WO2025032681A1 - Colloidal solution, method for producing same, and display device - Google Patents

Abstract

The present disclosure achieves a quantum dot (QD) ink having good lightfastness and coating performance. A colloidal solution (1) comprises: a dispersion medium (100); and semiconductor nanoparticles and composite particles (10) dispersed in the dispersion medium (100) as dispersoids. The composite particles (10) comprise: semiconductor nanoparticles (11); and a matrix component (12) constituting a particulate phase that is immiscible with the dispersion medium (100). The content of the composite particles (10) is 50 mass% or less of the total amount of dispersoids.

Description

Colloidal solution, its manufacturing method and display device

This disclosure relates to a colloidal solution, its manufacturing method, and a display device.

Conventionally, various display devices equipped with light-emitting elements have been developed. Known examples of such light-emitting elements include OLEDs (Organic Light Emitting Diodes) and QLEDs (Quantum dot Light Emitting Diodes). The use of quantum dot technology in the manufacture of such light-emitting elements is also being considered. One example of quantum dot (QD) technology for manufacturing such display devices is a known QD ink that is used to manufacture a QD film containing a blue absorbing material, and that contains the blue absorbing material and 0.1 to 30% by mass of a scattering material (see, for example, Patent Document 1).

International Publication No. 2020/068379

In general, QD inks can be degraded by light absorption. In particular, degradation caused by light with high energy density is significant. When the QD ink contains particles that are much larger than QDs, such as the scattering materials mentioned above, the light is scattered, which is effective in suppressing degradation caused by irradiated light. However, the inclusion of further particles larger than QDs in the QD ink can degrade the application properties of the QD ink, and as a result, the desired functionality of the resulting film may be insufficient.

One aspect of the present disclosure aims to provide a technology that can realize a QD ink that has good light resistance and coating performance.

In order to solve the above problems, a colloidal solution according to one embodiment of the present disclosure is a colloidal solution containing a dispersion medium, and semiconductor nanoparticles and composite particles containing semiconductor nanoparticles dispersed in the dispersion medium as dispersoids, the composite particles having a matrix component that constitutes a particulate phase that is incompatible with the dispersion medium, and the content of the composite particles is 50% by mass or less of the total dispersoids.

In order to solve the above problems, a method for producing a colloidal solution according to one embodiment of the present disclosure suspends semiconductor nanoparticles, a dispersion medium, and a matrix component that is incompatible with the dispersion medium, and produces composite particles containing semiconductor nanoparticles in an amount of 50% by mass or less of the total dispersed matter, the composite particles being constituted by the matrix component and in which the particulate phase that is incompatible with the dispersion medium contains semiconductor nanoparticles.

Furthermore, a display device according to one embodiment of the present disclosure has a semiconductor functional layer formed by applying the above-mentioned colloidal solution and composed of the semiconductor nanoparticles.

According to one aspect of the present disclosure, it is possible to realize a QD ink that has good light resistance and coating performance. In addition, according to one aspect of the present disclosure, it is possible to provide a device having an excellent film made of such a QD ink.

FIG. 2 is a diagram showing a schematic diagram of the effect of light on a colloidal solution according to the present disclosure. FIG. 1 is a diagram showing the effect of light on a conventional colloidal solution of semiconductor nanoparticles. FIG. 1 is a schematic diagram illustrating a first embodiment of a composite particle in a colloidal solution according to the present disclosure. FIG. 2 is a schematic diagram showing a second embodiment of a composite particle in a colloidal solution according to the present disclosure. FIG. 1 is a diagram illustrating a display device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating a layer structure of a light-emitting element according to an embodiment of the present disclosure.

In an embodiment of the present disclosure, the light resistance of a colloidal solution containing semiconductor nanoparticles such as QDs is improved by further imparting light scattering properties to the colloidal solution, thereby reducing the amount of light and light density that strikes the colloidal solution.

[Colloidal solution]
The colloidal solution according to an embodiment of the present disclosure contains a dispersion medium, semiconductor nanoparticles, and composite particles.

