Indium tin oxide particles, indium tin oxide particle dispersion, method for producing indium tin oxide particle dispersion, and method for producing indium tin oxide particle laminated film

Abstract

To provide indium tin oxide particles that enable uniform coating of the indium tin oxide particles and allow stable formation of a thinned indium tin oxide particle laminated film.SOLUTION: The ratio Dv / Dn of the mode Dv (nm) of a volume particle diameter to the mode Dn (nm) of a number particle diameter, obtained by measuring a hydrodynamic particle diameter by a dynamic light scattering method in a state of being dispersed at a concentration of 0.5 mass% in a dispersion medium, is within a range of 1.00 or more and 1.20 or less. It is preferable that the mode Dv (nm) of the volume particle diameter is within a range of 4 nm or more and 30 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to indium tin oxide particles, an indium tin oxide particle dispersion, a method for producing an indium tin oxide particle dispersion, and a method for producing an indium tin oxide particle laminate film using the indium tin oxide particle dispersion, which can be used, for example, when forming a conductive film or the like. [Background technology]

[0002] Indium tin oxide has relatively good electrical conductivity, and therefore, as shown in Patent Documents 1 and 2, for example, indium tin oxide particle laminated films having a structure in which indium tin oxide particles are laminated are used as conductive materials such as antistatic agents, electron transport layers in solar cells, and conductive layers in various devices. The indium tin oxide particle laminated film is formed using an indium tin oxide particle dispersion liquid in which indium tin oxide particles are dispersed in a dispersion medium. Currently, the mainstream method for industrially producing indium tin oxide particles is a method involving high-temperature firing, such as the coprecipitation method disclosed in Patent Document 3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-185748 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-115206 [Patent Document 3] Japanese Patent Application Publication No. 05-201731 Summary of the Invention [Problem to be solved by the invention]

[0004] When using indium tin oxide particles as a conductive material, the particles must be uniformly coated to achieve high conductivity, and uniform coating requires small variations in particle shape and size. For example, when used as an electron transport layer in perovskite solar cells, the film thickness needs to be reduced to a few tens of nanometers, so the inclusion of coarse particles or variations in particle size have a significant impact on the solar cell characteristics. Here, when indium tin oxide particles are conventionally produced by the coprecipitation method described in Patent Document 3 or the like, the particle shape and particle size tend to be non-uniform.

[0005] The present invention has been made in view of the above-mentioned circumstances, and aims to provide indium tin oxide particles and an indium tin oxide particle dispersion that enable uniform application of indium tin oxide particles and stable formation of a thin indium tin oxide particle laminate film, a method for producing this indium tin oxide particle dispersion, and a method for producing an indium tin oxide particle laminate film using this indium tin oxide particle dispersion. [Means for solving the problem]

[0006] In order to solve the above problems, the indium tin oxide particles of aspect 1 of the present invention are characterized in that, when dispersed in a dispersion medium at a concentration of 0.5% by mass, the hydrodynamic particle diameter is measured by dynamic light scattering, and the ratio Dv / Dn of the mode of volume particle diameter Dv (nm) to the mode of number particle diameter Dn (nm) is within the range of 1.00 or more and 1.20 or less.

[0007] According to the indium tin oxide particles of aspect 1 of the present invention, when dispersed in a dispersion medium at a concentration of 0.5% by mass, the ratio Dv / Dn of the mode of volume particle diameter Dv (nm) to the mode of number particle diameter Dn (nm), obtained by measuring the hydrodynamic particle diameter by dynamic light scattering, is within the range of 1.00 or more and 1.20 or less. Therefore, the particle diameter of the indium tin oxide particles is sufficiently uniform, allowing the indium tin oxide particles to be uniformly coated, and enabling the stable formation of an indium tin oxide particle laminate film with excellent conductivity.

[0008] The indium tin oxide particles of aspect 2 of the present invention are the indium tin oxide particles of aspect 1, characterized in that the volume particle diameter mode Dv (nm) is in the range of 4 nm or more and 30 nm or less. According to the indium tin oxide particles of aspect 2 of the present invention, the volume particle diameter mode Dv (nm) is set within the range of 4 nm or more and 30 nm or less, and therefore, even a thin indium tin oxide particle laminate film having a thickness of, for example, 50 nm or less can be stably formed.

