" means that X Ａ１ and X Ａ２ This means that the number of atoms constituting the molecular chain with the shortest distance connecting X is 1 to 10. For example, in the case of the following formula (A1), X Ａ１ and X Ａ２ and are separated by two atoms, and in the case of the following formula (A2) and formula (A3), X Ａ１ and X Ａ２ The numbers in the following structural formulas represent X Ａ１ and X Ａ２ It represents the order of the arrangement of atoms that make up the shortest molecular chain connecting the

[0061] To explain this by taking a specific compound, 3-mercaptopropionic acid is X Ａ１ The site corresponding to X is a carboxyl group. Ａ２ The site corresponding to is a thiol group, and L Ａ１ In 3-mercaptopropionic acid, the site corresponding to X is an ethylene group (compound with the following structure). Ａ１ (carboxy group) and X Ａ２ (thiol group) and L Ａ１ (ethylene group) separates them by two atoms.

[0062] X Ｂ１ and X Ｂ３ Is L Ｂ１ are separated by 1 to 10 atoms, Ｂ２ and X Ｂ３ Is L Ｂ２ are separated by 1 to 10 atoms, Ｃ１ and X Ｃ４ Is L Ｃ１ are separated by 1 to 10 atoms,Ｃ２ and X Ｃ４ Is L Ｃ２ are separated by 1 to 10 atoms, Ｃ３ and X Ｃ４ Is L Ｃ３ The meaning of being separated by 1 to 10 atoms is the same as above.

[0063] Specific examples of the polydentate ligand include 3-mercaptopropionic acid, thioglycolic acid, 2-aminoethanol, 2-aminoethanethiol, 2-mercaptoethanol, glycolic acid, ethylene glycol, ethylenediamine, aminosulfonic acid, glycine, aminomethylphosphate, 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 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, tartronic acid, 1,2-benzenedithiol, 1,3-benzenedithiol, 1,4-benzenedithiol, 2-mercaptobenzoic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, and derivatives thereof.

[0064] The total content of semiconductor quantum dots and ligands in the semiconductor film of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0065] <Method for Producing Semiconductor Film> The semiconductor film of the present invention can be produced by applying a dispersion containing the above-described semiconductor quantum dots, a solvent, and a ligand onto a substrate.

[0066] Examples of the semiconductor quantum dots contained in the dispersion include the semiconductor quantum dots described in the semiconductor film section above, and the preferred ranges are the same. The content of the semiconductor quantum dots in the dispersion is preferably 10 to 500 mg / mL. The lower limit is preferably 50 mg / mL or more, and more preferably 80 mg / mL or more. The upper limit is preferably 300 mg / mL or less, and more preferably 200 mg / mL or less.

[0067] Examples of the ligand contained in the dispersion include the ligands described in the semiconductor film section above. The dispersion may also contain a ligand that functions as a ligand that coordinates to the semiconductor quantum dots and has a molecular structure that easily causes steric hindrance, thereby serving as a dispersant that disperses the semiconductor quantum dots in the solvent. Examples of such ligands include ligands having at least 6 or more carbon atoms in the main chain, and preferably ligands having 10 or more carbon atoms in the main chain. The ligand may be either a saturated compound or an unsaturated compound. Specific examples include decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, oleylamine, stearylamine, 1-aminodecane, dodecylamine, aniline, dodecanethiol, 1,2-hexadecanethiol, tributylphosphine, trihexylphosphine, trioctylphosphine, tributylphosphine oxide, trioctylphosphine oxide, and cetrimonium bromide.

[0068] The content of the ligand in the dispersion is preferably 0.2 mol / L to 3.0 mol / L, and more preferably 0.2 mol / L to 0.5 mol / L.

[0069] The solvent contained in the dispersion is not particularly limited, but is preferably a solvent that hardly dissolves the semiconductor quantum dots and easily dissolves the ligands. Organic solvents are preferred. Specific examples include alkanes (n-hexane, n-octane, etc.), alkenes (octadecene, etc.), benzene, toluene, etc. The solvent contained in the dispersion of the present invention may be a single solvent or a mixed solvent of two or more solvents.

[0070] The content of the solvent in the dispersion is preferably from 50 to 99% by mass, more preferably from 70 to 99% by mass, and even more preferably from 90 to 98% by mass.

[0071] There are no particular limitations on the shape, structure, size, etc. of the substrate to which the dispersion is applied, and these can be appropriately selected depending on the purpose. The substrate structure may be a single-layer structure or a multilayer structure. For example, the substrate may be made of an inorganic material such as silicon, glass, or YSZ (Yttrium-Stabilized Zirconia), a resin, a resin composite material, or the like. Furthermore, electrodes, insulating films, etc. may be formed on the substrate. In this case, the dispersion is also applied to the electrodes and insulating films on the substrate.

[0072] The method for applying the dispersion onto the substrate is not particularly limited, and examples thereof include spin coating, dipping, inkjet printing, dispenser printing, screen printing, letterpress printing, intaglio printing, and spray coating.

[0073] The thickness of the film of the semiconductor quantum dot aggregate formed by applying the dispersion is preferably 3 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more, and the upper limit is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less.

[0074] After forming a film of semiconductor quantum dot aggregates, a step of applying a ligand solution to the film may be performed. By performing this step, the ligands coordinated to the semiconductor quantum dots can be replaced with ligands contained in the ligand solution, or the ligands contained in the ligand solution can be coordinated to the semiconductor quantum dots, thereby suppressing the occurrence of surface defects of the semiconductor quantum dots. The step of applying the dispersion liquid and the step of applying the ligand solution may be alternately repeated multiple times.

