Method for producing quantum dot

Abstract

This method for producing a quantum dot comprises: a step for adding an indium halide and an antimony halide to an amine compound and mixing to prepare a precursor solution; and a step for adding a reducing agent to the precursor solution and reacting indium halide and antimony halide in the presence of the reducing agent.

Description

Quantum dot manufacturing method

[0001] The present invention relates to a method for producing quantum dots.

[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 have therefore not become widely used.

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

[0006] Patent Document 1 discloses a method for producing quantum dots containing a group IIIA-VA compound, the method comprising the steps of: supplying a group VA element precursor containing a halide of a group VA element and a first ligand containing a phosphine compound or a first amine compound; and carrying out a reaction between the group VA element precursor and a group IIIA metal precursor in an organic reaction medium containing a second amine compound in the presence of a reducing agent.

[0007] U.S. Pat. No. 1,095,0427

[0008] In recent years, with the demand for improved performance of image sensors and the like, further improvements are being demanded in the properties required of the photodetector elements used therein. For example, one of the properties required of a photodetector element is a high external quantum efficiency for light of the target wavelength to be detected by the photodetector element. Increasing the external quantum efficiency of the photodetector element can improve the light detection accuracy of the photodetector element.

[0009] 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.

[0010] The present inventors have conducted further studies on a photodetector element using quantum dots containing indium and antimony in the photoelectric conversion layer, and have found that there is room for further improvement in these characteristics.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing quantum dots that can form a semiconductor film with high external quantum efficiency and reduced dark current.

[0012] The present invention provides the following:

[0013] <1> A method for producing quantum dots, comprising the steps of: preparing a precursor solution by adding an indium halide and an antimony halide to an amine compound and mixing them; and adding a reducing agent to the precursor solution and reacting the indium halide with the antimony halide in the presence of the reducing agent. <2> The method for producing quantum dots according to <1>, wherein the indium halide is indium chloride, and the antimony halide is antimony chloride. <3> The method for producing quantum dots according to <1> or <2>, wherein the amine compound is an amine compound having 12 to 20 carbon atoms. <4> The method for producing quantum dots according to any one of <1> to <3>, wherein the amine compound includes oleylamine. <5> The method for producing quantum dots according to any one of <1> to <4>, wherein the reducing agent is at least one selected from a boron hydride-based reducing agent, a silicon hydride-based reducing agent, an aluminum hydride-based reducing agent, a calcium hydride-based reducing agent, a hydrazine-based reducing agent, and hydrogen. <6> The method for producing quantum dots according to any one of <1> to <4>, wherein the reducing agent is at least one selected from the group consisting of lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, and lithium triethylborohydride. <7> The method for producing quantum dots according to any one of <1> to <4>, wherein the reducing agent is lithium triethylborohydride.

[0014] According to the present invention, it is possible to provide a method for manufacturing quantum dots that can form a semiconductor film with high external quantum efficiency and reduced dark current.

[0015] FIG. 2 illustrates an embodiment of a photodetector element.

[0016] 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).

[0017] <Method for producing quantum dots> The method for producing quantum dots of the present invention is characterized by comprising: a step of adding an indium halide and an antimony halide to an amine compound and mixing them to prepare a precursor solution; and a step of adding a reducing agent to the precursor solution and reacting the indium halide with the antimony halide in the presence of the reducing agent.

[0018] By using the quantum dots obtained by the present invention, it is possible to form a semiconductor film with high external quantum efficiency and reduced dark current. The detailed reasons for this effect are unclear, but it is presumed to be due to the following reasons. In the present invention, a precursor solution is produced by adding an indium halide and an antimony halide to an amine compound and mixing them, thereby achieving a good dispersion state. Therefore, it is presumed that adding a reducing agent to this precursor solution can efficiently promote the reaction between the indium halide and the antimony halide, thereby producing quantum dots with a uniform particle size. Therefore, it is presumed that the use of the obtained quantum dots makes it possible to form a semiconductor film with high external quantum efficiency and reduced dark current.

