Method for producing m-xene dispersion, method for producing solar cell, and m-xene dispersion

Abstract

Provided is a method for producing a Mxene dispersion liquid in which Mxene is dispersed in a low-polarity dispersion medium, a method for producing a solar cell using the method for producing a Mxene dispersion liquid, and a Mxene dispersion liquid produced by the method for producing a Mxene dispersion liquid. The method for producing a Mxene dispersion liquid (1) includes: a preparation step of preparing a water dispersion liquid of Mxene (11); a freeze-drying step of performing freeze-drying on the water dispersion liquid to leave the Mxene (11) and remove water (20); and a dispersion step of, after the freeze-drying step, dispersing the freeze-dried Mxene (11) in a low-polarity dispersion medium (21) that maintains flowability at an environmental temperature that maintains a dispersed state of the Mxene (11).

Description

Technical Field

[0001] This invention relates to a method for manufacturing an Mxene dispersion, a method for manufacturing a solar cell, and an Mxene dispersion. Background Technology

[0002] Previously, a technique for obtaining an aqueous dispersion of two-dimensional titanium carbide as a type of Mxene was known (see Patent Document 1).

[0003] According to the technology in Patent Document 1, hydrofluoric acid can be used to chemically peel off the aluminum atom layers from layered titanium aluminum carbide, causing two-dimensional titanium carbide to precipitate, and then dispersing the two-dimensional titanium carbide in water to obtain an aqueous dispersion.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2018-527275 Summary of the Invention

[0007] As illustrated in Patent Document 1, Mxene exhibits high dispersibility in water. Therefore, aqueous dispersions of Mxene are readily obtained. However, Mxene strongly aggregates in low-polarity dispersion media (non-polar dispersion media), making it difficult to obtain dispersions.

[0008] The purpose of this invention is to provide a method for manufacturing a Mxene dispersion formed by dispersing Mxene in a low-polarity dispersion medium, a method for manufacturing a solar cell using the method for manufacturing the Mxene dispersion, and a Mxene dispersion manufactured by the method for manufacturing the Mxene dispersion.

[0009] To achieve the above objectives, one aspect of the present invention provides a method for manufacturing an Mxene dispersion, a method for manufacturing a solar cell, and an Mxene dispersion.

[0010] [1] A method for manufacturing a Mxene dispersion includes: a preparation step of preparing an aqueous dispersion of Mxene; a freeze-drying step of freeze-drying the aqueous dispersion to leave the Mxene and remove water; and a dispersion step of dispersing the freeze-dried Mxene in a low-polarity dispersion medium that can maintain fluidity at the ambient temperature while maintaining the ambient temperature at a temperature that can maintain the dispersion state of the Mxene after the freeze-drying step.

[0011] [2] In the method for manufacturing Mxene dispersion as described in [1] above, the ambient temperature is below -87.5°C.

[0012] [3] The method for manufacturing Mxene dispersion according to [1] or [2] above, wherein the low polarity dispersion medium is toluene.

[0013] [4] A method for manufacturing a solar cell includes an electron transport layer, a hole transport layer, and a perovskite layer composed of perovskite crystals sandwiched between the electron transport layer and the hole transport layer. The method includes: a preparation step of preparing an aqueous dispersion of Mxene; a freeze-drying step of freeze-drying the aqueous dispersion to remove water while retaining Mxene; a dispersion step of dispersing the freeze-dried Mxene in a low-polarity dispersion medium that can maintain fluidity at the ambient temperature after the freeze-drying step; and a layer forming step of coating the Mxene dispersion on one side of the perovskite layer and removing the low-polarity dispersion medium to form the electron transport layer.

[0014] [5] In the method for manufacturing a solar cell according to [4] above, the ambient temperature is below -87.5°C.

[0015] [6] A Mxene dispersion, wherein Mxene is dispersed in a low polarity dispersion medium.

[0016] [7] According to the Mxene dispersion described in [6] above, the low polarity dispersion medium is toluene.

[0017] According to the present invention, a method for manufacturing a Mxene dispersion formed by dispersing Mxene in a low-polarity dispersion medium, a method for manufacturing a solar cell using the method for manufacturing the Mxene dispersion, and a Mxene dispersion manufactured by the method for manufacturing the Mxene dispersion are provided. Attached Figure Description

[0018] Figure 1 (a) to (e) are flowcharts showing the experimental process for preparing a Mxene dispersion in a low-polarity dispersion medium as a comparative example.

[0019] Figure 2 (a) to (d) are flowcharts showing the procedures for other experiments aimed at preparing Mxene dispersions in low-polarity dispersion media, which serve as comparative examples.

[0020] Figure 3(a) to (d) are flowcharts illustrating the manufacturing process of a Mxene dispersion in a low-polarity dispersion medium, as an example of an embodiment of the present invention.

