Dispersion liquid, method for manufacturing photoelectric conversion film, method for manufacturing photodetector, and method for manufacturing image sensor

Abstract

A dispersion liquid containing quantum dots with a band gap of 1.35 eV or less, ligands, organic solvent, and water. The content of the quantum dots in the components of the dispersion liquid excluding the ligands, the organic solvent, and the water is 50 mass% or more, and the content of the water in the dispersion liquid is 0.001-0.3 mass%. Methods for manufacturing a photoelectric conversion film, a photodetector, and an image sensor by using the dispersion liquid.

Description

Dispersion liquid, method for manufacturing photoelectric conversion film, method for manufacturing photodetector element, and method for manufacturing image sensor

[0001] The present invention relates to a dispersion liquid containing quantum dots, and also to a method for manufacturing a photoelectric conversion film, a photodetector, and an image sensor.

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

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

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

[0005] In addition, in recent years, the use of quantum dots in photoelectric conversion elements has been studied. For example, Patent Document 1 describes quantum dots having inorganic particles, the quantum dots having organic ligands and inorganic ligands on their surfaces, and the molar ratio of the inorganic ligands to the total of the inorganic ligands and the organic ligands being 25% or more and 99.8% or less, being used in a photoelectric conversion film of a photoelectric conversion element.

[0006] Japanese Patent Application Laid-Open No. 2020-150251

[0007] In recent years, along 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 in these devices, such as high external quantum efficiency for light of the target wavelength to be detected by the photodetector element.

[0008] The present inventors have conducted extensive research into dispersions containing quantum dots and have found that quantum dot aggregates tend to form in the dispersions when stored for long periods of time. Furthermore, they have found that when such aggregates are contained in a film, the external quantum efficiency tends to decrease.

[0009] Therefore, an object of the present invention is to provide a dispersion liquid that has excellent dispersibility and is capable of forming a quantum dot film having high external quantum efficiency even when the dispersion liquid is used after long-term storage. Another object of the present invention is to provide a method for manufacturing a photoelectric conversion film, a photodetector, and an image sensor.

[0010] The present invention provides the following: <1> A dispersion containing quantum dots having a band gap of 1.35 eV or less, a ligand, an organic solvent, and water, wherein the quantum dots account for 50% by mass or more of the components excluding the ligand, the organic solvent, and water from the dispersion, and the water content in the dispersion is 0.001 to 0.3% by mass. <2> The dispersion according to <1>, wherein the water content in the dispersion is 0.01 to 0.1% by mass. <3> The dispersion according to <1> or <2>, wherein the quantum dots are III-V quantum dots. <4> The dispersion according to any one of <1> to <3>, wherein the quantum dots have an average primary particle size of 0.5 nm or more and less than 100 nm. <5> The dispersion according to any one of <1> to <4>, wherein the quantum dots include at least one selected from InAs, InSb, InPAs, and InAsSb. <6> The dispersion according to any one of <1> to <5>, wherein the quantum dots have an absorbance maximum in a wavelength range of 900 to 1700 nm. <7> The dispersion according to any one of <1> to <6>, wherein the ligand comprises an inorganic halide. <8> The dispersion according to any one of <1> to <7>, wherein the ligand comprises an organic ligand having at least one functional group selected from a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, and a sulfo group. <9> The dispersion according to any one of <1> to <8>, wherein the organic solvent is a polar solvent. <10> A method for producing a photoelectric conversion film, comprising: applying the dispersion according to any one of <1> to <9> on a support to form a composition layer; and drying the composition layer. <11> A method for producing a photodetector, comprising the method for producing a photoelectric conversion film according to <10>. <12> A method for producing an image sensor, comprising the method for producing a photoelectric conversion film according to <10>.

[0011] According to the present invention, a dispersion liquid having excellent dispersibility and capable of forming a quantum dot film having high external quantum efficiency even when used after long-term storage can be provided. The present invention also provides a method for manufacturing a photoelectric conversion film, a photodetector, and an image sensor.

[0012] FIG. 2 illustrates an embodiment of a photodetector element.

[0013] 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).

[0014] <Dispersion> The dispersion of the present invention is a dispersion containing quantum dots having a band gap of 1.35 eV or less, a ligand, an organic solvent, and water, characterized in that the content of the quantum dots in the components excluding the ligand, the organic solvent, and the water from the dispersion is 50 mass% or more, and the content of water in the dispersion is 0.001 to 0.3 mass%.

[0015] The dispersion of the present invention has excellent dispersibility, and even when used with a dispersion that has been stored for a long period of time, it is possible to form a quantum dot film with high external quantum efficiency. The reason for this effect is presumed to be as follows. The dispersion of the present invention contains 0.001 to 0.3 mass% water, and it is presumed that this trace amount of water adsorbs to the ligands and the quantum dot surfaces, thereby increasing charge repulsion and suppressing aggregation of the quantum dots in the composition, thereby achieving excellent dispersibility. Furthermore, because the dispersion of the present invention has excellent dispersibility, it is presumed that a quantum dot film with high external quantum efficiency can be formed even after long-term storage.

[0016] The water content in the dispersion can be adjusted to fall within the above range by adjusting the production conditions of the dispersion and the amount of water added during production.

