Quantum dot composition, quantum dot composition-containing liquid, light-emitting element, light-emitting device, method for producing quantum dot composition

Abstract

A QD composition (31) includes a QD (32) and at least one metal compound (33) selected from the group consisting of metal fluoro complexes, hydroxy group-containing metal fluoro complexes, and fluorine-containing metal oxides. The complex stability constant of the metal fluoro complex of the at least one metal element contained in the aformentioned metal compound is greater than the complex stability constant of the metal fluoro complex of at least one metal element contained in the QDs, and is between 0.1 and 20.0, inclusive.

Description

Technical Field

[0001] The present disclosure relates to a quantum dot composition, a liquid containing the quantum dot composition, a light-emitting element, a light-emitting device, and a method for producing a quantum dot composition.

Background Art

[0002] Patent Document 1 discloses, as a very stable nanostructure, a quantum dot composition including a quantum dot and at least one fluoride-containing ligand selected from the group consisting of fluorozincate, tetrafluoroborate, and hexafluorophosphate bonded to the surface of the quantum dot.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in fluorozincate, the Zn (zinc)-F (fluorine) bond in the complex is relatively weak. Therefore, fluorozincate has a strong tendency for the F in the complex to be substituted by an OH group and is unstable against the substitution of the OH group. Fluorozincate is more likely to form a Zn-OH bond than a Zn-F bond and reacts with the OH group to easily generate Zn(OH)2.

[0005] Patent Document 1 unconditionally uses at least one selected from the group consisting of fluorozincate, tetrafluoroborate, and hexafluorophosphate as a fluoride-containing ligand. However, when the quantum dots contain, for example, Zn as in Patent Document 1, if fluorozincate is used as the fluoride-containing ligand, OH groups will be present near the surface of the quantum dots, deteriorating the properties of the quantum dots and reducing their reliability. Therefore, fluorozincate is not preferable from the viewpoint of the long-term reliability of the device using the quantum dot composition. Further, when OH groups are present near the surface of the quantum dots and the quantum dots are exposed to the electric field generated by the dipole moment of the OH groups, the excitons of the quantum dots may be separated into electrons and holes, deactivated, and quenched. Moreover, Zn(OH)2 is an insulator, and the carrier injection property deteriorates due to the decrease in electrical conductivity. Therefore, when fluorozincate is used as the fluoride-containing ligand, the light emission efficiency of the quantum dots decreases.

[0006] Conversely, tetrafluoroborate and hexafluorophosphate are very stable and thus do not function sufficiently as a sacrificial layer for OH groups. Therefore, when tetrafluoroborate or hexafluorophosphate is used as the fluoride-containing ligand, the OH groups that reach the surface of the quantum dots preferentially bind to, for example, Zn contained in the surface layer of the quantum dots. As a result, also in this case, OH groups will be present near the surface of the quantum dots, deteriorating the properties of the quantum dots, reducing their reliability, and decreasing the light emission efficiency.

[0007] One aspect of the present disclosure has been made in view of the above problems, and an object thereof is to provide a quantum dot composition, a liquid containing the quantum dot composition, a light-emitting element, a light-emitting device, and a method for producing a quantum dot composition, which have high stability against OH groups and are excellent in long-term reliability and light emission efficiency.

Means for Solving the Problems

[0008] To solve the above problems, a quantum dot composition according to one aspect of the present disclosure includes quantum dots and at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine. The metal compound and the quantum dots each contain at least one metal element. The complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the metal compound is greater than the complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the quantum dots, and the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the metal compound is in the range of 0.1 or more and 20.0 or less.

[0009] To solve the above problems, a quantum dot composition according to one aspect of the present disclosure The object is , in a quantum dot composition containing quantum dots and an organic compound, at least a part of the organic compound is replaced with at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine. The metal compound and the quantum dots each contain at least one metal element. The complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the metal compound is greater than the complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the quantum dots, and the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the metal compound is in the range of 0.1 or more and 20.0 or less.

[0010] To solve the above problems, a liquid containing a quantum dot composition according to one aspect of the present disclosure includes the quantum dot composition according to one aspect of the present disclosure.

[0011] To solve the above problems, a light-emitting device according to one aspect of the present disclosure includes the quantum dot composition according to one aspect of the present disclosure.

[0012] In order to solve the above problems, a light-emitting device according to an aspect of the present disclosure includes the above light-emitting element according to an aspect of the present disclosure.

[0013] In order to solve the above problems, a method for producing a quantum dot composition according to an aspect of the present disclosure includes a substitution step of substituting at least a part of the organic compound in the initial quantum dot composition containing quantum dots and an organic compound with at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine. The quantum dots and the metal compound each contain at least one metal element, and the complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the metal compound is larger than the complex stability constant in an aqueous solution of the metal fluoro complex of at least one metal element contained in the quantum dots, and the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the metal compound is in the range of 0.1 or more and 20.0 or less. Quantum dots and metal compounds are used.

Effects of the Invention

[0014] According to an aspect of the present disclosure, it is possible to provide a quantum dot composition, a quantum dot composition-containing liquid, a light-emitting element, a light-emitting device, and a method for producing a quantum dot composition, which have high stability against OH groups and excellent long-term reliability and light-emitting efficiency.

Brief Description of the Drawings

[0015]

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Mode for Carrying Out the Invention

[0016] 〔Embodiment 1〕 (Configuration of Light-Emitting Element 1) FIG. 1 is a diagram schematically showing a partial enlargement of a schematic configuration of a light-emitting element 1 according to the present embodiment.

[0017] As shown in FIG. 1, the light-emitting element 1 includes an anode 11, a cathode 13, and a functional layer 12 including at least a light-emitting layer (hereinafter referred to as "EML") 23 provided between the anode 11 and the cathode 13. In the present embodiment, the layers between the anode 11 and the cathode 13 are collectively referred to as the functional layer 12.

[0018] The above functional layer 12 may be a single-layer type consisting only of the EML 23, or may be a multi-layer type including a functional layer 12 other than the EML 23. Examples of the functional layer 12 other than the EML 23 among the above functional layers 12 include a hole injection layer (hereinafter referred to as "HIL"), a hole transport layer (hereinafter referred to as "HTL"), an electron transport layer (hereinafter referred to as "ETL"), and the like.

[0019] In this embodiment, a layer formed in a process prior to the layer to be compared is referred to as a "lower layer", and a layer formed in a process subsequent to the layer to be compared is referred to as an "upper layer". In this embodiment, the direction from the anode 11 to the cathode 13 in FIG. 1 is referred to as the upward direction, and the opposite direction is referred to as the downward direction.

[0020] Each layer from the anode 11 to the cathode 13 is generally supported by a substrate as a support. Therefore, the light-emitting element 1 may include a substrate as a support.

[0021] The light-emitting element 1 shown in FIG. 1 has, as an example, a configuration in which a substrate 10, an anode 11, an HIL 21, an HTL 22, an EML 23, an ETL 24, and a cathode 13 are laminated in this order from the lower layer side. The light-emitting element 1 includes an HIL 21, an HTL 22, an EML 23, and an ETL 24 as the functional layer 12.

[0022] The substrate 10 is a support for forming each layer from the anode 11 to the cathode 13. The substrate 10 may be, for example, a glass substrate, or may be a flexible substrate such as a plastic substrate or a plastic film.

[0023] In addition, the light-emitting element 1 may be used, for example, as a light source of a light-emitting device such as a display device. When the light-emitting element 1 is a part of a light-emitting device, the substrate of the above light-emitting device is used for the substrate 10. Therefore, the light-emitting element 1 may be referred to as the light-emitting element 1 including the substrate 10 in some cases, or may be referred to as the light-emitting element 1 without including the substrate 10 in some cases. When the light-emitting element 1 is a part of a display device, for example, an array substrate on which a plurality of thin film transistors (TFTs) are formed may be used for the substrate 10.

[0024] The anode 11 and the cathode 13 are connected to a power source (e.g., a DC power source) not shown, so that a voltage is applied therebetween. The anode 11 and the cathode 13 each contain a conductive material and are electrically connected to the HIL 21 and the ETL 24, respectively.

[0025] The anode 11 is an electrode that supplies holes to the EML 23 when a voltage is applied. The cathode 13 is an electrode that supplies electrons to the EML 23 when a voltage is applied.

[0026] At least one of the anode 11 and the cathode 13 is a translucent electrode. Note that either one of the anode 11 and the cathode 13 may be a so-called reflective electrode having light reflectivity. The light-emitting element 1 can extract light from the translucent electrode side.

[0027] For example, when the light-emitting element 1 is a top-emission type light-emitting element that emits light from the upper electrode side, a translucent electrode is used for the upper electrode and a reflective electrode is used for the lower electrode. On the other hand, when the light-emitting element 1 is a bottom-emission type light-emitting element that emits light from the lower electrode side, a translucent electrode is used for the lower electrode, upper and a reflective electrode is used for the layer electrode.

[0028] The translucent electrode is formed of a conductive translucent material such as, for example, ITO (indium tin oxide), IZO (indium zinc oxide), AgNW (silver nanowire), a thin film of a MgAg (magnesium-silver) alloy, a thin film of Ag, etc.

[0029] On the other hand, the reflective electrode is formed of a conductive light-reflective material such as, for example, a metal such as Ag, Al, Cu, an alloy containing these metals, etc. Note that a layer made of the above translucent material and a layer made of the above light-reflective material may be laminated to form a reflective electrode.

[0030] HIL21 is a layer that has hole-transporting properties and promotes the injection of holes from the anode 11 to the HTL22. As the material of HIL21, hole-transporting materials such as a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS) are used, for example.

