Bioplastic substrates, methods for manufacturing bioplastic substrates, electronic devices, organic thin-film solar cells

Abstract

The present invention provides a bioplastic substrate that is sufficiently thin, resistant to deformation by heat, has a smooth surface, and is suitable for use as a substrate for electronic devices, as well as a method for manufacturing the same. [Solution] A bioplastic substrate having a film-like shape containing cellulose acetate propionate resin, with a thickness of 0.1 mm to 1.0 mm and a surface roughness (SRa) of 30 nm or less, wherein a 20 mm square test piece taken from the bioplastic substrate is placed on a horizontal mounting surface and heated at 80°C for 15 minutes, and the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface is 0.3 mm or less.

Description

Technical Field

[0001] The present invention relates to a biodegradable plastic substrate, a method for manufacturing a biodegradable plastic substrate, an electronic device, and an organic thin-film solar cell.

Background Art

[0002] Organic thin-film solar cells have attracted attention as next-generation solar cells. An organic thin-film solar cell has a substrate, a cathode and an anode formed on the substrate, and a photoelectric conversion film formed between the cathode and the anode.

[0003] Conventionally, glass substrates have been widely used as substrates for organic thin-film solar cells. For example, Patent Document 1 and Patent Document 2 describe organic thin-film solar cells using glass substrates on which an anode made of indium-tin composite oxide (ITO) is formed on the surface. Further, Patent Document 2 describes using a PET resin substrate made of PET (polyethylene terephthalate) resin as a substrate for an organic thin-film solar cell.

[0004] Conventionally, there are resin substrates as substrates for electronic devices. Examples of resin substrates include those made of resins such as PET (polyethylene terephthalate) resin, PC (polycarbonate) resin, and PI (polyimide) resin.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, technologies utilizing bioplastics have attracted attention in various technological fields from the perspective of Sustainable Development Goals (SDGs) and environmental protection. In the case of electronic device substrates, it is considered preferable to use bioplastic substrates made from bioplastics instead of glass substrates or PET resin substrates.

[0007] However, conventional technology has not been able to manufacture substrates made of bioplastics that are sufficiently thin, resistant to thermal deformation, and have a smooth surface. In other words, conventional technology has not been able to manufacture bioplastic substrates that possess sufficient properties to be used as substrates for electronic devices.

[0008] This invention has been made in view of the above circumstances, and aims to provide a bioplastic substrate that is sufficiently thin, resistant to deformation by heat, has a smooth surface, and can be suitably used as a substrate for electronic devices, as well as a method for manufacturing the same. Furthermore, the present invention aims to provide an electronic device comprising the bioplastic substrate of the present invention, and an organic thin-film solar cell comprising the bioplastic substrate of the present invention. [Means for solving the problem]

[0009] [1] A bioplastic substrate having a film-like shape containing cellulose acetate propionate resin, with a thickness of 0.1 mm or more and 1.0 mm or less, and a surface roughness (SRa) of 30 nm or less. A bioplastic substrate in which, when a 20 mm square test piece taken from the bioplastic substrate is placed on a horizontal mounting surface and heated at 80°C for 15 minutes, the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface is 0.3 mm or less.

[0010] [2] [1] comprising a bioplastic substrate and an electronic element, An electronic device having an electrode layer formed in contact with the bioplastic substrate. [3] The electronic device according to [2], wherein the electrode layer is made of a material containing a composite of polyethylenedioxythiophene and polystyrene sulfonic acid.

[0011] [4] An organic thin-film solar cell comprising a bioplastic substrate as described in [1], a first electrode formed in contact with the bioplastic substrate, a second electrode, and a photoelectric conversion film disposed between the first electrode and the second electrode. [5] The organic thin-film solar cell according to [4], wherein the first electrode is made of a material containing a composite of polyethylenedioxythiophene and polystyrene sulfonic acid.

[0012] [6] [1] is a method for producing a bioplastic substrate, A surface treatment step is performed by surface treating the first surfaces of a first silicon substrate and a second silicon substrate, each having a surface roughness (SRa) of 20 nm or less, using a surface treatment agent containing a silane coupling agent. A method for manufacturing a bioplastic substrate, comprising: arranging the first surface of the first silicon substrate and the first surface of the second silicon substrate facing each other; sandwiching a film precursor containing the cellulose acetate propionate resin between the first silicon substrate and the second silicon substrate; and a hot press step of heating while applying pressure with the first silicon substrate and the second silicon substrate.

[0013] [7] The method for producing a bioplastic substrate according to [6], wherein in the hot pressing step, the film precursor is heated at a temperature of 180°C or higher while being pressurized at a pressure of 1.0 MPa or higher. [Effects of the Invention]

[0014] The bioplastic substrate of the present invention contains cellulose acetate propionate resin and has a film-like shape with a thickness of 0.1 mm to 1.0 mm and a surface roughness (SRa) of 30 nm or less. Furthermore, when a 20 mm square test piece taken from the bioplastic substrate is placed on a horizontal mounting surface and heated at 80°C for 15 minutes, the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface is 0.3 mm or less.Therefore, the bioplastic substrate of the present invention is sufficiently thin, resistant to deformation by heat, has a smooth surface, and can be suitably used as a substrate for electronic devices.

[0015] Furthermore, the method for manufacturing the bioplastic substrate of the present invention includes a surface treatment step of surface-treating the first surfaces of a first silicon substrate and a second silicon substrate having a surface roughness (SRa) of 20 nm or less using a surface treatment agent containing a silane coupling agent, and a hot-press step of arranging the first surface of the first silicon substrate and the first surface of the second silicon substrate opposite each other, sandwiching a film precursor containing the cellulose acetate propionate resin between the first silicon substrate and the second silicon substrate, and heating while applying pressure with the first silicon substrate and the second silicon substrate.Therefore, the bioplastic substrate of the present invention can be easily manufactured according to the method for manufacturing the bioplastic substrate of the present invention.

[0016] Furthermore, the electronic device of the present invention includes the bioplastic substrate of the present invention and an electronic element, the electronic element having an electrode layer formed in contact with the bioplastic substrate. The bioplastic substrate of the present invention is sufficiently thin, resistant to deformation by heat, and has a smooth surface. For this reason, the electronic device of the present invention, which includes an electronic element having an electrode layer formed in contact with the bioplastic substrate of the present invention, exhibits less deformation due to heat during the formation of the electrode layer, is thin, has sufficient properties, and is preferable from the perspective of the Sustainable Development Goals (SDGs) and environmental protection.

[0017] In addition, the organic thin-film solar cell of the present invention includes a biodegradable plastic substrate of the present invention, a first electrode formed in contact with the biodegradable plastic substrate, a second electrode, and a photoelectric conversion film disposed between the first electrode and the second electrode. Therefore, the organic thin-film solar cell of the present invention has less deformation due to heat when forming the first electrode, is thin in thickness, and has sufficient power generation characteristics.

Brief Description of Drawings

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an organic thin-film solar cell according to the present embodiment.

Embodiments for Carrying Out the Invention

[0019] In order to solve the above problems and realize a biodegradable plastic substrate that can be suitably used as a substrate for electronic devices, the present inventor focused on cellulose acetate propionate resin (hereinafter, may be abbreviated as "CAP resin") and conducted intensive studies as follows. CAP resin is a reaction product of cellulose, acetic acid, and propionic acid, and is a biodegradable plastic that can easily form a transparent film. In addition, a film made of CAP resin has a high glass transition temperature Tg (150 ° C), good heat resistance, and excellent flexibility and processability.

[0020] First, the present inventors used a method (cast molding method) in which a solution obtained by dissolving CAP resin in a solvent is applied onto a substrate, dried, and then peeled off from the substrate to create a CAP resin film made of CAP resin and having a thickness of 0.1 mm or more and 1.0 mm or less, which can be suitably used as a substrate for electronic devices.

