Colloidal solution, method for producing same, and display device

Abstract

The present disclosure realizes a QD ink having good light resistance and coating performance. The colloidal solution (1) contains a dispersion medium (100), and semiconductor nanoparticles and composite particles (10) dispersed as dispersoids in the dispersion medium (100). The composite particles (10) comprise semiconductor nanoparticles (11) and a matrix component (12) that constitutes a particulate phase that is incompatible with a dispersion medium (100). The content of the composite particles (10) is 50% by mass or less of the total dispersoid.

Description

Technical Field

[0001] This disclosure relates to colloidal solutions, methods for manufacturing them, and display devices. Background Technology

[0002] In the past, various display devices incorporating light-emitting elements have been developed. Among these light-emitting elements are known OLEDs (Organic Light Emitting Diodes) and QLEDs (Quantum Dot Light Emitting Diodes). Furthermore, the use of quantum dot technology is being researched in the manufacture of these light-emitting elements. As an example of quantum dot (QD) technology used to manufacture such display devices, inks are known for manufacturing QD films containing a blue absorbing material, which contain the blue absorbing material and 0.1 to 30% by mass of a scattering material (see, for example, Patent Document 1).

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2020 / 068379 Summary of the Invention Typically, QD inks can degrade due to light absorption, especially from high-energy-density light. When the QD ink contains particles larger than QDs such as the aforementioned scattering materials, light is scattered, thus effectively suppressing degradation caused by irradiated light. However, the presence of particles larger than QDs in the QD ink can sometimes reduce its coating properties, resulting in the formed film sometimes failing to achieve the desired functionality.

[0004] One aspect of this disclosure is to provide a technique for achieving QD inks with good lightfastness and coating properties.

[0005] Methods for solving problems To address the aforementioned issues, one technical solution disclosed herein relates to a colloidal solution comprising: a dispersion medium; and composite particles, comprising semiconductor nanoparticles and composite particles containing semiconductor nanoparticles, wherein the semiconductor nanoparticles and the composite particles are dispersed as a dispersion phase in the dispersion medium, the composite particles having a matrix component constituting a particle-like phase incompatible with the dispersion medium, and the content of the composite particles being less than 50% by mass of the total dispersion phase.

[0006] In addition, in order to solve the above-mentioned problems, in a method for manufacturing a colloidal solution of one technical solution disclosed herein, semiconductor nanoparticles, a dispersion medium and a matrix component that is incompatible with the dispersion medium are suspended to generate a composite particle containing semiconductor nanoparticles in a particle-like phase composed of the matrix component and incompatible with the dispersion medium, wherein the amount of the composite particle generated is less than 50% by mass of the total dispersed mass.

[0007] Furthermore, a display device according to one of the technical solutions of this disclosure has a semiconductor functional layer, which is formed by coating the above-mentioned colloidal solution and is composed of the above-mentioned semiconductor nanoparticles.

[0008] Invention Effects According to one aspect of this disclosure, QD inks with good lightfastness and coating properties can be achieved. Furthermore, according to one aspect of this disclosure, an apparatus having an excellent film based on such QD ink can be provided. Attached Figure Description

[0009] Figure 1 A diagram schematically illustrating the effect of the colloidal solution of this disclosure on light.

[0010] Figure 2 This is a schematic diagram illustrating the effect of conventional semiconductor nanoparticles on the light in colloidal solutions.

[0011] Figure 3 This is a schematic diagram illustrating the first morphology of the composite particles in the colloidal solution of the present disclosure.

[0012] Figure 4 This is a schematic diagram representing the second morphology of the composite particles in the colloidal solution of the present disclosure.

[0013] Figure 5 This is a schematic diagram illustrating a display device according to an embodiment of the present disclosure.

[0014] Figure 6 This is a schematic diagram illustrating the layer structure of a light-emitting element in one embodiment of the present disclosure. Detailed Implementation

[0015] In embodiments of this disclosure, by further imparting light scattering properties to a colloidal solution containing semiconductor nanoparticles such as QD, the amount and density of light irradiated onto the colloidal solution are reduced, thereby improving the lightfastness of the colloidal solution.

[0016] <Colloidal solutions> The colloidal solutions of embodiments of this disclosure contain a dispersion medium, semiconductor nanoparticles, and composite particles.

