Dispersion, surface-modified nickel oxide nanoparticles, thin film

Abstract

The objective is to provide a dispersion containing nickel oxide nanoparticles with excellent dispersibility and a surface modifier, surface-modified nickel oxide nanoparticles, and a thin film containing the surface-modified nickel oxide nanoparticles. [Solution] The dispersion of the present disclosure is a dispersion comprising nickel oxide nanoparticles, a surface modifier, and an organic solvent, wherein the surface modifier is a nitrogen-containing compound comprising at least one of an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. The thin film of the present disclosure is characterized by comprising surface-modified nickel oxide nanoparticles.

Description

Technical Field

[0001] The present disclosure relates to a dispersion liquid containing nickel nanoparticles and a surface modifier, surface-modified nickel oxide nanoparticles, and a thin film containing the surface-modified nickel oxide nanoparticles.

Background Art

[0002] Patent Document 1 discloses an invention relating to a NiO film containing NiO particles and a dispersion liquid. Patent Document 1 defines the cumulative 50% particle diameter in the volume particle size distribution of NiO particles. Patent Document 1 takes as the effect of the invention that a NiO dispersion liquid with high particle dispersibility is provided.

[0003] Patent Document 1 states that including a polyhydric alcohol in the dispersion liquid improves dispersibility. It also states that adding a silane coupling agent or the like is also suitable.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, thin films containing NiO particles are used, for example, as hole injection layers and hole transport layers of light-emitting elements and photoelectric conversion elements. It is expected to enhance the dispersion stability of the dispersion liquid containing NiO particles and improve the electrical conductivity of the thin film containing NiO particles.

[0006] The present disclosure has been made in view of the above problems, and aims to provide a dispersion liquid containing nickel oxide nanoparticles with excellent dispersion stability and a surface modifier, surface-modified nickel oxide nanoparticles, and a thin film containing the surface-modified nickel oxide nanoparticles.

Means for Solving the Problems

[0007] The dispersion of the present disclosure is a dispersion comprising nickel oxide nanoparticles, a surface modifier, and an organic solvent, wherein the surface modifier is a nitrogen-containing compound comprising at least one of an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle.

[0008] The surface-modified nickel oxide nanoparticles of the present disclosure comprise nickel oxide nanoparticles and a nitrogen-containing compound surface-modified on the nickel oxide nanoparticles, wherein the nitrogen-containing compound comprises at least one of an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a dispersion containing nickel oxide nanoparticles and a surface modifier that exhibits excellent dispersion stability. Excellent conductivity can be obtained by forming a thin film containing surface-modified nickel oxide nanoparticles using a dispersion with excellent dispersion stability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional view of the conductive film of this embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of this disclosure (hereinafter abbreviated as "Embodiment") will be described in detail. However, this disclosure is not limited to the following embodiment, and can be implemented in various modifications within the scope of its gist.

[0012] <Background leading to this embodiment> For example, in self-luminous light-emitting devices, a hole injection layer is provided between the anode and the light-emitting layer to promote the injection of holes from the anode to the light-emitting layer. Furthermore, in perovskite solar cells, the use of a thin film containing nickel oxide nanoparticles as a hole transport layer is being considered. When using nickel oxide nanoparticles as hole injection or hole transport layers in light-emitting devices or perovskite solar cells, there is a need for a form that is highly conductive, has excellent long-term stability, and can be easily formed into a thin film.

[0013] For example, a method is known in which a thin film is obtained by applying a dispersion of nickel oxide nanoparticles and an organic solvent using a spin coater to form a coating film. In this case, a method is known in which a mixture of a silane coupling agent and nickel oxide nanoparticles or a precursor of nickel oxide nanoparticles is mechanically dispersed using a paint shaker or ball mill. However, in the method of mechanically dispersing using a silane coupling agent, as described in Patent Document 1, the nickel oxide nanoparticles are prone to distortion, and furthermore, the conductivity may decrease due to the influence of impurities from the ceramic material used for grinding.

[0014] Therefore, as a result of diligent research by the inventors, we have developed a dispersion containing nickel oxide nanoparticles and a surface modifier that exhibits excellent dispersion stability.

[0015] <Regarding the characteristic configuration of this embodiment> In this embodiment, the dispersion comprises nickel oxide nanoparticles, a surface modifier, and an organic solvent, wherein the surface modifier is a nitrogen-containing compound comprising at least one of the following: an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle.