[0017] The water content in the dispersion of the present invention is preferably 0.01 to 0.1% by mass. This embodiment can further improve the dispersibility of quantum dots. Furthermore, a quantum dot film having a higher external quantum efficiency can be formed, and even when a dispersion that has been stored for a long period of time is used, a quantum dot film having an external quantum efficiency as high as that obtained when a dispersion immediately after production is used can be formed.

[0018] The water content in the dispersion can be measured by the Karl Fischer method. Specifically, the water content in the dispersion is measured using a Karl Fischer moisture meter (KF-06 manufactured by Mitsubishi Chemical Holdings Corporation), and the water content can be calculated using the following formula: Water content in dispersion (water content) = (water content / mass of dispersion) x 100

[0019] The quantum dot film obtained using the dispersion of the present invention can be used in a photodetector element or an image sensor. More specifically, the quantum dot film can be used as a photoelectric conversion film in a photodetector element or an image sensor. Therefore, the dispersion of the present invention is preferably used for the photoelectric conversion film in a photodetector element or an image sensor. Furthermore, the quantum dot film obtained using the dispersion of the present invention has excellent sensitivity to light with wavelengths in the infrared region. Therefore, an image sensor using the quantum dot film obtained using the dispersion of the present invention as a photoelectric conversion film can be particularly preferably used as an infrared sensor. Therefore, the dispersion of the present invention is preferably used for the photoelectric conversion film in an infrared sensor.

[0020] The dispersion of the present invention will be described in more detail below.

[0021] (Quantum dots) The dispersion of the present invention contains quantum dots. The quantum dots are preferably semiconductor particles containing metal atoms. In this specification, the term "metal atoms" also includes semi-metal atoms, such as Si atoms. In addition, the term "semiconductor" in this specification refers to a semiconductor having a specific resistance of 10 －２ Ωcm or more 10 ８ It means a substance with a resistivity of Ωcm or less.

[0022] The quantum dots preferably contain at least one element selected from the group consisting of Ga, Ge, P, As, Se, In, Sn, Sb, Te, Pb, Bi, Ag, Cu, and Hg, more preferably contain at least one element selected from the group consisting of Ga, P, As, Se, In, Sb, Te, and Bi, and even more preferably contain at least one element selected from the group consisting of P, As, Sb, and In.

[0023] The quantum dots are preferably group III-V quantum dots or group IV-VI quantum dots, and are more preferably group III-V quantum dots because the effects of the present invention are more pronounced.

[0024] Group III-V quantum dots are quantum dots containing group III elements (group 13 elements) and group V elements (group 15 elements). Examples of group III-V quantum dots include quantum dots made of compound semiconductors containing group III elements and group V elements. Group IV-VI quantum dots are quantum dots made of group IV elements (group 14 elements) and group VI elements (group 16 elements). Examples of group IV-VI quantum dots include quantum dots made of compound semiconductors containing group IV elements and group VI elements.

[0025] Examples of group III elements contained in III-V quantum dots include boron (B), aluminum (Al), gallium (Ga), and indium (In), with In being preferred. Examples of group V elements contained in III-V quantum dots include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), with at least one element selected from As and Sb being preferred. III-V quantum dots may further contain elements other than group III and V elements. Examples of other elements include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), and mercury (Hg).

[0026] Examples of the group IV elements contained in the group IV-VI quantum dots include silicon (Si), germanium (Ge), tin (Sn), and lead (Pb), with Pb being preferred. Examples of the group VI elements contained in the group IV-VI quantum dots include oxygen (O), sulfur (S), selenium (Se), and tellurium (Te), with at least one element selected from S and Se being preferred, and S being more preferred. The group IV-VI quantum dots may further contain elements other than the group IV and VI elements. Examples of other elements include Mg, Ca, Sr, Ba, Zn, Cd, and Hg.

[0027] Specific examples of quantum dots include PbS, PbSe, PbSeS, InN, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, InPAs, InAsSb, InPSb, HgTe, HgCdTe, and Ag ２ S, Ag ２ Se, Ag ２ Te, SnS, SnSe, SnTe, Si, InP, AgBiS ２ and AgBiSTe, and at least one selected from InAs, InSb, InPAs, InAsSb, InPSb, PbS and PbSe is preferred, and at least one selected from InAs, InSb, InPAs and InAsSb is more preferred.

[0028] The band gap of the quantum dots is 1.35 eV or less, preferably 1.1 eV or less, and more preferably 1.0 eV or less. The lower limit of the band gap of the quantum dots is not particularly limited, but can be 0.5 eV or more. If the band gap of the quantum dots is 1.35 eV, a quantum dot film having a high external quantum efficiency for light with wavelengths in the infrared region can be formed. The band gap of the quantum dots can be calculated from the energy at the maximum absorption wavelength of the absorption spectrum obtained by measuring optical absorption in the visible to infrared region using a UV-Vis-NIR spectrophotometer. Furthermore, in the case of quantum dots that do not have a maximum absorption wavelength, it can be determined from a Tauc plot, as described in Japanese Patent No. 5,949,567.

[0029] The quantum dots preferably have a maximum absorption in the wavelength range of 900 to 1700 nm, and more preferably have a maximum absorption in the wavelength range of 1300 to 1600 nm. By using such quantum dots, a quantum dot film can be formed that has a high external quantum efficiency for light with wavelengths in the infrared region.

