Photoelectric conversion element

Abstract

A photoelectric conversion element (100) is obtained by integrally forming a laminate that includes a light transmissive substrate (1), a transparent conductive film (2), a first conductive layer (5), a power generation layer (6), and a second conductive layer (7) in the state order. The second conductive layer (7) comprises a porous layer (4) including at least a carbon nanofiber body. A high molecular weight layer (8) formed of a polymer having a weight average molecular weight of 20,000-200,000 is provided between the power generation layer (6) and the second conductive layer (7).

Description

photoelectric conversion element

[0001] The present invention relates to a photoelectric conversion element.

[0002] Solar cells have attracted attention as photoelectric conversion elements that convert light energy into electricity. There are various types of solar cells, such as perovskite solar cells that use a perovskite compound as a power generation layer.

[0003] For example, Patent Document 1 proposes a photoelectric conversion element including: a first electrode; a second electrode including a substrate including a plurality of structures including carbon and a first material portion provided between the plurality of structures and including a carrier transport material; a photoelectric conversion layer provided between the first electrode and the second electrode and including a material having a perovskite structure; and a first layer provided between the photoelectric conversion layer and the second electrode and including a carrier transport material.

[0004] Patent No. 6339037

[0005] However, conventional photoelectric conversion elements have room for improvement in terms of structural stability.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photoelectric conversion element that is excellent in structural stability.

[0007] The photoelectric conversion element of the present invention is a photoelectric conversion element formed by integrating a laminate including a light-transmitting substrate, a transparent conductive film, a first conductive layer, a power generation layer, and a second conductive layer in this order, wherein the second conductive layer is a porous layer containing at least carbon nanofibers, and a polymer layer having a weight-average molecular weight of 20,000 to 200,000 is provided between the power generation layer and the second conductive layer. This configuration makes it possible to provide a photoelectric conversion element with excellent structural stability.

[0008] In the photoelectric conversion element of the present invention, the polymer is preferably a hydrogenated polymer, which can further improve the structural stability of the photoelectric conversion element.

[0009] In the photoelectric conversion element of the present invention, the polymer is preferably a polymer having a hydrogenated aromatic or diene skeleton in the main chain, which can further improve the structural stability of the photoelectric conversion element.

[0010] In the photoelectric conversion element of the present invention, the polymer is preferably at least one selected from the group consisting of a hydrogenated aromatic vinyl compound-conjugated diene block copolymer and a hydrogenated aromatic vinyl compound-conjugated diene block copolymer modified with a silicon atom-containing polar group. This configuration can further improve the structural stability of the photoelectric conversion element.

[0011] In the photoelectric conversion element of the present invention, the hydrogenated aromatic vinyl compound-conjugated diene block copolymer preferably has a structure in which both the non-aromatic carbon-carbon unsaturated bond and the aromatic carbon-carbon unsaturated bond are hydrogenated. This configuration can further improve the structural stability of the photoelectric conversion element.

[0012] In the photoelectric conversion element of the present invention, the second conductive layer is preferably made of a porous self-supporting sheet. Such a configuration makes it possible to facilitate the production of the photoelectric conversion element and further improve the structural stability.

[0013] In the present invention, the term "porous free-standing sheet" refers to a sheet having a plurality of pores formed therein, which maintains its shape even without a support. The porous free-standing sheet used in the present invention maintains its shape without tearing even when the porous free-standing sheet is immersed in a predetermined solvent or solution, pulled out, and then attached to an object to be attached. Furthermore, the porous free-standing sheet used in the present invention does not tear or deform even when, for example, chlorobenzene, which is a poor solvent for perovskite compounds, is dropped onto the sheet or when it is handled using a jig for attaching the sheet. The porous free-standing sheet used in the present invention has a thickness of 1 μm to 200 μm and an area of ​​1 mm. 2 ~100cm 2It is preferable that the sheet maintains its shape without a support at this size.

[0014] In the photoelectric conversion element of the present invention, the porous free-standing sheet preferably has a thickness of 20 μm or more. Such a configuration facilitates the production of the photoelectric conversion element and can further improve the structural stability.

[0015] In the photoelectric conversion element of the present invention, the power generation layer preferably contains a perovskite compound. This configuration reduces the manufacturing cost of the photoelectric conversion element and improves the ease of manufacturing the photoelectric conversion element.

[0016] In the photoelectric conversion element of the present invention, the carbon nanofiber material preferably has an average diameter (Av) and a standard deviation (σ) of the diameters that satisfy the following relationship: 0.20<(3σ / Av)<0.60. This configuration can further improve the structural stability of the photoelectric conversion element.

[0017] The "average diameter (Av) of carbon nanofiber bodies" and the "standard deviation of the diameters of carbon nanofiber bodies (σ: standard deviation)" can each be determined by measuring the diameters (outer diameters) of 100 randomly selected carbon nanofiber bodies using a transmission electron microscope. The average diameter (Av) and standard deviation (σ) of the carbon nanofiber bodies may be adjusted by changing the manufacturing method or manufacturing conditions of the carbon nanofiber bodies, or by combining multiple types of carbon nanofiber bodies obtained by different manufacturing methods.

[0018] In the photoelectric conversion element of the present invention, the carbon nanofiber material preferably exhibits an upwardly convex t-plot obtained from an adsorption isotherm, which can further improve the structural stability of the photoelectric conversion element.

[0019] Furthermore, the photoelectric conversion element of the present invention is preferably produced by a method including the steps of: laminating the polymer layer on the power generation layer; and then laminating the porous free-standing sheet on the polymer layer while maintaining a solvent on at least one bonding surface between the porous free-standing sheet that will become the second conductive layer and the polymer layer. With this configuration, a photoelectric conversion element that is easy to produce and has excellent structural stability can be easily produced.

[0020] Furthermore, the photoelectric conversion element of the present invention is preferably produced by a method including a step of laminating the porous free-standing sheet to the power generation layer in a state in which at least one bonding surface between the porous free-standing sheet to be the second conductive layer and the power generation layer retains a solution in which a polymer for forming the polymer layer is dissolved. With this configuration, a photoelectric conversion element that is easy to produce and has excellent structural stability can be easily produced.

[0021] According to the present invention, it is possible to provide a photoelectric conversion element having excellent structural stability.

[0022] 1 is a cross-sectional view schematically showing the configuration of a photoelectric conversion element according to one embodiment of the present invention.

[0023] The photoelectric conversion element of the present invention is not particularly limited and can be used, for example, as a perovskite solar cell. One embodiment of the photoelectric conversion element of the present invention will be described in detail below with reference to FIG.

[0024] (Photoelectric Conversion Element) Figure 1 is a cross-sectional view schematically illustrating the configuration of a photoelectric conversion element 100 according to one embodiment of the present invention. The photoelectric conversion element 100 is formed by integrating a laminate including, in this order: a light-transmitting substrate 1; a transparent conductive film 2; a first conductive layer 5 consisting of an underlayer 3 and a porous semiconductor layer 4; a power generation layer 6; and a second conductive layer 7. The second conductive layer 7 is formed of a porous free-standing sheet serving as a porous layer containing at least carbon nanofibers, and a polymer layer 8 consisting of a polymer having a weight-average molecular weight of 20,000 or more and 200,000 or less is provided between the power generation layer 6 and the second conductive layer 7. Each of the components constituting the photoelectric conversion element 100 will be described below in order.

[0025] <Light-Transmitting Substrate 1> The light-transmitting substrate 1 constitutes a base of the photoelectric conversion element 100. The light-transmitting substrate 1 is not particularly limited, and examples thereof include a substrate made of glass or synthetic resin, and a film made of synthetic resin.

[0026] Examples of the glass that constitutes the light-transmitting substrate 1 include inorganic glass such as soda glass.

[0027] Examples of synthetic resins that can be used to form the light-transmitting substrate 1 include polyacrylic resin, polycarbonate resin, polyester resin, polyimide resin, polystyrene resin, polyvinyl chloride resin, polyamide resin, and polycycloolefin resin. Among these, from the viewpoint of obtaining a thin, lightweight, and flexible photoelectric conversion element 100, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferred synthetic resins.

[0028] The thickness of the light-transmitting substrate 1 is not particularly limited as long as it can maintain its shape as a substrate. The thickness of the light-transmitting substrate 1 can be, for example, 0.1 mm or more and 10 mm or less.

