TWI873142B - Semiconductor film, photoelectric conversion element, image sensor and method for manufacturing semiconductor film - Google Patents

Abstract

The present invention provides a semiconductor film, a photoelectric conversion element, an image sensor and a method for manufacturing a semiconductor film having excellent driving durability. The semiconductor film comprises: an aggregate of semiconductor quantum dots comprising metal atoms; and a ligand coordinated to the semiconductor quantum dots, the ligand comprising a first ligand being an inorganic halide and a second ligand represented by any one of formulas (A) to (C). ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 , and ^XB1 and ^XB3 are separated by 1 atom or 2 atoms by L ^B1 or L ^B2 . ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 . ^XC1 and ^XC4 are separated by ^LC1 by 3 to 10 atoms, and ^XC2 and ^XC4 , as well as ^XC3 and ^XC4, are separated by ^LC2 or ^LC3 by 1 to 10 atoms, respectively.

Description

Semiconductor film, photoelectric conversion element, image sensor and method for manufacturing semiconductor film

The present invention relates to a semiconductor film containing semiconductor quantum dots containing metal atoms, a photoelectric conversion element, an image sensor, and a method for manufacturing the semiconductor film.

In recent years, light detection components that can detect light in the infrared region have attracted much attention in the fields of smartphones, surveillance cameras, and car cameras.

In the past, photodetection elements used in image sensors and the like used silicon photodiodes using silicon wafers as the material for the photoelectric conversion layer. However, silicon photodiodes have low sensitivity in the infrared region with a wavelength of 900nm or more.

In addition, regarding the InGaAs semiconductor material known as a near-infrared light receiving element, in order to achieve high quantum efficiency, a very high-cost process such as crystal film growth is required, and it has not yet been popularized.

In recent years, semiconductor quantum dots have been studied. Non-patent document 1 describes a solar cell device having a semiconductor film containing PbS quantum dots treated with ZnI ₂ and 3-butylene propionic acid as a photoelectric conversion layer.

[Non-patent document 1] Santanu Pradhan, Alexandros Stavrinadis, Shuchi Gupta, Yu Bi, Francesco Di Stasio, and Gerasimos Konstantatos, "Trap-State Suppression and Improved Charge Transport in PbS Quantum Dot Solar Cells with Synergistic Mixed-Ligand Treatments", Small 13, 17005 98 (2017).

The inventor of the present invention has studied the semiconductor film described in non-patent document 1 and found that the semiconductor film has room for improving driving durability.

Therefore, the purpose of the present invention is to provide a semiconductor film, a photoelectric conversion element, an image sensor and a method for manufacturing a semiconductor film with excellent driving durability.

According to the research of the inventor, it is found that the above purpose can be achieved by setting the following structure and completing the present invention. Thus, the present invention provides the following contents.

<1> A semiconductor film comprising: an aggregate of semiconductor quantum dots comprising metal atoms; and ligands coordinated to the semiconductor quantum dots, wherein the ligands comprise a first ligand being an inorganic halide and a second ligand represented by any one of formulas (A) to (C);

In formula (A), ^XA1 and ^XA2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^A1 represents a alkyl group, and ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 ; in formula (B), ^XB1 and ^XB2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XB3 represents S, O or NH, L ^B1 and L ^B2 each independently represent a alkyl group, ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 ; in formula (C), ^XC1 to ^XC3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XC4 represents N, L ^C1 to L ^C3 independently represent a alkyl group, X ^C1 and X ^C4 are separated by 3 to 10 atoms by L ^C1 , X ^C2 and X ^C4 are separated by 1 to 10 atoms by L ^C2 , and X ^C3 and X ^C4 are separated by 1 to 10 atoms by L ^C3 .

<2> The semiconductor film as described in <1>, wherein the semiconductor quantum dots contain Pb atoms.

<3> The semiconductor film as described in <1> or <2>, wherein the first ligand comprises at least one selected from Group 12 elements and Group 13 elements.

<4> A semiconductor film as described in any one of <1> to <3>, wherein the first ligand comprises a Zn atom.

<5> A semiconductor film as described in any one of <1> to <4>, wherein the first ligand comprises an iodine atom.

<6> The semiconductor film as described in any one of <1> to <5>, which contains two or more of the above-mentioned first ligands.

<7> The semiconductor film according to any one of <1> to <6>, wherein the second ligand is represented by any one of the formulas (A) to (C), at least one of ^XA1 and ^XA2 in the formula (A) is a thiol group, an amine group, a hydroxyl group or a carboxyl group, at least one of XB1 and XB2 in the formula (B) is a thiol group, an amine group, a hydroxyl group or a carboxyl group, and at least one of ^{XC1 to XC3} in the formula (C) is a thiol group, an amine group, a hydroxyl group or a carboxyl ^group .

<8> A semiconductor film as described in any one of <1> to <6>, wherein the second ligand is at least one selected from 4-butylbutyric acid, 3-aminopropanol, 3-butylpropanol, N-(3-aminopropyl)-1,3-propylenediamine, 3-(bis(3-aminopropyl)amino)propane-1-ol, 3-aminopropylphosphonic acid and their derivatives.

<9> The semiconductor film as described in any one of <1> to <8>, further comprising a ligand other than the first ligand and the second ligand.

<10> A photoelectric conversion element comprising a semiconductor film as described in any one of <1> to <9>.

<11> The photoelectric conversion element as described in <10> is a photodiode type light detection element.

<12> An image sensor comprising the photoelectric conversion element described in <10> or <11>.

<13> The image sensor as described in <12> senses light with a wavelength of 900nm~1600nm.

<14> A method for manufacturing a semiconductor film, comprising: a semiconductor quantum dot aggregate formation process, wherein a semiconductor quantum dot dispersion liquid containing semiconductor quantum dots including metal atoms, a third ligand coordinated to the semiconductor quantum dots and different from a first ligand being an inorganic halide and a second ligand represented by any one of formulas (A) to (C), and a solvent is provided on a substrate to form a semiconductor quantum dot aggregate film; and a ligand replacement process, wherein a semiconductor quantum dot aggregate is formed by the semiconductor quantum dot aggregate. A film of the semiconductor quantum dot aggregate formed by a process is provided, wherein a ligand solution 1 comprising a first ligand being an inorganic halide and a solvent and a ligand solution 2 comprising a second ligand represented by any one of formulas (A) to (C) and a solvent are provided, or a ligand solution 3 comprising a first ligand being an inorganic halide, a second ligand represented by any one of formulas (A) to (C) and a solvent are provided, and the third ligand coordinated to the semiconductor quantum dot is replaced by the first ligand and the second ligand;

In formula (A), ^XA1 and ^XA2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^A1 represents a alkyl group, and ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 ; in formula (B), ^XB1 and ^XB2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XB3 represents S, O or NH, L ^B1 and L ^B2 each independently represent a alkyl group, ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 ; in formula (C), ^XC1 to ^XC3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XC4 represents N, L ^C1 to L ^C3 independently represent a alkyl group, X ^C1 and X ^C4 are separated by 3 to 10 atoms by L ^C1 , X ^C2 and X ^C4 are separated by 1 to 10 atoms by L ^C2 , and X ^C3 and X ^C4 are separated by 1 to 10 atoms by L ^C3 .

<15> The method for manufacturing a semiconductor film as described in <14> further includes a rinsing process of bringing an aprotic solvent into contact with the film of the semiconductor quantum dot aggregate for rinsing.

<16> The method for manufacturing a semiconductor film as described in <15>, wherein the aprotic solvent is a polar aprotic solvent.

<17> The method for manufacturing a semiconductor film as described in <15>, wherein the aprotic solvent is at least one selected from acetonitrile and acetone.

<18> A method for manufacturing a semiconductor film as described in any one of <14> to <17>, wherein in the semiconductor quantum dot aggregate formation process, a semiconductor quantum dot aggregate film having a thickness of 30 nm or more is formed, and the complex stability constant K1 of the second ligand relative to the metal atoms contained in the semiconductor quantum dots is 6 or more.

<19> The method for manufacturing a semiconductor film as described in <18>, wherein the complex stability constant K1 of the second ligand relative to the metal atoms contained in the semiconductor quantum dot is greater than 8.

<20> A method for manufacturing a semiconductor film as described in <18>, wherein the semiconductor quantum dots contain Pb atoms, and the complex stability constant K1 of the second ligand relative to the Pb atoms is greater than 6.

According to the present invention, a semiconductor film, a photoelectric conversion element, an image sensor and a method for manufacturing a semiconductor film with excellent driving durability can be provided.

1: Light detection element

11: Upper electrode

12: Lower electrode

12a, 13a: Surface

13: Photoelectric conversion layer

14:65 Comb-shaped electrodes

15: Reference electrode

16: Counter electrode

17: Working electrode

18: Quartz glass

FIG1 is a diagram showing an implementation form of a light detection element.

FIG2 is a diagram showing a substrate (a substrate having a comb-type platinum electrode) used for manufacturing the test piece 1.

The following is a detailed description of the contents of the present invention.

In this manual, "~" is used to mean that the numerical values written before and after it are included as lower and upper limits.

In the marking of groups (atomic groups) in this manual, the markings that are not marked with substituted and unsubstituted include groups (atomic groups) without substituents, and also include groups (atomic groups) with substituents. For example, "alkyl" includes not only alkyl groups without substituents (unsubstituted alkyl groups), but also alkyl groups with substituents (substituted alkyl groups).

<Semiconductor film>

The semiconductor film of the present invention is characterized by comprising: an aggregate of semiconductor quantum dots, comprising metal atoms; and ligands coordinated to the semiconductor quantum dots, wherein the ligands comprise a first ligand being an inorganic halide and a second ligand represented by any one of formulas (A) to (C).