[0017] [Dispersion medium] The dispersion medium can be any liquid suitable for use in the dispersion of semiconductor nanoparticles. For example, the dispersion medium can be a liquid component used in the dispersion medium of QD inks. The dispersion medium can also be a polar solvent, examples of which include water, N,N-dimethylformamide, dimethyl sulfoxide, ethanol, isopropanol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. Alternatively, the dispersion medium can be a non-polar solvent, examples of which include hexane, octane, decane, dodecane, tetradecane, and toluene.

[0018] [Semiconductor nanoparticles] Semiconductor nanoparticles are a type of dispersed phase in colloidal solutions, dispersed in a dispersion medium. Semiconductor nanoparticles are inorganic or organic particles that exhibit semiconductor properties and are nanoscale particles. Examples of semiconductor nanoparticles include nanoscale particles of Si, PbS, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, ZnSeTe, AlGS, ZnO, MgZnO, AlZnO, LiZnO, and NiO. Semiconductor nanoparticles can also be core-shell structured particles. For example, a semiconductor nanoparticle may be a particle having the aforementioned particles as a core and a shell covering it, exhibiting semiconductor properties as a whole. Furthermore, the shell may be composed of a different component than the core particle.

[0019] The particle size of semiconductor nanoparticles, such as the average particle size, can be measured, for example, by observation based on a transmission electron microscope. Smaller particle sizes are generally preferred; for example, the average particle size can be less than 30 nm, less than 20 nm, or less than 15 nm. Furthermore, there is no lower limit to the particle size of semiconductor nanoparticles; for example, it can be greater than 10 nm.

[0020] The structure of semiconductor nanoparticles is not limited and they can also contain ligands. For example, semiconductor nanoparticles can also be core-shell particles with a shell composed of zinc halides containing more than 10 mol% zinc. Semiconductor nanoparticles with this structure form clusters with a portion of other ligands such as xanthates. While enhancing light scattering, these other ligands fill the pores of the zinc shell, thereby effectively maintaining the optical properties of the semiconductor nanoparticles.

[0021] [Composite particles] The composite particles comprise the aforementioned semiconductor nanoparticles and a matrix component. The matrix component is the particulate phase that is incompatible with the dispersion medium. The matrix component will be discussed later.

[0022] In the colloidal solution disclosed herein, the content of the composite particles is 50% by mass or less of the total dispersed phase. The content of the composite component is sufficient to adequately suppress the light degradation described later and to reduce the light scattering irradiated onto the colloidal solution; it can be appropriately determined based on the irradiated light or the lightfastness of the semiconductor nanoparticles. From this perspective, the content of the composite component can be 40% by mass or less, 30% by mass or less, 20% by mass or less, or even 10% by mass or less.

[0023] <Matrix Composition> The matrix composition is appropriately determined based on the type of dispersion medium in the colloidal solution and on the components that can form a particulate phase incompatible with the dispersion medium. For example, when the dispersion medium is a polar solvent, the matrix composition may be an alkoxysilane. When the matrix composition is an alkoxysilane, the semiconductor nanoparticles preferably have silane-based ligands that have an affinity for that alkoxysilane.

[0024] Furthermore, when the dispersion medium is a non-polar solvent, the matrix component can be a component containing less than 10% by mass of a polar solvent relative to the dispersion medium. In this case, the amount of polar solvent is sufficient to form a particulate liquid phase in the dispersion; therefore, within the range of forming such a liquid phase, it can be less than 5% by mass or less than 3% by mass relative to the dispersion medium. In this case, it is preferable that the matrix component also contains ligands for semiconductor nanoparticles or components with an affinity for them.

[0025] The matrix component may also be other components used in place of the aforementioned components or in combination with the aforementioned components. For example, the matrix component may further contain xanthates. From the viewpoint of enhancing the stability of semiconductor nanoparticles in colloidal solutions through multidentate coordination of semiconductor nanoparticles, it is preferable that the matrix component also contains xanthates. The xanthates may be one or more, and examples of xanthates include zinc methyl xanthate, zinc ethyl xanthate, zinc isopropyl xanthate, and zinc butyl xanthate.

[0026] The content of xanthates in the colloidal solution can be appropriately determined within a range that achieves the aforementioned effects. For example, the mass basis content of xanthates is preferably more than half the mass basis content of semiconductor nanoparticles. Furthermore, in the case of the colloidal solution, the content of xanthates is preferably 1% by mass or more.