[0019] The quantum dots obtained by the present invention contain indium (In) and antimony (Sb). Examples of such quantum dots include quantum dots made of a compound semiconductor containing In and Sb. A compound semiconductor is a semiconductor composed of two or more elements. Therefore, in this specification, a "compound semiconductor containing In and Sb" refers to a compound semiconductor containing In and Sb as constituent elements of the compound semiconductor. In and Sb may also be included. Examples of additional elements include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), mercury (Hg), boron (B), aluminum (Al), gallium (Ga), phosphorus (P), arsenic (As), and bismuth (Bi), with Zn, Al, Ga, P, As, and Bi being preferred.

[0020] In the quantum dots, the ratio of the number of In atoms to the number of Sb atoms 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.

[0021] In this specification, the ratio of the number of In elements to the number of Sb elements in the quantum dots can be calculated by measuring the elemental composition ratio of the quantum dots by X-ray photoelectron spectroscopy. For example, the ratio can be calculated by forming a film using a quantum dot dispersion and measuring the elemental composition ratio of the quantum dots in this film by X-ray photoelectron spectroscopy.

[0022] Specific examples of quantum dots obtainable by the present invention include InSb and InSbAs.

[0023] The crystalline structure of the quantum dots obtained by the present invention is not particularly limited. Various crystalline structures can be obtained depending on the type and composition ratio of the elements constituting the quantum dots, but a cubic or hexagonal crystalline 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 crystalline structure of the quantum dots can be measured by X-ray diffraction or electron beam diffraction.

[0024] The quantum dots obtained by the present invention preferably have a band gap of 1.2 eV or less, more preferably 1.0 eV or less. The lower limit of the band gap of the quantum dots is not particularly limited, but is preferably 0.3 eV or more, more preferably 0.5 eV or more.

[0025] The average particle size of the quantum dots obtained by the present invention is preferably 3 to 20 nm. The upper limit of the average particle size of the quantum dots is preferably 15 nm or less, and more preferably 10 nm or less. In this specification, the average particle size of the quantum dots is the average value of the particle sizes of 10 arbitrarily selected quantum dots. The particle size of the quantum dots can be measured using a transmission electron microscope.

[0026] Each step of the method for producing quantum dots of the present invention will be described in more detail below.

[0027] <<Precursor Solution Preparation Step>> In the precursor solution preparation step, an indium halide and an antimony halide are added to an amine compound and mixed to prepare a precursor solution.

[0028] When preparing the precursor solution, the order of adding the indium halide and the antimony halide is not particularly limited. The indium halide may be added first, the antimony halide may be added first, or the indium halide and the antimony halide may be added simultaneously. From the viewpoint of productivity, it is preferable to add the indium halide first and then the antimony halide.

[0029] The amine compound is preferably an amine compound having 12 to 20 carbon atoms, and more preferably an amine compound having 14 to 20 carbon atoms.

[0030] The molecular weight of the amine compound is preferably 100 to 500. The upper limit is preferably 400 or less, more preferably 350 or less. The lower limit is preferably 150 or more, more preferably 200 or more.

[0031] The amine compound is preferably a compound represented by formula (Am-1). ａｍ１ -NH ２ ...(Am-1) where R ａｍ１ represents a hydrocarbon group having 12 to 20 carbon atoms. ａｍ１ is preferably a hydrocarbon group having 14 to 20 carbon atoms. The hydrocarbon group is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. An unsaturated aliphatic hydrocarbon group is preferred.

[0032] The amine compound is preferably in a liquid state at 25° C. In this specification, the phrase "in a liquid state at 25° C." means that the amine compound has a pour point at a temperature of 25° C. or lower and exhibits fluidity at 25° C.

[0033] Specific examples of the amine compound include oleylamine, 1-aminodecane, dodecylamine, and stearylamine.

[0034] The content of the amine compound in the precursor solution is preferably 0.1 to 500 mmol / L, and more preferably 0.5 mmol / L to 100 mmol / L.

[0035] The indium halide and the antimony compound are preferably in a solid state, more preferably in a powder state.