[0031] HTL22 is a layer that has hole-transporting properties and transports holes from HIL21 to the EML23. As the material of HTL22, hole-transporting materials such as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’-(N-4-sec-butylphenyl))diphenylamine] (abbreviation “TFB”), poly[N,N’-bis(4-butylphenyl)-N,N’-bis(phenyl)-benzidine] (abbreviation “p-TPD”), polyvinylcarbazole (abbreviation “PVK”), NiO, MoO3, MgO, MgNiO, LaNiO3 are used, for example. These hole-transporting materials may be used alone or may be mixed and used in appropriate combinations of two or more.

[0032] ETL24 is a layer that has electron-transporting properties and transports electrons from the cathode 13 to the EML23. As the material of ETL24, electron-transporting materials such as ZnO, MgZnO, TiO2, Ta2O3, SrTiO3, ZrO2, Ta2O5 are used, for example. These electron-transporting materials may be used alone or may be mixed and used in appropriate combinations of two or more.

[0033] EML23 is a QD light-emitting layer (QD composition-containing layer) that contains a QD composition 31 (quantum dot composition) containing quantum dots (hereinafter referred to as “QD”) 32 as a constituent element.

[0034] The QD composition 31 includes QD 32 and at least one metal compound 33 selected from the group consisting of a metal fluoro complex (metal-fluorine complex), a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine. Hereinafter, the metal fluoro complex containing a hydroxy group is referred to as a "hydroxy group-containing metal fluoro complex". Further, the metal oxide containing fluorine is referred to as a "fluorine-containing metal oxide". Also, a compound containing a metal element is referred to as a "metal compound".

[0035] In EML 23, holes transported from the anode 11 and electrons transported from the cathode 13 recombine, and light is emitted during the process in which excitons generated thereby transition from the conduction band level to the valence band level of QD 32.

[0036] QD 32 is a dot having a maximum particle width of 100 nm or less. Since QD is generally derived from a semiconductor material in terms of its composition, it may be referred to as a semiconductor nanoparticle. Also, since QD is generally derived from an inorganic material in terms of its composition, it may be referred to as an inorganic nanoparticle. Further, since QD has a specific crystal structure, for example, in terms of its structure, it may also be referred to as a nanocrystal.

[0037] The shape of QD 32 only needs to be within the range that satisfies the above maximum width, and is not particularly limited, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). For example, it may have a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branched three-dimensional shape, a three-dimensional shape having irregularities on the surface, or a combination thereof.

[0038] QD 32 contains at least one metal element. Examples of the metal element contained in QD 32 include Cd, Zn, In, Sb, Al, Si, Ga, Pb, Ge, Mg, etc.

[0039] Specific QD32 materials include, for example, semiconductor materials such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, InN, InP, InAs, InSb, AlP, AlS, AlAs, AlSb, GaN, GaP, GaAs, GaSb, PbS, PbSe, Si, Ge, MgS, MgSe, MgTe, etc. These materials may be used alone, or two or more of them may be mixed and used as appropriate.

[0040] Thus, QD32 may be a semiconductor material containing at least one metal element, or may be a semiconductor material combining at least one metal element and non-metal elements such as S, Te, Se, N, P, As, etc.

[0041] QD32 may be formed only by a core, or may be a two-component core type, a three-component core type, or a four-component core type. Also, as shown in FIG. 2, QD32 may have a core-shell structure including a core 32a and a shell 32b, and may be a core-shell type or a core-multishell type. Note that FIG. 2 is a cross-sectional view schematically showing an example of QD32. FIG. 2 shows an example of the schematic configuration of the main part of the QD composition 31. QD32 may contain doped nanoparticles and may have a compositionally graded structure. Also, the shell 32b may be formed in a state of being solid-soluted on the surface of the core 32a. In FIG. 2, the boundary between the core 32a and the shell 32b is shown by a dotted line, which indicates that whether the boundary between the core 32a and the shell 32b can be confirmed by analysis or not is both acceptable. The shell 32b may be formed in multiple layers.

[0042] As described above, when QD32 includes the core 32a and at least one layer of the shell 32b, the light emission efficiency due to the quantum confinement effect is improved. Also, when hydroxide ions (OH - ) invade the QD composition 31 due to the intrusion of moisture or the like, the decrease in the light emission efficiency caused by OH - directly bonding to the surface of the core 32a as a hydroxy group (OH group) can be suppressed.

[0043] As described above, QD32 only needs to contain at least one metal element. However, from the viewpoints of luminous efficiency, full-width at half-maximum of luminescence, ease of availability, etc., the core 32a contains, for example, Cd x1 Zn 1-x1 Se y1 S 1-y1 (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1) and In x2 Ga 1-x2 P (0 ≦ x2 ≦ 1) is preferably included in at least one of them.

[0044] Further, the shell 32b contains, for example, Cd x3 Zn 1-x3 Se y3 S 1-y3 (0 ≦ x3 ≦ 1, 0 ≦ y3 ≦ 1) and at least one of metal oxides represented by MO x4 (0 < x4 ≦ 3, M represents a metal element) is preferably included.

[0045] The metal element used for the shell 32b represented by M is not particularly limited as long as it satisfies the condition of 0 < x4 ≦ 3 as described above. For example, Al, Ti, Sn, V, Ni, Si, Ga, etc. can be mentioned. As an example of the metal oxide used for the shell 32b, specifically, Al2O3, TiO2, SnO2, V2O3, NiO, SiO2, GaO, etc. can be mentioned.

[0046] Since the shell 32b having a larger bandgap than the core 32a exists in this way, the luminous efficiency due to the quantum confinement effect is improved, and when OH - invades the QD composition 31, the decrease in luminous efficiency caused by OH - directly bonding to the surface of the shell 32b can be suppressed.

[0047] When QD32 has a core-shell structure, an example of the material of QD32 (the combination of the core 32a / shell 32b materials) includes, for example, ZnSe / ZnS, InP / ZnS, CdSe / CdS, etc.

[0048] Alternatively, QD32 may be a Cd-free chalcopyrite-based QD represented by ABX2. Here, A and B represent metal atoms of cationic species with different valences. Examples of the cationic species include Ag (silver), Al (aluminum), In (indium), Ga (gallium), Cu (copper), Zn (zinc), Si (silicon), Ge (germanium), Sn (tin), etc. X represents a non-metal or semi-metal atom of an anionic species such as S (sulfur), Se (selenium), Te (tellurium), P (phosphorus), As (arsenic), etc.

[0049] When the core 32a is formed of such a chalcopyrite-based material, the material of the shell 32b may be, for example, ZnS, ZnSe, etc., may be GaO, GaS, etc., or may be a combination thereof.

[0050] In addition, when QD32 includes the shell 32b, the shell 32b may be provided on the surface of the core 32a. It is desirable that the shell 32b covers the entire core 32a, but it is not necessary for the shell 32b to completely cover the core 32a. The shell 32b may be formed on a part of the surface of the core 32a. If it can be determined from the observation of a cross-section of the QD32 that the shell 32b is formed on a part of the surface of the core 32a, or if it can be determined that the core 32 a is wrapped by the shell 32 b, then it can be said that it has a core-shell structure. Therefore, it is sufficient if it can be determined by observing a cross-section of QD32 whether the shell 32b covers the entire core 32a. The above cross-section observation can be performed, for example, with a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM).

[0051] The emission wavelength of QD32 can be variously changed depending on the particle size, composition, etc. of the particles. The above QD32 is a QD that emits visible light, and by appropriately adjusting the particle size and composition of QD32, it is possible to control the emission wavelength from the blue wavelength region to the red wavelength region.

[0052] Thus, QD32 may be, for example, a blue QD that emits blue light, a green QD that emits green light, or a red QD that emits red light.

[0053] Note that the blue light is, for example, light having an emission peak wavelength in a wavelength band of 400 nm or more and 500 nm or less. The green light is, for example, light having an emission peak wavelength in a wavelength band exceeding 500 nm and 600 nm or less. The red light is, for example, light having an emission peak wavelength in a wavelength band exceeding 600 nm and 780 nm or less.

[0054] In the QD composition 31, at least one metal compound 33 selected from the group consisting of a metal fluoro complex, a hydroxy group-containing metal fluoro complex, and a fluorine-containing metal oxide is present on the surface of QD32.

[0055] The metal compound 33 contains at least one metal element. The metal compound 33 used in the present embodiment has a complex stability constant in an aqueous solution of a metal fluoro complex of at least one metal element contained in the metal compound 33 that is greater than the complex stability constant in an aqueous solution of a metal fluoro complex of at least one metal element contained in QD32.

[0056] The OH substitution tendency in an aqueous solution of a metal fluoro complex is indicated by the complex stability constant. When the complex stability constant in an aqueous solution of a metal fluoro complex is K(logβ), the complex stability constant K is represented by the equilibrium constant of the following reaction formula (A) as shown in the following formula (1).

[0057] M + mF ⇔ MF m ‥(A) K(Logβ)=[MF m / ([M] × [F] m )‥(1) In formula (1), [MF] represents the activity (concentration) of the metal fluoro complex (MF) in the above aqueous solution. [M] represents the activity (concentration) of the metal (M) that is in equilibrium with the metal (M) of the metal fluoro complex (MF), and [F] represents the activity (concentration) of the fluorine (F) that is in equilibrium with the fluorine (F) of the metal fluoro complex (MF).

[0058] When the complex stability constant of the metal fluoro complex of the at least one metal element contained in the metal compound 33 used in the present disclosure in an aqueous solution at 25 °C is K1, the complex stability constant K1 is in the range of 0.1 or more and 20.0 or less.

