Method for producing quantum dots

Abstract

To provide a method for producing quantum dots having a small variation in particle size.SOLUTION: A method for producing quantum dots, the method comprising: mixing a first precursor solution containing an indium halide with a second precursor solution containing an antimony halide and an ether compound to prepare a mixed solution; and adding a reducing agent to the mixed solution to react the indium halide with the antimony halide in the presence of the reducing agent.SELECTED DRAWING: None

Description

[Technical Field]

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

[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 light detection elements for image sensors, etc. However, silicon photodiodes have low sensitivity in the infrared region with wavelengths above 900 nm.

[0004] InGaAs-based semiconductor materials, known as near-infrared light receiving elements, have not been widely adopted due to the issue that they require very costly processes, such as epitaxial growth and substrate bonding processes, to achieve high quantum efficiency.

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

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

[0007] [Patent Document 1] U.S. Patent No. 10,950,427 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the investigations of the present inventors, it has been found that when quantum dots are produced by the method disclosed in Patent Document 1, there is a large variation in particle size.

[0009] Therefore, an object of the present invention is to provide a method for producing quantum dots with small variations in particle size. [Means for solving the problem]

[0010] The present invention provides the following: <1> mixing a first precursor solution containing an indium halide with a second precursor solution containing an antimony halide and an ether compound to prepare a mixed solution; adding a reducing agent to the mixed solution and reacting the indium halide with the antimony halide in the presence of the reducing agent; A method for producing quantum dots, comprising: <2> The antimony halide is antimony chloride. <1> 10. A method for producing quantum dots according to claim 9. <3> the first precursor solution contains an indium halide and an amine compound; <1> 10. A method for producing quantum dots according to claim 9. <4> The amine compound includes oleylamine. <3> 10. A method for producing quantum dots according to claim 9. <5> The ether compound is a compound having 12 to 20 carbon atoms. <1> ~ <4> 1. A method for producing quantum dots according to any one of the preceding claims. <6> The ether compound is a liquid at 25°C. <1> ~ <5> 1. A method for producing quantum dots according to any one of the preceding claims. <7> The boiling point of the ether compound is 280°C or higher. <1> ~ <6> 1. A method for producing quantum dots according to any one of the preceding claims. [Effects of the Invention]

[0011] According to the present invention, quantum dots with small variations in particle size can be produced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 illustrates an embodiment of a photodetector element. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In the description of groups (atomic groups) in this specification, when a notation does not specify whether they are substituted or unsubstituted, it encompasses both unsubstituted groups (atomic groups) and substituted groups (atomic groups). For example, the term "alkyl group" encompasses not only alkyl groups without a substituent (unsubstituted alkyl groups) but also alkyl groups with a substituent (substituted alkyl groups).

[0014] <Quantum dot manufacturing method> The method for producing quantum dots of the present invention includes the steps of: a step of preparing a mixed solution by mixing a first precursor solution containing an indium halide with a second precursor solution containing an antimony halide and an ether compound (mixed solution preparation step); a step of adding a reducing agent to the mixed solution and reacting the indium halide with the antimony halide in the presence of the reducing agent (reaction step); The present invention is characterized in that it includes:

[0015] According to the present invention, quantum dots with small particle size variations can be produced. In the present invention, a second precursor solution containing an antimony halide and an ether compound is used. Antimony halide has good solubility in ether compounds, and it is presumed that the antimony halide is uniformly present in the second precursor solution. Therefore, by mixing a first precursor solution containing an indium halide with the second precursor solution and then reacting the indium halide with the antimony halide in the presence of a reducing agent, it is presumed that the reaction between the indium halide and the antimony halide can proceed uniformly, and quantum dots with small particle size variations can be produced.

[0016] The quantum dots obtained by the present invention contain indium (In) and antimony (Sb). Examples of the 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. The compound semiconductor may further contain In and Sb. 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.

[0017] 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, and the upper limit is preferably 3.0 or less.

[0018] 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, a film is formed using a dispersion of the quantum dots, and the elemental composition ratio of the quantum dots in this film is measured by X-ray photoelectron spectroscopy.