[0075] Examples of the ligand contained in the ligand solution include the ligands described in the section on the semiconductor film above. The ligand contained in the ligand solution may be the same as or different from the ligand contained in the dispersion. The ligand solution may contain only one type of ligand, or may contain two or more types. Furthermore, two or more types of ligand solutions may be used in the step of applying the ligand solution.

[0076] The solvent contained in the ligand solution is preferably selected appropriately depending on the type of ligand contained in each ligand solution, and is preferably a solvent that easily dissolves each ligand. Furthermore, the solvent contained in the ligand solution is preferably an organic solvent with a high dielectric constant. Specific examples include ethanol, acetone, methanol, acetonitrile, dimethylformamide, dimethyl sulfoxide, butanol, propanol, etc. Furthermore, the solvent contained in the ligand solution is preferably a solvent that is unlikely to remain in the semiconductor film to be formed. From the viewpoint of ease of drying and ease of removal by washing, low-boiling alcohols, ketones, and nitriles are preferred, and methanol, ethanol, acetone, or acetonitrile are more preferred. The solvent contained in the ligand solution is preferably one that is immiscible with the solvent contained in the quantum dot dispersion. As a preferred solvent combination, when the solvent contained in the quantum dot dispersion is an alkane such as hexane or octane, or toluene, the solvent contained in the ligand solution is preferably a polar solvent such as methanol or acetone.

[0077] After the step of applying the ligand solution, a step of rinsing the film by contacting it with a rinse liquid (rinsing step) may be performed. By performing the rinsing step, excess ligands contained in the semiconductor film and ligands detached from the semiconductor quantum dots can be removed. The rinsing step may also be performed multiple times using two or more rinse liquids with different polarities (dielectric constants). For example, it is preferable to first rinse using a rinse liquid with a high dielectric constant (also referred to as a first rinse liquid), and then rinse using a rinse liquid with a lower dielectric constant than the first rinse liquid (also referred to as a second rinse liquid). The dielectric constant of the first rinse liquid is preferably 15 to 50, more preferably 20 to 45, and even more preferably 25 to 40. The dielectric constant of the second rinse liquid is preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5.

[0078] The method for producing a semiconductor film may include a drying step. By performing the drying step, residual solvent in the semiconductor film can be removed. The drying time is preferably 1 to 100 hours, more preferably 1 to 50 hours, and even more preferably 5 to 30 hours. The drying temperature is preferably 10 to 100°C, more preferably 20 to 90°C, and even more preferably 20 to 60°C. The drying step may be performed in an oxygen-containing atmosphere or a nitrogen atmosphere. The amount of residual solvent in the semiconductor film is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total amount of the semiconductor film. The lower limit can be, for example, 0.0001% by mass. The semiconductor film may contain water, which is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total amount of the semiconductor film. The lower limit can be, for example, 0.0001% by mass. During the semiconductor film production process, the semiconductor quantum dots and ligands may be oxidized.

[0079] <Photodetector> The photodetector of the present invention includes the semiconductor film of the present invention described above. Preferably, the photodetector includes the semiconductor film of the present invention as a photoelectric conversion layer.

[0080] The types of photodetector elements include photoconductor-type photodetectors and photodiode-type photodetectors, of which photodiode-type photodetectors are preferred because they tend to provide a high signal-to-noise ratio (SN ratio).

[0081] Since the semiconductor film of the present invention has excellent sensitivity to light having a wavelength in the infrared region, a photodetector using this semiconductor film as a photoelectric conversion layer is preferably used as a photodetector for detecting light having a wavelength in the infrared region, i.e., the photodetector is preferably used as an infrared light detecting element.

[0082] The infrared wavelength light is preferably light having a wavelength of more than 700 nm, more preferably light having a wavelength of 800 nm or more, and even more preferably light having a wavelength of 900 nm or more. The infrared wavelength light is preferably light having a wavelength of 3000 nm or less, more preferably light having a wavelength of 2000 nm or less, and even more preferably light having a wavelength of 1600 nm or less.

[0083] The photodetector may be a photodetector that simultaneously detects light with a wavelength in the infrared region and light with a wavelength in the visible region (preferably light with a wavelength in the range of 400 to 700 nm).

[0084] FIG. 1 shows one embodiment of a photodetector element. FIG. 1 is a diagram illustrating one embodiment of a photodiode-type photodetector element. Note that arrows in the figure indicate incident light on the photodetector element. The photodetector element 1 shown in FIG. 1 includes a second electrode 12, a first electrode 11 provided opposite the second electrode 12, a photoelectric conversion layer 13 provided between the second electrode 12 and the first electrode 11, an electron transport layer 21 provided between the first electrode 11 and the photoelectric conversion layer 13, and a hole transport layer 22 provided between the second electrode 12 and the photoelectric conversion layer 13. The photodetector element 1 shown in FIG. 1 is used so that light is incident from above the first electrode 11. Note that, although not shown, a transparent substrate may be disposed on the light-incident surface of the first electrode 11. Examples of transparent substrates include glass substrates, resin substrates, and ceramic substrates.

[0085] (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), and fluorine-doped tin oxide (FTO).

[0086] The film thickness of the first electrode 11 is not particularly limited, but is preferably 0.01 to 100 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 a cross section of the photodetector element 1 using a scanning electron microscope (SEM) or the like.

[0087] (Electron Transport Layer) The electron transport layer 21 is a layer having a function of transporting electrons generated in the photoelectric conversion layer 13 to the electrode. The electron transport layer is also called a hole blocking layer. The electron transport layer is formed of an electron transport material that can exhibit this function.