[0009] The indium tin oxide particle dispersion liquid of the third aspect of the present invention is characterized in that the indium tin oxide particles of the first or second aspect are dispersed in a dispersion medium. According to the indium tin oxide particle dispersion liquid of aspect 3 of the present invention, the indium tin oxide particles of aspect 1 or aspect 2 are dispersed, so that the indium tin oxide particles can be uniformly applied, and an indium tin oxide particle laminated film with excellent conductivity can be stably formed.

[0010] An indium tin oxide particle dispersion liquid of a fourth aspect of the present invention is the indium tin oxide particle dispersion liquid of the third aspect, characterized in that the dispersion medium is an organic solvent having 5 or more carbon atoms and containing no hydroxyl groups. According to the indium tin oxide particle dispersion liquid of the fourth aspect of the present invention, the dispersion medium is an organic solvent having 5 or more carbon atoms and not containing a hydroxyl group, so that the dispersion medium can be well coated on a material that is easily deteriorated by moisture, such as a perovskite layer. Furthermore, because the organic solvent has 5 or more carbon atoms and not containing a hydroxyl group, the indium tin oxide particles can be well dispersed.

[0011] The method for producing an indium tin oxide particle dispersion liquid according to aspect 5 of the present invention is a method for producing the indium tin oxide particle dispersion liquid according to aspect 3 or aspect 4, and is characterized by comprising an indium tin oxide particle production step of producing the indium tin oxide particles using as raw materials an indium hydroxycarboxylate having an average carboxylic acid substitution number of 1.8 to 2.6 and a tin compound, and a dispersion step of dispersing the produced indium tin oxide particles in the dispersion medium. The method for producing an indium tin oxide particle dispersion according to the fifth aspect of the present invention includes an indium tin oxide particle production step for producing the indium tin oxide particles using as raw materials an indium hydroxycarboxylate having an average carboxylic acid substitution number of 1.8 or more and 2.6 or less and a tin compound, and therefore it is possible to obtain indium tin oxide particles having a uniform particle size distribution as described above.

[0012] A method for producing an indium tin oxide particle laminate film according to a sixth aspect of the present invention is a method for producing an indium tin oxide particle laminate film, and is characterized by including a coating step of coating the indium tin oxide particle dispersion liquid according to the third or fourth aspect. The method for producing an indium tin oxide particle laminate film according to the sixth aspect of the present invention includes a coating step of coating the indium tin oxide particle dispersion liquid according to the third or fourth aspect, so that the indium tin oxide particles are uniformly arranged, making it possible to form an indium tin oxide particle laminate film having excellent conductivity. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide indium tin oxide particles and an indium tin oxide particle dispersion that can uniformly coat indium tin oxide particles and stably form a thin indium tin oxide particle laminate film, a method for producing this indium tin oxide particle dispersion, and a method for producing an indium tin oxide particle laminate film using this indium tin oxide particle dispersion. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic explanatory diagram of a perovskite solar cell including an indium tin oxide particle laminated film formed using an indium tin oxide particle dispersion liquid according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flow chart showing an example of a method for producing an indium tin oxide particle dispersion liquid according to an embodiment of the present invention. [Figure 3] FIG. 1 is a flow diagram showing an example of a method for producing an indium tin oxide particle laminated film according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Indium tin oxide particles, an indium tin oxide particle dispersion, a method for producing an indium tin oxide particle dispersion, and a method for producing an indium tin oxide particle laminate film, which are embodiments of the present invention, will be described below with reference to the accompanying drawings. Note that the following embodiments are specifically described to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the present invention.

[0016] The indium tin oxide particles and the indium tin oxide particle dispersion liquid according to the embodiment of the present invention are used, for example, when forming an indium tin oxide particle laminated film to be used as a conductive layer. The indium tin oxide particle laminated film according to an embodiment of the present invention is used, for example, as an electron transport layer of the perovskite solar cell shown in FIG. In this embodiment, the perovskite solar cell 10 has a structure in which an ITO film 12, a hole transport layer 13, a perovskite layer 14, an electron transport layer 15, and a back electrode 16 are laminated on the surface of a glass substrate 11, as shown in FIG.