[0021] Then, the obtained CAP resin film was heat-treated at a temperature of 80 ° C for 15 minutes by simulating the heat treatment conditions when forming the electrode layer of the electronic device. As a result, the CAP resin film curled and became a cylindrical shape. Therefore, it was found that it could not be used as a substrate for electronic devices.

[0022] Therefore, the inventors investigated the cause of curling of the CAP resin film due to heat treatment. As a result, the inventors concluded that this is due to a large density difference between the first and second surfaces of the CAP resin film. More specifically, it is presumed that a large density difference between the first and second surfaces leads to a large difference in stress between the first and second surfaces generated by heat treatment, causing the CAP resin film to warp and curl.

[0023] Therefore, in order to reduce the density difference between the first and second surfaces of the CAP resin film, the inventors used powder made of CAP resin as a film precursor, sandwiched it between two pressurized substrates made of polyimide (PI) resin, which has good heat resistance, and performed a hot press by heating it while applying pressure in the thickness direction. Then, the CAP resin film obtained after the hot press was subjected to a heat treatment by heating it at a temperature of 80°C for 15 minutes. As a result, it was confirmed that the CAP resin film did not curl.

[0024] Furthermore, we found that even when the first electrode, the photoelectric conversion film, and the second electrode are formed in this order on the CAP resin film obtained after hot pressing, the CAP resin film does not curl, and organic thin-film solar cells can be manufactured without any problems. However, when the photoelectric conversion rate of the obtained organic thin-film solar cell was measured, the photoelectric conversion efficiency (PCE) was low, and sufficient power generation characteristics could not be obtained.

[0025] Therefore, the inventors diligently investigated the cause of insufficient photoelectric conversion rate in organic thin-film solar cells manufactured using a CAP resin film obtained after hot pressing as a substrate. As a result, the inventors found that the cause was the rough surface roughness of the CAP resin film obtained after hot pressing. Therefore, in order to reduce the surface roughness of the CAP resin film obtained after hot pressing, the inventors used a silicon substrate with a good flat surface as the pressurizing substrate and performed hot pressing using powder made of CAP resin as the film precursor.

[0026] However, it was found that when a silicon substrate with good flatness and a surface roughness (SRa) of 20 nm or less is used as the pressurized substrate, it becomes difficult to peel the CAP resin film from the silicon substrate after hot pressing. Therefore, the inventors conducted extensive research to enable easy peeling of the CAP resin film from the silicon substrate after hot pressing.

[0027] As a result, it was found that before sandwiching the film precursor between the two silicon substrates used as the pressurized substrate, the flat surfaces of the two silicon substrates that will come into contact with the CAP resin film after hot pressing should be surface-treated using a surface treatment agent containing a silane coupling agent. In other words, it was found that by placing the flat surfaces of the two silicon substrates that have undergone the above surface treatment facing each other, sandwiching the film precursor between them, and hot-pressing, a CAP resin film with a thickness of 0.1 mm to 1.0 mm, that can be easily peeled off the silicon substrate, and that has a flat surface can be obtained after hot pressing.

[0028] Furthermore, the inventors investigated the relationship between the heat treatment conditions associated with the manufacturing of organic thin-film solar cells and the amount of substrate warping. As a result, they found that if the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface (hereinafter sometimes referred to as "heating warping amount") when a 20 mm square test piece taken from the substrate is placed on a horizontal mounting surface and heated at 80°C for 15 minutes is 0.3 mm or less, then components such as electrode layers for electronic devices can be formed in contact with the substrate without being affected by the warping of the substrate due to heat treatment.

[0029] Furthermore, we confirmed that a bioplastic substrate having a film-like shape containing CAP resin, with a thickness of 0.1 mm to 1.0 mm and a surface roughness (SRa) of 30 nm or less, manufactured by hot pressing using the method described above, exhibits a heating warp of 0.3 mm or less, and thus conceived the present invention.

[0030] The bioplastic substrate, method for manufacturing the bioplastic substrate, electronic device, and organic thin-film solar cell of the present invention will be described in detail below. The scope of the present invention is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the invention. Furthermore, if multiple upper and lower limits are given for a particular parameter, any upper and lower limit can be combined from among these upper and lower limits to obtain a suitable numerical range.

[0031] [Bioplastic substrate] The bioplastic substrate of this embodiment has a film-like shape containing cellulose acetate propionate resin (CAP resin). Because the bioplastic substrate of this embodiment contains CAP resin, it is preferable from the perspective of the Sustainable Development Goals (SDGs) and environmental protection.

[0032] The bioplastic substrate of this embodiment is preferably composed mainly of CAP resin. That is, the bioplastic substrate may contain 50% by mass or more of CAP resin, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The bioplastic substrate of this embodiment may also consist only of CAP resin and unavoidable impurities.

[0033] If the bioplastic substrate of this embodiment contains other materials along with the CAP resin, the other materials can be, for example, a resin other than the CAP resin, a filler, a known additive, etc. Other materials can be used, one or more in amounts that meet the required properties such as transparency (transmittance), strength, and glass transition temperature (Tg) depending on the application of the bioplastic substrate, and do not deviate from the purpose of the present invention.

[0034] The resin other than CAP resin can be any resin that can satisfy the strength, glass transition temperature (Tg), transmittance, and thermoformability characteristics required depending on the application of the bioplastic substrate, and is not particularly limited. Examples of resins other than CAP resin include cellulose resins that are not CAP resins, bio-based plastics that use biomass as a raw material, biodegradable plastics that use biomass as a raw material, and biodegradable plastics that do not use biomass as a raw material.

[0035] Examples of cellulose resins other than CAP resins include those in which one type of acyl group (-COR) is bonded to at least some of the hydrogen atoms of the -OH group of the pyranose ring derived from cellulose, and the number of carbon atoms in the acyl group is between 2 and 10. Specifically, examples include cellulose acetate (CA) resin, in which the acyl group contains 2 carbon atoms; cellulose propionate (CP) resin, in which the acyl group contains 3 carbon atoms; cellulose butyrate (CB) resin, in which the acyl group contains 4 carbon atoms; cellulose hexanoate (CH) resin, in which the acyl group contains 6 carbon atoms; cellulose octanoate (CO) resin, in which the acyl group contains 8 carbon atoms; and cellulose decanoate (CD) resin, in which the acyl group contains 10 carbon atoms.

[0036] Furthermore, examples of cellulose resins other than CAP resins include those in which two or more acyl groups (-COR) are bonded in any proportion to at least some of the hydrogen atoms of the -OH group derived from cellulose, and the number of carbon atoms in the two or more acyl groups is between 2 and 10. Specifically, examples of the above acyl groups include cellulose acetate butyrate (CAB) resin containing -COCH3 with 2 carbon atoms and -COCH2CH2CH3 with 4 carbon atoms, and cellulose acetate hexanoate (CAH) resin containing -COCH3 with 2 carbon atoms and -COCH2CH2CH2CH2CH3 with 6 carbon atoms.

[0037] Examples of bio-based plastics used as resins other than CAP resins include biopolyethylene (PE), biopolypropylene (PP), and biopolyethylene terephthalate (PET). Examples of biodegradable plastics that use biomass as a raw material and are used as resins other than CAP resins include polylactic acid (PLA) and biopolybutylene succinate (PBS). Examples of biodegradable plastics that are not CAP resins and do not use biomass as a raw material include polybutylene succinate (PBS) and polycaprolactone (PCL).