[0019] Specific examples of quantum dots obtainable by the present invention include InSb and InSbAs.

[0020] 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 that make up the quantum dots. However, 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 diffraction.

[0021] 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.

[0022] 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.

[0023] The quantum dots obtained by the present invention have small variations in particle size, and therefore, by using the quantum dots obtained by the present invention, it is possible to manufacture a photodetector element with suppressed dark current.

[0024] Each step of the method for producing quantum dots of the present invention will be described in more detail below.

[0025] <<Mixture preparation process>> In the mixed solution preparation step, a first precursor solution containing an indium halide is mixed with a second precursor solution containing an antimony halide and an ether compound to prepare a mixed solution.

[0026] The first precursor solution and the second precursor solution are preferably mixed in a ratio of 0.25 to 1.0 moles of antimony halide per mole of indium halide. The upper limit is preferably 0.9 moles or less, more preferably 0.7 moles or less. The lower limit is preferably 0.3 moles or more, more preferably 0.35 moles or more.

[0027] (First precursor solution) The first precursor solution contains an indium halide. The first precursor solution preferably contains an indium halide and an amine compound. This first precursor solution can be prepared by mixing the indium halide and the amine compound. The indium halide and the amine compound are preferably mixed at a temperature of 30 to 80°C.

[0028] Examples of indium halides include indium chloride, indium bromide, indium iodide, and indium fluoride, with indium chloride being preferred.

[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). R am1 -NH2···(Am-1) In the formula, 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 a liquid at 25° C. In this specification, the phrase "liquid 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, with oleylamine being preferred.

[0034] The content of the indium halide in the first precursor solution is preferably 1 to 5000 mmol / L, and more preferably 10 to 300 mmol / L. The first precursor solution preferably contains 0.1 to 500 mmol, more preferably 1 to 30 mmol, of an indium halide per 100 ml of the amine compound.

[0035] The first precursor solution may further contain other halides containing elements other than In and Sb. Examples of other halides include 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. The content of other halides is preferably 0.5 mol or less, more preferably 0.2 mol or less, per mol of indium halide.

[0036] (Second precursor solution) The second precursor solution contains an antimony halide and an ether compound. The second precursor solution can be prepared by mixing the antimony halide and the ether compound. The mixing of the antimony halide and the ether compound is preferably carried out at a temperature of 30 to 80°C.

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

[0038] The ether compound is preferably a compound having 12 to 20 carbon atoms, and more preferably a compound having 12 to 16 carbon atoms.

[0039] The ether compound is preferably a dialkyl ether compound, more preferably a dialkyl ether compound having 12 to 20 carbon atoms, and even more preferably a dialkyl ether compound having 12 to 16 carbon atoms.

[0040] The ether compound is preferably a liquid at 25°C.

[0041] The boiling point of the ether compound is preferably 280°C or higher, more preferably 280 to 400°C, and even more preferably 280 to 350°C.

[0042] Specific examples of the ether compound include di-n-octyl ether and didecyl ether.

[0043] The content of antimony halide in the second precursor solution is preferably 10 to 1500 mmol / L, more preferably 50 to 1000 mmol / L, and even more preferably 100 to 1000 mmol / L. The second precursor solution preferably contains 0.1 to 15 mmol, more preferably 0.5 to 10 mmol, and even more preferably 1 to 10 mmol of antimony halide per 10 ml of the ether compound.

[0044] The second precursor solution may further contain other halides containing elements other than In and Sb. Examples of other halides include 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. The content of other halides is preferably 0.5 mol or less, more preferably 0.2 mol or less, per mol of antimony halide.

[0045] <<Reaction process>> In the reaction step, a reducing agent is added to the mixed solution obtained in the above step, and the indium halide and the antimony halide are reacted in the presence of the reducing agent.

[0046] 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.

[0047] 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.

[0048] Examples of silicon hydride reducing agents include triethylsilane, dimethylphenylsilane, and diphenylsilane.

[0049] Examples of aluminum hydride reducing agents include lithium aluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, diisobutylaluminum hydride, alkoxyaluminum hydride, and aluminum hydride.