[0029] <Transparent conductive film 2> The transparent conductive film 2 is a film made of a metal oxide formed on the surface of the light-transmitting substrate 1. By providing the transparent conductive film 2, it is possible to impart conductivity to the surface of the light-transmitting substrate 1.

[0030] 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). While the photoelectric conversion element 100 shown in FIG. 1 has one transparent conductive film 2 on the translucent substrate 1, two or more transparent conductive films 2 may be provided on the translucent substrate 1. When the photoelectric conversion element 100 has two or more transparent conductive films 2, the respective transparent conductive films may be made of the same metal oxide or different metal oxides.

[0031] The thickness of the transparent conductive film 2 is not particularly limited as long as it can impart the desired conductivity to the light-transmitting substrate 1, and can be, for example, 1 nm or more and 1 μm or less. The transparent conductive film 2 may be formed on the entire surface of the light-transmitting substrate 1, or may be formed on only a part of the surface of the light-transmitting substrate 1, as shown in FIG.

[0032] <First conductive layer 5> The first conductive layer 5 is a layer that functions as a charge transport layer and is made of an n-type semiconductor. In this embodiment, the first conductive layer 5 is made of two layers, the underlayer 3 and the porous semiconductor layer 4, but is not limited to this, and the first conductive layer 5 may be a single layer made of an n-type semiconductor.

[0033] <Underlayer 3> The underlayer 3 is an optional layer. By providing the underlayer 3, the light-transmitting substrate 1 and the transparent conductive film 2 are prevented from coming into direct contact with the porous semiconductor layer 4. This prevents loss of electromotive force, thereby improving the photoelectric conversion efficiency of the photoelectric conversion element 100.

[0034] The underlayer 3 may be a porous film or a dense film, for example, as long as it is made of an n-type semiconductor. However, from the viewpoint of sufficiently preventing the light-transmitting substrate 1 and the transparent conductive film 2 from contacting the porous semiconductor layer 4, the underlayer 3 is preferably a non-porous dense film. The thickness of the underlayer 3 is not particularly limited, and may be, for example, 1 nm or more and 500 nm or less. Furthermore, the underlayer 3 may optionally contain an insulating material other than an n-type semiconductor in a proportion that does not impair the properties of the underlayer 3 as an n-type semiconductor.

[0035] <Porous Semiconductor Layer 4> The porous semiconductor layer 4 is a porous layer. When the first conductive layer 5 includes the porous semiconductor layer 4, the photoelectric conversion efficiency of the photoelectric conversion element 100 can be further improved.

[0036] The thickness of the porous semiconductor layer 4 is not particularly limited, but is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 100 nm or less. The porous semiconductor layer 4 may be formed from a single layer as shown in Figure 1, or may be formed from multiple layers.

[0037] <Power generation layer 6> The power generation layer 6 is a layer made of a material that generates electromotive force by absorbing light, and is preferably a layer containing a perovskite compound, and more preferably a layer made of a perovskite compound (perovskite layer).

[0038] The perovskite compound constituting the power generation layer 6 is not particularly limited, and any known perovskite compound can be used. Specific examples include lead-based perovskite compounds such as CH3NH3PbI3, CH3NH3PbBr3, (CH3(CH2)nCHCH3NH3)2PbI4 [n = 5 to 8], and (C6H5C2H4NH3)2PbBr4, as well as lead-free perovskite compounds. The perovskite compound constituting the power generation layer 6 is not limited to lead-based or lead-free perovskite compounds, and any compound that forms a perovskite structure and functions as a power generation layer can be used.

[0039] 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, and is preferably 1 μm or less, 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.

[0040] <Second conductive layer 7> The second conductive layer 7 is a layer made of a porous layer containing at least carbon nanofibers. Here, the carbon nanofibers contained in the second conductive layer 7 are not particularly limited, but preferably contain carbon nanotubes (hereinafter, carbon nanotubes may also be referred to as "CNTs"), and the CNTs contained in the second conductive layer 7 preferably contain single-walled CNTs. With this configuration, the photoelectric conversion efficiency of the photoelectric conversion element 100 can be increased.

[0041] The second conductive layer 7 is preferably a layer made of a porous free-standing sheet. The use of a porous free-standing sheet, which is a free-standing film, can improve the shape stability of the second conductive layer 7 and facilitate the easy manufacture of the photoelectric conversion element 100, thereby making it easy to increase the area of ​​the photoelectric conversion element 100. Furthermore, the use of a porous free-standing sheet allows for easy drying of the solvent or solution when wet processing is performed. The porous free-standing sheet must contain at least carbon nanofibers, preferably containing at least single-walled CNTs as the carbon nanofibers, more preferably a sheet made of carbon nanofibers, more preferably a sheet made of single-walled CNTs, and even more preferably a sheet made of buckypaper. The use of a porous free-standing sheet containing carbon nanofibers with at least P-type semiconductor properties can impart to the second conductive layer 7 the functions of both an excellent hole transport layer and a collecting electrode.

[0042] The carbon nanofiber materials contained in the second conductive layer 7 (more preferably a porous self-standing sheet) preferably include carbon nanofiber materials (more preferably CNTs, more preferably single-walled CNTs) having the following properties:

[0043] -(3σ / Av)- The carbon nanofiber materials contained in second conductive layer 7 preferably have a ratio (3σ) of the standard deviation (σ) of diameters multiplied by 3 to the average diameter (Av) of the carbon nanofiber materials, which is greater than 0.20, more preferably greater than 0.25, even more preferably greater than 0.50, and preferably less than 0.60. When 3σ / Av is greater than 0.20 and less than 0.60, even if the amount of carbon nanofiber materials contained in second conductive layer 7 is small, second conductive layer 7 can be provided with a sufficient function as a hole transport layer and a sufficient function as a current collecting electrode.

[0044] - Average Diameter (Av) of Carbon Nanofibers - The average diameter (Av) of the carbon nanofibers is preferably 0.5 nm or more, more preferably 1 nm or more, and preferably 15 nm or less, and more preferably 10 nm or less. When the average diameter (Av) of the carbon nanofibers is 0.5 nm or more, aggregation of the carbon nanofibers can be suppressed, and the dispersibility of the carbon nanofibers in the second conductive layer 7 can be increased. Furthermore, when the average diameter (Av) of the carbon nanofibers is 15 nm or less, the second conductive layer 7 can fully function as a collecting electrode.

[0045] -t-plot- It is preferable that the carbon nanofiber material exhibits an upwardly convex t-plot obtained from the adsorption isotherm. Such carbon nanofiber material is more preferably single-walled CNT that has not been subjected to an aperture treatment. If a carbon nanofiber material exhibiting an upwardly convex t-plot obtained from the adsorption isotherm is used, a second conductive layer 7 having excellent strength can be obtained.

[0046] The bending point of the t-plot of the carbon nanofiber material is preferably in the range satisfying 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.

[0047] Measurement of the adsorption isotherm of the carbon nanofiber material, creation of the t-plot, and analysis of the t-plot can be performed using, for example, a commercially available measuring device, "BELSORP (registered trademark)-mini" (manufactured by BEL Japan Co., Ltd.).

[0048] Carbon nanofibers having the properties described above can be efficiently produced, for example, by a method in which a raw material compound and a carrier gas are supplied onto a substrate having a catalyst layer for producing carbon nanofibers on its surface, and the carbon nanofibers are synthesized by chemical vapor deposition (CVD), in which the catalytic activity of the catalyst layer is dramatically improved by the presence of a trace amount of oxidant (catalytic activator) in the system (super growth method; see WO 2006 / 011655), and the catalyst layer is formed on the substrate surface by a wet process.

[0049] In particular, from the viewpoint of easily obtaining a second conductive layer 7 with a large thickness, it is preferable to use a carbon nanofiber material obtained by the super-growth method as the carbon nanofiber material.

[0050] Furthermore, the second conductive layer 7 preferably contains, inside the second conductive layer 7, the material (e.g., perovskite compound) that constitutes the power generation layer 6. More specifically, the second conductive layer 7 preferably contains, inside the multiple pores of the second conductive layer 7, the material (e.g., perovskite compound) that constitutes the power generation layer 6.

[0051] The proportion of carbon nanofibers contained in the second conductive layer 7 is not particularly limited, but is preferably 50% by mass or more, and more preferably 75% by mass or more.

[0052] Furthermore, materials other than carbon nanofibers that may be optionally contained in second conductive layer 7 include, for example, organic materials and inorganic materials that serve as p-type semiconductors.