[0016] "Nickel oxide nanoparticles" refer to those whose main component is nickel oxide, and do not exclude the presence of subcomponents or inevitable components other than nickel oxide. The composition analysis can be performed by X-ray diffraction (XRD). In addition, a large number of single particles (individual particles) of the nickel oxide nanoparticles are present in the dispersion. In the present embodiment for improving dispersion stability, it is preferred that a large number of substantially single particles are in a dispersed state, and without limitation, 90% or more, preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more of the particles exist as single particles. The nickel oxide component contained in the nickel oxide nanoparticles accounts for 90% or more, preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more of the entire nanoparticles.

[0017] Nickel oxide is NiO x can be represented by. In the stoichiometric composition of nickel oxide, x is 1, but in order to exhibit a hole transport function, x is desirably less than 1, and as a result, the Ni valence needs to be a value between divalent and trivalent. In the examples, the Ni valence is greater than 2 and less than 2.5, preferably 2.1 to 2.4. Thereby, the NiO of the present embodiment x can be proven to be a hole carrier.

[0018] "Nanoparticles" mean particles having a particle size on the nanometer order. Thereby, the denseness of a thin film formed using a dispersion containing nickel oxide nanoparticles can be improved.

[0019] For dispersions containing nickel oxide nanoparticles, the particle size distribution measured by a dynamic light scattering method can be defined. The "dynamic light scattering method" is a method of irradiating a solution in which particles are dispersed with laser light, and deriving the particle size (particle diameter) based on the fluctuation of scattered light intensity dependent on the Brownian motion of the particles detected when the change in the scattered light is measured.

[0020] The dispersion of the present embodiment contains a surface modifier and an organic solvent in addition to the nickel oxide nanoparticles. Hereinafter, the surface modifier will be described in detail.

[0021] <Surface Modifying Agent> The surface modifying agent comprises a nitrogen-containing compound containing at least one of an amino group, an ammonium group, or a heterocyclic compound having a nitrogen atom in its heterocycle. According to experiments described later, it has been found that excellent dispersion stability can be obtained by containing these functional groups and compounds. It is presumed that the dispersion stability can be enhanced because the adsorption property to the surface of nickel oxide is improved by having the compound, whereby the physical approach between particles can be hindered, or factors such as increased charge repulsion between particles are intertwined in a complex manner, aggregation hardly occurs, particle growth can be suppressed, and the particle diameter can be reduced.

[0022] In the present embodiment, the nitrogen-containing compound has at least one of the following general formulas (1), (2) and (3).

[0023] [Chemical Formula] (provided that X1 and X2 are each independently selected from at least one of hydrogen, an alkyl group, an aryl group and a cycloalkyl group, and R1 is selected from at least one of an aliphatic hydrocarbon, an aromatic hydrocarbon, a hydroxyl group and a carboxyl group)

[0024] [Chemical Formula] (provided that Y1, Y2 and Y3 are each independently selected from at least one of hydrogen, an alkyl group, an aryl group and a cycloalkyl group, Z is selected from halogens, and R2 is selected from at least one of an aliphatic hydrocarbon, an aromatic hydrocarbon, a hydroxyl group and a carboxyl group)

[0025] [Chemical Formula] (provided that R3 to R7 are each independently selected from at least one of hydrogen, an aliphatic hydrocarbon and an aromatic hydrocarbon)

[0026] For example, hydrogen can be selected for X1 and X2 in general formula (1). For example, R1 in general formula (1) can be a structure containing an aliphatic hydrocarbon and a hydroxyl group. In this case, the aliphatic hydrocarbon is attached to the amino group side and the hydroxyl group is attached to the terminal side.

[0027] In general formula (2), Y3, Y4, and Y5 can be, for example, hydrogen. Z can be selected from halogens, and is not limited to them, but for example, chlorine can be selected. Y can have a structure that includes aliphatic hydrocarbons and aromatic hydrocarbons. For example, hydrogen can be selected for R3 to R7 in general formula (3).

[0028] More specifically, the nitrogen-containing compound is selected from at least one of ethanolamine, pyridine, and phenylethylamine hydrochloride. A surface modifier containing two or more of these nitrogen compounds can be used.

[0029] By using these nitrogen-containing compounds as surface modifiers, the surface modifiers bind to the surface of nickel oxide nanoparticles. This suppresses aggregation of nickel oxide nanoparticles, inhibits particle growth, and reduces particle size. Therefore, it is possible to suppress particle sedimentation and turbidity in the dispersion, minimize changes in dispersibility over time, and obtain excellent dispersion stability over a long period of time.