[Dispersion medium]
The dispersion medium may be any liquid that can be used in the dispersion of semiconductor nanoparticles. The dispersion medium may be, for example, a liquid component used in the dispersion medium of a QD ink. For example, the dispersion medium may be a polar solvent, examples of which include water, N,N-dimethylformamide, dimethylsulfoxide, ethanol, isopropyl alcohol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. Alternatively, the dispersion medium may be a non-polar solvent, examples of which include hexane, octane, decane, dodecane, tetradecane, and toluene.

[Semiconductor nanoparticles]
Semiconductor nanoparticles are a type of dispersoid in a colloidal solution, and are dispersed as dispersoid in a dispersion medium. Semiconductor nanoparticles are inorganic or organic particles that exhibit semiconductor performance, and are also nano-sized particles. Examples of semiconductor nanoparticles include nano-sized particles of Si, PbS, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, ZnSeTe, AIGS, ZnO, MgZnO, AlZnO, LiZnO, and NiO. Semiconductor nanoparticles may be particles with a core-shell structure. For example, semiconductor nanoparticles may have the above-mentioned particles as core particles and a shell layer covering them, and may be particles that exhibit semiconductor performance as a whole. The shell layer is composed of a component different from that of the core particle.

The particle size of the semiconductor nanoparticles is, for example, an average particle size, and can be measured, for example, by observation with a transmission electron microscope. In general, the smaller the particle size of the semiconductor nanoparticles, the more preferable it is, and for example, the average particle size may be 30 nm or less, 20 nm or less, or 15 nm or less. There is no lower limit to the particle size of the semiconductor nanoparticles, but it can be, for example, 10 nm or more.

The structure of the semiconductor nanoparticles is not limited, and they may have ligands. For example, the semiconductor nanoparticles may be core-shell particles having a shell layer composed of zinc halide containing 10 mol % or more of zinc. Semiconductor nanoparticles of this structure form clusters with some of the other ligands, such as xanthogenates, and enhance light scattering while filling the zinc vacancies in the shell with the other ligands, thereby maintaining good optical properties of the semiconductor nanoparticles.

[Composite particles]
The composite particles contain the semiconductor nanoparticles and a matrix component. The matrix component is a component that constitutes a particulate phase that is incompatible with the dispersion medium. The matrix component will be described later.

In the colloidal solution according to the present disclosure, the content of the composite particles is 50% by mass or less of the total dispersed matter. The content of the composite component may be an amount capable of scattering the light irradiated to the colloidal solution so as to sufficiently suppress the light degradation described below, and may be appropriately determined depending on the light irradiated or the light resistance of the semiconductor nanoparticles. From this perspective, the content of the composite component may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less.

<Matrix components>
The matrix component is appropriately selected from components that can form a particulate phase that is incompatible with the dispersion medium, depending on the type of the dispersion medium in the colloidal solution. For example, when the dispersion medium is a polar solvent, the matrix component can be an alkoxysilane. When the matrix component is an alkoxysilane, the semiconductor nanoparticles preferably have a silane-based ligand that has affinity for the alkoxysilane.

In addition, when the dispersion medium is a non-polar solvent, the matrix component may be a component containing a polar solvent of less than 10% by mass relative to the dispersion medium. In this case, the content of the polar solvent is sufficient as long as it can form a particulate liquid phase in the dispersoid, and may be 5% by mass or less, or 3% by mass or less relative to the dispersion medium, within the range in which such a liquid phase is formed. In this case, it is preferable that the matrix component further contains a ligand of the semiconductor nanoparticles or a component having affinity therefor.

The matrix component may be another component used in place of the above components or in combination with the above components. For example, the matrix component may further contain xanthogenic acids. The matrix component further contains xanthogenic acids, which is preferable from the viewpoint of enhancing the stability of the semiconductor nanoparticles in the colloidal solution by multidentate coordination with the semiconductor nanoparticles. The xanthogenic acids may be one or more types, and examples of xanthogenic acids include zinc methylxanthogenate, zinc ethylxanthogenate, zinc isopropylxanthogenate, and zinc butylxanthogenate.

The content of xanthogenic acids in the colloidal solution can be appropriately determined within a range in which the above-mentioned effects can be obtained. For example, it is preferable that the mass-based content of xanthogenic acids is more than half the mass of the semiconductor nanoparticles content relative to the semiconductor nanoparticles content. In addition, in terms of the content in the colloidal solution, the content of xanthogenic acids is preferably 1 mass% or more.