[0017] The indium tin oxide particle laminated film constituting the electron transport layer 15 has a film thickness in the range of 10 nm to 100 nm. Therefore, in the indium tin oxide particle dispersion liquid of this embodiment, it is required to form a thin and precise indium tin oxide particle laminate film, and as a conductive material, the indium tin oxide particle laminate film is required to have excellent conductivity.

[0018] The conductivity of the indium tin oxide particle laminated film is greatly affected by the number of contact points between the indium tin oxide particles in the indium tin oxide particle laminated film. Therefore, in order to improve the conductivity of the indium tin oxide particle laminated film, it is necessary to form the indium tin oxide particle laminated film so that the indium tin oxide particles are uniformly arranged.

[0019] Therefore, in the indium tin oxide particles of this embodiment, the ratio Dv / Dn of the most frequent volume particle diameter Dv (nm) to the most frequent number particle diameter Dn (nm) obtained by measuring the hydrodynamic particle diameter by dynamic light scattering when the particles are dispersed in a dispersion medium at a concentration of 0.5% by mass is set to be in the range of 1.00 or more and 1.20 or less.

[0020] When the ratio Dv / Dn of the volume particle size mode Dv (nm) to the number particle size mode Dn (nm) is within the range of 1.00 to 1.20, the particle sizes of the indium tin oxide particles are uniform and have little variation, making it possible to form an indium tin oxide particle laminate film with excellent conductivity in which the indium tin oxide particles are uniformly arranged. The ratio Dv / Dn of the volume particle size mode Dv (nm) to the number particle size mode Dn (nm) is preferably in the range of 1.00 to 1.16, more preferably in the range of 1.00 to 1.13.

[0021] In addition, in the indium tin oxide particles of this embodiment, the volume particle diameter mode Dv (nm) is preferably within the range of 4 nm or more and 30 nm or less. When the volume particle diameter mode Dv (nm) of the indium tin oxide particles is 4 nm or more, the indium tin oxide particles can be stably produced. On the other hand, when the volume particle diameter mode Dv (nm) of the indium tin oxide particles is 30 nm or less, a thin indium tin oxide particle laminate film having a thickness of 50 nm or less can be stably formed. The lower limit of the volume particle size mode Dv (nm) of the indium tin oxide particles is more preferably 5 nm or more, and even more preferably 6 nm or more, while the upper limit of the volume particle size mode Dv (nm) of the indium tin oxide particles is more preferably 28 nm or less, and even more preferably 25 nm or less.

[0022] The indium tin oxide particle dispersion liquid of this embodiment is a dispersion medium in which the indium tin oxide particles of this embodiment are dispersed. Here, in the indium tin oxide particle dispersion liquid of this embodiment, the dispersion medium is preferably an organic solvent having 5 or more carbon atoms and containing no hydroxyl group. By using an organic solvent having 5 or more carbon atoms and not containing a hydroxyl group as the dispersion medium, it becomes possible to disperse the indium tin oxide particles well. Furthermore, by using an organic solvent, it is possible to apply the indium tin oxide particle dispersion onto the perovskite layer 14, which is easily deteriorated by moisture.

[0023] Next, an example of a method for producing an indium tin oxide particle dispersion liquid according to this embodiment will be described with reference to the flow diagram of FIG.

[0024] (Indium carboxylate hydroxide production step S01) First, the indium raw material is dissolved in ion-exchanged water to prepare solution A. On the other hand, sodium carboxylate is dissolved in ion-exchanged water, and then sodium hydroxide solution is added to prepare solution B. While stirring Solution B with a magnetic stirrer or the like, Solution A is added at a predetermined rate, and the mixture is maintained at a predetermined temperature to obtain an indium hydroxide carboxylate suspension.

