Photoelectric conversion element

Abstract

This invention provides a photoelectric conversion element exhibiting excellent photoelectric conversion efficiency and easy to manufacture, and a method for manufacturing the same. The photoelectric conversion element (100) sequentially comprises a light-transmitting substrate (1), a transparent conductive film (2), a first conductive layer (5) composed of a substrate layer (3) and a porous semiconductor layer (4), a power generation layer (6), and a second conductive layer (8). The second conductive layer (8) is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes.

Description

Technical Field

[0001] This invention relates to photoelectric conversion elements and their manufacturing methods. Background Technology

[0002] Solar cells, as photoelectric conversion devices that convert light energy into electrical energy, have attracted much attention. There are various types of solar cells, such as perovskite solar cells that use perovskite compounds as the power-generating layer. In recent years, a great deal of research has been conducted to improve the photoelectric conversion efficiency of solar cells.

[0003] For example, Patent Document 1 proposes a solar cell with a composite self-supporting film, wherein the composite self-supporting film is a flexible composite self-supporting film having a flexible structure retention layer containing fibrous and / or nanotube structural materials, and a semiconductor layer formed on the surface of the structure retention layer.

[0004] Furthermore, Patent Document 2 proposes a solid-state bonding type photoelectric conversion element, which sequentially comprises a substrate, a first conductive layer, and a conductive material containing a perovskite layer, wherein the conductive material has self-supporting properties.

[0005] In addition, a perovskite solar cell is proposed in Non-Patent Document 1, which is formed by having a single layer of carbon nanotubes with a thickness of about 100 nm on a perovskite film.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-185836;

[0009] Patent document 2: International Publication No. 2017 / 142074.

[0010] Non-patent literature

[0011] Non-patent literature 1: Sakaguchi et al., “Non-doped and unsorted single-walled carbon nanotubes as carrier-selective, transparent, and conductive electrode for perovskite solar cells”, MRS Communications (2018), Vol. 8, pp. 1058-1063, Materials Research Society, 2018. Summary of the Invention

[0012] The problem the invention aims to solve

[0013] However, there is still room for improvement in terms of the excellent photoelectric conversion efficiency and ease of manufacturing of conventional photoelectric conversion elements.

[0014] Therefore, the object of the present invention is to provide a photoelectric conversion element that exhibits excellent photoelectric conversion efficiency and is easy to manufacture, as well as a method for manufacturing the photoelectric conversion element.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research with the aim of solving the above-mentioned problems. Then, the inventors discovered that by setting a porous self-supporting sheet containing at least a single layer of carbon nanotubes on the power generation layer of the photoelectric conversion element, the porous self-supporting sheet can function as a hole transport layer and as a current collector electrode, thereby enabling the resulting photoelectric conversion element to exhibit excellent photoelectric conversion efficiency and be easy to manufacture, thus completing the present invention.

[0017] In other words, the object of the present invention is to advantageously solve the above-mentioned problems. The photoelectric conversion element of the present invention is characterized by being integrally formed of a laminate having a transparent substrate, a transparent conductive film, a first conductive layer, a power generation layer, and a second conductive layer in sequence, wherein the second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes. By making the photoelectric conversion element integrally formed of a laminate having a transparent substrate, a transparent conductive film, a first conductive layer, a power generation layer, and a second conductive layer in sequence, wherein the second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes, a photoelectric conversion element exhibiting excellent photoelectric conversion efficiency and easy to manufacture can be provided.

[0018] It should be noted that in this invention, "porous self-supporting sheet" refers to a sheet with multiple fine pores, and a sheet that maintains its sheet shape even without a support. Regarding the porous self-supporting sheet used in this invention, after immersing the porous self-supporting sheet in a specified solution and then lifting it, even when the porous self-supporting sheet is adhered to the substrate, no breakage or other damage occurs, and its sheet shape is maintained. Furthermore, regarding the porous self-supporting sheet used in this invention, for example, when chlorobenzene, which is a poor solvent for perovskite compounds, is dropped onto the sheet, or when it is processed using a clamp for adhering the sheet, no breakage or deformation occurs. Moreover, the porous self-supporting sheet used in this invention preferably has, for example, a film thickness of 1 μm to 200 μm and an area of ​​1 mm². 2 ~100cm 2 The dimensions are such that the shape is maintained as a sheet without any support.

[0019] In this invention, the photoelectric conversion element may also have a bonding layer at least in a portion between the power generation layer and the second conductive layer. This bonding layer is composed of an organic material A and has a different composition and properties than the power generation layer and the second conductive layer. By integrating the photoelectric conversion element into a laminate comprising a transparent substrate, a transparent conductive film, a first conductive layer, a power generation layer, and a second conductive layer in sequence, wherein the second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes, and a bonding layer is present in at least a portion between the power generation layer and the second conductive layer, and the bonding layer is composed of an organic material A and has a different composition and properties than the power generation layer and the second conductive layer, a photoelectric conversion element exhibiting excellent photoelectric conversion efficiency and easy to manufacture can be provided.

[0020] Furthermore, in the photoelectric conversion element of the present invention, the porous self-supporting sheet may also contain the organic material A. If the porous self-supporting sheet contains the organic material A, the charge transfer between the power generation layer and the second conductive layer can be well carried out, thereby improving the photoelectric conversion efficiency.

[0021] Furthermore, in the photoelectric conversion element of the present invention, it is preferable that the film thickness of the porous self-supporting sheet is typically 20 μm or more. If the film thickness of the porous self-supporting sheet is 20 μm or more, the second conductive layer can be sufficiently endowed with the function of a current collector electrode.

[0022] Furthermore, in the photoelectric conversion element of the present invention, the porous self-supporting sheet may also contain the material constituting the power generation layer, or at least a portion of the material constituting the power generation layer. If the porous self-supporting sheet contains the material constituting the power generation layer, or at least a portion of the material constituting the power generation layer, the charge transfer between the power generation layer and the second conductive layer can be effectively carried out, thereby improving the photoelectric conversion efficiency.

[0023] Furthermore, in the photoelectric conversion element of the present invention, the power generation layer preferably comprises a perovskite compound. By using a power generation layer comprising a perovskite compound, the manufacturing cost of the photoelectric conversion element can be reduced, and the ease of manufacturing the photoelectric conversion element can be improved.

[0024] Furthermore, in the photoelectric conversion element of the present invention, it is preferable that the average diameter (Av) of the aforementioned monolayer carbon nanotube and the standard deviation (σ) of the diameter satisfy the following relationship: 0.20 < (3σ / Av) < 0.60. Using monolayer carbon nanotubes that satisfy the above relationship can further improve the photoelectric conversion efficiency.

[0025] It should be noted that the "average diameter (Av) of carbon nanotubes" and the "standard deviation (σ) of the diameter of carbon nanotubes" can be determined by measuring the diameter (outer diameter) of 100 randomly selected monolayer CNTs using a transmission electron microscope. Furthermore, the average diameter (Av) and standard deviation (σ) of monolayer CNTs can be adjusted by changing the manufacturing method and conditions of the monolayer CNTs, or by combining multiple monolayer CNTs obtained using different manufacturing methods.

[0026] Furthermore, in the photoelectric conversion element of the present invention, the aforementioned monolayer carbon nanotube preferably exhibits an upwardly convex t-curve obtained from the adsorption isotherm. Using monolayer carbon nanotubes with an upwardly convex t-curve enables the fabrication of more stable porous self-supporting sheets and the stable fabrication of photoelectric conversion elements.

[0027] Furthermore, in the photoelectric conversion element of the present invention, the first conductive layer preferably comprises a metal oxide and / or an organic compound. For example, if a first conductive layer comprising a metal oxide and / or an organic compound is used, and the metal oxide and / or organic compound has an optimized energy level relative to the energy level of the power generation layer comprising the perovskite compound, the performance of the photoelectric conversion element can be further improved.

[0028] Furthermore, the object of the present invention is to advantageously solve the above-mentioned problems. The method for manufacturing the photoelectric conversion element of the present invention is characterized by being a method for manufacturing any of the aforementioned photoelectric conversion elements. This method includes a step of stacking the porous self-supporting sheet onto the power generation layer while maintaining a solvent or solution at the interface between at least one of the power generation layer and the porous self-supporting sheet. By stacking the porous self-supporting sheet onto the power generation layer while maintaining a solvent or solution at the interface between at least one of the power generation layer and the porous self-supporting sheet, a photoelectric conversion element exhibiting excellent photoelectric conversion efficiency can be easily manufactured.