[0053] Here, examples of organic materials that can be contained in the second conductive layer 7 include 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-MeOTAD), poly(3-hexylthiophene) (P3HT), and polytriallylamine (PTAA).

[0054] Furthermore, examples of inorganic materials that can be contained in the second conductive layer 7 include CuI, CuSCN, CuO, and Cu2O.

[0055] The thickness of the second conductive layer 7 is preferably 20 μm or more, more preferably 30 μm or more, and is preferably 200 μm or less, and more preferably 80 μm or less. When the thickness of the second conductive layer 7 is 20 μm or more and 200 μm or less, the second conductive layer 7 can exhibit a more excellent function as a collecting electrode.

[0056] <<Method for Manufacturing Second Conductive Layer 7>> The method for manufacturing the second conductive layer 7 is not particularly limited, and for example, it is possible to employ a method including a step (film formation step) of removing the solvent from a carbon nanofiber dispersion containing carbon nanofibers, a dispersant, and a solvent to form the second conductive layer 7. Furthermore, the method for manufacturing the second conductive layer 7 may optionally include a step (dispersion preparation step) of preparing the carbon nanofiber dispersion by dispersing a crude dispersion containing carbon nanofibers, a dispersant, and a solvent prior to the film formation step.

[0057] Dispersion Preparation Step In the dispersion preparation step, a crude dispersion containing carbon nanofibers, a dispersant, and a solvent is preferably subjected to a dispersion treatment that produces a cavitation effect or a disintegration effect, as described below in detail, but is not particularly limited thereto, to disperse the carbon nanofibers and prepare a carbon nanofiber dispersion. By performing a dispersion treatment that produces a cavitation effect or a disintegration effect in this manner, a carbon nanofiber dispersion in which the carbon nanofibers are well dispersed can be obtained. Furthermore, by producing the second conductive layer 7 using a carbon nanofiber dispersion in which the carbon nanofibers are well dispersed, the carbon nanofibers can be uniformly dispersed, resulting in a second conductive layer 7 with excellent properties such as electrical conductivity, thermal conductivity, and mechanical properties. The carbon nanofiber dispersion used to produce the second conductive layer 7 may also be prepared by dispersing carbon nanofibers in a solvent using a known dispersion treatment other than the above.

[0058] The carbon nanofibers used to prepare the carbon nanofiber dispersion preferably contain single-walled CNTs, and may be a mixture of single-walled CNTs and carbon nanofibers other than single-walled CNTs (for example, multi-walled CNTs).

[0059] Here, the carbon nanofiber dispersion liquid can have a content ratio of single-walled CNT to carbon nanofibers other than single-walled CNT of, for example, a mass ratio (single-walled CNT / carbon nanofibers other than single-walled CNT) of 50 / 50 to 75 / 25.

[0060] Dispersant The dispersant used in preparing the carbon nanofiber dispersion is not particularly limited as long as it can disperse carbon nanofibers and can dissolve in the solvent used in preparing the carbon nanofiber dispersion. Examples of such dispersants that can be used include surfactants, synthetic polymers, and natural polymers.

[0061] Examples of surfactants include sodium dodecyl sulfonate, sodium deoxycholate, sodium cholate, and sodium dodecylbenzenesulfonate.

[0062] Furthermore, examples of synthetic polymers include polyether diols, polyester diols, polycarbonate diols, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, acetal group-modified polyvinyl alcohol, butyral group-modified polyvinyl alcohol, silanol group-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resins, epoxy resins, modified epoxy resins, phenoxy resins, modified phenoxy resins, phenoxy ether resins, phenoxy ester resins, fluorine-based resins, melamine resins, alkyd resins, phenolic resins, polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.

[0063] Further, examples of natural polymers include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, and cellulose, as well as salts or derivatives thereof, where derivatives refer to conventionally known compounds such as esters and ethers.

[0064] These dispersants can be used alone or in combination of two or more. Among them, surfactants are preferred as dispersants because they have excellent dispersibility for carbon nanofiber materials, and sodium deoxycholate is more preferred.

[0065] =Solvent= The solvent for the carbon nanofiber dispersion is not particularly limited and examples thereof include water, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as diethyl ether, dioxane, and tetrahydrofuran, amide-based polar organic solvents such as N,N-dimethylformamide and N-methylpyrrolidone, and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene. These solvents may be used alone or in combination of two or more.

[0066] In the dispersion liquid preparation step, it is preferable to carry out a dispersion treatment that can obtain, for example, the cavitation effect or the disintegration effect described below.

[0067] Dispersion treatment that produces a cavitation effect Dispersion treatment that produces a cavitation effect is a dispersion method that utilizes shock waves generated when vacuum bubbles generated in water burst when high energy is applied to the liquid. By using this dispersion method, carbon nanofibers can be dispersed well.

[0068] Specific examples of dispersion treatments that can achieve the cavitation effect include dispersion treatment using ultrasonic waves, dispersion treatment using a jet mill, and dispersion treatment using high-shear stirring. These dispersion treatments may be performed alone or in combination. More specifically, for example, ultrasonic homogenizers, jet mills, and high-shear stirring devices are preferably used. These devices may be conventionally known.

[0069] When an ultrasonic homogenizer is used to disperse carbon nanofiber materials, the coarse dispersion liquid is irradiated with ultrasonic waves using the ultrasonic homogenizer. The irradiation time can be appropriately set depending on the amount of carbon nanofiber materials, and is, 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. Furthermore, for example, the output is preferably 20 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and the temperature is preferably 15°C or more and 50°C or less.

[0070] Furthermore, when a jet mill is used, the number of times of treatment may be appropriately set depending on the amount of carbon nanofiber material, etc., and is, for example, preferably 2 times or more, more preferably 5 times or more, and preferably 100 times or less, more preferably 50 times or less. Furthermore, 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.

[0071] Furthermore, when high shear stirring is used, the coarse dispersion liquid is stirred and sheared by a high shear stirring device. The faster the rotation speed, the better. For example, the operating time (the time the machine is rotating) is preferably 3 minutes to 4 hours, the peripheral speed is preferably 5 m / s to 50 m / s, and the temperature is preferably 15°C to 50°C.

[0072] The dispersion treatment that produces the above-mentioned cavitation effect is preferably carried out at a temperature of 50° C. or less, because this suppresses changes in concentration due to evaporation of the solvent.

[0073] Dispersion treatment that produces a disintegration effect Not only can the carbon nanofiber body be uniformly dispersed in the solvent, but it is also more advantageous than the dispersion treatment that produces the cavitation effect described above in that it can suppress damage to the carbon nanofiber body caused by shock waves when the bubbles disappear.

[0074] In the dispersion process that produces this disintegration effect, shear force is applied to the crude dispersion to disintegrate and disperse the agglomerates of carbon nanofibers, and then back pressure is applied to the crude dispersion, and if necessary, the crude dispersion is cooled, thereby suppressing the generation of bubbles and uniformly dispersing the carbon nanofibers in the solvent.

[0075] When a back pressure is applied to the crude dispersion, the back pressure applied to the crude dispersion may be reduced to atmospheric pressure in one go, but it is preferable to reduce the pressure in multiple stages.

[0076] - Film formation process - In the film formation process, the solvent is removed from the carbon nanofiber dispersion described above to form second conductive layer 7. Specifically, in the film formation process, the solvent is removed from the carbon nanofiber dispersion using, for example, either the following method (A) or (B) to form a porous free-standing sheet that will become second conductive layer 7. (A) A method in which the carbon nanofiber dispersion is applied to a film formation substrate, and the applied carbon nanofiber dispersion is then dried. (B) A method in which the carbon nanofiber dispersion is filtered using a porous film formation substrate, and the obtained filtrate is then dried.

[0077] [Film-forming substrate] The film-forming substrate is not particularly limited, and any known substrate can be used.

[0078] Specifically, examples of the film-forming substrate onto which the carbon nanofiber dispersion is applied in method (A) include resin substrates and glass substrates. Examples of resin substrates include substrates made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, polymethyl methacrylate, alicyclic acrylic resin, cycloolefin resin, triacetyl cellulose, etc. Examples of glass substrates include substrates made of ordinary soda glass.

[0079] In the method (B), examples of the film-forming substrate for filtering the carbon nanofiber dispersion include filter paper and porous sheets made of cellulose, nitrocellulose, alumina, and the like.

[0080] [Coating] In the method (A), the carbon nanofiber dispersion can be applied to the film-forming substrate by a known coating method, such as dipping, roll coating, gravure coating, knife coating, air knife coating, roll knife coating, die coating, screen printing, spray coating, or gravure offset.