[0021] Figure 4 This is a cross-sectional view along the thickness direction of a perovskite solar cell with a basic structure.

[0022] Symbol Explanation

[0023] 1 Mxene dispersion

[0024] 10 Max phase

[0025] 11 Mxene

[0026] 20 water

[0027] 21 Low-polarity dispersion media

[0028] 3. Perovskite Solar Cells

[0029] 31 Perovskite layer

[0030] 32 Electron Transport Layer Detailed Implementation

[0031] The method for manufacturing Mxene dispersion according to embodiments of the present invention is a method for obtaining Mxene dispersion in a low-polarity dispersion medium. Since the Mxene dispersion in the low-polarity dispersion medium does not contain water, it is suitable for applications where water content is a problem.

[0032] Mxene is a two-dimensional layered compound of preperiod transition metals such as Ti (titanium), V (vanadium), and Nb (niobium) with one or both of C (carbon) and N (nitrogen).

[0033] The typical structure of Mxene is represented by the chemical formula M n+1 X n (n is 1 to 4). Here, M is the previous periodic transition metal, and X is one or both of C and N. In this structure, there are n+1 layers of M and n layers of X, with the M layers and X layers stacked alternately.

[0034] A representative example of Mxene is Ti3C2 (two-dimensional titanium carbide), a layered compound consisting of three layers of titanium and two layers of carbon.

[0035] Mxene is obtained using a substance called the Max phase as a precursor. The Max phase has a stacked structure consisting of the aforementioned M layer, X layer, Al, Si, etc. (called the A layer). Mxene is obtained by selectively etching the A layer using hydrofluoric acid or similar methods. A typical structure of the Max phase is M... n＋1 AX n (A represents Al, Si, etc.).

[0036] Furthermore, through reaction with etchants such as hydrofluoric acid, terminal functional groups such as -OH, =O, and -F are generated on the surface of Mxene. These terminal functional groups endow Mxene with hydrophilicity, thus Mxene exhibits high dispersibility in water.

[0037] In addition, Mxene has excellent electrical conductivity, making it suitable, for example, as a material for the electron transport layer in perovskite solar cells.

[0038] Hereinafter, the method for manufacturing the Mxene dispersion according to the embodiments will be described in detail while comparing it with the comparative examples.

[0039] (Comparative Example 1)

[0040] Figure 1 (a) to (e) are diagrams showing the experimental procedure (designated as Comparative Example 1) for the purpose of preparing a Mxene dispersion in a low-polarity dispersion medium.

[0041] In Comparative Example 1, firstly, as Figure 1 As shown in (a), Max phase 10 is prepared to become the precursor of Mxene.

[0042] Next, as Figure 1 As shown in (b), after selectively removing the A layer of Max phase 10 using an etchant such as hydrofluoric acid (HF), it is dispersed in water 20 to obtain an aqueous dispersion of Mxene11 in water 20.

[0043] At this point, for example, if Ti3AlC2 is used as the Max phase 10, Al is selectively removed by etching to obtain Ti3C2 as Mxene11. For example, Ti3AlC2 is immersed in hydrofluoric acid with a concentration of 10-50% by mass, stirred at an ambient temperature of 25-60°C and a stirring speed of 1500-2000 rpm for 2-8 hours. The reaction solution is then filtered, repeatedly washed with water until the pH is neutral, and then centrifuged to obtain Ti3C2. In addition, the concentration of Mxene11 dispersed in water 20 is, for example, 0.5-5% by mass.

[0044] As an etchant for removing the aforementioned layer A, a mixture containing HF, NH4HF2, HCl, and LiF can be used, for example. － The solution.

[0045] Next, as Figure 1 As shown in (c), water 20, which serves as the dispersion medium, is removed by filtration. In this process, by removing water 20, Mxene 11 is re-layered to form a stack 12 of Mxene 11. This re-layering of Mxene 11 is not intermediated by impurity layers such as A layers, but is based on the strong interactions between Mxene 11s from intermolecular forces. That is, the stack 12 is obtained by directly stacking multiple Mxene 11s without intermediate impurity layers.

[0046] Next, as Figure 1 As shown in (d) and (e), a low-polarity dispersion medium 21, such as toluene, is added to a container containing the laminate 12. However, the laminate 12 does not separate into a single layer of Mxene 11 and disperse in the low-polarity dispersion medium 21, and the desired Mxene dispersion in the low-polarity dispersion medium cannot be obtained.

[0047] (Comparative Example 2)

[0048] Figure 2 (a) to (d) are diagrams showing the procedures for other experiments (designated as Comparative Example 2) aimed at preparing Mxene dispersions in a low-polarity dispersion medium.

[0049] In Comparative Example 2, firstly, an aqueous dispersion of Mxene11 dispersed in water 20 was obtained by the same method as in Comparative Example 1.