[0050] Examples of calcium hydride reducing agents include calcium hydride.

[0051] Examples of the hydrazine-based reducing agent include hydrazine and its derivatives.

[0052] 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.

[0053] 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.

[0054] The reaction temperature is preferably 260 to 300° C. The upper limit is preferably 295° C. or lower, more preferably 290° C. or lower. The lower limit is preferably 250° C. or higher, more preferably 270° C. or higher.

[0055] 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.

[0056] 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 the inert gas include nitrogen gas and argon gas.

[0057] After the reaction is completed, it is preferable to cool the reaction mixture to 40° C. or less. Cooling may be natural cooling or forced cooling.

[0058] <Dispersion> The quantum dots obtained by the present invention can be dispersed in a solvent and used as a dispersion liquid.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The dispersion preferably contains a ligand. Examples of the ligand include those that function as ligands that coordinate to the quantum dots and have 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 those having 6 or more carbon atoms in the main chain, preferably those having 10 or more carbon atoms in the main chain. The ligand may be either a saturated or 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.

[0063] The dispersion liquid may contain a ligand containing a halogen element as a ligand. It 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 it is preferably an iodine element.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The polydentate ligand may be a ligand represented by any one of formulas (A) to (C). [ka]

[0068] 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.

[0069] 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, X B3 represents S, O or NH, L B1 and L B2 each independently represents a hydrocarbon group.

[0070] 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, X C4 represents N, L C1 ~L C3 each independently represents a hydrocarbon group.

[0071] X A1 , X A2 , X B1 , X B2 , X C1 , X C2 and X C3 The amino group represented by is not limited to -NH2, but also includes substituted amino groups and cyclic amino groups. Examples of substituted amino groups include monoalkylamino groups, dialkylamino groups, monoarylamino groups, diarylamino groups, and alkylarylamino groups. The amino group represented by these groups is preferably -NH2, a monoalkylamino group, or a dialkylamino group, and more preferably -NH2.

[0072] 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.

[0073] 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.

[0074] X in formula (C) C1 ~X C3At 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.

[0075] 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.

[0076] 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. Preferred specific examples of the group having 1 to 10 atoms include alkyl groups having 1 to 3 carbon atoms [methyl, ethyl, propyl, and isopropyl groups], alkenyl groups having 2 to 3 carbon atoms [ethenyl and propenyl groups], alkynyl groups having 2 to 4 carbon atoms [ethynyl, propynyl, etc.], cyclopropyl groups, alkoxy groups having 1 to 2 carbon atoms [methoxy and ethoxy groups], acyl groups having 2 to 3 carbon atoms [acetyl and propionyl groups], alkoxycarbonyl groups having 2 to 3 carbon atoms [methoxycarbonyl and ethoxycarbonyl groups], acyloxy groups having 2 carbon atoms [acetyloxy group], Examples of such groups 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.

[0077] In formula (A), XA1 and 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.

[0078] 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.

[0079] 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.

[0080] In addition, X A1 and X A2 is L A1 By separating them by 1 to 10 atoms, 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 structural formula below represent X A1 and X A2 It represents the order of the arrangement of atoms that make up the shortest molecular chain connecting the [ka]

[0081] To give a specific example, 3-mercaptopropionic acid is X A1 The site corresponding to X is a carboxyl group. A2 The site corresponding to L is a thiol group. 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. [ka]

[0082] X B1 and X B3 is L B1Separated by 1 to 10 atoms, X B2 and X B3 is L B2 Separated by 1 to 10 atoms, X C1 and X C4 is L C1 Separated by 1 to 10 atoms, X C2 and X C4 is L C2 Separated by 1 to 10 atoms, X C3 and X C4 is L C3 The meaning of being separated by 1 to 10 atoms is the same as above.

[0083] Specific examples of polydentate ligands include 3-mercaptopropionic acid, thioglycolic acid, 2-aminoethanol, 2-aminoethanethiol, 2-mercaptoethanol, glycolic acid, ethylene glycol, ethylenediamine, aminosulfonic acid, glycine, 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 Examples of suitable amines include 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.