[0081] [Filtration] In the above method (B), the carbon nanofiber dispersion can be filtered using a film-forming substrate by any known filtration method, such as natural filtration, reduced pressure filtration, pressure filtration, or centrifugal filtration.

[0082] [Drying] A known drying method can be used to dry the carbon nanofiber dispersion applied to the film-forming substrate in the above method (A) or the filtered product obtained in the above method (B). Examples of drying methods include hot air drying, vacuum drying, hot roll drying, and infrared irradiation. The drying temperature is not particularly limited, but is usually room temperature to 200°C, and the drying time is not particularly limited, but is usually 0.1 to 150 minutes.

[0083] [Post-treatment] The porous free-standing sheet formed as described above typically contains the components contained in the carbon nanofiber dispersion, such as carbon nanofibers and dispersant, in the same proportions as in the carbon nanofiber dispersion. Therefore, in the method for producing the second conductive layer 7, the porous free-standing sheet formed in the film formation step may optionally be washed to remove the dispersant from the porous free-standing sheet. Removing the dispersant from the porous free-standing sheet can further improve the properties of the porous free-standing sheet, such as its conductivity.

[0084] The porous free-standing sheet can be washed by contacting it with a solvent capable of dissolving the dispersant and dissolving the dispersant in the porous free-standing sheet into the solvent. The solvent capable of dissolving the dispersant in the porous free-standing sheet is not particularly limited, and the solvents described above that can be used as solvents for carbon nanofiber dispersions, preferably the same solvents as those for carbon nanofiber dispersions, can be used. The contact between the porous free-standing sheet and the solvent can be achieved by immersing the porous free-standing sheet in the solvent or by applying the solvent to the porous free-standing sheet. After washing, the porous free-standing sheet can be dried using a known method.

[0085] Furthermore, in producing the porous free-standing sheet, the porous free-standing sheet formed in the film formation step may be optionally subjected to press processing to further increase the density, etc., to adjust the voids as needed. From the viewpoint of suppressing deterioration of the properties due to damage or destruction of the carbon nanofiber body, the press pressure during press processing is preferably less than 3 MPa, and it is more preferable not to perform press processing.

[0086] <Polymer Layer 8> The polymer layer 8 provided between the power generation layer 6 and the second conductive layer 7 is a layer made of a polymer having a weight-average molecular weight of 20,000 or more and 200,000 or less. Here, the polymer layer 8 is preferably present in a state of at least partial contact with both the power generation layer 6 and the second conductive layer 7. The polymer constituting the polymer layer 8 is not particularly limited, and known polymers can be used. With this configuration, the polymer layer 8 can function as a buffer layer, thereby stabilizing the shape of the bonding surface while suppressing performance degradation of the photoelectric conversion element 100.

[0087] The polymer constituting the polymer layer 8 is not particularly limited as long as it can improve adhesion without inhibiting charge transport at the interface. In this regard, the polymer constituting the polymer layer 8 is preferably a hydrogenated polymer, more preferably a polymer having a hydrogenated aromatic or diene skeleton in the main chain, and more preferably one or more types selected from the group consisting of a hydrogenated aromatic vinyl compound-conjugated diene block copolymer and a hydrogenated aromatic vinyl compound-conjugated diene block copolymer modified with a silicon atom-containing polar group. Furthermore, the hydrogenated aromatic vinyl compound-conjugated diene block copolymer preferably has a structure in which both the non-aromatic carbon-carbon unsaturated bond and the aromatic carbon-carbon unsaturated bond are hydrogenated.

[0088] Examples of the polymer constituting the polymer layer 8 include ethylene-α-olefin copolymers such as ethylene-propylene copolymers; ethylene-α-olefin-polyene copolymers; copolymers of ethylene and unsaturated carboxylic acid esters such as ethylene-methyl methacrylate and ethylene-butyl acrylate copolymers; copolymers of ethylene and fatty acid vinyl such as ethylene-vinyl acetate copolymers; polymers of alkyl acrylates such as ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate; and diene-based polymers such as polybutadiene, polyisoprene, acrylonitrile-butadiene copolymers, butadiene-isoprene copolymers, butadiene-(meth)acrylic acid alkyl ester copolymers, butadiene-(meth)acrylic acid alkyl ester-acrylonitrile copolymers, and butadiene-(meth)acrylic acid alkyl ester-acrylonitrile-styrene copolymers. copolymers; butylene-isoprene copolymers; aromatic vinyl compound-conjugated diene copolymers such as styrene-butadiene random copolymers, styrene-isoprene random copolymers, styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, and styrene-isoprene-styrene block copolymers; hydrogenated aromatic vinyl compound-conjugated diene copolymers such as hydrogenated styrene-butadiene random copolymers, hydrogenated styrene-isoprene random copolymers, hydrogenated styrene-butadiene block copolymers, hydrogenated styrene-butadiene-styrene block copolymers, hydrogenated styrene-isoprene block copolymers, and hydrogenated styrene-isoprene-styrene block copolymers; low-crystalline polybutadiene; styrene-grafted ethylene-propylene elastomers; thermoplastic polyester elastomers; and ethylene-based ionomers. One type of thermoplastic elastomer may be used alone, or two or more types may be used in any combination in any ratio.

[0089] As the polymer, a hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferred in order to obtain the desired effects of the present invention. The hydrogenated aromatic vinyl compound-conjugated diene block copolymer refers to a hydrogenated product of an aromatic vinyl compound-conjugated diene block copolymer. That is, the hydrogenated aromatic vinyl compound-conjugated diene block copolymer refers to a polymer having a structure obtained by hydrogenating a portion or all of the non-aromatic carbon-carbon unsaturated bonds, the aromatic carbon-carbon unsaturated bonds, or both of these of the aromatic vinyl compound-conjugated diene block copolymer. However, the hydrogenated product is not limited by its production method.

[0090] As the aromatic vinyl compound, styrene and its derivatives; and vinylnaphthalene and its derivatives are preferred. In view of industrial availability, it is particularly preferred to use styrene. On the other hand, as the conjugated diene, a chain conjugated diene (straight-chain conjugated diene, branched-chain conjugated diene) is preferred. Preferred examples of conjugated dienes include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Of these, 1,3-butadiene and isoprene are particularly preferred in view of industrial availability.

[0091] The mass fraction of all aromatic vinyl monomer units in the entire aromatic vinyl compound-conjugated diene block copolymer is w Ａ The mass fraction of all conjugated diene monomer units in the entire aromatic vinyl compound-conjugated diene block copolymer is expressed as w Ｂ In this case, w Ａ And lol Ｂ Ratio to (w Ａ / w Ｂ ) is preferably in a specific range. Ａ / w Ｂ ) is preferably 20 / 80 or more, more preferably 30 / 70 or more, and is preferably 60 / 40 or less, more preferably 55 / 45 or less. Ａ / w ＢWhen the ratio (w Ａ / w Ｂ ) within the above range, the temperature range in which the polymer layer 8 has rubber elasticity can be widened, and therefore the temperature range in which the photoelectric conversion element 100 has flexibility can be widened.

[0092] The aromatic vinyl compound-conjugated diene block copolymer is preferably a polymer selected from styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, and mixtures thereof. Specific examples thereof include those described in technical documents such as JP-A-2-133406, JP-A-2-305814, JP-A-3-72512, JP-A-3-74409, and WO 2015 / 099079.

[0093] The hydrogenation rate of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 90% or more, more preferably 97% or more, and particularly preferably 99% or more. The higher the hydrogenation rate, the better the heat resistance and light resistance of the polymer layer 8. The hydrogenation rate of the hydrogenated product can be determined by measurement using 1H-NMR.

[0094] The hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 95% or more, more preferably 99% or more. When the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds is high, the light resistance and oxidation resistance of the polymer layer 8 can be further improved.

[0095] The hydrogenation rate of the aromatic carbon-carbon unsaturated bonds of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferably 90% or more, more preferably 93% or more, and particularly preferably 95% or more. When the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds is high, the glass transition temperature of the hydrogenated product increases, thereby effectively improving the heat resistance of the polymer layer 8. Furthermore, the photoelastic coefficient of the polymer layer 8 can be lowered, thereby reducing the occurrence of retardation.

[0096] The hydrogenated aromatic vinyl compound-conjugated diene block copolymer particularly preferably has a structure in which both the non-aromatic carbon-carbon unsaturated bond and the aromatic carbon-carbon unsaturated bond are hydrogenated.