[0029] Furthermore, the method for manufacturing the photoelectric conversion element of the present invention can also involve using a poor solvent, and stacking the porous self-supporting sheet impregnated with the solvent onto the power generation layer. If this is done, the porous self-supporting sheet can be well adhered to the power generation layer.

[0030] Furthermore, the method for manufacturing the photoelectric conversion element of the present invention can also involve the power generation layer being a layer composed of a perovskite compound, the solution being a solution formed by dissolving at least one of the precursors of the perovskite compound in a poor solvent, and the porous self-supporting sheet impregnated with the solution being laminated onto the power generation layer. If this is done, a porous self-supporting sheet containing at least one of the precursors of the perovskite compound can be laminated onto the power generation layer, thus enabling efficient charge transfer between the power generation layer and the second conductive layer in the resulting photoelectric conversion element, thereby improving the photoelectric conversion efficiency.

[0031] Furthermore, the method for manufacturing the photoelectric conversion element of the present invention can also involve using an organic material solution formed by dissolving the organic material A in a poor solvent, and then stacking the porous self-supporting sheet impregnated with the organic material solution onto the power generation layer. This also allows the porous self-supporting sheet to be well adhered to the power generation layer.

[0032] Furthermore, the manufacturing method of the photoelectric conversion element of the present invention preferably includes a step of heating and pressing the porous self-supporting sheet stacked on the above-mentioned power generation layer. This results in a photoelectric conversion element with excellent integrity.

[0033] Invention Effects

[0034] The present invention provides a photoelectric conversion element that exhibits excellent photoelectric conversion efficiency and is easy to manufacture, as well as a method for manufacturing the photoelectric conversion element. Attached Figure Description

[0035] Figure 1 This is a cross-sectional view schematically illustrating the structure of a photoelectric conversion element according to one embodiment of the present invention.

[0036] Figure 2 This is a cross-sectional view schematically illustrating the structure of a photoelectric conversion element according to a modified embodiment of the present invention. Detailed Implementation

[0037] The photoelectric conversion element of the present invention is not particularly limited, and can be used, for example, as a perovskite solar cell. Hereinafter, reference will be made to... Figure 1 and Figure 2 The present invention will be described in detail one embodiment of the photoelectric conversion element and its variations.

[0038] (Photoelectric conversion element)

[0039] Figure 1This is a schematic cross-sectional view illustrating the structure of a photoelectric conversion element according to one embodiment of the present invention. The photoelectric conversion element 100 is integrally formed of a laminate having a light-transmitting substrate 1, a transparent conductive film 2, a first conductive layer 5 composed of a substrate layer 3 and a porous semiconductor layer 4, a power generation layer 6, and a second conductive layer 8 in sequence. Moreover, the second conductive layer 8 is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes (hereinafter referred to as "single-layer CNT"). Hereinafter, each constituent component constituting the photoelectric conversion element 100 will be described in sequence.

[0040] <Transparent substrate 1>

[0041] The light-transparent substrate 1 forms the base of the photoelectric conversion element 100. There are no particular limitations on the light-transparent substrate 1, and examples include substrates made of glass or synthetic resin, films made of synthetic resin, etc.

[0042] Examples of glass that constitutes the light-transmitting substrate 1 include glass made of inorganic materials such as soda glass.

[0043] Furthermore, examples of synthetic resins constituting the light-transmitting substrate 1 include polyacrylic acid resin, polycarbonate resin, polyester resin, polyimide resin, polystyrene resin, polyvinyl chloride resin, polyamide resin, and polycyclic olefin resin. From the viewpoint of obtaining a thin, lightweight, and flexible photoelectric conversion element 100, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferred as synthetic resins.

[0044] There are no particular limitations on the thickness of the light-transmitting substrate 1, as long as it is thick enough to maintain the shape of the substrate. For example, the thickness of the light-transmitting substrate 1 can be 0.1 mm or more and 10 mm or less.

[0045] <Transparent Conductive Film 2>

[0046] The transparent conductive film 2 is a film made of metal oxide formed on the surface of the light-transmitting substrate 1. By providing the transparent conductive film 2, the surface of the light-transmitting substrate 1 can be made conductive.

[0047] Examples of metal oxides constituting the transparent conductive film 2 include fluorine-doped tin oxide (FTO), tin oxide (SnO), indium oxide (In₂O₃), tin-doped indium oxide (ITO), zinc oxide (ZnO), indium oxide / zinc oxide (IZO), and gallium oxide / zinc oxide (GZO). Furthermore, although in Figure 1In the photoelectric conversion element 100 shown, there is one transparent conductive film 2 on the light-transmitting substrate 1, but there may also be two or more transparent conductive films 2 on the light-transmitting substrate 1. Furthermore, when the photoelectric conversion element 100 has two or more transparent conductive films 2, each transparent conductive film may be made of the same metal oxide or may be made of different metal oxides.

[0048] The thickness of the transparent conductive film 2 is not particularly limited, as long as it imparts the desired conductivity to the light-transmitting substrate 1; for example, it can be 1 nm or more and 1 μm or less. Furthermore, the transparent conductive film 2 can be formed on the entire surface of the light-transmitting substrate 1, or it can be formed as follows: Figure 1 As shown, it is formed on a portion of the surface of the light-transmitting substrate 1.

[0049] <First conductive layer 5>

[0050] The first conductive layer 5 functions as a charge transport layer and is made of an n-type semiconductor. Furthermore, although in this embodiment the first conductive layer 5 is composed of a substrate layer 3 and a porous semiconductor layer 4, it is not limited to this; the first conductive layer 5 can also be a single layer made of an n-type semiconductor.

[0051] <Basal layer 3>

[0052] The substrate layer 3 can be arbitrarily positioned. By setting the substrate layer 3, direct contact between the light-transmitting substrate 1, the transparent conductive film 2, and the porous semiconductor layer 4 can be prevented. This prevents the loss of electromotive force and thus improves the photoelectric conversion efficiency of the photoelectric conversion element 100.

[0053] The substrate layer 3 can be a porous film or a non-porous dense film, as long as it is made of, for example, an n-type semiconductor. However, from the viewpoint of sufficiently preventing the transparent substrate 1 and the transparent conductive film 2 from contacting the porous semiconductor layer 4, it is preferable that the substrate layer 3 is a non-porous dense film. Furthermore, the thickness of the substrate layer 3 is not particularly limited and can be, for example, 1 nm or more and 500 nm or less. In addition, the substrate layer 3 may arbitrarily contain insulating materials other than n-type semiconductors in a proportion that does not impair the properties of the n-type semiconductor in the substrate layer 3.

[0054] <Porous Semiconductor Layer 4>

[0055] The porous semiconductor layer 4 is a porous layer. By including the porous semiconductor layer 4 in the first conductive layer 5, the photoelectric conversion efficiency of the photoelectric conversion element 100 can be further improved.

[0056] The porous semiconductor layer 4 preferably comprises metal oxides and / or organic compounds, more preferably comprises microparticles composed of metal oxides and / or organic compounds, and even more preferably is formed of microparticles composed of metal oxides and / or organic compounds.

[0057] Here, there are no particular restrictions on the metal oxide used to form the porous semiconductor layer 4, as long as it can function as an n-type semiconductor; for example, titanium dioxide (TiO2) can be used.

[0058] In addition, examples of organic compounds that form the porous semiconductor layer 4 include fullerene derivatives such as methyl phenyl C61 butyrate (PCBM).

[0059] Furthermore, the particle size (average particle size of primary particles) of the metal oxide and / or organic compound particles used in the porous semiconductor layer 4 is preferably 2 nm or more and 80 nm or less, more preferably 30 nm or less. By making the particle size smaller, the resistance of the porous semiconductor 4 can be reduced. Particles of the same size can be used alone, or particles of different sizes can be used in combination. In addition, the average particle size can be determined by measuring the particle size of 100 randomly selected particles using an electron microscope.

[0060] The thickness of the porous semiconductor layer 4 is not particularly limited, but is typically 5 nm or more, preferably 10 nm or more, typically less than 500 nm, and preferably less than 100 nm. The porous semiconductor layer 4 can be as follows: Figure 1 It can be formed by one layer, or it can be formed by multiple layers.

[0061] <Power Generation Layer 6>

[0062] The power generation layer 6 is a layer made of a material that generates an electromotive force by absorbing light, preferably a layer containing a perovskite compound, and more preferably a layer made of a perovskite compound (perovskite layer).

[0063] Here, there are no particular restrictions on the perovskite compound constituting the power generation layer 6, and known perovskite compounds can be used. Specifically, perovskite compounds such as CH3NH3PbI3, CH3NH3PbBr3, (CH3(CH2)nCHCH3NH3)2PbI4 [n=5~8], and (C6H5C2H4NH3)2PbBr4 can be used.