[0027] Furthermore, the upper limit of the xanthic acid content can be appropriately determined within the range that achieves the above-mentioned effects, for example, it can be less than 200% by mass of the semiconductor nanoparticle content, or it can be less than 100 mg / ml in the colloidal solution.

[0028] Furthermore, the matrix component may also contain zinc halides. The presence of zinc halides in the matrix component, similar to the presence of xanthates, is preferred from the viewpoint of enhancing the stability of the semiconductor nanoparticles. There may be one or more zinc halides; examples include zinc fluoride, zinc chloride, zinc iodide, and zinc bromide.

[0029] The content of zinc halide in the colloidal solution can be appropriately determined within a range that achieves the aforementioned effects. For example, the content of zinc halide, based on a mass ratio, is preferably more than half the content of semiconductor nanoparticles relative to the content of semiconductor nanoparticles. Furthermore, in the case of the colloidal solution, the content of zinc halide is preferably 1% by mass or more.

[0030] Furthermore, the upper limit of the zinc halide content can be appropriately determined within the range that achieves the above-mentioned effects, for example, it can be less than 50% by mass of semiconductor nanoparticles, or it can be less than 25 mg / ml in colloidal solutions.

[0031] [Other ingredients] The colloidal solution of this disclosure may further contain other components besides those described above, within the scope of the effects achieved by this disclosure. Examples of such other components include existing scattering materials. Existing scattering materials are, for example, metal oxide particles with a diameter of 100 nm or more, including titanium oxide particles, zirconium oxide particles, aluminum oxide particles, and zinc oxide particles. When further containing such a scattering material, the colloidal solution can be used after removing the scattering material by filtration. In this disclosure, the colloidal solution may further contain a rigid medium such as the scattering material.

[0032] The content of the scattering material can be appropriately determined within the range that allows for the acquisition of scattered light, for example, less than 50% by mass relative to the total medium in the colloidal solution. In this way, the photodegradation of the colloidal solution can also be suppressed by light scattering, thereby improving the stability of the colloidal solution.

[0033] However, in this disclosure, the aforementioned composite particles are able to suppress the light degradation of the colloidal solution due to light scattering. Therefore, the colloidal solution of this disclosure does not substantially contain a rigid medium such as a scattering material.

[0034] [Light scattering] Colloidal particles possess light-scattering properties based on composite particles. Composite particles can be fabricated according to the light to be scattered. For example, composite particles exhibit light-scattering properties for light of wavelengths absorbed by semiconductor nanoparticles. The wavelength of light absorbed by semiconductor nanoparticles is determined by measuring the light absorption characteristics of a colloidal solution containing only semiconductor nanoparticles as the dispersion phase. From the viewpoint of fully reflecting the lightfastness of the colloidal solution, composite particles with such light-scattering properties are preferred.

[0035] Semiconductor nanoparticles can absorb light with wavelengths above 300 nm. Therefore, from the perspective of preventing light degradation of semiconductor nanoparticles in colloidal solutions, this is effective for dealing with the abundant light contained in nature.

[0036] 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 component. For example, the median of the volumetric kinetic diameter of the colloidal solution can also be greater than or equal to the wavelength of the light. The kinetic diameter of the colloidal solution refers to the particle size of the composite particles. From the viewpoint of enhancing the scattering of light absorbed by the semiconductor nanoparticles, it is preferable that the median of the volumetric kinetic diameter is greater than or equal to the wavelength of the light.

[0037] Furthermore, when a film with an average thickness of 50 nm is fabricated by spin coating of a colloidal solution, the arithmetic mean roughness Ra of the film can be 50 nm or less. From the viewpoint of suppressing photodegradation of the colloidal solution through light scattering and improving the photostability of the colloidal solution, it is preferable that Ra is 50 nm or less. Within the range where the effects of this disclosure are obtained, the smaller Ra is, the more preferred. From this viewpoint, it can be 50 nm or less, 30 nm or less, 20 nm or less, or even 10 nm or less.

[0038] The colloidal solution disclosed herein contains a proportion of primary particles larger than a multiple of the average diameter of the semiconductor nanoparticles that can be less than 5% by volume relative to the semiconductor nanoparticles. Here, the average diameter refers to the median diameter on a volume basis. Furthermore, primary particles refer to the particle size of the semiconductor nanoparticles. Such a colloidal solution is advantageous from the viewpoint of achieving the aforementioned Ra.

