Organic solar cell module, organic solar cell module electrode, and method of producing organic solar cell module

Abstract

An organic solar cell module 10 has a module structure in which a plurality of unit cells A each comprising a first electrode 1 and a second electrode 2 that are translucent and face opposite in the Z-direction, and a power generation laminate 7 comprising a laminated structure including an electron transport layer 3 and a hole transport layer 4 lined up in the Z-direction as well as an organic power generation layer 5 located therebetween, one of the electron transport layer 3 and the hole transport layer 4 being arranged opposite the first electrode 1 and the other being arranged opposite the second electrode 2, are arranged spaced apart between a first substrate 11 and a second substrate 12 both of which are translucent and which face opposite in the Z-direction, so that the first substrate 11 and the first electrode 1 face opposite and are lined up in the in-plane direction of the XY-plane. Between two adjacent unit cells A of the plurality of unit cells A, there is a connection wiring 6 connecting the first electrodes 1 of unit cells A1, A2 and the second electrodes 2 of unit cells A2, A3. The connection wiring 6 and the second electrodes 2 are integrally formed of carbon nanotubes.

Description

Organic solar cell module, electrode for organic solar cell module, and method for manufacturing organic solar cell module

[0001] The present invention relates to an organic solar cell module in which a plurality of cells are connected, an electrode for the organic solar cell module, and a method for manufacturing the organic solar cell module.

[0002] Organic photovoltaics (OPV) are organic solar cells that use a thin film of an organic semiconductor as the power generation layer. They have attracted attention as next-generation solar cells due to their advantages, such as being lightweight and flexible, being able to be manufactured by coating because the organic semiconductor is soluble in a solvent, and having high transparency because the power generation layer is on the order of several hundred nanometers thick. While organic solar cell modules based on organic thin-film solar cells have the above-mentioned unique advantages not found in conventional inorganic solar cells, they still face challenges in terms of cost and durability due to the use of metals as electrodes. To address these challenges, the production of OPVs (CNT-OPVs) using electrodes made of carbon nanotubes (CNTs) instead of metals has been reported (see, for example, Patent Document 1).

[0003] International Publication No. WO2016 / 035832

[0004] Patent Document 1 describes the fabrication of cell-sized CNT-OPVs on a laboratory scale, but does not describe modules scaled up from the cell size. To advance to the next stage, it is necessary to create a module structure in which single cells with larger light-receiving areas are arranged in series on the same substrate. In other words, in the practical application of organic semiconductor batteries, it is important to connect multiple cells to form a module. The present invention aims to provide an organic solar cell module, an electrode for an organic solar cell module, and a method for manufacturing an organic solar cell module.

[0005] As a means for solving the above-mentioned problems, the present invention has the following configuration. [1] An organic solar cell module having a module structure in which a plurality of unit cells each having a first electrode and a second electrode, both of which are light-transmitting and opposed to each other in a first direction, and a power-generating stack including an electron transport layer, a hole transport layer, and an organic power-generating layer positioned between the electron transport layer and the hole transport layer, which are aligned in the first direction, and one of the electron transport layer and the hole transport layer is disposed opposite the first electrode and the other of the electron transport layer and the hole transport layer is disposed opposite the second electrode, the module structure being such that the first substrate and the first electrode are opposed to each other and the first substrate and the first electrode are disposed apart from each other in an in-plane direction of an intersecting plane of the first direction, and a connection wiring is provided between a first cell and a second cell, which are two adjacent unit cells among the plurality of unit cells, connecting the first electrode of the first cell and the second electrode of the second cell, and the connection wiring and the second electrode are integrally formed of a first material containing carbon nanotubes.

[0006] [2] The organic solar cell module according to [1], wherein the second electrode has a transmittance of 14% or more at λ=550 nm. [3] The organic solar cell module according to [1], wherein the second substrate is a protective film.

[0007] [4] The organic solar cell module according to [1], wherein at least four of the unit cells are connected in series via the connecting wiring, and the open circuit voltage is 2.70 V or more. [5] The organic solar cell module according to [1], wherein, when the module structure has four of the unit cells connected in series using the connecting wiring, the series resistance per unit cell, obtained by dividing the series resistance of the module structure by 4, which is the number of the unit cells, is 39 Ω / cell or less.

[0008] [6] The organic solar cell module according to [1], wherein the first electrode is made of an oxide-based material. [7] The organic solar cell module according to [1], wherein the first electrode is made of a material containing the carbon nanotubes. [8] The organic solar cell module according to [1], wherein the first electrode is made of a metal-based material.

[0009] [9] The first material contains the carbon nanotubes and has an S in the absorption spectrum in the near-infrared region. 11 The absorption peak that appears at wavelengths of 2200 to 2500 nm due to the transition is S 22 The organic solar cell module according to [1], wherein the peak wavelength is smaller than the peak appearing in the wavelength range of 1100 to 1500 nm due to the transition.

[0010]

[10] The organic solar cell module according to [1], wherein the surface resistivity of the first material is 5 Ω / □ or more.

[11] The organic solar cell module according to [1], wherein the length of the second electrode in the first direction is 0.50 μm or less, and the average length of the carbon nanotubes contained in the first material is 1 μm or more.

[12] The organic solar cell module according to

[11] , wherein the length of the power-generating laminate in the first direction is 0.15 μm or more.

[0011]

[13] The organic solar cell module according to [1], which has a transmittance of 18% or more at chloroplast absorption wavelengths measured by a measurement method based on JIS K7375: 2008.

[14] The organic solar cell module according to [1], which has a total light reflectance of 10% or less measured by a measurement method based on JIS K7375: 2008.

[0012]

[15] The organic solar cell module according to [4], wherein the conversion efficiency Em of the module structure and the conversion efficiency Ec of the single cell satisfy Em / Ec≧0.60.

[0013]

[16] Carbon nanotubes are contained, and S in the infrared absorption spectrum 11 The peak that appears at wavelengths of 2200 to 2500 nm due to the transition is S 22

[17] The electrode for a solar cell module according to

[16] , which is formed integrally with a connecting wiring that electrically connects two adjacent single cells in a solar cell module, is characterized in that the peak wavelength is smaller than that appearing in the wavelength range of 1100 to 1500 nm due to transition.

[0014]

[18] The method for manufacturing an organic solar cell module according to [1], characterized in that the second electrode and the connecting wiring are formed by pressing a material containing carbon nanotubes to form a press body, and a polymeric acid is applied to the second electrode and the connecting wiring to dope holes into the carbon nanotubes.

[19] The method for manufacturing an organic solar cell module according to

[18] , wherein the polymeric acid has a sulfo group.

[20] The method for manufacturing an organic solar cell module according to

[18] , wherein the polymeric acid is PEDOT:PSS or Nafion.

[0015]

[21] The method for manufacturing an organic solar cell module according to

[18] , wherein a volatile solvent is applied to the second electrode and the connecting wiring.

[22] The method for manufacturing an organic solar cell module according to

[21] , wherein the volatile solvent is applied to the second electrode and the connecting wiring by spray coating.

[23] The method for manufacturing an organic solar cell module according to

[21] , wherein the volatile solvent is a lower alcohol having 3 or less carbon atoms.

[0016] The present invention enables modularization of single organic solar cell cells by forming a connection wiring that connects the first electrode of a first cell to the second electrode of a second cell adjacent to the first cell integrally with the second electrode, thereby electrically connecting the first cell and the second cell. Furthermore, by forming the connection wiring integrally with the second electrode, the proportion of the connection wiring can be reduced, thereby providing an organic solar cell module with excellent power generation efficiency. By applying a polymeric acid to the second electrode and connection wiring containing carbon nanotubes, the carbon nanotubes can be doped with holes. Therefore, the sheet resistance of the integrally formed second electrode and connection wiring, which are suitable for modularization, can be reduced, providing an organic solar cell module with excellent power generation efficiency.

