Solar cell

Abstract

This solar cell is provided with a pair of electrodes (2, 3) and an active layer (1). The active layer is located between the pair of electrodes and absorbs light to generate electrons and holes. The pair of electrodes are composed of an electron collecting electrode (3) for collecting electrons and a hole collecting electrode (2) for collecting holes. The electron collecting electrode contains a carbon nanotube (31) and an electron donating material (32). This configuration makes it possible to provide a solar cell capable of achieving high energy conversion efficiency while reducing material costs.

Description

solar cells CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2024-32056 filed on March 4, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to solar cells.

[0003] Solar cells have traditionally used transparent electrodes that are electrically conductive. Among these, indium tin oxide (ITO) is currently widely used as the mainstream transparent electrode material. However, indium is a rare metal, and there are concerns about its cost and supply stability.

[0004] In response to this, Patent Document 1 discloses a solar cell that uses a carbon nanotube film as a translucent electrode. By employing a carbon nanotube film as the translucent electrode, high energy conversion efficiency can be achieved at low cost.

[0005] Patent No. 7191310

[0006] Carbon nanotubes become p-type semiconductors, especially when handled in air, and have the ability to transport and collect holes. For this reason, carbon nanotube films are generally used in solar cells as hole-collecting electrodes that collect holes.

[0007] In response to this, the present inventors have investigated the use of a carbon nanotube film as an electron collecting electrode that collects electrons. However, it has become clear that when a carbon nanotube film is used as an electron transport electrode, the ability to transport and collect electrons may be insufficient. For this reason, it is difficult to employ a carbon nanotube film as an electron collecting electrode, and there is a possibility that the effect of reducing material costs may not be fully achieved.

[0008] In view of the above, an object of the present disclosure is to provide a solar cell that can achieve high energy conversion efficiency while reducing material costs.

[0009] In order to achieve the above object, a solar cell according to one embodiment of the present disclosure includes a pair of electrodes and an active layer located between the pair of electrodes that absorbs light and generates electrons and holes, wherein the pair of electrodes are composed of an electron collecting electrode that collects electrons and a hole collecting electrode that collects holes, and the electron collecting electrode contains carbon nanotubes and an electron donating material.

[0010] According to this, by incorporating carbon nanotubes and an electron donor material into the electron collecting electrode, the main carriers in the electron collecting electrode can be converted from holes to electrons. Therefore, even when carbon nanotubes are used as the electron collecting electrode, electrons generated in the active layer can be collected. Therefore, since carbon nanotubes can be used as the electron collecting electrode, it is possible to achieve high energy conversion efficiency while reducing material costs.

[0011] FIG. 2 is an explanatory diagram showing a layered structure of a solar cell according to one embodiment. FIG. 3 is an explanatory diagram showing an electron collecting electrode, an electron transport layer, and an active layer in one embodiment. FIG. 4 is an enlarged view of part III in FIG. 2. FIG. 5 is a characteristic diagram showing the relationship between temperature difference and thermoelectromotive force in a CNT transparent electrode. FIG. 6 is a characteristic diagram showing the relationship between current and voltage during light irradiation. FIG. 7 is an explanatory diagram showing an electron collecting electrode, an electron transport layer, and an active layer in a comparative example. FIG. 8 is an explanatory diagram showing a layered structure of a solar cell according to another embodiment (2).

[0012] An embodiment of the present disclosure will now be described with reference to the drawings. As shown in Figure 1, a solar cell 10 of this embodiment includes an active layer 1, a pair of electrodes 2 and 3, a light-transmitting substrate 4, a hole transport layer 5, and an electron transport layer 6.

[0013] The active layer 1 is disposed between a pair of electrodes 2 and 3. The active layer 1 is a photoelectric conversion element that absorbs light and generates electrons and holes.