[0088] Examples of electron transport materials include fullerene compounds such as [6,6]-phenyl-C61-butylic acid methyl ester (PC61BM), perylene compounds such as perylene tetracarboxydiimide, tetracyanoquinodimethane, titanium oxide, 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 be in the form of particles. The electron transport material is preferably zinc oxide. Furthermore, from the viewpoints of reducing residual organic components and increasing the contact area with the photoelectric conversion layer, the zinc oxide is preferably in the form of particles (zinc oxide particles).

[0089] The zinc oxide may be zinc oxide doped with metal atoms other than Zn. Hereinafter, zinc oxide doped with metal atoms other than Zn will also be referred to as doped zinc oxide.

[0090] The metal atoms other than Zn in the doped zinc oxide are preferably monovalent to trivalent metal atoms, more preferably at least one selected from Li, Mg, Al, and Ga, further preferably Li, Mg, Al, or Ga, and particularly preferably Li or Mg.

[0091] In the doped zinc oxide, the ratio of metal atoms other than Zn to the total of Zn and metal atoms other than Zn is preferably 1 atomic % or more, more preferably 2 atomic % or more, and even more preferably 4 atomic % or more. From the viewpoint of suppressing an increase in crystal defects, the upper limit is preferably 20 atomic % or less, more preferably 15 atomic % or less, and even more preferably 12 atomic % or less. The ratio of metal atoms other than Zn in the doped zinc oxide can be measured by a high-frequency inductively coupled plasma (ICP) method.

[0092] The average particle size of the zinc oxide particles is preferably 2 to 30 nm. 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 having a large contact area with the photoelectric conversion layer and high flatness is likely to be obtained. In this specification, the average particle size of the zinc oxide particles is the average value of the particle sizes of 10 arbitrarily selected particles. The particle size of the zinc oxide particles can be measured using a transmission electron microscope.

[0093] The electron transport layer may be a single layer film or a laminated film of two or more layers. 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. The thickness of the electron transport layer is preferably 0.05 to 10 times, more preferably 0.1 to 5 times, and even more preferably 0.2 to 2 times the thickness of the photoelectric conversion layer 13.

[0094] The electron transport layer may be subjected to ultraviolet ozone treatment. In particular, when the electron transport layer is a layer made of nanoparticles, ultraviolet ozone treatment is desirable. By performing ultraviolet ozone treatment, the wettability of the quantum dot dispersion liquid to the electron transport layer can be improved, and residual organic matter in the electron transport layer can be decomposed or removed, resulting in high device performance. The wavelength of the ultraviolet light to be irradiated can be selected between 100 and 400 nm. In particular, because the above-mentioned effects can be easily obtained and excessive damage to the film can be avoided, it is preferable for the peak intensity to be between 200 and 300 nm, and more preferably between 240 and 270 nm. There are no particular restrictions on the ultraviolet light irradiation intensity, but because the above-mentioned effects can be easily obtained and excessive damage to the film can be avoided, it is preferable for the peak intensity to be between 1 and 100 mW / cm. ２ is preferably 10 to 50 mW / cm ２ The treatment time is not particularly limited, but for the same reason, it is preferably 1 to 60 minutes, more preferably 1 to 20 minutes, and even more preferably 3 to 15 minutes.

[0095] (Photoelectric Conversion Layer) The photoelectric conversion layer 13 is composed of the semiconductor film of the present invention described above. The thickness of the photoelectric conversion layer 13 is preferably 10 to 1000 nm. The lower limit of the thickness is preferably 20 nm or more, and more preferably 30 nm or more. The upper limit of the thickness is preferably 600 nm or less, more preferably 550 nm or less, even more preferably 500 nm or less, and particularly preferably 450 nm or less. The refractive index of the photoelectric conversion layer 13 for light of the target wavelength to be detected by the photodetector element can be 1.5 to 5.0.

[0096] (Hole Transport Layer) The hole transport layer 22 is a layer having a function of transporting holes generated in the photoelectric conversion layer 13 to the electrode. The hole transport layer is also called an electron blocking layer.

[0097] The hole transport layer 22 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) and thieno[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-1)carbonyl]thieno[3,4-b]thiophenediyl})), poly(3-hexylthiophene-2,5-diyl), poly(3-n-octyl oxythiophene), poly(9,9'-dioctyl-fluorene-co-bithiophene), poly(3,3'''-didodecyl-quaterthiophene), poly(3,6-dioctylthieno[3,2-b]thiophene), poly(2,5-bis(3-decylthiophen-2-yl)thieno[3,2-b]thiophene), poly(3,4-didecylthiophene-co-thieno[3,2-b]thiophene), poly(3,6-dioctylthieno[3,2-b]thiophene-co-thieno[3,2-b]thiophene), poly(3,6-dioctylthieno[3,2-b]thiophene-co-thiophene), poly(3,6-dioctylthieno[3,2-b]thiophene-co-bithiophene), PC71BM ([6,6]-phenyl-C71-methyl butyrate). Alternatively, organic hole transport materials such as those described in paragraphs 0209 to 0212 of JP-A-2001-291534 can be used. Quantum dots can also be used as the hole transport material. Examples of quantum dot materials that constitute quantum dots include nanoparticles (particles with a size of 0.5 nm or more and less than 100 nm) of common semiconductor crystals (a) Group IV semiconductors, b) Group IV-IV, III-V, or II-VI compound semiconductors, and c) compound semiconductors formed from a combination of three or more of Group II, III, IV, V, and VI elements).Specifically, PbS, PbSe, PbSeS, InN, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, and Ag. ２ S, Ag ２ Se, Ag ２ Examples of such semiconductor materials include Te, SnS, SnSe, SnTe, Si, InP, etc. Ligands may be coordinated to the surface of the quantum dots.