[0030] In the dispersion of this embodiment, the surface modifier is included in an amount of 0.1 to 1 part by mass of nickel oxide nanoparticles. Preferably, it is 0.1 to 0.9, and more preferably 0.1 to 0.8. This makes it possible to more effectively enhance dispersion stability.

[0031] In the dispersion of this embodiment, the organic solvent preferably contains at least one of alcohols, solvents having an amide group, or solvents having a sulfoxide group. Examples of alcohols, though not limited to them, include methanol, ethanol, and isopropyl alcohol. Examples of solvents having an amide group include dimethylacetamide, dimethylformamide (DMF), N-methylpyrrolidone, and N-cyclohexylpyrrolidone. Examples of solvents having a sulfoxide group include dimethyl sulfoxide (DMSO) and diethyl sulfoxide. By using these organic solvents, the affinity between the surface modifier and the organic solvent is increased, thereby improving dispersion stability.

[0032] In the dispersion of this embodiment, the cumulative 50% particle size (D50) in the cumulative particle size distribution measured by dynamic light scattering is 30 nm or less. Dynamic light scattering is a method of determining particle size (dispersed particle diameter) based on fluctuations in scattered light intensity that depend on the Brownian motion of the particles, detected when laser light is irradiated onto a solution in which particles are dispersed and the change in scattered light is measured. D50 is preferably between 1 nm and 29 nm, and more preferably between 3 nm and 27 nm. By keeping D50 within the above range, aggregation of nickel oxide nanoparticles is suppressed, and the dispersed particle diameter of nickel oxide nanoparticles can be reduced. This suppresses particle sedimentation and turbidity in the dispersion, reduces changes in dispersibility over time, and allows for excellent dispersion stability over a long period of time.

[0033] <Regarding the embodiment containing nickel oxide nanoparticles of this embodiment> In this embodiment, a conductive film can be provided using a dispersion containing nickel oxide nanoparticles and a surface modifier.

[0034] Figure 1 is a partial cross-sectional view showing an example of the conductive film 10 of this embodiment. The conductive film 10 shown in Figure 1 comprises a substrate 1 and a thin film 2 formed on the surface of the substrate 1.

[0035] For example, the base material 1 is a glass substrate, but it may be replaced with a plastic substrate or a film.

[0036] In this embodiment, the thin film 2 is composed of a metal oxide containing surface-modified nickel oxide particles. The nickel vacancies in the metal oxide are preferably greater than those in the bulk material. That is, a stoichiometric composition or close to it is preferable. "Bulk material" refers to a lump containing the metal oxide, regardless of size or shape.

[0037] In this embodiment, a thin film 2 can be formed by depositing the dispersion onto a substrate 1 and performing a predetermined drying treatment. The thin film 2 contains surface-modified nickel oxide nanoparticles. In this specification, surface-modified nickel oxide nanoparticles will be referred to as "surface-modified nickel oxide nanoparticles".

[0038] Surface-modified nickel oxide nanoparticles are nickel oxide nanoparticles surface-modified with a nitrogen-containing compound, the nitrogen-containing compound having a structure containing at least one of an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. Preferably, the nitrogen-containing compound contains one or more of the general formulas (1), (2), and (3) listed above. More specifically, the nitrogen-containing compound is selected from at least one of ethanolamine, pyridine, and phenylethylamine hydrochloride. Two or more of these nitrogen compounds may be surface-modified on the nickel oxide nanoparticles.

[0039] The nitrogen-containing compound surface-modified on the nickel oxide nanoparticles may be a compound derived from general formulas (1), (2), or (3), or a derivative thereof.

[0040] The surface roughness Sa of thin film 2 is not limited, but can be adjusted to 40 nm or less, or 30 nm or less. Surface roughness Sa is a three-dimensional surface roughness and is expressed as the average value of the surface roughness in the measurement area. Surface roughness Sa is more preferably 20 nm or less, and even more preferably 10 nm or less. Also, since the smaller the surface roughness Sa, the better, there is no lower limit, but it may be, for example, 1 nm or more. Surface roughness Sa can be measured, for example, by an atomic force microscope (AFM) (e.g., Park NX10).

[0041] In this embodiment, the thin film 2 preferably has an average transmittance of 85% or more in the wavelength band from 400 nm to 1600 nm. The average transmittance is greater than 85%, more preferably 90% or more, and even more preferably 95% or more. "Average transmittance" is the value obtained by averaging multiple transmittances measured at an arbitrary wavelength pitch.