[0036] Specific examples of the indium halide include indium chloride, indium bromide, indium iodide, and indium fluoride, with indium chloride being preferred.

[0037] Specific examples of the antimony halide include antimony chloride, antimony bromide, antimony iodide, and antimony fluoride, with antimony chloride being preferred.

[0038] In the precursor solution, the ratio of indium halide to antimony halide is preferably 0.1 to 1.0 moles of antimony halide per mole of indium halide. The upper limit is preferably 0.75 moles or less, more preferably 0.6 moles or less. The lower limit is preferably 0.2 moles or more, more preferably 0.4 moles or more.

[0039] In preparing the precursor solution, other halides containing elements other than In and Sb may be further added, such as halides containing an element selected from Mg, Ca, Sr, Ba, Zn, Cd, Hg, B, Al, Ga, P, As, and Bi, and preferably halides containing an element selected from Zn, Al, Ga, P, As, and Bi.

[0040] When other halides are added, the amount of the other halides added is preferably 0.5 mol or less, and more preferably 0.2 mol or less, per mol of the indium halide.

[0041] <<Reaction Step>> In the reaction step, a reducing agent is added to the precursor solution obtained in the above step, and the indium halide and the antimony halide are reacted in the presence of the reducing agent.

[0042] Examples of the reducing agent include a boron hydride-based reducing agent, a silicon hydride-based reducing agent, an aluminum hydride-based reducing agent, a calcium hydride-based reducing agent, a hydrazine-based reducing agent, and hydrogen. A boron hydride-based reducing agent, a silicon hydride-based reducing agent, or an aluminum hydride-based reducing agent is preferred, and a boron hydride-based reducing agent is more preferred.

[0043] Examples of boron hydride reducing agents include diborane, borane-tetrahydrofuran complex, sodium borohydride, lithium borohydride, lithium tri(sec-butyl)borohydride, potassium tri(sec-butyl)borohydride, lithium triethylborohydride, and catecholborane.

[0044] Examples of silicon hydride reducing agents include triethylsilane, dimethylphenylsilane, and diphenylsilane.

[0045] Examples of aluminum hydride reducing agents include lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, diisobutylaluminum hydride, alkoxyaluminum hydride, and aluminum hydride.

[0046] Examples of calcium hydride reducing agents include calcium hydride.

[0047] Examples of the hydrazine-based reducing agent include hydrazine and its derivatives.

[0048] The reducing agent is preferably at least one selected from lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, and lithium triethylborohydride, and more preferably lithium triethylborohydride.

[0049] The amount of reducing agent added is preferably 1.3 to 4.5 moles per mole of the total of the indium halide and antimony halide. The upper limit is preferably 3.9 moles or less, more preferably 3.2 moles or less. The lower limit is preferably 1.6 moles or more, more preferably 1.9 moles or more.

[0050] The reaction temperature is preferably 260 to 300° C. The upper limit is preferably 295° C. or less, more preferably 290° C. or less. The lower limit is preferably 250° C. or more, more preferably 270° C. or more.

[0051] The reaction time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 15 minutes or more. There is no particular upper limit, but from the viewpoint of productivity, it is preferably 100 minutes or less, more preferably 90 minutes or less, and even more preferably 40 minutes or less.

[0052] The reaction may be carried out in air, vacuum, or an inert gas atmosphere. To prevent oxidation of the resulting quantum dots, the reaction is preferably carried out in an inert gas atmosphere. Examples of inert gases include nitrogen gas and argon gas.

[0053] After the reaction is completed, it is preferable to cool the reaction mixture to 40° C. or less. The cooling may be natural cooling or forced cooling.

[0054] <Dispersion> The quantum dots obtained by the present invention can be dispersed in a solvent and used as a dispersion.

[0055] The content of quantum dots in the dispersion is preferably 10 to 500 mg / mL. The lower limit is preferably 50 mg / mL or more, more preferably 80 mg / mL or more. The upper limit is preferably 300 mg / mL or less, more preferably 200 mg / mL or less.