[0039] Furthermore, the haze of the colloidal solution disclosed herein can be 5% or higher when the optical path length is 1 cm. Colloidal solutions typically have a cloudy appearance due to the light-scattering properties of the composite particles. The haze can be appropriately determined within a range that sufficiently demonstrates the light-scattering effect of the composite particles; from this perspective, it can be 10% or higher, or even 20% or higher. The haze only needs to be sufficiently high from the perspective of reflecting light scattering properties; as needed, an upper limit for the haze can be appropriately set within a range exceeding 5% while still achieving the effects of this disclosure.

[0040] Here, Figure 1This diagram schematically illustrates the effect of the colloidal solution of this disclosure on light. As described above, the colloidal solution CS of this disclosure contains composite particles. These composite particles, being particles of a liquid phase incompatible with the dispersed phase by semiconductor nanoparticles and matrix components, have a sufficiently large particle size than the semiconductor nanoparticles. Therefore, even when the colloidal solution CS is irradiated with illumination light Li, the illumination light Li is scattered by the composite particles, becoming scattered light Ls, which substantially cannot reach the depths of the colloidal solution CS. Therefore, the region Aa where photodegradation of the semiconductor nanoparticles occurs due to irradiation by illumination light Li either does not occur or is sufficiently defined.

[0041] Figure 2 This diagram schematically illustrates the effect of conventional semiconductor nanoparticles on light in a colloidal solution. It is assumed that the colloidal solution CS does not contain scattering materials. If illumination light Li is irradiated onto the colloidal solution CS, the illumination light Li transmits through the colloidal solution CS. This is because the particle size of the semiconductor nanoparticles is sufficiently small compared to the wavelength of the illumination light Li. Therefore, light degradation of the semiconductor nanoparticles occurs around the illumination light Li irradiating the colloidal solution CS, and the region Aa causing this light degradation is widely distributed in the colloidal solution CS.

[0042] <Methods for manufacturing colloidal solutions> The colloidal solution of this disclosure can be manufactured by slowly agglomerating a portion of the semiconductor nanoparticles in a dispersion of semiconductor nanoparticles. That is, the colloidal solution of this disclosure can be manufactured by suspending semiconductor nanoparticles, a dispersion medium, and a matrix component that is incompatible with the dispersion medium, thereby generating a composite particle containing semiconductor nanoparticles in a particle-like phase composed of the matrix component and incompatible with the dispersion medium, wherein the amount of the composite particle generated is less than 50% by mass of the total dispersed mass.

[0043] From the viewpoint of introducing desired ligands into semiconductor nanoparticles, this manufacturing method can further include the step of adding one or more components selected from zinc halides, mercaptosilanes, and xanthates to semiconductor nanoparticles or their dispersions to obtain a slurry. The dispersed phase in this slurry is used to suspend the semiconductor nanoparticles in a dispersion medium. By introducing these ligands into the semiconductor nanoparticles, the colloidal solution can be maintained in a stable state, making it possible to manufacture products using this colloidal solution with good yield.

[0044] The introduction of ligands can be either a replacement of the ligands described above or an addition. That is, if the semiconductor nanoparticles initially possess ligands, the initial ligands can be removed, and then the aforementioned ligands can be added. Alternatively, the aforementioned ligands can be added to the semiconductor nanoparticles while they initially possess ligands, thus introducing a portion of the aforementioned ligands into the semiconductor nanoparticles.

[0045] The manufacturing method may further include a step of filtering the generated colloidal solution. From the viewpoint of enabling the manufacture of products using the colloidal solution with a good yield, this further step is preferred.

[0046] (First method) Figure 3 This is a schematic diagram illustrating a first embodiment of composite particles in a colloidal solution according to the present disclosure. The colloidal solution 1 includes a dispersion medium 100 and composite particles 10 formed therein. The composite particles 10 include semiconductor nanoparticles 11 and a matrix component 12. Furthermore, in... Figure 3 In this context, semiconductor nanoparticles 11 that do not constitute the composite particles 10 in the dispersion medium 100 are omitted.