[0059] As described above, when QD32 contains a plurality of metal elements, among the at least one metal element contained in the metal compound 33, it is desirable that the complex stability constant of the metal fluoro complex of the metal element most contained in the metal compound 33 in an aqueous solution is greater than the complex stability constant of the metal fluoro complex of the metal element most contained in QD32 in an aqueous solution.

[0060] In particular, when QD32 contains a plurality of metal elements on its surface (outermost layer), among the at least one metal element contained in the metal compound 33, it is desirable that the complex stability constant of the metal fluoro complex of the metal element most contained in the metal compound 33 in an aqueous solution is greater than the complex stability constant of the metal fluoro complex of the metal element most contained on the surface (outermost layer) of QD32 in an aqueous solution.

[0061] Here, the surface (outermost layer) of QD32 refers to the shell 32b when QD32 includes the shell 32b, and refers to the surface of the core 32a when QD32 does not include the shell 32b and is formed only of the core 32a.

[0062] In addition, the "metal element most contained in the metal compound 33 among at least one metal element contained in the metal compound 33" refers to the metal element contained in the metal compound 33 when the metal compound 33 contains only one metal element, and refers to the metal element most contained in the metal compound 33 among the plurality of metal elements contained in the metal compound 33 when the metal compound 33 contains a plurality of metal elements.

[0063] In addition, the metal element most contained in the metal compound 33 or QD32 refers to the metal element that can be judged to have the highest concentration in the observation of a cross-section of these metal compounds 33 or QD32. Further, the metal element most contained in the surface (outermost layer) of QD32 refers to the metal element that can be judged to have the highest concentration near the surface of QD32 in the observation of a cross-section of QD32.

[0064] In addition, when the metal compound 33 contains a plurality of metal elements, it is desirable that the complex stability constant K1 of the metal fluoro complex of the metal element most contained in the metal compound 33 be in the range of 0.1 or more and 20.0 or less in an aqueous solution at 25°C.

[0065] Table 1 shows an example of the complex stability constant K of various metal ions and metal fluoro complexes having these metal ions as central metal ions in an aqueous solution at 25°C. Note that the equilibrium constant (complex stability constant) of metal ions in an aqueous solution, which is generally disclosed, is a value measured at 25°C. Therefore, the complex stability constant K can be directly adopted as the value of the equilibrium constant (complex stability constant) of metal ions in an aqueous solution, which is generally disclosed. Note that the generally disclosed equilibrium constant (complex stability constant) varies slightly depending on the measurement conditions such as the activity (concentration) of each metal ion. Therefore, in Table 1, among the generally disclosed equilibrium constants (complex stability constants), the highest value (in other words, the value in the most stable state) that has been confirmed is described. In addition, the activity (concentration) of each metal ion is described as the complex stability constant at the lower value among 0, 0.5, and 1.0, which is a lower value for the interaction between complexes among the confirmed values.

[0066]

Table 1

[0067] As described above, examples of metal ions for which 0.1 ≦ K1 ≦ 20.0 include, from Table 1, Sr 2+ , Co 2+ , Ni 2+ , Ca 2+ , Mn 2+ , Mn 3+ , Fe 2+ , Fe 3+ , Cd 2+ , Cu 2+ , Zn 2+ , Mg 2+ , Bi 3+ , Pb 2+ , Si 4+ , Ti 4+ , V 3+ , V 5+ , Ge 4+ , Sn 2+ , Cr 3+ , Ga 3+ , Sb 3+ , In 3+ , Y 3+ , Al 3+ and other metal ions.

[0068] Therefore, as the above metal compound 33, for example, at least one metal compound selected from the group consisting of a metal fluoro complex, a hydroxy group-containing metal fluoro complex, and a fluorine-containing metal oxide having at least one metal element selected from the group consisting of Sr, Co, Ni, Ca, Mn, Fe, Cd, Cu, Zn, Mg, Bi, Pb, Si, Ti, V, Ge, Sn, Cr, Ga, Sb, In, Y, and Al can be used.

[0069] More specifically, as the above metal compound 33, for example, at least one metal compound selected from the group consisting of a metal fluoro complex, a hydroxy group-containing metal fluoro complex, and a fluorine-containing metal oxide, which contains any one metal element selected from the group consisting of Sr(II), Co(II), Ni(II), Ca(II), Mn(II), Mn(III), Fe(II), Fe(III), Cd(II), Cu(II), Zn(II), Mg(II), Bi(III), Pb(II), Si(IV), Ti(IV), V(III), V(V), Ge(IV), Sn(II), Cr(III), Ga(III), Sb(III), In(III), Y(III), and Al(III) as a central metal (central metal ion), can be used.

[0070] In addition, it is preferable that the complex stability constant K1 is in the range of 1.2 or more and 19.0 or less. As the metal ions that satisfy 1.2 ≦ K1 ≦ 19.0 as described above, from Table 1, for example, Mg 2+ , Bi 3+ , Pb 2+ , Si 4+ , Ti 4+ , Mn 3+ , V 3+ , V 5+ , Ge 4+ , Sn 2+ , Cr 3+ , Ga 3+ , Sb 3+ , In 3+ , Fe 3+ , Y 3+ , Al 3+ and other metal ions can be mentioned.

[0071] Therefore, as the above metal compound 33, for example, at least one metal compound selected from the group consisting of a metal fluoro complex, a hydroxy group-containing metal fluoro complex, and a fluorine-containing metal oxide, which contains any one metal element selected from the group consisting of Mg(II), Bi(III), Pb(II), Si(IV), Ti(IV), Mn(III), V(III), V(V), Ge(IV), Sn(II), Cr(III), Ga(III), Sb(III), In(III), Fe(III), Y(III), and Al(III) as a central metal (central metal ion), is preferably used.

[0072] Also, when the complex stability constant K of the metal fluoro complex of at least one metal element contained in QD32 is K2, it is preferable that the above complex stability constant K1 is 0.1 or more greater than the above complex stability constant K2. For example, when Zn is contained in the surface (outermost layer) of QD32, as the metal satisfying 0.1 ≦ K1 ≦ 20.0 and K1 ≧ (K2 + 0.1), from Table 1, for example, Mg(II), Bi(III), Pb(II), Si(IV), Ti(IV), Mn(III), V(III), V(V), Ge(IV), Sn(II), Cr(III), Ga(III), Sb(III), In(III), Fe(III), Y(III), Al(III), etc. can be mentioned.

[0073] Also, it is preferable that the above complex stability constant K1 is 1.5 or more greater than the above complex stability constant K2. For example, when Zn is contained in the surface (outermost layer) of QD32, as the metal satisfying 0.1 ≦ K1 ≦ 20.0 and K1 ≧ (K2 + 1.5), from Table 1, for example, Si(IV), Ti(IV), Mn(III), V(III), V(V), Ge(IV), Sn(II), Cr(III), Ga(III), Sb(III), In(III), Fe(III), Y(III), Al(III), etc. can be mentioned.

[0074] Also, the above complex stability constant K1 is 2.5It is preferably large. For example, when Zn is contained in the surface (the outermost layer) of QD32, examples of the metal that satisfies 0.1 ≦ K1 ≦ 20.0 and K1 ≧ (K2 + 2.5) for the complex stability constant K1 include, from Table 1, for example, Ti(IV), Mn(III), V(III), V(V), Ge(IV), Sn(II), Cr(III), Ga(III), Sb(III), In(III), Fe(III), Y(III), Al(III), etc.

[0075] Hereinafter, in this embodiment, a case where the metal compound 33 is a ligand containing a metal fluoro complex and QD32 contains Zn atoms will be described as an example.

[0076] For example, in QD32 having only the core 32a or a core-shell structure in which Zn atoms are present on the surface of QD32, the Zn atoms exposed on the surface can be a factor in exciton deactivation. In order to suppress the decrease in the emission efficiency due to Zn exposed on the surface of such QD32 (the surface of the core 32a or the shell 32b), it is desirable that a ligand is coordinated on the surface of QD32.

[0077] In order to stably disperse QD32 in a solvent, it is necessary to separate QD32 from each other. For this purpose, a ligand length of a certain length is required. On the other hand, in a carrier-injection type light-emitting device, the shorter the ligand length, the better. However, since the ionic radius of a halogen is small, with only a halogen, QD32 aggregates and QD32 does not disperse.

[0078] Therefore, in the present embodiment, a metal fluoro complex is used as a ligand. The metal fluoro complex has a larger ionic radius than a single halogen ion. For this reason, according to the present embodiment, as shown in FIG. 1, even when only the metal fluoro complex is used as a ligand, aggregation of QD32 can be suppressed and QD32 can be dispersed. Moreover, compared with the organic ligands generally used for stable dispersion, the metal fluoro complex has a shorter ligand length and can bring QD32 closer to each other. For this reason, compared with the organic ligand, the metal fluoro complex can improve the carrier injection property and suppress a decrease in the light emission efficiency due to defects on the surface of QD32.

[0079] However, for the dispersion stability of QD32, the QD composition 31 may contain an organic compound 34 as an organic ligand, as shown in FIG. 3. FIG. 3 is a diagram schematically showing, in an enlarged manner in part, another example of the schematic configuration of the light-emitting element 1 according to the present embodiment.

[0080] When the QD composition 31 contains the organic compound 34, as the organic compound 34, various known organic compounds containing at least one coordinating functional group capable of coordinating to QD32 and used as an organic ligand can be used.