[0050] Next, as Figure 2 As shown in (a) and (b), ethanol 22 was added to the aqueous dispersion of Mxene 11, causing Mxene 11 to condense in a mixed solution 23 of water 20 and ethanol 22, resulting in amorphous aggregates 13 of Mxene. This was to prevent the re-layering of Mxene 11 as seen in Comparative Example 1.

[0051] Next, as Figure 2 As shown in (c) and (d), the mixed solution 23, which serves as the dispersion medium, is removed by filtration, and then a low-polarity dispersion medium 21, such as toluene, is added to the container holding the amorphous aggregates 13 of Mxene. However, the amorphous aggregates 13 of Mxene do not deagglomerate in the low-polarity dispersion medium 21, and the desired Mxene dispersion in the low-polarity dispersion medium cannot be obtained.

[0052] (Example)

[0053] Figure 3 (a) to (d) are flowcharts illustrating the manufacturing process of Mxene dispersion 1, which is an example of an embodiment of the present invention, in which Mxene is dispersed in a low polarity dispersion medium (as an example).

[0054] In the embodiment, firstly, as Figure 3 As shown in (a) and (b), an aqueous dispersion of Mxene11 in water 20 was obtained by the same method as in Comparative Example 1.

[0055] Next, as Figure 3 As shown in (c) and (d), the aqueous dispersion of Mxene11 is freeze-dried, leaving Mxene11 and removing water 20. Then, while maintaining the ambient temperature at a temperature that can maintain the dispersion state of Mxene11 (e.g., below -87.5°C), a low polarity dispersion medium 21 is added to the container containing the freeze-dried Mxene11, so that Mxene11 is dispersed in the low polarity dispersion medium 21.

[0056] In this process, if the ambient temperature is increased (e.g., returned to room temperature) before dispersing Mxene11 in the low-polarity dispersion medium 21, aggregation may occur. This is thought to be because the temperature rise after freeze-drying increases the intermolecular forces acting between Mxene11 molecules, causing nearby Mxene11 molecules to aggregate. As an example, by maintaining the ambient temperature below -87.5°C after freeze-drying, it was confirmed that aggregation of Mxene11 could be prevented and the dispersion maintained.

[0057] For the low-polarity dispersion medium 21 used in this process, a low-polarity dispersion medium that can maintain fluidity at an ambient temperature (e.g., below -87.5°C) that can maintain the dispersion state of Mxene11 described above can be used, such as toluene.

[0058] As described above, in the embodiments, no re-layering or aggregation of Mxene11 occurs, and a Mxene dispersion 1 in which Mxene11 is dispersed in a low polarity dispersion medium 21 can be obtained.

[0059] That is, according to an embodiment of the present invention, a method for manufacturing Mxene dispersion 1 can be provided, comprising: a preparation step of preparing an aqueous dispersion of Mxene 11; a freeze-drying step of freeze-drying the aqueous dispersion to leave Mxene 11 and remove water 20; and a dispersion step of dispersing the freeze-dried Mxene 11 in a low polarity dispersion medium 21 that can maintain fluidity at the ambient temperature while maintaining the ambient temperature at a temperature that can maintain the dispersion state of Mxene 11 (e.g., below -87.5°C).

[0060] Next, an application example of Mxene dispersion 1 will be described. In this application example, Mxene dispersion 1 is used as a material for the electron transport layer of a perovskite solar cell.

[0061] Figure 4 This is a cross-sectional view along the thickness direction of a perovskite solar cell 3, which has a basic structure. The perovskite solar cell 3 includes an electron transport layer 32, a hole transport layer 33, and a perovskite layer 31 composed of perovskite crystals sandwiched between the electron transport layer 32 and the hole transport layer 33.

[0062] In addition, the perovskite solar cell 3 includes a substrate 30, an electrode 34 disposed on the electron transport layer 32 side, an electrode 35 disposed on the hole transport layer 33 side, and a sealing material 36 that seals the perovskite layer 31, the electron transport layer 32, the hole transport layer 33, and the electrode 34.

[0063] The perovskite solar cell 3 absorbs light from the outside and converts that energy into electrical energy, thereby generating electricity. More specifically, the perovskite layer 31 generates charge separation by absorbing light. Electrons generated by charge separation flow to the electrode 34 through the electron transport layer 32, while holes generated by charge separation flow to the electrode 35 through the hole transport layer 33. Furthermore, the generated electrical energy can be supplied to external devices via wiring or the like connected to the electrode 35.

[0064] When the perovskite solar cell 3 extracts light from the substrate 30 side to generate electricity, the substrate 30 and electrode 35 are made of a transparent material. Alternatively, when the perovskite solar cell 3 extracts light from the sealing material 36 side to generate electricity, the sealing material 36 and electrode 34 are made of a transparent material.