[0030] It is also preferable that the quantum dots have high absorption for light having a wavelength in the range of 900 to 1700 nm (preferably, 1300 to 1600 nm). By using such quantum dots, it is possible to form a quantum dot film having a high external quantum efficiency for light having a wavelength in the infrared region.

[0031] The average primary particle diameter of the quantum dots is preferably 0.5 nm or more and less than 100 nm. The lower limit of the average primary particle diameter of the quantum dots is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more. The upper limit of the average primary particle diameter of the quantum dots is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less. If the average primary particle diameter of the quantum dots is within the above range, a quantum dot film having high external quantum efficiency for light with wavelengths in the infrared region can be formed. Note that, in this specification, the average primary particle diameter of the quantum dots is the average value of the primary particle diameters of 10 arbitrarily selected quantum dots. The primary particle diameter of the quantum dots can be measured using a transmission electron microscope.

[0032] The content of quantum dots in the dispersion is preferably 1 to 25% by mass. The lower limit is preferably 2% by mass or more, and more preferably 3% by mass or more. The upper limit is preferably 20% by mass or less. The content of quantum dots in the dispersion is preferably 10 to 250 mg / mL. The lower limit is preferably 20 mg / mL or more, and more preferably 30 mg / mL or more. The upper limit is preferably 200 mg / mL or less.

[0033] The content of quantum dots in the dispersion liquid excluding the ligand, organic solvent, and water is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In addition, the total content of quantum dots and ligands in the dispersion liquid excluding the organic solvent and water is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit can be 100% by mass or less.

[0034] (Ligand) The dispersion of the present invention contains a ligand. Examples of the ligand include inorganic ligands and organic ligands. The ligand preferably contains an inorganic ligand. The inorganic ligand is preferably an inorganic halide. By using a ligand containing an inorganic halide in the dispersion of the present invention, the effects of the present invention are more pronounced. The reason why such effects are obtained is presumed to be as follows. That is, since the dispersion of the present invention contains a predetermined amount of water, the water contained in the dispersion substitutes a portion of the inorganic halide with a hydroxy group, promoting capping of the quantum dots, and as a result, it is presumed that the occurrence of surface defects on the quantum dots can be suppressed.

[0035] Examples of halogen atoms contained in the inorganic halide include fluorine, chlorine, bromine, and iodine atoms, and bromine or iodine atoms are preferred. The inorganic halide is also preferably a compound containing at least one atom selected from the group consisting of Zn, Cd, Ga, Ge, As, Se, In, Sn, Sb, Te, Tl, Pb, Bi, and Po.

[0036] Specific examples of inorganic ligands include zinc iodide, zinc bromide, zinc chloride, indium iodide, indium bromide, indium chloride, cadmium iodide, lead chloride, lead bromide, lead iodide, cadmium bromide, cadmium chloride, gallium iodide, gallium bromide, gallium chloride, potassium sulfide, and sodium sulfide.

[0037] The organic ligand is preferably a compound having at least one functional group selected from a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, and a sulfo group, more preferably a compound having at least one functional group selected from a carboxy group, a mercapto group, an amino group, and a hydroxy group, and even more preferably a compound having a mercapto group. The organic ligand may be a monodentate ligand having only one of the above functional groups, or a multidentate ligand having two or more of the above ligands.

[0038] The organic ligand is also preferably a compound having a pKa of 3 or less. The pKa of the compound is more preferably 2.5 or less, because this allows the formation of a quantum dot film with high external quantum efficiency and further suppressed dark current. The lower limit of the pKa of the compound is preferably -2.0 or more, more preferably -1.0 or more, and even more preferably 0.5 or more.

[0039] Specific examples of monodentate ligands include 2-naphthylamine, 4-methylthioaniline, 4-methylbenzenethiol, 3,5-dimethylbenzenethiol, 4-chlorobenzenethiol, 4-methoxybenzenethiol, benzoic acid, phenylphosphonic acid, methanesulfonic acid, trifluoroacetic acid, bromoacetic acid, 3-phosphorylpropionic acid, glycine-N,N-bis(methylenephosphonic acid), 2-chloroethylphosphonic acid, phenyl phosphate, dimethyl phosphate, and trifluoromethanesulfonic acid. Of the above compounds, phenylphosphonic acid, methanesulfonic acid, trifluoroacetic acid, bromoacetic acid, 3-phosphorylpropionic acid, glycine-N,N-bis(methylenephosphonic acid), 2-chloroethylphosphonic acid, phenyl phosphate, dimethyl phosphate, and trifluoromethanesulfonic acid are compounds with a pKa of 3 or less.

[0040] The polydentate ligand may be a ligand represented by any one of formulas (A) to (C).

[0041] In formula (A), X Ａ１ and X Ａ２ each independently represents a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, or a sulfo group; L Ａ１ represents a hydrocarbon group.

[0042] In formula (B), X Ｂ１ and X Ｂ２ each independently represents a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, or a sulfo group; Ｂ３ represents S, O or NH; L Ｂ１ and L Ｂ２each independently represents a hydrocarbon group.

[0043] In formula (C), X Ｃ１ ~X Ｃ３ each independently represents a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, or a sulfo group; Ｃ４ represents N, and L Ｃ１ ~L Ｃ３ each independently represents a hydrocarbon group.