[0098] The thickness of the hole transport layer 22 is preferably 5 to 100 nm. The lower limit is preferably 10 nm or more. The upper limit is preferably 50 nm or less, and more preferably 30 nm or less.

[0099] (Second Electrode) The second electrode 12 is preferably composed of a metal 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. By using such a metal material for the second electrode 12, a photodetector element with high external quantum efficiency and reduced dark current can be obtained. The second electrode 12 can also be made of the above-mentioned conductive metal oxides, carbon materials, conductive polymers, and the like. The carbon material may be any conductive material, such as fullerene, carbon nanotube, graphite, or graphene.

[0100] The work function of the second electrode 12 is preferably 4.6 eV or more, more preferably 4.8 to 5.7 eV, and even more preferably 4.9 to 5.3 eV, for the reasons that this enhances the electron blocking property of the hole transport layer and makes it easy to collect holes generated in the device.

[0101] The film thickness of the second electrode 12 is not particularly limited, but is preferably 0.01 to 100 μm, more preferably 0.01 to 10 μm, and even more preferably 0.01 to 1 μm.

[0102] (Charge Extraction Layer) Although not shown, the photodetector of the present invention may have a charge extraction layer between the second electrode 12 and the hole transport layer 22. By having the charge extraction layer, high external quantum efficiency can be obtained at a low applied voltage.

[0103] Materials for forming the charge extraction layer include metal oxides and organic semiconductors, with metal oxides being preferred. 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. Organic semiconductors include polythiophene compounds, with the materials mentioned above being specific examples of polythiophene compounds. The charge extraction layer may be a single-layer film or a laminated film of two or more layers.

[0104] The thickness of the charge extraction layer is preferably 1 to 100 nm, with the lower limit being preferably 5 nm or more and the upper limit being preferably 50 nm or less.

[0105] (Blocking Layer) Although not shown, the photodetector element may have a blocking layer between the first electrode 11 and the electron transport layer 21. The blocking layer 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 oxide, magnesium oxide, aluminum oxide, calcium carbonate, cesium carbonate, polyvinyl alcohol, polyurethane, titanium oxide, tin oxide, zinc oxide, niobium oxide, and tungsten oxide. The blocking layer may be a single-layer film or a laminated film of two or more layers. The film thickness of the blocking layer is preferably 5 to 100 nm. The lower limit is preferably 10 nm or more. The upper limit is preferably 50 nm or less, and more preferably 30 nm or less.

[0106] In the photodetector element, the wavelength λ of the light to be detected by the photodetector element and the optical path length L of the light of the wavelength λ from the surface of the second electrode 12 on the photoelectric conversion layer 13 side to the surface of the photoelectric conversion layer 13 on the first electrode 11 side are λ and preferably satisfy the relationship of the following formula (1-1), and more preferably satisfy the relationship of the following formula (1-2): λWhen these relationships are satisfied, the phases of the light incident from the first electrode 11 side (incident light) and the light reflected from the surface of the second electrode 12 (reflected light) can be aligned in the photoelectric conversion layer 13, and as a result, the light is reinforced by the optical interference effect, thereby achieving a higher external quantum efficiency.

[0107] 0.05+m / 2≦L λ / λ≦0.35+m / 2 ... (1-1) 0.10+m / 2≦L λ / λ≦0.30+m / 2 ... (1-2)

[0108] In the above formula, λ is the wavelength of the light to be detected by the light detection element, and L λ is the optical path length of light of wavelength λ from the surface of the second electrode 12 on the photoelectric conversion layer 13 side to the surface of the photoelectric conversion layer 13 on the first electrode 11 side, and m is an integer of 0 or more.

[0109] m is preferably an integer of 0 to 4, more preferably an integer of 0 to 3, and even more preferably an integer of 0 to 2. According to this embodiment, the transport properties of charges such as holes and electrons are good, and the external quantum efficiency of the photodetector can be further increased.

[0110] Here, the optical path length means the product of the physical thickness of the material through which light passes and the refractive index. Taking the photoelectric conversion layer 13 as an example, the thickness of the photoelectric conversion layer is d １ , the wavelength λ of the photoelectric conversion layer １ The refractive index of the light is N １ When the wavelength λ transmitted through the photoelectric conversion layer 13 is １ The optical path length of the light is N １ ×d １ When the photoelectric conversion layer 13 or the hole transport layer 22 is composed of a laminated film of two or more layers, or when an intermediate layer is present between the hole transport layer 22 and the second electrode 12, the integrated value of the optical path lengths of the respective layers is the above-mentioned optical path length L λ is.

[0111] <Image Sensor> The image sensor of the present invention includes the photodetector element of the present invention described above. Since the photodetector element of the present invention has excellent sensitivity to light with wavelengths in the infrared region, this image sensor can be particularly preferably used as an infrared sensor. Furthermore, the image sensor can be preferably used to sense light with a wavelength of 900 to 3000 nm, more preferably used to sense light with a wavelength of 900 to 2000 nm, and even more preferably used to sense light with a wavelength of 900 to 1600 nm.

[0112] The configuration of the image sensor is not particularly limited as long as it has a photodetector element and functions as an image sensor. Examples of the photodetector element include those described above.

[0113] The image sensor may include an infrared-transmitting filter layer, which preferably has low transmittance for light in the visible wavelength range, and more preferably has 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.

