Tin alkoxide solution and method for manufacturing conductive film

Abstract

To provide: a tin alkoxide solution that is excellent in conductivity and can be stably deposited even on a surface of an organic material; and a method for manufacturing a conductive film.SOLUTION: A tin alkoxide solution contains a solvent and tin alkoxide. A content of Sn in the tin alkoxide solution is in a range of 2 mass% or more and less than 20 mass%. The tin alkoxide solution further contains an alkali metal ion in a range of 0.1 massppm or more and less than 10 massppm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tin alkoxide solution applicable, for example, when forming a conductive film or the like, and a method for manufacturing a conductive film using this tin alkoxide solution.

Background Art

[0002] Tin oxide particles are used as a conductive film for antistatic agents, electron transport layers of solar cells, and the like. For example, in the electron transport layer of a perovskite solar cell, a tin oxide particle laminated film formed using a tin oxide particle dispersion is used. However, in a conductive film produced using a tin oxide particle dispersion, a decrease in conductivity due to interfacial resistance between tin oxide particles, interfacial resistance on the surface of the conductive film, and interfacial resistance caused by voids between particles cannot be avoided. In addition, while film formation by coating a tin oxide particle dispersion is easy, it is generally less conductive than a sputtered film.

[0003] On the other hand, as described in Patent Document 1, it is possible to form a conductive film by a method other than coating and drying a particle dispersion using tin aminoalkoxide, but a high-energy process such as MOCVD is required for film formation. In order to produce a highly conductive conductive film from such an organotin compound, it is necessary to convert it to crystalline tin oxide. Referring to the crystallization of tin oxide by the coprecipitation method shown in Patent Document 2, it is necessary to heat to about 600°C in order to obtain tin hydroxide or tin alkoxide as crystalline tin oxide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, for example, when forming a conductive film as an electron transport layer of a perovskite solar cell, since the perovskite solar cell is formed on a substrate made of a material with low heat resistance such as an organic film or an organometallic compound, it was impossible to form a conductive film using the tin alkoxide as described above. Further, for example, when forming a conductive film as an electron transport layer of a perovskite solar cell, it is required to have even better conductivity.

[0006] This invention has been made in view of the above-described circumstances, and an object thereof is to provide a tin alkoxide solution that is excellent in conductivity and can stably form a conductive film on the surface of an organic material, and a method for manufacturing a conductive film.

Means for Solving the Problems

[0007] As a result of intensive studies by the present inventors to solve the above problems, it has been found that by adding alkali metal ions to a tin alkoxide solution, a conductive film having sufficiently excellent conductivity can be formed without firing at a low temperature to generate crystalline tin oxide.

[0008] The tin alkoxide solution according to Embodiment 1 of the present invention is a tin alkoxide solution containing a solvent and tin alkoxide, wherein the content of Sn in the tin alkoxide solution is in the range of 2 mass% or more and less than 20 mass%, and further contains alkali metal ions in the range of 0.1 mass ppm or more and less than 10 mass ppm.

[0009] According to the tin alkoxide solution of Embodiment 1 of the present invention, since the Sn content in the tin alkoxide solution is in the range of 2 mass% or more and less than 20 mass%, the tin alkoxide is sufficiently dissolved in the solvent, can be stably applied, and a conductive film can be stably formed by heating and drying / firing the applied tin alkoxide solution. And since it contains alkali metal ions in the range of 0.1 mass ppm or more and less than 10 mass ppm, conductivity is ensured even when heated and dried / fired under low-temperature conditions, and it becomes possible to stably form a conductive film on the surface of the organic material.

[0010] The tin alkoxide solution of Embodiment 2 of the present invention is characterized in that, in the tin alkoxide solution of Embodiment 1, the boiling point of the solvent is less than 200°C. According to the tin alkoxide solution of Embodiment 2 of the present invention, since the boiling point of the solvent is less than 200°C, it becomes possible to remove the solvent under low-temperature conditions of less than 200°C, and by heating and drying / firing the tin alkoxide solution applied to the surface of the organic material under low-temperature conditions, it becomes possible to form a more stable conductive film.