[0025] The indium hydroxide carboxylate suspension is centrifuged to obtain an indium hydroxide carboxylate paste, which is then dissolved in ion-exchanged water and centrifuged again. Dissolution in ion-exchanged water and centrifugation are repeated until the conductivity of the separated supernatant falls below 50 μS / cm. The indium hydroxide carboxylate paste obtained as described above is dried to obtain an indium hydroxide carboxylate powder. Here, the amount of sodium hydroxide solution added is adjusted so that the pH of the separated supernatant liquid falls within the range of 3.5 to 7.0, thereby making the carboxylic acid coordination number fall within the range of 1.8 to 2.6.

[0026] (Raw material suspension production process S02) The indium hydroxide carboxylate and tin compound having an average carboxylic acid substitution number of 1.8 or more and 2.6 or less obtained as described above are suspended in a solvent to produce a raw material suspension. Here, it is preferable to use, as the tin compound, for example, tin(II) chloride, stannous octoate, or the like. As the solvent, for example, octyl ether, octadecene, or the like is preferably used.

[0027] (Indium tin oxide particle generation step S03) The raw material suspension is stirred with a magnetic stirrer or the like, and a carboxylic acid and an amine compound are added. Here, it is preferable to use, as the carboxylic acid, for example, oleic acid, isovaleric acid, propionic acid, decanoic acid, isobutyric acid, acetic acid, or the like. As the amine compound, for example, oleylamine, triethanolamine, diethanolamine, monoethanolamine, etc. are preferably used. This suspension is maintained at a temperature of 130° C. or higher and 450° C. or lower for 1.5 minutes or longer and 480 minutes or shorter to produce indium tin oxide particles, thereby obtaining a liquid containing indium tin oxide particles.

[0028] (Dispersion medium replacement step S04) This indium tin oxide particle-containing liquid is centrifuged and washed, and the dispersion medium is replaced with an organic solvent having 5 or more carbon atoms and not containing a hydroxyl group.

[0029] By the above-described steps, the indium tin oxide particle dispersion liquid of this embodiment can be produced.

[0030] Next, an example of a method for producing an indium tin oxide particle laminated film (electron transport layer 15) using the indium tin oxide particle dispersion liquid according to this embodiment will be described with reference to the flow diagram of FIG.

[0031] (Solid concentration adjustment step S11) First, an indium tin oxide particle dispersion liquid according to this embodiment is prepared, and the solid content concentration in the indium tin oxide particle dispersion liquid is adjusted to be within the range of 5 mass % to 45 mass %. The solid content concentration in the indium tin oxide particle dispersion is preferably 8 mass% or more, more preferably 10 mass% or more, and is preferably 40 mass% or less, more preferably 30 mass% or less.

[0032] (Coating process S12) Next, the indium tin oxide particle dispersion liquid with the adjusted solid content concentration is applied to the surface of the substrate. In this embodiment, the indium tin oxide particle dispersion liquid is applied to the surface of the substrate by a spin coater. The spin coating conditions in the coating step S12 are preferably a rotation speed of 500 rpm to 4000 rpm, a coating time of 3 seconds to 80 seconds, and a thickness of the coating film of 15 nm to 100 nm.

[0033] (Heating process S13) Next, the coating film (the coated indium tin oxide particle dispersion liquid) is heated to remove the dispersion medium, thereby forming an indium tin oxide particle laminated film (electron transport layer 15). The heating conditions in this heating step S13 are preferably a heating temperature in the range of 80° C. to 300° C. and a heating time in the range of 1 minute to 15 minutes.

[0034] Through the above-described steps, the indium tin oxide particle laminated film (electron transport layer 15) of this embodiment is formed. Here, in the indium tin oxide particle laminated film (electron transport layer 15) of this embodiment, the average film thickness is set to be in the range of 10 nm or more and 100 nm or less.

[0035] According to the indium tin oxide particles of this embodiment configured as described above, the ratio Dv / Dn of the volume particle diameter mode Dv (nm) to the number particle diameter mode Dn (nm) is within the range of 1.00 or more and 1.20 or less. This means that the particle diameters of the indium tin oxide particles are sufficiently uniform, allowing the indium tin oxide particles to be uniformly coated, and enabling the stable formation of an indium tin oxide particle laminate film (electron transport layer 15) with excellent conductivity.