The upper limit of the xanthogenic acid content can be appropriately determined within the range in which the above-mentioned effects can be obtained, and may be, for example, 200% by mass or less of the semiconductor nanoparticle content, or 100 mg/ml or less in the colloidal solution.

The matrix component may further contain a zinc halide. Similar to the case where the matrix component further contains a xanthogenic acid, the case where the matrix component further contains a zinc halide is also preferable from the viewpoint of enhancing the stability of the semiconductor nanoparticles. The zinc halide may be one or more kinds, and examples of the zinc halide include zinc fluoride, zinc chloride, zinc iodide, and zinc bromide.

The amount of zinc halide contained in the colloidal solution can be determined as appropriate within a range that provides the above-mentioned effects. For example, it is preferable that the mass-based content of zinc halide is more than half the mass of the semiconductor nanoparticles. In addition, in terms of the content in the colloidal solution, the zinc halide content is preferably 1 mass% or more.

The upper limit of the zinc halide content can be appropriately determined within the range in which the above-mentioned effects can be obtained, and may be, for example, 50% by mass or less of the semiconductor nanoparticle content, or 25 mg/ml or less in the colloidal solution.

[Other ingredients]
The colloidal solution of the present disclosure may further contain other components than the above-mentioned components within the range in which the effects of the present disclosure can be obtained. Examples of such other components include conventional scattering materials. Conventional scattering materials are, for example, metal oxide particles with a diameter of 100 nm or more, and examples thereof include titanium oxide particles, zirconium oxide particles, aluminum oxide particles, and zinc oxide particles. In the case where the scattering material is further contained, the colloidal solution may be used after removing the scattering material by filtration. In the present disclosure, the colloidal solution may further contain a rigid medium such as the scattering material.

The content of the scattering material can be appropriately determined within the range in which scattered light can be obtained, for example, 50 mass% or less of the total medium in the colloidal solution. Even in such a form, photodegradation of the colloidal solution can be suppressed by light scattering, and the stability of the colloidal solution can be improved.

However, in the present disclosure, the aforementioned composite particles can suppress photodegradation of the colloidal solution by scattering light. Therefore, the colloidal solution of the present disclosure does not need to substantially contain a rigid medium such as a scattering material.

[Light scattering properties]
The colloid particles have light scattering properties due to the composite particles. The composite particles can be produced according to the light to be scattered. For example, the composite particles have light scattering properties for light of a wavelength absorbed by the semiconductor nanoparticles. The wavelength of light absorbed by the semiconductor nanoparticles can be determined by measuring the light absorption characteristics of a colloidal solution containing only semiconductor nanoparticles as dispersoids. It is preferable that the composite particles have such light scattering properties from the viewpoint of fully expressing the light resistance of the colloidal solution.

The wavelength of light absorbed by semiconductor nanoparticles may be 300 nm or more. In this case, it is effective from the viewpoint of preventing photodegradation of semiconductor nanoparticles in a colloidal solution against light that is abundant in the natural world.

The composite particles only need to have a particle size substantially larger than the wavelength of light absorbed by the semiconductor nanoparticles. The particle size of the composite particles can be measured, for example, by dynamic light scattering. The particle size of the composite particles can be adjusted by the type or amount of the matrix components. For example, the volume-based median kinetic diameter of the colloidal solution may be equal to or greater than the wavelength of the light. The kinetic diameter of the colloidal solution refers to the particle size of the composite particles. It is preferable for the volume-based median kinetic diameter to be equal to or greater than the wavelength of the light in order to enhance the scattering of the light absorbed by the semiconductor nanoparticles.

Furthermore, when a film having an average thickness of 50 nm is produced by spin-casting the colloidal solution, the arithmetic mean roughness Ra of the film may be 50 nm or less. A Ra of 50 nm or less is preferable from the viewpoint of suppressing photodegradation of the colloidal solution by light scattering and increasing the photostability of the colloidal solution. The smaller Ra is, the more preferable it is within the range in which the effects of the present disclosure can be obtained. From this viewpoint, it may be 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less.

The colloidal solution of the present disclosure may have a ratio of primary particles larger than twice the average diameter of the semiconductor nanoparticles of less than 5 volume % relative to the semiconductor nanoparticles. The average diameter here refers to the median diameter based on volume. Additionally, primary particles refer to the particle diameter of the semiconductor nanoparticles. Such a colloidal solution is advantageous from the viewpoint of achieving the above-mentioned Ra.