[0064] The thickness of the power generation layer 6 is not particularly limited, but is preferably 100 nm or more, more preferably 200 nm or more, preferably 1 μm or less, and more preferably 800 nm or less. By making the thickness of the power generation layer 6 100 nm or more, the electromotive force of the power generation layer 6 can be increased.

[0065] <Second conductive layer 8>

[0066] The second conductive layer 8 is a layer composed of a porous self-supporting sheet. Here, the porous self-supporting sheet needs to contain at least a single layer of CNTs, preferably a sheet composed of a single layer of CNTs, and more preferably a sheet composed of Buck paper. By using a porous self-supporting sheet containing at least a single layer of CNTs, the second conductive layer 8 can be endowed with excellent functions as a hole transport layer and as a current collector electrode.

[0067] <<Porous Self-Supporting Sheet>>

[0068] Furthermore, the monolayer CNTs contained in the porous self-supporting sheet preferably contain monolayer CNTs having the following properties.

[0069] -(3σ / Av)-

[0070] In the single-layer CNTs contained in the porous self-supporting sheet, the ratio of the standard deviation of the diameter (σ) multiplied by 3 (3σ) to the average diameter (Av) (3σ / Av) is preferably greater than 0.20, more preferably greater than 0.25, even more preferably greater than 0.50, and preferably less than 0.60. If 3σ / Av is greater than 0.20 and less than 0.60, even if the amount of single-layer CNTs contained in the porous self-supporting sheet is small, the second conductive layer 8 can be sufficiently endowed with the functions of a hole transport layer and a current collector electrode.

[0071] -Average diameter (Av) of a single layer of CNTs-

[0072] The average diameter (Av) of the monolayer CNT is preferably 0.5 nm or more, more preferably 1 nm or more, more preferably 15 nm or less, and even more preferably 10 nm or less. If the average diameter (Av) of the monolayer CNT is 0.5 nm or more, the aggregation of the monolayer CNT can be suppressed, and the dispersion of the monolayer CNT in the second conductive layer 8 can be improved. Furthermore, if the average diameter (Av) of the monolayer CNT is 15 nm or less, the second conductive layer 8 can fully perform its function as a current collector electrode.

[0073] -t-curve-

[0074] The monolayer CNT preferably exhibits an upwardly convex t-curve obtained from the adsorption isotherm. More preferably, the monolayer CNT is one without any opening treatment. Using a monolayer CNT with an upwardly convex t-curve obtained from the adsorption isotherm allows for the acquisition of a second conductive layer 8 with excellent strength.

[0075] In addition, the bending point of the t-curve of the monolayer CNT is preferably in the range of 0.2≤t(nm)≤1.5, more preferably in the range of 0.45≤t(nm)≤1.5, and even more preferably in the range of 0.55≤t(nm)≤1.0.

[0076] The determination of adsorption isotherms, the plotting of t-curves, and the analysis of t-curves of monolayer CNTs can be performed using, for example, a commercially available measuring device, “BELSORP-mini” (manufactured by BEL Corporation of Japan).

[0077] There are no particular limitations on the monolayer CNTs possessing the aforementioned properties, and they can be efficiently manufactured, for example, by forming a catalyst layer on the substrate surface using a wet process in the Super Growth method (refer to International Publication No. 2006 / 011655). Here, the Super Growth method refers to a method in which, during the synthesis of CNTs using chemical vapor deposition (CVD) by supplying a raw material compound and a carrier gas to a substrate having a catalyst layer for CNT manufacturing, a trace amount of oxidant (catalyst activator) is present in the system, thereby dramatically increasing the catalytic activity of the catalyst layer.

[0078] From the viewpoint that porous self-supporting sheets with large film thickness can be easily obtained, monolayer CNTs obtained by the Super Growth method are preferred as monolayer CNTs.

[0079] Furthermore, the porous self-supporting sheet may contain the material constituting the power generation layer 6, or a portion thereof. More specifically, the porous self-supporting sheet may contain the material constituting the power generation layer 6, or a portion thereof, within its plurality of fine pores.

[0080] There is no particular limitation on the proportion of monolayer CNTs contained in the porous self-supporting sheet, but it is preferably 50% by mass or more, and more preferably 75% by mass or more.

[0081] Furthermore, as materials that can be arbitrarily included in porous self-supporting sheets other than monolayer CNTs, examples include organic materials as p-type semiconductors, inorganic materials, and fibrous carbon nanostructures other than monolayer CNTs.

[0082] Examples of organic materials that can be included in porous self-supporting sheets include 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spiro-meOTAD, poly(3-hexylthiophene) (P3HT), and polytriallylamine (PTAA).

[0083] In addition, inorganic materials that can be included in porous self-supporting sheets include, for example, CuI, CuSCN, CuO, Cu2O, etc.

[0084] The thickness of the porous self-supporting sheet is preferably 20 μm or more, preferably 30 μm or more, preferably 200 μm or less, and more preferably 80 μm or less. If the thickness of the porous self-supporting sheet is 20 μm or more and 200 μm or less, the second conductive layer 8 can perform a better function as a current collector electrode.

[0085] <<Manufacturing Method of Porous Self-Supporting Sheets>>

[0086] There are no particular limitations on the manufacturing method of the porous self-supporting sheet. For example, a method including a film-forming step can be used, namely, removing the solvent from a dispersion of fibrous carbon nanostructures containing at least a monolayer of CNTs, a dispersant, and a solvent, thereby forming a porous self-supporting sheet. Furthermore, in the manufacturing method of the porous self-supporting sheet, a dispersion preparation step can be arbitrarily included before the film-forming step, namely, dispersing a coarse dispersion containing at least a monolayer of CNTs, a dispersant, and a solvent to prepare the aforementioned fibrous carbon nanostructure dispersion.

[0087] -Dispersion preparation process-

[0088] In the dispersion preparation process, there are no particular limitations on the dispersion treatment of the coarse dispersion containing at least a monolayer CNT fibrous carbon nanostructure, a dispersant, and a solvent. Preferably, the coarse dispersion is supplied to a dispersion treatment that achieves the cavitation effect or fragmentation effect described in detail below, thereby dispersing the monolayer CNT fibrous carbon nanostructure and preparing a fibrous carbon nanostructure dispersion. In this way, by performing a dispersion treatment that achieves the cavitation effect or fragmentation effect, a fibrous carbon nanostructure dispersion in which the monolayer CNT fibrous carbon nanostructure is well dispersed can be obtained. Furthermore, if a porous self-supporting sheet is fabricated using a fibrous carbon nanostructure in which the monolayer CNT is well dispersed, the monolayer CNT can be uniformly dispersed, thereby obtaining a porous self-supporting sheet with excellent electrical conductivity, thermal conductivity, and mechanical properties. Alternatively, other known dispersion treatments besides those described above can be used to disperse the monolayer CNT fibrous carbon nanostructure in a solvent, thereby preparing a fibrous carbon nanostructure dispersion for manufacturing porous self-supporting sheets.

[0089] The fibrous carbon nanostructures used to prepare the fibrous carbon nanostructure dispersions only need to be fibrous carbon nanostructures that contain at least a single layer of CNTs. For example, it can be a mixture of single-layer CNTs and fibrous carbon nanostructures other than single-layer CNTs (such as multilayer CNTs).

[0090] Here, in the fibrous carbon nanostructure dispersion, the content ratio of monolayer CNTs to fibrous carbon nanostructures other than monolayer CNTs can be, for example, a mass ratio (monolayer CNTs / fibrous carbon nanostructures other than monolayer CNTs) of 50 / 50 to 75 / 25.

[0091] =Dispersant=

[0092] There are no particular limitations on the dispersant used to prepare the fibrous carbon nanostructure dispersion, as long as it can disperse fibrous carbon nanostructures containing at least a monolayer of CNTs and can dissolve in the solvent used to prepare the fibrous carbon nanostructure dispersion. For example, surfactants, synthetic polymers, or natural polymers can be used as such dispersants.

[0093] Examples of surfactants include sodium dodecyl sulfonate, sodium deoxycholate, sodium cholate, and sodium dodecylbenzene sulfonate.

[0094] In addition, examples of synthetic polymers include polyether glycol, polyester glycol, polycarbonate glycol, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resin, epoxy resin, modified epoxy resin, phenoxy resin, modified phenoxy resin, phenoxy ether resin, phenoxy ester resin, fluorinated resin, melamine resin, alkyd resin, phenolic resin, polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.