The semiconductor film of the present invention has excellent driving durability. The detailed reason for obtaining such an effect is not clear, but it is presumed to be as follows. In the ligand represented by formula (A) in the second ligand (hereinafter, also referred to as ligand (A)), it is presumed that the metal atom is coordinated to the semiconductor quantum dot at the positions of ^XA1 and ^XA2 . In addition, in the ligand represented by formula (B) (hereinafter, also referred to as ligand (B)), it is presumed that the metal atom is coordinated to the semiconductor quantum dot at the positions of ^XB1 to ^XB3 . In addition, in the ligand represented by formula (C) (hereinafter, also referred to as ligand (C)), it is presumed that the metal atom is coordinated to the semiconductor quantum dot at the positions of ^XC1 to ^XC4 . Thus, ligand (A), ligand (B), and ligand (C) all have multiple sites coordinated to the metal atoms of the semiconductor quantum dot in one molecule, and therefore are presumed to be chelated to the metal atoms of the semiconductor quantum dot. The coordination sites of these ligands are linked to each other by relatively long molecular chains, and therefore are presumed to be flexible, and are not easily distorted when coordinated to the semiconductor quantum dot, and are stably coordinated. Therefore, it is presumed that the second ligand is firmly coordinated to the surface of the semiconductor quantum dot, and the ligand is not easily peeled off from the surface of the semiconductor quantum dot. Furthermore, in the present invention, the ligand coordinated to the semiconductor quantum dot also includes a first ligand which is an inorganic halide. Therefore, it is presumed that the first ligand is coordinated to the gap where the second ligand is not coordinated, and it is presumed that the surface defects of the semiconductor quantum dot can be reduced.

For this reason, it is speculated that the semiconductor film of the present invention has excellent driving durability.

The semiconductor film of the present invention is described in detail below.

(Agglomeration of semiconductor quantum dots containing metal atoms)

The semiconductor film has an aggregate of semiconductor quantum dots containing metal atoms. In addition, the semiconductor quantum dot aggregate refers to a form in which a plurality of semiconductor quantum dots (for example, more than 100 per 1 μm ² ) are arranged close to each other. In addition, the "semiconductor" in the present invention refers to a substance having a specific resistance value of more than 10 ^-2 Ω‧cm and less than 10 ⁸ Ω‧cm.

Semiconductor quantum dots are semiconductor particles with metal atoms. In addition, in the present invention, metal atoms also include semimetal atoms represented by Si atoms. As semiconductor quantum dot materials constituting semiconductor quantum dots, for example, nanoparticles (0.5 nm or more and less than 100 nm) of general semiconductor crystals [a) Group IV semiconductors, b) Group IV-IV, Group III-V or Group II-VI compound semiconductors, c) compound semiconductors containing a combination of three or more elements from Group II, Group III, Group IV, Group V and Group VI] can be cited.

The semiconductor quantum dots preferably contain at least one metal atom selected from Pb atoms, In atoms, Ge atoms, Si atoms, Cd atoms, Zn atoms, Hg atoms, Al atoms, Sn atoms, and Ga atoms, and more preferably contain at least one metal atom selected from Pb atoms, In atoms, Ge atoms, and Si atoms. For the reason that the effect of the present invention can be more significantly obtained, it is further preferred to contain Pb atoms.

Specific examples of semiconductor quantum dot materials constituting semiconductor quantum dots include PbS, PbSe, PbSeS, InN, InAs, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, Ag2S, Ag2Se, Ag2Te, SnS, SnSe, SnTe, Si, InP and other semiconductor materials with relatively narrow band gaps. Among them, for reasons such as large absorption coefficient of light in the infrared region, long lifetime of photocurrent, and large carrier mobility, it is preferred that semiconductor quantum dots contain PbS or PbSe, and it is more preferred that they contain PbS.

Semiconductor quantum dots can be materials with a core-shell structure in which a semiconductor quantum dot material is set as a core and a coating compound covers the semiconductor quantum dot material. Examples of coating compounds include ZnS, ZnSe, ZnTe, ZnCdS, CdS, GaP, etc.

The band gap of semiconductor quantum dots is preferably 0.5eV~2.0eV. When the semiconductor film of the present invention is applied to a photodetection element, more specifically, to a photoelectric conversion layer of a photodetection element, it can be set as a photodetection element capable of detecting light of various wavelengths according to the application. For example, it can be set as a photodetection element capable of detecting light in the infrared region. The upper limit of the band gap of semiconductor quantum dots is preferably below 1.9eV, more preferably below 1.8eV, and further preferably below 1.5eV. The lower limit of the band gap of semiconductor quantum dots is preferably above 0.6eV, and more preferably above 0.7eV.

The average particle size of semiconductor quantum dots is preferably 2nm~15nm. In addition, the average particle size of semiconductor quantum dots refers to the average particle size of 10 semiconductor quantum dots. A transmission electron microscope can be used to measure the particle size of semiconductor quantum dots.

Generally, semiconductor quantum dots contain particles of various sizes ranging from several nm to tens of nm. If the average particle size of semiconductor quantum dots is reduced to a size below the Bohr radius of the intrinsic electrons in semiconductor quantum dots, the band gap of semiconductor quantum dots changes due to the quantum size effect. If the average particle size of semiconductor quantum dots is below 15nm, it is easy to control the band gap based on the quantum size effect.

There is no particular limit to the thickness of the semiconductor film, but from the perspective of obtaining high conductivity, 10nm~600nm is preferred, 50nm~600nm is more preferred, 100nm~600nm is further preferred, and 150nm~600nm is further preferred. The upper limit of the thickness is preferably below 550nm, more preferably below 500nm, and further preferably below 450nm.

(ligand)

The semiconductor film includes a ligand coordinated to the semiconductor quantum dot. The ligand includes a first ligand that is an inorganic halogenide and a second ligand represented by any one of formulas (A) to (C). The semiconductor film may include only one first ligand or more than two first ligands. Furthermore, the semiconductor film may include only one second ligand or more than two second ligands.

〔First ligand〕

First, the first ligand is explained. The first ligand is an inorganic halide. As the first ligand, the halogen atom contained in the inorganic halide, there can be cited fluorine atom, chlorine atom, bromine atom and iodine atom. Iodine atom is preferred because it is easy to obtain high coordination force.

The first ligand, i.e., the inorganic halide, preferably contains at least one selected from the elements of Group 12 and Group 13. Among them, the first ligand is preferably a compound containing a metal atom selected from Zn atom, In atom, and Cd atom, and more preferably a compound containing a Zn atom. For the reason that it is easily ionized and easily coordinated to semiconductor quantum dots, the inorganic halide is preferably a salt of a metal atom and a halogen atom.

Specific examples of the first ligand 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, among which zinc iodide is particularly preferred.

In addition, regarding the first ligand, in the film, the inorganic halides are sometimes coordinated to the surface of the semiconductor quantum dot, and sometimes dissociate into halogen ions and inorganic ions and each of them is coordinated to the surface of the semiconductor quantum dot. To give a specific example, in the case of zinc iodide, zinc iodide is sometimes coordinated to the surface of the semiconductor quantum dot, and zinc iodide is sometimes dissociated into iodine ions and zinc ions and each of them is coordinated to the surface of the semiconductor quantum dot.

[Second ligand]

Next, the second ligand is described. The second ligand is a ligand represented by any one of formulas (A) to (C). For reasons such as further reducing the stereohindrance of the ligand and making it easier to obtain a high external quantum efficiency, the second ligand is preferably a ligand represented by formula (A).

[Chemical formula 3]

In formula (A), ^XA1 and ^XA2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^A1 represents a alkyl group, and ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 ; in formula (B), ^XB1 and ^XB2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XB3 represents S, O or NH, L ^B1 and L ^B2 each independently represent a alkyl group, ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 ; in formula (C), ^XC1 to ^XC3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XC4 represents N, L ^C1 to L ^C3 independently represent a alkyl group, X ^C1 and X ^C4 are separated by 3 to 10 atoms by L ^C1 , X ^C2 and X ^C4 are separated by 1 to 10 atoms by L ^C2 , and X ^C3 and X ^C4 are separated by 1 to 10 atoms by L ^C3 .

The amino groups represented by ^XA1 , ^XA2 , ^XB1 , ^XB2 , ^XC1 , ^XC2 and ^XC3 are not limited to _-NH2 , but also include substituted amino groups and cyclic amino groups. Examples of substituted amino groups include monoalkylamino groups, dialkylamino groups, monoarylamino groups, diarylamino groups, alkylarylamino groups and the like. As the amino groups represented by these groups, _-NH2 , monoalkylamino groups and dialkylamino groups are preferred, and _-NH2 is more preferred.

In formula (A), at least one of ^XA1 and ^XA2 is preferably a thiol group, an amine group, a hydroxyl group or a carboxyl group, and a thiol group is more preferably. As a preferred combination of ^XA1 and ^XA2 , there can be cited a combination in which one of ^XA1 and ^XA2 is a thiol group and the other is a thiol group, an amine group, a hydroxyl group or a carboxyl group, and a combination in which one of ^XA1 and ^XA2 is an amine group and the other is a hydroxyl group or a carboxyl group. Among them, since the coordination force is high and it is easy to further reduce surface defects, the combination in which one of ^XA1 and ^XA2 is a thiol group and the other is a thiol group, an amine group, a hydroxyl group or a carboxyl group is preferred.

In formula (A), X ^A1 is preferably a group different from X ^A2 . According to this aspect, it is easy to coordinate more firmly to the semiconductor quantum dot, and the driving durability can be further improved. Furthermore, it is also easy to suppress the occurrence of film peeling and the like.

In formula (B), at least one of ^XB1 and ^XB2 is preferably a thiol group, an amine group, a hydroxyl group or a carboxyl group, more preferably a thiol group, an amine group or a hydroxyl group, and even more preferably an amine group. ^XB3 represents S, O or NH, preferably O or NH, and even more preferably NH.

In formula (C), at least one of ^XC1 to ^XC3 is preferably a thiol group, an amine group, a hydroxyl group or a carboxyl group, more preferably a thiol group, an amine group or a hydroxyl group, and even more preferably an amine group.