Furthermore, the haze of the colloidal solution of the present disclosure at an optical path length of 1 cm may be 5% or more. Colloidal solutions usually have a cloudy appearance because the composite particles exhibit light scattering properties. The haze can be appropriately determined within a range in which the light scattering effect of the composite particles is fully exhibited, and from this viewpoint, it may be 10% or more, or 20% or more. From the viewpoint of exhibiting light scattering properties, the haze need only be sufficiently high, and the upper limit of the haze may be appropriately set to a value greater than 5% as necessary within a range in which the effects of the present disclosure can be obtained.

Here, FIG. 1 is a diagram showing a schematic diagram of the effect of light on the colloidal solution according to the present disclosure. The colloidal solution CS according to the present disclosure contains composite particles as described above. The composite particles have a sufficiently large particle size compared to semiconductor nanoparticles because the semiconductor nanoparticles and the matrix component constitute liquid phase particles that are incompatible with the dispersoid. Therefore, even if the colloidal solution CS is irradiated with the irradiation light Li, the irradiation light Li is scattered by the composite particles and becomes scattered light Ls, and does not substantially reach the depths of the colloidal solution CS. Therefore, the region Aa where photodegradation of the semiconductor nanoparticles occurs due to irradiation with the irradiation light Li does not occur or is sufficiently limited.

Figure 2 is a diagram showing the effect of light on a conventional colloidal solution of semiconductor nanoparticles. Assume that this colloidal solution CS does not contain any scattering material. When the colloidal solution CS is irradiated with irradiation light Li, the irradiation light Li passes through the colloidal solution CS. This is because the particle size of the semiconductor nanoparticles is sufficiently small compared to the wavelength of the irradiation light Li. Therefore, photodegradation of the semiconductor nanoparticles occurs in the vicinity of the irradiation light Li irradiated onto the colloidal solution CS, and the area Aa where this photodegradation occurs is widespread in the colloidal solution CS.

[Method for producing colloidal solution]
The colloidal solution of the present disclosure can be produced by gently agglomerating some of the semiconductor nanoparticles in a dispersion of the semiconductor nanoparticles. That is, the colloidal solution of the present disclosure can be produced by suspending the semiconductor nanoparticles, a dispersion medium, and a matrix component that is incompatible with the dispersion medium, and producing composite particles containing semiconductor nanoparticles, in which the particulate phase that is incompatible with the dispersion medium and is constituted by the matrix component contains the semiconductor nanoparticles, in an amount of 50% by mass or less of the total dispersed matter.

The manufacturing method may further include a step of adding one or more components selected from the group consisting of zinc halide, mercaptosilane, and xanthogenic acids to the semiconductor nanoparticles or a dispersion thereof to obtain a slurry, from the viewpoint of introducing desired ligands into the semiconductor nanoparticles. The dispersoids in the slurry are used for the semiconductor nanoparticles to be suspended in a dispersion medium. By introducing these ligands into the semiconductor nanoparticles, the colloidal solution can be kept in a stable state, and products using the colloidal solution can be manufactured with a high yield.

The introduction of the ligand may be a replacement of the above-mentioned ligand, or may be an addition. That is, if the semiconductor nanoparticles have a ligand from the beginning, the original ligand may be removed and then the above-mentioned ligand may be added. Alternatively, the above-mentioned ligand may be added to the semiconductor nanoparticles when the semiconductor nanoparticles have a ligand from the beginning, so that a portion of the above-mentioned ligand is introduced into the semiconductor nanoparticles.

The manufacturing method may further include a step of filtering the produced colloidal solution. Including this step is preferable from the viewpoint of enabling the manufacture of products using the colloidal solution with a high yield.

(First Aspect)
3 is a diagram showing a first embodiment of a composite particle in a colloidal solution according to the present disclosure. The colloidal solution 1 includes a dispersion medium 100 and a composite particle 10 formed therein. The composite particle 10 includes semiconductor nanoparticles 11 and a matrix component 12. Note that the semiconductor nanoparticles 11 that do not constitute the composite particle 10 in the dispersion medium 100 are omitted in FIG. 3.