[0081] Typical examples of the coordinating functional group include at least one functional group selected from the group consisting of an amino (-NR2) group, a phosphonato (-P(=O)(OR)2) group, a phosphine (-PR2) group, a phosphine oxide (-P(=O)R2) group, a carboxyl (-C(=O)OH) group, and a thiol (-SH) group.

[0082] Among the above coordinating functional groups, the thiol group has a higher coordinating property to QD, particularly to QD containing Zn, than other coordinating functional groups, and can coordinate to QD32 more stably.

[0083] Examples of the organic compound 34 used as the above organic ligand include amine compounds such as oleylamine and dodecylamine; phosphonic acid compounds such as (12-phosphonododecyl)phosphonic acid and 11-mercaptoundecylphosphonic acid; phosphine compounds such as trioctylphosphine and tributylphosphine; phosphine oxide compounds such as trioctylphosphine oxide and tributylphosphine oxide; aliphatic compounds such as oleic acid and octanoic acid; thiol compounds such as dodecanethiol and octanethiol; and the like.

[0084] However, in order to facilitate carrier injection, it is desirable that the content ratio of the organic compound 34 in the QD composition 31 is low or the QD composition 31 does not contain the organic compound 34. The ratio of the metal compound 33 to the total amount of the metal compound 33 and the organic compound 34 in the QD composition 31 is desirably 40% or more, more desirably 70% or more, and particularly desirably 90% or more.

[0085] In many cases, organic ligands are coordinated as initial ligands in synthesized or commercially available QDs. Commercially available QDs are generally provided in the state of a QD composition-containing liquid containing an organic ligand. The organic ligand is used as a dispersant for improving the dispersibility of QDs in the QD composition-containing liquid, and is also used for improving the surface stability and storage stability of QDs. Further, for example, a wet method is used for the synthesis of QDs, and the particle size of QDs is controlled by coordinating an organic ligand on the surface of QDs. Therefore, the QD composition-containing liquid synthesized by the wet method contains the organic ligand used for the synthesis of QDs.

[0086] Therefore, in order to obtain the QD composition 31, it is necessary to replace the organic ligand as the initial ligand contained in the synthesized or commercially available QD composition-containing liquid with the metal compound 33. Hereinafter, the synthesized or commercially available QD composition-containing liquid is referred to as the "initial QD composition-containing liquid".

[0087] The organic compound 34 may be an organic compound as an organic ligand (initial ligand) contained in the initially synthesized or commercially available QD composition-containing liquid, or may be an organic compound different from the initial ligand.

[0088] The film formation of EML23 is performed by applying a QD composition-containing liquid containing the QD composition 31. As an example, in the present embodiment, the QD composition-containing liquid is produced by a ligand substitution process in a solution state. The QD composition-containing liquid and ligand substitution will be described later.

[0089] As shown in FIGS. 1 and 3, in EML23, at least a part of the plurality of metal compounds 33 is coordinated to the QD 32. Since the metal fluoro complex is an anion and negatively charged, it is attracted to the positively charged surface of the QD 32 as a ligand. Thereby, the metal fluoro complex can be coordinated to the QD 32.

[0090] In the present embodiment, "coordination" indicates that the ligand and the surface of the QD 32 are interacting. For example, it indicates that the ligand is adsorbed on the surface of the QD 32 (in other words, the ligand is modifying (surface-modifying) the surface of the QD 32). Here, "adsorption" indicates that the concentration of the ligand is increased on the surface of the QD 32 compared to the surroundings. The above adsorption may be chemisorption with a chemical bond between the QD 32 and the ligand, or may be physical adsorption or electrostatic adsorption.

[0091] Therefore, if the ligand can interact with the surface of the QD 32, it may be bonded by a coordination bond, co-owned bond, ionic bond, hydrogen bond, etc., or may not necessarily be bonded. The above interaction may be, for example, an interaction of coordination bondability, covalent bondability, ionic bondability, hydrogen bondability, or may be a van der Waals interaction or other molecular interaction.

[0092] Thus, in this embodiment, the "ligand" refers to a molecule or ion capable of interacting with the surface of QD32. Any of the exemplified metal compounds 33 is a molecule capable of interacting with the surface of QD32 and can be used as a ligand as described above. In addition, in this embodiment, the "ligand" includes not only molecules or ions coordinated on the surface of QD32 but also molecules or ions that can be coordinated but are not coordinated.

[0093] The types of ligands contained in EML23 can be identified, for example, by combining a plurality of analytical methods such as MALDI-TOF-MS method, LC-MS / MS method, TOF-SIMS method, ICP-AES method, and NMR method.

[0094] The MALDI (Matrix-Assisted Laser Desorption / Ionization) method is a method in which a nitrogen laser beam (wavelength = 337 nm) is irradiated onto a matrix mixture to rapidly (in several nsec) heat the outermost surface to 100 nm and vaporize it.

[0095] The TOF-MS (Time-of-Flight Mass Spectrometry) method is a method of mass spectrometry that utilizes the fact that the flight time of ions differs depending on the mass-to-charge ratio m / z value.

[0096] The LC-MS / MS (Liquid Chromatography-Mass Spectrometry) method is a method of identifying molecules using an apparatus that combines a high-performance liquid chromatograph (HPLC) and a triple quadrupole mass spectrometer (MS / MS). LC-MS / MS is excellent for molecule identification because a mass spectrum that is more separated than LC-MS can be obtained by the connected MS section.

[0097] In the TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) method, when a sample is irradiated with a primary ion beam under ultra-high vacuum, secondary ions are emitted from the outermost surface (1 - 3 nm) of the sample. By introducing the secondary ions into a time-of-flight (TOF-type) mass spectrometer, the mass spectrum of the outermost surface of the sample can be obtained. At this time, by keeping the primary ion irradiation dose low, surface components can be detected as molecular ions that maintain their chemical structure or partially cleaved fragments, and information on the elemental composition and chemical structure of the outermost surface can be obtained.

[0098] The ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) method is a method in which an atomized liquid sample is introduced into a plasma, and the emission observed in the plasma is spectroscopically analyzed for each element by a spectroscope to perform qualitative and quantitative analysis of the elements, and it is mainly used for the analysis of metal elements.

[0099] The NMR (Nuclear Magnetic Resonance) method is a method for analyzing the molecular structure of a compound by irradiating a nucleus in a state where a magnetic field is applied with an electromagnetic wave from the outside and observing the resonance phenomenon of nuclear spin.

[0100] Similarly, the metal elements contained in QD32 can be identified by the above methods. When QD32 is of the core type, the metal elements detected from the QD32 (in other words, core 32a) are regarded as the metal elements contained in QD32. At this time, it is desirable to regard the most detected metal element as the metal element contained in QD32. On the other hand, when QD32 has a core-shell structure and the core 32a and the shell 32b can be separated and detected, the metal elements detected from the shell 32b are regarded as the metal elements contained in QD32. When the core 32a and the shell 32b cannot be separated, it is considered that a common metal element is used for the core 32a and the shell 32b, and the metal elements detected from the entire QD32 are regarded as the metal elements contained in QD32. In any case, it is desirable to regard the most detected metal element as the metal element contained in QD32.

[0101] As described above, the metal fluoro complex is an anion, and for the counter ion, for example, H + , NH4+ 、 Na + 、 K + 、 R4N + and the like cations can be mentioned. Also, here, for R in R4N + for example, CH3C x H 2x can be mentioned. X is preferably an integer from 1 to 3, for example, because it is easily available.

[0102] Therefore, the metal compound 33 includes an anion 33a and a cation 33b, and the anion 33a includes a metal fluoro complex. The metal fluoro complex and the counter ion may be bonded to each other within the EML23 to form a metal fluoro complex compound. The metal fluoro complex compound to be used is preferably a compound having high solubility in a polar solvent, particularly an amphoteric solvent composed of polar molecules such as ethanol. For this reason, as the counter ion, the above-exemplified cations are preferable, and the cation 33b is preferably at least one selected from the group consisting of the above-exemplified cations.

[0103] As described above, the QD composition 31 includes QD32 and at least one metal compound 33. When the QD composition 31 includes QD32 and a metal compound 33 (for example, a metal fluoro complex compound) coordinated to the QD32 as a ligand, the QD composition 31 includes, for example, as shown in FIG. 1, QD32 and the metal compound 33 in a state before coordination to the QD32 or in a coordinated state. Here, the "state before coordination" refers to a state in which the anion 33a and the cation 33b are bonded. Also, the "coordinated state" refers to a state in which, for example, a metal fluoro complex compound, which is the anion 33a, interacts with the surface of the QD32 (for example, a state in which the metal fluoro complex compound is bonded to the surface of the QD32).

[0104] Similarly, when the QD composition 31 further includes an organic compound 34 coordinated to QD32 as an organic ligand, the QD composition 31 includes the organic compound 34 in a state before coordination to QD32 or in a coordinated state. When the organic compound 34 has, for example, a thiol (-SH) group as a coordinating functional group, the hydrogen atom of the thiol group of the organic compound 34 is removed and the organic compound 34 is coordinated to QD32 by a sulfide (-S-) bond. Therefore, here, the organic compound 34 in the "state before coordination" refers to, for example, the organic compound 34 in a state where a hydrogen atom removed by coordination is bonded.

[0105] In FIG. 1, the metal compound 33 includes a titanium fluoro complex ([TiF6] 2- ) containing titanium (IV) as a central metal (central metal ion) as an anion 33a, and ammonium (NH4 + ) as a cation 33b, and is illustrated by taking the case of ammonium titanium fluoride as an example. However, the metal fluoro complex compound according to the present embodiment is not limited to this, and various metal fluoro complex compounds formed by combining a metal fluoro complex containing the exemplified metal element and the exemplified counter ion can be used. Hereinafter, as the notation of the complex, [TiF6] 2- is simply denoted as "TiF6 2- ". The other complexes are also denoted in the same manner.