[0044] 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:

[0045] 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.

[0046] 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 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), and alkyl groups having 2 to 3 carbon atoms (ethynyl, propynyl, etc.). acylamino group [acetylamino group], hydroxyalkyl group having 1 to 3 carbon atoms [hydroxymethyl group, hydroxyethyl group, hydroxypropyl group], aldehyde group, hydroxy group, carboxy group, sulfo group, phospho group, carbamoyl group, cyano group, isocyanate group, mercapto group, nitro group, nitroxy group, isothiocyanate group, cyanate group, thiocyanate group, acetoxy group, acetamido group, formyl group, formyloxy group, formamido group, sulfamino group, sulfino group, sulfamoyl group, phosphono group, acetyl group, halogen atom, alkali metal atom, etc.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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

[0051] Specific examples of polydentate ligands include ethanedithiol, 3-mercaptopropionic acid, thiosalicylic acid, thioglycolic acid, 2-aminoethanol, 2-aminoethanethiol, 2-mercaptoethanol, glycolic acid, ethylenediamine, glycine, 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, 3-aminopropan-1-ol, 3-mercapto-2,2-bis(mercaptomethyl)-1-propanol, 1-thioglycerol, dimercaprol, 1-mercapto-2-butanol, 1-mercapto-2-pentanol, 3-mercapto-1-propanol, 2,3-dimercapto-1-propanol, diethanolamine, 2-(2-aminoethyl)aminoethanol, dimethylenetriamine, 1,1-oxybismethylamine amine, 1,1-thiobismethylamine, 2-[(2-aminoethyl)amino]ethanethiol, bis(2-mercaptoethyl)amine, 2-aminoethane-1-thiol, 1-amino-2-butanol, 1-amino-2-pentanol, L-cysteine, D-cysteine, 3-amino-1-propanol, L-homoserine, D-homoserine, aminohydroxyacetic acid, L-lactic acid, D-lactic acid, L-malic acid, D-malic acid, glyceric acid, 2-hydroxybutyric acid, L-tartaric acid, D-tartaric acid, 1,2 mercaptobenzoic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, 3-mercapto-2,2-bismercaptomethyl-1-propanol, trimethylolpropane tris(thioglycolate), pentaerythritol tetrakis(mercaptoacetate), dipentaerythritol hexakis(3-mercaptopropionate), dithioerythritol, and derivatives thereof.

[0052] The organic ligand may be a salt of a compound having at least one functional group selected from a carboxy group, a phospho group, a phosphonic acid group, and a sulfo group. The atom or atomic group constituting the salt with the compound having the functional group may be a metal ion (Li ＋ , Na ＋ , K. ＋ , Ca ２＋ , Mg ２＋ , Zn ２＋ , Cu ２＋ , Ga ３＋ , In ３＋ , Zr ４＋ , Hf ４＋ and the like), ammonium ions, etc. That is, examples of the salts of the compounds having the above functional groups include metal salts of the compounds having the above functional groups, ammonium salts of the compounds having the above functional groups, etc.

[0053] The compound having the functional group is preferably a compound having a pKa of 3 or less, more preferably a compound having a pKa of 2.5 or less. The lower limit of the pKa of the compound having the functional group is preferably -2.0 or more, more preferably -1.0 or more, and even more preferably 0.5 or more.

[0054] The molecular weight of the compound having the functional group is preferably 50 to 500. The upper limit of the molecular weight is preferably 450 or less, and more preferably 400 or less.

[0055] Specific examples of salts of compounds having the above functional group include metal salts and ammonium salts of compounds selected from phenylphosphonic acid, methanesulfonic acid, trifluoroacetic acid, bromoacetic acid, 3-phosphorylpropionic acid, glycine-N,N-bis(methylenephosphonic acid), 2-chloroethylphosphonic acid, methylphosphonic acid, methyl phosphate, phenyl phosphate, dimethyl phosphate, trifluoromethanesulfonic acid, and acetic acid.

[0056] The content of the ligand in the dispersion is preferably 1 to 15% by mass. The lower limit is preferably 2% by mass or more, and more preferably 2.5% by mass or more. The upper limit is preferably 10% by mass or less, and more preferably 7% by mass or less. The content of the ligand in the dispersion is preferably 10 to 150 mg / mL. The lower limit is preferably 20 mg / mL or more, and more preferably 25 mg / mL or more. The upper limit is preferably 100 mg / mL or less, and more preferably 70 mg / mL or less. The ratio of the quantum dots to the ligand is preferably 10 to 100 parts by mass of the ligand per 100 parts by mass of the quantum dots. The lower limit is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more. The upper limit is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less.

[0057] (Organic Solvent) The dispersion of the present invention contains an organic solvent. The organic solvent is not particularly limited, but is preferably a solvent that hardly dissolves quantum dots and easily dissolves ligands. The organic solvent may be either a polar solvent or a non-polar solvent, but is preferably a polar solvent, and more preferably a polar solvent having an amide group, because it can further improve the dispersibility of quantum dots.

[0058] The boiling point of the organic solvent is preferably 60 to 250° C. The lower limit is preferably 70° C. or higher, more preferably 80° C. or higher. The upper limit is preferably 200° C. or lower, more preferably 190° C. or lower.