[0036] In the indium tin oxide particles of this embodiment, when the volume particle diameter mode Dv (nm) is set within the range of 4 nm or more and 30 nm or less, a thin indium tin oxide particle laminate film (electron transport layer 15) having a thickness of, for example, 50 nm or less can be stably formed.

[0037] According to the indium tin oxide particle dispersion liquid of this embodiment, the indium tin oxide particles of this embodiment are dispersed in a dispersion medium, so that the indium tin oxide particles can be uniformly applied, and an indium tin oxide particle laminated film (electron transport layer 15) having excellent conductivity can be stably formed.

[0038] In the indium tin oxide particle dispersion of this embodiment, when the dispersion medium is an organic solvent having 5 or more carbon atoms and containing no hydroxyl groups, it can be well coated on the perovskite layer 14, which is prone to deterioration due to moisture. Furthermore, because the organic solvent has 5 or more carbon atoms and contains no hydroxyl groups, the indium tin oxide particles can be well dispersed.

[0039] The method for producing an indium tin oxide particle dispersion according to this embodiment includes an indium tin oxide particle production step S03 in which indium tin oxide particles are produced using as raw materials an indium hydroxycarboxylate having an average carboxylic acid substitution number of 1.8 or more and 2.6 or less and a tin compound. This makes it possible to obtain indium tin oxide particles with a uniform particle size distribution.

[0040] The method for producing an indium tin oxide particle laminate film of this embodiment includes a coating step S12 of coating the indium tin oxide particle dispersion of this embodiment, so that the indium tin oxide particles are uniformly arranged, making it possible to form an indium tin oxide particle laminate film (electron transport layer 15) with excellent conductivity.

[0041] Although one embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. In this embodiment, the indium tin oxide particle laminated film has been described as constituting the electron transport layer of the perovskite solar cell shown in FIG. 1, but it may also be used for other purposes, without being limited thereto. [Example]

[0042] A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

[0043] (Indium tin oxide particle dispersion) 4.5 mmol of the indium raw material shown in Table 1 and 0.5 mmol of the tin compound were suspended in 30 mL of the solvent shown in Table 1. After stirring for 15 minutes with a magnetic stirrer, 3 mmol of a carboxylic acid and 7 mmol of an amine compound shown in Table 1 were added, and stirring was continued for an additional 30 minutes. The resulting suspension was subjected to a heat treatment by holding it at 280° C. for 10 hours to produce indium tin oxide particles, thereby obtaining a liquid containing indium tin oxide particles. The obtained indium tin oxide particle-containing liquid was centrifuged and washed, and the solvent was replaced with the dispersion medium shown in Table 1, thereby producing indium tin oxide particle dispersion liquids of Invention Examples 1 to 10 and Comparative Examples 1 and 2.

[0044] Here, the coordination number of carboxylic acid in the indium raw material (indium hydroxide carboxylate) was measured as follows. The weight loss rate z due to oxide formation is calculated from the weight loss rate x at 100°C and the weight loss rate y at 600°C. z=y / x

[0045] The molecular weight of indium oxide (In2O3) is 277.64 g / mol, and two indium hydroxide carboxylate molecules make up one indium oxide molecule. Therefore, the molecular weight of indium hydroxide carboxylate is 277.64 / (2×z) g / mol. Therefore, the molecular weight of the indium hydroxide carboxylate ion other than indium is (277.64 / (2×z)-114.818) g / mol, which is the molecular weight of the total of 3 moles of carboxylate ion and hydroxide ion.

[0046] If the coordination number of a carboxylate ion with molecular weight a is w, then a×w+(3-w)×17.007=(277.64 / (2×z)-114.818) From this formula, the coordination number w is w=(138.82 / z-165.839) / (a-17.007) This becomes: Therefore, the coordination number w of the carboxylic acid can be calculated from z calculated from TG (thermal gravimetry) and the molar mass a of the carboxylic acid anion used in the synthesis.