[0106] According to the present embodiment, by using such a metal fluoro complex as a ligand, as described above, aggregation of QD32 can be suppressed and carrier injection properties can be improved. In addition, when OH - enters the QD composition 31, which causes a decrease in the light emission efficiency of QD32, fluoride ions (F - ) in the metal fluoro complex are substituted with the above OH - , and it is possible to suppress the direct bonding of OH groups to the surface of QD32.

[0107] The stability of the metal fluoro complex with respect to OH groups (in other words, F - in the metal fluoro complex is OH -The stability (reactivity) to substitution varies depending on the type of metal element in the metal fluoro complex. The above stability (reactivity) can be compared by the complex stability constant K described above.

[0108] A metal fluoro complex with a small complex stability constant K has F in the metal fluoro complex - and OH - readily substituted. Also, there are many metal species that become metal hydroxides as the final product. For example, when Zn(OH)2 is present near QD32, QD32 is deactivated, causing quenching. As a result, the quantum efficiency decreases, and the carrier injection property decreases due to the decrease in electrical conductivity. Also, from the perspective of long-term stability, the use of a metal fluoro complex that easily forms hydroxides is not preferable. Therefore, it is preferable to use a metal fluoro complex with a high complex stability constant. Also, as described above, as the metal element contained in the metal compound 33, the complex stability constant K1 in the aqueous solution of the metal fluoro complex of at least one metal element contained in the metal compound 33 is selected to be larger than the complex stability constant K2 in the aqueous solution of the metal fluoro complex of at least one metal element contained in QD32.

[0109] For example, taking TiF6 2- as an example, TiF6 2- has a higher complex stability constant K than ZnF4 2- and can exist as a more stable complex ligand with respect to the OH group.

[0110] ZnF4 2- loses its ligand by moisture (OH - ) as shown in the following equation.

[0111] Zn-F + OH - → Zn-OH + F - If the complex stability constant K is 20.0 or less, substitution between F - and OH - occurs as described above. In particular, Zn has a relatively low complex stability constant K, and the reaction to Zn-OH readily proceeds. Therefore, when the metal compound 33 is ZnF42- If so, as the final product, metal compound 33 is likely to become a metal hydroxide. Note that the more unstable the complex of the metal element is, the more likely it is to be in a state containing OH from the beginning. - from the beginning.

[0112] As described above, when QD32 contains Zn as a metal element, if metal compound 33 is ZnF4 2- then the metal element contained in metal compound 33 is the same as the metal element contained in QD32, and the complex stability constant K1 = the complex stability constant K2. Therefore, as described above, due to moisture (OH - ), the ligand directly coordinated to QD32 is removed, and metal hydroxide is formed on the surface of QD32. As a result, quenching occurs and the characteristics of QD32 deteriorate.

[0113] On the other hand, for example, like [AlF6] having a stable Al-F bond 3- the F of a metal fluoro complex that is too stable - is hardly replaced by OH - . Therefore, when such a metal fluoro complex is used as a ligand, the OH - that has invaded EML23 directly binds to the Zn 2+ on the surface of QD32. Therefore, it is not preferable to use a very stable metal fluoro complex with a complex stability constant K exceeding 20.0 as a ligand.

[0114] In contrast, in this embodiment, as described above, a metal fluoro complex in which the complex stability constant K1 is larger than the complex stability constant K2 and the complex stability constant K1 is in the range of 0.1 or more and 20.0 or less is used as a ligand.

[0115] In this case, since the complex stability constant K1 is 20.0 or less, when OH - invades EML23, the OH - is replaced by F - . On the other hand, since the complex stability constant K1 is 0.1 or more, the metal fluoro complex does not initially contain OH - from the beginning.

[0116] Also, since the complex stability constant K1 is larger than the complex stability constant K2, for the intrusion of OH into EML23 - with respect to the intrusion of OH into EML23, F that is not directly coordinated to the surface of QD32 - (in other words, F other than the F on the surface of QD32 - other than the F on the surface of QD32 - ) is replaced by OH - . Therefore, according to this embodiment, the ligand directly coordinated to the surface of QD32 does not come off, and an OH group does not directly bind to the surface of QD32. For this reason, the quenching of QD32 can be suppressed.

[0117] FIG. 4 is a diagram schematically showing the reaction between the metal fluoro complex and OH - when moisture intrudes into EML23.

[0118] As shown in FIG. 4, when moisture intrudes into EML23 and OH - intrudes into the QD composition 31, F - in the above metal fluoro complex is replaced by OH - . As a result, the above metal fluoro complex binds to an OH group instead of a metal (for example, a metal constituting the surface (outermost layer) of QD32) such as a Zn atom that constitutes QD32. Thus, according to this embodiment, the ligand functions as a sacrificial layer against OH - , and it is possible to suppress the direct binding of an OH group to a metal that constitutes QD32 such as a Zn atom. As a result, the deterioration of QD32 itself can be suppressed, and the decrease in the light emission efficiency of QD32 can be suppressed.

[0119] Note that, as described above, when OH - intrudes into the QD composition 31, a part of F - in the above metal fluoro complex is replaced by OH -It is replaced with. Therefore, the QD composition 31 may contain a metal fluoro complex containing a hydroxy group. In other words, at least a part of the metal fluoro complexes contained in the QD composition 31 may have a part of the fluoride ions in the metal fluoro complex replaced with hydroxide ions.

[0120] Also, the ligand diameter of the halogen ligand is such that when the halogen ligand is, for example, F - and is a monatomic halide ion as in, it is represented by twice the ionic radius of the halide ion. The complex ion radius of TiF6 2- is, for example, more than twice as large as the ionic radius of elemental F (F - ). For example, the ligand diameter of F - is 130 pm, whereas the ligand diameter of TiF6 2- is about 300 pm. Therefore, when using, for example, TiF6 2- as the ligand, the distance between QD32s can be increased compared to the case of using F - , and the dispersion stability of QD32 can be improved. For this reason, according to the present embodiment, it is possible to provide a quantum dot composition having high stability against OH groups, excellent long-term reliability and luminous efficiency, and a light-emitting element 1 including the EML23 containing the quantum dot composition.

[0121] In FIGS. 1 and 3, the case where the light-emitting element 1 has a conventional structure with the anode 11 as the lower electrode is illustrated as an example. However, the light-emitting element 1 may have an inverted structure with the cathode 13 as the lower electrode, and may have a structure in which, for example, the cathode 13, ETL24, EML23, HTL22, HIL21, and anode 11 are laminated in this order from the lower layer side on the substrate 10.

[0122] As described above, the film formation of the EML23 is performed by applying a QD composition-containing liquid containing the QD composition 31.

[0123] (QD composition-containing liquid 41) FIG. 5 is a cross-sectional view schematically showing an example of the QD composition-containing liquid 41 according to the present embodiment.

[0124] The QD composition-containing liquid 41 according to the present embodiment includes a QD composition 31 and a solvent 42.

[0125] As described above, the QD composition 31 includes QDs 32 and a metal compound 33. As described above, the metal compound 33 includes an anion 33a and a cation 33b, and the anion 33a includes a metal fluoro complex. As shown in FIG. 4, the metal fluoro complex compound exists as an anion 33a and a cation 33b in the QD composition-containing liquid 41.

[0126] In FIG. 5, as an example, the case where the QD composition 31 contains an organic compound 34 (residual organic ligand) is illustrated. However, the present embodiment is not limited thereto, and the QD composition 31 may contain QDs 32 and a metal compound 33 as described above.

[0127] The QD composition-containing liquid 41 is a dispersion in which the QD composition 31 is dispersed in the solvent 42. The QD composition-containing liquid 41 may be, for example, a colloidal solution in which the QD composition 31 is colloidal-dispersed in the solvent 42.

[0128] The solvent 42 is selected according to the ratio of the metal fluoro complex coordinated on the surface of the QDs 32 and the organic compound 34 in the QD composition 31. For example, when the ratio of the metal fluoro complex that is easily dissolved in a polar solvent is large, a polar solvent is selected, and when the ratio of the organic compound 34 is large, a nonpolar solvent is selected. However, since the substitution from the organic compound 34 to the metal fluoro complex proceeds better, a polar solvent is more suitable as the solvent 42. As the polar solvent, a polar solvent other than water that is liquid at room temperature is preferably used. Among them, as the solvent 42, for example, amphoteric solvents such as methanol and ethanol are more preferably used. However, the present invention is not limited thereto, and the solvent 42 may be, for example, a non-aqueous polar solvent such as DMSO (dimethyl sulfoxide).

[0129] The concentration of the ligand in the QD composition-containing liquid 41 desirably contains an excess metal fluoro complex in order to maintain the interval between QD32s and for the protection of the surface of QD32. Note that the content of the metal fluoro complex with respect to QD32 may be set so that QD32 can be uniformly dispersed in the solvent 42, and is not particularly limited.