[0038] Examples of fillers include fibers made from organic materials other than CAP resin, such as cellulose nanofibers, chitin nanofibers, and chitosan nanofibers; fibers made from inorganic materials such as inorganic nanofibers; and inorganic nanoparticles. When the bioplastic substrate of this embodiment contains fillers together with the CAP resin, it becomes a bioplastic substrate with excellent strength. Furthermore, when the bioplastic substrate of this embodiment contains fillers together with the CAP resin, it may become a bioplastic substrate with a high glass transition temperature (Tg).

[0039] In this embodiment, it is preferable to use a CAP resin with a number-average molecular weight (Mn) in the range of 30,000 to 300,000 for the bioplastic substrate. A number-average molecular weight (Mn) of 30,000 or more results in a bioplastic substrate with better heat resistance. A number-average molecular weight (Mn) of 50,000 or more is more preferable for the CAP resin. Furthermore, a number-average molecular weight (Mn) of 300,000 or less is preferable because it does not result in excessively high melt viscosity, which would impair thermoformability. A number-average molecular weight (Mn) of 250,000 or less is more preferable for the CAP resin.

[0040] The CAP resin contained in the bioplastic substrate of this embodiment is formed in which -C(=O)CH3 and -C(=O)CH2CH3 are bonded in any proportion to at least some of the hydrogen atoms of the -OH group of the pyranose ring derived from cellulose. The total number of -OC(=O)CH3 and -OC(=O)CH2CH3 bonded to each pyranose ring derived from cellulose in the CAP resin is in the range of 1 to 3. All ring structures derived from the pyranose ring in the CAP resin may have the same number of -OC(=O)CH3 and / or -OC(=O)CH2CH3 bonded to them, or ring structures with different numbers of -OC(=O)CH3 and / or -OC(=O)CH2CH3 bonded to them may be included.

[0041] The bioplastic substrate of this embodiment has a film-like shape with a thickness of 0.1 mm or more and 1.0 mm or less. Since the bioplastic substrate of this embodiment has a thickness of 0.1 mm or more, warping of the substrate due to heat treatment can be effectively suppressed. As a result, the bioplastic substrate of this embodiment can form components such as electrode layers for electronic devices in contact with the substrate, and can be suitably used as a substrate for electronic devices. The thickness of the bioplastic substrate of this embodiment may be 0.2 mm or more, or 0.25 mm or more.

[0042] Furthermore, since the bioplastic substrate of this embodiment has a thickness of 1.0 mm or less, when used as a substrate for an electronic device, for example, it can contribute to the miniaturization and thinning of the electronic device. The thickness of the bioplastic substrate is preferably 0.5 mm or less, and more preferably 0.3 mm or less.

[0043] The bioplastic substrate of this embodiment has a surface roughness (SRa) of 30 nm or less. Therefore, for example, when an electrode layer of an electronic device is formed in contact with the bioplastic of this embodiment, the roughness of the surface does not impair the quality of the electrode layer and the electronic device. For this reason, the bioplastic substrate of this embodiment can be suitably used as a substrate for electronic devices. Furthermore, electronic devices manufactured using the bioplastic substrate of this embodiment will have excellent reliability. The surface roughness (SRa) of the bioplastic substrate is preferably 25 nm or less, and more preferably 20 nm or less.

[0044] Furthermore, the bioplastic substrate of this embodiment preferably has a surface roughness (SRa) of 10 nm or more. This is because, if the surface roughness of the bioplastic substrate of this embodiment is 10 nm or more, it can be easily manufactured using the manufacturing method described later. The surface roughness of the bioplastic substrate is preferably 12 nm or more, and may also be 15 nm or more.

[0045] The surface roughness (SRa) of the bioplastic substrate in this embodiment can be measured, for example, using a micro-shape measuring instrument (ET200A-3D, manufactured by Kosaka Research Institute Co., Ltd.).

[0046] In this embodiment, when a 20mm square test piece taken from the bioplastic substrate is placed on a horizontal mounting surface and heated at 80°C for 15 minutes, the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface (hereinafter sometimes referred to as "heat warp amount") is 0.3mm or less. Therefore, in this embodiment, components such as electrode layers for electronic devices can be formed in contact with the substrate without being affected by warping of the substrate due to heat treatment. As a result, the bioplastic substrate of this embodiment can be suitably used as a substrate for electronic devices.

[0047] The amount of heat warping of the bioplastic substrate is preferably 0.25 mm or less, and more preferably 0.2 mm or less. The amount of heat warping of the bioplastic substrate is preferably 0.1 mm or more, and more preferably 0.15 mm or more, as this allows for the use of thin bioplastic substrates.

[0048] When measuring the amount of heat warping of a bioplastic substrate, the material of the mounting surface on which the test specimen is placed can be, for example, anodized aluminum that forms the heating surface of a hot plate, and is not particularly limited.

[0049] [Method for manufacturing bioplastic substrates] The bioplastic substrate of this embodiment can be manufactured, for example, by the method shown below. First, a first silicon substrate and a second silicon substrate are prepared, with at least the first surface having a surface roughness (SRa) of 20 nm or less. The first surface of the first silicon substrate and the first surface of the second silicon substrate are the surfaces that come into contact with the film precursor, which will later be described as a bioplastic substrate.

[0050] Since the first silicon substrate and the second silicon substrate have a surface roughness (SRa) of 20 nm or less on their first surface, it is possible to manufacture the bioplastic substrate of this embodiment having a surface roughness (SRa) of 30 nm or less. Preferably, the first silicon substrate and the second silicon substrate have a surface roughness of 18 nm or less on their first surface, more preferably 17 nm or less, and even more preferably 15 nm or less. Furthermore, since the first silicon substrate and the second silicon substrate can be easily manufactured, it is preferable that the surface roughness (SRa) of the first surface is 10 nm or more. The surface roughness (SRa) of the first surface of the first silicon substrate and the second silicon substrate may be 12 nm or more.

[0051] The surface roughness of the first surface of the first silicon substrate and the second silicon substrate can be adjusted, for example, by polishing the surface of the silicon substrate using a known polishing method. The surface roughness of the second surface of the first silicon substrate and the second silicon substrate is not particularly limited and may be the same as or different from the surface roughness of the first surface. The surface roughness (SRa) of the first surface of the first silicon substrate and the second silicon substrate can be measured using the same method as the surface roughness (SRa) of the bioplastic substrate described above.

[0052] The size and planar shape of the first and second silicon substrates are not particularly limited and can be appropriately determined according to the size and planar shape of the bioplastic substrate to be manufactured. The planar shape of the first and second silicon substrates is not particularly limited and can be, for example, a circular shape with a diameter of 4 to 8 inches, as this facilitates handling and improves productivity.

[0053] The thickness of the first silicon substrate and the second silicon substrate can be, for example, 0.1 mm or more and 3.0 mm or less. The thickness of the first silicon substrate and the second silicon substrate is preferably 0.5 mm or more, as this provides sufficient strength and prevents damage due to pressure. The thickness of the first silicon substrate and the second silicon substrate is preferably 2.0 mm or less, as this makes them easier to handle.

[0054] For the first and second silicon substrates, for example, known silicon substrates that can be used as substrates for electronic devices may be used, and commercially available ones may also be used. The first silicon substrate and the second silicon substrate may be the same, or they may differ in one or more ways, such as material, planar shape, or thickness.

[0055] Next, the first surface of the first silicon substrate and the first surface of the second silicon substrate are surface-treated using a surface treatment agent (surface treatment step). The surface treatment agent used in the surface treatment process includes a silane coupling agent. The surface treatment agent may contain only one type of silane coupling agent or two or more types. The surface treatment agent may consist only of a silane coupling agent, or it may contain a silane coupling agent along with other components such as water, organic solvents such as toluene, etc. When surface treatment is performed by applying the surface treatment agent, it is preferable to use a surface treatment agent that contains both a silane coupling agent and an organic solvent.