[0065] In the manufacture of the perovskite solar cell 3, for example, a hole transport layer 33, a perovskite layer 31, an electron transport layer 32, and an electrode 34 are sequentially stacked on an electrode 35 patterned on a substrate 30 and sealed with a sealing material 36.

[0066] In the formation of the electron transport layer 32, Mxene dispersion 1 is coated on the perovskite layer 31, and the low polarity dispersion medium 21 such as toluene contained in the Mxene dispersion 1 is removed by evaporation or heating-based evaporation, so that it is solidified.

[0067] The Mxene dispersion 1 described above can be coated by spin coating or the like. Spin coating conditions are, for example, 1000 rpm × 60 sec. Furthermore, the removal of the low-polarity dispersion medium 21 can be performed, for example, by heat treatment at 80°C × 5 min. It should be noted that various known methods can be used for forming components other than the electron transport layer 32 of the perovskite solar cell 3.

[0068] The perovskite crystals constituting the perovskite layer 31 have the property that they will be significantly degraded or damaged if they come into contact with water. Therefore, coatings containing water cannot be used to form the electron transport layer 32. The Mxene dispersion 1 uses a low-polarity dispersion medium 21 as the dispersion medium for Mxene 11 and does not contain water. Therefore, the electron transport layer 32 can be formed without degrading or damaging the perovskite layer 31.

[0069] That is, according to an embodiment of the present invention, a method for manufacturing a solar cell can be provided as a method for manufacturing a perovskite solar cell 3 that can form an electron transport layer 32 without deteriorating or damaging the perovskite layer 31, comprising: a preparation step, preparing an aqueous dispersion of Mxene 11; a freeze-drying step, performing freeze-drying on the aqueous dispersion to leave Mxene 11 and remove water 20; a dispersion step, after the freeze-drying step, dispersing the freeze-dried Mxene 11 in a low-polarity dispersion medium 21 that can maintain fluidity at the ambient temperature (e.g., below -87.5°C) while maintaining the ambient temperature to obtain Mxene dispersion 1; and a layer forming step, coating the Mxene dispersion 1 on one surface of the perovskite layer 31 and removing the low-polarity dispersion medium 21 to form an electron transport layer 32.

[0070] (Effects of the implementation method)

[0071] According to the embodiments of the present invention described above, a Mxene dispersion 1 in which Mxene11 is dispersed in a low-polarity dispersion medium 21 can be obtained. In addition, the manufactured Mxene dispersion 1 can be used as a raw material for the electron transport layer 32 without deteriorating or damaging the perovskite layer 31 to manufacture a perovskite solar cell 3.

[0072] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Furthermore, the constituent elements of the above embodiments can be arbitrarily combined without departing from the spirit of the invention. Additionally, the above embodiments do not limit the scope of protection of the invention. It should also be noted that the feature combinations described in the embodiments are not necessarily all necessary means to solve the problems of the invention.

Claims

1. A method for manufacturing an Mxene dispersion, comprising: Preparation step: Prepare an aqueous dispersion of Mxene; In the freeze-drying process, the aqueous dispersion is freeze-dried to remove water while retaining the Mxene; and In the dispersion process, after the freeze-drying process, the freeze-dried Mxene is dispersed in a low-polarity dispersion medium that maintains fluidity at the ambient temperature while keeping the ambient temperature at a temperature that can maintain the dispersion state of the Mxene.

2. The method for manufacturing the Mxene dispersion according to claim 1, wherein, The ambient temperature is below -87.5℃.

3. The method for manufacturing the Mxene dispersion according to claim 1 or 2, wherein, The low-polarity dispersion medium is toluene.

4. A method for manufacturing a solar cell, comprising an electron transport layer, a hole transport layer, and a perovskite layer composed of perovskite crystals sandwiched between the electron transport layer and the hole transport layer, comprising: Preparation step: Prepare an aqueous dispersion of Mxene; In the freeze-drying process, the aqueous dispersion is freeze-dried to remove water while retaining Mxene; In the dispersion step, after the freeze-drying step, while maintaining the ambient temperature at a temperature capable of preserving the dispersed state of the Mxene, the freeze-dried Mxene is dispersed in a low-polarity dispersion medium that maintains fluidity at the ambient temperature, resulting in an Mxene dispersion; and In the layer formation process, the Mxene dispersion is coated on one side of the perovskite layer to remove the low-polarity dispersion medium and form the electron transport layer.

5. The method for manufacturing a solar cell according to claim 4, wherein, The ambient temperature is below -87.5℃.

6. A Mxene dispersion, wherein Mxene is dispersed in a low-polarity dispersion medium.

7. The Mxene dispersion according to claim 6, wherein, The low-polarity dispersion medium is toluene.

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