[0047] In this first embodiment, the dispersion medium 100 is a polar solvent, such as water, ethanol, or DMF. The semiconductor nanoparticles 11 are QDs having, for example, mercaptosilanes (e.g., (3-mercaptopropyl)triethoxysilane) as ligands. The matrix component 12 is, for example, an alkyl silicate (CxHyOzSiw, e.g., tetramethyl orthosilicate).

[0048] Semiconductor nanoparticles 11 and matrix component 12 are loosely adjacent to each other and function in an aggregate form, forming composite particles 10. Composite particles 10 become refractive index boundaries at the μm scale and produce light scattering, but are relatively soft. Therefore, they do not hinder film formation.

[0049] Thus, by forming large micelles (composite particles 10) in colloidal solution 1, the intensity of light scattering is increased, and the lightfastness of the colloidal solution is further improved. For example, colloidal solution 1 exhibits light scattering with a haze of approximately 20% in a solution with an optical path length of 1 cm. Furthermore, it achieves a median volume ratio of kinetic diameter that is above the wavelength of light absorbed by the semiconductor nanoparticles 11. Thus, colloidal solution 1 exhibits strong light scattering, and its lightfastness is further improved.

[0050] (Second method) Figure 4 This diagram schematically illustrates a second morphology of the composite particles in a colloidal solution according to the present disclosure. The colloidal solution 2 includes a dispersion medium 200 and composite particles 20 formed therein. The composite particles 20 include semiconductor nanoparticles 11 and matrix components 22A and 22B. Furthermore, in... Figure 4 In the text, the semiconductor nanoparticles 11 in the dispersion medium 200 are omitted.

[0051] In this second embodiment, the dispersion medium 200 is a nonpolar solvent, such as toluene. The semiconductor nanoparticles 11 are QD having, for example, a 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, a mercaptosilane or a product of its reaction with water. This mercaptosilane is the same as the ligand of the semiconductor nanoparticles 11.

[0052] Semiconductor nanoparticles 11 and matrix components 22A and 22B are loosely adjacent to each other and function in an aggregate form to form composite particles 20. Similar to the first method, composite particles 20 become refractive index boundaries at the μm scale, generating light scattering, but are more flexible. Therefore, they do not hinder film formation.

[0053] Similar to colloidal solution 1, colloidal solution 2 exhibits light scattering with a haze of approximately 20% in a solution with an optical path length of 1 cm. Furthermore, it achieves a median volume ratio of kinetic diameter that is above the wavelength of light absorbed by the semiconductor nanoparticles 11. Therefore, colloidal solution 2 also exhibits strong light scattering, further enhancing its lightfastness.

[0054] Furthermore, the composite particles 20 of the colloidal solution 2 contain water in the matrix composition. Therefore, it is easier to form large (soft) micelles, which is more advantageous from the viewpoint of increased light scattering intensity and improved light resistance.

[0055] <Display Device> The display device disclosed herein has a semiconductor functional layer composed of semiconductor nanoparticles formed by coating the colloidal solution. This semiconductor functional layer may contain the aforementioned matrix component, reactants of the matrix component in the colloidal solution, or residues thereof.

[0056] From the viewpoint of fully realizing the desired function of the semiconductor functional layer, the content of organic components in the semiconductor functional layer is preferably low. Organic components refer to ligands, free forms, or residues of organic components present in the semiconductor nanoparticles. From this viewpoint, the content of organic components in the semiconductor functional layer can be 10% by volume or less, 5% by volume or less, or 3% by volume or less. Furthermore, regarding the composition of the semiconductor functional layer, for example, 90% or more of the semiconductor functional layer is composed of reactants of semiconductor nanoparticles and matrix components, where the reactants of the matrix components can be silicon oxide or zinc sulfide. In such a semiconductor functional layer, further suppression of degradation of the semiconductor functional layer caused by current or light is preferable from the viewpoint of extending the lifespan of the display device.

[0057] The thickness of the semiconductor functional layer is thinner than the wavelength of visible light, for example, it can be less than 100 nm, or it can be less than 50 nm. In addition, from the viewpoint of the light emission characteristics of the display device, the arithmetic mean roughness Ra of the semiconductor functional layer is preferably less than the thickness of the semiconductor functional layer, more preferably less than half the thickness of the semiconductor functional layer, and even more preferably less than one-tenth of the thickness of the semiconductor functional layer.