[0056] The silane coupling agent contained in the surface treatment agent reacts with the first surface of the first silicon substrate and the first surface of the second silicon substrate to form chemical bonds, creating a surface treatment layer consisting of a self-assembled monolayer. The surface treatment layer formed on the first surfaces of the first and second silicon substrates has excellent lubricity, making it difficult for the bioplastic substrate formed in the hot-pressing process described later to adhere to it. As a result, in the manufacturing method of this embodiment, the bioplastic substrate formed in the hot-pressing process described later can be easily peeled off from the first and second silicon substrates.

[0057] Silane coupling agents used in surface treatment agents typically have both a functional group and a hydrolyzable group in their molecule. The hydrolyzable groups react with the first silicon substrate and the second silicon substrate. Examples of hydrolyzable groups include methoxy groups (-OCH3) and ethoxy groups (-OCH2CH3). The number of hydrolyzable groups in the silane coupling agent may be one, two, or three. The number of hydrolyzable groups in the silane coupling agent is preferably two or three, and more preferably three, because it results in a surface treatment agent with good reactivity with the first and second silicon substrates. When there are multiple hydrolyzable groups, the multiple hydrolyzable groups may be the same, or some or all of them may be different.

[0058] Examples of functional groups include alkyl groups, fluoroalkyl groups in which some or all of the hydrogen atoms of the alkyl group are substituted with fluorine, and aromatic groups. These functional groups contribute to the lubricity of the surface treatment layer formed by reaction with the first surface of the first silicon substrate and the first surface of the second silicon substrate.

[0059] The alkyl group as a functional group can be, for example, a linear or branched alkyl group having 1 to 20 carbon atoms, preferably a linear or branched alkyl group having 3 to 10 carbon atoms, and more preferably a linear alkyl group having 3 to 10 carbon atoms.

[0060] Furthermore, the fluoroalkyl group as a functional group can be a fluoroalkyl group in which some or all of the hydrogen atoms of the alkyl group as a functional group are substituted with fluorine. Since the fluoroalkyl group as a functional group can form a surface treatment layer with excellent lubricity, it is preferable that it be a perfluoroalkyl group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine.

[0061] Examples of functional groups include perfluorohexyl groups, perfluorooctyl groups, and perfluorodecyl groups.

[0062] Commercially available surface treatment agents may be used. Examples of commercially available surface treatment agents include perfluorodecyltriethoxysilane (FDTS, manufactured by Tokyo Chemical Industry Co., Ltd.).

[0063] Methods for surface-treating the first surface of the first silicon substrate and the first surface of the second silicon substrate using a surface treatment agent include, for example, applying the surface treatment agent to the first surface of the first silicon substrate and the first surface of the second silicon substrate, or heating the surface treatment agent to vaporize it and react it with the first surface of the first silicon substrate and the first surface of the second silicon substrate. Known methods can be used for applying the surface treatment agent. For example, methods such as applying the surface treatment agent to the first silicon substrate and the second silicon substrate using a spray, or immersing the first silicon substrate and the second silicon substrate in the surface treatment agent can be used.

[0064] Next, the first surface of the first silicon substrate, which has undergone surface treatment, and the first surface of the second silicon substrate are placed facing each other. Then, a film precursor is sandwiched between the first and second silicon substrates and heated while applying pressure in the thickness direction (hot press process). The film precursors formed by the first and second silicon substrates can be pressurized and heated, for example, by placing the first and second silicon substrates, which are positioned opposite each other, between two metal plates, and using a known hot press device to pressurize them in the thickness direction at a predetermined pressure through the metal plates while heating them to a predetermined temperature. The metal plates can be made of stainless steel, iron, or the like.

[0065] The film precursor used in the hot pressing process should contain CAP resin and be made of the same material as the target bioplastic substrate. The shape of the film precursor is not particularly limited; for example, it can be in the form of a powder, film, or pellet. However, it is preferable that it be in the form of a powder because it eliminates the need for a film precursor manufacturing process.

[0066] When using a powdered film precursor, the particle size of the film precursor is not particularly limited, but is preferably, for example, 50 μm to 100 μm. When a film precursor is used, for example, it can be manufactured by dissolving a material corresponding to the composition of the film precursor in a solvent, coating a known substrate with the solution, drying it, and then peeling it off the substrate.

[0067] In the hot pressing process, the pressure applied to the film precursor is preferably within the range of 1.0 MPa to 1.2 MPa. A pressure of 1.0 MPa to 1.2 MPa is preferable because it makes it easier to obtain a bioplastic substrate with a surface roughness closer to the surface roughness of the first surface of the surface-treated first silicon substrate and second silicon substrate.

[0068] In the hot pressing process, the temperature at which the film precursor is heated is preferably, for example, 180°C to 300°C, and more preferably 200°C to 230°C. When the temperature at which the film precursor is heated is within the range of 180°C to 230°C, it is easier to obtain a bioplastic substrate having a surface roughness that is closer to the surface roughness of the first surface of the surface-treated first silicon substrate and second silicon substrate, which is preferable.

[0069] In the hot pressing process, the heat treatment time for heating the film precursor under pressure can be, for example, 1 minute or more and 10 minutes or less. The heat treatment time can be appropriately determined depending on the temperature at which the film precursor is heated, the thickness of the target bioplastic substrate, etc. If the heat treatment time is 1 minute or more, the effects of the hot pressing process are effectively realized, and a bioplastic substrate with a surface roughness closer to the surface roughness of the first surface of the surface-treated first silicon substrate and second silicon substrate can be obtained. The heat treatment time is preferably 2 minutes or more. Furthermore, if the heat treatment time is 10 minutes or less, the bioplastic substrate of this embodiment can be manufactured efficiently, resulting in good productivity. The heat treatment time is preferably 5 minutes or less. By performing the above steps, the bioplastic substrate of this embodiment can be obtained.

[0070] [Electronic devices] Next, the electronic device of this embodiment will be described in detail. The electronic device (electronic component) of this embodiment includes the bioplastic substrate and electronic elements of this embodiment. Examples of electronic elements include photoelectric converters, capacitors, transistors, photodetectors, diodes, and rectifiers.

[0071] The electronic elements of the electronic device of this embodiment have an electrode layer formed in contact with the bioplastic substrate of this embodiment. As the electrode layer, known conductive materials used as electrode layers in electronic devices can be used. Examples include materials containing PEDOT:PSS, nanocarbon-based conductive materials, conductive polymers such as polyaniline, metals such as copper, aluminum, silver, and gold, and conductive oxides such as indium-tin composite oxide (ITO) and aluminum-tin composite oxide (AZO).

[0072] When the electronic device of this embodiment is an optical component such as an organic thin-film solar cell, the electrode layer is preferably made of a light-transmitting conductive material. Examples of such conductive materials include materials containing PEDOT:PSS, indium-tin composite oxide (ITO), and nanocarbon-based conductive materials.

[0073] PEDOT:PSS is poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid, and is an organic material consisting of a composite of polyethylenedioxythiophene and polystyrene sulfonic acid. Electrode layers made from materials containing PEDOT:PSS have good conductivity and heat resistance, and excellent flexibility. Moreover, electrode layers made from materials containing PEDOT:PSS can be formed at low temperatures of 80°C or less by the method described later. For this reason, it is particularly preferable that the electrode layer of the electronic device of this embodiment is made from a material containing PEDOT:PSS.

[0074] As the PEDOT:PSS-containing material used as the electrode layer material, one or more types can be selected from, for example, ethylene glycol (EG)-containing PEDOT:PSS, methanol-containing PEDOT:PSS, and dimethyl sulfoxide-added PEDOT:PSS. It is preferable to use ethylene glycol (EG)-containing PEDOT:PSS because it results in an electrode layer with good conductivity.