[0011] The tin alkoxide solution of Embodiment 3 of the present invention is characterized in that, in the tin alkoxide solution of Embodiment 1 or Embodiment 2, the tin alkoxide is one or more selected from tin(IV) methoxide and tin(IV) ethoxide. According to the tin alkoxide solution of Embodiment 3 of the present invention, since the tin alkoxide is one or more selected from tin(IV) methoxide and tin(IV) ethoxide, it becomes possible to surely form a conductive film excellent in conductivity by heating and drying / firing the applied tin alkoxide solution.

[0012] The method for manufacturing a conductive film according to Embodiment 4 of the present invention includes a coating step of coating any one of the tin alkoxide solutions of Embodiments 1 to 3, and a heating step of heating and drying / firing the applied tin alkoxide solution. According to the method for manufacturing a conductive film of Embodiment 4 of the present invention, since any one of the tin alkoxide solutions of Embodiments 1 to 3 is used, conductivity can be ensured even when drying and firing are performed under low-temperature conditions in the heating step, and it becomes possible to stably form a conductive film on the surface of the organic material.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a tin alkoxide solution that is excellent in conductivity and can stably form a conductive film on the surface of an organic material, and a method for manufacturing a conductive film.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] Hereinafter, a tin alkoxide solution which is an embodiment of the present invention and a method for manufacturing a conductive film will be described with reference to the accompanying drawings. Note that each of the embodiments shown below is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0016] The tin alkoxide solution which is an embodiment of the present invention is used when forming a conductive film. And the conductive film which is an embodiment of the present invention is used, for example, as an electron transport layer of the perovskite solar cell shown in FIG. 1. In this embodiment, as shown in FIG. 1 for example, 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 substrate 11. Note that in the conductive film constituting the electron transport layer 15, the film thickness is in the range of 10 nm or more and 100 nm or less.

[0017] Here, in this embodiment, the substrate 11 is a transparent substrate made of an organic material. Therefore, in the tin alkoxide solution of this embodiment, it is required to stably form a conductive film on the substrate 11 made of an organic material. In addition, in the conductive film constituting the electron transport layer 15, as the conductive material, it is required to be particularly excellent in conductivity.

[0018] Therefore, in the tin alkoxide solution of this embodiment, it is made to contain alkali metal ions in the range of 0.1 mass ppm or more and less than 10 mass ppm. By containing alkali metal ions in the range of 0.1 mass ppm or more and less than 10 mass ppm, a conductive film excellent in conductivity can be formed even without firing the tin alkoxide solution at a low temperature to generate crystalline tin oxide. Note that the lower limit of the content of alkali metal ions is preferably 0.2 mass ppm or more, and more preferably 0.8 mass ppm or more. On the other hand, the upper limit of the content of alkali metal ions is preferably 8 mass ppm or less, and more preferably 2 mass ppm or less.

[0019] Therefore, in the tin alkoxide solution of this embodiment, the content of Sn in the tin alkoxide solution is in the range of 2 mass% or more and less than 20 mass%. By setting the Sn content in the tin alkoxide solution to 2 mass% or more, a conductive film can be formed by heating and drying / firing the tin alkoxide solution. On the other hand, by setting the Sn content in the tin alkoxide solution to less than 20 mass%, the tin alkoxide can be dissolved in the solvent and stable coating becomes possible. Note that the lower limit of the Sn content in the tin alkoxide solution is preferably 2.5 mass% or more, and more preferably 3 mass% or more. On the other hand, the upper limit of the Sn content in the tin alkoxide solution is preferably 12 mass% or less, and more preferably 9 mass% or less.

[0020] Here, in the tin alkoxide solution of the present embodiment, the boiling point of the solvent is preferably less than 200°C. By setting the boiling point of the solvent to less than 200°C, it becomes possible to stably form a conductive film by heating and drying / firing under low-temperature conditions. Examples of solvents having a boiling point of less than 200°C include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetonitrile, diethylamine, triethylamine, 2-aminoethanol, ethylene glycol, etc.

[0021] Also, in the tin alkoxide solution of the present embodiment, the tin alkoxide is preferably one or more selected from tin(IV) methoxide and tin(IV) ethoxide. By using one or more selected from tin(IV) methoxide and tin(IV) ethoxide as the tin alkoxide, it becomes possible to surely form a conductive film.

[0022] Next, an example of the manufacturing method of the tin alkoxide solution of the present embodiment will be described using the flowchart of FIG. 2.