[0017] 7A is a cross-sectional view schematically illustrating the configuration of an organic solar cell module according to an embodiment. 7B is a photograph, substituted for a drawing, showing the appearance of an organic solar cell module according to an example. 7C is a photograph, substituted for a drawing, showing a cross section of a single cell of an organic solar cell module using a CNT thin film electrode as the second electrode, observed with a TEM. 7D is an IV curve of an organic solar cell module according to an example. 7E is a schematic diagram illustrating the configuration of a spray coating device. 7F is an IV curve (current-voltage curve) of an organic solar cell module before and after spray coating. 7G is a graph showing changes in Raman spectra before and after spray coating of a solution containing a polymer acid. 7H is a graph showing an enlarged portion of FIG. 7A. 7G is an IV curve of an organic solar cell module before and after nitric acid doping. 7G is an IV curve of a general solar cell. 7G is an IV curve of a solar cell module before and after application of PEDOT:PSS. 7G is an IV curve of a solar cell module before and after application of Nafion. 7H is a schematic diagram illustrating the mechanism by which an absorption peak in the infrared region disappears due to hole doping. This is an absorption spectrum in the near-infrared region of a CNT thin film sprayed with IPA and PEDOT:PSS. This is an absorption spectrum in the near-infrared region of a CNT thin film sprayed with IPA and Nafion. This is a drawing-substitute photograph of a cross section of a single cell using a CNT thin film electrode as the second electrode, observed with an SEM. This is an IV curve of a single cell of an organic solar cell module, showing the effect of the application method of the volatile solvent.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The Z axis in the coordinate system shown for reference in the drawings corresponds to the first direction. FIG. 1 is a cross-sectional view schematically illustrating the configuration of a module (organic solar cell module) 10 according to an embodiment. In the module 10, a plurality of unit cells A1, A2, and A3 are spaced apart and aligned in an in-plane direction of an XY plane intersecting the Z direction. Hereinafter, when there is no need to distinguish between the unit cells A1, A2, and A3, they will be referred to as unit cell A.

[0019] The single cell A has a laminated structure including a first electrode 1 and a second electrode 2, both of which are transparent and opposed to each other in the Z direction (first direction), an electron transport layer 3 and a hole transport layer 4 aligned in the Z direction, and an organic power generation layer 5 positioned between the electron transport layer 3 and the hole transport layer 4. In this embodiment, "transparent" refers to having the property of transmitting visible light. The translucency of a "transparent" member can be evaluated, for example, by the transmittance of light at λ=550 nm (hereinafter simply referred to as "transmittance"). From the viewpoint of achieving a solar cell module with excellent power generation efficiency, it is preferable that the members constituting the first electrode 1 and the second electrode 2 have high translucency.

[0020] For example, if the module 10 has a transmittance of light of λ=550 nm of approximately 7% to 30%, it is useful as a material to replace smoked glass, and if it has a transmittance of 30% or more, it is useful as a material to replace translucent glass.

[0021] For example, if the transmittance of light at λ=550 nm in the portions of the module 10 other than the second electrode 2 is 50%, and the transmittance of the second electrode 2 is 14% or more, it is possible to realize a module 10 that can be used as a replacement for smoked glass. Furthermore, by using a first material containing carbon nanotubes, it is possible to form a second electrode 2 that has a transmittance of 60% or more, or even 85% or more, for light at λ=550 nm, and therefore it is also possible to realize a module 10 that can be used as a replacement for translucent glass.

[0022] Furthermore, by using the second electrode 2 having such high transmittance, light can be captured not only from the first electrode 1 side but also from the second electrode 2 side and used for power generation by the organic power generation layer 5. This makes it possible to realize a module 10 that can capture light from both the first electrode 1 and the second electrode 2 side simultaneously and be used for power generation. Furthermore, if the module 10 is used as a window provided at the boundary between indoors and outdoors, it becomes possible to capture light mainly from the first electrode 1 side and also from the second electrode 2 side for power generation during the day, and to capture indoor light from the second electrode 2 side for power generation at night. The organic solar cell module 10 has an absorption wavelength that is more suited (matches) to indoor light than sunlight, so it can capture indoor light from the second electrode 2 side and generate power efficiently.

[0023] In the module 10, one of the electron transport layer 3 and the hole transport layer 4 is disposed opposite the first electrode 1, and the other of the electron transport layer 3 and the hole transport layer 4 is disposed opposite the second electrode 2. In the power-generating laminate 7 shown in FIG. 1 , the electron transport layer 3 is disposed opposite the first electrode 1, and the hole transport layer 4 is disposed opposite the second electrode 2.

[0024] The module 10 has a module structure in which unit cells A1, A2, and A3 are spaced apart and aligned in an in-plane direction of an XY plane, which is an intersecting plane that intersects with the Z direction, between a first base material 11 and a second base material 12, both of which are light-transmitting and opposed in the Z direction. In the example shown in Fig. 1, the layers are arranged with the first base material 11 and the first electrode 1 opposed to each other.

[0025] Each unit cell A has a connection wiring 6 that connects two adjacent unit cells A among the plurality of unit cells A. For example, a unit cell (first cell) A1 and a unit cell (second cell) A2 have a connection wiring 6 between them that connects the first electrode 1 of the unit cell A1 and the second electrode 2 of the unit cell A2. With this configuration, the first electrode 1 of the unit cell A and the second electrode 2 of the unit cell A adjacent to that unit cell A are electrically connected, and the plurality of unit cells A can be modularized.

[0026] The first electrode 1 may be made of any material as long as it is translucent, but may be made of, for example, an oxide-based material such as indium tin oxide, zinc oxide, tin oxide, or titanium oxide, a material containing carbon nanotubes, or a metal-based material.

[0027] Conventionally, precious metals such as gold and silver have been used for the second electrode 2. However, precious metals are limited resources and have problems such as poor physical and chemical durability. Therefore, in the module 10 of this embodiment, the second electrode 2 is formed using a first material containing carbon nanotubes (CNTs).

[0028] CNTs are a more abundant resource than precious metals, and are characterized by their flexibility, stability in the atmosphere, and excellent physical and chemical durability. Furthermore, if the second electrode 2 is formed using a first material containing CNTs, the connection wiring 6 and the second electrode 2 can be integrally formed by a transfer method without using a vacuum process such as vacuum deposition. Therefore, CNTs are superior to conventionally used precious metals in that the cost and effort required for film formation can be kept low. CNTs can be produced by known methods such as arc discharge, laser evaporation, and CVD.

[0029] Compared to other manufacturing methods, the CVD method can produce CNTs with high purity, high yield, and low cost, making it suitable for mass synthesis. There are two main types of CVD methods. One is the fluidized bed method, in which CNTs are grown from a substrate or carrier carrying catalyst particles, and the other is the gas-phase flow method, in which CNTs are grown from catalyst particles suspended in a flowing gas phase without using a substrate or carrier.

[0030] The first material that integrally forms the connection wiring 6 and the second electrode 2 may contain CNTs, may further contain a metal oxide film, or may be doped with an acid. It may also be a CNT film, such as a single-walled carbon nanotube (SWCNT), with a polymeric acid film formed on it. A "polymeric acid" is a polymer that exhibits acid properties and contains carboxyl groups (-COOH) and sulfo groups (-SO3H) within the molecule, many of which are water-soluble. Examples of polymeric acids that can be used include poly(3,4-ethylenedioxythiophene) poly(styrenesulfonic acid) (PEDOT:PSS) and Nafion (trademark).

[0031] When the connection wiring 6 and the second electrode 2 are formed as a CNT pressed body, the pressed body may be formed by a transfer method, and then a volatile solvent may be applied and dried. The second electrode 2 of a pressed body formed of CNT by a transfer method may not have sufficient adhesion to the hole transport layer 4. However, by forming the second electrode 2 of the pressed body, applying a volatile solvent and drying it, the adhesion between the second electrode 2 and the hole transport layer 4 is improved, thereby improving the performance of the module 10. As the volatile solvent, for example, a lower alcohol having 3 or less carbon atoms, such as methanol, ethanol, or isopropyl alcohol, can be used.