[0014] The pair of electrodes 2, 3 is composed of a hole collecting electrode 2 and an electron collecting electrode 3. The hole collecting electrode 2 collects holes generated by light absorption in the active layer 1. The electron collecting electrode 3 collects electrons generated by light absorption in the active layer 1 and transports the collected electrons to an external circuit (not shown).

[0015] As an example, in this embodiment, the hole collecting electrode 2 is a light-transmitting electrode, and the electron collecting electrode 3 is a counter electrode. The hole collecting electrode 2 is provided directly or indirectly on the light-transmitting substrate 4. In this specification, "provided indirectly" means that the electrode is provided via another film or the like.

[0016] The hole transport layer 5 extracts holes generated in the active layer 1 toward the hole collecting electrode 2, and blocks electrons from flowing into the hole collecting electrode 2. The hole transport layer 5 is provided directly or indirectly on the hole collecting electrode 2. The active layer 1 is provided directly or indirectly on the hole transport layer 5.

[0017] The electron transport layer 6 extracts electrons generated in the active layer 1 to the electron collecting electrode 3 side, and blocks holes from flowing into the electron collecting electrode 3 side. The electron collecting electrode 3 is provided directly or indirectly on the active layer 1. The electron collecting electrode 3 is provided directly or indirectly on the electron transport layer 6.

[0018] That is, the solar cell 10 of this embodiment includes an active layer 1, a hole collecting electrode 2, an electron collecting electrode 3, a light-transmitting substrate 4, a hole transport layer 5, and an electron transport layer 6. The solar cell 10 of this embodiment is a solar cell element in which the light-transmitting substrate 4, the hole collecting electrode 2, the hole transport layer 5, the active layer 1, the electron transport layer 6, and the electron collecting electrode 3 are formed in this order. Each component will be described in detail below.

[0019] The light-transmitting substrate 4 is not particularly limited as long as it is a substrate that transmits light. Examples of the light-transmitting substrate 4 that can be used include transparent glass substrates such as quartz, soda-lime glass, and alkali-free glass, ceramic substrates, and light-transmitting plastic substrates. Examples of the light-transmitting plastic substrate that can be used include substrates made of polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, fluororesin films, polyolefins such as vinyl chloride and polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, and epoxy resins. As an example, in this embodiment, a transparent glass substrate is used as the light-transmitting substrate 4.

[0020] The active layer 1 is not particularly limited as long as it contains a substance capable of performing photoelectric conversion. The active layer 1 generally contains an electron acceptor and an electron donor.

[0021] When light is irradiated onto the active layer 1, the light is absorbed by the active layer 1, and electron transfer occurs at the interface between the electron acceptor and the electron donor, generating electrons and holes. The generated electrons and holes are extracted from the electron collecting electrode 3 and the hole collecting electrode 2, respectively.

[0022] The material of the active layer 1 may be either an inorganic compound or an organic compound, but it is preferable to use an organic compound.

[0023] Examples of electron donors that can be used in the active layer 1 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.

[0024] Specific examples of the electron donor that can be used 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, various low band gap polymers, and organometallic polymers.

[0025] Examples of the electron acceptor for the active layer 1 include fullerene or a fullerene derivative; a condensed ring tetracarboxylic acid diimide such as naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid diimide; and a condensed polycyclic aromatic hydrocarbon such as a perylene derivative, a thiazole derivative, a benzothiazole derivative, or a benzothiadiazole derivative.

[0026] Specific examples of the electron acceptor include polyphenylene vinylene, polyfluorene, derivatives thereof, copolymers thereof, carbon nanotubes (CNT), and phenyl C ６１ -fullerene derivatives such as methyl butyric acid ester (PCBM), polymers containing cyano (CN) groups or trifluoromethyl (CF3) groups, CF ３ 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).

[0027] As the fullerene derivative, hydrogenated fullerene, oxidized fullerene, hydroxylated fullerene, aminated fullerene, sulfided fullerene, halogenated (F, Cl, Br, I) fullerene, fulleroid, methanofullerene, pyrrolidinofullerene, alkylated fullerene, arylated fullerene, or the like can be used.