[0059] Specific examples of the organic solvent include alkanes (n-hexane, n-octane, etc.), benzene, toluene, N,N-dimethylformamide, dimethyl sulfoxide, N-methylformamide, N,N-dimethylacetamide, propylene carbonate, and ethylene glycol, and N,N-dimethylformamide, dimethyl sulfoxide, or N-methylformamide is preferred.

[0060] The content of the organic solvent in the dispersion is preferably 50 to 99% by mass, more preferably 70 to 99% by mass, and even more preferably 85 to 98% by mass. The organic solvent contained in the dispersion may be a single type, or a mixed solvent containing two or more types. When two or more types of organic solvents are contained, the total amount thereof is preferably in the above range.

[0061] <Method for producing photoelectric conversion film> The method for producing a photoelectric conversion film of the present invention includes the steps of applying the dispersion of the present invention described above onto a support to form a composition layer, and drying the composition layer.

[0062] There are no particular limitations on the shape, structure, size, etc. of the support to which the dispersion is applied, and these can be appropriately selected depending on the purpose. The support may have a single-layer structure or a laminated structure. As the support, for example, a support made of an inorganic material such as silicon, glass, or YSZ (Yttrium-Stabilized Zirconia), a resin, a resin composite material, etc. can be used. Furthermore, an electrode, an insulating film, etc. may be formed on the support. In this case, the dispersion is also applied to the electrode and insulating film on the support.

[0063] The method for applying the dispersion is not particularly limited, and examples thereof include coating methods such as spin coating, dipping, inkjet printing, dispenser printing, screen printing, letterpress printing, intaglio printing, and spray coating.

[0064] After the composition layer is formed, it is dried. By drying, the solvent remaining in the composition layer can be removed. The drying temperature is preferably 50 to 150°C. The upper limit of the drying temperature is preferably 120°C or less, and more preferably 100°C or less. The lower limit of the drying temperature is preferably 55°C or more, and more preferably 60°C or more. The drying time is preferably 1 to 300 minutes. The upper limit of the drying time is preferably 200 minutes or less, and more preferably 100 minutes or less. The lower limit of the drying time is preferably 2 minutes or more, and more preferably 5 minutes or more.

[0065] In the method for producing a photoelectric conversion film of the present invention, the step of forming a composition layer and the step of drying the composition layer may be alternately repeated multiple times.

[0066] In the method for producing a photoelectric conversion film of the present invention, after the step of drying the composition layer, a step of applying a ligand solution onto the dried composition layer may be performed. By performing this step, the ligands coordinated to the quantum dots can be exchanged for the 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 on the quantum dots.

[0067] The ligand contained in the ligand solution may be the ligand described as being used in the dispersion of the present invention. The ligand contained in the ligand solution may be the same as or different from the ligand contained in the dispersion. The ligand solution may contain only one type of ligand, or may contain two or more types. Furthermore, two or more types of ligand solutions may be used in the step of applying the ligand solution.

[0068] The solvent contained in the ligand solution is preferably selected appropriately depending on the type of ligand contained in the ligand solution, and is preferably a solvent that easily dissolves the 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, and propanol. Furthermore, the solvent contained in the ligand solution is preferably a solvent that is unlikely to remain in the photoelectric conversion film that is formed. From the viewpoint of ease of drying and ease of removal by washing, a low-boiling alcohol, ketone, or nitrile is preferred, and methanol, ethanol, acetone, or acetonitrile is more preferred.

[0069] The method for applying the ligand solution is the same as the method for applying the dispersion onto the support, and the preferred embodiments are also the same.

[0070] When performing the step of applying a ligand solution, a step of rinsing the film after applying the ligand solution by contacting it with a rinse liquid (rinsing step) may be performed. By performing the rinsing step, excess ligands contained in the film and ligands detached from the quantum dots can be removed. Furthermore, remaining solvent and other impurities can be removed. The rinse liquid is preferably an aprotic solvent because it can more effectively remove excess ligands contained in the film and ligands detached from the quantum dots and easily maintain a uniform film surface by rearranging the quantum dot surface. Specific examples of aprotic solvents include acetonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, dioxane, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, hexane, octane, cyclohexane, benzene, toluene, chloroform, carbon tetrachloride, and dimethylformamide. Acetonitrile or tetrahydrofuran is preferred, and acetonitrile is more preferred.

[0071] The rinsing step may 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.

[0072] A photoelectric conversion film can be produced through such steps. The obtained photoelectric conversion film can be used in a photodetector or an image sensor. The photoelectric conversion film obtained using the dispersion of the present invention has excellent sensitivity to light with wavelengths in the infrared region, so that a photodetector using this photoelectric conversion film is preferably used as a photodetector that detects light with wavelengths in the infrared region. Therefore, the photoelectric conversion film is preferably used as a photoelectric conversion film for an infrared light detection element.

[0073] 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 2000 nm or less, and more preferably has a wavelength of 1600 nm or less.

[0074] The total content of the quantum dots and the ligands in the photoelectric conversion film is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, with the upper limit being 100% by mass or less.

[0075] <Method for manufacturing photodetector> The photodetector of the present invention includes the method for manufacturing a photoelectric conversion film of the present invention described above. Specifically, it is preferable to form the photoelectric conversion film of the photodetector element using the method for manufacturing a photoelectric conversion film described above.