As the alkyl group represented by L ^A1 , L ^B1 , L ^B2 , L ^C1 , L ^C2 and L ^C3 , an aliphatic alkyl group is preferred. The aliphatic alkyl group may be a saturated aliphatic alkyl group or an unsaturated aliphatic alkyl group. In addition, in the alkyl groups represented by these groups, an oxygen atom, a sulfur atom or a nitrogen atom may be inserted between carbon atoms. The carbon number of the alkyl group represented by L ^A1 , L ^B1 and L ^C1 is preferably 3 to 20. The upper limit of the carbon number is preferably 10 or less, more preferably 6 or less, and further preferably 4 or less. The carbon number of the alkyl group represented by L ^B2 , L ^C2 and L ^C3 is preferably 1 to 20. The upper limit of the carbon number is preferably 10 or less, and more preferably 6 or less. The lower limit of the carbon number is preferably 2 or more, and more preferably 3 or more. Specific examples of the alkyl group represented by L ^A1 , L ^B1 , L ^B2 , L ^C1 , L ^C2 and L ^C3 include alkylene groups, alkenylene groups and alkynylene groups.

Examples of the alkylene group include straight chain alkylene groups, branched chain alkylene groups, and cyclic alkylene groups, and straight chain alkylene groups or branched chain alkylene groups are preferred, and straight chain alkylene groups are more preferred. Examples of the alkenylene group include straight chain alkenylene groups, branched chain alkenylene groups, and cyclic alkenylene groups, and straight chain alkenylene groups or branched chain alkenylene groups are preferred, and straight chain alkenylene groups are more preferred. Examples of the alkynylene group include straight chain alkynylene groups and branched chain alkynylene groups, and straight chain alkynylene groups are preferred. The alkylene group, alkenylene group, and alkynylene group may further have a substituent. The substituent group is preferably a group having 1 or more and 10 or less 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), alkenyl groups having 2 to 3 carbon atoms (vinyl and propenyl), alkynyl groups having 2 to 4 carbon atoms (ethynyl, propynyl, etc.), cyclopropyl, alkoxy groups having 1 to 2 carbon atoms (methoxy and ethoxy), acyl groups having 2 to 3 carbon atoms (acetyl and propionyl), alkoxycarbonyl groups having 2 to 3 carbon atoms (methoxycarbonyl and ethoxycarbonyl), acyloxy groups having 2 carbon atoms (acetyloxy and propionyl), yl], amide group with 2 carbon atoms [acetamido], hydroxyalkyl group with 1 to 3 carbon atoms [hydroxymethyl, hydroxyethyl, hydroxypropyl], aldehyde group, hydroxyl group, carboxyl group, sulfonic acid group, phospho group, aminoformyl group, cyano group, isocyanate group, thiol group, nitro group, nitroxy group, isothiocyanate group, cyanate group, thiocyanate group, acetoxy group, acetamido group, formyl group, formyloxy group, formamide group, sulfonic acid amide group, sulfinic acid group, sulfonamide group, phosphonyl group, acetyl group, halogen atom, alkali metal atom, etc.

In formula (A), ^XA1 and ^XA2 are separated by ^LA1 by 3 to 10 atoms, preferably by 3 to 6 atoms, and more preferably by 3 or 4 atoms.

In formula (B), ^XB1 and ^XB3 are separated by ^LB1 by 3 to 10 atoms, preferably by 3 to 6 atoms, and more preferably by 3 or 4 atoms. Furthermore, ^XB2 and ^XB3 are separated ^{by LB2} by 1 to 10 atoms, preferably by 1 to 6 atoms, and more preferably by 1 to 4 atoms. Furthermore, ^XB2 and ^XB3 are separated by ^LB2 by 3 to 10 atoms, preferably by 3 to 6 atoms, and more preferably by 3 or 4 atoms. Furthermore, in formula (B), the average value of the number of atoms separating ^XB1 and ^XB3 by ^LB1 and the number of atoms separating ^XB2 and ^XB3 by ^LB2 is preferably 3 to 10, more preferably 3 to 6, and more preferably 3 to 4.

In formula (C), X ^C1 and X ^C4 are separated by 3 to 10 atoms, preferably 3 to 6 atoms, and more preferably 3 or 4 atoms by L ^C1 . In addition, X ^C2 and X ^C4 are separated by 1 to 10 atoms, preferably 1 to 6 atoms, and more preferably 1 to 4 atoms by L ^C2 . In addition, X ^C2 and X ^C4 are separated by 3 to 10 atoms, preferably 3 to 6 atoms, and more preferably 3 or 4 atoms by L ^C2 . In addition, X ^C3 and X ^C4 are separated by 1 to 10 atoms, preferably 1 to 6 atoms, and more preferably 1 to 4 atoms by L ^C3 .

Furthermore, ^XC3 and ^XC4 are preferably separated by 3 to 10 atoms, 3 to 6 atoms, 3 atoms or 4 atoms by L ^C3 . Furthermore, in formula (C), the average of the number of atoms separated by L ^C1 between ^XC1 and ^XC4 , the number of atoms separated by L ^C2 between ^XC2 and ^XC4 , and the number of atoms separated by L ^C3 between ^XC3 and ^XC4 is preferably 3 to 10, more preferably 3 to 6, and even more preferably 3 to 4.

In addition, ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 , which means that the number of atoms constituting the shortest molecular chain connecting ^XA1 and ^XA2 is 3 to 10. For example, in any of the following formulas (A1) to (A3), ^XA1 and ^XA2 are separated by 3 atoms. The numbers indicated in the following structural formulas represent the arrangement order of the atoms constituting the shortest molecular chain connecting ^XA1 and ^XA2 .

[Chemical formula 4]

When describing the specific compound, 4-hydroxybutyric acid is a compound having a structure in which the position corresponding to X ^A1 is a thiol group, the position corresponding to X ^A2 is a carboxyl group, and the position corresponding to L ^A1 is a propyl group (a compound having the following structure). In 4-hydroxybutyric acid, X ^A1 (thiol group) and X ^A2 (carboxyl group) are separated by three atoms by L ^A1 (propyl group).

The meanings of X ^B1 and X ^B3 being separated by 3 to 10 atoms by L ^B1 , X ^B2 and X ^B3 being separated by 1 to 10 atoms by L ^B2 , X ^C1 and X ^C4 being separated by 3 to 10 atoms by L ^C1 , X ^C2 and X ^C4 being separated by 1 to 10 atoms by L ^C2 , and X ^C3 and X ^C4 being separated by 1 to 10 atoms by L ^C3 are the same as described above.

Specific examples of the second ligand include 4-butylbutyric acid, 3-aminopropanol, 3-butylpropanol, N-(3-aminopropyl)-1,3-propylenediamine, 3-(bis(3-aminopropyl)amino)propane-1-ol, 3-aminopropylphosphonic acid, and their derivatives. Among them, 4-butylbutyric acid and 3-butylpropanol are preferred, and 4-butylbutyric acid is more preferred because the effects of the present invention can be more significantly obtained.

The complex stability constant K1 of the second ligand relative to the metal atom contained in the semiconductor quantum dot is preferably 6 or more, more preferably 8 or more, and even more preferably 9 or more. If the above complex stability constant K1 is 6 or more, the strength of the bond between the semiconductor quantum dot and the second ligand can be increased. Therefore, the peeling of the second ligand from the semiconductor quantum dot can be suppressed, and as a result, the driving durability can be further improved.

The complex stability constant K1 refers to a constant determined by the relationship between the ligand and the metal atom that is the target of the coordination bond, and is represented by the following formula (b).

Complex stability constant K1=[ML]/([M]˙[L])......(b)

In formula (b), [ML] represents the molar concentration of the complex obtained by bonding the metal atom and the ligand, [M] represents the molar concentration of the metal atom contributing to the coordination bond, and [L] represents the molar concentration of the ligand.

In practice, multiple ligands are sometimes coordinated to one metal atom, but in the present invention, the complex stability constant K1 represented by formula (b) when one ligand molecule is coordinated to one metal atom is defined as an indicator of the strength of the coordination bond.

As a method for obtaining the complex stability constant K1 between a ligand and a metal atom, spectroscopy, magnetic resonance spectroscopy, potential method, solubility measurement, chromatography, calorimetry, freezing point measurement, vapor pressure measurement, relaxation measurement, viscosity measurement, surface tension measurement, etc. are known. In the present invention, the complex stability constant K1 was determined by using Sc-Databese ver.5.85 (Academic Software) (2010), which summarizes the results from research institutions using various methods. In the case where there is no complex stability constant K1 in Sc-Databese ver.5.85, the value described in Critical Stability Constants by A.E.Martell and R.M.Smith was used. If the complex stability constant K1 is not listed in Critical Stability Constants, the complex stability constant K1 is calculated using the measurement method described above or the PKAS method (A.E.Martell et al., The Determination and Use of Stability Constants, VCH (1988)) for calculating the complex stability constant K1.

In the present invention, a semiconductor quantum dot containing Pb atoms (preferably PbS) is used, and the complex stability constant K1 of the second ligand relative to the Pb atom is preferably 6 or more, 8 or more is more preferred, and 9 or more is further preferred.

[Other ligands]

The semiconductor film may also contain ligands other than the first ligand and the second ligand as ligands coordinated to the semiconductor quantum dots (hereinafter, also referred to as other ligands). As other ligands, for example, ligands represented by any one of the following formulas (D) to (F) can be cited.

In formula (D), ^XD1 and ^XD2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^D1 represents a alkyl group, and ^XD1 and ^XD2 are separated by 1 atom or 2 atoms by L ^D1 ; in formula (E), ^XE1 and ^XE2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XE3 represents S, O or NH, L ^E1 and L ^E2 each independently represent a alkyl group, ^XE1 and ^XE3 are separated by 1 atom or 2 atoms by L ^E1 , and ^XE2 and ^XE3 are separated by 1 atom or 2 atoms by L ^E2 ; in formula (F), ^XF1 to ^XF3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, and X ^F4 represents N, ^LF1 to ^LF3 independently represent a alkyl group, ^XF1 and ^XF4 are separated by ^LF1 by one or two atoms, ^XF2 and XF4 are separated by ^LF2 by one or two atoms, ^{and XF3} and ^XF4 are separated by ^LF3 by one or two atoms.