[0056] The solvent used in the dispersion is not particularly limited, but is preferably a solvent that does not easily dissolve quantum dots. Organic solvents are preferred. Specific examples include alkanes (n-hexane, n-octane, etc.), alkenes (octadecene, etc.), benzene, toluene, etc. The dispersion may contain only one solvent, or a mixed solvent of two or more solvents.

[0057] 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.

[0058] The dispersion preferably contains a ligand. Examples of the ligand include a ligand that functions as a ligand that coordinates with the quantum dots and has a molecular structure that easily causes steric hindrance, thereby serving as a dispersant that disperses the quantum dots in the solvent. Examples of such ligands include ligands having 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.

[0059] The dispersion liquid may contain a ligand containing a halogen element as a ligand. The ligand is preferably an inorganic ligand containing a halogen element. The halogen element-containing ligand preferably contains an In element. Examples of the halogen element contained in the halogen element-containing ligand include a fluorine element, a chlorine element, a bromine element, and an iodine element, and iodine element is preferred.

[0060] 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.

[0061] 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 quantum dot. Furthermore, a portion of the ligand other than the halogen element may also be coordinated to the surface of the quantum dot. To give a specific example, in the case of indium iodide, indium iodide may be coordinated to the surface of the quantum dot, or iodine ions or indium ions may be coordinated to the surface of the quantum dot.

[0062] The dispersion liquid may contain, as a ligand, a multidentate organic ligand containing two or more coordination moieties. Examples of the coordination moieties contained in the organic ligand include a thiol group, an amino group, a hydroxyl group, a carboxyl group, a sulfo group, a phospho group, and a phosphonic acid group. The organic ligand preferably contains a thiol group.

[0063] The polydentate ligand may be a ligand represented by any one of formulas (A) to (C).

[0064] 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.

[0065] 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.

[0066] In formula (C), XＣ１ ~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.

[0067] 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:

[0068] X in formula (A) Ａ１ and X Ａ２ At least one of the groups is preferably a thiol group, and the other may be a thiol group or a group other than a thiol group.

[0069] X in formula (B) Ｂ１ and X Ｂ２ At least one of the groups is preferably a thiol group, and the other may be a thiol group or a group other than a thiol group.

[0070] X in formula (C) Ｃ１ ~X Ｃ３ At least one of the groups is preferably a thiol group, and the other may be a thiol group or a group other than a thiol group.

[0071] L Ａ１ , L Ｂ１ , L Ｂ２ , L Ｃ１ , L Ｃ２ and L Ｃ３The 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] <Method for Producing a Semiconductor Film> The quantum dots obtained by the present invention can be used to form a semiconductor film. The semiconductor film can be produced by applying the above-described dispersion onto a substrate.

[0082] 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.

[0083] 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.

[0084] The thickness of the film of the 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.

[0085] After forming a film of 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 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 quantum dots, thereby suppressing the occurrence of surface defects of the quantum dots. The step of applying the dispersion liquid and the step of applying the ligand solution may be alternately repeated multiple times.

[0086] Examples of the ligand contained in the ligand solution include the ligands described 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 of ligands. Furthermore, two or more types of ligand solutions may be used in the step of applying the ligand solution.

[0087] 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.

[0088] After the step of applying the ligand solution, a step of rinsing the film by contacting it with a rinse solution (rinsing step) may be performed. By performing the rinsing step, excess ligands contained in the semiconductor film and ligands detached from the quantum dots can be removed. The rinsing step may also be performed multiple times using two or more rinse solutions with different polarities (dielectric constants). For example, it is preferable to first rinse using a rinse solution with a high dielectric constant (also referred to as a first rinse solution), and then rinse using a rinse solution with a lower dielectric constant than the first rinse solution (also referred to as a second rinse solution). The dielectric constant of the first rinse solution is preferably 15 to 50, more preferably 20 to 45, and even more preferably 25 to 40. The dielectric constant of the second rinse solution is preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5.

[0089] 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, quantum dots and ligands may be oxidized.

[0090] <Photodetector> The quantum dots obtained by the present invention can be used in a photodetector, preferably in the photoelectric conversion layer of the photodetector.