[0032] For example, when a SWCNT film is used as the second electrode 2 and the connection wiring 6 of a pressing body integrally formed with CNTs, the film thickness at the time of transferring the SWCNT film to the hole transport layer 4 is typically about 100 to 150 nm. When a volatile solvent such as alcohol is applied to the second electrode 2 of this SWCNT film by dropwise application, spin coating, spray coating, or the like, the penetration of the volatile solvent into the SWCNT film and the surface tension thereof cause the SWCNT film to shrink, resulting in a film thickness of 100 nm or less (typically about 50 to 80 nm). This allows the second electrode 2 of the SWCNT film to adhere closely to the hole transport layer 4. Furthermore, when the pressing body of the SWCNT film shrinks, the connection wiring 6 formed integrally with the second electrode 2 can be brought into close contact with the first electrode 1 formed of ITO or the like in the adjacent single cell A.

[0033] By utilizing the penetration of the volatile solvent into the SWCNT film and its surface tension, the second electrode 2 and the first electrode 1 of the adjacent unit cell A can be efficiently and reliably connected by the connecting wire 6. This makes it possible to effectively and reliably connect the unit cells A in series. Note that if the volatile solvent is allowed to penetrate into the SWCNT film after pressing the SWCNT film presser with a roller or the like, it is thought that neither of the above-mentioned effects of adhering the second electrode 2 and the hole transport layer 4 nor the above-mentioned effects of adhering the connecting wire 6 formed integrally with the second electrode 2 and the first electrode 1 of the adjacent unit cell A can be obtained.

[0034] The volatile solvent may contain a polymeric acid. Applying a polymeric acid solution containing a polymeric acid and a volatile solvent to the second electrode 2 of a pressed body formed from CNTs and drying the solution allows the CNTs to be doped with holes (p-type doping, appropriately referred to as p-doping). By p-doping the CNT film constituting the pressed body formed using a transfer method with a polymeric acid, the conductivity of the second electrode 2 and the connecting wiring 6 is improved, and electrical resistance is reduced, thereby improving the performance of the module 10. Furthermore, the hole transport ability of the CNTs can also be improved by p-doping using a strong acid such as nitric acid to inject protons into the pressed body formed from CNTs. However, because the use of a strong acid may cause deterioration of the power generation layer, it is preferable to use a polymeric acid solution for p-doping the CNTs.

[0035] The polymer acid solution may contain a polymer acid, and may be, for example, a solution in which the polymer acid is dissolved in various solvents, or a dispersion in which the polymer acid is dispersed in a dispersion medium. The polymer acid solution is preferably a solution in which the polymer acid is dissolved in a solvent. Examples of the solvent include water and alcohol. The polymer acid, solvent, and dispersion medium may be used singly or in combination.

[0036] The polymer acid solution containing the polymer acid and a volatile solvent can be applied to the second electrode 2 of the pressing body made of CNT by spray coating, dipping, spin coating, etc. Among these, the polymer acid solution is preferred because it allows the polymer acid to be added little by little as a dopant, the pressing body made of CNT does not move from a predetermined position, there is little risk of the components of the adjacent hole transport layer 4 eluting when applied, and the I of the module 10 SC The spray coating method is superior in that it can increase the coating efficiency.

[0037] Therefore, by pressing a material containing CNTs to form a pressed body, and then applying a polymer acid solution to the pressed body to form the connecting wiring and the second electrode 2, an organic solar cell module with excellent performance can be obtained.

[0038] Doping the pressed CNT body with a polymeric acid by spray coating reduces the electrical resistance of the pressed body. Therefore, the second electrode 2 and connecting wire 6 containing doped CNT obtained by the above-described forming method are also useful as electrodes and connecting wires for solar cell modules other than organic solar cells.

[0039] From the viewpoint of lowering the electrical resistance of the CNT presser by doping, when Nafion (trademark) is used as the polymeric acid and isopropyl alcohol is used as the volatile solvent, the Nafion (trademark) concentration is preferably 0.20 to 2.0 wt%, more preferably 0.30 to 1.0 wt%. Alternatively, a mixture of PEDOT and PSS (PEDOT:PSS) may be used instead of Nafion as the polymeric acid. When PEDOT:PSS is used, the ratio and concentration of PEDOT and PSS are not particularly limited.

[0040] The absorption spectrum of CNT in the near infrared region includes S 11 A peak appears at wavelengths of 2200 to 2500 nm due to the transition, and S 22 The peak at wavelengths of 1100 to 1500 nm is due to the S transition. 11The peaks due to the S transition in the infrared absorption spectra of the interconnects and electrodes containing CNTs are weakened. 11 The absorption peak that appears at wavelengths of 2200 to 2500 nm due to the transition is S 22 If the peak is smaller than the peak appearing at wavelengths of 1100 to 1500 nm due to the transition, it indicates that the CNT is doped.

[0041] By integrally forming the connection wiring 6 and the second electrode 2, the area of ​​the region where the connection wiring 6 is located can be reduced when viewed along the Z direction. This makes it possible to increase the ratio of the conversion efficiency Em of the module 10 to the conversion efficiency Ec of the unit cell A. For example, it is possible to provide a module 10 in which the conversion efficiency Em of the module 10 and the conversion efficiency Ec of the unit cell A satisfy Em / Ec≧0.60, or even Em / Ec≧0.63, and in which a decrease in conversion efficiency due to modularization is suppressed.

[0042] The organic power generation layer 5 is a layer that performs photoelectric conversion and contains an electron acceptor compound and an electron donor compound. The organic power generation layer 5 absorbs received light, and electron transfer occurs at the interface between the electron acceptor compound and the electron donor compound, generating electrons and holes. The generated electrons are extracted from the first electrode 1 via the electron transport layer (ETL) 3, and the generated holes are extracted via the hole transport layer (HTL) 4.

[0043] Examples of the electron donor compound (electron donor) include condensed aromatic hydrocarbons such as naphthacene, pentacene, and pyrene; thiophenes (polythiophenes) having a thiophene ring such as α-sexithiophene; condensed polycyclic aromatic compounds such as pentacene and tetracene; phthalocyanine compounds and metal complexes thereof, porphyrin compounds such as tetrabenzoporphyrin and metal complexes thereof, macrocyclic compounds such as naphthalocyanine derivatives and porphyrin derivatives; conjugated polymer semiconductors such as polyfluorene, polyphenylenevinylene, polythienylenevinylene, polyacetylene, and polyaniline; oligomer semiconductors such as oligothiophenes substituted with alkyl groups or other substituents; and organic dyes such as diketopyrrolopyrrole derivatives and squaraine derivatives. Specific examples of the electron donor compound include benzoporphyrin (BP), polythiophene, polyphenylene, polyphenylenevinylene, polysilane, polycarbazole, polyvinylcarbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinylpyrene, polyvinylanthracene, thiophene-fluorene copolymer, polyalkylthiophene, phenyleneethynylene-phenylenevinylene copolymer, phenyleneethynylene-thiophene copolymer, phenyleneethynylene-fluorene copolymer, fluorene-phenylenevinylene copolymer, thiophene-phenylenevinylene copolymer, phthalocyanine-containing polymer, carbazole-containing polymer, and organic semiconductor polymers such as organometallic polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). Commercially available products include PV-D4610 (manufactured by Raynergy Tek) and PM6 (manufactured by Brilliant Matters Organic Electronics Inc.).