[0042] The conductive film 10 of this embodiment has an electrical resistivity of 1.0 × 10⁻⁶. 6 It is less than or equal to Ω·cm, or 1.0 × 10⁻⁶. 5 It is less than or equal to Ω·cm. The electrical resistivity is the volume resistivity. The film thickness of the thin film is not limited, but it is preferably 100 nm or less. This film thickness matches the film thickness of the hole transport layer and hole injection layer of perovskite solar cells, etc., and can be considered as the electrical resistivity of the hole transport layer and hole injection layer. The lower limit of thin film 2 is not limited, but it is preferably 10 nm or more, and may be 30 nm or more, or 50 nm or more.

[0043] The electrical resistivity is 1.0 × 10⁻⁶. 5 Preferably, it should be Ω·cm or less, and 5.0 × 10 4 It is more preferable that the value be less than or equal to Ω·cm. Thus, by including the surface-modified nickel oxide nanoparticles of this embodiment, it is possible to form a thin film with low electrical resistivity and high transmittance.

[0044] Thus, the thin film containing surface-modified nickel oxide nanoparticles of this embodiment has excellent conductivity.

[0045] <Method for producing nickel oxide particles according to this embodiment> The following describes a method for manufacturing nickel oxide particles, but this is just one example and is not limited to the method described below.

[0046] Prepare a nickel compound and then mix and stir it with deionized water to create an aqueous solution. While not limited to specific nickel compounds, examples include nickel sulfate, nickel carbonate, and nickel nitrate.

[0047] An alkaline aqueous solution is added to an aqueous nickel solution to obtain a nickel hydroxide precipitate. The alkaline raw material used is not particularly limited, but examples include sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide. The nickel hydroxide precipitate is washed with deionized water and then separated by centrifugation. The solid obtained by centrifugation is further washed with alcohol and separated by centrifugation.

[0048] Next, the separated solid material is dried in a vacuum dryer for 24 hours to remove moisture. The thoroughly dried nickel hydroxide is heated in an oven, for example, at 270°C for 3 hours to obtain black NiOx powder.

[0049] <Method for producing the dispersion of this embodiment> The following describes a method for producing a dispersion, but this is just one example and is not limited to the method described below.

[0050] The NiOx particles produced as described above are mixed with deionized water, and an aqueous dispersion of NiOx is obtained by ultrasonic waves or the like. A surface modifier is added to the obtained aqueous dispersion, and the aqueous dispersion and the surface modifier are thoroughly reacted by ultrasonic waves or the like. The surface modifier consists of a nitrogen-containing compound that contains at least one of the following: an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. Specifically, it is preferable that the surface modifier contains a nitrogen-containing compound having at least one of the general formulas (1), (2), and (3) listed above.

[0051] An aqueous solution containing a surface modifier is separated into water and solid matter using a centrifuge, and the water is removed. An organic solvent is added to the obtained solid matter, and it is dispersed again using ultrasound to obtain a dispersion.

[0052] In this embodiment, by adding a specific surface modifier, the particle size can be reduced, and a dispersion with excellent dispersion stability can be obtained.

[0053] <Applications of the thin film in this embodiment> While this embodiment does not limit the applications of the thin film, the thin film containing surface-modified nickel oxide nanoparticles in this embodiment has excellent conductivity and can therefore be preferably applied to hole transport layers in photoelectric conversion elements and hole injection layers and hole transport layers in optical elements. In particular, it is believed that using it as a hole transport layer in a perovskite solar cell allows for energy level matching with the perovskite semiconductor and reduces the electrical resistance of the hole transport layer 45, thereby obtaining excellent power generation characteristics. [Examples]

[0054] The effects of this disclosure will be explained below with reference to the examples and comparative examples provided. However, this disclosure is not limited in any way to the following examples. In the experiment, a dispersion containing nickel oxide nanoparticles, a surface dispersant, and an organic solvent was prepared.