[0130] (Method for manufacturing the light-emitting element 1) Next, an example of the method for manufacturing the light-emitting element 1 according to Embodiment 1 will be described. FIG. 6 is a flowchart showing an example of the outline of the method for manufacturing the light-emitting element 1 according to Embodiment 1. In the following, for convenience of explanation, for example, the anode 11 is taken as the first electrode, the cathode 13 is taken as the second electrode, the first electrode formation step is the anode formation step, and the second electrode formation step is the cathode formation step. For this reason, in the following, the HTL22 will be described as the first carrier transport layer and the ETL24 will be described as the second carrier transport layer. However, the formation order and the lamination order of the anode 11 and the cathode 13 are not particularly limited. For example, the cathode 13 may be the first electrode, the anode 11 may be the second electrode, the ETL24 may be the first carrier transport layer, and the HTL22 may be the second carrier transport layer. Therefore, the first electrode formation step may be the cathode formation step, the second electrode formation step may be the anode formation step, the first carrier transport layer formation step may be the electron transport layer formation step, and the second carrier transport layer formation step may be the hole transport layer formation step. When the cathode 13 is the first electrode and the first carrier injection layer is the HIL21, the first carrier injection layer formation step is performed after the electron transport layer formation step. Further, when the cathode 13 is the first electrode and the light-emitting element 1 includes an electron injection layer, the first carrier injection layer formation step may be the electron injection layer formation step.

[0131] In the manufacturing method of the light-emitting element 1 according to this embodiment, as shown in FIG. 6, first, for example, an anode 11 is formed as a first electrode on a substrate 10 (step S1, first electrode forming step, anode forming step). Next, the HIL 21 is formed (step S2, first carrier injection layer forming step, hole injection layer forming step). Next, the HTL 22 is formed (step S3, first carrier transport layer forming step, hole transport layer forming step). In parallel, a QD composition-containing liquid 41 is manufactured (liquid preparation) (step S11, QD composition-containing liquid manufacturing step). As described above, the QD composition-containing liquid 41 includes a QD composition 31 containing QD 32 and a metal compound 33, and a solvent 42.

[0132] Subsequently, the EML 23 is formed using the above QD composition-containing liquid 41 (step S4, light-emitting layer forming step). Next, the ETL 24 is formed (step S5, second carrier transport layer forming step, electron transport layer forming step). Next, the cathode 13 is formed (step S6, second electrode forming step, cathode forming step). Thus, the light-emitting element 1 is manufactured.

[0133] When the light-emitting element 1 is a part of a display device, in step S4, a red light-emitting layer containing red QDs, a green light-emitting layer containing green QDs, and a blue light-emitting layer containing blue are coated using a process similar to the conventional one, such as photolithography.

[0134] Also, after step S1 and before step S2, an edge cover forming step of forming an edge cover that covers the edge of the lower electrode (anode 11 in this embodiment) may be performed as necessary.

[0135] For the formation of the anode 11 in step S1 and the formation of the cathode 13 in step S6, for example, a vapor deposition method, a sputtering method, or the like is used.

[0136] For the formation of the HIL 21 in step S2 and the formation of the HTL 22 in step S3, for example, a coating method, a sputtering method, a sol-gel method, or the like is used. For the formation of the ETL 24 in step S5, for example, a coating method or the like is used.

[0137] The step of manufacturing the QD composition-containing liquid (step S11) includes a ligand substitution step (step S21) in a liquid.

[0138] As described above, the initially obtained QD composition-containing liquid by synthesis or commercially contains an organic ligand as an initial ligand. At least a part of the initial ligand is coordinated to the QD.

[0139] Therefore, in step S11 (the step of manufacturing the QD composition-containing liquid), it is necessary to substitute the initial ligand coordinated to QD32 with a metal fluoro complex. Therefore, the above step S11 (the step of manufacturing the QD composition-containing liquid) includes the above ligand substitution step (step S21) of substituting the initial ligand (organic ligand) contained in the initially obtained QD composition-containing liquid by synthesis or commercially with a metal fluoro complex (metal compound 33).

[0140] In the present embodiment, the QD composition-containing liquid 41 is manufactured by a ligand substitution process in a solution state.

[0141] Hereinafter, a method for substituting the initial ligand (organic ligand) coordinated to QD32 with a metal fluoro complex will be described.

[0142] FIG. 7 is a flowchart showing an example of the step of manufacturing the QD composition-containing liquid shown in FIG. 6.

[0143] In the following, a case where the initial ligand is the organic compound 34 and the organic compound 34 contained in the initially obtained QD composition-containing liquid by synthesis or commercially is substituted with a metal fluoro complex will be described as an example.

[0144] In the above ligand substitution step, first, QD32 having the organic compound 34 coordinated to the surface of the above QD32 is isolated from the initially obtained QD composition-containing liquid (step S21, isolation step).

[0145] In step S21, first, an initial QD composition-containing liquid is collected in a reaction vessel such as a centrifuge tube. The initial QD composition-containing liquid contains an initial QD composition containing QD32 and organic compound 34, and a solvent. A nonpolar solvent is used as the solvent.

[0146] Next, an excessive amount of a poor solvent is dropped into the initial QD composition-containing liquid in this reaction vessel to precipitate QD32 coordinated with organic compound 34 contained in the initial QD composition-containing liquid. As the poor solvent, a solvent in which QD32 does not disperse, such as ethanol, is used. Next, centrifugation is performed to remove the supernatant.

[0147] Next, the precipitated QD32 is washed to isolate the precipitated QD32 (that is, QD32 coordinated with organic compound 34). The washing of the QD32 is performed by repeating a plurality of times the operation of adding a nonpolar solvent to the precipitated QD32 again to redisperse the QD32, then adding the poor solvent again and performing centrifugation to remove the supernatant. Thereby, excess organic ligands not coordinated to QD32 contained in the initial QD composition-containing liquid can be removed.

[0148] Next, a nonpolar solvent is added again as a solvent to the QD32 in the reaction vessel isolated in step S21 to redisperse the QD32 in the solvent (nonpolar solvent) (step S22, redispersion step). Thereby, a QD composition-containing liquid containing QD32, the organic compound 34 coordinated to the QD32, and the solvent (nonpolar solvent) is obtained.

[0149] Next, a trace amount of a metal fluoro complex compound solution in which a metal fluoro complex compound is dissolved in a polar solvent (for example, ethanol), as a ligand solution containing a metal compound 33 as a ligand and a solvent, is added to the QD composition-containing liquid in the reaction vessel and stirred. Then, the reaction solution in the reaction vessel is allowed to stand for a predetermined time. Thereby, a ligand exchange reaction is performed to substitute at least a part of the organic compound 34 contained in the initial QD composition with a metal fluoro complex which is one kind of the metal compound 33 (step S23, ligand substitution step).

[0150] Incidentally, the concentration of the metal fluoro complex compound in the above metal fluoro complex solution, the addition amount of the above metal fluoro complex solution, and the time required for the above stirring and standing still, etc., each condition used for the above ligand substitution is not particularly limited. These conditions may be appropriately set according to the materials used and the like so that the ratio of the metal compound 33 to the total amount of the organic compound 34 and the metal compound 33 in the obtained QD composition 31 becomes a desired ratio.

[0151] Next, an excessive amount of a poor solvent is dropped again into the above reaction vessel. Then, centrifugation is performed to remove the supernatant. Thereby, the excess metal fluoro complex and the solvent that are not coordinated to QD32 and are contained in the above supernatant are removed, and the QD composition 31 containing QD32 and the metal fluoro complex and the organic compound 34 present on the surface of the above QD32 are separated (step S24, QD composition separation step).

[0152] Thereafter, a polar solvent is added as the solvent 42 into the above reaction vessel, and the above QD composition 31 is dispersed in the polar solvent (step S25, QD composition dispersion step). Thereby, a QD composition-containing liquid 41 containing the QD composition 31 and the solvent 42 can be obtained.

[0153] FIG. 8 is a flowchart showing an example of step S4 (light-emitting layer formation step).

[0154] In step S4, first, the above QD composition-containing liquid 41 is applied onto HTL22 to form a coating film of the above QD composition-containing liquid 41 (step S31, QD composition-containing liquid application step). Incidentally, as the method for forming the coating film, any method such as a bar coating method, a spin coating method, an inkjet method, etc. can be appropriately selected. Next, the above coating film is heated and dried or the like to remove the solvent 42 (step S32, solvent removal step). Thereby, for example, an EML23 containing the QD composition 31 shown in FIG. 3 can be formed.

[0155] FIG. 9 is a flowchart showing another example of step S4 (light-emitting layer formation step).

[0156] As described above, in order to facilitate carrier injection, it is desirable that the content ratio of the organic compound 34 in the QD composition 31 is low or the QD composition 31 does not contain the organic compound 34. Therefore, when the QD composition-containing liquid 41 contains the organic compound 34, as shown in FIG. 9, after removing the solvent in step S32 to form a thin film containing the QD composition 31, an additional ligand substitution (step S33, ligand substitution step) may be performed.

[0157] Ligand substitution in the thin film state can be performed, for example, as follows. First, as a ligand solution, a metal fluoro complex compound solution in which a metal fluoro complex compound is dissolved in a polar solvent (for example, ethanol) is supplied to the thin film by spin coating or the like. Instead of supplying the metal fluoro complex compound solution by spin coating or the like, the substrate on which the thin film is formed may be immersed in the metal fluoro complex compound solution. Next, if necessary, it is washed with a rinsing solution to remove the organic compound 34 and the excess metal fluoro complex compound that are not coordinated to the QD 32. Then, the solvent is removed by heating and drying or the like.

[0158] In this way, by performing an additional ligand substitution process after forming the thin film, the amount of ligand substitution may be increased. Thereby, for example, the EML 23 shown in FIG. 1 can be formed.