In the first embodiment, the dispersion medium 100 is a polar solvent, such as water, ethanol, or DMF. The semiconductor nanoparticles 11 are, for example, QDs having mercaptosilane (e.g., (3-mercaptopropyl)triethoxysilane) as a ligand. The matrix component 12 is, for example, an alkyl silicate (CxHyOzSiw, e.g., tetramethylorthosilicate).

The semiconductor nanoparticles 11 and the matrix components 12 are loosely spaced close to each other and behave as a group, forming composite particles 10. Composite particles 10 are flexible, although they act as a refractive index boundary on the μm scale, causing light scattering. Therefore, they do not interfere with the coating and film formation.

In this way, large micelles (composite particles 10) are formed in colloid solution 1, which increases the intensity of light scattering and further improves the light resistance of the colloid solution. For example, colloid solution 1 exhibits light scattering properties with a haze of about 20% in a solution with an optical path length of 1 cm, and can achieve a median volume ratio of the kinetic diameter that is equal to or greater than the wavelength of light absorbed by semiconductor nanoparticles 11. In this way, colloid solution 1 exhibits strong light scattering, and its light resistance is further improved.

(Second Aspect)
FIG. 4 is a schematic diagram showing a second embodiment of a composite particle in a colloidal solution according to the present disclosure.
The colloidal solution 2 contains a dispersion medium 200 and a composite particle 20 formed therein. The composite particle 20 contains a semiconductor nanoparticle 11 and matrix components 22A and 22B. Note that the semiconductor nanoparticles 11 in the dispersion medium 200 are omitted in Fig. 4.

In the second embodiment, the dispersion medium 200 is a non-polar solvent, such as toluene. The semiconductor nanoparticles 11 are QDs having, for example, mercaptosilane (e.g., (3-mercaptopropyl)triethoxysilane) as a ligand. The matrix component 22A is a polar solvent, such as water. The matrix component 22B is, for example, mercaptosilane or its reaction product with water. The mercaptosilane is the same as the ligand of the semiconductor nanoparticles 11.

The semiconductor nanoparticles 11 and the matrix components 22A and 22B are loosely spaced close to each other and behave as a group, forming a composite particle 20. As in the first embodiment, the composite particle 20 forms a refractive index boundary surface on the μm scale that causes light scattering, but it is flexible. Therefore, it does not interfere with the coating and film formation.

Similar to the colloidal solution, colloidal solution 2 exhibits light scattering properties with a haze of about 20% in a solution with an optical path length of 1 cm, and the median volume ratio of the dynamic diameter can be realized to be equal to or greater than the wavelength of light absorbed by semiconductor nanoparticles 11. Therefore, colloidal solution 2 also exhibits strong light scattering, and its light resistance is further improved.

Furthermore, the composite particles 20 of the colloidal solution 2 contain water as a matrix component. Therefore, it is easy to form large micelles (flexible), which is more advantageous from the viewpoint of increasing the light scattering intensity and improving light resistance.

[Display Device]
The display device of the present disclosure has a semiconductor functional layer formed by coating the above-mentioned colloidal solution and composed of semiconductor nanoparticles. The semiconductor functional layer may contain the above-mentioned matrix components, reaction products of the matrix components in the colloidal solution, or residues thereof.

The content of organic components in the semiconductor functional layer is preferably small from the viewpoint of fully expressing the desired function of the semiconductor functional layer. The organic components are ligands of the organic components possessed by the semiconductor nanoparticles, their free products, or their residues. From the above viewpoint, the content of organic components in the semiconductor functional layer may be 10 vol.% or less, 5 vol.% or less, or 3 vol.% or less. In addition, as for the composition of the semiconductor functional layer, for example, 90 vol.% or more of the semiconductor functional layer is composed of a reaction product of the semiconductor nanoparticles and the matrix component, and the reaction product of the matrix component may be silicon oxide or zinc sulfide. In such a semiconductor functional layer, deterioration of the semiconductor functional layer due to electric current or light is further suppressed, which is preferable from the viewpoint of extending the life of the display device.