[0055] <Example 1> Nickel nitrate aqueous solution was dissolved in a solvent, and sodium hydroxide aqueous solution was added to the aqueous solution to obtain nickel hydroxide. Then, the solution was heated at approximately 270°C for 3 hours to obtain nickel oxide nanoparticles. 1.0 g of the obtained nickel oxide nanoparticles was added to 19 g of deionized water at 25°C, and sonication was performed at 40 kHz for 10 minutes to obtain an aqueous dispersion. 0.1 g of ethanolamine (surface modifier) ​​was added to the obtained aqueous dispersion, and the reaction was carried out while sonication was performed at 40 kHz for 5 minutes. The reaction mixture was centrifuged at 4000 rpm for 5 minutes to separate the water and reactants. The supernatant was removed, 99 g of ethylene glycol (organic solvent) was added to adjust the concentration to 1%, and the mixture was redispersed by sonication at 40 kHz for 30 minutes to prepare a dispersion. <Example 2> In Example 1, pyridine was used as a surface modifier instead of ethanolamine. All other conditions were the same as in Example 1. <Example 3> In Example 1, phenylethylamine hydrochloride (PEACL; 10% solution in methanol) was used as a surface modifier instead of ethanolamine. All other conditions were the same as in Example 1, except that the amount of surface modifier added was 0.5 g. <Example 4> In Example 2, dimethylformamide (DMF) was used as the organic solvent instead of the alcohol. All other conditions were the same as in Example 2. <Example 5> In Example 2, dimethyl sulfoxide (DMSO) was used as the organic solvent instead of the alcohol. All other conditions were the same as in Example 2. <Example 6> Pyridine was mixed with the ethanolamine from Example 1. The conditions were the same as in Example 1, except that the total amount added was 0.2 g. <Example 7> PEACL was mixed with the ethanolamine from Example 1. The conditions were the same as in Example 1, except that the total amount added was 0.2 g. <Example 8> In Example 1, ethanolamine was replaced with a mixture of PEACL and pyridine. The procedure was the same as in Example 1, except that the total amount added was 0.6 g. <Example 9> In Example 1, diethyl ether was used as the organic solvent instead of the alcohol. All other conditions were the same as in Example 1.

[0056] <Comparative Example 1> Nickel nitrate aqueous solution was dissolved in a solvent, and sodium hydroxide aqueous solution was added to the solution to obtain nickel hydroxide. Then, the solution was heated at approximately 270°C for 3 hours to obtain nickel oxide nanoparticles. Alcohol was added to the obtained nickel oxide nanoparticles, and a dispersion was prepared by ultrasonic dispersion. In Comparative Example 1, unlike in the Examples, no surface modifier was added. <Comparative Example 2> Dodecanethiol was added as a surface modifier to Comparative Example 1. <Comparative Example 3> Zirconia beads were added to the dispersion of Comparative Example 1 and subjected to a crushing treatment using a paint shaker. The crushed dispersion was filtered to remove the zirconia beads and obtain a new dispersion.

[0057] <Method for measuring particle size distribution> The particle size distribution of nickel oxide nanoparticles in a dispersion was measured using a particle size distribution analyzer. The measurement principle is dynamic light scattering. <Visual observation> Dispersion stability was evaluated by visual observation. Samples that showed no precipitation or turbidity even after several days were marked with ◎. Samples that showed no precipitation or turbidity even after more than 24 hours, although their dispersion stability was inferior to that of ◎ samples, were marked with ○. Samples that showed precipitation or turbidity after 24 hours were marked with △. Samples that showed precipitation or turbidity immediately after the visual inspection were marked with ×. The experimental results are shown in Table 1.

[0058] [Table 1]

[0059] As shown in Table 1, the dispersion stability was excellent (◎) or good (○) in all of Examples 1 to 9. In Examples 1 to 9, the cumulative 50% particle size in the cumulative particle size distribution measured by dynamic light scattering was found to be 30 nm or less. Thus, the particle size was reduced.

[0060] Furthermore, in Examples 1 to 9, it was found that excellent dispersion stability could be obtained when the surface modifier consisted of a nitrogen-containing compound containing at least one of the following: an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. The nitrogen-containing compounds used in the experiments were selected from one or more of ethanolamine, pyridine, and phenylethylammonium salt. It is presumed that by including an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle as a surface modifier, the proximity of particles can be physically prevented, or dispersion stability can be enhanced through charge repulsion between particles, etc.

[0061] Furthermore, as shown in Examples 1 to 8, it was found that including at least one of alcohols, solvents having amide groups, or solvents having sulfoxide groups as the organic solvent can further enhance the aggregation suppression effect and obtain superior dispersion stability.

[0062] Next, a nickel oxide dispersion was deposited onto an ITO substrate by spin coating to a thickness of approximately 50 nm to 100 nm, and then dried on a hot plate at 100°C for 10 minutes. This yielded a thin film.

[0063] <Example 10> This is an experimental example using the dispersion from Example 1. <Example 11> This is an experimental example using the dispersion from Example 2. <Example 12> This is an experimental example using the dispersion from Example 3. <Example 13> This is an experimental example using the dispersion from Example 4. <Example 14> This is an experimental example using the dispersion from Example 5. <Example 15> This is an experimental example using the dispersion from Example 6. <Example 16> This is an experimental example using the dispersion from Example 7. <Example 17> This is an experimental example using the dispersion from Example 8. <Example 18> This is an experimental example using the dispersion from Example 9.