[0076] 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).

[0077] Since the photoelectric conversion film obtained by the present invention has excellent sensitivity to light having a wavelength in the infrared region, the photodetector is preferably used as a photodetector for detecting light having a wavelength in the infrared region, i.e., the photodetector is preferably used as an infrared light detecting element.

[0078] 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).

[0079] FIG. 1 shows one embodiment of a photodetector element. FIG. 1 is a diagram illustrating one 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 film 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 film 13, and a hole transport layer 22 disposed between the second electrode 12 and the photoelectric conversion film 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 transparent substrates include glass substrates, resin substrates, and ceramic substrates.

[0080] (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).

[0081] 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.

[0082] (Electron Transport Layer) The electron transport layer 21 is a layer having a function of transporting electrons generated in the photoelectric conversion film 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.

[0083] 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 film.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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, the contact area with the photoelectric conversion film is large, and a film with 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.

[0088] 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 film 13.

[0089] 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 There is no particular limitation 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.

[0090] (Photoelectric Conversion Film) The photoelectric conversion film 13 is composed of a quantum dot film formed using the dispersion liquid of the present invention described above. The photoelectric conversion film 13 can be formed by the method described above.

[0091] The thickness of the photoelectric conversion film 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 film 13 for light of the target wavelength to be detected by the photodetector element can be 1.5 to 5.0.

[0092] (Hole Transport Layer) The hole transport layer 22 is a layer having a function of transporting holes generated in the photoelectric conversion film 13 to the electrode. The hole transport layer is also called an electron blocking layer.

[0093] 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.

[0094] 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.

[0095] (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 low 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, and graphene.

[0096] 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.

[0097] 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.

[0098] (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.

[0099] 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.

[0100] 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.

[0101] (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 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.

[0102] 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 film 13 side to the surface of the photoelectric conversion film 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 satisfy this relationship, 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 film 13, and as a result, the light is reinforced by the optical interference effect, thereby achieving a higher external quantum efficiency.

[0103] 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)

[0104] 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 film 13 side to the surface of the photoelectric conversion film 13 on the first electrode 11 side, and m is an integer of 0 or more.

[0105] 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.

[0106] 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 film 13 as an example, the thickness of the photoelectric conversion film is d １ , the wavelength λ of the photoelectric conversion film １ The refractive index of the light is N １ When the wavelength λ transmitted through the photoelectric conversion film 13 is １ The optical path length of the light is N １ ×d １ When the photoelectric conversion film 13 or the hole transport layer 22 is configured by 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.

[0107] <Method for manufacturing image sensor> The method for manufacturing an image sensor of the present invention includes the method for manufacturing a photoelectric conversion film of the present invention described above. Specifically, it is preferable to form the photoelectric conversion film of the image sensor using the method for manufacturing a photoelectric conversion film described above.

[0108] The photoelectric conversion film obtained by the present invention has excellent sensitivity to light with wavelengths in the infrared region, and therefore an image sensor using this photoelectric conversion film can be particularly preferably used as an infrared sensor. Furthermore, the image sensor can be preferably used to sense light with wavelengths of 900 to 2000 nm, and more preferably used to sense light with wavelengths of 900 to 1600 nm.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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, and the central wavelength λ ｔ１ It is more preferably ±50 nm.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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. 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.

[0123] 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.

[0124] <Preparation of Dispersion> 1 mL of an octane dispersion of quantum dots (quantum dot concentration: 50 mg / mL, oleic acid concentration: 50 mg / mL) with oleic acid coordinated to the surface, as shown in the table below, 0.5 g of a ligand (0.25 g of each of the ligands shown in the table below for Examples 18 and 116), and 5 mL of an organic solvent (2.5 mL of each of the solvents shown in the table below for Examples 19 and 117) were weighed into a centrifuge tube and vigorously stirred for 10 minutes. Next, 30 mL of hexane was added, and the mixture was vigorously stirred for 1 minute. The upper hexane layer was then removed. This procedure was repeated twice. An excess amount of toluene was then added, and the mixture was centrifuged at 4000 rpm for 5 minutes. The resulting precipitate was vacuum dried for 30 minutes, followed by the addition of 0.5 mL of an organic solvent (0.25 mL of each of the solvents shown in the table below for Examples 19 and 117) and water, followed by stirring for 2 hours to obtain a dispersion. All of the above operations were carried out under nitrogen. The water content in the dispersion is shown in the "moisture content" column in the table below. The water content in the dispersion (moisture content) was adjusted by the amount of water added. The water content in the dispersion (moisture content) was measured by the Karl Fischer method. Specifically, the amount of water in the dispersion was measured using a Karl Fischer moisture meter (KF-06, manufactured by Mitsubishi Chemical Holdings Corporation), and calculated using the following formula: Water content in dispersion (moisture content) = (amount of water / mass of dispersion) x 100

[0125] <Evaluation of Dispersibility> The obtained dispersion was left standing under nitrogen at 25°C for 2 days, 1 week, or 1 month, and then visually inspected for the presence or absence of aggregates to evaluate dispersibility. A: No aggregation was observed even after standing for 1 month. B: Slight aggregation was observed after standing for 1 month, but no aggregation was observed after standing for 1 week. C: No aggregation was observed after standing for 2 days, but aggregation was observed after standing for 1 week. D: In the production process of the dispersion, the precipitate was not dispersed after centrifugation.