[0075] As for the ethylene glycol (EG)-containing PEDOT:PSS, it is preferable to use one in which the number of moles of ethylene glycol (EG) per mole of PEDOT:PSS is in the range of 0.001 moles to 10 moles. It is even more preferable to use one in the range of 0.003 moles to 1 mole, as this allows for the formation of an electrode layer with even better conductivity.

[0076] The PEDOT:PSS-containing material used as the electrode layer material may contain one or more additives. Examples of additives include surfactants such as fluorosurfactants (Zonyl®; FS-31, manufactured by Safic-Alcan) and Triton-X (manufactured by Sigma-Aldrich). These may also be included in the PEDOT:PSS-containing material. As the surfactant, it is preferable to use a fluorosurfactant because it provides an electrode layer with good conductivity. Furthermore, the PEDOT:PSS-containing material used as the electrode layer material may contain a solvent such as methanol, if necessary.

[0077] [Manufacturing methods for electronic devices] The electronic device of this embodiment can be manufactured by the method described below. First, an electrode layer for an electronic element is formed on the bioplastic substrate of this embodiment using a known method corresponding to the material of the electrode layer for the electronic element. For example, if the electrode layer is made of indium-tin composite oxide (ITO), it can be formed using methods such as sputtering or sol-gel deposition.

[0078] Furthermore, if the electrode layer is made of a material containing PEDOT:PSS, it can be manufactured, for example, by the following method. First, a PEDOT:PSS-containing material, such as ethylene glycol (EG)-containing PEDOT:PSS, and additives such as surfactants, which may be added as needed, are dispersed in a solvent containing water at a predetermined concentration to prepare a PEDOT / PSS dispersion. A commercially available PEDOT:PSS-containing material may be used as the raw material for the PEDOT / PSS dispersion.

[0079] Next, the PEDOT / PSS dispersion is applied to the bioplastic substrate of this embodiment to form a coating film. Known methods for applying the PEDOT / PSS dispersion include, for example, spin coating, immersion, various dispensing methods, spraying, inkjet, die coating, spray coating, roll coater, screen printing, flexographic printing, and other screen printing methods.

[0080] Next, the bioplastic substrate with the coating film is heat-treated to remove the solvent from the coating film and form a PEDOT / PSS film. As a method for heating the bioplastic substrate on which the coating film has been formed, known methods such as using a hot plate or a heating chamber can be used. The atmosphere used when heat-treating a bioplastic substrate with a coating is not particularly limited and can be an air atmosphere.

[0081] The temperature at which the coated bioplastic substrate is heated is preferably between 60°C and 100°C. A heat treatment temperature of 60°C or higher allows for efficient formation of an electrode layer made of a material containing PEDOT / PSS. A heat treatment temperature of 70°C or higher is preferable. Furthermore, a heat treatment temperature of 100°C or lower prevents warping of the bioplastic substrate in this embodiment due to the heat treatment. A heat treatment temperature of 90°C or lower is preferable.

[0082] The heat treatment time can be, for example, 3 minutes or more and 30 minutes or less. The heat treatment time can be appropriately determined according to the heat treatment temperature, the concentration of PEDOT / PSS in the PEDOT / PSS dispersion, the composition of the PEDOT / PSS dispersion, the thickness of the coating film, etc. If the heat treatment time is 3 minutes or more, water in the coating film can be removed at a lower heat treatment temperature. Therefore, it is possible to effectively prevent warping of the bioplastic substrate due to heat treatment. A heat treatment time of 5 minutes or more is preferable. Also, if the heat treatment time is 30 minutes or less, an electrode layer made of PEDOT / PSS film can be efficiently formed. A heat treatment time of 20 minutes or less is preferable.

[0083] In this embodiment, the electrode layer may be manufactured by performing the step of applying a PEDOT / PSS dispersion to form a coating film, removing the solvent by heat treatment, and forming a PEDOT / PSS film only once. Alternatively, after forming the PEDOT / PSS film, the above step of forming the PEDOT / PSS film may be repeated one or more times to form an electrode layer consisting of a PEDOT / PSS film of a predetermined thickness. When the above step of forming the PEDOT / PSS film is repeated one or more times after the initial PEDOT / PSS film formation, the coating film formation method and conditions, the heat treatment method and conditions, etc., may be the same throughout, or they may differ in some parts or each time.

[0084] In this embodiment, an electrode layer for an electronic element is formed in contact with the bioplastic substrate of this embodiment. Then, each component that will become the electronic element is formed on the bioplastic substrate with the electrode layer using a known method corresponding to the type of electronic element. This yields the electronic device of this embodiment.

[0085] The electronic device of this embodiment includes a bioplastic substrate and an electronic element, the electronic element having an electrode layer formed in contact with the bioplastic substrate. The bioplastic substrate of this embodiment is sufficiently thin, resistant to thermal deformation, and has a smooth surface. Therefore, the electronic device of this embodiment having an electrode layer formed in contact with the bioplastic substrate has minimal thermal deformation during the formation of the electrode layer, is thin, and possesses sufficient properties.

[0086] [Organic thin film solar cell] Next, the organic thin-film solar cell of this embodiment will be described in detail with reference to the drawings. Figure 1 is a schematic cross-sectional view showing an example of an organic thin-film solar cell according to this embodiment. As shown in Figure 1, the organic thin-film solar cell 10 of this embodiment has a plate-like shape and includes a substrate 1, a first electrode 2a formed in contact with the substrate 1, a second electrode 2b, and a photoelectric conversion film 3 disposed between the first electrode 2a and the second electrode 2b.

[0087] The organic thin-film solar cell 10 shown in Figure 1 is a preferred example of the electronic device of this embodiment. Specifically, the organic thin-film solar cell 10 includes a substrate 1 made of a bioplastic substrate of this embodiment and a photoelectric conversion element which is an electronic element. The photoelectric conversion element in the organic thin-film solar cell 10 includes a first electrode 2a, a photoelectric conversion film 3, and a second electrode 2b. The first electrode 2a included in the photoelectric conversion element of the organic thin-film solar cell 10 is an electrode layer formed in contact with the substrate 1 (the bioplastic substrate of this embodiment). Therefore, in this embodiment, the explanation of the substrate 1 and the first electrode 2a in the organic thin-film solar cell 10 shown in Figure 1 will be omitted.

[0088] In this embodiment, it is preferable that the photoelectric conversion element of the organic thin-film solar cell 10 is made only of organic materials and does not contain inorganic compounds such as metal materials. This is because, for example, compared to a case in which the photoelectric conversion element includes metal materials, the organic thin-film solar cell 10 is easier to recycle, which is preferable from the standpoint of the Sustainable Development Goals (SDGs) and environmental protection.

[0089] [Photoelectric conversion film] In the organic thin-film solar cell 10 of this embodiment, the photoelectric conversion film 3 can include, for example, an electron-donating material that functions as an electron donor and an electron-accepting material that functions as an electron acceptor. The electron-donating material and electron-accepting material included in the photoelectric conversion film 3 may be one type each, or two or more types each.

[0090] In this embodiment, as a preferred example of the photoelectric conversion film 3, we will describe the case in which the photoelectric conversion film 3 has a bulk heterojunction structure in which an electron-donating material and an electron-accepting material are mixed in a phase-separated state. When the photoelectric conversion film 3 has a bulk heterojunction structure, the organic thin-film solar cell 10 of this embodiment, including the photoelectric conversion film 3, has a high energy conversion efficiency, which is preferable.

[0091] The structure of the photoelectric conversion film 3 is not limited to a bulk heterojunction structure. The structure of the photoelectric conversion film 3 may be, for example, a single-layer type, a pn heterojunction, or a mutual penetration type junction. When the structure of the photoelectric conversion film 3 is a pn heterojunction, for example, it may consist of a layer containing an electron-donating material and a layer containing an electron-accepting material stacked on top of each other.