[0114] The infrared transmission filter layer may be formed of a resin film containing a colorant. Examples of the colorant include chromatic colorants such as red, green, blue, yellow, purple, and orange, as well as black colorants. The colorant contained in the infrared transmission filter layer preferably comprises a combination of two or more chromatic colorants to form a black color, or a black colorant. Examples of combinations of chromatic colorants when a black color is formed by combining two or more chromatic colorants include the following (C1) to (C7): (C1) A configuration containing a red colorant and a blue colorant; (C2) A configuration containing a red colorant, a blue colorant, and a yellow colorant; (C3) A configuration containing a red colorant, a blue colorant, a yellow colorant, and a purple colorant; (C4) A configuration containing a red colorant, a blue colorant, a yellow colorant, a purple colorant, and a green colorant; and (C5) A configuration containing a red colorant, a blue colorant, a yellow colorant, and a green colorant. (C6) An embodiment containing a red color material, a blue color material, and a green color material. (C7) An embodiment containing a yellow color material and a purple color material.

[0115] The chromatic colorant may be a pigment or a dye. It may contain both a pigment and a dye. The black colorant is preferably an organic black colorant. Examples of organic black colorants include bisbenzofuranone compounds, azomethine compounds, perylene compounds, and azo compounds.

[0116] The infrared transmission filter layer may further contain an infrared absorber. By incorporating an infrared absorber into the infrared transmission filter layer, the wavelength of light to be transmitted can be shifted to a longer wavelength side. Examples of the infrared absorber include pyrrolopyrrole compounds, cyanine compounds, squarylium compounds, phthalocyanine compounds, naphthalocyanine compounds, quaterrylene compounds, merocyanine compounds, croconium compounds, oxonol compounds, iminium compounds, dithiol compounds, triarylmethane compounds, pyrromethene compounds, azomethine compounds, anthraquinone compounds, dibenzofuranone compounds, dithiolene metal complexes, metal oxides, and metal borides.

[0117] The spectral characteristics of the infrared transmission filter layer can be appropriately selected depending on the application of the image sensor. Examples include filter layers satisfying any one of the following spectral characteristics (1) to (5): (1): A filter layer in which the maximum 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 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 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 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 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 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 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 light transmittance 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 having a maximum light transmittance in the thickness direction of the film in the wavelength range of 400 to 1300 nm of 20% or less (preferably 15% or less, more preferably 10% or less), and a minimum light transmittance in the wavelength range of 1600 to 2000 nm of 70% or more (preferably 75% or more, more preferably 80% or more).Further, as the infrared transmission filter, films described in JP 2013-077009 A, JP 2014-130173 A, JP 2014-130338 A, WO 2015 / 166779 A, ​​WO 2016 / 178346 A, WO 2016 / 190162 A, WO 2018 / 016232 A, JP 2016-177079 A, ​​JP 2014-130332 A, and WO 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 one filter may be used.

[0118] The image sensor may include an infrared shielding filter for the purpose of improving various performances such as noise reduction, etc. Specific examples of the infrared shielding filter include the filters described in International Publication No. 2016 / 186050, International Publication No. 2016 / 035695, Japanese Patent No. 6248945, International Publication No. 2019 / 021767, Japanese Patent Laid-Open No. 2017-067963, and Japanese Patent No. 6506529.

[0119] The image sensor may include a dielectric multilayer film. Examples of the dielectric multilayer film include a multilayer film in which a high refractive index dielectric thin film (high refractive index material layer) and a low refractive index dielectric thin film (low refractive index material layer) are alternately stacked. The number of dielectric thin films stacked in the dielectric multilayer film is not particularly limited, but is preferably 2 to 100 layers, more preferably 4 to 60 layers, and even more preferably 6 to 40 layers. A material with a refractive index of 1.7 to 2.5 is preferred as a material used to form the high refractive index material layer. Specific examples include 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 O３ , SiO, Ta ２ O ５ , TiO ２ , TlCl, Y ２ O ３ , ZnSe, ZnS, ZrO ２ The material used to form the low refractive index material layer is preferably a material having a refractive index of 1.2 to 1.6. 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 and the like. The method for forming the dielectric multilayer film is not particularly limited, and examples thereof include vacuum deposition methods such as ion plating and ion beam, physical vapor deposition methods (PVD methods) such as sputtering, and chemical vapor deposition methods (CVD methods). The thickness of each of the high refractive index material layer and the low refractive index material layer is preferably 0.1λ to 0.5λ, where λ (nm) is the wavelength of the light to be blocked. Specific examples of the dielectric multilayer film that can be used include the films described in JP 2014-130344 A and JP 2018-010296 A.

[0120] 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 determined by dividing the wavelength showing the maximum transmittance by the center wavelength λ ｔ１ In this case, the central wavelength λ ｔ１ ±100 nm, and the central wavelength λ ｔ１ More preferably, the central wavelength λ ｔ１ It is more preferably ±50 nm.

[0121] 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 may have a plurality of transmission wavelength bands.

[0122] The image sensor may include a color separation filter layer. Examples of the color separation filter layer include a filter layer containing colored pixels. Examples of the colored pixels include red, green, blue, yellow, cyan, and magenta pixels. The color separation filter layer may include colored pixels of two or more colors, or may include only one color. The filter layer may be appropriately selected depending on the application and purpose. For example, the filter described in International Publication No. 2019 / 039172 may be used.

[0123] Furthermore, when the color separation layer includes color pixels of two or more colors, the color pixels of each color may be adjacent to each other, and a partition wall may be provided between each color pixel. The material of the partition wall is not particularly limited. Examples include organic materials such as siloxane resin and fluororesin, and inorganic particles such as silica particles. The partition wall may also be made of a metal such as tungsten or aluminum.