[0126]

[0127]

[0128] The numerical value in the λmax column in the above table is the value of the maximum absorption wavelength of the quantum dots, and the numerical value in the average primary particle diameter column is the value of the average primary particle diameter of the quantum dots. Furthermore, the numerical value in the content column in the above table is the content value of the quantum dots or ligands in the components excluding the organic solvent and water. Furthermore, details of the materials listed in the type column in the above table, indicated by abbreviations, are as follows. In the dispersions of Examples 1 to 19, 101 to 117 and Comparative Examples 1, 2, 101, and 102, the content of the quantum dots in the components excluding the ligand, organic solvent, and water was 95% by mass or more, and the total content of the quantum dots and ligands in the components excluding the organic solvent and water was 95% by mass or more.

[0129] (Ligand) L1-1: InBr ３ L1-2: InCl ３ L1-3: InI ３ L2-1: 3-aminopropan-1-ol L2-2: 3-mercaptopropionic acid L2-3: Trifluoroacetic acid L2-4: 3-mercapto-2,2-bis(mercaptomethyl)-1-propanol L2-5: 3-aminopropan-1-ol L2-6: Methylphosphonic acid L2-7: Methanesulfonic acid L2-8: Mercaptoethanol L2-9: Methylamine acetic acid

[0130] (Organic solvents) S-1: N,N-dimethylformamide S-2: dimethyl sulfoxide S-3: ethylene glycol

[0131] As shown in the above table, all of the dispersions of the examples were excellent in dispersibility.

[0132] <Preparation of Zinc Oxide Particle Dispersion> (Zinc Oxide Particle Dispersion 1) 1.5 mmol of zinc acetate dihydrate and 15 mL of dimethyl sulfoxide (DMSO) were weighed and stirred in a flask to prepare a zinc acetate solution. A TMACl solution was prepared by dissolving 4 mmol of tetramethylammonium chloride (TMACl) in 4 mL of methanol, and a KOH solution was prepared by dissolving 4 mmol of potassium hydroxide (KOH) in 4 mL of methanol. While vigorously stirring the TMACl solution, the KOH solution was slowly added. After stirring for 30 minutes, the insoluble components were removed through a 0.45 μm pore filter to obtain a tetramethylammonium hydroxide (TMAH) solution. 6 mL of the TMAH solution was added dropwise to the zinc acetate solution in the flask at a rate of 6 mL / min. After holding for 1 hour, the reaction solution was recovered. An excess amount of acetone was added to the reaction solution, and the mixture was centrifuged at 10,000 rpm for 10 minutes. The supernatant was then removed, and the precipitate was dispersed in methanol. The precipitate was then precipitated again with acetone, and 5 ml of ethanol and 80 μl of aminoethanol were added thereto. The mixture was then ultrasonically dispersed to obtain zinc oxide particle dispersion 1 having a concentration of non-doped zinc oxide particles of approximately 30 mg / mL.

[0133] <Production of Photodetector> An ITO (Indium Tin Oxide) film approximately 100 nm thick was formed on quartz glass by sputtering to form a first electrode. Next, a solution of 1 g of zinc acetate dihydrate and 284 μl of ethanolamine dissolved in 10 ml of methoxyethanol was spin-coated onto the ITO film (first electrode) at 3000 rpm. This was then heated at 200°C for 30 minutes to form a zinc oxide sol-gel film approximately 40 nm thick. Next, zinc oxide particle dispersion 1 was dropped onto the sol-gel film, spin-coated at 2500 rpm, and heated at 70°C for 30 minutes. This process was repeated twice, and then the zinc oxide particle dispersion 1 was measured using a UVO-CLEANER MODEL 144AX-100 manufactured by Jlight at 30 mW / cm. ２An ultraviolet ozone treatment was performed for 5 minutes under conditions of ultraviolet ray 254 nm (wavelength peak 254 nm), forming a zinc oxide particle film with a thickness of approximately 130 nm to form an electron transport layer. Next, a dispersion liquid shown in the table below was dropped onto the electron transport layer, followed by spin coating at 1000 rpm and drying at 120°C for 10 minutes to form a quantum dot film. The quantum dot film formation process was repeated four times to form a photoelectric conversion film with a thickness of 180 nm. The photoelectric conversion film was then dried for 10 hours in a glove box. Each dispersion liquid was used immediately after production and after storage at 25°C under a nitrogen atmosphere for one month.

[0134] Next, a dichlorobenzene solution (concentration: 5 mg / mL) of PTB7 (poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl})) was spin-coated onto the photoelectric conversion film at 2000 rpm, and then dried in a glove box for 10 hours to form a hole transport layer.

[0135] Next, a 5 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 produce a photodiode type light detecting element.

[0136] <Evaluation> (Photodetector elements using the dispersions of Examples 1 to 19 (Production Examples 1 to 19) and photodetector elements using the dispersions of Comparative Examples 1 and 2 (Production Examples R1 and R2)) For each photodetector element, the external quantum efficiency was evaluated using a semiconductor parameter analyzer (C4156, manufactured by Agilent). First, the current-voltage characteristics (I-V 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 value was evaluated. Here, the dark current value was defined as the value at -1 V. Next, the I-V characteristics were measured while sweeping the voltage from 0 V to -2 V in a state where monochromatic light with a wavelength of 940 nm was irradiated. The photocurrent value was determined by subtracting the dark current value from the current value in a state where -1 V was applied, and the external quantum efficiency was calculated from this value.