[0044] Examples of the electron acceptor compound (electron acceptor) include fullerene or a fullerene derivative; a fused ring tetracarboxylic acid diimide such as naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid diimide; and a fused polycyclic aromatic hydrocarbon such as a perylene derivative, a thiazole derivative, a benzothiazole derivative, or a benzothiadiazole derivative. Specific examples of the electron acceptor compound include polyphenylene vinylene, polyfluorene, derivatives thereof, copolymers thereof, carbon nanotubes (CNT), fullerene derivatives such as phenyl C61-butyric acid methyl ester (PCBM), polymers containing a cyano (CN) group or a trifluoromethyl (CF3) group, CF3 group-substituted polymers, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). Examples of fullerene derivatives include hydrogenated fullerene, oxidized fullerene, hydroxylated fullerene, aminated fullerene, sulfurized fullerene, halogenated (F, Cl, Br, I) fullerene, fulleroid, methanofullerene, pyrrolidinofullerene, alkylated fullerenes, and arylated fullerene. 61 BM (manufactured by Resonac), Y6 (manufactured by Brilliant Matters Organic Electronics Inc.), and the like.

[0045] As used herein, "fullerene" includes, for example, fullerene C60 (so-called Buckminsterfullerene), fullerene C70, fullerene C76, fullerene C78, ​​fullerene C82, fullerene C84, fullerene C90, fullerene C94, fullerene C96, and the like.

[0046] Examples of the structure of the organic power generation layer 5 include (1) a heterojunction type in which a layer made of an electron donor compound and a layer made of an electron acceptor compound are stacked together and photoinduced charge transfer is utilized at the junction interface, and (2) a bulk heterojunction type having a layer in which an electron acceptor compound and an electron donor compound are mixed.

[0047] Heterojunction active layers utilize photoinduced charge transfer at the junction interface by stacking layers of electron donors and electron acceptors. For example, in heterojunction active layers, copper phthalocyanine can be used as the electron donor compound and a perylene derivative as the electron acceptor compound. Furthermore, in heterojunction active layers, condensed polycyclic aromatic compounds such as pentacene and tetracene can be used as the electron donor compound and fullerenes such as C60 or fullerene derivatives can be used as the electron acceptor compound. In bulk heterojunction active layers, the junctions between the electron donor and electron acceptor compounds are uniformly present throughout the bulk of the mixed active layer, allowing for efficient use of light. Methods for fabricating bulk heterojunction devices include co-evaporating the electron donor and electron acceptor compounds by vacuum deposition (vacuum deposition method) to form the active layer, and applying a mixed solution of the two compounds by spin coating or printing (wet coating method). Examples of active layers that can be formed by vacuum deposition include those made of copper phthalocyanine and fullerene. Examples of active layers that can be formed by wet coating include a mixture of poly(3-hexylthiophene-2,5-diyl) (P3HT), a conjugated polymer, and [6,6]-phenyl C61-butylic acid methyl ester (PCBM), a soluble derivative of fullerene; a mixture of PTB7 (poly(thieno[3,4-b]thiophene / benzodithiophene)) and PC71BM ([6,6]-phenyl C71-butylic acid methyl ester); and a mixture of P3HT (regioregular, A representative example is a mixture of PCBM (Sigma Aldrich Chemical Co., Inc.) and mix-PCBM (Frontier Carbon Co., Nanom spectrum E124).

[0048] Furthermore, a compound having a perovskite structure (perovskite compound) can be used for the organic power generation layer 5. Examples of perovskite compounds include CH3NH3PbI 3-x Cl x(wherein x is 1 to 3), CH3NH3PbBr3, CH3NH3PbBrI2, CH3NH3PbBr2I, CH3NH3SnBr3, CH3NH3SnI3, CH(=NH)NH3PbI3, (C2H5NH3)2PbI4, (CH2=CHNH3)2PbI4, (CH≡CNH3)2PbI4, (C6H5NH3)2PbI4, (C6H3F2NH3)2PbI4, (C6F5NH3)2PbI4, (C4H3SNH3)2PbI4, etc. Among these compounds, CH3NH3PbI3 compound or CH3NH3PbI 3-x Cl x It is preferable to use a compound (wherein x is 1 to 3) in the organic power generation layer 5 .

[0049] In order to further increase the conversion efficiency in a bulk heterojunction active layer, the active layer may have a pin type three-layer structure consisting of an electron donor layer (active layer (p-layer)), a mixed layer of an electron donor compound and an electron acceptor compound (active layer (i-layer)), and an electron acceptor layer (active layer (n-layer)).

[0050] The thickness of the organic power generation layer 5 is not particularly limited, but is 10 nm to 1,000 nm, preferably 50 nm to 500 nm. A thickness of 10 nm or more of the organic power generation layer 5 is preferable because it maintains uniformity in thickness and reduces the likelihood of short circuits. Furthermore, a thickness of 1,000 nm or less of the organic power generation layer 5 is preferable because it reduces internal resistance and prevents excessive separation between electrodes, allowing for good charge diffusion.

[0051] The electron transport layer (ETL) 3 is provided to selectively and efficiently transport electrons generated by light absorption in the organic power generation layer 5 to the first electrode 1, thereby achieving high conversion efficiency. The electron transport layer 3 may be made of a compound such as CdS, ZnS, Zn(S,O) and / or Zn(S,O,OH), SnS, Sn(S,O) and / or Sn(S,O,OH), InS, In(S,O) and / or In(S,O,OH), TiO2, or In2S3.

[0052] The hole transport layer (HTL) 4 is provided to selectively and efficiently transport holes generated by light absorption in the organic power generation layer 5 to the second electrode 2, thereby achieving high conversion efficiency. The hole transport layer 4 may be made of a conductive polymer: polymer acid such as poly(3,4-ethylenedioxythiophene)poly(styrenesulfonic acid) (PEDOT:PSS).

[0053] The first substrate 11 and the second substrate 12 may be any substrate having light-transmitting properties, such as a transparent glass substrate, a ceramic substrate, or a light-transmitting plastic substrate. The first substrate 11 and the second substrate 12 may be, for example, in the form of a plate, a film, a sheet, or the like, but their shapes are not limited. Furthermore, the film thickness is also not limited, but from the viewpoint of achieving a module 10 with a good balance between strength and weight, the film thickness of each of the first substrate 11 and the second substrate 12 is, for example, approximately 5 μm to 20 mm, and preferably approximately 20 μm to 10 mm.

[0054] The second substrate 12 may be, for example, a protective film made of a film-like, light-transmitting plastic substrate. The above-described structure of the module 10 prevents short-circuiting between the first electrode 1 and the second electrode 2. This allows the module 10 to be sealed and laminated by applying pressure to the protective film.

[0055] The number of unit cells A connected in series can be set as appropriate, but can be, for example, four or more. From the viewpoint of practicality of the module 10, when four unit cells A are connected in series, it is preferable that the open circuit voltage is 2.70 V or more. From the same viewpoint, in this case, it is also preferable that the series resistance per unit cell A, obtained by dividing the series resistance of the module structure by four, which is the number of unit cells A, is 39 Ω / cell or less.

[0056] The second electrode 2 is formed from a first material containing carbon nanotubes (CNTs). CNTs are fibrous carbon materials with diameters of several nanometers. They are highly conductive, lightweight, flexible, and durable. Furthermore, carbon, the raw material, is abundant on Earth, chemically stable, and has a low environmental impact. Therefore, in the present invention, CNTs are used as the second electrode (rear electrode) of the organic solar cell module.

[0057] In the module 10, when the second electrode 2 is formed by a transfer method, the connection wiring 6 and the second electrode 2 are integrally formed from a first material containing CNTs, thereby making it possible to integrally configure the connection wiring 6 and the second electrode 2 as a pressed body made of a material containing CNTs.

[0058] From the viewpoint of improving the performance of the module 10, the surface resistivity of the first material constituting the connection wiring 6 and the second electrode 2 is preferably 5 Ω / □ or more.

[0059] The length (thickness) D1 of the second electrode 2 in the Z direction may be set as appropriate, but may be, for example, 0.50 μm or less. The carbon nanotubes contained in the first material constituting the second electrode 2 preferably have an average length of 1 μm or more.