[0124] When the image sensor includes an infrared transmission filter layer and a color separation layer, it is preferable that the color separation layer is provided on a different 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 two-dimensionally. The two-dimensional arrangement of the infrared transmission filter layer and the color separation layer means that at least a portion of each layer exists on the same plane.

[0125] The image sensor may include an intermediate layer such as a planarization layer, a base layer, or an adhesion layer, an anti-reflection film, and a lens. The anti-reflection film may be, for example, a film made from a composition described in International Publication No. 2019 / 017280. The lens may be, for example, a structure described in International Publication No. 2018 / 092600.

[0126] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0127] [Preparation of Zinc Oxide Particle Dispersion] 1.5 mmol of zinc acetate dihydrate and 15 mL of dimethyl sulfoxide (DMSO) were weighed into a flask and stirred to prepare a zinc acetate solution. A TMACl solution was prepared by dissolving 4 mmol of tetramethylammonium chloride (TMACl) in 4 mL of methanol, and a KOH solution was prepared by dissolving 4 mmol of potassium hydroxide (KOH) in 4 mL of methanol. While vigorously stirring the TMACl solution, the KOH solution was slowly added. After stirring for 30 minutes, the insoluble components were removed through a 0.45 μm filter to obtain a tetramethylammonium hydroxide (TMAH) solution. 6 mL of the TMAH solution was added dropwise to the zinc acetate solution in the flask at a rate of 6 mL / min. After holding for 1 hour, the reaction solution was recovered. An excess amount of acetone was added to the reaction solution, which was then centrifuged at 10,000 rpm for 10 minutes. The supernatant was removed, and the precipitate was dispersed in methanol. Thereafter, the mixture was precipitated again with acetone, and 5 mL of ethanol and 80 μL of aminoethanol were added, followed by ultrasonic dispersion to obtain a zinc oxide particle dispersion liquid with a concentration of non-doped zinc oxide particles of 30 mg / mL.

[0128] [Preparation of Quantum Dot Dispersion] (Quantum Dot Dispersion 1) In a glove box, 5 mmol of indium chloride was added to 50 mL of oleylamine, and the mixture was heated and stirred at 60°C to dissolve the indium chloride, preparing indium precursor solution A. In a glove box, 5 mmol of antimony chloride was added to 20 mL of oleylamine, and the mixture was heated and stirred at 60°C to dissolve the antimony chloride, preparing antimony precursor solution B. In a glove box, 100 mL of a tetrahydrofuran (THF) solution of lithium triethylborohydride (concentration of lithium triethylborohydride: 1.0 mol / L, manufactured by Aldrich) was mixed with 50 mL of dioctyl ether, and the THF was distilled off to prepare solution C, which was a dioctyl ether solution of lithium triethylborohydride (concentration of lithium triethylborohydride: approximately 2.0 mol / L). In a glove box, 16.5 mL of precursor solution A, 3 mL of precursor solution B, and 13.5 mL of oleylamine were added to a three-neck flask to obtain a mixed solution. The three-neck flask was then removed from the glove box, and after repeated evacuation and nitrogen purging, the mixture was switched to a nitrogen flow state. 2.9 mL of solution C was then poured into the mixed solution, and the temperature was raised to 260°C at a rate of 3°C / min. After the liquid temperature reached 260°C, the reaction solution was maintained for approximately 15 minutes and then cooled. The three-neck flask was then returned to the glove box, and 6 mL of oleic acid and 90 mL of toluene were added and stirred. This solution was centrifuged at approximately 8000 rpm, after which the precipitate was removed. 60 mL of acetonitrile was added to the supernatant and centrifuged again at 8000 rpm. 9 mL of toluene was added to the precipitate to obtain quantum dot dispersion 1, a dispersion of InSb quantum dots. A quantum dot thin film was prepared using the obtained quantum dot dispersion liquid 1, and the band gap was estimated to be about 0.99 eV from the wavelength at which an inflection point of absorption was observed in the absorption measurement of the quantum dot thin film.

[0129] (Quantum Dot Dispersion 2) 9 ml of acetonitrile was added to 9 ml of quantum dot dispersion 1, and the mixture was centrifuged. The supernatant was removed and the precipitate was recovered. Octane was added to the recovered precipitate to obtain quantum dot dispersion 2a with a concentration of 9 mg / ml. Separately, 0.38 ml of 3-mercaptopropionic acid (MPA) was added and dissolved in 5 ml of N,N-dimethylformamide (DMF) to produce MPA ligand-exchanged solution 1. 4 ml of MPA ligand-exchanged solution 1 and 4 ml of quantum dot dispersion 2a were added to a centrifuge tube and stirred for 2 minutes with a vortex mixer. The mixture was then allowed to stand to separate into an octane phase (upper layer) and a DMF phase (lower layer). The upper octane phase was removed, and then 8 ml of hexane was added and stirred for 2 minutes with a vortex mixer. The upper hexane phase was then removed again, and 8 ml of hexane was added and stirred for 2 minutes with a vortex mixer. The upper hexane layer was removed, and 3.2 ml of toluene and 11.2 ml of hexane were added and centrifuged. The supernatant was removed, and the precipitate was vacuum dried for 15 minutes and then redispersed in DMF to obtain quantum dot dispersion 2 (concentration 50 mg / ml) in which MPA was coordinated as a ligand to InSb quantum dots.