[0023] (Raw material preparation step S01) First, prepare a tin raw material (a compound containing tin) and an alkoxide raw material. Here, as the alkoxide raw material, one containing an alkali metal is used. Here, as the tin raw material, tin(IV) chloride pentahydrate, tin(IV) chloride anhydride, tin(II) chloride dihydrate, tin(II) chloride anhydride, etc. can be used. Also, as the alkoxide raw material, sodium methoxide, sodium ethoxide, sodium isopropoxide, potassium methoxide, potassium ethoxide, lithium ethoxide, etc. can be used.

[0024] (Dissolution step S02) Next, add and dissolve the above-mentioned tin raw material (a compound containing tin) and alkoxide raw material weighed at a predetermined ratio in a solvent, and then let it stand for a certain period of time. At this time, the tin raw material and the alkoxide raw material containing an alkali metal react to form tin alkoxide, and alkali metal ions will be contained. Note that the standing time is preferably in the range of 12 hours or more and 168 hours or less.

[0025] (Precipitate removal step S03) Remove the precipitate from the standing solution and recover the supernatant (liquid component). Thereby, the tin alkoxide solution of this embodiment can be obtained.

[0026] Next, an example of a method for manufacturing a conductive film using the tin alkoxide solution of this embodiment will be described with reference to the flowchart of FIG. 3.

[0027] (Solid content concentration adjustment step S11) First, prepare the tin alkoxide solution of this embodiment, and adjust the solid content concentration in the tin alkoxide solution to be within the range of 3 mass% or more and 30 mass% or less. Note that the solid content concentration in the tin alkoxide solution is preferably 4 mass% or more, more preferably 5 mass% or more. Also, the solid content concentration in the tin alkoxide solution is preferably 20 mass% or less, more preferably 12 mass% or less.

[0028] (Coating step S12) Next, the tin alkoxide solution with adjusted solid content concentration is applied onto the substrate. There is no particular limitation on the coating method, but in this embodiment, the tin alkoxide solution is coated onto the substrate by a spin coater. In the coating step S12, when coating with a spin coater, the spin coating conditions are preferably within the range of a rotation speed of 500 rpm or more and 5000 rpm or less, and a coating time of 5 seconds or more and 60 seconds or less. Also, the thickness of the coating film is preferably within the range of 10 nm or more and 100 nm or less.

[0029] (Heating step S13) Next, the coating film (the coated tin alkoxide solution) is heated to remove the solvent, and drying and firing are performed to form a conductive film. The heating conditions in this heating step S13 are preferably within the range of a heating temperature of 15°C or more and 200°C or less, and a heating time of 1 minute or more and 120 minutes or less.

[0030] Through the above steps, the conductive film of this embodiment is formed. Here, in the conductive film of this embodiment, the average value of the film thickness is within the range of 10 nm or more and 100 nm or less, the standard deviation of the film thickness is within the range of 3 nm or more and 40 nm or less, and the coefficient of variation CV of the film thickness is 50% or less.

[0031] According to the tin alkoxide solution of the present embodiment configured as described above, since the Sn content in the tin alkoxide solution is 2 mass% or more, a conductive film can be formed by heating the applied tin alkoxide solution for drying and firing. Further, since the Sn content in the tin alkoxide solution is within the range of less than 20 mass%, the tin alkoxide can be dissolved in the solvent, and stable coating can be performed. And since it contains alkali metal ions in the range of 0.1 mass ppm or more and less than 10 mass ppm, conductivity can be ensured even when fired under low-temperature conditions, and it becomes possible to stably form a conductive film on the surface of the organic material.

[0032] In the tin alkoxide solution of the present embodiment, when the boiling point of the solvent is less than 200 °C, even if heated under low-temperature conditions of less than 200 °C in the heating step S13, the solvent can be removed, and by drying and firing the tin alkoxide solution applied to the surface of the organic material, it becomes possible to more stably form a conductive film.

[0033] In the tin alkoxide solution of the present embodiment, when the tin alkoxide is one or more selected from tin(IV) methoxide and tin(IV) ethoxide, it becomes possible to surely form a conductive film excellent in conductivity by heating the applied tin alkoxide solution for drying and firing.

[0034] According to the method for manufacturing a conductive film of the present embodiment, since it includes a coating step S12 of coating the tin alkoxide solution of the present embodiment and a heating step S13 of heating the applied tin alkoxide solution for drying and firing, even if heated, dried, and fired under low-temperature conditions in the heating step S13, a conductive film excellent in conductivity can be formed, and it becomes possible to stably form a conductive film on the surface of the organic material.