[0137] In the column of initial performance in the table below, the value of external quantum efficiency using a photodetector element manufactured using the dispersion immediately after manufacture in each manufacturing example is shown.

[0138] Furthermore, for the photodetector element of each manufacturing example, the degree of variation in external quantum efficiency was calculated using the following formula, and the stability over time was evaluated based on the following criteria: Degree of variation in external quantum efficiency = |1 - (external quantum efficiency of photodetector element prepared using dispersion after storage at 25°C for 1 month / external quantum efficiency of photodetector element prepared using dispersion immediately after production) | x 100 A: The degree of variation in external quantum efficiency is less than 1% B: The degree of variation in external quantum efficiency is 1% or more and less than 5% C: The degree of variation in external quantum efficiency is 5% or more and less than 10% D: The degree of variation in external quantum efficiency is 10% or more

[0139]

[0140] As shown in the table above, the photodetector element manufactured using the dispersion of the example had a higher external quantum efficiency than the photodetector element manufactured using the dispersion of the comparative example, and also had excellent stability over time.

[0141] (Photodetecting elements using the dispersions of Examples 101 to 117 (Production Examples 101 to 117) and photodetecting elements using the dispersions of Comparative Examples 101 and 102 (Production Examples R101 and R102)) For each photodetecting element, the external quantum efficiency was evaluated using a semiconductor parameter analyzer (C4156, manufactured by Agilent). First, the current-voltage characteristics (I-V 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 value was evaluated. Here, the dark current value was the value at -1 V. Next, the I-V characteristics were measured while sweeping the voltage from 0 V to -2 V in a state where monochromatic light with a wavelength of 1450 nm was irradiated. The photocurrent value was determined by subtracting the dark current value from the current value in a state where -1 V was applied, and the external quantum efficiency was calculated from this value.

[0142] In the column of initial performance in the table below, the value of external quantum efficiency using a photodetector element manufactured using the dispersion immediately after manufacture in each manufacturing example is shown.

[0143] Furthermore, for the photodetector element of each manufacturing example, the degree of variation in external quantum efficiency was calculated using the following formula, and the stability over time was evaluated based on the following criteria: Degree of variation in external quantum efficiency = |1 - (external quantum efficiency of photodetector element prepared using dispersion after storage at 25°C for 1 month / external quantum efficiency of photodetector element prepared using dispersion immediately after production) | x 100 A: The degree of variation in external quantum efficiency is less than 1% B: The degree of variation in external quantum efficiency is 1% or more and less than 5% C: The degree of variation in external quantum efficiency is 5% or more and less than 10% D: The degree of variation in external quantum efficiency is 10% or more

[0144]

[0145] As shown in the table above, the photodetector element manufactured using the dispersion of the example had a higher external quantum efficiency than the photodetector element manufactured using the dispersion of the comparative example, and also had excellent stability over time.

[0146] By using the photodetector elements obtained in the examples and optical filters prepared according to the methods described in WO 2016 / 186050 and WO 2016 / 190162 to prepare an image sensor by a known method, an image sensor having good visible-infrared imaging performance can be obtained.

[0147] 1: Photodetector element 11: First electrode 12: Second electrode 13: Photoelectric conversion film 21: Electron transport layer 22: Hole transport layer

Claims

1. A dispersion containing quantum dots having a band gap of 1.35 eV or less, a ligand, an organic solvent, and water, wherein the content of the quantum dots in the components excluding the ligand, the organic solvent, and the water from the dispersion is 50% by mass or more, and the content of water in the dispersion is 0.001 to 0.3% by mass.

2. The dispersion according to claim 1, wherein the content of water in the dispersion is 0.01 to 0.1% by mass.

3. The dispersion according to claim 1 or 2, wherein the quantum dots are III-V quantum dots.

4. The dispersion according to claim 1 or 2, wherein the average primary particle size of the quantum dots is 0.5 nm or more and less than 100 nm.

5. The dispersion according to claim 1 or 2, wherein the quantum dots include at least one selected from the group consisting of InAs, InSb, InPAs, and InAsSb.

6. The dispersion according to claim 1 or 2, wherein the quantum dots have a maximum absorption in the wavelength range of 900 to 1700 nm.

7. The dispersion of claim 1 or 2, wherein the ligand comprises an inorganic halide.

8. The dispersion according to claim 1 or 2, wherein the ligand comprises an organic ligand having at least one functional group selected from a carboxy group, a mercapto group, an amino group, a hydroxy group, a phospho group, a phosphonic acid group, and a sulfo group.

9. The dispersion according to claim 1 or 2, wherein the organic solvent is a polar solvent.

10. A method for producing a photoelectric conversion film, comprising the steps of: applying the dispersion liquid according to claim 1 or 2 onto a support to form a composition layer; and drying the composition layer.

11. A method for manufacturing a photodetector, comprising the method for manufacturing a photoelectric conversion film according to claim 10.

12. A method for manufacturing an image sensor, comprising the method for manufacturing a photoelectric conversion film according to claim 10.

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