[0091] The types of photodetector elements include photoconductor-type photodetectors and photodiode-type photodetectors, with photodiode-type photodetectors being preferred because they tend to provide a high signal-to-noise ratio (SN ratio).

[0092] The photoelectric conversion layer using the quantum dots obtained by the present invention has excellent sensitivity to light with wavelengths in the infrared region, and is therefore preferably used as a photodetector for detecting light with wavelengths in the infrared region. That is, the photodetector is preferably used as an infrared light detecting element.

[0093] 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.

[0094] The photodetector may be a photodetector that simultaneously detects light in the infrared wavelength range and light in the visible wavelength range (preferably light with a wavelength in the range of 400 to 700 nm).

[0095] 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.

[0096] (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).

[0097] 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.

[0098] (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.

[0099] 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).

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] (Photoelectric conversion layer) The photoelectric conversion layer 13 contains the quantum dots obtained by the present invention as described above. The photoelectric conversion layer can be formed by the method for manufacturing a semiconductor film as 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.

[0107] (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.

[0108] 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.

[0109] 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.

[0110] (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.

[0111] 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.

[0112] 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.

[0113] (Charge Extraction Layer) Although not shown, the photodetector element 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.

[0114] 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.

[0115] 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.

[0116] (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.

[0117] 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.

[0118] 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)

[0119] 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.

[0120] 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.

[0121] 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.

[0122] <Image Sensor> The quantum dots obtained by the present invention can be used in an image sensor. Preferably, they can be used in the photoelectric conversion layer of an image sensor. A photoelectric conversion layer using the quantum dots obtained by the present invention has excellent sensitivity to light with wavelengths in the infrared region, and therefore, 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] Example 1 In a glove box, 10 mmol of indium chloride and 5 mmol of antimony chloride were added to 100 mL of oleylamine and dissolved to prepare precursor solution 1. In the 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 reducing agent solution 1, which was a dioctyl ether solution of lithium triethylborohydride (concentration of lithium triethylborohydride: approximately 2.0 mol / L). In the glove box, 30 mL of precursor solution 1 was added to a three-neck flask. With nitrogen flowing through the three-neck flask, 4.0 mL of reducing agent solution 1 was injected and the temperature was raised to 290°C at a rate of 3°C / min. After the liquid temperature reached 290°C, the reaction solution was cooled by holding the temperature for 20 minutes. The three-neck flask was placed back into the glove box, and 90 mL of toluene and 6 mL of oleic acid were added and stirred. This solution was centrifuged at approximately 7,800 rpm, and the precipitate was removed. 60 mL of acetonitrile was added to the supernatant, and the mixture was centrifuged again at 7,800 rpm. Toluene was added to the precipitate, and an InSb quantum dot dispersion with a concentration of 40 mg / mL was obtained.

[0139] Example 2 In a glove box, 10 mmol of indium chloride and 6 mmol of antimony chloride were added to and dissolved in 100 mL of oleylamine to prepare precursor solution 2. The same procedure as in Example 1 was carried out except that precursor solution 2 was used instead of precursor solution 1, thereby obtaining an InSb quantum dot dispersion liquid with a concentration of 40 mg / mL.

[0140] Example 3 The same procedure as in Example 1 was carried out, except that 1.4 mL of a toluene solution (approximately 70%) of sodium bis(2-methoxyethoxy)aluminum hydride was used instead of the reducing agent solution 1 in Example 1, to obtain an InSb quantum dot dispersion liquid with a concentration of 40 mg / mL.