When the semiconductor film contains other ligands as ligands coordinated to the semiconductor quantum dots, the second ligand is preferably 50% by mass or more, 70% by mass or more, 80% by mass or more, and 90% by mass or more, relative to the total mass of the second ligand and the other ligands. In addition, it is not necessary to contain any of the ligands represented by the above formula (D), the ligand represented by the above formula (E), and the ligand represented by the above formula (E).

<Method for manufacturing semiconductor film>

The method for manufacturing a semiconductor film of the present invention comprises: a semiconductor quantum dot aggregate formation process, in which a semiconductor quantum dot dispersion liquid containing semiconductor quantum dots including metal atoms, a third ligand which is a ligand coordinated to the semiconductor quantum dots and different from a first ligand which is an inorganic halide and a second ligand represented by any one of formulas (A) to (C), and a solvent is provided on a substrate to form a semiconductor quantum dot aggregate film; and a ligand replacement process, in which a semiconductor quantum dot aggregate is formed by A film of semiconductor quantum dot aggregates formed by a process is provided with a ligand solution 1 comprising a first ligand as an inorganic halide and a solvent and a ligand solution 2 comprising a second ligand represented by any one of formulas (A) to (C) and a solvent, or a ligand solution 3 comprising a first ligand as an inorganic halide, a second ligand represented by any one of formulas (A) to (C) and a solvent, and the third ligand coordinated to the semiconductor quantum dot is replaced with the first ligand and the second ligand.

In the semiconductor film manufacturing method of the present invention, the semiconductor quantum dot aggregate formation process and the ligand replacement process can be repeated multiple times alternately. In addition, it can also include a rinsing process in which a rinsing liquid is brought into contact with the semiconductor quantum dot aggregate film for rinsing.

In the semiconductor film manufacturing method of the present invention, in the semiconductor quantum dot aggregate formation process, a semiconductor quantum dot dispersion liquid is applied to a substrate to form a semiconductor quantum dot aggregate film on the substrate. At this time, the semiconductor quantum dots are dispersed in the solvent by the third ligand, so the semiconductor quantum dots are not easy to form agglomerated blocks. Therefore, by applying the semiconductor quantum dot dispersion liquid to the substrate, the semiconductor quantum dot aggregate can be set to a structure in which each semiconductor quantum dot is arranged.

Next, by means of a ligand replacement process, a ligand solution 1 containing a first ligand and a solvent and a ligand solution 2 containing a second ligand and a solvent, or a ligand solution 3 containing a first ligand, a second ligand and a solvent is applied to the film of the semiconductor quantum dot aggregate, thereby performing a ligand replacement between the third ligand coordinated to the semiconductor quantum dot and the first ligand and the second ligand. Furthermore, by replacing the ligands, the semiconductor quantum dots can be brought closer to each other, the conductivity of the semiconductor quantum dot aggregate is improved, and a semiconductor film with a high photocurrent value and a high external quantum efficiency can be produced.

Below, each process is described in further detail.

(Semiconductor quantum dot cluster formation process)

In the semiconductor quantum dot aggregate formation process, a semiconductor quantum dot dispersion liquid containing semiconductor quantum dots including metal atoms, a third ligand coordinated to the semiconductor quantum dots, and a solvent is applied to a substrate to form a film of semiconductor quantum dot aggregates.

The semiconductor quantum dot dispersion can be applied on the surface of the substrate or on other layers provided on the substrate. Other layers provided on the substrate include adhesive layers and transparent conductive layers for improving the adhesion between the substrate and the semiconductor quantum dot aggregates.

The semiconductor quantum dot dispersion contains semiconductor quantum dots having metal atoms, a third ligand, and a solvent. The semiconductor quantum dot dispersion may also contain other components within the scope that does not impair the effect of the present invention.

The details of the semiconductor quantum dots containing metal atoms contained in the semiconductor quantum dot dispersion are as described above, and the preferred embodiment is the same. The content of the semiconductor quantum dots in the semiconductor quantum dot dispersion is preferably 1~500 mg/mL, more preferably 10~200 mg/mL, and further preferably 20~100 mg/mL. By making the content of the semiconductor quantum dots in the semiconductor quantum dot dispersion greater than 1 mg/mL, the density of the semiconductor quantum dots on the substrate becomes higher, and it is easy to obtain a good film. On the other hand, if the content of the semiconductor quantum dots is less than 500 mg/mL, the film thickness of the film obtained when the semiconductor quantum dot dispersion is applied once is not easy to increase. Therefore, in the ligand replacement process of the next process, the ligand replacement of the third ligand coordinated to the semiconductor quantum dots existing in the film can be fully carried out.

The third ligand contained in the semiconductor quantum dot dispersion liquid acts as a ligand coordinated to the semiconductor quantum dots, and has a molecular structure that easily becomes a stereo hindrance. It is preferred that it also acts as a dispersant that disperses the semiconductor quantum dots in the solvent.

From the viewpoint of improving the dispersibility of semiconductor quantum dots, the third ligand is preferably a ligand having at least 6 carbon atoms in the main chain, and more preferably a ligand having at least 10 carbon atoms in the main chain. The third ligand may be a saturated compound or an unsaturated compound. Specific examples of the third ligand include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, oleylamine, dodecylamine, dodecylamine, 1,2-hexadecylmercaptan, trioctylphosphine oxide, and cetrimonium bromide. The third ligand is preferably one that is not likely to remain in the semiconductor film after it is formed. Specifically, a smaller molecular weight is preferred. From the perspective of making semiconductor quantum dots dispersed stably and not easily remaining in the semiconductor film, oleic acid and oleylamine are preferred as the third ligand.

Relative to the total volume of the semiconductor quantum dot dispersion, the content of the third ligand in the semiconductor quantum dot dispersion is preferably 0.1mmol/L~500mmol/L, and more preferably 0.5mmol/L~100mmol/L.

The solvent contained in the semiconductor quantum dot dispersion is not particularly limited, but a solvent that does not easily dissolve the semiconductor quantum dots and easily dissolves the third ligand is preferred. As a solvent, an organic solvent is preferred. As specific examples, alkanes [n-hexane, n-octane, etc.], benzene, toluene, etc. can be cited. The solvent contained in the semiconductor quantum dot dispersion can be only one type, or a mixed solvent obtained by mixing two or more types.

The solvent contained in the semiconductor quantum dot dispersion is preferably a solvent that is not easy to remain in the formed semiconductor film. If it is a solvent with a relatively low boiling point, the content of residual organic matter can be suppressed when the semiconductor film is finally obtained. In addition, as a solvent, it is better to have good wettability to the substrate. For example, when applying the semiconductor quantum dot dispersion on a glass substrate, the solvent is preferably an alkane such as hexane and octane.

Relative to the total mass of the semiconductor quantum dot dispersion, the content of the solvent in the semiconductor quantum dot dispersion is preferably 50 mass% to 99 mass%, more preferably 70 mass% to 99 mass%, and even more preferably 90 mass% to 98 mass%.

The semiconductor quantum dot dispersion is applied to the substrate. There are no special restrictions on the shape, structure, size, etc. of the substrate, and it can be appropriately selected according to the purpose. The structure of the substrate can be a single-layer structure or a multilayer structure. As a substrate, for example, a substrate composed of inorganic materials such as glass, YSZ (Yttria-Stabilized Zirconia: yttria-stabilized zirconia; yttria-stabilized zirconia), resin, resin composite materials, etc. can be used. In addition, electrodes, insulating films, etc. can be formed on the substrate. At this time, the semiconductor quantum dot dispersion is applied to the electrodes and insulating films on the substrate.

The method for applying the semiconductor quantum dot dispersion liquid to the substrate is not particularly limited. Examples of coating methods include spin coating, immersion, inkjet, dripping, screen printing, letterpress printing, gravure printing, and spray coating.

The film thickness of the semiconductor quantum dot aggregate film formed by the semiconductor quantum dot aggregate formation process is preferably 3 nm or more, more preferably 10 nm or more, and more preferably 30 nm or more. The upper limit is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less.

(Ligand replacement process)

In the ligand replacement process, a ligand solution 1 containing a first ligand and a solvent and a ligand solution 2 containing a second ligand and a solvent are applied to a film of a semiconductor quantum dot aggregate formed by a semiconductor quantum dot aggregate formation process, or a ligand solution 3 containing a first ligand, a second ligand, and a solvent is applied to replace the third ligand coordinated to the semiconductor quantum dot with the first ligand and the second ligand.

The details of the first ligand contained in the ligand solution 1 and the ligand solution 3, and the second ligand contained in the ligand solution 2 and the ligand solution 3 are as described above, and the preferred embodiments are also the same.

Furthermore, the complex stability constant K1 of the second ligand with respect to the metal atom contained in the semiconductor quantum dot is preferably 6 or more, more preferably 8 or more, and even more preferably 9 or more. If the complex stability constant K1 is 6 or more, the ligand replacement of the third ligand and the second ligand can be performed quickly, and even if the film thickness of the semiconductor quantum dot aggregate film formed by the semiconductor quantum dot aggregate formation process is large, the ligand replacement can be performed sufficiently to the bottom side of the film. Therefore, usually, the semiconductor quantum dot cluster formation process and the ligand replacement process are repeated multiple times to form a semiconductor film of the desired film thickness. However, even if the film thickness formed in each cycle is large, the ligand replacement can be fully performed until the bottom side of the film, so the contact time when manufacturing a semiconductor film of the desired film thickness can be shortened. In addition, if the above-mentioned complex stability constant K1 is 6 or more, the second ligand can be firmly coordinated to the semiconductor quantum dot, which can further improve the conductivity, photocurrent value, external quantum efficiency, and in-plane uniformity of the external quantum efficiency of the semiconductor film.

In the semiconductor quantum dot aggregate formation process, when a film of semiconductor quantum dot aggregates with a thickness of 30 nm or more is formed, the complex stability constant K1 of the second ligand relative to the metal atoms contained in the semiconductor quantum dots is preferably 6 or more, 8 or more is more preferably, and 9 or more is further preferably. In addition, when a semiconductor quantum dot containing Pb atoms is used (preferably when PbS is used), the complex stability constant K1 of the second ligand relative to the Pb atoms is preferably 6 or more, 8 or more is more preferably, and 9 or more is further preferably.