[0092] As the electron-donating material that functions as an electron donor in the photoelectric conversion film 3 of this embodiment, known electron-donating materials can be used. Examples of electron-donating materials include poly(3-hexylthiophene-2,5-diyl)(P3HT) represented by the following formula (23), PCE10 represented by the following formula (22), poly((6,7-difluoro((2-hexyldecyl)oxy)-5,8-quinoxalinidyl)2,5-thiophenegyl)), and poly((2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophenyl)-benzo[1,2-b:4,5-b'))-5,5'-(5,8-bis(4-(2-butyloctyl)thiophenyl)dithienobenzothiadiazole).

[0093] [ka] (In equation (23), m is an integer representing the repeating unit.)

[0094] [ka] (In equation (22), n is an integer representing the repeating unit. Bu represents -CH2CH2CH2CH3. Et represents -CH2CH3.)

[0095] As the electron-accepting material that functions as an electron acceptor in the photoelectric conversion film 3 of this embodiment, a known material that accepts electrons donated from an electron-donating material can be used. The electron-accepting material can be a compound different from the electron-donating material in the photoelectric conversion film 3 of this embodiment, for example, phenyl C represented by the following formula (21). 61 Examples include methyl butyrate (PCBM), 2,2'-((2Z,2Z'-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydrothiazolothienothienopyrrolothienothienoindole-2,10-diyl)bis(metallinylidene)bis(5,6-difluoro-3-oxo-2,3-dihydroindene-2,1-diylidene)dimanolonitrile, etc.

[0096] [ka]

[0097] In this embodiment, the photoelectric conversion film 3 contains P3HT represented by formula (23) as the electron-donating material and phenyl C represented by formula (21) as the electron-accepting material. 61 It is preferable to include methyl butyrate (PCBM). This is because an organic thin-film solar cell 10 containing it has high energy conversion efficiency. The ratio of electron-donating material to electron-accepting material contained in the photoelectric conversion film 3 is preferably such that, for example, it contains 0.5 to 2 moles of electron-accepting material for every 1 mole of electron-donating material, and can be appropriately determined depending on the type of electron-donating material and the type of electron-accepting material.

[0098] The photoelectric conversion film 3 of this embodiment may include not only an electron-donating material and an electron-accepting material, but also other known materials as needed. If the photoelectric conversion film 3 of this embodiment includes materials other than the electron-donating material and the electron-accepting material, the proportion of the materials other than the electron-donating material and the electron-accepting material included in the photoelectric conversion film 3 is preferably 0.1% to 10% by mass, and more preferably 1% to 5% by mass.

[0099] If the photoelectric conversion film 3 has a bulk heterojunction structure, it can be manufactured, for example, by the method shown below. First, an electron-accepting material, an electron-donating material, and other materials as needed are dissolved in a solvent using a known method to prepare a coating (solution) for a photoelectric conversion film. As solvents that can be used as materials for photoelectric conversion film coatings, for example, one or more selected from chloroform, 1,8-diiodooctane, diphenyl ether, 1,2-dibromobenzene, chloronaphthalene, etc., can be used.

[0100] Next, the coating for the photoelectric conversion film is applied to the surface of the photoelectric conversion film 3 to form a coating film. Known methods can be used to apply the coating for the photoelectric conversion film. Specifically, examples of methods for applying the coating for the photoelectric conversion film include immersion method, inkjet method, dip coat method, die coat method, spray coat method, spin coat method, roll coater method, screen printing method, flexographic printing method, and screen printing method.

[0101] Next, the coating film formed on the surface of the photoelectric conversion film 3 is dried by a known method to remove the solvent contained in the coating film. Through these steps, a photoelectric conversion film 3 consisting of a thin film is obtained. The photoelectric conversion film 3 of this embodiment can be suitably used as the photoelectric conversion film 3 of an organic thin-film solar cell 10 without performing heat treatment after removing the solvent contained in the coating film. Therefore, it is possible to prevent warping from occurring in the substrate 1 made of the bioplastic substrate of this embodiment due to heat treatment.

[0102] [Second electrode] The second electrode 2b functions as a cathode. The second electrode 2b can be made of, for example, a known conductive material such as a metal like silver or aluminum, or a carbon nanotube (CNT).

[0103] The second electrode 2b can be formed by known methods. If the second electrode 2b is made of a metal such as silver or aluminum, it can be formed using methods such as sputtering, vapor deposition, or coating with an ink containing dispersed metal particles. If the second electrode 2b is made of carbon nanotubes (CNTs), it can be formed, for example, by attaching a encapsulating material integrated with the second electrode 2b, as described later.

[0104] [Hole transport layer] In the organic thin-film solar cell 10 of this embodiment, a hole transport layer (not shown) may be provided between the first electrode 2a and the photoelectric conversion film 3. As the hole transport layer, known materials such as molybdenum oxide (MoO3) and materials containing PEDOT:PSS can be used. Among these, the hole transport layer is preferably made of a material containing PEDOT:PSS because it is an organic material that can form a hole transport layer with good flexibility.

[0105] As the PEDOT:PSS-containing material used as the material for the hole transport layer, commercially available PEDOT:PSS-containing materials may be used. Examples of commercially available PEDOT:PSS-containing materials include Clevios PH1000 (Heraeus), Clevios AL4083 (Heraeus), and Clevios PH-510 (Heraeus). Only one type of PEDOT:PSS-containing material may be used as the material for the hole transport layer, or two or more types may be used.

[0106] A known method can be used to form the hole transport layer, and this method can be appropriately determined depending on the material of the hole transport layer. If the hole transport layer is made of a material containing PEDOT:PSS, the hole transport layer can be manufactured using the same method as when forming the first electrode 2a made of PEDOT:PSS.

[0107] [Electron transport layer] In the organic thin-film solar cell 10 of this embodiment, an electron transport layer (not shown) may be provided between the second electrode 2b and the photoelectric conversion film 3. As the electron transport layer, known materials such as N,N'-bis{3-[3-(dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic acid diimide (PDINN) and zinc oxide (ZnO) can be used. Furthermore, known methods can be used to form the electron transport layer, and these can be appropriately determined depending on the material of the electron transport layer.

[0108] [Sealing layer] The organic thin-film solar cell 10 of this embodiment may have a sealing layer (not shown) on the second electrode 2b. As the sealing layer, for example, a known resin such as polyethylene terephthalate (PET) resin can be used. The sealing layer may consist of only one layer, or it may have a laminated structure in which multiple layers are stacked.

[0109] The sealing layer can be manufactured by known methods. For example, it can be formed by applying a solution of resin dissolved in a solvent onto the second electrode 2b and drying it, or by preparing a sealing material integrated with the second electrode 2b and attaching it by heat and pressure. When forming the sealing layer using the method of attaching a sealing material integrated with the second electrode 2b, damage to the substrate 1 on which each layer up to the second electrode 2b is formed, caused by the formation of the second electrode 2b, can be suppressed, which is preferable.

[0110] The organic thin-film solar cell 10 of this embodiment, shown in Figure 1, includes a substrate 1 made of a bioplastic substrate of this embodiment, a first electrode 2a formed in contact with the substrate 1, a second electrode 2b, and a photoelectric conversion film 3 disposed between the first electrode 2a and the second electrode 2b. Therefore, the organic thin-film solar cell 10 of this embodiment exhibits minimal thermal deformation during the formation of the first electrode 2a, the photoelectric conversion film 3, and the second electrode 2b, resulting in a thin profile and sufficient performance.