[0159] However, the above illustration is just an example. In the step S11 (QD composition-containing liquid manufacturing step), by appropriately adjusting the ligand substitution conditions, EML23 shown in FIG. 1 can also be formed. Further, after applying the initial QD composition-containing liquid to form a thin film, the ligand substitution may be performed by supplying the metal fluoro complex compound solution to the thin film. That is, the QD composition according to the present embodiment is manufactured by removing the solvent, for example, in the step S24 (QD composition separation step) or the step S32 (solvent removal step) after at least a part of the organic compound 34 contained in the initial QD composition-containing liquid is ligand-substituted. Further, the QD composition according to the present embodiment may be manufactured by ligand substitution of the organic compound 34 contained in the initial QD composition without solvent, such as performing the above ligand substitution after thinning the initial QD composition as described above.

[0160] 〔Embodiment 2〕 Other embodiments of the present disclosure will be described below. For convenience of explanation, members having the same functions as the members described in the above embodiment are given the same reference numerals, and the description thereof will not be repeated. In the present embodiment, the differences from Embodiment 1 will be described.

[0161] FIG. 10 is a diagram schematically showing a schematic configuration of the light-emitting element 1 according to the present embodiment, partially enlarged.

[0162] As shown in FIG. 10, the QD composition 31 according to the present embodiment contains a metal compound 33 containing a metal oxide containing fluorine. Note that FIG. 10 illustrates a case where the QD composition 31 contains a metal oxide containing fluorine and a metal fluoro complex.

[0163] For example, ZnF4 2- from which Zn(OH)2 is generated, the F of the metal fluoro complex - is OH - The metal hydroxide generated by substitution with causes a decrease in quantum efficiency and a decrease in carrier injection property due to the deactivation of QD32, as described in Embodiment 1.

[0164] As described in Embodiment 1, the OH substitution tendency of the metal fluoro complex in an aqueous solution is indicated by the complex stability constant. The greater the complex stability constant K of the metal element, the more stable the bond with F - is, and the more difficult it is for F - to be substituted by OH - . On the other hand, the smaller the complex stability constant K of the metal element, the less stable the bond with F - is, and the easier it is for F - to be substituted by OH - .

[0165] Most metal species form metal hydroxides. Due to the substitution of F - in the metal fluoro complex by OH - , the metal fluoro complex coordinated on the surface of QD32 changes into a hydroxy (hydroxide) complex.

[0166] However, depending on the metal species, the hydroxy complex and the metal hydroxide formed by the dehydration reaction of the hydroxy complex are unstable. Therefore, when some metal fluoro complexes are substituted by OH - , further dehydration reactions proceed to form metal oxides.

[0167] - As an example, for instance, when Ti, Sn, V, and Si are substituted by OH, they form TiO2, SnO2, V2O3, and SiO2, respectively, through dehydration reactions.

[0168] Such reactions are more likely to occur at the heterogeneous field of the QD / solution interface than in the homogeneous field within the solution, and metal oxides preferentially precipitate on the surface of QD32. Therefore, a shell of the above metal oxide covering the surface of QD32 is formed by the above reaction. Note that, as a characteristic of the metal oxide formed by the hydrolysis reaction and dehydration reaction of the metal fluoro complex, the metal oxide contains fluorine. That is, fluoride ions remain in the metal oxide formed by the hydrolysis reaction and dehydration reaction of the metal fluoro complex.

[0169] ​Such a shell made of metal oxide protects QD32 against the intrusion of excess OH - . Therefore, it is desirable that the metal fluoro complex contains a metal element that forms a metal oxide by hydrolysis. Thereby, a metal oxide is formed on the surface of QD32 (for example, the surface of shell 32b), and QD32 can be protected against the intrusion of excess OH - .

[0170] In addition, in order to form a hydroxy complex that is a precursor to metal hydroxide and metal oxide, as described above, the complex stability constant K needs to be 20.0 or less. As described above, when the complex stability constant K exceeds 20.0, the substitution of OH - itself hardly occurs. For example, metal fluoro complexes such as B, P, and Al are stable as complexes and do not form either metal hydroxide or metal oxide.

[0171] Among the metal elements that form hydroxy complexes, the metal elements for which the hydroxy complex is unstable and forms a metal oxide by dehydration reaction are, for example, Ti, Sn, V, and Si.

[0172] In addition, the precipitated metal oxide is preferably a material that does not hinder carrier injection in the light-emitting element 1. Among the above elements, Ti, Sn, and V are more preferable than Si having a large band gap.

[0173] Therefore, the metal element contained in the metal compound 33 is preferably at least one selected from the group consisting of Ti, Sn, V, and Si, and more preferably at least one selected from the group consisting of Ti, Sn, and V.

[0174] For this reason, the metal fluoro complex is TiF6 2- , SnF6 2- , VF6 - , and SiF6 2-It is preferable to contain at least one selected from the group consisting of. Further, since the carrier conductivity of the metal oxide formed on the surface of QD32 is good, the above metal fluoro complex is TiF6 2- , SnF6 2- , and VF6 - It is more preferable to contain at least one selected from the group consisting of.

[0175] TiO2, SnO2, and V2O3 generated from a metal fluoro complex containing Ti, Sn, or V have high electron or hole conductivity. For example, TiO2 generated from TiF6 2- is an n-type semiconductor, has conductivity, and carriers can be effectively injected also in the light-emitting element 1.

[0176] FIG. 11 is a flowchart showing an example of the light-emitting layer formation step (step S4) in the method for manufacturing the light-emitting element 1 according to the present embodiment. In the method for manufacturing the light-emitting element 1 according to the present embodiment, in step S4, for example, after step S32 or step S33, metal oxide formation (step S34, metal oxide formation step) of the metal fluoro complex is performed. In FIG. 11, as an example, the case where step S34 is performed after step S33 is illustrated. Except for this, the method for manufacturing the light-emitting element 1 according to the present embodiment is the same as the method for manufacturing the light-emitting element 1 according to Embodiment 1.

[0177] Hereinafter, a method for forming a metal oxide from a metal fluoro complex in step S34 will be described with reference to FIG. 12.

[0178] FIG. 12 is a diagram schematically showing a process in which a shell of a metal oxide (hereinafter referred to as "metal oxide shell") is formed on the surface of QD32 by a metal fluoro complex. In FIG. 12, only the anion 33a of the metal compound 33 is illustrated, and the illustration of the cation 33b and fluoride ions contained in the finally formed metal oxide shell is omitted.

[0179] In step S34 described above, first, the substrate on which the thin film containing the QD composition 31 obtained in step S33 or step S32 is formed is immersed in, for example, a boric acid solution. Thereby, hydrolysis of the metal fluoro complex is performed. In FIG. 12, as an example, the metal fluoro complex is TiF6 2- is illustrated by taking the case where it is as an example.

[0180] When a boric acid solution is added to the QD composition 31 in which an unstable metal fluoro complex having a complex stability constant K lower than that of boron (B) is coordinated on the surface of QD32, as shown in FIG. 12, F - is gradually replaced by OH - . As a result, the metal fluoro complex (TiF6 2- ) coordinated on the surface of QD32 changes to a hydroxy complex (Ti(OH)6 2- ), and B(OH)4 - changes to BF4 - .

[0181] However, since Ti(OH)6 2- is unstable, it finally precipitates as a solid of metal oxide (in this case, TiO2) by a dehydration reaction. At this time, as described above, the reaction is more likely to occur in the non-uniform field at the QD / solution interface than in the uniform field in the solution, and the metal oxide preferentially precipitates on the surface of QD32. As a result, a metal compound shell composed of a metal compound 33 containing a metal oxide containing fluorine that covers the front surface of QD32 is formed. Note that the metal oxide shell may be formed in a state of being solidified on the surface of QD32. In FIGS. 10 and 12, the boundary between QD32 and the metal compound shell is shown by a dotted line, which indicates that it may or may not be possible to confirm the boundary between QD32 and the metal compound shell by analysis.

[0182] 〔Embodiment 3〕 (Application to a display device) As described above, the light-emitting element 1 according to Embodiments 1 and 2 may be used as a light source of a light-emitting device such as a display device. Hereinafter, the case where the light-emitting device according to the present embodiment is a display device will be described as an example.

[0183] FIG. 13 is a cross-sectional view showing an example of the schematic configuration of a main part of a display device 2 (light-emitting device) according to the present embodiment.

[0184] The display device 2 has a plurality of pixels. A light-emitting element 1 is provided in each pixel. The display device 2 includes, as a substrate 10, for example, an array substrate on which a TFT layer is formed, and on the substrate 10, a light-emitting element layer 4 including a plurality of light-emitting elements 1 having different emission wavelengths, a sealing layer 5, and a functional film 6 are laminated in this order.

[0185] The display device 2 shown in FIG. 13 includes, as pixels, a red pixel PR that emits red light, a green pixel PG that emits green light, and a blue pixel PB that emits blue light. An insulating edge cover 14 is provided between the pixels, which functions as a pixel separation film that covers the edge of the lower electrode (anode 11 in the example shown in FIG. 13) and separates adjacent pixels.

[0186] The edge cover 14 is formed, for example, by applying an organic material such as polyimide or acrylic resin and then patterning it by photolithography.

[0187] The display device 2 includes, as a plurality of light-emitting elements 1 having different emission wavelengths, a red light-emitting element that emits red light, a green light-emitting element that emits green light, and a blue light-emitting element that emits blue light. A red light-emitting element is provided as the light-emitting element 1 in the red pixel PR. A green light-emitting element is provided as the light-emitting element 1 in the green pixel PG. A blue light-emitting element is provided as the light-emitting element 1 in the blue pixel PB.