The content of the first ligand contained in the ligand solution 1 and the ligand solution 3 is preferably 1mmol/L~500mmol/L, more preferably 5mmol/L~100mmol/L, and even more preferably 10mmol/L~50mmol/L.

The content of the second ligand contained in the ligand solution 2 and the ligand solution 3 is preferably 0.001v/v%~5v/v%, more preferably 0.002v/v%~1v/v%, and even more preferably 0.005v/v%~0.1v /v%.

Regarding the solvents contained in the ligand solution 1, the ligand solution 2, and the ligand solution 3, it is preferred to appropriately select the solvents according to the types of ligands contained in each ligand solution, and a solvent that easily dissolves each ligand is preferred. In addition, 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.

In addition, the solvent contained in the ligand solution is preferably a solvent that is not easy to remain in the formed semiconductor film. From the perspective of easy drying and easy removal by washing, low-boiling alcohols, ketones, and nitriles are preferred, and methanol, ethanol, acetone, or acetonitrile is more preferred. The solvent contained in the ligand solution is preferably not mixed with the solvent contained in the semiconductor quantum dot dispersion. As a preferred combination of solvents, when the solvent contained in the semiconductor quantum dot dispersion is an alkane such as hexane or octane, it is preferred that the solvent contained in the ligand solution is a polar solvent such as methanol or acetone.

The content of solvent in the ligand solution is the remainder obtained by subtracting the content of ligand from the total mass of the ligand solution.

The method of imparting the ligand solution to the semiconductor quantum dot aggregate is the same as the method of imparting the semiconductor quantum dot dispersion to the substrate, and the preferred embodiment is also the same.

(Rinsing process)

The method for manufacturing the semiconductor film of the present invention may include a rinsing process for rinsing by bringing a rinsing liquid into contact with the film of the semiconductor quantum dot aggregate. By including the rinsing process, it is possible to remove excess ligands contained in the film and ligands separated from the semiconductor quantum dots. In addition, it is possible to remove residual solvents and other impurities. For the rinsing liquid, it is also possible to use a solvent or a ligand solution contained in a semiconductor quantum dot dispersion liquid. However, a non-protonic solvent is preferred, and a non-protonic polar solvent is more preferred, because it is easy to more effectively remove excess ligands contained in the film and ligands separated from the semiconductor quantum dots, and it is easy to uniformly maintain the film surface by rearranging the quantum dot surface. For the reason that it is easy to remove after the film is formed, the boiling point of the rinse liquid is preferably below 120°C, more preferably below 100°C, and more preferably below 90°C. For the reason that unnecessary concentration during operation can be avoided, the boiling point of the rinse liquid is preferably above 30°C, more preferably above 40°C, and more preferably above 50°C. From the above content, the boiling point of the rinse liquid is preferably 50~90°C. As specific examples of aprotic solvents, acetonitrile, acetone, dimethylformamide, and dimethyl sulfoxide can be cited. For the reason that they have low boiling points and are not easily retained in the film, acetonitrile and acetone are preferred.

In the rinsing process, a rinsing liquid may be injected into the film of the semiconductor quantum dot aggregate, or the film of the semiconductor quantum dot aggregate may be immersed in the rinsing liquid. Furthermore, the rinsing process may be performed after the semiconductor quantum dot aggregate formation process or after the ligand replacement process. Furthermore, the rinsing process may be performed after repeatedly performing a combination of the semiconductor quantum dot aggregate formation process and the ligand replacement process.

The solvent used in the semiconductor quantum dot aggregate formation process, ligand replacement process, and rinsing process preferably has less metal impurities, and the metal content is, for example, 10 ppb (parts per billion) or less. If necessary, a ppt (parts per trillion) level solvent can be used, such as provided by Toyo Gosei Co., Ltd. (Chemical Industry Daily, November 13, 2015). As a method for removing impurities such as metals from the solvent, for example, distillation (molecular distillation or thin film distillation, etc.) or filtration using a filter can be cited. The pore size of the filter used in the filtration is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. The material of the filter is preferably polytetrafluoroethylene, polyethylene or nylon. In addition, the solvent may contain isomers (compounds with the same atomic number but different structures), and the isomers may contain only one type or multiple types.

(Drying process)

The semiconductor film manufacturing method of the present invention may have a drying process. The drying process may be a dispersion drying process for drying and removing the solvent remaining in the semiconductor quantum dot aggregate film after the semiconductor quantum dot aggregate formation process, or a solution drying process for drying the ligand solution after the ligand replacement process. Furthermore, it may be a comprehensive process performed after repeatedly performing a combination of a semiconductor quantum dot aggregate formation process and a ligand replacement process.

By going through the above-described processes, a semiconductor film can be formed on a substrate. The obtained semiconductor film has excellent driving durability.

<Photoelectric conversion element>

The photoelectric conversion element of the present invention includes the semiconductor film of the present invention as described above. It is more preferred to include the semiconductor film of the present invention as a photoelectric conversion layer.

The thickness of the semiconductor film of the present invention in the photoelectric conversion element is preferably 10nm~600nm, more preferably 50nm~600nm, more preferably 100nm~600nm, and more preferably 150nm~600nm. The upper limit of the thickness is preferably 550nm or less, more preferably 500nm or less, and more preferably 450nm or less.

As the type of photoelectric conversion element, there can be cited light detection elements such as sensors, photovoltaic elements such as solar cells, etc. As for the semiconductor film of the present invention, the in-plane uniformity of the external quantum efficiency is excellent, so it is particularly effective when used as a light detection element. That is, in a light detection element, if there is a lot of in-plane non-uniformity in the external quantum efficiency, it becomes a cause of noise, for example, in the case of an image sensor, it sometimes causes the quality of the acquired image to deteriorate, and the function as a sensor is easily reduced. Therefore, this is because the in-plane uniformity of the external quantum efficiency is particularly required to be high in the light detection element. As the type of light detection element, there can be cited a photoconductor type light detection element and a photodiode type light detection element. Among them, photodiode-type photodetection elements are preferred because they can easily achieve a high signal-to-noise ratio (SN ratio).

Furthermore, the semiconductor film of the present invention also has excellent sensitivity to light of wavelengths in the infrared region, so the photoelectric conversion element of the present invention can be preferably used as a light detection element for detecting light of wavelengths in the infrared region. That is, the photoelectric conversion element of the present invention can be preferably used as an infrared light detection element.

The wavelength of the infrared region light is preferably light with a wavelength exceeding 700nm, more preferably light with a wavelength exceeding 800nm, and even more preferably light with a wavelength exceeding 900nm. Furthermore, the wavelength of the infrared region light is preferably light with a wavelength below 2000nm, and even more preferably light with a wavelength below 1600nm.

The photoelectric conversion element can be a light detection element that 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 400nm to 700nm).

FIG1 shows an embodiment of a photodiode-type light detection element. In addition, the arrow in the figure indicates incident light on the light detection element. The light detection element 1 shown in FIG1 includes a lower electrode 12, an upper electrode 11 opposite to the lower electrode 12, and a photoelectric conversion layer 13 disposed between the lower electrode 12 and the upper electrode 11. The light detection element 1 shown in FIG1 is used by incident light from above the upper electrode 11.

The photoelectric conversion layer 13 is composed of the semiconductor film of the present invention described above.

The refractive index of the photoelectric conversion layer 13 relative to the target wavelength of light detected by the photodetection element is preferably 2.0-3.0, more preferably 2.1-2.8, and even more preferably 2.2-2.7. In this manner, when the photodetection element is set to a photodiode structure, it is easy to achieve high light absorption rate, that is, high external quantum efficiency.

The thickness of the photoelectric conversion layer 13 is preferably 10nm~600nm, more preferably 50nm~600nm, further preferably 100nm~600nm, and further preferably 150nm~600nm. The upper limit of the thickness is preferably below 550nm, more preferably below 500nm, and further preferably below 450nm.

It is preferred that the wavelength λ of the target light detected by the light detection element and the optical path length ^Lλ of the light of the wavelength λ from the surface 12a on the photoelectric conversion layer 13 side of the lower electrode 12 to the surface 13a on the upper electrode side of the photoelectric conversion layer 13 satisfy the relationship of the following formula (1-1), and it is more preferred that the wavelength λ and the optical path length ^Lλ satisfy the relationship of the following formula (1-2). When the wavelength λ and the optical path length Lλ satisfy this relationship, the phases of the light incident from the upper electrode 11 side (incident light) and the light reflected from the surface of the lower electrode 12 (reflected light) can be aligned in the photoelectric conversion layer 13, and as a result, the light mutually reinforces each other by the optical interference effect, and a higher external quantum efficiency can be obtained.

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)

In the above formula, λ is the wavelength of the target light detected by the light detection element, ^Lλ is the optical path length of light of wavelength λ from the surface 12a on the photoelectric conversion layer 13 side of the lower electrode 12 to the surface 13a on the upper electrode side of the photoelectric conversion layer 13, and m is an integer greater than 0.

m is preferably an integer between 0 and 4, more preferably an integer between 0 and 3, still more preferably an integer between 0 and 2, and particularly preferably 0 or 1.

Here, the optical path length is obtained by multiplying the physical thickness of the substance through which light is transmitted by the refractive index. For example, if the photoelectric conversion layer 13 is used for explanation, and the thickness of the photoelectric conversion layer is d ¹ and the refractive index of the photoelectric conversion layer with respect to the wavelength λ ¹ is N ¹ , the optical path length of the light of wavelength λ ¹ transmitted through the photoelectric conversion layer 13 is N ¹ ×d ^1. When the photoelectric conversion layer 13 is composed of two or more laminated films and an intermediate layer described later is present between the photoelectric conversion layer 13 and the lower electrode 12, the cumulative value of the optical path lengths of the layers is the above optical path length L ^λ .

The upper electrode 11 is preferably a transparent electrode formed of a conductive material that is substantially transparent to the wavelength of the target light detected by the light detection element. In addition, in the present invention, "substantially transparent" means that the light transmittance is 50% or more, preferably 60% or more, and particularly preferably 80% or more. As materials for the upper electrode 11, conductive metal oxides and the like can be cited. As specific examples, tin oxide, zinc oxide, indium oxide, indium tungsten oxide, indium zinc oxide (indium zinc oxide: IZO), indium tin oxide (indium tin oxide: ITO), fluorine-doped tin oxide (fluorine-doped tin oxide: FTO), etc. can be cited.