[0097] Particularly preferred block forms of the hydrogenated aromatic vinyl compound-conjugated diene block copolymer are a triblock copolymer in which a block [A] of a hydrogenated aromatic vinyl polymer is bonded to both ends of a block [B] of a hydrogenated conjugated diene polymer, or a pentablock copolymer in which a polymer block [B] is bonded to both ends of a polymer block [A] and a polymer block [A] is bonded to the other end of each of the polymer blocks [B]. In particular, an [A]-[B]-[A] triblock copolymer is particularly preferred because it is easy to produce and can achieve the desired range of physical properties as a thermoplastic elastomer.

[0098] The hydrogenated aromatic vinyl compound-conjugated diene block copolymer can be produced, for example, by the methods described in WO 2015 / 099079 and JP 2016-204217 A.

[0099] The polymer may also be a polymer having a silicon atom-containing polar group. Examples of such polymers include modified products of the polymers exemplified as polymers that can be used as thermoplastic elastomers with a silicon atom-containing polar group. When a polymer having a silicon atom-containing polar group is used as the thermoplastic elastomer, the adhesion between the organic sealing layer and other components can be improved.

[0100] Hereinafter, the polymer used in the reaction to obtain the modified product may be referred to as the "pre-reaction polymer" as appropriate. The modified product may have a structure obtained by, for example, graft polymerization of the pre-reaction polymer with a compound having a silicon atom-containing polar group as a monomer. However, the modified product is not limited by its production method.

[0101] The silicon atom-containing polar group is preferably an alkoxysilyl group. Examples of compounds having an alkoxysilyl group as the silicon atom-containing polar group include ethylenically unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 2-norbornene-5-yltrimethoxysilane.

[0102] By reacting a pre-reaction polymer with a compound having a silicon atom-containing polar group, a silicon atom-containing polar group can be introduced into the pre-reaction polymer, thereby obtaining a modified product having a silicon atom-containing polar group. When an alkoxysilyl group is introduced as the silicon atom-containing polar group, the amount of alkoxysilyl group introduced is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.3 parts by weight or more, relative to 100 parts by weight of the pre-reaction polymer, and is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 3 parts by weight or less. When the amount of alkoxysilyl group introduced falls within the above range, the degree of crosslinking between alkoxysilyl groups decomposed by water can be prevented from becoming excessively high, thereby maintaining high adhesiveness. Examples of substances having alkoxysilyl groups used to introduce alkoxysilyl groups and modification methods include those described in WO 2015 / 099079.

[0103] The amount of polar group introduced can be measured by 1H-NMR spectroscopy. When the amount of polar group introduced is small, the number of integration times can be increased.

[0104] Among the above-mentioned polymers, from the viewpoint of significantly achieving the desired effects of the present invention, one or more types selected from the group consisting of hydrogenated aromatic vinyl compound-conjugated diene block copolymers and hydrogenated aromatic vinyl compound-conjugated diene block copolymers modified with silicon atom-containing polar groups are preferred, and among these, hydrogenated aromatic vinyl compound-conjugated diene block copolymers modified with silicon atom-containing polar groups are particularly preferred.

[0105] Among the modified products of hydrogenated aromatic vinyl compound-conjugated diene block copolymers with silicon atom-containing polar groups, modified products in which an alkoxysilyl group has been introduced as the silicon atom-containing polar group are preferred. Generally, the introduction of an alkoxysilyl group as a polar group into a pre-reaction polymer such as a hydrogenated aromatic vinyl compound-conjugated diene block copolymer is sometimes referred to as silane modification. In the silane modification, the alkoxysilyl group may be bonded directly to the pre-reaction polymer, or may be bonded via a divalent organic group such as an alkylene group. Hereinafter, the polymer obtained by silane modification of the pre-reaction polymer is also referred to as a "silane-modified product."

[0106] Therefore, as the silicon atom-containing polar group-modified hydrogenated aromatic vinyl compound-conjugated diene block copolymer, a silane-modified hydrogenated aromatic vinyl compound-conjugated diene block copolymer is preferred, and among them, one or more silane-modified products selected from the group consisting of a silane-modified hydrogenated styrene-butadiene block copolymer, a silane-modified hydrogenated styrene-butadiene-styrene block copolymer, a silane-modified hydrogenated styrene-isoprene block copolymer, and a silane-modified hydrogenated styrene-isoprene-styrene block copolymer are particularly preferred.

[0107] The weight-average molecular weight (Mw) of the polymer is not particularly limited, but is preferably 20,000 or more, more preferably 30,000 or more, even more preferably 35,000 or more, and preferably 200,000 or less, more preferably 100,000 or less, and even more preferably 70,000 or less. The weight-average molecular weight of the thermoplastic elastomer can be measured in polystyrene equivalent terms by gel permeation chromatography using tetrahydrofuran as a solvent. The molecular weight distribution (Mw / Mn) of the thermoplastic elastomer is preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, and preferably 1 or more. When the weight-average molecular weight Mw and molecular weight distribution Mw / Mn of the thermoplastic elastomer are within the above ranges, the mechanical strength and heat resistance of the polymer layer 8 can be improved.

[0108] The glass transition temperature of the thermoplastic elastomer is not particularly limited, but is preferably 40° C. or higher, more preferably 70° C. or higher, and preferably 200° C. or lower, more preferably 180° C. or lower, and even more preferably 160° C. or lower. When a thermoplastic elastomer containing a block copolymer is used, the weight ratio of each polymer block can be changed to adjust the glass transition temperature, thereby achieving a balance between the adhesiveness and flexibility of the polymer layer 8. The glass transition temperature of the resin can be measured using a differential scanning calorimeter (DSC) by increasing the temperature at a rate of 10° C. / min.

[0109] The second conductive layer 7 may contain the material constituting the polymer layer 8 described above inside the second conductive layer 7. The power generation layer 6 may contain the material constituting the polymer layer 8 described above inside the power generation layer 6.

[0110] According to the above-described photoelectric conversion element 100, the functions of the hole transport layer and the collecting electrode can be performed by the single second conductive layer 7. Furthermore, since the photoelectric conversion element 100 includes the polymer layer 8 as a buffer layer between the power generation layer 6 and the second conductive layer 7, it is possible to achieve excellent structural stability and photoelectric conversion efficiency.

[0111] The photoelectric conversion element of the present invention may further comprise other layers, etc., as long as the photoelectric conversion element is an integrated laminate in which the above-mentioned order of the constituent members is maintained, the second conductive layer is made of a porous layer containing at least carbon nanofibers, and a polymer layer made of a polymer having a weight-average molecular weight of 20,000 to 200,000 is provided between the power generation layer and the second conductive layer. Furthermore, the photoelectric conversion element of the present invention may also comprise an extraction electrode made of one or more other conductive members in order to extract electricity collected by the second conductive layer to the outside of the photoelectric conversion element.

[0112] (Method for Manufacturing Photoelectric Conversion Element) The method for manufacturing the photoelectric conversion element 100 of the above-described embodiment is not particularly limited. For example, the photoelectric conversion element 100 can be manufactured by a method including a step (hereinafter also referred to as step O) of laminating the polymer layer 8 on the power generation layer 6, and then laminating the porous free-standing sheet on the polymer layer 8 while at least one of the bonding surfaces between the porous free-standing sheet that will become the second conductive layer 7 and the polymer layer 8 retains a solvent (hereinafter also referred to as solvent X). The photoelectric conversion element 100 may also be manufactured by a method including a step (hereinafter also referred to as step P) of laminating the porous free-standing sheet on the power generation layer 6 while at least one of the bonding surfaces between the porous free-standing sheet that will become the second conductive layer 7 and the power generation layer 6 retains a solution (hereinafter also referred to as solution Y) in which a polymer for forming the polymer layer 8 is dissolved. In either method, a step of drying the solvent X or solution Y may be further included. Note that the "bonding surface" mentioned above refers to the surface on the side where the power generation layer 6 and the porous free-standing sheet face each other. A method for manufacturing the photoelectric conversion element 100 will be specifically described below.

[0113] <Preparation of Light-Transmitting Substrate 1> In the method for manufacturing the photoelectric conversion element 100, first, the light-transmitting substrate 1 is prepared. As the type of light-transmitting substrate 1, those listed in the "Photoelectric Conversion Element" section can be used.