[0028] Unless otherwise specified, the term "fullerene" used herein refers to, for example, fullerene C ６０ , fullerene C ７０ , fullerene C ７６ , fullerene C ７８ , fullerene C ８２ , fullerene C ８４ , fullerene C ９０ , fullerene C ９４ , fullerene C ９６ etc. can be used.

[0029] Furthermore, a compound having a perovskite structure (perovskite compound) can be used for the active layer 1. Examples of perovskite compounds include CH ３ NH ３ PbI ３ - ｘ Cl ｘ (wherein x is 1 to 3), CH ３ NH ３ PbBr ３ , C.H. ３ NH３ PbBrI ２ , C.H. ３ NH ３ PbBr ２ I, CH ３ NH ３ SnBr ３ , C.H. ３ NH ３ SnI ３ , CH(=NH)NH ３ PbI ３ , (C ２ H ５ NH ３ ) ２ PbI ４ , (CH ２ = CHNH ３ ) ２ PbI ４ , (CH≡CNH ３ ) ２ PbI ４ , (C ６ H ５ NH ３ ) ２ PbI ４ , (C ６ H ３ F ２ NH ３ ) ２ PbI ４ , (C ６ F ５ NH ３ ) ２ PbI ４ , (C ４ H ３ SNH ３ ) ２ PbI ４ Among these compounds, CH ３ NH ３ PbI ３ Compound or CH ３ NH ３ PbI ３ - ｘ Cl ｘ It is preferable to use a compound (wherein x is 1 to 3) for the active layer 1. For example, in this embodiment, the active layer 1 is made of a compound ３ NH ３ PbI ３ Compound (i.e., MAPbI ３Compounds) are used.

[0030] The hole-collecting electrode 2 is a translucent electrode that is translucent at least to visible light contained in sunlight. The hole-collecting electrode 2 may be made of any material as long as it is translucent, and may be made of, for example, an oxide-based material such as indium tin oxide (ITO), tin oxide, zinc oxide, or titanium oxide. As an example, in this embodiment, an indium tin oxide electrode (ITO electrode) is used as the hole-collecting electrode 2.

[0031] For example, a conductive polymer such as poly(3,4-ethylenedioxythiophene)poly(styrenesulfonic acid) (PEDOT:PSS) or poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) can be used as the hole transport layer 5. In this embodiment, as an example, PEDOT:PSS is used as the hole transport layer 5.

[0032] 2 and 3, the electron collecting electrode 3 contains carbon nanotubes 31, an electron donating material 32, and an electron transporting material 33. In Fig. 3, for clarity of illustration, the electron transporting material 33 is shown scattered around the carbon nanotubes 31, but the electron transporting material 33 is actually filled throughout the entire electron collecting electrode 3 (i.e., arranged without any gaps).

[0033] As the carbon nanotubes 31, for example, single-walled carbon nanotubes (SWCNTs) can be used. The electron donating material 32 is added to facilitate the flow of electrons in the carbon nanotubes 31. That is, the electron donating material 32 is added to impart conductivity to the carbon nanotubes 31. By adding the electron donating material 32 to the carbon nanotubes 31, the main carriers can be changed from holes to electrons. For this reason, in this embodiment, the Seebeck coefficient of the electron collecting electrode 3 is negative.

[0034] In the first place, CNTs have holes injected into them due to the effect of oxidation by oxygen in the atmosphere, and exhibit the property of transporting holes. However, by doping with the electron-donating material 32, the electron-donating material 32 removes oxygen, weakening the hole-transporting property, and it is expected that electrons will be injected into the CNTs, giving them the property of transporting electrons.

[0035] The electron donating material 32 can be at least one of a substance that can partially donate electrons to other materials due to the properties of a lone pair of electrons or an anionic moiety, and a substance that can donate electrons to other materials due to an alkali metal or alkaline earth metal.