The film thickness of the upper electrode 11 is not particularly limited, and 0.01μm~100μm is preferred, 0.01μm~10μm is further preferred, and 0.01μm~1μm is particularly preferred. In addition, in the present invention, the film thickness of each layer can be measured by observing the cross section of the light detection element 1 using a scanning electron microscope (SEM) or the like.

As materials for forming the lower electrode 12, for example, metals such as platinum, gold, nickel, copper, silver, indium, ruthenium, palladium, rhodium, iridium, nb, aluminum, the above-mentioned conductive metal oxides, carbon materials, and conductive polymers can be cited. As carbon materials, materials with conductivity can be cited, for example, fullerene, carbon nanotubes, graphite, graphene, etc.

As the lower electrode 12, a thin film of metal or conductive metal oxide (including a thin film formed by evaporation), or a glass substrate or plastic substrate having the thin film is preferred. As the glass substrate or plastic substrate, glass having a thin film of gold or platinum, or glass evaporated with platinum is preferred. The film thickness of the lower electrode 12 is not particularly limited, and 0.01μm~100μm is preferred, 0.01μm~10μm is further preferred, and 0.01μm~1μm is particularly preferred.

In addition, although not shown, a transparent substrate may be arranged on the surface of the light incident side of the upper electrode 11 (the surface opposite to the photoelectric conversion layer 13 side). Examples of the transparent substrate include a glass substrate, a resin substrate, and a ceramic substrate.

Although not shown, an intermediate layer may be provided between the photoelectric conversion layer 13 and the lower electrode 12 and/or between the photoelectric conversion layer 13 and the upper electrode 11. Examples of the intermediate layer include a blocking layer, an electron transport layer, and a hole transport layer. As a preferred embodiment, a hole transport layer may be provided between the photoelectric conversion layer 13 and the lower electrode 12 and between the photoelectric conversion layer 13 and the upper electrode 11. It is more preferable to have an electron transport layer between the photoelectric conversion layer 13 and the lower electrode 12 and between the photoelectric conversion layer 13 and the upper electrode 11, and to have a hole transport layer on the other side. The hole transport layer and the electron transport layer may be a single layer film or a multilayer film of two or more layers.

The blocking layer is a layer that has the function of preventing reverse current. The blocking layer is also called an anti-short circuit layer. As for the materials forming the blocking layer, for example, silicon oxide, magnesium oxide, aluminum oxide, calcium carbonate, cesium carbonate, polyvinyl alcohol, polyurethane, titanium oxide, tin oxide, zinc oxide, niobium oxide, tungsten oxide, etc. can be cited. The blocking layer can be a single layer film or a multilayer film of two or more layers.

The electron transport layer is a layer having a function of transporting electrons generated in the photoelectric conversion layer 13 to the upper electrode 11 or the lower electrode 12. The electron transport layer is also called a hole blocking layer. The electron transport layer is formed of an electron transport material capable of performing this function. Examples of the electron transport material include fullerene compounds such as [6,6]-phenyl-C61-butyric acid methyl ester (PC ₆₁ BM), perylene compounds such as perylene tetracarboxylic diimide, tetracyanoquinodimethane, titanium oxide, tin oxide, zinc oxide, indium oxide, indium tungsten oxide, indium zinc oxide, indium tin oxide, fluorine-doped tin oxide, etc. The electron transport layer may be a single layer film or a laminated film of two or more layers.

The hole transport layer is a layer having the function of transporting holes generated in the photoelectric conversion layer 13 to the upper electrode 11 or the lower electrode 12. The hole transport layer is also called an electron blocking layer. The hole transport layer is formed of a hole transport material that can exert this function. For example, PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid)), MoO ₃ , etc. can be cited. In addition, organic hole transport materials described in paragraphs 0209 to 0212 of Japanese Patent Gazette No. 2001-291534 can also be used. In addition, semiconductor quantum dots can also be used in the hole transport material. As semiconductor quantum dot materials constituting semiconductor quantum dots, for example, nanoparticles (0.5 nm or more and less than 100 nm) of general semiconductor crystals [a) Group IV semiconductors, b) Group IV-IV, Group III-V or Group II-VI compound semiconductors, c) compound semiconductors containing a combination of three or more elements from Group II, Group III, Group IV, Group V and Group VI] can be cited. Specifically, semiconductor materials with relatively narrow band gaps such as PbS, PbSe, PbSeS, InN, InAs, Ge, InAs, InGaAs, CuInS, CuInSe, CuInGaSe, InSb, HgTe, HgCdTe, Ag2S, Ag2Se, Ag2Te, SnS, SnSe, SnTe, Si, InP can be cited. The ligand can be coordinated to the surface of the semiconductor quantum dot.

<Image sensor>

The photoelectric conversion device of the present invention includes the above-mentioned photoelectric conversion element of the present invention. The photoelectric conversion element of the present invention also has excellent sensitivity to light with wavelengths in the infrared region, so it can be used particularly well as an infrared image sensor.

The structure of the image sensor is not particularly limited as long as it has the photoelectric conversion element of the present invention and functions as an image sensor.

The image sensor may include an infrared transmission filter. As an infrared transmission filter, the one with low transmittance of light in the wavelength band of the visible region is preferred, and the average transmittance of light in the wavelength range of 400nm to 650nm is preferably below 10%, more preferably below 7.5%, and particularly preferably below 5%.

As the infrared transmission filter layer, there can be cited those composed of a resin film containing a color material. As the color material, there can be cited red color material, green color material, blue color material, yellow color material, purple color material, orange color material and other color materials, and black color material. It is preferred that the color material contained in the infrared transmission filter layer forms black with a combination of two or more color materials, or contains a black color material. As a combination of color materials when forming black with a combination of two or more color materials, for example, the following (C1) to (C7) can be cited.

(C1) A state containing red color material and blue color material.

(C2) A state containing red color material, blue color material and yellow color material.

(C3) A state containing red color material, blue color material, yellow color material and purple color material.

(C4) A pattern containing red color material, blue color material, yellow color material, purple color material and green color material.

(C5) A pattern containing red color material, blue color material, yellow color material and green color material.

(C6) A pattern containing red, blue and green color materials.

(C7) Contains yellow color material and purple color material.

The color material can be a pigment or a dye. It can contain pigments and dyes. The black color material is preferably an organic black color material. For example, as an organic black color material, bisbenzofuranone compounds, azomethine compounds, perylene compounds, azo compounds, etc. can be cited.

The infrared transmission filter may also contain an infrared absorber. By including an infrared absorber in the infrared transmission filter, the wavelength of the transmitted light can be shifted to a longer wavelength side. Examples of infrared absorbers include pyrrolopyrrole compounds, cyanine compounds, squarylium compounds, phthalocyanine compounds, naphthalocyanine compounds, quartylene compounds, merocyanine compounds, crotonium compounds, oxocyanine compounds, ammonium compounds, dithiol compounds, triarylmethane compounds, pyrromethene compounds, azomethine compounds, anthraquinone compounds, dibenzofuranone compounds, dithiol-ene metal complexes, metal oxides, metal borides, and the like.

The spectral characteristics of the infrared transmission filter can be appropriately selected according to the purpose of the image sensor. For example, a filter that satisfies any of the following spectral characteristics (1) to (5) can be cited.

(1): A filter layer whose maximum value of the transmittance of light in the thickness direction of the film within the wavelength range of 400nm~750nm is less than 20% (preferably less than 15%, more preferably less than 10%), and whose minimum value of the transmittance of light in the thickness direction of the film within the wavelength range of 900nm~1500nm is more than 70% (preferably more than 75%, more preferably more than 80%).

(2): A filter layer whose maximum value of the transmittance of light in the thickness direction of the film within the wavelength range of 400nm~830nm is less than 20% (preferably less than 15%, more preferably less than 10%), and whose minimum value of the transmittance of light in the thickness direction of the film within the wavelength range of 1000nm~1500nm is more than 70% (preferably more than 75%, more preferably more than 80%).

(3): A filter layer whose maximum value of the transmittance of light in the thickness direction of the film within the wavelength range of 400nm~950nm is less than 20% (preferably less than 15%, more preferably less than 10%), and whose minimum value of the transmittance of light in the thickness direction of the film within the wavelength range of 1100nm~1500nm is more than 70% (preferably more than 75%, more preferably more than 80%).

(4): A filter layer whose maximum value of light transmittance in the thickness direction of the film within the wavelength range of 400nm to 1100nm is less than 20% (preferably less than 15%, more preferably less than 10%), and whose minimum value within the wavelength range of 1400nm to 1500nm is more than 70% (preferably more than 75%, more preferably more than 80%).

(5): A filter layer whose maximum value of light transmittance in the thickness direction of the film within the wavelength range of 400nm to 1300nm is less than 20% (preferably less than 15%, more preferably less than 10%), and whose minimum value within the wavelength range of 1600nm to 2000nm is more than 70% (preferably more than 75%, more preferably more than 80%).

Furthermore, as an infrared transmission filter, films described in Japanese Patent Publication No. 2013-077009, Japanese Patent Publication No. 2014-130173, Japanese Patent Publication No. 2014-130338, International Publication No. 2015/166779, International Publication No. 2016/178346, International Publication No. 2016/190162, International Publication No. 2018/016232, Japanese Patent Publication No. 2016-177079, Japanese Patent Publication No. 2014-130332, and International Publication No. 2016/027798 can be used. Infrared transmission filters can be used by combining two or more filters, or by using a double-pass filter that transmits two or more specific wavelength regions with one filter.

In order to improve various performances such as noise reduction, the image sensor of the present invention may include an infrared shielding filter. As specific examples of infrared shielding filters, for example, filters described in International Publication No. 2016/186050, International Publication No. 2016/035695, Japanese Patent No. 6248945, International Publication No. 2019/021767, Japanese Patent Publication No. 2017-067963, and Japanese Patent No. 6506529 can be cited.