[0064] <Comparative Example 4> This is an experimental example using the dispersion from Comparative Example 1. <Comparative Example 5> This is an experimental example using the dispersion from Comparative Example 2. <Comparative Example 6> This is an experimental example using the dispersion from Comparative Example 3.

[0065] <Method for measuring surface roughness Sa> The surface roughness Sa of the thin film was measured using an atomic force microscope (AFM) (Park NX10). <Method for measuring transmittance> Using a UH4150 ultraviolet-visible-infrared spectrophotometer (manufactured by Hitachi High-Tech Corporation), the transmittance (wavelength 400-1600 nm) of a thin film coated on a glass substrate was measured with the glass substrate as the baseline, and the average transmittance (wavelength 400-1600 nm) of the thin film was obtained. <Method for measuring electrical resistivity> The electrical resistivity (volume resistivity) of the conductive film was measured using a high-resistivity resistivity meter, the Hi-Lester UX (manufactured by Nitto Seiko Co., Ltd.). The experimental results are shown in Table 2 below.

[0066] [Table 2]

[0067] As shown in Table 2, Examples 10-18 had a surface roughness Sa of 40 nm or less, preferably 30 nm or less, and an average transmittance of 85% or more in the wavelength range of 400 nm to 1600 nm. Furthermore, the electrical resistivity of Examples 10-18 was lower than that of Comparative Examples 4-6. The electrical resistivity in the examples was 1.0 × 10⁻⁶. 6 The conductivity was less than or equal to Ω·cm. Thus, it was found that Examples 10 to 18 have excellent conductivity and can be preferably applied as hole transport layers or hole injection layers in optical elements and photoelectric conversion elements. [Explanation of Symbols]

[0068] 45: Hole transport layer 46: Glass substrate

Claims

1. A dispersion comprising nickel oxide nanoparticles, a surface modifier, and an organic solvent, The surface modifier has a nitrogen-containing compound that includes at least one of the following: an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. A dispersion characterized by the following features.

2. The invention comprises nickel oxide nanoparticles and a nitrogen-containing compound surface-modified on the nickel oxide nanoparticles. The nitrogen-containing compound comprises at least one of the following: an amino group, an ammonium group, or a heterocyclic compound containing a nitrogen atom in the heterocycle. Surface-modified nickel oxide nanoparticles characterized by the following features.

3. The nitrogen-containing compound has at least one of the following general formulas (1), (2), and (3): A dispersion or surface-modified nickel oxide nanoparticles according to claim 1 or 2. 【Chemistry 1】 (However, X １ and X ２ Each of these is selected from hydrogen, alkyl groups, aryl groups, and cycloalkyl groups, and R １ (At least one of aliphatic hydrocarbons, aromatic hydrocarbons, hydroxyl groups, and carboxyl groups is selected.) 【Chemistry 2】 (However, Y １ , Y ２ and Y ３ Each of the following is selected: hydrogen, alkyl group, aryl group and cycloalkyl group, Z is selected from halogens, and R ２ (At least one of aliphatic hydrocarbons, aromatic hydrocarbons, hydroxyl groups, and carboxyl groups is selected.) 【Transformation 3】 (provided that, R ３ to R ７ are each independently selected from at least one of hydrogen, aliphatic hydrocarbons, and aromatic hydrocarbons)

4. The nitrogen-containing compound is selected from at least one of ethanolamine, pyridine, and phenylethylamine hydrochloride. A dispersion or surface-modified nickel oxide nanoparticles according to claim 1 or 2.

5. The surface modifier is included in an amount of 0.1 to 1 with respect to 1 part by mass of the nickel oxide nanoparticles. The dispersion according to feature 1.

6. The organic solvent comprises at least one of alcohols, solvents having an amide group, and solvents having a sulfoxide group. The dispersion according to feature 1.

7. The cumulative 50% particle size in the cumulative particle size distribution measured by dynamic light scattering is 30 nm or less. The dispersion according to feature 1.

8. A thin film comprising surface-modified nickel oxide nanoparticles as described in claim 2.

9. The surface roughness Sa is 40 nm or less. The thin film according to feature 8.

10. The average transmittance in the wavelength range of 400 nm to 1600 nm is 85% or higher. The thin film according to feature 8.

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