[0060] The length (thickness) D2 in the Z direction of the power-generating laminate 7 constituting the unit cell A is preferably small (thin) from the viewpoint of increasing light transmittance. D2 is 0.15 μm or more to form each layer constituting the power-generating laminate 7. Furthermore, from the viewpoint of ensuring the performance of each layer, D2 is preferably 1.0 μm or more.

[0061] The module 10 has a transmittance of 18% or more, preferably 30% or more, and more preferably 50% or more at chloroplast absorption wavelengths, as measured by a measurement method based on JIS K7375:2008. Increasing the transmittance at chloroplast absorption wavelengths enables effective use of sunlight in the cultivation of crops and aquaculture beneath the module 10.

[0062] From the viewpoint of effectively utilizing sunlight and improving power generation efficiency, it is preferable that the surface reflectance of the module 10 be low. When polycarbonate is used as the first substrate 11 and the second substrate 12, the surface reflectance is approximately 50%, but by using acrylic or PET, the reflectance can be reduced to 10% or less, or even 8% or less. Furthermore, by using a film with a moth-eye structure that mimics the micro-convex and concave structure of a moth's eye (moth-eye), the surface reflectance can be reduced to 1% or less, or even 0.1% or less. In this embodiment, the surface reflectance refers to the total light reflectance measured by a measurement method in accordance with JIS K7375:2008.

[0063] Test Examples 1 to 3 An electron transport layer 3, an organic power generation layer 5, and a hole transport layer 4 were formed by spin coating on a first substrate 11 and a first electrode 1 having the following configuration. Subsequently, a glass substrate was pressed against the CNTs on the filter to transfer the CNT thin film, integrally forming a second electrode (rear electrode) 2 and connecting wiring 6, and a module (semi-module) 10 having a structure in which four unit cells A, each 6 mm wide and 28 mm long, were connected in series was produced.

[0064] (First substrate 11 / first electrode 1) A 37 mm square glass substrate (manufactured by Technoprint) was used, on which ITO (indium-tin oxide) had been patterned in advance so that 1 mm x 37 mm grooves were formed at positions 4 mm, 12 mm, 20 mm, and 28 mm from the edge of the substrate. First, the substrate surface was irradiated with UV / O3 for 15 minutes to clean and hydrophilize it.

[0065] (Second Electrode 2, Connection Wiring 6) CNTs with an average length of approximately 3 μm, synthesized by a gas-phase flow method, were used as the second electrode 2 and connection wiring 6. Methane gas was used as the carbon source, and ferrocene, an organometallic compound containing iron atoms, was used as the catalyst precursor. These materials were flowed into a tubular furnace at approximately 1000°C to synthesize CNTs. The CNTs synthesized in the furnace were collected in a collection section. A membrane filter (manufactured by Merck Millipore, pore size 1.2 μm) made of a cellulose mixed ester was used as the collection filter. By placing the filter on a patterned metal mask, CNTs could be collected in the pattern of the mask. In this example, a pattern of four rectangles, each 6 mm wide and 28 mm long, was used. The collection time was approximately 1200 seconds, and the second electrode 2 and connection wiring 6 were formed so that the transmittance of visible light at λ = 550 nm was 85%. The transmittance was measured by irradiating the sample with light from a light source using a halogen lamp (manufactured by Ocean Insight) and detecting the light transmitted through the sample with a spectrometer (manufactured by Ocean Insight), thereby measuring the transmission spectrum. sheet showed a value of 210 to 310 Ω / sq. The CNTs produced by TEM imaging were single-walled carbon nanotubes (SWCNTs) with a diameter of approximately 2 nm, and Raman spectroscopy confirmed that they were SWCNTs with few defects. Note that while CNTs produced by a gas-phase flow method were used in this example, CNTs obtained by a wet process and with an average length of approximately 1 to 2 μm may also be used.

[0066] In Test Examples 1 and 2, the second electrode 2 and connecting wiring 6 were fabricated by transferring a CNT thin film. The transfer was performed by pressing a glass substrate against the CNTs on the filter. In this way, the CNT thin film can be easily formed on a target substrate by transfer. One of the advantages of using a CNT thin film is that the film formation process does not require vacuum equipment. In Test Example 3, which was equipped with a metal electrode, a silver film (purity 99.99%) of approximately 100 nm was formed by vacuum deposition to form the second electrode 2 and connecting wiring 6. After the second electrode 2 was formed, copper tape was attached as an auxiliary electrode to the ITO portion (first electrode 1) from which current was extracted. During measurement, light was incident on the entire surface of the module 10. In this case, the effective power generation area per element was 1.12 cm 2 The entire module 10 is 4.48 cm 2 It was decided.

[0067] (Electron Transport Layer 3) As a pretreatment for film formation, a ZnO dispersion with a ZnO concentration of 3.0 wt % was prepared using ethanol. Film formation using the ZnO dispersion was performed by spin coating. Approximately 600 μL of the ZnO dispersion was dropped onto the substrate using a hydrophilic filter, and spin coating was performed at a rotation speed of 1000 rpm. After spin coating, annealing was performed at 80°C for 2 minutes. Next, a PEI (polyethyleneimine) solution with a concentration of 0.2 mg / mL was prepared, and a film was formed on the ZnO by spin coating. Approximately 600 μL of the PEI (polyethyleneimine) solution was dropped onto the substrate using a hydrophilic filter, and spin coating was performed at 2000 rpm. After spin coating, annealing was performed at 80°C for 2 minutes.

[0068] (Hole Transport Layer 4) As a pretreatment for film formation, the PEDOT:PSS aqueous dispersion was subjected to ultrasonic irradiation for 20 minutes. The PEDOT:PSS aqueous dispersion was formed into a film using spin coating. Approximately 1500 μL of the PEDOT:PSS aqueous dispersion was dropped onto the substrate, and then spin coated at 1000 rpm. Three 2 mm-wide grooves were then created to allow contact between the CNTs and ITO. The excess layer was wiped off to expose the ITO portion that would serve as the extraction electrode. A toothpick and a cotton swab soaked in acetone or water were used to create the grooves and wipe off the excess layer.

[0069] (Organic power generation layer 5) PV-D4610 (manufactured by Raynergy Tek) was used as the donor material, and PC was used as the acceptor material. 61 First, to prepare the power generation layer solution, 15 mg of PV-D4610 and PC 61 30 mg of BM was weighed out and placed in a brown vial. Then, 1 mL of ODCB (orthodichlorobenzene) was added to prepare a solution. The organic power generation layer 5 was formed by spin coating. Approximately 700 μL of the solution was dropped onto the substrate using a hydrophobic filter, and then spin coated at 600 rpm. After spin coating, the substrate was annealed at 70° C. for 2 minutes.

[0070] 2 is a photograph showing the appearance of the organic solar cell module fabricated in this example. On the left side, CNT thin film electrodes were used as the second electrode 2 and the connecting wiring 6 (Test Examples 1 and 2), and on the right side, silver electrodes were used as the second electrode 2 and the connecting wiring 6 (Test Example 3).

[0071] Test Examples 2 and 3 were conducted similarly to Test Example 1, except that poly(3-hexylthiophene-2,5-diyl) (P3HT) was used as the electron donor in the organic power generation layer 5 instead of PV-D4610. Figure 3 is a photograph showing a cross-sectional image of a single cell A in a module 10 using a CNT thin-film electrode as the second electrode 2, as observed by TEM. As shown in the figure, it can be seen that a ZnO layer (electron transport layer 3), an organic power generation layer 5, a PEDOT:PSS layer (hole transport layer 4), and a CNT layer (second electrode 2) are formed on an ITO (first electrode 1) / glass substrate (first base material 11) in the order of thickness, with thicknesses of approximately 10 nm, 100 nm, 50 nm, and 100 nm, respectively. The spherical materials scattered throughout the CNT layer are CNT catalyst particles.