[0058] The display device disclosed herein is a full-color display device having light-emitting elements that emit light in various colors, such as RGB, and at least one of the light-emitting elements of each color is made using the colloidal solution disclosed herein. The display device of this disclosure, except for including the light-emitting elements, can be configured in the same manner as known display devices that have light-emitting elements.

[0059] <Detailed Implementation> The display device of the present disclosure and the light-emitting element therein are further described below with reference to the accompanying drawings. Furthermore, in the following description, when reference numerals R, G, or B are used to indicate specific light-emitting colors, it signifies a specific light-emitting color configuration; when reference numerals are not used to indicate specific light-emitting colors, it signifies a general configuration unrelated to the light-emitting color.

[0060] Figure 5 This is a schematic diagram illustrating a display device according to one embodiment of the present disclosure. (As shown) Figure 5 As shown, the display device 50 includes a border area NDA and a display area DA. The display area DA of the display device 50 includes multiple pixels (PIX), each pixel comprising a red sub-pixel RSP, a green sub-pixel GSP, and a blue sub-pixel BSP. The red sub-pixel RSP includes a red light-emitting element, the green sub-pixel GSP includes a green light-emitting element, and the blue sub-pixel BSP includes a blue light-emitting element. In the stacking direction, the display device 50 has a configuration, for example, formed by sequentially stacking a substrate, a barrier layer, a thin-film transistor, a diaphragm, a light-emitting element, a sealing layer, and a functional film.

[0061] Figure 6 This is a schematic diagram illustrating the layer structure of the light-emitting element in this embodiment. (See diagram for example.) Figure 6 As shown, the light-emitting element 60 is disposed on a barrier layer 62 disposed on a substrate 61. The barrier layer 62 is formed, for example, of an insulator. A ridge 63 dividing the sub-pixels SP in the planar direction is formed on the barrier layer 62. The light-emitting element 60 is constructed by sequentially 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. Examples of light-emitting elements 60 include OLEDs and QLEDs.

[0062] The first electrode 64 is also referred to as the anode. The first electrode 64 is conductive, and has optical properties, such as reflecting a portion of visible light and transmitting the remainder. The first electrode 64 comprises both electrode materials that reflect visible light and electrode materials that transmit visible light.

[0063] Examples of electrode materials that reflect visible light include metallic materials such as Al, Mg, Li, and Ag, alloys of such metallic materials, and laminates of such metallic materials or their alloys with transparent metal oxides (such as indium tin oxide (ITO), indium zinc oxide, or indium gallium zinc oxide, etc.) (e.g., ITO / Ag / ITO). Examples of electrode materials that transmit visible light include thin films composed of transparent metal oxides, metallic materials such as Al and Ag, and nanowires composed of such metallic materials.

[0064] The first electrode 64 can be fabricated using known methods for fabricating electrode layers in a light-emitting element. For example, the first electrode 64 can be fabricated using physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of physical vapor deposition methods include vacuum evaporation, sputtering, electron beam (EB) evaporation, and ion plating. Additionally, examples of methods for patterning the first electrode 64 include photolithography and inkjet printing.

[0065] The hole injection layer 65 is composed of a hole-injecting material capable of stabilizing the injection of holes into the light-emitting layer 67. The hole-injecting material may be one or more. Examples of hole-injecting materials include the nickel oxide nanoparticles disclosed herein, and also contain poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), Ni(OH)₂, and CuSCN.

[0066] Hole transport layer 66 is composed of a hole transport material capable of stabilizing the transport of holes into the light-emitting layer 67. The hole transport material may be one or more. Examples of hole transport materials include the nickel oxide nanoparticles disclosed herein, 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).

[0067] In this disclosure, the encapsulated nickel oxide nanoparticles may be contained in only one of the hole injection layer 65 and the hole transport layer 66, or they may be contained in both.

[0068] The hole injection layer 65 or hole transport layer 66 containing the nickel oxide nanoparticles of this disclosure can be fabricated by coating with an ink containing nickel oxide nanoparticles. The hole injection layer 65 or hole transport layer 66 can be fabricated by known methods of fabricating layers of a light-emitting element through ink coating, in addition to using an ink containing nickel oxide nanoparticles. For example, the hole injection layer 65 or hole transport layer 66 can be fabricated using a slot coater or inkjet printing.