[0095] Furthermore, examples of natural macromolecules include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, gel polysaccharides, chitin, chitosan, cellulose, and their salts or derivatives. Derivatives refer to previously known compounds such as esters and ethers.

[0096] These dispersants can be used in one or in combination of two or more. From the viewpoint of excellent dispersibility of fibrous carbon nanostructures containing monolayer CNTs, surfactants are preferred as dispersants, and sodium deoxycholate is more preferred.

[0097] =Solvent=

[0098] There are no particular limitations on the solvents used for dispersions of fibrous carbon nanostructures. Examples include: alcohols such as water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and pentyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and diethyl ether, diethyl... Ethers such as alkanes and tetrahydrofurans; polar organic solvents such as N,N-dimethylformamide and N-methylpyrrolidone; and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, o-dichlorobenzene, and p-dichlorobenzene. These substances can be used alone or in combination with two or more.

[0099] Furthermore, in the dispersion preparation process, it is preferable to perform a dispersion treatment, for example, as shown below, to obtain cavitation or breakup effects.

[0100] ~Dispersion treatment that can achieve cavitation effect~

[0101] The dispersion treatment that achieves cavitation effect utilizes the shock wave generated by the collapse of vacuum bubbles in water when high energy is imparted to the liquid. By using this dispersion method, monolayer CNTs can be well dispersed.

[0102] Here, specific examples of dispersion processes that can achieve cavitation effects include dispersion processes using ultrasound, dispersion processes using jet mills, and dispersion processes using high-shear stirring. These dispersion processes can be performed individually or in combination. More specifically, it is preferable to use, for example, an ultrasonic homogenizer, a jet mill, and a high-shear stirring device. These devices can be those already known in the art.

[0103] When using an ultrasonic homogenizer to disperse monolayer CNTs, the coarse dispersion can be simply irradiated with ultrasound using the ultrasonic homogenizer. The irradiation time can be appropriately set according to the amount of monolayer CNTs, for example, preferably 3 minutes or more, more preferably 30 minutes or more, and preferably 5 hours or less, more preferably 2 hours or less. In addition, for example, the power is preferably 20W or more and 500W or less, more preferably 100W or more and 500W or less, and the temperature is preferably 15°C or more and 50°C or less.

[0104] Furthermore, when using a jet mill, the number of treatments can be appropriately set according to the amount of CNTs in a single layer, for example, preferably 2 or more, more preferably 5 or more, and preferably 100 or less, more preferably 50 or less. Additionally, for example, the pressure is preferably 20 MPa or more and 250 MPa or less, and the temperature is preferably 15°C or more and 50°C or less.

[0105] Furthermore, when using high-shear agitation, it is sufficient to apply agitation and shearing to the coarse dispersion using a high-shear agitator. The faster the rotation speed, the better. For example, the running time (the time the machine rotates) is preferably 3 minutes or more and 4 hours or less, the circumferential speed is preferably 5 m / s or more and 50 m / s or less, and the temperature is preferably 15°C or more and 50°C or less.

[0106] Furthermore, the dispersion treatment described above, which yields cavitation effects, is preferably performed at a temperature below 50°C. This is because it can suppress concentration changes caused by solvent evaporation.

[0107] ~Dispersion treatment that can achieve a crushing effect~

[0108] The dispersion treatment that achieves a breakage effect not only uniformly disperses monolayer CNTs in the solvent, but is also more advantageous than the dispersion treatment that achieves a cavitation effect in suppressing damage to monolayer CNTs caused by the shock wave when bubbles disappear.

[0109] In this dispersion process that achieves a breaking effect, shear force is applied to the coarse dispersion to break and disperse the aggregates of fibrous carbon nanostructures containing monolayer CNTs, thereby loading back pressure onto the coarse dispersion. Furthermore, the coarse dispersion is cooled as needed, thereby suppressing the generation of bubbles and ensuring that the monolayer CNTs are uniformly dispersed in the solvent.

[0110] In addition, when applying back pressure to the coarse dispersion load, the back pressure to the coarse dispersion load can be directly reduced to atmospheric pressure, but it is preferable to reduce the pressure in multiple stages.

[0111] -Film Forming Process-

[0112] In the film-forming process, the solvent is removed from the aforementioned fibrous carbon nanostructure dispersion to form a porous self-supporting sheet. Specifically, in the film-forming process, for example, either method (A) or (B) below is used to remove the solvent from the fibrous carbon nanostructure dispersion to form a porous self-supporting sheet.

[0113] (A) A method for drying the fibrous carbon nanostructure dispersion after coating it onto a film-forming substrate.

[0114] (B) A method for filtering a dispersion of fibrous carbon nanostructures using a porous film-forming substrate and drying the resulting filtrate.

[0115] [Film-forming substrate]

[0116] There are no particular restrictions on the film-forming substrate, and known substrates can be used.

[0117] Specifically, in method (A) above, resin substrates and glass substrates can be used as film-forming substrates for coating the fibrous carbon nanostructure dispersion. Here, as resin substrates, substrates composed of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, polymethyl methacrylate, alicyclic acrylic resins, cyclic olefin resins, triacetyl cellulose, etc., can be used. Furthermore, as glass substrates, substrates made of ordinary soda glass can be used.

[0118] Furthermore, in the above method (B), porous sheets composed of filter paper, cellulose, cellulose nitrate, alumina, etc., can be used as film-forming substrates for filtering fibrous carbon nanostructure dispersions.

[0119] [Apply as a poultice]

[0120] In the above method (A), known methods can be used as the method for coating a dispersion of fibrous carbon nanostructures onto a film-forming substrate. Specifically, as the coating method, dip coating, roller coating, gravure coating, doctor blade coating, air knife coating, roller knife coating, mold coating, screen printing, spraying, gravure printing, etc., can be used.

[0121] [filter]

[0122] In method (B) above, known filtration methods can be used as a method for filtering a dispersion of fibrous carbon nanostructures using a film-forming substrate. Specifically, natural filtration, reduced pressure filtration, pressurized filtration, centrifugal filtration, etc., can be used as filtration methods.

[0123] [dry]

[0124] As for the method of drying the fibrous carbon nanostructure dispersion coated on the film-forming substrate in method (A) above, or the method of drying the filtrate obtained in method (B) above, known drying methods can be used. Examples of drying methods include hot air drying, vacuum drying, hot roller drying, and infrared irradiation. There are no particular limitations on the drying temperature, which is usually room temperature to 200°C, and there are no particular limitations on the drying time, which is usually 0.1 to 150 minutes.

[0125] Post-processing of porous self-supporting sheets

[0126] Here, the porous self-supported sheet formed as described above typically contains monolayer CNTs, fibrous carbon nanostructures other than monolayer CNTs, a dispersant, and other components included in the fibrous carbon nanostructure dispersion in the same proportion as the fibrous carbon nanostructure dispersion. Therefore, in the method for manufacturing the porous self-supported sheet, the porous self-supported sheet formed in the film-forming process can be arbitrarily cleaned to remove the dispersant from the porous self-supported sheet. Removing the dispersant from the porous self-supported sheet can further improve its properties, such as conductivity.

[0127] Furthermore, the porous self-supporting sheet can be cleaned by contacting it with a solvent capable of dissolving the dispersant, thereby dissolving the dispersant in the porous self-supporting sheet into the solvent. Moreover, there are no particular limitations on the solvent capable of dissolving the dispersant in the porous self-supporting sheet; the aforementioned solvents suitable for use as dispersions of fibrous carbon nanostructures can be used, preferably the same solvent used for dispersions of fibrous carbon nanostructures. Furthermore, the contact between the porous self-supporting sheet and the solvent can be performed by immersing the porous self-supporting sheet in the solvent or by coating the porous self-supporting sheet with the solvent. Finally, the cleaned porous self-supporting sheet can be dried using known methods.

[0128] Furthermore, during the manufacture of porous self-supporting sheets, the porosity can be adjusted arbitrarily as needed. For example, the density can be further increased by pressing the porous self-supporting sheet formed in the film-forming process. From the viewpoint of suppressing damage to monolayer CNTs or the degradation of properties due to damage, the pressing pressure during pressing is preferably less than 3 MPa, and more preferably no pressing is performed.

[0129] The aforementioned photoelectric conversion element 100 enables a second conductive layer 8 to function as both a hole transport layer and a current collector electrode. Furthermore, since the second conductive layer 8 is composed of a porous self-supporting sheet containing at least a single layer of CNTs, its shape is stable. Therefore, with this structure, the photoelectric conversion element can be easily scaled up to a large area. Additionally, as long as the photoelectric conversion element of the present invention is an integrated product that sequentially maintains the aforementioned constituent components, and the second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of CNTs, it may further include other layers without compromising the effects of the present invention.