The film thickness of the semiconductor functional layer is thinner than the wavelength of visible light, and may be, for example, 100 nm or less, or 50 nm or less. From the viewpoint of the light-emitting characteristics of the display device, the arithmetic mean roughness Ra of the semiconductor functional layer is preferably less than the film thickness of the semiconductor functional layer, more preferably less than half the film thickness of the semiconductor functional layer, and even more preferably less than one-tenth the film thickness of the semiconductor functional layer.

The display device of the present disclosure is, for example, a full-color display device having light-emitting elements that emit light of each color of RGB, and at least one of the light-emitting elements of each color is fabricated using the colloidal solution of the present disclosure. The display device of the present disclosure can be configured in the same manner as known display devices that include light-emitting elements, except that it includes the light-emitting elements.

[Specific embodiment]
The display device and the light-emitting element included therein of the present disclosure will be further described below with reference to the drawings. In the following description, when the symbol R, G, or B representing each light-emitting color is added to the symbol, it means a configuration of a specific light-emitting color, and when the symbol representing each light-emitting color is not added, it means a configuration common to all colors regardless of the light-emitting color.

FIG. 5 is a schematic diagram of a display device according to an embodiment of the present disclosure. As shown in FIG. 5, the display device 50 includes a frame region NDA and a display region DA. The display region DA of the display device 50 includes a plurality of pixels PIX, each of which includes a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP. The red subpixel RSP includes a red light-emitting element, the green subpixel GSP includes a green light-emitting element, and the blue subpixel BSP includes a blue light-emitting element. In the stacking direction, the display device 50 has a configuration in which, for example, a substrate, a barrier layer, a thin-film transistor, a bank and a light-emitting element, a sealing layer, and a functional film are stacked in this order.

FIG. 6 is a diagram showing a schematic layer structure of a light-emitting element in this embodiment. As shown in FIG. 6, a light-emitting element 60 is disposed on a barrier layer 62 disposed on a substrate 61. The barrier layer 62 is formed of, for example, an insulator. A bank 63 is formed on the barrier layer 62 to separate the sub-pixels SP in the planar direction. The light-emitting element 60 is configured by stacking a first electrode 64, a hole injection layer 65, a hole transport layer 66, a light-emitting layer 67, an electron transport layer 68, and a second electrode 69 in this order. Examples of the light-emitting element 60 include an OLED and a QLED.

The first electrode 64 is also called an anode. The first electrode 64 is conductive and has optical properties, for example, of reflecting part of visible light and transmitting the rest. The first electrode 64 includes both an electrode material that reflects visible light and an electrode material that transmits visible light.

Examples of electrode materials that reflect visible light include metal materials such as Al, Mg, Li, and Ag, alloys of these metal materials, and laminates (e.g., ITO/Ag/ITO) of these metal materials or their alloys with transparent metal oxides (e.g., indium tin oxide (ITO), indium zinc oxide, or indium gallium zinc oxide). Examples of electrode materials that transmit visible light include transparent metal oxides, thin films made of metal materials such as Al and Ag, and nanowires made of these metal materials.

The first electrode 64 may be produced by a known method for producing an electrode layer in a light-emitting element. For example, the first electrode 64 may be produced by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. Examples of physical vapor deposition methods include vacuum deposition, sputtering, electron beam (EB) deposition, and ion plating. Examples of methods for patterning the first electrode 64 include photolithography and inkjet methods.

The hole injection layer 65 is comprised of a hole injection material capable of stabilizing the injection of holes into the light emitting layer 67. There may be one or more hole injection materials. Examples of hole injection materials include the encapsulated nickel oxide nanoparticles of the present disclosure, as well as poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT:PSS), Ni(OH) ₂ , and CuSCN.

The hole transport layer 66 is comprised of a hole transporting material capable of stabilizing the transport of holes into the light emitting layer 67. There may be one or more hole transporting materials. Examples of hole transporting materials include the encapsulated nickel oxide nanoparticles of the present disclosure, as well as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB), Ni(OH) ₂ , and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (poly-TPD).

In the present disclosure, the encapsulated nickel oxide nanoparticles of the present disclosure may be contained in only one of the hole injection layer 65 and the hole transport layer 66, or may be contained in both.