[0069] The encapsulated nickel oxide nanoparticles of this disclosure are tiny and uniform nanoparticles, encapsulated by a host. Therefore, they are uniformly dispersed in the ink solvent. The ink solvent is selected to have appropriate wetting properties for the coating area. By coating the ink containing the uniformly dispersed encapsulated nickel oxide nanoparticles, the encapsulated nickel oxide nanoparticles are uniformly coated onto the coating area, forming a flat layer. Therefore, in this disclosure, a flat hole injection layer 65 or hole transport layer 66 formed by the encapsulated nickel oxide nanoparticles can be formed.

[0070] The light-emitting layer 67 can be composed of quantum dots (QDs). A QD is a dot with a maximum width of less than 100 nm. The shape of a QD can be a spherical three-dimensional shape (a circular cross-sectional shape), or, for example, a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a dendritic three-dimensional shape, a three-dimensional shape with uneven surfaces, or a combination thereof.

[0071] The structure of a QD can be, for example, a nuclear structure, a core / shell structure, a core / shell / shell structure, or a shell structure in which the core-shell ratio changes continuously. A QD can have ligands; when the QD has a nuclear structure, ligands can be present on the surface of the nuclear structure, and when the QD has a shell structure, ligands can be present on the surface of the shell structure.

[0072] The materials constituting the core structure of a QD (Quadrature Diode) include Si and C if it is a unary system. In a binary system, the materials include CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, and ZnTe. In a ternary system, the materials include CdSeTe, GaInP, and ZnSeTe. If the material is a quaternary system, it includes AIGS.

[0073] If the material constituting the shell structure of QD is a binary system, it includes CdS, CdTe, CdSe, ZnS, ZnSe, and ZnTe. If the material is a ternary system, it includes CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AIP.

[0074] The electron transport layer 68 is composed of an electron transport material capable of stabilizing the transport of electrons into the light-emitting layer 67. Examples of electron transport materials include 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.

[0075] The second electrode 69 is also called a cathode. The second electrode 69 is conductive, for example, it is conductive and transmissive to visible light. Examples of electrode materials constituting the second electrode 69 include the aforementioned visible light-transmitting electrode materials, such as ITO and Ag nanowires (NW). The second electrode 69 can be fabricated from the first electrode 64 using a method corresponding to the electrode material described above. From the viewpoint of simplifying the manufacturing process, the second electrode 69 is integrally formed on both the electron transport layer 68 and the dam 63. The second electrode 69 may be formed on the electron transport layer 68, or it may not be formed on the dam 63.

[0076] 〔Summarize〕 When fabricating a semiconductor functional layer using the colloidal solution of this disclosure, the composite particles constitute a phase incompatible with the dispersion medium, i.e., a particle-like aggregate formed through gentle aggregation. Therefore, by applying a force for film formation in the colloidal solution, the composite particles disintegrate, and the semiconductor nanoparticles and matrix components within 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 this disclosure, which achieves this film-forming mechanism, is advantageous for forming nanometer-scale thin films for electroluminescence (EL) applications.

[0077] Furthermore, compared to existing colloidal solutions containing scattering materials, the colloidal solution disclosed herein does not require filtration to remove light-scattering particles. Moreover, since the composite particles are a soft, particle-like aggregate, even if the colloidal solution is filtered to remove particles the size of the composite particles, the composite particles can still pass through the filter.

[0078] Furthermore, in the colloidal solution disclosed herein, the matrix component can utilize ligands for semiconductor nanoparticles. Therefore, the functionality of the semiconductor nanoparticles in the semiconductor functional layer can be further enhanced.

[0079] According to this disclosure, a colloidal solution of semiconductor nanoparticles with good lightfastness and coating properties can be achieved, thereby improving the yield of articles having a semiconductor functional layer formed from the semiconductor nanoparticles. This disclosure, with its advantages, is expected to contribute to achieving, for example, Goal 12, “Responsible Consumption and Production,” of the United Nations Sustainable Development Goals (SDGs).

[0080] This disclosure is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included within the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0081] Industrial availability The colloidal solution disclosed herein is useful as a coating for manufacturing semiconductor functional layers substantially composed of semiconductor nanoparticles. The colloidal solution disclosed herein is also useful as a technique for improving the light scattering properties of colloidal solutions without adding light scattering materials.