[0084] 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.

[0085] <Method of manufacturing semiconductor film> The quantum dots obtained by the present invention can be used to produce a semiconductor film, which can be produced by applying the above-mentioned dispersion onto a substrate.

[0086] The shape, structure, size, etc. of the substrate to which the dispersion is applied are not particularly limited and 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 (Yttria-Stabilized Zirconia), a resin, a resin composite material, etc. Furthermore, an electrode, an insulating film, etc. may be formed on the substrate. In this case, the dispersion is also applied to the electrode and the insulating film on the substrate.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The ligand contained in the ligand solution may be 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. Furthermore, in the step of applying the ligand solution, two or more types of ligand solutions may be used.

[0091] 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.

[0092] After the step of applying the ligand solution, the film may be subjected to a rinsing step (rinsing step) in which the film is brought into contact with a rinsing liquid. The rinsing step can remove excess ligands contained in the semiconductor film and ligands detached from the quantum dots. The rinsing step may be performed multiple times using two or more rinsing liquids with different polarities (dielectric constants). For example, it is preferable to first rinse using a rinsing liquid with a high dielectric constant (also referred to as a first rinsing liquid), and then rinse using a rinsing liquid with a lower dielectric constant than the first rinsing liquid (also referred to as a second rinsing liquid). The dielectric constant of the first rinsing liquid is preferably 15 to 50, more preferably 20 to 45, and even more preferably 25 to 40. The dielectric constant of the second rinsing liquid is preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5.

[0093] The method for producing a semiconductor film may include a drying step. The drying step can remove any remaining solvent from the semiconductor film. 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 remaining 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 process for producing the semiconductor film, quantum dots and ligands may be oxidized.

[0094] <Photodetector element> The quantum dots obtained by the present invention can be used in a photodetector element, preferably in the photoelectric conversion layer of the photodetector element.

[0095] 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).

[0096] The photoelectric conversion layer using the quantum dots obtained by the present invention has excellent sensitivity to light in the infrared wavelength range, and is therefore preferably used as a photodetector for detecting light in the infrared wavelength range. That is, the photodetector is preferably used as an infrared light detecting element.

[0097] The infrared light preferably has a wavelength of more than 700 nm, more preferably has a wavelength of 800 nm or more, and even more preferably has a wavelength of 900 nm or more. The infrared light preferably has a wavelength of 3000 nm or less, more preferably has a wavelength of 2000 nm or less, and even more preferably has a wavelength of 1600 nm or less.

[0098] 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).

[0099] FIG. 1 shows an embodiment of a photodetector element. FIG. 1 is a diagram illustrating an embodiment of a photodiode-type photodetector element. The 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 disposed opposite the second electrode 12, a photoelectric conversion layer 13 disposed between the second electrode 12 and the first electrode 11, an electron transport layer 21 disposed between the first electrode 11 and the photoelectric conversion layer 13, and a hole transport layer 22 disposed 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. Although not shown, a transparent substrate may be disposed on the light-incident surface of the first electrode 11. Examples of the transparent substrate include a glass substrate, a resin substrate, and a ceramic substrate.

[0100] (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).

[0101] The film thickness of the first electrode 11 is not particularly limited, and 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 the cross section of the photodetector element 1 using a scanning electron microscope (SEM) or the like.

[0102] (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.

[0103] 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, the zinc oxide is preferably in the form of particles (zinc oxide particles) from the viewpoints of reducing residual organic components and increasing the contact area with the photoelectric conversion layer.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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, 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 easily 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.

[0108] 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.

[0109] 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 that the peak intensity be between 200 and 300 nm, and more preferably between 240 and 270 nm. There are no particular restrictions on the irradiation intensity of the ultraviolet light, but because the above-mentioned effects can be easily obtained and excessive damage to the film can be avoided, it is preferable that the wavelength be between 1 and 100 mW / cm. 2 It is preferable that the intensity is 10 to 50 mW / cm 2 There are no particular limitations on the treatment time, 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.