[0036] The material that donates electrons from an alkali metal or alkaline earth metal refers to elemental metals such as lithium, sodium, potassium, and cesium, as well as salts of the above metals that can be expected to generate elemental metals through decomposition during the vacuum deposition process. Examples of the salts of the above metals that can be expected to generate elemental metals through decomposition during the vacuum deposition process include LiF, CsCO ３ The materials that donate electrons by alkali metals or alkaline earth metals also include fullerenes containing alkali metals. Examples of fullerenes containing alkali metals include Li@C ６０ , Li@C ７０ , Na@C ６０ etc.

[0037] Specifically, as the electron donating material 32, at least one compound selected from the group consisting of compounds represented by the following chemical formulas 1 to 8 can be used.

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[0046] As an example, in this embodiment, triphenylphosphine (TPP) is used as the electron donating material 32 .

[0047] The electron transport material 33 is added to increase the contact points between the electron transport layer 6, which is the underlying layer, and the carbon nanotubes 31, and to more efficiently transport electrons from the electron transport layer 6 to the carbon nanotubes 31. The electron transport material 33 is also expected to penetrate into the gaps in the network structure of the CNTs and protect the CNTs, which have been given the electron transporting property by the electron donor material 32, from oxidation by oxygen in the atmosphere.

[0048] The electron transport material 33 has an electron mobility of 1×10 －８ cm ２ At least one of a substance having a valence of 1 / Vs or more and an n-type organic semiconductor containing fullerene or a fullerene derivative can be used.

[0049] Specifically, the electron transport material 33 may be CdS, GaN, In, ２ S ３ , InGaZnO ４ , SnO ２ , SnS ２ , SrSnO ３ , SrTiO ３ , TiO ２ , Zn ２ SO ４ , ZnO, ZnTiO ３ , ZrSnO ４ , C ６０ Fullerene, C ７０ Fullerene, diphenylmethanofullerene (DPM), oligoether (OE), C ６０ derivative, C ７０ At least one compound selected from the group consisting of derivatives and compounds represented by the following chemical formulas 9 to 30 can be used.

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[0072] However, in Chemical Formula 30, R ２ is a group represented by the following chemical formula 31.

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[0074] As an example, in this embodiment, the electron transport material 33 is (6,6)-phenyl C ６１ Butyric acid methyl ester (PC６１ BM) is adopted.

[0075] The electron transport layer 6 may be made of a compound similar to the electron transport material 33 contained in the electron collecting electrode 3. For example, the electron transport layer 6 may be made of a material such as PC ６１ For example, in this embodiment, the electron transport layer 6 may be made of PCBM or mix-PCBM (for example, nanom (registered trademark) spectrum E124 manufactured by Frontier Carbon Corporation). ６１ BM is used.

[0076] Examples Next, examples according to the present disclosure will be described. These examples are examples of the present disclosure, and the present disclosure is not limited to these examples.

[0077] (1) Preparation of Evaluation Samples In this example, samples of inverted perovskite solar cells were prepared using the following materials and procedures.

[0078] (1-1) Materials The following materials were prepared as the electrodes and layers of each sample.

[0079] (Sample A) Light-transmitting substrate 4 and hole-collecting electrode 2: transparent conductive film (ITO film) glass substrate; Hole-transporting layer 5: PEDOT:PSS; Active layer 1: MAPbI ３ (Perovskite) Electron transport layer 6: PC ６１ BM Electron collecting electrode 3: carbon nanotubes Electron donating material 32 contained in electron collecting electrode 3: TPP Electron transporting material 33 contained in electron collecting electrode 3: PC ６１ BM (Sample B) Sample B was the same as Sample A except that 1,2-bis(diphenylphosphino)ethane (DPPE) was used as the electron donating material 32 contained in the electron collecting electrode 3 .