[0035] As described above, one embodiment of the present invention has been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention. In this embodiment, the conductive film has been described as constituting the electron transport layer of the perovskite solar cell shown in FIG. 1, but it may be used for other applications not limited thereto.

Example

[0036] A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

[0037] (Example 1 of the present invention) 0.743 g of tin(IV) chloride pentahydrate (tin raw material) and 0.742 g of sodium ethoxide (alkoxide raw material) were dissolved in 10 mL of ethanol (solvent), and this was allowed to stand for 7 days. Thereafter, the precipitate was removed and the supernatant was recovered to obtain the tin alkoxide solution of Example 1 of the present invention.

[0038] (Examples 2 to 15 of the present invention, Comparative Examples 1 and 2) Using the tin raw materials, alkoxide raw materials, and solvents shown in Table 1, tin alkoxide solutions of Examples 2 to 15 of the present invention and Comparative Examples 1 and 2 were obtained by the same procedure as in Example 1 of the present invention. At this time, by adjusting the blending amounts of the tin raw material and the alkoxide raw material and the amount of the solvent, the Sn content and the alkali metal ion content in the tin alkoxide solution were adjusted.

[0039] (Film formation of conductive film) The solid content concentration of the obtained tin alkoxide solution was adjusted to 8 mass%. The tin alkoxide solution with adjusted solid content was spin-coated on a 50 mm × 50 mm glass substrate at 500 rpm for 60 seconds using a spin coater (manufactured by Mikasa Co., Ltd., model name: MS-A150) 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 a conductive film.

[0040] For the tin alkoxide solution and the conductive film obtained as described above, each item was evaluated by the following methods.

[0041] (Sn content in tin alkoxide solution) A measurement sample was collected from the tin alkoxide solution obtained as described above, wet decomposition of organic substances with sulfuric acid-nitric acid was performed as a pretreatment, composition analysis was performed by ICP emission spectrometry, and the Sn content was quantified. The wavelength used was 189.989 nm.

[0042] (Alkali metal ion content in the tin alkoxide solution) A measurement sample was collected from the tin alkoxide solution obtained as described above, wet decomposition of organic substances with sulfuric acid-nitric acid was performed as a pretreatment, composition analysis was performed by ICP emission spectrometry, and the alkali metal ion content was quantified. The wavelength used was 589.592 nm.

[0043] (Conductivity of the conductive film) Regarding the conductive film obtained as described above, resistance measurement was performed using a surface resistance meter (product number: Loresta AP MCP-T400 probe: ASP probe (four needles), manufactured by Mitsubishi Chemical Corporation).

[0044]

Table 1

[0045] In Comparative Example 1, the content of alkali metal ions in the tin alkoxide solution was less than 1 mass ppm, the resistance of the formed conductive film was large, and it could not be measured. In Comparative Example 2, the content of alkali metal ions in the tin alkoxide solution was as high as 180 mass ppm, the resistance of the formed conductive film was large, and it could not be measured. On the other hand, in Invention Examples 1 to 15 in which the content of alkali metal ions in the tin alkoxide solution was within the scope of the present invention, the electric resistance value was sufficiently low and the conductivity was excellent.

[0046] As described above, it was confirmed that according to the present invention, it is possible to provide a tin alkoxide solution excellent in conductivity and capable of stably forming a conductive film on the surface of an organic material, and a method for manufacturing a conductive film.

Claims

1. A tin alkoxide solution containing a solvent and a tin alkoxide, The Sn content in the tin alkoxide solution is in the range of 2 mass% or more and less than 20 mass%, A tin alkoxide solution further comprising an alkali metal ion in a range of 0.1 ppm by mass or more and less than 10 ppm by mass.

2. 2. The tin alkoxide solution according to claim 1, wherein the boiling point of the solvent is less than 200°C.

3. 2. The tin alkoxide solution according to claim 1, wherein the tin alkoxide is one or more selected from the group consisting of tin (IV) methoxide and tin (IV) ethoxide.

4. 4. A method for producing a conductive film, comprising: a coating step of coating a tin alkoxide solution according to claim 1; and a heating step of heating the coated tin alkoxide solution to dry and bake it.

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