[0072] The current-voltage characteristics of the fabricated organic solar cell module were measured under simulated sunlight irradiation. A solar simulator (single cell: manufactured by ASAHI SPECTRA, semi-module: manufactured by USHIO SPAX) using a xenon lamp as a light source was used as the simulated sunlight. The irradiation intensity of the incident light was AM1.5G: 100 mW / cm using a silicon reference cell. 2This is an internationally established standard value for consistent performance measurements. The current-voltage characteristics were measured by the four-terminal method using a low-voltage source meter (manufactured by Keithley).

[0073] Figure 9 shows the IV curve (current-voltage curve) of a typical solar cell. Each parameter indicating the photoelectric conversion characteristics can be estimated from the current-voltage curve. SC ) is the current when no voltage is applied. OC ) is the voltage when no current is flowing. SC , V OC are the maximum current and voltage that the solar cell can exhibit, but the maximum output that can actually be extracted is I SC and V OC This is not the product of the series resistance (R S ) and parallel resistance (R SH This is due to the influence of R S is V OC R is the inverse of the slope of the curve near the center of the photovoltaic cell, and represents the magnitude of the electrical resistance in the carrier transport path inside the organic solar cell. The main causes are the contact resistance of the electrodes and the bulk resistance of the electrode material itself, and R S A smaller value is desirable. SH is I SC It is the inverse of the slope of the slope near the ETL and represents the magnitude of the leakage current of the solar cell. For example, if the electrode penetrates the ETL or HTL, R SH When the resistance of the parallel component to the junction becomes low in this way, it can cause leakage current, so R SH A larger value is preferable.

[0074] Due to the influence of these resistance components, the curve showing the output characteristics is SC and V OC The maximum power generated by the solar cell (P MAX ) is the maximum generated current (I MAX ) and maximum power generation voltage (V MAX ) and is the area of ​​the rectangle inscribed in the current-voltage curve (the inner rectangle in FIG. 9). MAX I SC and VOC The value obtained by dividing the FF by the product of the FF and the power conversion efficiency (PCE) is called the fill factor (FF). FF is an index that indicates the performance of solar cell characteristics, and the better the solar cell, the closer it is to 1. The power conversion efficiency (PCE) is calculated by dividing the FF by the power conversion efficiency (PCO) of the solar cell when the energy of irradiated light is 100 mW / cm 2 In this case, it can be expressed by the following formula: PCE [%] = I SC ×V OC ×FF and below are mainly I SC , V OC , R S , R SH , FF, and PCE were used to evaluate the performance of the OPV.

[0075] 4 is a graph showing the IV curves of the organic solar cell modules of Test Examples 1, 2, and 3. The effective power generation area was 1.12 cm per single cell A. 2 The entire module 10 is 4.48 cm 2 The graph shows the open circuit voltage (V oc ) is shown, indicating that a module 10 in which four unit cells A are connected has been produced. The manufacturing method of forming the connection wiring 6 integrally with the second electrode 2 using a first material containing CNTs by mechanical transfer requires little effort and burden during film formation, making it an excellent manufacturing method in terms of cost. Furthermore, the organic solar cell modules (modules 10) of Test Examples 1 and 2 exhibited roughly the same conversion efficiency even when light was incident from the back electrode side (second electrode 2 side). This is a significant advantage not seen in solar cells using conventional metal electrodes.

[0076]

[0077] The module 10 of Test Example 1, which was formed by connecting four unit cells A in series via the connecting wiring 6, had an open circuit voltage of 2.90 V or more and a series resistance per unit cell of 39 Ω / cell or less, and thus had practical performance. The ratio Em / Ec of the conversion efficiency Em of the module 10 to the conversion efficiency Ec of the unit cell A was 0.63.

[0078] (Test Examples 4 to 6: CNT doping by spray coating) When a CNT film was used as the second electrode 2, the DC resistance (R s) tended to increase. The reason for this is presumably due to the structure of the CNT. That is, CNTs have a network structure in which thin fibers are entangled, which creates gaps, which reduces the number of carrier transport paths compared to silver electrodes, and is thought to increase the resistance of the module 10 as a device. Therefore, we focused on the adhesion and resistance of the CNT thin film and investigated the effects of applying a volatile solvent and drying it after forming a CNT pressed body, and applying a polymer acid solution containing a polymer acid and a volatile solvent and drying it.

[0079] Modules 10 of Test Examples 4 to 6 were fabricated in the same manner as Test Example 1. The performance of the fabricated modules 10 was evaluated before and after isopropyl alcohol (IPA) as a volatile solvent and an IPA solution containing a polymer acid (polymer acid solution) were applied to the second electrode 2 by spraying.

[0080] FIG. 5 is a schematic diagram showing the configuration of the spray coating device (manufactured by Asahi Sunac Corporation) used in Test Examples 4 to 6. Spray coating was performed using the device shown in the figure as follows. First, the fabricated module 10 was placed on the sample stage. The sample stage was positioned 10 cm away from the nozzle, and the temperature of the stage surface was maintained at 90°C. Next, a syringe containing the liquid to be sprayed was fixed to the syringe pump. Coating began when the syringe pump pushed out the syringe. The syringe pump was digitally controlled, allowing the discharge flow rate of the liquid to be sprayed to be maintained constant. The discharge flow rate was set to 3.2 mL / min. During spray coating, the spray nozzle moved to the right as viewed in FIG. 5, and the sample stage moved toward the front and rear of FIG. 5. A total of five coatings were performed, with each coating performed while the nozzle reached the right end counting as one coating.

[0081] The following polymeric acids and IPA were mixed to prepare solutions with the concentrations shown in Table 2. The prepared solutions were used after 15 minutes of ultrasonic irradiation. However, for PEDOT:PSS, the solution was prepared based on the state of the aqueous dispersion. For example, when 500 mg of PEDOT:PSS aqueous dispersion was mixed with 9,500 mg of IPA, the concentration of PEDOT:PSS was 5.0 wt%. (Volatile solvent) - Isopropyl alcohol (IPA) (Polymeric acids) - PEDOT:PSS (manufactured by Arakawa Chemical Industries, Ltd.) - Nafion (Nafion, trademark, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0082]

[0083] The current-voltage characteristics of the fabricated module 10 were measured under irradiation with simulated sunlight. A solar simulator (single cell: manufactured by ASAHI SPECTRA, semi-module: manufactured by USHIO SPAX) using a xenon lamp as a light source was used as the simulated sunlight. The irradiation intensity of the incident light was AM1.5G: 100 mW / cm using a silicon reference cell. 2 The current-voltage characteristics were measured by the four-terminal method using a low-voltage source meter (manufactured by Keithley).

[0084] FIG. 6 is a graph showing the IV curves of module 10 before and after spray application of a solution of 10.0 wt % PEDOT:PSS and 0.5 wt % Nafion, a polymer acid solution prepared by dissolving a polymer acid in a volatile solvent. Table 2 shows the characteristic values ​​of modules 10 for Test Examples 4 to 7. As shown in these figures and tables, spray application of a polymer acid solution containing IPA, a volatile solvent, was found to improve the solar cell characteristics of module 10. This improvement in characteristics is believed to be due to improved adhesion between the second electrode 2 composed of CNTs and the hole transport layer 4 (HTL) resulting from the process of spraying and drying IPA.

[0085] Furthermore, the characteristics of the solar cell were improved by adding a polymeric acid to the IPA applied to the second electrode 2. This improvement in characteristics is believed to be due to the polymeric acid's ability to reduce the resistance of the second electrode 2. In addition to the improvement in adhesion and the reduction in series resistance due to the doping effect of the polymeric acid, an increase in shunt resistance was also confirmed. This effect is believed to be due to the backfilling of pinhole defects.

[0086]

[0087] (Test Examples 7 and 8) For a CNT thin film (transmittance of about 85%, sheet resistance of about 300 Ω / sq) using SWCNT, the sheet resistance R sheet The sheet resistance R of the SWCNTs was measured. sheet The measurement results are shown below.