[0114] <Formation of Transparent Conductive Film 2> Next, the transparent conductive film 2 is formed on the light-transmitting substrate 1. The method for forming the transparent conductive film 2 is not particularly limited, and known methods such as sputtering and vapor deposition can be used. Note that the formation of the transparent conductive film 2 may be omitted by using a commercially available light-transmitting substrate on the surface of which a transparent conductive film is formed.

[0115] <Formation of First Conductive Layer 5> Furthermore, the first conductive layer 5 is formed on the transparent conductive film 2. The first conductive layer 5 is obtained by forming the underlayer 3 on the transparent conductive film 2, and then forming the porous semiconductor layer 4.

[0116] [Formation of Underlayer 3] The method for forming the underlayer 3 is not particularly limited, and for example, the underlayer 3 can be formed by spraying a solution containing a material for forming an n-type semiconductor onto the transparent conductive film 2 and heating it as necessary.

[0117] Here, examples of methods for spraying the fine particles include spray pyrolysis, aerosol deposition, electrostatic spray, and cold spray.

[0118] [Formation of Porous Semiconductor Layer 4] The method for forming the porous semiconductor layer 4 is not particularly limited, and the porous semiconductor layer 4 can be formed, for example, by applying a solution containing a precursor of an n-type semiconductor onto the underlayer 3 by a spin coating method or the like, and then drying the applied solution.

[0119] Here, examples of precursors of n-type semiconductors include titanium alkoxides such as titanium tetrachloride (TiCl), peroxotitanic acid (PTA), titanium ethoxide, and titanium isopropoxide (TTIP); and metal alkoxides such as zinc alkoxide, alkoxysilane, zirconium alkoxide, and titanium diisopropoxide bis(acetylacetonate).

[0120] The solvent used for the solution containing the precursor of the n-type semiconductor is not particularly limited, and for example, an alcohol solution such as ethanol can be used.

[0121] Furthermore, the temperature and time for drying the solution applied onto the underlayer 3 are not particularly limited, and may be adjusted appropriately depending on the type of n-type precursor and the type of solvent used.

[0122] <Formation of Power-Generating Layer 6> Next, the power-generating layer 6 is formed on the first conductive layer 5. Methods for forming the power-generating layer 6 include, but are not limited to, vacuum deposition and coating. For example, the power-generating layer 6 can be formed by applying a precursor-containing solution containing a precursor of a perovskite compound to the first conductive layer 5 and then baking it. Examples of precursors of the perovskite compound include lead iodide (PbI) and methylammonium iodide (CHNHI). The solvent contained in the precursor-containing solution is also not particularly limited, and examples include N,N-dimethylformamide and dimethyl sulfoxide. After applying these solutions, it is also possible to promote the precipitation of the perovskite compound using a poor solvent. In this specification, a poor solvent refers to a solvent that does not substantially change the perovskite compound during the fabrication process. If no visible changes in the appearance of the perovskite compound, such as cloudiness of the film, are observed during the fabrication process, it can be said that the perovskite compound does not substantially change.

[0123] The concentration of the precursor of the perovskite compound in the precursor-containing solution may be appropriately selected depending on the solubility of the materials that make up the perovskite compound, and may be, for example, about 0.5M to 1.5M.

[0124] The method for applying the precursor-containing solution onto the first conductive layer 5 is not particularly limited, and known application methods such as spin coating, spraying, and bar coating can be used.

[0125] <Production Examples of Polymers> As examples of polymers used in the present invention, those synthesized according to the production examples shown below can be used.

[0126] (P1-1. Production of Hydrogenated Block Copolymer) Using styrene as the aromatic vinyl compound and isoprene as the linear conjugated diene compound, a hydrogenated block copolymer (hydrogenated block copolymer) having a triblock structure in which polymer block [A] is bonded to both ends of polymer block [B] was produced by the following procedure.

[0127] A reactor equipped with a stirrer and the inside of which had been thoroughly purged with nitrogen was charged with 256 parts of dehydrated cyclohexane, 25.0 parts of dehydrated styrene, and 0.615 parts of n-dibutyl ether, and 1.35 parts of n-butyllithium (15% cyclohexane solution) was added with stirring at 60°C to initiate polymerization, and the reaction was continued for 60 minutes at 60°C with further stirring. The polymerization conversion at this point was 99.5% (the polymerization conversion was measured by gas chromatography; the same applies hereinafter).

[0128] Next, 50.0 parts of dehydrated isoprene was added, and stirring was continued at the same temperature for 30 minutes. At this point, the polymerization conversion rate was 99%. Then, 25.0 parts of dehydrated styrene was further added, and stirring was continued at the same temperature for 60 minutes. At this point, the polymerization conversion rate was almost 100%. Next, 0.5 parts of isopropyl alcohol was added to the reaction solution to terminate the reaction, and a solution (i) containing a block copolymer was obtained. The weight average molecular weight (Mw) of the block copolymer in the obtained solution (i) was 44,900, and the molecular weight distribution (Mw / Mn) was 1.03 (measured in polystyrene equivalent values ​​by gel permeation chromatography using tetrahydrofuran as a solvent; the same applies below).

[0129] Next, solution (i) was transferred to a pressure-resistant reactor equipped with a stirrer, and 4.0 parts of a silica-alumina-supported nickel catalyst (E22U, nickel loading 60%; manufactured by JGC Chemical Industries, Ltd.) as a hydrogenation catalyst and 350 parts of dehydrated cyclohexane were added and mixed to solution (i). The atmosphere inside the reactor was purged with hydrogen gas, and hydrogen was further supplied to the solution while stirring. The hydrogenation reaction was carried out at a temperature of 170°C and a pressure of 4.5 MPa for 6 hours to hydrogenate the block copolymer, thereby obtaining solution (iii) containing a hydrogenated block copolymer (ii). The weight-average molecular weight (Mw) of the hydrogenated product (ii) in solution (iii) was 45,100, and the molecular weight distribution (Mw / Mn) was 1.04.

[0130] After completion of the hydrogenation reaction, the solution (iii) was filtered to remove the hydrogenation catalyst. Thereafter, 1.0 part of a xylene solution containing 0.1 part of a phosphorus-based antioxidant, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetrakis-t-butyldibenzo[d,f][1.3.2]dioxaphosphepin (Sumitomo Chemical Co., Ltd., "Sumilizer (registered trademark) GP"; hereinafter referred to as "antioxidant A"), was added and dissolved into the filtered solution (iii), thereby obtaining a solution (iv).

[0131] Next, solution (iv) was filtered through a ZetaPlus (registered trademark) filter 30H (manufactured by Cuno, pore size 0.5 μm to 1 μm) and then another metal fiber filter (pore size 0.4 μm, manufactured by Nichidai Corporation) to remove minute solids. The solvent cyclohexane, xylene, and other volatile components were removed from the filtered solution (iv) using a cylindrical concentrating dryer (product name "CONTROL", manufactured by Hitachi, Ltd.) at a temperature of 260°C and a pressure of 0.001 MPa or less. The solids were then extruded in a molten state into strands through a die directly connected to the concentrating dryer, cooled, and cut with a pelletizer to obtain 85 parts of pellets (v) containing the hydrogenated block copolymer and antioxidant A. The weight-average molecular weight (Mw) of the hydrogenated block copolymer (hydrogenated block copolymer) in the obtained pellets (v) was 45,000, and the molecular weight distribution (Mw / Mn) was 1.08. Also, 1 The hydrogenation rate measured by H-NMR was 99.9%.

[0132] (P1-2. Production of Silane-Modified Hydrogenated Block Copolymer) 2.0 parts of vinyltrimethoxysilane and 0.2 parts of di-t-butyl peroxide were added to 100 parts of the pellets (v) obtained in the above step (P1-1) to obtain a mixture. This mixture was kneaded using a twin-screw extruder at a barrel temperature of 210°C and a residence time of 80 to 90 seconds. The kneaded mixture was extruded and cut with a pelletizer to obtain pellets (vi) of the silane-modified hydrogenated block copolymer. A film-like test piece was prepared from this pellet (vi), and the glass transition temperature Tg was evaluated using the tan δ peak of a dynamic viscoelasticity measuring device, which was 124°C. The peak tan δ value of this pellet (vi) at 40°C or higher and 200°C or lower was 1.3. The Young's modulus of this pellet (vi) at 23°C was 0.5 GPa, and the tensile elongation was 550%. The refractive index (n1) of the pellet (vi) measured with an Abbe refractometer was 1.50.