The hole injection layer 65 or hole transport layer 66 containing the encapsulated nickel oxide nanoparticles of the present disclosure may be prepared by applying an ink containing encapsulated nickel oxide nanoparticles. The hole injection layer 65 or hole transport layer 66 may be prepared by any known method for preparing a layer of a light-emitting element by applying an ink, except for using an ink containing encapsulated nickel oxide nanoparticles. For example, the hole injection layer 65 or hole transport layer 66 may be prepared by a slit coater or inkjet.

The encapsulated nickel oxide nanoparticles of the present disclosure are tiny and uniform nanoparticles, and are encapsulated by a host. Therefore, they are uniformly dispersed in the ink solvent. A solvent having appropriate wettability for the application area is selected as the ink solvent. By applying ink in which the encapsulated nickel oxide nanoparticles are uniformly dispersed, the encapsulated nickel oxide nanoparticles are uniformly applied to the application area, forming a flat layer. Therefore, in the present disclosure, a flat hole injection layer 65 or hole transport layer 66 can be formed by the encapsulated nickel oxide nanoparticles.

The light-emitting layer 67 may be composed of quantum dots (QDs). QDs refer to dots with a maximum width of 100 nm or less. The shape of the QDs may be a spherical three-dimensional shape (circular cross-sectional shape), or may be, for example, a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with uneven surfaces, or a combination of these.

The structure of the QDs may be, for example, a core structure, a core/shell structure, a core/shell/shell structure, or a core/shell structure with a continuously changing core/shell ratio. The QDs may have a ligand, and if the QDs have a core structure, the ligand may be provided on the surface of the core structure, and if the QDs have a shell structure, the ligand may be provided on the surface of the shell structure.

The materials that make up the core structure of the QDs include Si and C if they are unicomponent. The materials include CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, and ZnTe if they are binaries. The materials include CdSeTe, GaInP, and ZnSeTe if they are ternary. The materials include AIGS if they are quaternary.

The materials that make up the shell structure of the QDs include binary systems such as CdS, CdTe, CdSe, ZnS, ZnSe, and ZnTe. The materials that make up the shell structure of the QDs include ternary systems such as CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AIP.

The electron transport layer 68 is composed of an electron transporting material that can stabilize the transport of electrons into the light emitting layer 67. Examples of electron transporting materials include fine particles containing one or more elements selected from the group consisting of Zn, Mg, Ti, Si, Sn, W, Ta, Ba, Zr, Al, Y, and Hf.

The second electrode 69 is also called a cathode. The second electrode 69 is conductive, for example, conductive and transparent to visible light. Examples of electrode materials constituting the second electrode 69 include the above-mentioned electrode materials that transmit visible light, for example, ITO and Ag nanowires (NW). The second electrode 69 can be produced by the method described above for the first electrode 64, depending on the electrode material. From the viewpoint of simplifying the manufacturing process, the second electrode 69 is integrally formed on both the electron transport layer 68 and the bank 63. The second electrode 69 is formed on the electron transport layer 68, and does not necessarily have to be formed on the bank 63.

〔summary〕
In the case of preparing a semiconductor functional layer using the colloidal solution of the present disclosure, the composite particles form a phase incompatible with the dispersion medium, i.e., a particulate aggregate due to gentle aggregation. Therefore, when a force for forming a film is applied to the colloidal solution, the composite particles collapse, and the semiconductor nanoparticles and matrix components in the composite particles diffuse into the film. As a result, a semiconductor functional layer substantially composed of semiconductor nanoparticles is formed. The colloidal solution of the present disclosure, which realizes such a film formation mechanism, is advantageous for forming a thin film of the nm order for EL.

Furthermore, the colloidal solution of the present disclosure does not require filtration to remove light-scattering particles, as compared to conventional colloidal solutions containing scattering materials. Furthermore, since the composite particles are a flexible particulate aggregate, the composite particles can pass through the filter even when the colloidal solution is subjected to filtration capable of filtering out particles of the size of the composite particles.

Furthermore, in the colloidal solution of the present disclosure, the ligand of the semiconductor nanoparticles can be used as the matrix component. This can further enhance the functionality of the semiconductor nanoparticles in the semiconductor functional layer.

According to this disclosure, it is possible to realize a colloidal solution of semiconductor nanoparticles that has good light resistance and coating performance, and it is possible to increase the yield of products that have a semiconductor functional layer made of the semiconductor nanoparticles. This disclosure, which has such effects, is expected to contribute to the achievement of, for example, Goal 12 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Responsible Consumption and Production."