[0130] (Manufacturing method of photoelectric conversion element)

[0131] Next, refer to again Figure 1The manufacturing method of the photoelectric conversion element 100 of the present invention will be described below. The manufacturing method of the photoelectric conversion element 100 of the present invention includes a step of laminating the porous self-supporting sheet onto the power generation layer 6 while maintaining a solvent or solution at the interface between at least one of the power generation layer 6 and the porous self-supporting sheet, and optionally includes a step of heating and pressing the porous self-supporting sheet laminated on the power generation layer 6. Furthermore, the aforementioned "interface" refers to the surface of the power generation layer 6 opposite to the porous self-supporting sheet. The manufacturing method of the photoelectric conversion element 100 will be described in detail below.

[0132] <Preparation of Transparent Substrate 1>

[0133] In the method for manufacturing the photoelectric conversion element 100 of the present invention, firstly, a light-transmitting substrate 1 is prepared. The types of light-transmitting substrate 1 listed in the "photoelectric conversion element" section can be used.

[0134] <Formation of transparent conductive film 2>

[0135] Next, a transparent conductive film 2 is formed on the light-transmitting substrate 1. There are no particular limitations on the method for forming the transparent conductive film 2; known methods such as sputtering or vapor deposition can be used. Alternatively, the formation of the transparent conductive film 2 can be omitted by using a commercially available light-transmitting substrate on which the transparent conductive film is formed.

[0136] <Forming of the first conductive layer 5>

[0137] Then, a first conductive layer 5 is formed on the transparent conductive film 2. The first conductive layer 5 can be obtained by forming a base layer 3 on the transparent conductive film 2, followed by forming a porous semiconductor layer 4.

[0138] [Formation of basal layer 3]

[0139] There are no particular limitations on the method of forming the substrate 3, and it can be formed, for example, by spraying a solution containing a material forming an n-type semiconductor onto the transparent conductive film 2.

[0140] Examples of spraying methods include spray pyrolysis, aerosol deposition, electrostatic spraying, and cold spraying.

[0141] [Formation of porous semiconductor layer 4]

[0142] There are no particular limitations on the method of forming the porous semiconductor layer 4. It can be formed, for example, by spin-coating a solution containing an n-type semiconductor precursor onto the substrate layer 3 and then drying it.

[0143] Examples of precursors for n-type semiconductors include titanium alkoxides such as titanium tetrachloride (TiCl4), peroxytitanic acid (PTA), ethoxytitanic acid, and titanium isopropoxide (TTIP); and metal alkoxides such as zinc alkoxide, alkoxysilane, alkoxyzirconium, and bis(acetylacetonyl)diisopropyltitanate.

[0144] Furthermore, there are no particular restrictions on the solvent used in the solution containing the n-type semiconductor, and alcoholic solutions such as ethanol can be used.

[0145] Furthermore, there are no particular restrictions on the temperature and time for drying the solution applied to the substrate 3; they can be adjusted appropriately according to the type of n-type precursor and the type of solvent used.

[0146] <Formation of Power Generation Layer 6>

[0147] Then, a power-generating layer 6 is formed on the first conductive layer 5. The power-generating layer 6 can be formed by vacuum evaporation, coating, etc., without particular limitations. For example, it can be formed by coating a precursor-containing solution containing a perovskite compound precursor onto the first conductive layer 5 and then sintering it. Examples of perovskite compound precursors include lead iodide (PbI2) and methylammonium iodide (CH3NH3I). Furthermore, there are no particular limitations on the solvent contained in the precursor-containing solution; examples include N,N-dimethylformamide and dimethyl sulfoxide. After coating with these solutions, a poor solvent can be used to promote the precipitation of the perovskite compound. In this specification, a poor solvent refers to a solvent in which the perovskite compound does not substantially change during the manufacturing process. During the manufacturing process, if no visual changes such as film turbidity are observed in the perovskite compound, it can be considered substantially unchanged.

[0148] Here, the concentration of the perovskite compound precursor in the precursor solution can be adjusted to a suitable concentration based on the solubility of the materials constituting the perovskite compound, for example, around 0.5 M to 1.5 M.

[0149] Furthermore, there are no particular limitations on the method of applying the precursor solution to the first conductive layer 5, and known coating methods such as spin coating, spray coating, and bar coating can be used.

[0150] <Forming of the second conductive layer 8>

[0151] After forming the power generation layer 6, a second conductive layer 8 is formed on the power generation layer 6. In the manufacturing method of the photoelectric conversion element 100 of the present invention, the porous self-supporting sheet is stacked on the power generation layer 6 while the interface between at least one of the power generation layer 6 and the porous self-supporting sheet is kept in a solvent or solution state. As a result, it is possible to easily manufacture a photoelectric conversion element 100 with excellent photoelectric conversion efficiency.

[0152] Examples of undesirable solvents include chlorobenzene, toluene, and anisole. Using these undesirable solvents allows for the proper adhesion of the porous self-supporting sheet to the power generation layer 6, for example, when the power generation layer 6 is a perovskite layer composed of a perovskite compound.

[0153] Furthermore, when the power-generating layer 6 is a perovskite layer, a solution formed by dissolving at least one precursor of the perovskite compound in a poor solvent can be used as the aforementioned solution. Doing so allows for a better formation of the interface between the perovskite layer and the porous self-supporting sheet. Consequently, charge transfer between the power-generating layer 6 and the second conductive layer 8 can be performed efficiently in the resulting photoelectric conversion element 100, resulting in improved photoelectric conversion efficiency.

[0154] Furthermore, if a porous self-supporting sheet impregnated with the aforementioned solvent or solution is used, the solvent or solution can be well retained at the interface between the power generation layer 6 and at least one of the porous self-supporting sheet.

[0155] Here, a porous self-supporting sheet impregnated with a solvent or solution can be obtained, for example, by immersing the porous self-supporting sheet in the aforementioned solvent or solution and then lifting it out. In this case, there is no particular limitation on the immersion time; it can be set as appropriate depending on the type of solvent or solution used.

[0156] Furthermore, in the manufacturing method of the photoelectric conversion element 100 of the present invention, it is preferable to heat-press the porous self-supporting sheet stacked on the power generation layer 6. This results in a photoelectric conversion element 100 with excellent integrity. The heating temperature is not particularly limited and can be, for example, around 100°C. Furthermore, the pressure during heat pressing is not particularly limited and can be, for example, 0.05 MPa. Furthermore, the pressing time is not particularly limited and can be, for example, 30 seconds. In addition, during heat pressing, to accelerate the removal of solvent components contained in the porous self-supporting sheet, it is preferable to press in a manner that ensures a solvent evaporation path. Specifically, to ensure a solvent evaporation path, it is preferable to heat-press through, for example, a porous component such as a thick wiping cloth, porous rubber, porous metal, or porous ceramic.

[0157] Based on the manufacturing method described above, it is possible to manufacture efficiently. Figure 1 The photoelectric conversion element 100 shown is illustrated. It should be noted that the manufacturing method of the photoelectric conversion element of the present invention is not limited to the method described above. Without impairing the effects of the present invention, it may include other processes besides those described above.

[0158] (A modified photoelectric conversion element)

[0159] Figure 2This is a cross-sectional view schematically illustrating the structure of a photoelectric conversion element according to a modified embodiment of the present invention. The photoelectric conversion element 200 is integrally formed from a laminate having, in sequence, a light-transmitting substrate 1, a transparent conductive film 2, a first conductive layer 5 composed of a substrate layer 3 and a porous semiconductor layer 4, a power-generating layer 6, a bonding layer 7, and a second conductive layer 8. It is sufficient that at least a portion of the bonding layer 7 is present between the power-generating layer 6 and the second conductive layer 8; alternatively, it can be as follows... Figure 2 As shown, a bonding layer 7 is present between the power generation layer 6 and the second conductive layer 8. Furthermore, the bonding layer 7 is composed of an organic material A and has a different composition and properties from the power generation layer 6 and the second conductive layer 8.

[0160] Furthermore, the photoelectric conversion element in the embodiment of the present invention is the same as the photoelectric conversion element in the embodiment of the present invention described above, except that it further includes a bonding layer 7. Therefore, in the following description, the same reference numerals will be used for parts that have the same basic function as those in the above-described embodiments, and their descriptions will be omitted.