[0133] <Formation of Second Conductive Layer 7 and Polymer Layer 8> <<Step O>> When the second conductive layer 7 and polymer layer 8 are formed by step O, the power generation layer 6 is formed, and then the polymer layer 8 is formed on the power generation layer 6. Then, with the solvent X held on at least one bonding surface between the porous free-standing sheet that will become the second conductive layer 7 and the polymer layer 8, the porous free-standing sheet is laminated on the polymer layer 8. This allows the porous free-standing sheet to be efficiently attached to the power generation layer 6.

[0134] [Formation of Polymer Layer 8] The method for forming the polymer layer 8 is not particularly limited. For example, the polymer layer 8 can be formed by applying a solution Y in which a polymer for forming the polymer layer 8 is dissolved to the power generation layer 6, and drying the solution as necessary.

[0135] The solvent for dissolving the polymer is not particularly limited, but examples thereof include poor solvents such as chlorobenzene, toluene, and anisole. As the polymer, those listed in the "Polymer Layer" section can be used. The concentration of the polymer in solution Y can be appropriately selected depending on the coating amount and coating method, since the amount of liquid carried varies depending on the coating amount and coating method.

[0136] The method for applying the solution Y onto the power generation layer 6 is not particularly limited, and any known application method such as spin coating, spraying, or bar coating can be used.

[0137] [Formation of Second Conductive Layer 7] The solvent X is not particularly limited, and examples thereof include poor solvents such as chlorobenzene, toluene, anisole, etc. If these poor solvents are used, for example, when the power generation layer 6 is a perovskite layer made of a perovskite compound, the performance of the power generation layer 6 can be maintained even if the solvent X penetrates into the power generation layer 6 through the polymer layer 8.

[0138] The method for retaining solvent X on at least one of the bonding surfaces between the porous free-standing sheet and the polymer layer 8 is not particularly limited. For example, solvent X may be applied to the porous free-standing sheet, solvent X may be applied to the polymer layer 8, or solvent X may be applied to both the porous free-standing sheet and the polymer layer 8.

[0139] In particular, if a porous self-supporting sheet impregnated with solvent X is used, solvent X can be well retained on at least one of the bonding surfaces between the porous self-supporting sheet and the polymer layer 8 .

[0140] Here, a porous free-standing sheet impregnated with solvent X can be obtained, for example, by immersing a porous free-standing sheet in solvent X and then removing it. The immersion time is not particularly limited and may be set appropriately depending on the type of solvent used, etc. Alternatively, the method can be appropriately selected depending on the actual manufacturing process, such as spraying or dripping solvent X onto a porous free-standing sheet placed in an application jig.

[0141] <<Step P>> When the second conductive layer 7 and the polymer layer 8 are formed in step P, the porous free-standing sheet is laminated on the power generation layer 6 in a state where at least one bonding surface between the porous free-standing sheet that will become the second conductive layer 7 and the power generation layer 6 holds solution Y, in which a polymer for forming the polymer layer 8 is dissolved. This allows the porous free-standing sheet to be efficiently attached to the power generation layer 6.

[0142] The solvent for solution Y is not particularly limited, and examples thereof include poor solvents such as chlorobenzene, toluene, and anisole, as long as they can dissolve a predetermined amount of the polymer that forms the polymer layer 8. If these poor solvents are used, for example, when the power generation layer 6 is a perovskite layer made of a perovskite compound, the performance of the power generation layer 6 can be maintained. As the polymer in solution Y, those listed in the "Polymer Layer" section can be used. The concentration of the polymer in solution Y can be selected appropriately depending on the method, as the amount of liquid supported varies depending on the application amount and application method.

[0143] The method for retaining solution Y on at least one of the bonding surfaces between the porous self-supporting sheet and the power generation layer 6 is not particularly limited, and for example, solution Y may be applied to the porous self-supporting sheet, solution Y may be applied to the power generation layer 6, or solution Y may be applied to both the porous self-supporting sheet and the power generation layer 6.

[0144] The specific method for applying solution Y to the porous self-supporting sheet is not particularly limited, and examples of methods that can be used include dipping, roll coating, gravure coating, knife coating, air knife coating, roll knife coating, die coating, screen printing, spray coating, and gravure offset.

[0145] In particular, if a porous self-supporting sheet impregnated with solution Y is used, solution Y can be well retained on at least one of the bonding surfaces between the porous self-supporting sheet and the power-generating layer 6 .

[0146] Here, the porous free-standing sheet impregnated with solution Y can be obtained, for example, by immersing a porous free-standing sheet in solution Y and then removing it. In this case, the immersion time is not particularly limited and may be set appropriately depending on the type of solvent and polymer used, etc.

[0147] The specific method for applying the solution Y to the power generation layer 6 is not particularly limited, and for example, a spin coating method, a spray method, a bar coating method, or the like can be used.

[0148] <Drying> After forming the second conductive layer 7 and the polymer layer 8 in step O or step P, a drying step of drying the porous free-standing sheet may be provided. Known drying methods can be used to dry the porous free-standing sheet. Examples of drying methods include hot air drying, vacuum drying, heat roll drying, infrared irradiation, and heat pressing. The drying temperature and drying time can be appropriately selected depending on the solvent used for solvent X or solution Y, the amount of liquid applied, and the like. The drying temperature is not particularly limited, but is preferably room temperature or higher, more preferably 80°C or higher, and preferably 200°C or lower, and more preferably 120°C or lower. The drying time is not particularly limited, but is preferably 1 second or higher, more preferably 10 seconds or higher, and preferably 10 minutes or shorter, and more preferably 1 minute or shorter.

[0149] Among the above, the hot pressing method is preferably used. The hot pressing method allows for the production of a photoelectric conversion element 100 with excellent integrity. The pressure used during hot pressing is not particularly limited as long as it does not affect the substrate or the formed film, and can be, for example, 0.01 to 0.5 MPa. The heating temperature and heating time during hot pressing can be appropriately selected depending on the solvent used for solvent X or solution Y, the amount of applied liquid, and other factors. Furthermore, when hot pressing, it is preferable to press in a manner that ensures a solvent evaporation path in order to promote the removal of the solvent component contained in the porous free-standing sheet. Specifically, in order to ensure a solvent evaporation path, it is preferable to perform hot pressing via a porous member such as a thick wipe, porous rubber, porous metal, or porous ceramic.

[0150] According to the above-described manufacturing method, it is possible to easily manufacture a photoelectric conversion element 100 having excellent structural stability and photoelectric conversion efficiency. Note that the manufacturing method of the photoelectric conversion element 100 is not limited to the above-described method, and may include steps other than the above-described steps as long as the effects of the present invention are not impaired.

[0151] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0152] <Fabrication of Perovskite Solar Cell> A perovskite solar cell was fabricated as a photoelectric conversion element by the following procedure.

[0153] Example 1 (Preparation of a Light-Transmitting Substrate Having a Transparent Conductive Film Formed Thereon) A conductive glass substrate (manufactured by Sigma-Aldrich) having a fluorine-doped tin (FTO) film formed on the surface of the glass substrate as a transparent conductive film was used, and part of the FTO film was removed by etching to obtain a light-transmitting substrate having a transparent conductive film formed thereon (hereinafter referred to as a "light-transmitting substrate with a transparent conductive film").

[0154] [Formation of First Conductive Layer] A solution (manufactured by Sigma-Aldrich) prepared by dissolving titanium diisopropoxide bis(acetylacetonate) in isopropanol was sprayed onto the surface of the FTO film of the translucent substrate with a transparent conductive film by spray pyrolysis. This resulted in the formation of an underlayer (30 nm thick) made of titanium dioxide on the FTO film. Next, a solution was prepared by diluting titanium oxide paste (manufactured by Sigma-Aldrich) with ethanol, and the resulting solution was applied to the surface of the underlayer by spin coating, followed by heat treatment at a temperature of 450°C for 30 minutes, thereby forming a titanium dioxide (TiO ２ A porous semiconductor layer (thickness: 120 nm) made of SiO 2 was formed to obtain a first conductive layer.

[0155] [Formation of Power Generation Layer] A solution (1) containing a precursor of a perovskite compound was prepared by adding lead iodide (PbI) with a concentration of 1.0 M. ２ ) and 1.0 M methylammonium iodide (CH ３ NH ３ An N,N-dimethylformamide (DMF) solution containing I) was prepared. The resulting solution (1) was applied to the surface of the first conductive layer by spin coating while chlorobenzene was added dropwise, and then baked at a temperature of 100°C for 10 minutes to form a perovskite layer (thickness 450 nm) as a power generation layer.