[0111] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. [Examples]

[0112] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0113] (Example 1) [Manufacturing of bioplastic substrates] First, two silicon substrates were prepared as the first and second silicon substrates: a circular substrate with a thickness of 0.5 mm, a diameter of 4 inches, and a surface roughness (SRa) of 10 nm on both sides (product name: Si 4inch Wafer, manufactured by ELECTRONICS AND MATERIALS CORPORATION LIMITED).

[0114] Then, the surfaces of both sides of the two silicon substrates were each treated with a surface treatment agent (surface treatment process). As the surface treatment agent, a toluene solution containing 0.05 mmol% of perfluorodecyltriethoxysilane (FDTS, trade name; 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.)) was used. The surface treatment method involved immersion in a toluene solution of the silane coupling agent.

[0115] Next, two surface-treated silicon substrates were placed facing each other and positioned between two 1mm thick stainless steel plates. Then, 10g of a film precursor, which is a powder made of CAP resin (product name: CAP-482-20; number average molecular weight (Mn) 75,000; manufactured by Sigma-Aldrich), was sandwiched between the two silicon substrates. Subsequently, the substrates were heated at 210°C for 3 minutes using a hot press device (IMD-180C; manufactured by Imoto Seisakusho Co., Ltd.) while applying pressure of 1.2 MPa in the thickness direction through the stainless steel plates (hot press process). Through the above process, a bioplastic substrate of Example 1 was obtained, which has a circular shape with a diameter of 4 inches, a thickness of 0.1 mm, and a surface roughness of 19 nm on one side, forming a film-like structure.

[0116] The amount of warping due to heating was measured for the bioplastic substrate of Example 1 using the method described below. Specifically, a 20 mm square test piece was taken from the bioplastic substrate. The test piece was then placed on the horizontal mounting surface, which is the heating surface of a hot plate made of anodized aluminum, and heated at a temperature of 80°C for 15 minutes. Subsequently, the maximum distance between the mounting surface and the opposing surface of the test specimen (measurement of heat warping) was measured. The result was 0.1 mm or less.

[0117] [Manufacturing of organic thin-film solar cells] (Formation of the first electrode) The bioplastic substrate from Example 1 was washed with distilled water and then treated with ultraviolet ozone for 30 minutes using an ultraviolet ozone chamber. Subsequently, a first electrode was formed in contact with one surface of the bioplastic substrate using the method described below, and on the first electrode, the following layers were formed in this order: a hole transport layer, a photoelectric conversion film, an electron transport layer, a second electrode, and a sealing layer.

[0118] First, a PEDOT:PSS dispersion was prepared by dispersing a material containing PEDOT:PSS in water using the method described below. Specifically, an aqueous dispersion of PEDOT:PSS (Clevios PH1000; manufactured by Heraeus) was mixed with 6 vol% ethylene glycol (EG) (manufactured by Kanto Chemical Co., Ltd.), 0.5 vol% fluorosurfactant as an additive (Zonyl®; FS-31, manufactured by Safic-Alcan), and 6 vol% methanol as a solvent to prepare a PEDOT:PSS dispersion in which the number of moles of ethylene glycol per mole of PEDOT:PSS was 0.005 moles.

[0119] Next, the PEDOT / PSS dispersion was applied to a bioplastic substrate by spin coating at a rotation speed of 1500 rpm for 60 seconds to form a coating film. Next, the bioplastic substrate with the coating film was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. This formed a PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS.

[0120] Furthermore, a second coating layer was formed on the EG-containing PEDOT / PSS film obtained after heat treatment by spin coating under conditions of 2000 rpm and 60 seconds. Next, the bioplastic substrate with the second coating film was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. This formed a second PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS.

[0121] Furthermore, a third coating layer was formed on the EG-containing PEDOT / PSS film obtained after the second heat treatment by spin coating under conditions of 2000 rpm and 60 seconds. Next, the bioplastic substrate with the third coating film was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. This formed a third PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS. By performing the above steps, a first electrode with a thickness of 100 nm, made of EG-containing PEDOT:PSS, was formed in contact with the bioplastic substrate.

[0122] (Formation of hole transport layer) First, we prepared a PEDOT:PSS dispersion (product name Clevios AL4083; manufactured by Heraeus). Next, the PEDOT / PSS dispersion was applied to the first electrode formed on the bioplastic substrate by spin coating under conditions of 2000 rpm and 30 seconds to form a coating film, which was then dried in air. Subsequently, another coating film was applied to the coating film formed on the first electrode by spin coating under conditions of 2000 rpm and 30 seconds to form a coating film.

[0123] Next, the bioplastic substrate with the coating film formed on the first electrode was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. As a result, a 100 nm thick hole transport layer made of a PEDOT / PSS film was formed on the first electrode formed on the bioplastic substrate.

[0124] (Formation of photoelectric conversion film) P3HT, represented by formula (23), as an electron-accepting material, and phenyl C, represented by formula (21), as an electron-donating material. 61 A mixture containing methyl butyrate (PCBM) in a molar ratio (electron acceptor material: electron donor material) of 1 mole:1.2 moles was dissolved in chloroform as a solvent. This resulted in a total content of 26 mg / mL of electron acceptor and electron donor material. -1 A coating (solution) for photoelectric conversion films was obtained.

[0125] Next, a coating for photoelectric conversion films was applied to a hole transport layer formed on a bioplastic substrate using a spin-coating method at a rotation speed of 4000 rpm for 30 seconds to form a coating film, which was then dried in air. This allowed a photoelectric conversion film to be formed on a hole transport layer created on a bioplastic substrate.

[0126] (Formation of electron transport layer) N,N'-bis{3-[3-(dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic acid diimide (PDINN) (manufactured by Derthon) was dissolved in methanol to prepare a PDINN solution containing 50 mg / ml of PDINN.

[0127] Next, the PDINN solution was applied to the photoelectric conversion film formed on the bioplastic substrate by spin coating under conditions of 4000 rpm and 30 seconds, forming a coating film, which was then dried in air. This allowed for the formation of an electron transport layer on a photoelectric conversion film formed on a bioplastic substrate.

[0128] (Formation of the second electrode and sealing layer) Next, a encapsulating material integrated with the second electrode is placed on the electron transport layer formed on the bioplastic substrate, with the second electrode facing the electron transport layer, at a temperature of 80°C and a pressure of 0.1 N / cm². 2Under these conditions, the electrodes were heat-pressed and attached for 2 minutes and 30 seconds. This formed the second electrode and the sealing layer on the electron transport layer formed on the bioplastic substrate.

[0129] The sealing material integrated with the electrode layer was manufactured by the method described below. First, a carbon nanotube aqueous dispersion containing carbon nanotubes was prepared at a concentration of 0.2% by mass. Next, a coating film was formed by applying the carbon nanotube aqueous dispersion onto the resin layer of a sealing material (VERREAL; manufactured by Reiko Co., Ltd.) containing a polyethylene terephthalate (PET) resin layer. The carbon nanotube aqueous dispersion was applied by spin coating at a rotation speed of 1000 rpm for 120 seconds.

[0130] The coating film containing carbon nanotubes obtained in this manner was dried by heat treatment at 40°C for 15 minutes. Next, the encapsulant with the dried carbon nanotube coating film was immersed in water for 30 minutes. After that, the encapsulant with the carbon nanotube coating film was removed from the water and dried in air at room temperature (25°C). This formed a encapsulant integrated with an electrode layer made of carbon nanotubes. The organic thin-film solar cell of Example 1 was obtained through the above process.

[0131] (Comparative Example 1) [Manufacturing of organic thin-film solar cells] (Formation of the first electrode) A substrate made of polyethylene terephthalate (PET) resin (PET resin substrate) (manufactured by Reikosha Co., Ltd.) was prepared, having a circular shape with a diameter of 4 inches, a thickness of 0.1 mm, and a surface roughness of 19 nm on the side where the first electrode is formed.