[0161] <Joint Layer 7>

[0162] As described above, at least a portion between the power generation layer 6 and the second conductive layer 8 has a bonding layer 7. Furthermore, the bonding layer 7 is made of an organic material A and has a different composition and properties from the power generation layer 6 and the second conductive layer 8. The bonding layer 7 is provided to fill the gaps formed between the power generation layer 6 and the second conductive layer 8 due to the unevenness of the surface of the power generation layer 6 and the porous self-supporting sheet constituting the second conductive layer 8. By having the bonding layer 7, the charge transfer between the power generation layer 6 and the second conductive layer 8 in the photoelectric conversion element 200 can be effectively carried out, thereby enabling the photoelectric conversion element 200 to exhibit excellent photoelectric conversion efficiency.

[0163] Examples of organic materials A constituting the bonding layer 7 include, for instance, polymethyl methacrylate (PMMA), a polymer exhibiting adhesive properties, and 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spiro-meOTAD, a polymer exhibiting semiconductor properties. Alternatively, mixtures of these various materials may also be used.

[0164] The thickness of the bonding layer 7 is not particularly limited as long as it can fill the gap formed between the power generation layer 6 and the second conductive layer 8, and can be set as appropriate according to the shape of the surface of the power generation layer 6 and the second conductive layer 8.

[0165] Furthermore, the porous self-supporting sheet preferably comprises the material constituting the bonding layer 7. More specifically, the porous self-supporting sheet preferably contains an organic material A constituting the bonding layer 7 within the plurality of pores of the porous self-supporting sheet.

[0166] According to the photoelectric conversion element 200 described above, a second conductive layer 8 can function as both a hole transport layer and a current collector electrode. Furthermore, by having a bonding layer 7 between the power generation layer 6 and the second conductive layer 8, the gap between them can be filled, thus enabling efficient charge transfer between them and improving photoelectric conversion efficiency. Moreover, since the second conductive layer 8 is composed of a porous self-supporting sheet containing at least a single layer of CNTs, its shape is stable. Therefore, with this structure, large-area photoelectric conversion elements can be easily achieved. Additionally, as long as the photoelectric conversion element of this modified example is an integral body that sequentially maintains the above-described composite material, the second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of CNTs, a bonding layer is present in at least a portion of the power generation layer and the second conductive layer, and the bonding layer is made of an organic material A and has a different composition and properties from the power generation layer and the second conductive layer, other layers may be further included without impairing the effects of the present invention.

[0167] (Manufacturing method of a modified photoelectric conversion element)

[0168] Next, refer to again Figure 2 The manufacturing method of a modified photoelectric conversion element of the present invention will be described below. The manufacturing method of the modified photoelectric conversion element 200 of the present invention includes a step of laminating the porous self-supporting sheet onto the power generation layer 6 while maintaining a solvent or solution at the interface of at least one of the power generation layer 6 and the porous self-supporting sheet, and optionally includes a step of heating and pressing the porous self-supporting sheet laminated on the power generation layer 6. The manufacturing method of the photoelectric conversion element 200 will be described in detail below.

[0169] In the manufacturing method of the photoelectric conversion element 200 of the modified embodiment of the present invention, the following steps are performed: preparation of the light-transmitting substrate 1, formation of the transparent conductive film 2, formation of the first conductive layer 5 (formation of the base layer 3 and formation of the porous semiconductor layer 4), formation of the power generation layer 6, formation of the bonding layer 7, and formation of the second conductive layer 8. It should be noted that the methods for preparing the light-transmitting substrate 1, forming the transparent conductive film 2, forming the first conductive layer 5, forming the base layer 3, forming the porous semiconductor layer 4, and forming the power generation layer 6 are the same as those described in the above-mentioned sections on <Preparation of the light-transmitting substrate 1>, <Formation of the transparent conductive film 2>, <Formation of the first conductive layer 5> ([Formation of the base layer 3], [Formation of the porous semiconductor layer 4]), and <Formation of the power generation layer 6>, so they will not be repeated here. Hereinafter, only the methods for forming the bonding layer 7 and the second conductive layer 8 will be described.

[0170] <Forming of bonding layer 7 and second conductive layer 8>

[0171] After forming the power generation layer 6, a second conductive layer 8 is formed on the power generation layer 6 with a bonding layer 7 in between. In the manufacturing method of the photoelectric conversion element 200 of the modified embodiment of the present invention, the porous self-supporting sheet is stacked on the power generation layer 6 with at least one of the bonding surfaces of the power generation layer 6 and the porous self-supporting sheet in a state where a solvent or solution is present. As a result, it is possible to easily manufacture a photoelectric conversion element 200 with excellent photoelectric conversion efficiency.

[0172] As a solvent, examples include those listed in the section on "Formation of the Second Conductive Layer 8".

[0173] Furthermore, as the above-mentioned solution, an organic material solution can be cited as an example, formed by dissolving the organic material A constituting the above-mentioned bonding layer 7 in a poor solvent.

[0174] Furthermore, if a porous self-supporting sheet impregnated with the aforementioned solvent or solution is used, the solvent or solution can be well retained at the interface between the power generation layer 6 and at least one of the porous self-supporting sheet.

[0175] Here, a porous self-supporting sheet impregnated with a solvent or solution can be obtained, for example, by immersing the porous self-supporting sheet in the aforementioned solvent or solution and then lifting it out. In this case, there is no particular limitation on the immersion time; it can be set as appropriate depending on the type of solvent or solution used.

[0176] There are no particular limitations on the method for forming the bonding layer 7. However, from the viewpoint of efficiently manufacturing the photoelectric conversion element 200, it is preferable to impregnate the porous self-supporting sheet in an organic material solution containing organic material formed by dissolving the organic material A constituting the bonding layer 7 (such as PMMA as described above) in a poor solvent. After lifting the sheet, heating and drying are performed to form the bonding layer 7 on the porous self-supporting sheet. Then, the porous self-supporting sheet is bonded to the power generation layer 6 through the bonding layer 7. At this time, there are no particular limitations on the impregnation time, heating temperature, and drying time, which can be set as appropriate according to the type of organic material solution used. In order to prevent the influence caused by residue, it is preferable to use a poor solvent to dissolve the organic material A constituting the bonding layer 7. However, as long as drying can be performed in a way that does not change the power generation layer 6, it is not limited to a poor solvent, and various solvents can be used.

[0177] Furthermore, in the manufacturing method of the photoelectric conversion element 200 of the modified embodiment of the present invention, it is preferable to heat-press the porous self-supporting sheet stacked on the power generation layer 6. This allows for the acquisition of a photoelectric conversion element 200 with excellent integrity. Additionally, there are no particular limitations on the heating time, the pressure during heat pressing, or the pressing time; the heat pressing conditions described in the manufacturing method of the photoelectric conversion element 100 can also be used.

[0178] Based on the manufacturing method described above, it is possible to manufacture efficiently. Figure 2The photoelectric conversion element 200 is shown. Furthermore, the manufacturing method of the photoelectric conversion element in the modified embodiment of the present invention is not limited to the method described above; other steps besides those described above may be included without impairing the effects of the present invention.

[0179] Example

[0180] The present invention will now be specifically described based on embodiments, but the present invention is not limited to these embodiments. Furthermore, in the embodiments and comparative examples, the following methods were used to measure the perovskite layer's embedding within the fine pores of the porous self-supporting sheet and the cell performance of the fabricated perovskite solar cell.

[0181] <The perovskite layer is embedded within the pores of the porous self-supporting sheet>

[0182] The presence of the perovskite layer embedded within the pores of the porous self-supporting sheet was observed by examining its surface condition when it was peeled off from the sheet. Microscopic observation revealed that if unevenness was formed on the entire surface of the perovskite layer in contact with the porous self-supporting sheet, it was recorded as "present"—the perovskite layer was embedded within the pores. Conversely, if no unevenness was formed on the entire surface of the perovskite layer in contact with the porous self-supporting sheet, it was recorded as "absent"—the perovskite layer was not embedded within the pores.

[0183] <Battery Performance>

[0184] As the light source, a simulated solar illumination device (PEC-L11 type, manufactured by Peccell Technologies) with an AM1.5G filter installed at a 150W xenon lamp source was used. The light source was adjusted to 1 sun [AM1.5G, 100mW / cm²]. 2 (JISC8912 Class A)]. The fabricated perovskite solar cell was connected to a digital source meter (Model 2400 Source Meter, Keithley) to measure its current and voltage characteristics as follows.

[0185] Under 1 sun illumination, the output current was measured while the bias voltage was varied from -0.2V to 1.0V in 0.01V increments. The output current was measured by accumulating the values ​​between 0.1 and 0.2 seconds after each voltage step change.