[0088] (Measurement of Sheet Resistance Value) The resistance of SWCNT is measured by the sheet resistance value R sheet The evaluation was carried out by measuring Ω / sq. The four-probe method was used as the evaluation method. First, a four-probe prober (manufactured by Hisol) with a needle spacing of 1 mm was used to apply a current to the sample and detect the voltage generated when the current was applied. No electrodes were formed on the sample, and the sheet resistance was calculated using the following formula, taking the resistance value R shown when the prober was directly applied. I (A) is the applied current, and V (V) is the detected voltage. The average value of values ​​measured at three different points on the same sample was taken as the sheet resistance. R sheet =V / I×π / ln2=R×4.5324Ω / sq

[0089] (Raman spectroscopy measurement) Raman spectroscopy measurement was performed to evaluate the structure of the CNT thin film using SWCNT. An inViaReflex (manufactured by Renishaw) was used for the measurement. The wavelength of the excitation laser was 532 nm, and the diameter of the laser spot was approximately 1 μm. The measurement conditions were an exposure time of 10 seconds, an accumulation count of 1, and a laser output of 0.1%.

[0090]

[0091] As shown in Table 3, by applying an alcohol solution of polymer acid (PEDOT:PSS, Nafion, solvent IPA), the sheet resistance R sheet The change in Raman spectrum due to spray application of the alcohol solution of polymeric acid was reduced. A magnified portion of the graph in Figure 7A, showing the change in Raman spectrum due to spray application of the alcohol solution of polymeric acid, is shown in Figure 7B. In Figure 7B, the G band in the Raman measurement of SWCNTs shifts to a higher wavenumber due to the effect of doping. The results in Table 3, Figures 7A, and 7B indicate that the SWCNTs were p-doped.

[0092] SWCNTs are oxidized by oxygen in the air and are already slightly p-doped. Further oxidation with a polymeric acid enhances the p-doping effect, lowering the sheet resistance of the SWCNTs. While using silver as the second electrode clearly degrades battery performance due to oxidation, using CNTs as the second electrode, as in the organic solar cell module of the present invention, makes it possible to realize solar cells whose performance improves through oxidation. In other words, by using CNTs as the second electrode (rear electrode), oxygen adsorption, which is one of the causes of durability degradation, becomes a doping material for the CNTs, thereby lowering the resistance of the CNTs and increasing the efficiency of the solar cell. This allows for the realization of a solar cell module whose performance improves through oxidation.

[0093] (Test Example 9) Nitric acid, which is commonly used as a dopant, was used. The doping method involved exposing the module 10 to nitric acid vapor for one hour. The sheet resistance of the CNT thin film was 163.8 Ω / sq after nitric acid doping, and the sheet resistance was reduced by approximately 54.5% from 359.9 Ω / sq before nitric acid doping due to nitric acid aeration. This indicates that nitric acid is an effective dopant for lowering the resistance of CNT thin films. Figure 8 shows the current-voltage curves of the CNT-OPV semi-module before and after nitric acid doping. Table 4 also shows the film performance of the CNT used and various parameters of the module 10. As shown in these figures and tables, it was found that the performance of the module 10 was significantly deteriorated as a result of nitric acid doping. In particular, R S The value increases, and I SCThe reason for this is thought to be the oxidation and deterioration of the power generation layer due to nitric acid vapor.

[0094]

[0095] (Test Example 10) Figure 10 shows the IV curves of the solar cell module 10 before and after application of PEDOT:PSS. Table 5 also shows the film performance of the CNT thin film used and various parameters of the module 10. In Test Example 10, almost no change was observed at a PEDOT:PSS concentration of 1.0 wt%. On the other hand, at PEDOT:PSS concentrations of 5.0 wt% and 10.0 wt%, the I SC has improved by approximately 10%, and R SH As a result, the PCE increased by approximately 30%, reaching a value of approximately 2.7-2.8%.

[0096]

[0097] (Test Example 11) Figure 11 shows the IV curves of the solar cell module 10 before and after applying Nafion. Table 5 also shows the film performance of the CNT thin film used and various parameters of the module 10. In Test Example 11, almost no change was observed at a Nafion concentration of 0.050 wt%. On the other hand, at Nafion concentrations of 0.25 wt% and 0.50 wt%, the IV curves were SC has improved by approximately 10%, and R SH As a result, PCE increased by approximately 30%, reaching a value of 2.8-2.9%.

[0098]

[0099] The results shown in FIGS. 10 and 11 and Tables 5 and 6 indicate that the performance of the solar cell module 10 improves with increasing concentrations of PEDOT:PSS and Nafion used as dopants.

[0100] The PCE of the solar cell of module 10 improved by approximately 10% from 1.96% to 2.21% in Test Example 6, in which only IPA was sprayed onto the CNT thin film. Meanwhile, the PCE improved by approximately 30% from 2.05% to 2.70% in Test Example 10, in which 10.0 wt% PEDOT:PSS was sprayed, and the PCE improved by approximately 30% from 2.09% to 2.80% in Test Example 11, in which 0.50% Nafion was sprayed. These results suggest that one-third of the improvement in PCE achieved by spraying PEDOT:PSS or Nafion onto the CNT thin film is due to improved adhesion of the CNT thin film. Therefore, the remaining two-thirds can be attributed to other factors.

[0101] A possible factor in improving performance, other than adhesion, is the decrease in the resistance of the CNT thin film due to doping. As shown in Table 3, it was found that spraying PEDOT:PSS or Nafion reduces the sheet resistance of the CNT thin film. However, this result does not clearly indicate that the decrease in the sheet resistance of the CNT thin film is due to doping. Therefore, the near-infrared absorption spectrum of the spray-coated CNT thin film was measured. The measurement sample was prepared by transferring the CNT thin film onto a glass substrate and spray-coating it under the same conditions as when fabricating module 10.

[0102] It has been reported that doped CNTs exhibit a disappearance of absorption peaks in the near-infrared region [A. Kaskela et al., Nano Lett. 10, 4349 (2010)., R. Jacquemin et al., Synthetic Metals, 115, 283 (2000)]. Figure 12 is a schematic diagram illustrating the mechanism by which doping causes the disappearance of absorption peaks in the near-infrared region. Semiconducting SWCNTs typically exhibit a divergence in the electronic density of states known as the VHS, or van Hove singularity (VHS), and optical absorption occurs due to these interband transitions. However, when the number of holes in SWCNTs increases due to dopant adsorption, the Fermi level of the SWCNTs shifts downward. This is thought to result in a decrease in the probability of VHS transitions, i.e., the existence of electrons contributing to absorption, resulting in the disappearance of the absorption peak.

[0103] Figure 13 shows the absorption spectrum in the near infrared region of the CNT thin film sprayed with IPA and PEDOT:PSS solution. 11 The absorption peak appears at a wavelength of 2200 to 2500 nm due to the transition, and 22 The absorption peaks appearing at wavelengths of 1100 to 1500 nm due to the transition were observed. These two peaks were also observed in the CNT thin film with a PEDOT:PSS concentration of 1.0 wt%. On the other hand, when the PEDOT:PSS concentration was 5.0 wt% and 10.0 wt%, the S 11 It was found that the peaks due to the transition were slightly weakened. 11 The absorption peak due to the transition is S 22 The absorption peak due to the transition was smaller than that of the

[0104] Figure 14 shows the absorption spectrum in the near-infrared region of the CNT thin film sprayed with IPA and Nafion solution. When the Nafion concentration was 0.05 wt%, the S 11 Transitions and S 22However, when the Nafion concentration was 0.25 wt% and 0.50 wt%, the S 11 The peak of S disappears, 22 The peak of S is significantly weakened, 11 The absorption peak due to the transition is S 22 The absorption peak due to the transition was smaller than that of the

[0105] The absorption spectra shown in Figures 13 and 14 indicate that the decrease in sheet resistance of the CNT thin film is due to the doping effect of PEDOT:PSS and Nafion. That is, the hole doping of the CNT thin film was confirmed by measuring the near-infrared absorption spectrum and Raman spectrum. We also confirmed that the surface sheet resistance of the CNT thin film actually decreased.