[0110] (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 can be 1.5 to 5.0.

[0111] (Hole transport layer) The hole transport layer 22 is a layer that has the 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.

[0112] The hole transport layer 22 is formed of a hole transport material that can perform this function. For example, 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[ ...carbonyl]thieno[4,8-bis[(2-ethylhexyl)carbonyl [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)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- Examples of suitable hole transport materials include 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), and PC71BM (methyl [6,6]-phenyl-C71-butyrate). Also usable are organic hole transport materials described in paragraphs 0209 to 0212 of JP-A No. 2001-291534. Quantum dots can also be used as the hole transport material. Quantum dot materials that make up 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 consisting of a combination of three or more of Group II, III, IV, V, and VI elements).Specific examples include semiconductor materials with relatively narrow band gaps such as PbS, PbSe, PbSeS, InN, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, AgS, AgSe, AgTe, SnS, SnSe, SnTe, Si, and InP. Ligands may be coordinated to the surface of the quantum dots.

[0113] 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.

[0114] (Second electrode) The second electrode 12 is preferably made 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. Any conductive carbon material can be used, including, for example, fullerenes, carbon nanotubes, graphite, and graphene.

[0115] 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 easier to collect holes generated in the device.

[0116] 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.

[0117] (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 a charge extraction layer, high external quantum efficiency can be obtained at a low applied voltage.

[0118] 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.

[0119] 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.

[0120] (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 for forming 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.

[0121] 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 λand preferably satisfy the relationship of the following formula (1-1), and more preferably satisfy the relationship of the following formula (1-2): λ When 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, resulting in a higher external quantum efficiency.

[0122] 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)

[0123] In the above formula, λ is the wavelength of the light to be detected by the photodetector element, 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, m is an integer of 0 or greater.

[0124] 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 improved.

[0125] 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 1When the photoelectric conversion layer 13 or the hole transport layer 22 is formed 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.

[0126] <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 the image sensor. Since the photoelectric conversion layer using the quantum dots obtained by 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 image 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.

[0127] 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.

[0128] The image sensor may include an infrared transmission 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.

[0129] The infrared transmission filter layer may be formed of a resin film containing a coloring material. Examples of the coloring material include chromatic coloring materials such as red, green, blue, yellow, purple, and orange coloring materials, and black coloring materials. The coloring material contained in the infrared transmission filter layer is preferably a combination of two or more chromatic coloring materials that form a black color, or a coloring material that contains a black coloring material. When a combination of two or more chromatic coloring materials forms a black color, examples of the combination of chromatic coloring materials include the following embodiments (C1) to (C7). (C1) An embodiment containing a red coloring material and a blue coloring material. (C2) An embodiment containing a red coloring material, a blue coloring material, and a yellow coloring material. (C3) An embodiment containing a red coloring material, a blue coloring material, a yellow coloring material, and a purple coloring material. (C4) An embodiment containing a red color material, a blue color material, a yellow color material, a purple color material, and a green color material. (C5) An embodiment containing a red coloring material, a blue coloring material, a yellow coloring material, and a green coloring material. (C6) An embodiment containing a red coloring material, a blue coloring material, and a green coloring material. (C7) An embodiment containing a yellow coloring material and a purple coloring material.

[0130] 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.

[0131] 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.

[0132] The spectral characteristics of the infrared transmission filter layer can be appropriately selected depending on the application of the image sensor, and examples include a filter layer that satisfies 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 having a maximum light transmittance in the thickness direction of the film in the wavelength range of 400 to 1100 nm of 20% or less (preferably 15% or less, more preferably 10% or less), and a minimum light transmittance in the wavelength range of 1400 to 1500 nm of 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). Furthermore, 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 A can be used. Two or more infrared transmission filters may be used in combination, or a dual bandpass filter that transmits two or more specific wavelength regions with one filter may be used.

[0133] 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.