[0186] Based on the above measurements of current and voltage characteristics, the short-circuit current density (mA / cm²) is calculated. 2 ), open voltage (V), form factor, and photoelectric conversion efficiency (%).

[0187] (Example 1)

[0188] Fabrication of Perovskite Solar Cells

[0189] The perovskite solar cell, which serves as a photoelectric conversion element, is manufactured in the following order.

[0190] Fabrication of a light-transmitting substrate with a transparent conductive film

[0191] A conductive glass substrate (manufactured by Sigma-Aldrich) on which a fluorine-doped tin oxide (FTO) film as a transparent conductive film is formed is prepared. A portion of the FTO film is removed by etching the conductive glass substrate. This yields a light-transmitting substrate with a transparent conductive film formed thereon (hereinafter referred to as "light-transmitting substrate with a transparent conductive film").

[0192] [Formation of the first conductive layer]

[0193] -Formation of the basal layer-

[0194] Using a spray pyrolysis method, a solution (manufactured by Sigma-Aldrich) of bis(acetylacetonate) diisopropyl titanate dissolved in isopropanol solution was sprayed onto the surface of an FTO film on a transparent substrate with a transparent conductive film. This formed a substrate layer (30 nm thick) of titanium dioxide on the FTO film. Next, a solution of titanium dioxide slurry (manufactured by Sigma-Aldrich) diluted with ethanol was prepared, and the resulting solution was applied to the surface of the substrate layer using a spin-coating method. The substrate was then heat-treated at 450°C for 30 minutes, thereby forming a porous semiconductor layer (120 nm thick) of titanium dioxide (TiO2), thus obtaining the first conductive layer.

[0195] [Formation of the power-generating layer]

[0196] A solution of N,N-dimethylformamide (DMF) containing 1.0 M lead iodide (PbI2) and 1.0 M methylammonium iodide (CH3NH3) was prepared as a precursor solution (1) containing a perovskite compound. While adding chlorobenzene dropwise, the obtained solution (1) was spin-coated onto the surface of the first conductive layer. Then, it was sintered at 100°C for 10 minutes, thereby forming a perovskite layer (450 nm thick) as the power generation layer. Thus, a pre-pressed laminate consisting of a transparent substrate with a transparent conductive film, a first conductive layer (substrate layer / porous semiconductor layer), and a power generation layer (perovskite layer) was obtained.

[0197] [Fabrication of porous self-supporting sheets]

[0198] Fabricate a porous self-supporting sheet containing a single layer of CNTs in the following order.

[0199] In a 500 mL aqueous solution of 2% sodium deoxycholate (DOC) as a dispersant, 1.0 g of carbon nanotubes (manufactured by Zeon Corporation, Japan, product name "ZEONANO SG101", monolayer CNT, average diameter: 3.5 nm, G / D ratio: 2.1, t-curve of unopened treatment is an upward convex curve) were added as fibrous carbon nanostructures containing monolayer CNTs, resulting in a coarse dispersion containing DOC as a dispersant. This coarse dispersion was then filled into a high-pressure homogenizer (manufactured by Meli-Kei Co., Ltd., product name "BERYUSYSTEM PRO") equipped with a multi-stage pressure control device (multi-stage pressure reducer) that applies back pressure during dispersion, and dispersed at a pressure of 100 MPa. Specifically, while applying back pressure, shear force was applied to the coarse dispersion to disperse the fibrous carbon nanostructures containing monolayer CNTs, resulting in a fibrous carbon nanostructure dispersion containing monolayer CNTs. In addition, during the dispersion process, the dispersion flowing out of the high-pressure homogenizer is returned to the high-pressure homogenizer and subjected to a 10-minute process.

[0200] 50 g of the prepared fibrous carbon nanostructure dispersion containing monolayer CNTs was added to a 200 mL beaker, followed by 50 g of distilled water to prepare a dispersion diluted two-fold. Filtration was then performed using a vacuum filtration apparatus equipped with a membrane filter at 0.09 MPa. After filtration, isopropanol and water were passed separately through the vacuum filtration apparatus to clean the carbon membrane formed on the membrane filter, followed by purging with air for 15 minutes. Next, the prepared carbon membrane / membrane filter was immersed in ethanol, and the carbon membrane was peeled off from the membrane filter to obtain carbon membrane (A).

[0201] The resulting carbon membrane (A) has the same size as the membrane filter, exhibits excellent film-forming properties, and maintains its state even after being peeled from the filter, demonstrating excellent self-support. The membrane density of the resulting carbon membrane (A) was measured, and the result was 0.85 g / cm³. 3 Based on these results, the carbon film (A) is a porous self-supporting sheet (A).

[0202] [Formation of the second conductive layer]

[0203] A porous self-supporting sheet (A) was immersed in chlorobenzene for 10 seconds, and then lifted out of the chlorobenzene to obtain a porous self-supporting sheet (1) impregnated with chlorobenzene. The porous self-supporting sheet (1) was stacked on a pre-pressed laminate heated on a heating plate at 100°C. The resulting laminate was then pressed from the porous self-supporting sheet (1) side under a pressure of 0.05 Pa (heat pressing) to obtain a perovskite solar cell formed by integrating the laminate. The obtained perovskite solar cell was used to evaluate and measure the "perovskite layer embedded in the pores of the porous self-supporting sheet" and the "cell performance". The results are shown in Table 1.

[0204] (Example 2)

[0205] To pretreat the porous self-supporting sheet, the porous self-supporting sheet (A) prepared in Example 1 was immersed in a solution (1) containing a perovskite compound precursor prepared in Example 1 for 10 seconds and then lifted to remove excess solution. Chlorobenzene was then dropped onto the surface of the porous self-supporting sheet (A) impregnated with the solution (1), and the sheet was dried at 80°C for 10 minutes to obtain a porous self-supporting sheet (2) with a perovskite compound attached. The obtained porous self-supporting sheet (2) was impregnated in chlorobenzene in the same manner as in Example 1 to obtain a porous self-supporting sheet (2) impregnated with chlorobenzene. Then, instead of the porous self-supporting sheet (1) impregnated with chlorobenzene, the porous self-supporting sheet (2) impregnated with chlorobenzene was laminated onto a pre-pressed laminate, and the same operations as in Example 1 were performed to obtain a perovskite solar cell. Various evaluations and measurements were performed using the obtained perovskite solar cell in the same manner as in Example 1. The results are shown in Table 1.

[0206] (Example 3)

[0207] An ethanolic solution containing 0.1 M methyl ammonium iodide (CH3NH3I) was prepared as solution (3).

[0208] To pretreat the porous self-supporting sheet, the porous self-supporting sheet (A) prepared in Example 1 was immersed in solution (3) for 10 seconds and then removed, and then dried at 80°C for 10 minutes to obtain a porous self-supporting sheet (3) with methyl ammonium iodide attached. The obtained porous self-supporting sheet (3) was immersed in chlorobenzene in the same way as in Example 1 to obtain a porous self-supporting sheet (3) impregnated with chlorobenzene. Then, instead of the porous self-supporting sheet (1) impregnated with chlorobenzene, the porous self-supporting sheet (3) impregnated with methyl ammonium iodide (MAI) was laminated onto the pre-pressed laminate, and the same operation as in Example 1 was performed to obtain a perovskite solar cell. Various evaluations and measurements were performed using the obtained perovskite solar cell in the same way as in Example 1. The results are shown in Table 1.

[0209] (Example 4)

[0210] A chlorobenzene solution containing 1.0 M methylammonium iodide (CH4NH3I) was prepared as solution (4). The porous self-supporting sheet (A) prepared in Example 1 was immersed in solution (4) for 10 seconds and then lifted out, thus obtaining a porous self-supporting sheet (4) impregnated with solution (4). Instead of the porous self-supporting sheet (1) impregnated with chlorobenzene, the porous self-supporting sheet (4) impregnated with solution (4) was stacked on the pre-pressed laminate, and the same operation as in Example 1 was performed to obtain a perovskite solar cell. Various evaluations and measurements were performed using the obtained perovskite solar cell in the same manner as in Example 1. The results are shown in Table 1.

[0211] (Example 5)

[0212] A porous self-supporting sheet (B) with a film thickness of 1 μm, prepared using the same method as in Example 1, was used instead of the porous self-supporting sheet (A) prepared in Example 1. Otherwise, the same procedures as in Example 1 were performed to obtain a perovskite solar cell. Various evaluations and measurements were performed using the obtained perovskite solar cell in the same manner as in Example 1. The results are shown in Table 1.