[0156] [Formation of Polymer Layer] A solution prepared by dissolving 10 mg of the polymer synthesized according to the above-described Production Example in 1 ml of chlorobenzene was spin-coated onto the formed perovskite layer, and the resulting solution was dried on a hot plate at 80° C. As a result, a pre-press laminate was obtained which was provided in the order of a translucent substrate with a transparent conductive film, a first conductive layer, a power generation layer (perovskite layer), and a polymer layer.

[0157] [Preparation of Porous Freestanding Sheet] A porous freestanding sheet containing single-walled CNTs was prepared according to the following procedure.

[0158] To 500 mL of a 2% by mass aqueous solution of sodium deoxycholate (DOC) as a solvent containing a dispersant, 1.0 g of single-walled CNT (manufactured by Zeon Corporation, product name "ZEONANO SG101", average diameter: 3.5 nm, G / D ratio: 2.1, t-plot is upwardly convex when unopened) was added as a fibrous carbon nanostructure containing single-walled CNT, to obtain a crude dispersion containing DOC as a dispersant. This crude dispersion was filled into a high-pressure homogenizer (manufactured by Biryu Co., Ltd., product name "BERYU SYSTEM PRO") equipped with a multistage pressure control device (multistage pressure reducer) that applies back pressure during dispersion, and the crude dispersion was subjected to a dispersion treatment at a pressure of 100 MPa. Specifically, shear force was applied to the crude dispersion while applying back pressure to disperse the fibrous carbon nanostructures containing single-walled CNT, thereby obtaining a fibrous carbon nanostructure dispersion containing single-walled CNT. The dispersion treatment was carried out for 10 minutes while the dispersion liquid flowing out of the high-pressure homogenizer was returned to the high-pressure homogenizer.

[0159] 50 g of the prepared fibrous carbon nanostructure dispersion containing single-walled CNTs was added to a 200 mL beaker, and 50 g of distilled water was added to dilute it two-fold. This was then filtered under a pressure of 0.09 MPa using a vacuum filtration device equipped with a membrane filter. After filtration, the carbon film formed on the membrane filter was washed by passing isopropyl alcohol and water through the vacuum filtration device, and then air was passed through for 15 minutes. Next, the prepared carbon film / membrane filter was immersed in ethanol, and the carbon film was peeled off from the membrane filter to obtain carbon film (A).

[0160] The obtained carbon membrane (A) had the same size as the membrane filter, excellent film-forming properties, and maintained its film state even after being peeled off from the filter, exhibiting excellent self-supporting properties. The film density of the obtained carbon membrane (A) was measured, and the density was found to be 0.85 g / cm. ３ From these results, it was found that the carbon membrane (A) was a porous self-supporting sheet (A).

[0161] [Formation of second conductive layer] The porous free-standing sheet (A) was immersed in chlorobenzene for 10 seconds, and then pulled out of the chlorobenzene to obtain a chlorobenzene-impregnated porous free-standing sheet (1). The porous free-standing sheet (1) was laminated on a pre-press laminate heated on a hot plate at a temperature of 80°C, and the resulting laminate was dried while being heated and pressed from the porous free-standing sheet (1) side via a wipe at a pressure of 0.05 MPa, to obtain a perovskite solar cell.

[0162] Example 2 A perovskite solar cell was produced in accordance with Example 1, except that a polymer layer was not formed in advance on the power generation layer, and the porous free-standing sheet (A) was immersed for 20 seconds in a solution prepared by dissolving 10 mg of a polymer synthesized based on the above-described production example in 1 ml of chlorobenzene, and then the porous free-standing sheet (A) was pulled up from the solution, and the porous free-standing sheet (1) was laminated onto a pre-press laminate heated on a hot plate at a temperature of 80°C, and the resulting laminate was dried while being heat-pressed from the side of the porous free-standing sheet (1) via a wipe at a pressure of 0.05 MPa.

[0163] Comparative Example 1 A perovskite solar cell was fabricated in accordance with Example 1, except that the porous free-standing sheet (A) was placed directly on the perovskite layer without forming a polymer layer.

[0164] Example 3 A perovskite solar cell was fabricated in the same manner as in Example 1, except that a polymer layer was formed on the formed perovskite layer after a Li salt treatment was performed on the surface of the formed perovskite layer.

[0165] Comparative Example 2 A perovskite solar cell was fabricated in accordance with Example 2, except that the porous free-standing sheet (A) was placed directly on the perovskite layer without forming a polymer layer.

[0166] Example 4 A perovskite solar cell was fabricated in accordance with Example 1, except that a porous free-standing sheet was produced without using a dispersant.

[0167] Comparative Example 3 A perovskite solar cell was fabricated in accordance with Example 3, except that the porous free-standing sheet (A) was placed directly on the perovskite layer without forming a polymer layer.

[0168] Example 5 A perovskite solar cell was fabricated in the same manner as in Example 3, except that a polymer layer was formed on the formed perovskite layer after a Li salt treatment was performed on the surface of the formed perovskite layer.

[0169] Comparative Example 4 A perovskite solar cell was fabricated in accordance with Example 4, except that the porous free-standing sheet (A) was placed directly on the perovskite layer without forming a polymer layer.

[0170] <Evaluation of Structural Stability> The obtained perovskite solar cells were examined for the presence or absence of peeling of the second conductive layer immediately after production and after a predetermined period of time. The results are shown in Tables 1 and 2.

[0171]

[0172]

[0173] The results shown in Tables 1 and 2 demonstrate that the methods of Examples 1 to 4 make it possible to manufacture perovskite solar cells with excellent structural stability.

[0174] According to the present invention, it is possible to provide a photoelectric conversion element having excellent structural stability.

[0175] REFERENCE SIGNS LIST 1 Light-transmitting substrate 2 Transparent conductive film 3 Underlayer 4 Porous semiconductor layer 5 First conductive layer 6 Power generation layer 7 Second conductive layer 8 Polymer layer 100 Photoelectric conversion element

Claims

1. A photoelectric conversion element including a laminated body including a light-transmitting substrate, a transparent conductive film, a first conductive layer, a power generation layer, and a second conductive layer, which are integrated together in this order, a photoelectric conversion element, wherein the second conductive layer is a porous layer containing at least a carbon nanofiber material, and a polymer layer made of a polymer having a weight-average molecular weight of 20,000 or more and 200,000 or less is provided between the power generation layer and the second conductive layer.

2. The photoelectric conversion element according to claim 1 , wherein the polymer is a hydrogenated polymer.

3. 2. The photoelectric conversion element according to claim 1, wherein the polymer has a hydrogenated aromatic or diene skeleton in the main chain.

4. 2. The photoelectric conversion element according to claim 1, wherein the polymer is at least one selected from the group consisting of a hydrogenated aromatic vinyl compound-conjugated diene block copolymer and a hydrogenated aromatic vinyl compound-conjugated diene block copolymer modified with a silicon atom-containing polar group.

5. 5. The photoelectric conversion element according to claim 4, wherein the hydrogenated aromatic vinyl compound-conjugated diene block copolymer has a structure in which both non-aromatic carbon-carbon unsaturated bonds and aromatic carbon-carbon unsaturated bonds are hydrogenated.

6. The photoelectric conversion element according to claim 1 , wherein the second conductive layer is made of a porous self-supporting sheet.

7. The photoelectric conversion element according to claim 6 , wherein the porous free-standing sheet has a thickness of 20 μm or more.

8. The photoelectric conversion element according to claim 1 , wherein the power generation layer contains a perovskite compound.

9. 2. The photoelectric conversion element according to claim 1, wherein the carbon nanofiber body has an average diameter (Av) and a standard deviation (σ) of the diameters that satisfy the relationship: 0.20<(3σ / Av)<0.

60.

10. 2. The photoelectric conversion element according to claim 1, wherein the carbon nanofiber material exhibits an upwardly convex t-plot obtained from an adsorption isotherm.

11. A method for producing the photoelectric conversion element according to any one of claims 1 to 10, and then laminating the polymer layer on the power-generating layer, while retaining a solvent on at least one bonding surface between the porous free-standing sheet that will become the second conductive layer and the polymer layer.

12. A method for producing the photoelectric conversion element according to any one of claims 1 to 10, a step of laminating the porous free-standing sheet to be the second conductive layer on the power generating layer in a state where at least one bonding surface between the porous free-standing sheet and the power generating layer retains a solution in which a polymer for forming the polymer layer is dissolved.