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

The colloidal solution of the present disclosure is useful as a coating material for producing a semiconductor functional layer substantially composed of semiconductor nanoparticles. The colloidal solution of the present disclosure is also useful as a technology for increasing the light scattering properties of a colloidal solution without adding a light scattering material.

1, 2, CS colloidal solution 10, 20 composite particle 11 semiconductor nanoparticle 12, 22A, 22B matrix component 100, 200 dispersion medium 50 display device 61 substrate 62 barrier layer 63 bank 64 first electrode 65 hole injection layer 66 hole transport layer 67 light emitting layer 68 electron transport layer 69 second electrode DA display area NDA frame area PIX pixel Aa area where photodegradation occurs Li irradiated light Ls scattered light

Claims (21)

A colloidal solution containing a dispersion medium, and semiconductor nanoparticles and composite particles containing semiconductor nanoparticles dispersed as dispersoids in the dispersion medium,
the composite particles have a matrix component that constitutes a particulate phase that is incompatible with the dispersion medium,
A colloidal solution in which the content of the composite particles is 50 mass % or less of the total dispersed matter. The colloidal solution according to claim 1, wherein the composite particles have light scattering properties for light having a wavelength absorbed by the semiconductor nanoparticles. The colloidal solution of claim 2, wherein the wavelength of the light is 300 nm or more. The colloidal solution according to claim 2 or 3, wherein the volume-based median kinetic diameter of the colloidal solution is equal to or greater than the wavelength of the light. The colloidal solution according to claim 1, wherein when a film having an average thickness of 50 nm is produced by spin-casting the colloidal solution, the arithmetic mean roughness Ra of the film is 50 nm or less. the semiconductor nanoparticles are core-shell particles having a shell layer composed of zinc halide containing 10 mol % or more of zinc,
10. The colloidal solution of claim 1 further comprising a zinc halide. The colloidal solution according to claim 1, further comprising xanthogenic acids. The colloidal solution according to claim 7, wherein the content by mass of the xanthogenic acids is more than half the content by mass of the semiconductor nanoparticles. The colloidal solution according to claim 7 or 8, wherein the content of the xanthogenic acids is 1% by mass or more. The dispersion medium is a polar solvent,
The colloidal solution according to any one of claims 1 to 9, wherein the matrix component comprises an alkoxysilane. The colloidal solution according to claim 10, wherein the mass content of the alkoxysilane is more than half the mass content of the semiconductor nanoparticles. The colloidal solution according to claim 10 or 11, wherein the content of the alkoxysilane is 1% by mass or more. The dispersion medium is a non-polar solvent,
The colloidal solution according to any one of claims 1 to 9, wherein the matrix component contains less than 10% by mass of a polar solvent relative to the dispersion medium. The colloidal solution of claim 13, wherein the matrix component further comprises a mercaptosilane. The colloidal solution according to claim 14, wherein the mass content of the mercaptosilane is greater than half the mass content of the semiconductor nanoparticles. The colloidal solution according to claim 14 or 15, wherein the content of the mercaptosilane is 1% by mass or more. A method for producing a colloidal solution, comprising suspending semiconductor nanoparticles, a dispersion medium, and a matrix component that is incompatible with the dispersion medium, and producing composite particles containing semiconductor nanoparticles, the composite particles being constituted by the matrix component and in which the particulate phase that is incompatible with the dispersion medium contains semiconductor nanoparticles, in an amount of 50% by mass or less of the total dispersed matter. The method further includes a step of adding one or more components selected from the group consisting of zinc halide, mercaptosilane, and xanthogenic acids to the semiconductor nanoparticles or the dispersion thereof to obtain a slurry,
18. The method for producing a colloidal solution according to claim 17, wherein a dispersoid in the slurry is used for the semiconductor nanoparticles to be suspended in the dispersion medium. The method for producing a colloidal solution according to claim 17 or 18, further comprising a step of filtering the produced colloidal solution. A display device having a semiconductor functional layer composed of the semiconductor nanoparticles formed by applying the colloidal solution according to any one of claims 1 to 16. The display device according to claim 20, wherein the content of organic components in the semiconductor functional layer is 10% by volume or less.

Images