The image sensor of the present invention may include a dielectric multilayer film. As a dielectric multilayer film, there can be cited a film obtained by alternately laminating a plurality of layers of dielectric thin films with a high refractive index (high refractive index material layer) and dielectric thin films with a low refractive index (low refractive index material layer). The number of layers of dielectric thin films in the dielectric multilayer film is not particularly limited, but 2 to 100 layers are preferred, 4 to 60 layers are more preferred, and 6 to 40 layers are further preferred. As a material used to form the high refractive index material layer, a material with a refractive index of 1.7 to 2.5 is preferred. Specific examples include _Sb2O3 , _Sb2S3 , _Bi2O3 , _CeO2 , CeF3 _{, HfO2} , _La2O3 , _Nd2O3 , _{Pr6O11 , Sc2O3} , SiO, _Ta2O5 , _TiO2 , _TlCl , _Y2O3 , _ZnSe , _ZnS , _{ZrO2 , etc.} As the material used for forming the low refractive index material layer, _a material having _{a refractive} index of 1.2 to 1.6 is preferred. Specific examples include _Al2O3 , _BiF3 , _CaF2 , _LaF3 , _PbCl2 , _PbF2 , LiF, _MgF2 , MgO, _NdF3 , _SiO2 , _Si2O3 , NaF, _ThO2 , _ThF4 , _Na3AlF6 , etc. The method for forming the dielectric multilayer film is not particularly limited, but examples thereof include ion plating, vacuum evaporation methods such as _ion beam, physical vapor deposition methods ₍ PVD methods) such _as sputtering, and chemical vapor deposition methods (CVD methods). When the wavelength of light to be shielded is λ (nm), the thickness of each layer of the high refractive index material layer and the low refractive index material layer is preferably 0.1λ~0.5λ. As a specific example of the dielectric multilayer film, for example, the film described in Japanese Patent Publication No. 2014-130344 and Japanese Patent Publication No. 2018-010296 can be used.

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 further 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 further preferably 90% or more. Furthermore, the maximum transmittance in the light-shielding wavelength band is preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. Furthermore, the average transmittance in the transmission wavelength band is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. In addition, when the wavelength showing maximum transmittance is set to the central wavelength λ _t1 , the wavelength range of the transmission wavelength band is preferably the central wavelength λ _t1 ± 100nm, more preferably the central wavelength λ _t1 ± 75nm, and even more preferably the central wavelength λ _t1 ± 50nm.

The dielectric multilayer film may have only one transmission wavelength band (preferably a transmission wavelength band with a maximum transmittance of more than 90%), or may have multiple transmission wavelength bands.

The image sensor of the present invention may include a color separation filter layer. As a color separation filter layer, a filter layer including colored pixels can be cited. As the type of colored pixels, red pixels, green pixels, blue pixels, yellow pixels, cyan pixels, and magenta pixels can be cited. The color separation filter layer can include colored pixels of more than two colors, or only one color. It can be appropriately selected according to the use and purpose. For example, the filter described in International Publication No. 2019/039172 can be used.

Furthermore, when the color separation layer includes colored pixels of two or more colors, the colored pixels of each color may be adjacent to each other, or a partition wall may be provided between each colored pixel. There is no particular limitation on the material of the partition wall. For example, organic materials such as silicone resins and fluororesins, and inorganic particles such as silica particles may be cited. Furthermore, the partition wall may be made of metals such as tungsten and aluminum.

In addition, when the image sensor of the present invention includes an infrared transmission filter layer and a color separation layer, it is preferred that the color separation layer is disposed on a different optical path from the infrared transmission filter layer. Furthermore, it is also preferred that the infrared transmission filter layer and the color separation layer are two-dimensionally arranged. In addition, the infrared transmission filter layer and the color separation layer are two-dimensionally arranged means that at least a part of the two exist on the same plane.

The image sensor of the present invention may include a planarization layer, a base layer, an intermediate layer such as an adhesive layer, an anti-reflection film, and a lens. As an anti-reflection film, for example, a film made of a composition described in International Publication No. 2019/017280 can be used. As a lens, for example, a structure described in International Publication No. 2018/092600 can be used.

The image sensor of the present invention can be preferably used as an infrared image sensor. Moreover, the image sensor of the present invention can be preferably used as a sensor for sensing light with a wavelength of 900nm to 2000nm, and can be more preferably used as a sensor for sensing light with a wavelength of 900nm to 1600nm.

[Implementation example]

The following examples are given to further illustrate the present invention. The materials, usage amounts, proportions, processing contents, processing sequences, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the purpose of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Implementation Example 1, Comparative Example 1>

A precursor solution was obtained by weighing 22.5 mL of oleic acid, 2 mmol of lead oxide and 19 mL of octadecene in a flask and heating it at 110°C for 90 minutes under vacuum. Then, the temperature of the solution was adjusted to 95°C, and the system was set to a nitrogen flow state. Next, 1 mmol of hexamethyldisilasulfane was injected together with 5 mL of octadecene. Immediately after the injection, the flask was naturally cooled, and 12 mL of hexane was added at a stage of 30°C to recover the solution. Excess ethanol was added to the solution, and centrifugal separation was performed at 10,000 rpm for 10 minutes to disperse the precipitate in octane, and a dispersion of PbS quantum dots with oleic acid as a ligand coordinated to the surface of the PbS quantum dots was obtained (concentration of 40 mg/mL). The band gap of PbS quantum dots estimated from the absorption measurement of the obtained PbS quantum dot dispersion is about 0.80 eV. Samples 1 and 2 were prepared using the obtained PbS quantum dot dispersion by the following method.

(Preparation of test specimen 1)

As a substrate, a substrate having 65 pairs of comb-shaped platinum electrodes as shown in Figure 2 on quartz glass was prepared. The comb-shaped platinum electrodes used were comb-shaped electrodes manufactured by BAS (model 012126, electrode spacing 5μm).

The dispersion of PbS quantum dots was dripped onto the above substrate and spun at 2500 rpm to form a PbS quantum dot aggregate film (Process 1). Then, a methanol solution of the specific ligand 1 listed in the following table (concentration of 25 mmol/L) i.e., the first ligand solution and a methanol solution of the specific ligand 2 listed in the following table (concentration of 0.01 v/v%) i.e., the second ligand solution were dripped onto the PbS quantum dot aggregate film, and then left to stand for 10 seconds and spun dried at 2500 rpm for 10 seconds. Then, by dripping methanol as a rinse solution onto the PbS quantum dot aggregate film and spun dried at 2500 rpm for 20 seconds, the ligand coordinated to the PbS quantum dots was replaced from oleic acid to specific ligand 1 and specific ligand 2 (Process 2). The operation of process 1 and process 2 as one cycle was repeated for 10 cycles, and a PbS quantum dot aggregate film, i.e., a semiconductor film, in which the ligand was changed from oleic acid to specific ligand 1 and specific ligand 2 was formed with a thickness of 180nm, thereby producing a test piece 1. The thickness of the PbS quantum dot aggregate film formed in each cycle was about 18nm.

(Production of Test Specimen 2)

A titanium oxide film was formed on a quartz glass substrate with a fluorine-doped tin oxide film by sputtering at 50 nm. Then, a dispersion of PbS quantum dots was dripped onto the titanium oxide film formed on the above substrate and spun at 2500 rpm to form a PbS quantum dot aggregate film (process 1). Then, a methanol solution of the specific ligand 1 listed in the following table (concentration of 25 mmol/L), i.e., the first ligand solution, and a methanol solution of the specific ligand 2 listed in the following table (concentration of 0.01 v/v%), i.e., the second ligand solution, were dripped onto the PbS quantum dot aggregate film, and then left to stand for 10 seconds and spun dried at 2500 rpm for 10 seconds. Next, by dripping methanol as a rinse liquid onto the PbS quantum dot aggregate film and rotating it at 2500 rpm for 20 seconds, the ligand coordinated to the PbS quantum dots was replaced from oleic acid to specific ligand 1 and specific ligand 2 (process 2). The operation of process 1 and process 2 as one cycle was repeated for 10 cycles, and a PbS quantum dot aggregate film, i.e., a photoelectric conversion layer, in which the ligand was replaced from oleic acid to specific ligand 1 and specific ligand 2, was formed with a thickness of 180 nm. The thickness of the PbS quantum dot aggregate film formed in each cycle was about 18 nm.

Next, 50nm of molybdenum oxide and 100nm of gold were successively evaporated on the photoelectric conversion layer to produce the test piece 2 as a photodiode type light detection element.

(Conductivity and photocurrent value)

Regarding the test piece 1 prepared above, the conductivity and photocurrent value of the semiconductor film were measured using a semiconductor parameter analyzer (C4156, manufactured by Agilent).

That is, regarding the conductivity, +5V was applied to the electrode without irradiating light to the sample 1, and the conductivity of the semiconductor film was measured by obtaining the current value. Regarding the photocurrent value, the photocurrent value was measured and evaluated in the state where monochromatic light with a wavelength of 1550nm (irradiation intensity 40μW/ ^cm2 ) was irradiated to the sample 1. For light irradiation, a monochromatic light source system MLS-1510 (manufactured by Asahi Spectra Co., Ltd.) was used.

(External quantum efficiency and drive durability)

The external quantum efficiency and driving durability were evaluated using the test specimen 2 prepared above.

That is, the external quantum efficiency (EQE) was measured when the sample 2 was irradiated with monochromatic light of a wavelength of 1550nm (irradiation intensity of 40μW/ ^cm2 ) while a reverse voltage of 2V was applied to the sample 2. The external quantum efficiency (EQE) is calculated by subtracting the current value in the state of non-irradiation from the current value in the state of irradiation. The value of the external quantum efficiency (EQE) is obtained by dividing the number of electrons generated by light irradiation by the number of photons of the irradiated light.

In addition, regarding the driving durability, the external quantum efficiency reduction rate (the value of the external quantum efficiency measured at the first time - the value of the external quantum efficiency measured at the 100th time) after repeating the above-mentioned external quantum efficiency measurement 100 times was calculated and evaluated. The smaller the value of the external quantum efficiency reduction rate, the better the driving durability.