[0082] Explanation of reference numerals in the attached figures 1, 2, CS: colloidal solution; 10, 20: Composite particles; 11: Semiconductor nanoparticles; 12, 22A, 22B: Matrix components; 100, 200: Dispersion medium; 50: Display device; 61: Substrate; 62: Barrier layer; 63: embankment; 64: First electrode; 65: Hole injection layer; 66: Hole transport layer; 67: Emissive layer; 68: Electron transport layer; 69: Second electrode; DA: Display area; NDA: Border Area; PIX: pixel; Aa: The region where light degradation occurs; Li: Irradiation light; Ls: Scattered light.

Claims

1. A colloidal solution comprising: Dispersion medium; and A composite particle, comprising semiconductor nanoparticles and composite particles containing semiconductor nanoparticles, wherein the semiconductor nanoparticles and the composite particles are dispersed as a dispersing phase in a dispersion medium, characterized in that... The composite particles have a matrix component that constitutes a particle-like phase incompatible with the dispersion medium. The content of the composite particles is less than 50% by mass of the total dispersed mass.

2. The colloidal solution according to claim 1, characterized in that, The composite particles have light scattering properties for the wavelengths of light absorbed by the semiconductor nanoparticles.

3. The colloidal solution according to claim 2, characterized in that, The wavelength of the light is above 300 nm.

4. The colloidal solution according to claim 2 or 3, characterized in that, The median of the volumetric reference for the kinetic diameter of the colloidal solution is above the wavelength of the light.

5. The colloidal solution according to claim 1, characterized in that, When a film with an average thickness of 50 nm is prepared by spin-coating the colloidal solution, the arithmetic mean roughness Ra of the film is less than 50 nm.

6. The colloidal solution according to claim 1, characterized in that, The semiconductor nanoparticles are core-shell particles with a shell, the shell being composed of zinc halides containing more than 10 mol% zinc. It further contains zinc halides.

7. The colloidal solution according to claim 1, characterized in that, It further contains xanthic acid compounds.

8. The colloidal solution according to claim 7, characterized in that, The content of the xanthate as a mass standard is more than half the content of the semiconductor nanoparticles.

9. The colloidal solution according to claim 7 or 8, characterized in that, The content of xanthic acid is above 1% by mass.

10. The colloidal solution according to any one of claims 1 to 9, characterized in that, The dispersion medium is a polar solvent. The matrix component contains alkoxysilane.

11. The colloidal solution according to claim 10, characterized in that, The mass basis content of the alkoxysilane is more than half the mass basis content of the semiconductor nanoparticles.

12. The colloidal solution according to claim 10 or 11, characterized in that, The content of the alkoxysilane is 1% by mass or more.

13. The colloidal solution according to any one of claims 1 to 9, characterized in that, The dispersion medium is a nonpolar solvent. The matrix component contains less than 10% by mass of a polar solvent relative to the dispersion medium.

14. The colloidal solution according to claim 13, characterized in that, The matrix components also include mercaptosilane.

15. The colloidal solution according to claim 14, characterized in that, The content of the mercaptosilane as a mass standard is more than half the content of the semiconductor nanoparticles.

16. The colloidal solution according to claim 14 or 15, characterized in that, The content of the mercaptosilane is 1% by mass or more.

17. A method for manufacturing a colloidal solution, characterized in that, Semiconductor nanoparticles, a dispersion medium, and a matrix component incompatible with the dispersion medium are suspended to generate a composite particle containing semiconductor nanoparticles in a particle-like phase composed of the matrix component and incompatible with the dispersion medium. The amount of the composite particle generated is less than 50% by mass of the total dispersed mass.

18. The method for manufacturing a colloidal solution according to claim 17, characterized in that, It also includes the step of adding one or more components selected from the group consisting of zinc halides, mercaptosilanes, and xanthates to semiconductor nanoparticles or their dispersions to obtain a slurry. The dispersed phase in the slurry is used to suspend semiconductor nanoparticles in the dispersion medium.

19. The method for manufacturing a colloidal solution according to claim 17 or 18, characterized in that, The process further includes the step of filtering the resulting colloidal solution.

20. A display device, characterized in that, It has a semiconductor functional layer composed of said semiconductor nanoparticles, formed by coating a colloidal solution according to any one of claims 1 to 16.

21. The display device according to claim 20, characterized in that, The content of organic components in the semiconductor functional layer is less than 10% by volume.

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