[0134] 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 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. The material used to form the high refractive index material layer is preferably a material with a refractive index of 1.7 to 2.5. Specific examples include Sb2O3, Sb2S3, Bi2O3, CeO2, CeF3, HfO2, La2O3, Nd2O3, and Pr6O 11 , Sc2O3, SiO, Ta2O5, TiO2, TlCl, Y2O3, ZnSe, ZnS, ZrO2, etc. Materials used to form the low refractive index material layer preferably have a refractive index of 1.2 to 1.6. Specific examples include Al2O3, BiF3, CaF2, LaF3, PbCl2, PbF2, LiF, MgF2, MgO, NdF3, SiO2, SiO2, NaF, ThO2, ThF4, Na3AlF6, etc. The method for forming the dielectric multilayer film is not particularly limited, but examples 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 include the films described in JP-A-2014-130344 and JP-A-2018-010296.

[0135] 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 ±75 nm is more preferable, and the central wavelength λ t1 It is more preferably ±50 nm.

[0136] 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 multiple transmission wavelength bands.

[0137] The image sensor may include a color separation filter layer. Examples of the color separation filter layer include a filter layer containing colored pixels. Types of colored pixels include red pixels, green pixels, blue pixels, yellow pixels, cyan pixels, 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.

[0138] 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.

[0139] 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.

[0140] The image sensor may include an intermediate layer such as a planarization layer, a base layer, or an adhesion layer, an anti-reflection film, or a lens. For example, a film made from a composition described in International Publication No. 2019 / 017280 can be used as the anti-reflection film. For example, a structure described in International Publication No. 2018 / 092600 can be used as the lens. [Example]

[0141] 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.

[0142] Example 1 In a glove box, 10 mmol of indium chloride was added to 100 mL of oleylamine (liquid temperature: 60° C.) and stirred to prepare a first precursor solution 1. In a glove box, 5 mmol of antimony chloride was added to 10 mL of di-n-octyl ether (liquid temperature: 60° C.) and stirred to prepare a second precursor solution 1. 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 di-n-octyl ether, and the THF was distilled off to prepare reducing agent solution 1, which was a di-n-octyl ether solution of lithium triethylborohydride (concentration of lithium triethylborohydride: approximately 2.0 mol / L). In a glove box, 15 mL of the first precursor solution 1, 1.5 mL of the second precursor solution 1, and 15 mL of oleylamine were added to a three-neck flask and stirred. Next, nitrogen was flowed through the three-neck flask, and 4.0 mL of the reducing agent solution 1 was added, followed by heating to 290°C at a rate of 3°C / min. After the liquid temperature reached 290°C, it was held for 20 minutes, and then cooled to 40°C over 15 minutes. The three-neck flask was 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, 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, yielding a 40 mg / mL InSb quantum dot dispersion.

[0143] Example 2 The same operations as in Example 1 were carried out to prepare a first precursor solution 1, a second precursor solution 1 and a reducing agent solution 1. In a glove box, 15 mL of the first precursor solution 1, 1.5 mL of the second precursor solution 1, and 15 mL of oleylamine were added to a three-neck flask and stirred. Next, nitrogen was flowed through the three-neck flask, and 4.0 mL of the reducing agent solution 1 was added. The temperature was then raised to 280°C at a rate of 3°C / min. After the liquid temperature reached 280°C, the temperature was maintained for 20 minutes, and the reaction solution was cooled to 40°C over 15 minutes. The same procedure as in Example 1 was then repeated to obtain an InSb quantum dot dispersion with a concentration of 40 mg / mL.

[0144] (Comparative Example 1) The same operations as in Example 1 were carried out to prepare a first precursor solution 1 and a reducing agent solution 1. In a glove box, 5 mmol of antimony chloride was added to 100 mL of oleylamine (liquid temperature: 60° C.) and stirred to prepare a second precursor solution r1. In a glove box, 15 mL of the first precursor solution 1 and 15 mL of the second precursor solution r1 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. After 4.0 mL of reducing agent solution 1 was injected into the mixed solution, the temperature was raised to 290°C at a rate of 3°C / min. After the liquid temperature reached 290°C, the temperature was maintained for 20 minutes, and the reaction solution was cooled to 40°C over 15 minutes. The same procedure as in Example 1 was then performed to obtain an InSb quantum dot dispersion liquid with a concentration of 40 mg / mL.