[0047] (Indium tin oxide particle laminated film) The solid content concentration of the indium tin oxide particle dispersions of Inventive Examples 1 to 10 and Comparative Examples 1 and 2 was adjusted to 8 mass %. The indium tin oxide particle dispersion liquid with the adjusted solid content was spin-coated onto a 50 mm x 50 mm glass substrate using a spin coater (Mikasa Co., Ltd., model name: MS-A150) at 500 rpm for 60 seconds to form a coating film. The glass substrate on which the coating film was formed was heated on a hot plate at 100° C. for 3 minutes to form an indium tin oxide particle laminated film.

[0048] The indium tin oxide particle dispersions and indium tin oxide particle laminated films of Inventive Examples 1 to 10 and Comparative Examples 1 and 2 obtained as described above were evaluated for various items by the following methods.

[0049] (Hydrodynamic particle size of indium tin oxide particles) The indium tin oxide particle dispersion was diluted with the same solvent as the dispersion medium to adjust the indium tin oxide particle content to 0.5% by mass. The volume and number distributions of particle diameters were measured by dynamic light scattering using a particle size distribution analyzer (Malvern Zetasizer nano). The mode of volume particle diameter Dv (nm) and the mode of number particle diameter Dn (nm) were then calculated.

[0050] (Conductivity of indium tin oxide particle laminated film) The resistance of the indium tin oxide particle laminated film obtained as described above was measured using a surface resistance measuring device (product number: Loresta AP MCP-T400, probe: ASP probe (four-needle), manufactured by Mitsubishi Chemical Corporation).

[0051] [Table 1]

[0052] In Comparative Examples 1 and 2, the ratio Dv / Dn of the most frequent volume particle diameter Dv (nm) of the indium tin oxide particles to the most frequent number particle diameter Dn (nm) exceeded 1.20, and the formed indium tin oxide particle laminate film had high resistance and poor conductivity. In contrast, in Examples 1 to 10 of the present invention, the ratio Dv / Dn of the mode Dv (nm) of the volume particle diameter of the indium tin oxide particles to the mode Dn (nm) of the number particle diameter was within the range of 1.00 or more and 1.20 or less, and the formed indium tin oxide particle laminate film had low resistance and excellent conductivity.

[0053] As described above, it has been confirmed that the present invention can provide indium tin oxide particles and an indium tin oxide particle dispersion that can uniformly coat indium tin oxide particles and stably form a thin indium tin oxide particle laminate film, a method for producing this indium tin oxide particle dispersion, and a method for producing an indium tin oxide particle laminate film using this indium tin oxide particle dispersion.

Claims

1. Indium tin oxide particles characterized in that the ratio Dv / Dn of the most frequent volume particle diameter Dv (nm) to the most frequent number particle diameter Dn (nm) obtained by measuring the hydrodynamic particle diameter by dynamic light scattering when dispersed in a dispersion medium at a concentration of 0.5% by mass is in the range of 1.00 or more and 1.20 or less.

2. 2. The indium tin oxide particles according to claim 1, wherein the volume particle size mode Dv (nm) is in the range of 4 nm to 30 nm.

3. 10. An indium tin oxide particle dispersion liquid, comprising the indium tin oxide particles according to claim 1 dispersed in a dispersion medium.

4. 4. The indium tin oxide particle dispersion liquid according to claim 3, wherein the dispersion medium is an organic solvent having 5 or more carbon atoms and not containing a hydroxyl group.

5. A method for producing the indium tin oxide particle dispersion liquid according to claim 3 or 4, comprising the steps of:

1. A method for producing an indium tin oxide particle dispersion liquid, comprising: an indium tin oxide particle production step of producing the indium tin oxide particles using as raw materials an indium hydroxycarboxylate having an average carboxylic acid substitution number of 1.8 to 2.6 and a tin compound; and a dispersion step of dispersing the produced indium tin oxide particles in the dispersion medium.

6. A method for producing an indium tin oxide particle laminate film, comprising:

5. A method for producing an indium tin oxide particle laminated film, comprising a coating step of coating the indium tin oxide particle dispersion liquid according to claim 3 or 4.

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