[0132] The PET resin substrate described above was washed with distilled water and then treated with ultraviolet ozone for 30 minutes using an ultraviolet ozone chamber. Subsequently, a first electrode was formed in contact with one surface of the PET resin substrate using the method described below, and on the first electrode, the following layers were formed in this order: a hole transport layer, a photoelectric conversion film, an electron transport layer, a second electrode, and a sealing layer.

[0133] First, a PEDOT:PSS dispersion was prepared in the same manner as in Example 1. Next, the PEDOT / PSS dispersion was applied to a PET resin substrate by spin coating under conditions of 1500 rpm and 60 seconds to form a coating film. Next, the PET resin substrate with the coating was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating. This formed a PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS.

[0134] Furthermore, a second coating layer was formed on the EG-containing PEDOT / PSS film obtained after heat treatment by spin coating under conditions of 2000 rpm and 60 seconds. Next, the PET resin substrate with the second coating film was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. This formed a second PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS. By performing the above steps, a first electrode with a thickness of 100 nm, made of EG-containing PEDOT:PSS, was formed in contact with the PET resin substrate.

[0135] (Formation of hole transport layer) First, as in Example 1, a PEDOT:PSS dispersion (product name Clevios AL4083; manufactured by Heraeus) was prepared. Next, the PEDOT / PSS dispersion was applied to the first electrode formed on the PET resin substrate by spin coating under conditions of 700 rpm and 30 seconds to form a coating film.

[0136] Next, the PET resin substrate with the coating film formed on the first electrode was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. As a result, a 30 nm thick hole transport layer made of a PEDOT / PSS film was formed on the first electrode formed on the PET resin substrate. Subsequently, a photoelectric conversion film, an electron transport layer, a second electrode, and a sealing layer were formed in the same order as in Example 1 on the hole transport layer of the PET resin substrate to obtain the organic thin-film solar cell of Comparative Example 1.

[0137] (Comparative Example 2) [Manufacturing of organic thin-film solar cells] (Formation of the first electrode) A glass substrate (manufactured by Corning) was prepared, which is a square with sides of 2 centimeters, a thickness of 0.1 mm, and a surface roughness of 10 nm on the side where the first electrode is formed.

[0138] The glass substrate described above was cleaned by immersing it in isopropyl alcohol, ultrasonically treating it, and then boiling it with distilled water. The cleaned glass substrate was then subjected to ultraviolet ozone treatment for 30 minutes using an ultraviolet ozone chamber. Subsequently, a first electrode was formed in contact with one surface of the glass substrate using the method described below, and on the first electrode, the following layers were formed in this order: a hole transport layer, a photoelectric conversion film, an electron transport layer, a second electrode, and a sealing layer.

[0139] First, a PEDOT:PSS dispersion was prepared in the same manner as in Example 1. Next, the PEDOT / PSS dispersion was applied to a glass substrate by spin coating under conditions of 2000 rpm and 60 seconds to form a coating film. Next, the glass substrate on which the coating film was formed was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film.

[0140] Furthermore, a second coating layer was formed on the EG-containing PEDOT / PSS film obtained after heat treatment by spin coating under conditions of 3500 rpm and 60 seconds. Next, the glass substrate on which the second coating layer was formed was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating layer. This formed a second PEDOT / PSS film consisting of ethylene glycol (EG)-containing PEDOT:PSS. By performing the above steps, a first electrode with a thickness of 100 nm, made of EG-containing PEDOT:PSS, was formed in contact with the glass substrate.

[0141] (Formation of hole transport layer) First, as in Example 1, a PEDOT:PSS dispersion (product name Clevios AL4083; manufactured by Heraeus) was prepared. Next, the PEDOT / PSS dispersion was applied to the first electrode formed on the glass substrate by spin coating under conditions of 2000 rpm and 30 seconds to form a coating film.

[0142] Next, the glass substrate on which the coating film was formed was heat-treated using a hot plate in an air atmosphere at 80°C for 15 minutes to remove the solvent from the coating film. As a result, a 30 nm thick hole transport layer made of a PEDOT / PSS film was formed on the first electrode formed on the glass substrate. Subsequently, a photoelectric conversion film, an electron transport layer, a second electrode, and a sealing layer were formed in the same order as in Example 1 on the hole transport layer of the PET resin substrate to obtain the organic thin-film solar cell of Comparative Example 2.

[0143] [Calculation of Photoelectric Conversion Efficiency (PCE)] For each of the organic thin-film solar cells obtained in Example 1, Comparative Example 1, and Comparative Example 2, simulated sunlight was irradiated using a solar simulator (product name: XES-40S1, manufactured by Sanei Electric Works Co., Ltd.), and the current flowing during the light irradiation was measured while applying voltage using an IV meter (product name: ADCMAT6242, manufactured by ADC Corporation).

[0144] Based on the above measurement results, the photoelectric conversion efficiency (PCE) of the organic thin-film solar cell in Example 1 was calculated to be 8.6%. In contrast, the photoelectric conversion efficiency (PCE) of the organic thin-film solar cell of Comparative Example 1, which was manufactured using a PET resin substrate, was 8.7%. Furthermore, the photoelectric conversion efficiency (PCE) of the organic thin-film solar cell of Comparative Example 2, which was manufactured using a glass substrate, was 9.7%. These results confirm that the organic thin-film solar cell of Example 1, manufactured using a bioplastic substrate, can achieve power generation characteristics equivalent to those of the organic thin-film solar cell of Comparative Example 1, manufactured using a PET resin substrate. [Explanation of symbols]

[0145] 10... Organic thin film solar cell, 1... Substrate, 2a... First electrode, 2b... Second electrode, 3... Photoelectric conversion film.

Claims

1. A bioplastic substrate having a film-like shape containing cellulose acetate propionate resin, with a thickness of 0.1 mm to 1.0 mm and a surface roughness (SRa) of 30 nm or less. A bioplastic substrate in which a square test piece with sides of 20 mm, taken from the bioplastic substrate, is placed on a horizontal mounting surface and heated at a temperature of 80°C for 15 minutes, and the maximum distance between the mounting surface and the surface of the test piece facing the mounting surface is 0.3 mm or less.

2. The bioplastic substrate described in claim 1 and an electronic element are included. An electronic device having an electrode layer formed in contact with the bioplastic substrate.

3. The electronic device according to claim 2, wherein the electrode layer is made of a material containing a composite of polyethylenedioxythiophene and polystyrene sulfonic acid.

4. An organic thin-film solar cell comprising a bioplastic substrate according to claim 1, a first electrode formed in contact with the bioplastic substrate, a second electrode, and a photoelectric conversion film disposed between the first electrode and the second electrode.

5. The organic thin-film solar cell according to claim 4, wherein the first electrode is made of a material containing a composite of polyethylenedioxythiophene and polystyrene sulfonic acid.

6. A method for producing a bioplastic substrate according to claim 1, A surface treatment step is performed by surface treating the first surfaces of a first silicon substrate and a second silicon substrate, each having a surface roughness (SRa) of 20 nm or less, using a surface treatment agent containing a silane coupling agent. A method for manufacturing a bioplastic substrate, comprising: arranging the first surface of the first silicon substrate and the first surface of the second silicon substrate facing each other; sandwiching a film precursor containing the cellulose acetate propionate resin between the first silicon substrate and the second silicon substrate; and a hot press step of heating while applying pressure with the first silicon substrate and the second silicon substrate.

7. The method for producing a bioplastic substrate according to claim 6, wherein in the hot pressing step, the film precursor is heated at a temperature of 180°C or higher while being pressurized at a pressure of 1.0 MPa or higher.

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