[0106] As explained above, by coating the SWCNT second electrode 2 and the connecting wiring 6 with an IPA solution containing Nafion, the connection between the single cells A was ensured, and the protons possessed by the sulfonic acid in Nafion were doped into the SWCNT, thereby injecting holes. The doping of holes was confirmed by measuring near-infrared absorption spectroscopy and Raman spectroscopy. It was also confirmed that the surface sheet resistance of the second electrode 2 and the connecting wiring 6 formed from SWCNT actually decreased.

[0107] Furthermore, by coating the SWCNT second electrode 2 and the connecting wiring 6 with an IPA solution of PEDOT:PSS, the connection between the single cells A is ensured, and the protons possessed by the sulfonic acid of the PSS are doped into the SWCNT, injecting holes. The hole doping was confirmed by measuring near-infrared absorption spectroscopy and Raman spectroscopy. It was also confirmed that the surface sheet resistance of the second electrode 2 and the connecting wiring 6 formed from SWCNT actually decreased.

[0108] 15 is a photograph, shown as a substitute for a drawing, of a cross section of a single cell of the organic solar cell module of Test Example 1, which was fabricated using a CNT thin film electrode as the second electrode 2, and observed with a scanning electron microscope (SEM) after applying IPA (a volatile solvent). As shown in the figure, a CNT thin film electrode with a thickness of about 100 to 150 nm was formed on the PEDOT:PSS layer.

[0109] (Test Examples 13 and 14) In order to investigate the effect of applying a volatile solvent to a pressed body formed by pressing a material containing carbon nanotubes, two single cells were fabricated: one in which IPA was spray-coated as a volatile solvent onto the CNT thin-film electrode of the single cell of Test Example 12 (Test Example 13), and one in which IPA was dripped onto the CNT thin-film electrode and then spin-coated (Test Example 14). Then, the IV curves of the single cells of Test Examples 13 and 14 were measured.

[0110] FIG. 16 is an IV curve showing the measurement results of Test Examples 13 and 14. The measurement results are shown in Table 7. As shown in FIG. 16 and Table 7, Test Example 13, in which IPA was spray-coated, had a larger I than Test Example 14, in which IPA was applied by dripping and then spin-coating. SC These results demonstrate that spray coating is a superior method for applying IPA.

[0111] The embodiments disclosed in this specification are illustrative in all respects and are not limited to these embodiments. The scope of the present invention is defined by the claims rather than by the description of the above-described embodiments alone, and is intended to include all modifications within the meaning and scope of the claims.

[0112] INDUSTRIAL APPLICABILITY The present invention is useful as an organic solar cell module, an electrode for an organic solar cell module, and a method for producing an organic solar cell module that are highly practical.

[0113] 1: First electrode 2: Second electrode 3: Electron transport layer 4: Hole transport layer 5: Organic power generation layer 6: Connection wiring 7: Power generation laminate 10: Module 11: First substrate 12: Second substrate A: Single cell A1: Single cell A2: Single cell A3: Single cell D1: Length D2: Length Ec: Conversion efficiency Em: Conversion efficiency

Claims

1. An organic solar cell module having a module structure in which a plurality of unit cells each having: a power-generating stack having a laminate structure including a first electrode and a second electrode, both of which are transparent and opposed to each other in a first direction; an electron transport layer, a hole transport layer, and an organic power-generating layer located between the electron transport layer and the hole transport layer, which are aligned in the first direction, one of the electron transport layer and the hole transport layer being positioned opposite the first electrode, and the other of the electron transport layer and the hole transport layer being positioned opposite the second electrode; and a first substrate and a second substrate, both of which are transparent and opposed to each other in the first direction, with the first substrate and the first electrode facing each other and spaced apart so as to be aligned in an in-plane direction of an intersecting plane of the first direction; and a connection wiring between a first cell and a second cell, which are two adjacent unit cells among the plurality of unit cells, connecting the first electrode of the first cell and the second electrode of the second cell, wherein the connection wiring and the second electrode are integrally formed from a first material containing carbon nanotubes.

2. The organic solar cell module according to claim 1, wherein the second electrode has a transmittance of 14% or more for light with a wavelength λ of 550 nm.

3. The organic solar cell module according to claim 1, wherein the second substrate is a protective film.

4. The organic solar cell module according to claim 1, wherein at least four of the single cells are connected in series via the connecting wiring, and the open circuit voltage is 2.70 V or higher.

5. The organic solar cell module according to claim 1, wherein, when the module structure has a structure in which four of the unit cells are connected in series using the connecting wiring, the series resistance per unit cell obtained by dividing the series resistance of the module structure by 4, which is the number of the unit cells, is 39 Ω / cell or less.

6. The organic solar cell module according to claim 1, wherein the first electrode is made of an oxide-based material.

7. The organic solar cell module according to claim 1, wherein the first electrode is made of a material containing the carbon nanotubes.

8. The organic solar cell module according to claim 1, wherein the first electrode is made of a metal-based material.

9. The first material contains the carbon nanotubes and has an S in the absorption spectrum in the near infrared region. 11 The absorption peak that appears at wavelengths of 2200 to 2500 nm due to the transition is S 22 2. The organic solar cell module according to claim 1, wherein the peak is smaller than a peak appearing at a wavelength of 1100 to 1500 nm due to a transition.

10. The organic solar cell module according to claim 1, wherein the surface resistivity of the first material is 5 Ω / □ or more.

11. The organic solar cell module according to claim 1, wherein the length of the second electrode in the first direction is 0.50 μm or less, and the average length of the carbon nanotubes contained in the first material is 1 μm or more.

12. The organic solar cell module according to claim 11, wherein the length of the power generating laminate in the first direction is 0.15 μm or more.

13. An organic solar cell module according to claim 1, having a transmittance of 18% or more at chloroplast absorption wavelengths measured by a measurement method based on JIS K7375:2008.

14. The organic solar cell module according to claim 1, having a total light reflectance of 10% or less as measured by a measurement method in accordance with JIS K7375:2008.

15. The organic solar cell module according to claim 4, wherein the conversion efficiency Em of the module structure and the conversion efficiency Ec of the single cell satisfy Em / Ec ≥ 0.

60.

16. Contains carbon nanotubes and has S in the infrared absorption spectrum 11 The peak that appears at wavelengths of 2200 to 2500 nm due to the transition is S 22 The electrode for a solar cell module is characterized in that the peak is smaller than the peak appearing in the wavelength range of 1100 to 1500 nm due to transition.

17. The electrode for a solar cell module according to claim 16, which is formed integrally with a connection wiring that electrically connects two adjacent unit cells in a solar cell module.

18. A method for manufacturing an organic solar cell module as described in claim 1, characterized in that the second electrode and the connecting wiring are formed by pressing a material containing the carbon nanotubes to form a pressed body, and a polymeric acid is applied to the second electrode and the connecting wiring to dope holes into the carbon nanotubes.

19. The method for producing an organic solar cell module according to claim 18, wherein the polymeric acid has a sulfo group.

20. The method for producing an organic solar cell module according to claim 18, wherein the polymeric acid is PEDOT:PSS or Nafion.

21. The method for producing an organic solar cell module according to claim 18, wherein a volatile solvent is applied to the second electrode and the connecting wiring.

22. The method for producing an organic solar cell module according to claim 21, wherein the volatile solvent is applied to the second electrode and the connecting wiring by spray coating.

23. The method for producing an organic solar cell module according to claim 21, wherein the volatile solvent is a lower alcohol having 3 or less carbon atoms.

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