[0213] (Comparative Example 1)

[0214] A sheet (C) with a film thickness of 0.1 μm, prepared using the same method as in Example 1, was used instead of the porous self-supporting sheet (A) prepared in Example 1. Otherwise, the same operations as in Example 1 were performed to obtain a perovskite solar cell. However, when the sheet (C) was immersed in chlorobenzene, the sheet (C) broke, making it impossible to fabricate a perovskite solar cell.

[0215] (Comparative Example 2)

[0216] Instead of the porous self-supporting sheet (1) impregnated with chlorobenzene, a porous self-supporting sheet (A) without chlorobenzene impregnation was laminated onto the pre-pressed laminate. Otherwise, the same operation as in Example 1 was performed to obtain a perovskite solar cell. However, it was not possible to attach the porous self-supporting sheet (A) to the power generation layer of the pre-pressed laminate to integrate it, and a perovskite solar cell could not be obtained.

[0217] [Table 1]

[0218]

[0219] (Example 6)

[0220] Perform the same operation as in Example 1 to obtain a light-transmitting substrate with a transparent conductive film, a first conductive layer (base layer / porous semiconductor layer), a power generation layer, and a porous self-supporting sheet.

[0221] [Formation of the bonding layer]

[0222] A solution (10) containing polymethyl methacrylate (hereinafter referred to as "PMMA") and chlorobenzene is prepared as an organic material solution.

[0223] In order to pretreat the porous self-supporting sheet, the porous self-supporting sheet (A) was immersed in the solution (10) obtained as described above for 30 seconds and then lifted out, and then dried at a temperature of 80°C for 2 minutes to obtain a porous self-supporting sheet (10) with a layer (bonding layer) formed of PMMA.

[0224] [Formation of the second conductive layer]

[0225] A porous self-supporting sheet (10) was immersed in chlorobenzene for 10 seconds and then lifted to obtain a porous self-supporting sheet (10) impregnated with chlorobenzene. The porous self-supporting sheet (10) was stacked on a pre-pressed laminate heated on a heating plate at 100°C with the power generation layer facing the PMMA layer (bonding layer) and pressed from the porous self-supporting sheet (10) side at a pressure of 0.05 MPa (heat pressing) to obtain a perovskite solar cell. The performance of the obtained perovskite solar cell was measured. The results are shown in Table 2.

[0226] (Example 7)

[0227] A solution (20) containing PMMA and anisole was prepared as an organic material solution.

[0228] To pretreat the porous self-supporting sheet, the porous self-supporting sheet (A) was immersed in the solution (20) obtained as described above for 30 seconds and then removed. It was then dried at 80°C for 2 minutes to obtain a porous self-supporting sheet (20) with a layer (bonding layer) formed of PMMA. The obtained porous self-supporting sheet (20) was immersed in chlorobenzene in the same manner as in Example 6 to obtain a porous self-supporting sheet (20) impregnated with chlorobenzene. Instead of the porous self-supporting sheet (10) impregnated with chlorobenzene, the porous self-supporting sheet (20) impregnated with chlorobenzene was laminated onto a pre-pressing laminate. Except as in Example 6, heat pressing was performed to obtain a perovskite solar cell. The obtained perovskite solar cell was measured in the same manner as in Example 6. The results are shown in Table 2.

[0229] (Example 8)

[0230] A solution (30) containing PMMA and chlorobenzene was prepared as an organic material solution.

[0231] The porous self-supporting sheet (A) was immersed in the solution (30) obtained as described above for 30 seconds to obtain a porous self-supporting sheet (30) impregnated with solution (30). The porous self-supporting sheet (30) impregnated with solution (30) was laminated onto a pre-pressed laminate heated on a heating plate at 100°C. Except as in Example 6, heating and pressing were performed to form a layer (bonding layer) made of PMMA between the power generation layer and the porous self-supporting sheet (30) to obtain a perovskite solar cell. The obtained perovskite solar cell was measured in the same manner as in Example 6. The results are shown in Table 2.

[0232] (Example 9)

[0233] A porous self-supporting sheet (B) with a film thickness of 1 μm, prepared by the same method as in Example 6, was used instead of the porous self-supporting sheet (A) prepared in Example 6.

[0234] The same operation as in Example 6 was performed using the obtained porous self-supporting sheet (B), thereby obtaining a porous self-supporting sheet (40) with a layer (bonding layer) made of PMMA.

[0235] A porous self-supporting sheet (40) was stacked on a pre-pressed laminate heated on a heating plate at 100°C with the power generation layer facing the PMMA layer (bonding layer). Chlorobenzene was dropped onto the surface of the porous self-supporting sheet (40), and then heated and pressed in the same manner as in Example 6 to obtain a perovskite solar cell. The obtained perovskite solar cell was measured in the same manner as in Example 6. The results are shown in Table 2.

[0236] (Comparative Example 3)

[0237] A sheet (C) with a film thickness of 0.1 μm, prepared using the same method as in Example 9, was used instead of the porous self-supporting sheet (B) prepared in Example 9. Then, the fabrication of a perovskite solar cell was attempted in the same manner as in Example 9; however, during the pretreatment of the sheet (C), i.e., when immersing the sheet (C) in the solution (10), the sheet (C) broke. Therefore, it was impossible to fabricate a perovskite solar cell.

[0238] (Comparative Example 4)

[0239] By not impregnating the porous self-supporting sheet (10) with chlorobenzene, and instead stacking the porous self-supporting sheet (10) without chlorobenzene impregnation onto the pre-pressing laminate, the perovskite solar cell was fabricated in the same manner as in Example 6. However, the porous self-supporting sheet (A) could not be adhered to the pre-pressing laminate, and a perovskite solar cell could not be obtained.

[0240] [Table 2]

[0241]

[0242] In Tables 1 and 2,

[0243] "FTO" indicates fluorine-doped tin oxide.

[0244] "MAI" stands for methylammonium iodide.

[0245] “CB” represents chlorobenzene.

[0246] "PMMA" stands for polymethyl methacrylate.

[0247] As can be seen from the results shown in Tables 1 and 2, perovskite solar cells with excellent photoelectric conversion efficiency can be manufactured according to the methods of Examples 1 to 9.

[0248] Industrial availability

[0249] The present invention provides a photoelectric conversion element that exhibits excellent photoelectric conversion efficiency and is easy to manufacture, as well as a method for manufacturing the photoelectric conversion element.

[0250] Explanation of reference numerals in the attached figures

[0251] 1: Transparent substrate;

[0252] 2: Transparent conductive film;

[0253] 3: Basal layer;

[0254] 4: Porous semiconductor layer;

[0255] 5: First conductive layer;

[0256] 6: Power generation layer;

[0257] 7: Bonding layer;

[0258] 8: Second conductive layer (porous self-supporting sheet)

[0259] 100, 200: Photoelectric conversion elements.

Claims

1. A photoelectric conversion element, which is integrally formed by a laminate having a light-transmitting substrate, a transparent conductive film, a first conductive layer, a power-generating layer and a second conductive layer in sequence. The power generation layer contains perovskite compounds. The second conductive layer is composed of a porous self-supporting sheet containing at least a single layer of carbon nanotubes. At least a portion between the power generation layer and the second conductive layer has a bonding layer. The bonding layer is composed of organic materials and has a different composition and properties from the power generation layer and the second conductive layer. The organic material is a polymer material exhibiting adhesive properties and / or a polymer material exhibiting semiconductor properties. The bonding layer is formed by immersing the porous self-supporting sheet in an organic material solution formed by dissolving the organic material in a poor solvent, then lifting it out and heating and drying it, thereby forming the bonding layer on the porous self-supporting sheet. The porous self-supporting sheet is then bonded to the power generation layer through the bonding layer. The term "undesirable solvent" refers to a solvent in which the perovskite compound does not undergo any changes during the manufacturing process.

2. The photoelectric conversion element according to claim 1, wherein, The porous self-supporting sheet contains the organic material.

3. The photoelectric conversion element according to claim 1 or 2, wherein, The thickness of the porous self-supporting sheet is 20 μm or more.

4. The photoelectric conversion element according to claim 1 or 2, wherein, The average diameter (Av) of the monolayer carbon nanotubes and the standard deviation (σ) of the diameter satisfy the following relationship: 0.20 < (3σ / Av) < 0.

60.

5. The photoelectric conversion element according to claim 1 or 2, wherein, The t-curve of the monolayer carbon nanotube, obtained from the adsorption isotherm, exhibits an upwardly convex shape.

6. The photoelectric conversion element according to claim 1 or 2, wherein, The first conductive layer comprises metal oxides and / or organic compounds.

Images