[0130] (Quantum Dot Dispersion 3) 9 ml of acetonitrile was added to 9 ml of Quantum Dot Dispersion 1, and after centrifugation, the supernatant was removed and the precipitate was collected. Octane was added to the collected precipitate to obtain Quantum Dot Dispersion 3a with a concentration of 9 mg / ml. Separately, 1 g of indium iodide (InI3) and 0.09 g of ammonium acetate were dissolved in 20 ml of N,N-dimethylformamide (DMF) to obtain InI ３ Ligand exchange solution 1 was prepared. ３6 ml of the ligand exchange solution 1 and 4 ml of the quantum dot dispersion solution 3a were added to a centrifuge tube, stirred for 2 minutes with a vortex mixer, and then allowed to stand to separate into an octane phase (upper layer) and a DMF phase (lower layer). After removing the upper octane phase, 6 ml of octane was added and stirred for 2 minutes with a vortex mixer. The upper octane phase was again removed, 6 ml of octane was added, and stirred for 2 minutes with a vortex mixer. The upper octane phase was removed, 12 ml of toluene was added, centrifuged, the supernatant was removed, and the precipitate was vacuum dried for 15 minutes. After redispersing in DMF, InSb quantum dots were treated with InI as a ligand. ３ Thus, quantum dot dispersion 3 (concentration: 50 mg / ml) in which the above was coordinated was obtained.

[0131] (Quantum dot dispersion liquid r1) Acetonitrile was added to the quantum dot dispersion liquid 1, and after centrifugation, the supernatant was removed and the precipitate was collected. Octane was added to the collected precipitate to obtain a quantum dot dispersion liquid r1a with a concentration of 50 mg / ml. Separately, 23.4 mg of nitrosonium tetrafluoroborate (NOBF) was dissolved in 10 ml of N,N-dimethylformamide (DMF). ４ ) and stirring to obtain NOBF ４ A solution was obtained. ４ 10 ml of the solution and 4 ml of quantum dot dispersion liquid r1a were added to a centrifuge tube, stirred with a vortex mixer for 1 minute, and then allowed to stand to separate into an octane phase (upper layer) and a DMF phase (lower layer). After removing the upper octane phase, 4 ml of hexane was added and stirred with a vortex mixer for 1 minute. The upper hexane phase was again removed, 4 ml of hexane was added, and stirred with a vortex mixer for 2 minutes. The upper hexane phase was removed, 30 ml of toluene was added, centrifuged, the supernatant was removed, and the precipitate was vacuum dried for 1 day. After that, quantum dot dispersion liquid r1 (concentration 50 mg / ml) was obtained by redispersing it in DMF.

[0132] [Fabrication of Semiconductor Film] (Example 1) All of the following steps were carried out in a nitrogen-filled glove box. Quantum dot dispersion 2 was dropped onto a gold-coated silicon substrate and spin-coated at 2500 rpm to form an InSb quantum dot assembly film (Step 1). Next, an InI iodide film prepared by adding 0.1 g of indium iodide to 20 mL of methanol and dissolving it was applied onto the InSb quantum dot assembly film. ３ After the ligand exchange liquid 2 was dropped, the film was left to stand for 20 seconds and then spun dry at 2500 rpm for 10 seconds (step 2). Next, acetonitrile was dropped onto the InSb quantum dot assembly film as a rinse liquid, and the film was spun dry at 2500 rpm for 20 seconds (step 3). Next, the film was heated at 120°C for 1 minute using a hot plate (step 4). Steps 1 to 4 were repeated again to impart InI ３ An InSb quantum dot assembly film (semiconductor film) in which MPA is coordinated was formed to a thickness of 100 nm.

[0133] (Example 2) In Example 1, InI ３ An InSb quantum dot assembly film (semiconductor film) having a thickness of 100 nm, in which MAI and MPA were coordinated to the InSb quantum dots, was formed in the same manner as in Example 1, except that a methylammonium iodide (MAI) ligand exchange liquid prepared by dissolving 0.16 g of MAI in 50 mL of methanol was used instead of ligand exchange liquid 2.

[0134] (Example 3) In Example 1, quantum dot dispersion liquid 3 was used instead of quantum dot dispersion liquid 2, and InI ３ InSb quantum dots were treated with InI in the same manner as in Example 1, except that an MPA ligand exchange solution prepared by mixing 20 μL of MPA in 50 mL of methanol was used instead of the ligand exchange solution 2. ３ An InSb quantum dot assembly film (semiconductor film) in which MPA is coordinated was formed to a thickness of 100 nm.

[0135] (Comparative Example 1) In Example 1, InI ３ Instead of the ligand exchange solution 2, sodium azide (NaN ３ ) 0.16 g of NaN３ The same method as in Example 1 was used except that a ligand exchange solution was used. ３ An InSb quantum dot assembly film (semiconductor film) in which MPA is coordinated was formed to a thickness of 100 nm.

[0136] Comparative Example 2 In Example 1, quantum dot dispersion liquid r1 was used instead of quantum dot dispersion liquid 2, and InI ３ Instead of the ligand exchange solution 2, add InI to 50 ml of methanol. ３ 0.05g of InI mixed with 10 μL of MPA ３ InSb quantum dots were treated with InI in the same manner as in Example 1, except that the MPA ligand exchange solution was used. ３ An InSb quantum dot assembly film (semiconductor film) in which MPA is coordinated was formed to a thickness of 100 nm.