[0188] The red light-emitting element includes a red EML containing red QDs that emit red light as QD32, and has the EML as EML23. The green light-emitting element includes a green EML containing green QDs that emit green light as QD32, and has the EML as EML23. The blue light-emitting element includes a including blue QDs that emit blue light blue EML, and has the EML as EML23. The same light-emitting element 1 (the same pixel) includes the same type of QD32.

[0189] The light-emitting element layer 4 includes the plurality of light-emitting elements 1 provided for each pixel, and has a structure in which the respective layers of these light-emitting elements 1 are stacked on the substrate 10.

[0190] The substrate 10 is an array substrate, and a TFT layer, for example, is formed on the substrate 10 as a driving element layer. A pixel circuit including driving elements such as TFTs for controlling the light-emitting element 1 is provided in the TFT layer.

[0191] The light-emitting element layer 4 includes, for example, a plurality of anodes 11 constituting the light-emitting element 1, a cathode 13, a functional layer 12 provided between these anodes 11 and the cathode 13, and an insulating edge cover 14 covering the edges of the respective anodes 11. The anode 11 functions as a so-called pixel electrode (island-shaped lower electrode) and is provided in an island shape on the substrate 10 for each light-emitting element 1 (in other words, for each pixel). The cathode 13 is provided in a layer above the lower electrode via the functional layer 12 and the edge cover 14. The cathode 13 is provided in common for all the light-emitting elements 1 (in other words, for all the pixels) as a common electrode (common upper electrode). The light-emitting element 1 functions as a light source for lighting the respective pixels. The light-emitting element 1 may have the configuration shown in Embodiment 1 or may have the configuration shown in Embodiment 2.

[0192] The light-emitting element layer 4 is covered with a sealing layer 5. The sealing layer 5 has light-transmitting properties and includes, for example, a first inorganic sealing film 51, an organic sealing film 52, and a second inorganic sealing film 53 in this order from the lower layer side (i.e., the light-emitting element layer 4 side). However, it is not limited to this, and the sealing layer 5 may be formed of a single layer of an inorganic sealing film or a laminate of five or more layers of an organic sealing film and an inorganic sealing film. Further, the sealing layer 5 may be, for example, a sealing glass. By sealing the light-emitting element 1 with the sealing layer 5, penetration of water, oxygen, etc. into the light-emitting element 1 can be prevented.

[0193] The first inorganic sealing film 51 and the second inorganic sealing film 53 can each be formed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminate of these films formed by a CVD (chemical vapor deposition) method. The organic sealing film 52 is a light-transmitting organic film thicker than the first inorganic sealing film 51 and the second inorganic sealing film 53, and can be formed of, for example, an applicable photosensitive resin such as a polyimide resin or an acrylic resin.

[0194] Note that, as shown in FIG. 13, the display device 2 may include a functional film 6 having at least one of an optical compensation function, a touch sensor function, and a protection function on the sealing layer 5.

[0195] As described above, the display device 2 shown in FIG. 13 includes the light-emitting element 1 according to Embodiment 1 or Embodiment 2 as the light-emitting element 1 having different emission wavelengths. For this reason, the display device 2 includes a QD composition-containing layer containing the QD composition 31 as the EML 23. Therefore, according to the present embodiment, the same effects as those of Embodiment 1 or 2 can be obtained. For this reason, according to the present embodiment, a light-emitting device with high stability against OH groups, excellent long-term reliability, and high luminous efficiency can be provided.

[0196] In FIG. 13, the case where the light-emitting device is a display device has been described as an example. However, the present embodiment is not limited to this. The above light-emitting device only needs to include the light-emitting element 1 shown in Embodiment 1 or 2. Further, the above light-emitting device only needs to include a QD composition-containing layer containing the QD composition 31 shown in Embodiment 1 or 2.

[0197] For example, the above QD composition-containing layer may be a wavelength conversion layer of a wavelength conversion member, and the above light-emitting device may be a wavelength conversion member. Further, the display device may include the above wavelength conversion member as a photoelectric conversion unit.

[0198] In any case, according to the present embodiment, since the above light-emitting device includes a QD composition-containing layer containing the QD composition 31, it is possible to provide a light-emitting device having high stability against OH groups, excellent long-term reliability, and high luminous efficiency.

[0199] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Further, by combining the technical means disclosed in each embodiment, new technical features can be formed.

Explanation of Reference Numerals

[0200] 1 Light-emitting element 2 Display device 11 Anode 12 Functional layer 13 Cathode 23 EML (Emission layer) 31 QD composition (Quantum dot composition) 32 QD (Quantum dot) 32a Core 32b Shell 33 Metal compound 33a Anion 33b Cation 34 Organic compound 41 Quantum dot composition-containing liquid 42 Solvent

Claims

1. A quantum dot composition comprising at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine, and wherein the metal compound and the quantum dot each contain at least one metal element, the complex stability constant of at least one metal element contained in the metal compound in an aqueous solution of the metal fluoro complex is greater than the complex stability constant of at least one metal element contained in the quantum dot in an aqueous solution of the metal fluoro complex, and the complex stability constant of at least one metal element contained in the metal compound in an aqueous solution of the metal fluoro complex is in the range of 0.1 or more and 20.0 or less.

2. A quantum dot composition comprising a quantum dot and an organic compound, wherein at least a part of the organic compound is replaced with at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine, wherein the metal compound and the quantum dot each contain at least one metal element, the complex stability constant of at least one metal element contained in the metal compound in an aqueous solution of the metal fluoro complex is greater than the complex stability constant of at least one metal element contained in the quantum dot in an aqueous solution of the metal fluoro complex, and the complex stability constant of at least one metal element contained in the metal compound in an aqueous solution of the metal fluoro complex is in the range of 0.1 or more and 20.0 or less.

3. The quantum dot composition according to claim 2, wherein, after at least a part of the organic compound in a quantum dot composition-containing liquid containing the quantum dot composition and the organic compound and a solvent is replaced with the metal compound, the solvent contained in the quantum dot composition-containing liquid is removed.

4. The complex stability constant of at least one metal element contained in the metal compound in an aqueous solution of the metal fluoro complex is in the range of 1.2 or more and 19.0 or less, according to any one of claims 1 to 3.

5. The complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above metal compound is 0.1 or more greater than the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above quantum dots. The quantum dot composition according to any one of claims 1 to 4, characterized in that.

6. The complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above metal compound is 1.5 or more greater than the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above quantum dots. The quantum dot composition according to any one of claims 1 to 4, characterized in that.

7. The complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above metal compound is 2.5 or more greater than the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the above quantum dots. The quantum dot composition according to any one of claims 1 to 4, characterized in that.

8. The above quantum dots include a core and at least one layer of shell. The quantum dot composition according to any one of claims 1 to 7, characterized in that.

9. wherein the core contains at least one of Cd ｘ１ Zn １－ｘ１ Se ｙ１ S １－ｙ１ wherein (0 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 1) and In ｘ２ Ga １－ｘ２ P (0 ≤ x2 ≤ 1), The above shell contains Cd ｘ３ Zn １－ｘ３ Se ｙ３ S １－ｙ３ (0 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 1) and MO ｘ４ (0 < x4 ≤ 3, M represents a metal element), and contains at least one of the metal oxides represented thereby. Among the at least one metal element contained in the above metal compound, the complex stability constant in an aqueous solution of the metal fluoro complex of the metal element most contained in the above metal compound is greater than the complex stability constant in an aqueous solution of the metal fluoro complex of the metal element most contained in the above shell. The quantum dot composition according to claim 8, characterized in that.

10. The metal element contained in the above metal compound is at least one selected from the group consisting of Ti, Sn, V, and Si. The quantum dot composition according to any one of claims 1 to 9, characterized in that.

11. The metal element contained in the above metal compound is at least one selected from the group consisting of Ti, Sn, and V. The quantum dot composition according to any one of claims 1 to 10, characterized in that.

12. The above metal fluoro complex contains a metal element that generates a metal oxide by hydrolysis. The quantum dot composition according to any one of claims 1 to 11, characterized in that.

13. The above metal fluoro complex is TiF ６ ２－ , SnF ６ ２－ , and VF ６ － The quantum dot composition according to any one of claims 1 to 12, characterized by containing at least one selected from the group consisting of

14. A quantum dot composition-containing liquid characterized by containing the quantum dot composition according to any one of claims 1 to 13.

15. A light-emitting device comprising a light-emitting layer containing the quantum dot composition according to any one of claims 1 to 13.

16. A light-emitting device comprising the light-emitting device according to claim 15.

17. A substitution step of substituting at least a part of the organic compound in the initial quantum dot composition containing a quantum dot and an organic compound with at least one metal compound selected from the group consisting of a metal fluoro complex, a metal fluoro complex containing a hydroxy group, and a metal oxide containing fluorine, wherein the quantum dot and the metal compound each contain at least one metal element, and the complex stability constant in an aqueous solution of a metal fluoro complex of at least one metal element contained in the metal compound is larger than the complex stability constant in an aqueous solution of a metal fluoro complex of at least one metal element contained in the quantum dot, and the complex stability constant in an aqueous solution of the metal fluoro complex of the at least one metal element contained in the metal compound is in the range of 0.1 or more and 20.0 or less. A method for producing a quantum dot composition, characterized by using a quantum dot and a metal compound.

18. The substitution step is performed by substituting at least a part of the organic compound in the quantum dot composition-containing liquid containing the quantum dot composition containing the quantum dot and the organic compound and a solvent with the metal compound, and The method for producing a quantum dot composition according to claim 17, further comprising a solvent removal step of removing the solvent contained in the quantum dot composition-containing liquid after the substitution step.

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