[0145] [Measurement of average particle size and standard deviation of particle size] The average particle size and standard deviation of the particle size of the InSb quantum dots contained in the InSb quantum dot dispersion were measured using the image processing software (open resource) "ImageJ." Specifically, the InSb quantum dot dispersion was diluted 150 times with toluene, dropped onto a sample stage (super high-resolution carbon) that had been submerged in water for 10 seconds, air-dried, treated with a plasma cleaner, and photographed with a transmission electron microscope (TEM). The image processing software (open resource) "ImageJ" was used to confirm the particle area by measuring the outer periphery of the particles in the TEM image. The particle diameter was calculated by converting this area to particle diameter, and the average particle diameter and standard deviation of particle diameter were calculated from the values ​​measured for 300 particles.

[0146] [Table 1]

[0147] As shown in the above table, Examples 1 and 2 had smaller standard deviations of particle diameter than Comparative Example 1.

[0148] [Manufacturing of photodetector elements] 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.

[0149] 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.

[0150] 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.

[0151] Next, a 10 nm thick MoO3 film was formed on the hole transport layer by vacuum deposition using a metal mask, and then a 100 nm thick Au film (second electrode) was formed to form three element parts, thereby producing a photodiode-type light detection element.

[0152] (Method for forming a photoelectric conversion layer in a photodetector element) 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, and the film was then left to stand for 20 seconds, followed by spin drying at 2500 rpm for 10 seconds (step 2). Next, acetonitrile was dropped onto the InSb quantum dot assembly film as a rinse, and the film was spin-dried at 2500 rpm for 20 seconds. Next, octane was dropped onto the InSb quantum dot assembly film as a rinse, and the film was spin-dried at 2500 rpm for 20 seconds, and the ligands coordinated to the InSb quantum dots were exchanged from oleic acid and oleylamine to mercaptopropionic acid (step 3). Steps 1 to 3 constitute one cycle, and this cycle was repeated five times to deposit a 100-nm-thick InSb quantum dot assembly film (semiconductor film) in which the ligands had been exchanged to mercaptopropionic acid, forming a photoelectric conversion layer.

[0153] [Performance evaluation of photodetector elements] With a reverse voltage of 1 V applied to each photodetector, monochrome light with a wavelength of 1300 nm (50 μW / cm 2 The external quantum efficiency was evaluated when the sample was irradiated with light. The external quantum efficiency was calculated using the number of photoelectrons estimated from the difference between the current value when not irradiated with light and the current value when irradiated with light, and the number of irradiated photons, according to the following formula. The current value when not irradiated with light was taken as the dark current value. External quantum efficiency = (number of photoelectrons / number of irradiated photons) The values ​​shown in the columns for external quantum efficiency and dark current in the table below are values ​​for the central element among the three element parts.

[0154] [Table 2]

[0155] As shown in the above table, the photodetectors of Examples 11 and 12, which used the quantum dot dispersion liquids of the examples, exhibited more suppressed dark current.

[0156] By using the photodetector element obtained in the above examples and an optical filter prepared according to the methods described in WO 2016 / 186050 and WO 2016 / 190162, an image sensor can be produced by a known method, thereby obtaining an image sensor with good visible-infrared imaging performance. [Explanation of symbols]

[0157] 1: Photodetector element 11: First electrode 12: Second electrode 13: Photoelectric conversion layer 21:Electron transport layer 22: Hole transport layer

Claims

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

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

3. The method for producing quantum dots according to claim 1 , wherein the first precursor solution contains an indium halide and an amine compound.

4. The method for producing quantum dots according to claim 3 , wherein the amine compound includes oleylamine.

5. 3. The method for producing quantum dots according to claim 1, wherein the ether compound is a compound having 12 to 20 carbon atoms.

6. The method for producing quantum dots according to claim 1 or 2, wherein the ether compound is a liquid at 25°C.

7. The method for producing quantum dots according to claim 1 or 2, wherein the boiling point of the ether compound is 280°C or higher.

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