[0137] [Method for measuring elemental composition ratio of semiconductor film] The elemental composition ratio of the semiconductor film was measured by X-ray photoelectron spectroscopy using an XPS (X-ray Photoelectron Spectroscopy) device under the following conditions. In the table below, the molar ratio of nitrogen element to In element is recorded in the N / In ratio column, and the molar ratio of nitrogen element to halogen element is recorded in the N / Halogen ratio column. X-ray source: Monochromated Al-K line (100 mmf, 25 W, 15 kV) Measurement area: 300 mm x 300 mm (area measurement) Pass energy: 46.95 eV Charge correction: Yes (electron gun and low-energy ion gun used together) Photoelectron take-off angle: 45°

[0138]

[0139] [Production of Photodetector] (Examples 11 to 13, Comparative Examples 11 and 12) An ITO (indium tin oxide) film (first electrode) having a thickness of approximately 100 nm was formed on quartz glass by sputtering. Next, a solution prepared by dissolving 1 g of zinc acetate dihydrate and 284 μL of ethanolamine in 10 mL of methoxyethanol was spin-coated onto the first electrode at 3000 rpm. This was then heated at 200°C for 30 minutes to form a zinc oxide film (electron transport layer) having a thickness of approximately 40 nm. Next, the zinc oxide particle dispersion described above was dropped onto the electron transport layer, followed by spin-coating at 2500 rpm and heating at 70°C for 30 minutes. This process was repeated twice to obtain a zinc oxide particle film having a thickness of approximately 160 nm. After forming the zinc oxide particle film, a UVO-CLEANER MODEL 144AX-100 manufactured by JElight was used, and the light was irradiated at 30 mW / cm ２ An ultraviolet ozone treatment was carried out for 5 minutes under the condition of ultraviolet ozone treatment (wavelength peak 254 nm). Next, an InSb quantum dot assembly film (semiconductor film) was formed to a thickness of 100 nm on the zinc oxide laminate according to the methods of Examples 1 to 3 and Comparative Examples 1 and 2 described above, to form a photoelectric conversion layer.

[0140] Next, a toluene solution (concentration: 10 mg / ml) of poly(3-hexylthiophene-2,5-diyl) (P3HT) was spin-coated onto the photoelectric conversion layer at 2000 rpm to form a hole transport layer.

[0141] Next, a 10 nm thick MoO film was deposited on the hole transport layer by vacuum deposition using a metal mask. ３ After the film was formed, a 100 nm thick Au film (second electrode) was formed to form three element portions, thereby manufacturing a photodiode-type light-detecting element.

[0142] [Performance Evaluation of Photodetector] The fabricated photodetector was evaluated for the dark current and external quantum efficiency (EQE) of the semiconductor film using a semiconductor parameter analyzer (C4156, manufactured by Agilent). First, the current-voltage characteristics (IV characteristics) were measured while sweeping the voltage from 0 V to −2 V in a state where no light was irradiated, and the dark current was evaluated. Here, the current value at −2 V was taken as the dark current value. Next, the photodetector was irradiated with 1400 nm monochrome light (irradiation dose 50 μW / cm２ ) was irradiated, the I-V characteristics were measured while sweeping the voltage from 0 V to -2 V. The photocurrent value was determined by subtracting the dark current value from the current value when -2 V was applied, and the external quantum efficiency (EQE) was calculated from this value. Note that the values ​​listed in the external quantum efficiency (EQE) and dark current columns in the table below are values ​​for the central element among the three element parts. Furthermore, for the in-plane uniformity of the external quantum efficiency (EQE), the external quantum efficiency of each of the three element parts was measured, and the difference between the highest and lowest external quantum efficiency values ​​was divided by the external quantum efficiency of the element with the median performance to calculate ΔEQE, and the in-plane uniformity of the external quantum efficiency was evaluated based on ΔEQE. A smaller ΔEQE value indicates better in-plane uniformity. ΔEQE (%) = (highest external quantum efficiency value - lowest external quantum efficiency value) / median external quantum efficiency × 100

[0143]

[0144] As shown in the table above, the photodetector element of the example had higher external quantum efficiency (EQE) and better in-plane uniformity of the external quantum efficiency (EQE) than the photodetector element of the comparative example.Furthermore, the dark current was also lower.

[0145] An image sensor having good visible-infrared imaging performance can be produced by using the photodetector element obtained in the above examples and an optical filter produced according to the methods described in WO 2016 / 186050 and WO 2016 / 190162 together with a known method.

[0146] 1: Photodetector element 11: First electrode 12: Second electrode 13: Photoelectric conversion layer 21: Electron transport layer 22: Hole transport layer

Claims

1. A semiconductor film comprising an aggregate of semiconductor quantum dots containing an In element and a Group 15 element, and ligands coordinated to the semiconductor quantum dots, wherein the Group 15 element contains an Sb element, the ligands contain a ligand containing a halogen element, and the semiconductor film contains a nitrogen element, with a molar ratio of the nitrogen element to the In element being 0.01 to 0.

10.

2. The semiconductor film according to claim 1, wherein the semiconductor film has a molar ratio of nitrogen element to halogen element of 0.01 to 0.

20.

3. The semiconductor film according to claim 1, wherein the molar ratio of nitrogen element to halogen element in said semiconductor film is 0.01 to 0.

10.

4. The semiconductor film according to any one of claims 1 to 3, wherein the molar ratio of Sb element to halogen element in the semiconductor film is 0.30 to 3.

20.

5. The semiconductor film according to any one of claims 1 to 3, wherein the ligand containing a halogen element is a ligand containing an iodine element.

6. The semiconductor film according to any one of claims 1 to 3, wherein the ligand includes a ligand containing a sulfur element.

7. The semiconductor film according to any one of claims 1 to 3, wherein the ligand containing a halogen element contains an In element.

8. The semiconductor film according to any one of claims 1 to 3, wherein the band gap of the semiconductor quantum dots is 1.0 eV or less.

9. A photodetector comprising the semiconductor film according to any one of claims 1 to 3.

10. An image sensor comprising the photodetector element of claim 9.

Images