[0141] Comparative Example 1 In a glove box, 10 mmol of indium chloride was added to 100 mL of oleylamine and stirred to dissolve the indium chloride, preparing indium precursor solution A. In a glove box, 5 mmol of antimony chloride was added to 100 mL of oleylamine and stirred 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 (reducing agent), which was a dioctyl ether solution of lithium triethylborohydride (concentration of lithium triethylborohydride: approximately 2.0 mol / L). In a glove box, 15 mL of precursor solution A and 15 mL of precursor solution B 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 flask was placed under a nitrogen flow. 4.0 mL of solution C was then poured into the mixed solution, and the temperature was raised to 290°C at a rate of 3°C / min. After the liquid temperature reached 290°C, the reaction solution was cooled by holding the temperature for 20 minutes. The three-neck flask was then returned to the glove box, and 90 mL of toluene and 6 mL of oleic acid were added and stirred. This solution was centrifuged at approximately 7,800 rpm, after which the precipitate was removed. 60 mL of acetonitrile was added to the supernatant, and the mixture was centrifuged again at 7,800 rpm. Toluene was added to the precipitate, yielding an InSb quantum dot dispersion with a concentration of 40 mg / mL.

[0142] [Production of Photodetector] A zinc oxide film having a thickness of 120 nm was formed by sputtering on a quartz glass substrate with a fluorine-doped tin oxide film.

[0143] Next, an InSb quantum dot assembly film (semiconductor film) was formed on the zinc oxide film to a thickness of 100 nm according to the method described below, to form a photoelectric conversion layer.

[0144] 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.

[0145] 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.

[0146] (Method of Forming a Photoelectric Conversion Layer in a Photodetector) An InSb quantum dot dispersion liquid shown in the table below was dropped onto a zinc oxide film and spin-coated at 2500 rpm to form an InSb quantum dot assembly film (Step 1). Next, a mercaptopropionic acid solution (concentration: 0.01 v / v%) was dropped onto the InSb quantum dot assembly film, which was then left to stand for 20 seconds and spin-dried at 2500 rpm for 10 seconds (Step 2). Next, acetonitrile was dropped onto the InSb quantum dot assembly film as a rinse, which was then spin-dried at 2500 rpm for 20 seconds. Next, octane was dropped onto the InSb quantum dot assembly film as a rinse, which was then spin-dried at 2500 rpm for 20 seconds, thereby exchanging the ligands coordinated to the InSb quantum dots from oleic acid and oleylamine to mercaptopropionic acid (Step 3). The operation of steps 1 to 3 as one cycle was repeated five times to form a 100 nm thick InSb quantum dot assembly film (semiconductor film) in which the ligands had been exchanged with mercaptopropionic acid, thereby forming a photoelectric conversion layer.

[0147] [Performance Evaluation of Photodetector] The fabricated photodetector was evaluated for dark current and external quantum efficiency 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 1300 nm monochrome light (irradiation dose 50 μW / cm ２) 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 was calculated from this value. The values ​​listed in the external quantum efficiency and dark current columns in the table below are the values ​​for the central element out of the three element parts.

[0148]

[0149] As shown in the above table, the photodetector element of the example had a higher external quantum efficiency and a lower dark current than the photodetector element of the comparative example.

[0150] 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.

[0151] 1: Photodetector element 11: First electrode 12: Second electrode 13: Photoelectric conversion layer 21: Electron transport layer 22: Hole transport layer

Claims

1. A method for producing quantum dots, comprising: a step of adding an indium halide and an antimony halide to an amine compound and mixing them to prepare a precursor solution; and a step of adding a reducing agent to the precursor solution and reacting the indium halide with the antimony halide in the presence of the reducing agent.

2. The method for producing quantum dots according to claim 1, wherein the indium halide is indium chloride, and the antimony halide is antimony chloride.

3. The method for producing quantum dots according to claim 1 or 2, wherein the amine compound is an amine compound having 12 to 20 carbon atoms.

4. The method for producing quantum dots according to claim 1 or 2, wherein the amine compound includes oleylamine.

5. The method for producing quantum dots described in claim 1 or 2, wherein the reducing agent is at least one selected from the group consisting of boron hydride-based reducing agents, silicon hydride-based reducing agents, aluminum hydride-based reducing agents, calcium hydride-based reducing agents, hydrazine-based reducing agents, and hydrogen.

6. The method for producing quantum dots according to claim 1 or 2, wherein the reducing agent is at least one selected from the group consisting of lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, and lithium triethylborohydride.

7. The method for producing quantum dots according to claim 1 or 2, wherein the reducing agent is lithium triethylborohydride.

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