As shown in the above table, Example 1 has characteristics similar to those of Comparative Example 1 in terms of conductivity, photocurrent value, and external quantum efficiency, and has a smaller value of the external quantum efficiency reduction rate than that of Comparative Example 1, and has excellent driving durability.

<Example 2 to Example 13, Comparative Example 2, Comparative Example 3>

In Example 1, the specific ligand 1 and the specific ligand 2 were changed to the ligands listed in the following table, and the test body 2 was prepared in the same manner as in Example 1. The driving durability was evaluated using the obtained test body 2. The values of the reduction rate of the external quantum efficiency of Examples 2 to 13, Comparative Example 2, and Comparative Example 3 are recorded in the following table. In addition, the value of the reduction rate of the external quantum efficiency of Comparative Example 1 is also recorded.

The ligands listed in the column of specific ligand 1 in the above table are equivalent to the first ligand in the present invention. In addition, 4-butylbutyric acid, 3-aminopropanol, 3-butylpropanol, N-(3-aminopropyl)-1,3-propanediamine, 3-(bis(3-aminopropyl)amino)propane-1-ol, 3-aminopropylphosphonic acid and 4-butylbutyric acid in the ligands listed in the column of specific ligand 2 in the above table are equivalent to the second ligand in the present invention.

In Example 11, a methanol solution in which ZnI ₂ and CdCl ₂ were mixed at a concentration of 12.5 mmol/L was used as the first ligand solution. In Example 12, a methanol solution in which 4-butylbutyric acid and 3-aminopropanol were mixed at a concentration of 0.005 v/v% was used as the second ligand solution. In Example 13, a second ligand solution in which 4-butylbutyric acid and 3-butylpropionic acid were mixed at a concentration of 0.008 v/v% was used. In Comparative Example 2, ligand replacement was performed using only the first ligand solution. Furthermore, in Comparative Example 3, ligand replacement was performed using only the second ligand solution.

As shown in the above table, compared with Comparative Examples 1 to 3, the values of the reduction rate of the external quantum efficiency of Examples 2 to 13 are all small, and the driving durability is excellent. In addition, Examples 2 to 13 have the same degree of external quantum efficiency as Example 1.

In Example 13, 3-butyl propionic acid was replaced with butyl acetic acid. Except for this, the evaluation was carried out in the same manner as in Example 13 and the test body 2 was prepared. The driving durability was evaluated using the obtained test body 2, and the same result as in Example 13 was obtained.

<Implementation Example 14>

In the preparation of the test pieces 1 and 2, the type of rinse liquid used in process 2 was changed from methanol to acetonitrile, and the test piece 2 was prepared in the same manner as in Example 1. The test piece 2 obtained was used to evaluate the driving durability, and the reduction rate of the external quantum efficiency (the value of the external quantum efficiency measured for the first time - the value of the external quantum efficiency measured for the 100th time) was 0.7%, which was improved compared with Example 1.

<Implementation Example 15>

In process 2, a methanol solution containing 0.01 v/v% of 4-butylbutyric acid and 25 mmol/L of ZnI ₂ was added dropwise as a ligand solution on the PbS quantum dot aggregate film, and samples 1 and 2 were prepared in the same manner as in Example 1. The conductivity, photocurrent value, external quantum efficiency and driving durability of the obtained samples 1 and 2 were evaluated, and the results were the same as those of Example 1.

The photodetection element obtained in the above embodiment is used to manufacture an image sensor by a known method together with a filter manufactured according to the method described in International Publication No. 2016/186050 and International Publication No. 2016/190162, and assembled into a solid imaging element, thereby obtaining an image sensor with good visibility and infrared imaging performance.

In each embodiment, even if the semiconductor quantum dots of the photoelectric conversion layer are changed to PbSe quantum dots, the same effect can be obtained.

1: Light detection element

11: Upper electrode

12: Lower electrode

12a, 13a: Surface

13: Photoelectric conversion layer

Claims (21)

A semiconductor film comprising: an aggregate of semiconductor quantum dots comprising metal atoms; and ligands coordinated to the semiconductor quantum dots, wherein the ligands comprise a first ligand being an inorganic halide and a second ligand represented by any one of formulas (A) to (C);

In formula (A), one of ^XA1 and ^XA2 is a thiol group and the other is a hydroxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^A1 represents a alkyl group, and ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 ; in formula (B), ^XB1 and ^XB2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XB3 represents S, O or NH, L ^B1 and L ^B2 each independently represent a alkyl group, ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 ; in formula (C), ^XC1 to ^XC3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XC4 represents N, L ^C1 to L ^C3 independently represents a alkyl group, ^XC1 and ^XC4 are separated by 3 to 10 atoms by L ^C1 , ^XC2 and ^XC4 are separated by 1 to 10 atoms by L ^C2 , and ^XC3 and ^XC4 are separated by 1 to 10 atoms by L ^C3 . A semiconductor film as described in claim 1, wherein the semiconductor quantum dots contain Pb atoms. A semiconductor film as described in claim 1 or claim 2, wherein the aforementioned first ligand comprises at least one selected from Group 12 elements and Group 13 elements. A semiconductor film as described in claim 1 or claim 2, wherein the first ligand comprises a Zn atom. A semiconductor film as described in claim 1 or claim 2, wherein the aforementioned first ligand comprises an iodine atom. The semiconductor film as described in claim 1 or claim 2 comprises two or more of the aforementioned first ligands. The semiconductor film as claimed in claim 1 or claim 2, wherein at least one of ^XB1 and ^XB2 in the aforementioned formula (B) is a thiol group, an amine group, a hydroxyl group or a carboxyl group, and at least one of ^{XC1 to XC3 in} the aforementioned formula (C) is a thiol group, an amine group, a hydroxyl group or a carboxyl group. The semiconductor film as described in claim 1 or claim 2, wherein the second ligand is at least one selected from 3-butyl propanol, N-(3-aminopropyl)-1,3-propylenediamine, 3-(bis(3-aminopropyl)amino)propane-1-ol and their derivatives. The semiconductor film as described in claim 1 or claim 2 further comprises ligands other than the aforementioned first ligand and the aforementioned second ligand. A photoelectric conversion element, comprising a semiconductor film as described in any one of claims 1 to 9. The photoelectric conversion element as described in claim 10 is a photodiode type light detection element. An image sensor comprising the photoelectric conversion element described in claim 10 or 11. The image sensor described in claim 12 senses light with a wavelength of 900nm to 1600nm. A method for manufacturing a semiconductor film, comprising: a semiconductor quantum dot aggregate forming process, wherein a semiconductor quantum dot dispersion liquid containing semiconductor quantum dots including metal atoms, a third ligand which is a ligand coordinated to the semiconductor quantum dots and different from a first ligand which is an inorganic halide and a second ligand represented by any one of formulas (A) to (C), and a solvent is provided on a substrate to form a semiconductor quantum dot aggregate film; and a ligand replacement process, wherein the semiconductor quantum dot aggregate formed by the semiconductor quantum dot aggregate forming process is replaced by a ligand replacement process. A film of an aggregate of the semiconductor quantum dots is provided, wherein a ligand solution 1 comprising a first ligand being an inorganic halide and a solvent and a ligand solution 2 comprising a second ligand represented by any one of formulas (A) to (C) and a solvent are provided, or a ligand solution 3 comprising a first ligand being an inorganic halide, a second ligand represented by any one of formulas (A) to (C) and a solvent are provided, and the third ligand coordinated to the semiconductor quantum dots is replaced with the first ligand and the second ligand, [Chemical Formula 2]

In formula (A), one of ^XA1 and ^XA2 is a thiol group and the other is a hydroxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, L ^A1 represents a alkyl group, and ^XA1 and ^XA2 are separated by 3 to 10 atoms by L ^A1 ; in formula (B), ^XB1 and ^XB2 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XB3 represents S, O or NH, L ^B1 and L ^B2 each independently represent a alkyl group, ^XB1 and ^XB3 are separated by 3 to 10 atoms by L ^B1 , and ^XB2 and ^XB3 are separated by 1 to 10 atoms by L ^B2 ; in formula (C), ^XC1 to ^XC3 each independently represent a thiol group, an amine group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phospho group or a phosphonic acid group, ^XC4 represents N, L ^C1 to L ^C3 independently represents a alkyl group, ^XC1 and ^XC4 are separated by 3 to 10 atoms by L ^C1 , ^XC2 and ^XC4 are separated by 1 to 10 atoms by L ^C2 , and ^XC3 and ^XC4 are separated by 1 to 10 atoms by L ^C3 . The method for manufacturing a semiconductor film as described in claim 14 further includes a rinsing process of bringing an aprotic solvent into contact with the film of the semiconductor quantum dot aggregate for rinsing. A method for manufacturing a semiconductor film as described in claim 15, wherein the aforementioned aprotic solvent is a aprotic polar solvent. A method for manufacturing a semiconductor film as described in claim 15, wherein the aforementioned aprotic solvent is at least one selected from acetonitrile and acetone. A method for manufacturing a semiconductor film as described in any one of claim 14 to claim 17, wherein in the aforementioned semiconductor quantum dot aggregate formation process, a film of semiconductor quantum dot aggregates with a thickness of 30 nm or more is formed, and the complex stability constant K1 of the aforementioned second ligand relative to the metal atoms contained in the aforementioned semiconductor quantum dots is 6 or more. A method for manufacturing a semiconductor film as described in claim 18, wherein the complex stability constant K1 of the aforementioned second ligand relative to the metal atoms contained in the aforementioned semiconductor quantum dot is greater than 8. A method for manufacturing a semiconductor film as described in claim 18, wherein the semiconductor quantum dots contain Pb atoms, and the complex stability constant K1 of the second ligand relative to the Pb atoms is greater than 6. A method for manufacturing a semiconductor film as described in claim 14, wherein the second ligand is at least one selected from 3-butyl propanol, N-(3-aminopropyl)-1,3-propylenediamine, 3-(bis(3-aminopropyl)amino)propane-1-ol and their derivatives.