[0080] (Sample C) Sample C was the same as Sample A, except that 1,1′-bis(diphenylphosphino)ferrocene (DPPF) was used as the electron donating material 32 contained in the electron collecting electrode 3 .

[0081] (Sample D) Sample D was the same as sample A, except that the electron donating material 32 was not added to the carbon nanotubes of the electron collecting electrode 3 .

[0082] (1-2) Preparation procedure (Sample A) A transparent conductive film (ITO film) is placed on a glass substrate with the ITO film facing up. ３ The treatment was carried out for 30 minutes. Subsequently, a PEDOT:PSS film (i.e., hole transport layer 5) was formed on the ITO film of the substrate. Specifically, the prepared PEDOT:PSS coating solution was spin-coated at 3000 rpm for 20 seconds, and heated on a hot plate at 115°C for 10 minutes to form a PEDOT:PSS film.

[0083] Next, a perovskite layer (i.e., active layer 1) was formed on the PEDOT:PSS film. ２ A perovskite precursor solution was prepared by mixing 355 mg of HCl, 122 mg of MAI, 490 μL of N,N'-dimethyl sulfoxide (DMSO), and 55 μL of dimethylformamide (DMF). The prepared perovskite precursor solution was then spin-coated at 4000 rpm for 20 seconds, and 150 μL of chlorobenzene (CB) was added dropwise 7 seconds after the start of spinning. After spinning, the mixture was heated at 100°C for 10 minutes to form a perovskite layer.

[0084] Next, a CNT transparent electrode (i.e., electron collecting electrode 3) was formed on the perovskite layer. Specifically, the CNT transparent electrode ( / collection filter) was transferred onto the perovskite layer, and only the collection filter was removed.

[0085] Next, the CNT transparent electrode was impregnated with the electron donating material 32. Specifically, 20 wt % TPP / CB was dropped onto the CNT transparent electrode, and then the electrode was rotated at 2000 rpm for 30 seconds using a spin coater to remove excess material.

[0086] Next, the CNT transparent electrode was impregnated with an electron transport material 33. Specifically, first, PC ６１30 mg of BM was dissolved in 1 mL of CB to prepare an electron transport material solution. The prepared electron transport material solution was then dropped onto the CNT transparent electrode impregnated with the electron donor material 32, and the electrode was then rotated at 4000 rpm for 20 seconds using a spin coater to remove excess material.

[0087] (Sample B) Sample B was the same as Sample A, except that 10 wt % / CB DPPE was dropped onto the CNT transparent electrode when the electron donating material 32 was impregnated into the CNT transparent electrode.

[0088] (Sample C) Sample C was the same as Sample A, except that 10 wt % / CB DPPF was dropped onto the CNT transparent electrode when the electron donating material 32 was impregnated into the CNT transparent electrode.

[0089] (Sample D) Sample D was the same as Sample A, except that the step of impregnating the CNT transparent electrode with the electron donating material 32 was not performed.

[0090] (2) Evaluation (2-2) Seebeck Coefficient For Samples A to D prepared above, the relationship between the temperature difference between both ends of the CNT transparent electrode and the thermoelectromotive force was measured. The results are shown in Figure 4. In Figure 4, when the slope of the graph is positive, the Seebeck coefficient is positive, and when the slope of the graph is negative, the Seebeck coefficient is negative.

[0091] 4, sample D, in which the CNT transparent electrode was not doped with the electron-donating material 32, had a positive Seebeck coefficient, whereas samples A to C, in which the CNT transparent electrode was doped with the electron-donating material 32, had negative Seebeck coefficients. This shows that doping the CNT transparent electrode with the electron-donating material 32 changes the film quality of the CNT transparent electrode from p-type to n-type.

[0092] (2-2) Conversion Efficiency The relationship between current and voltage (current-voltage characteristics) under light irradiation was measured for the samples A to D prepared above. The results are shown in FIG.

[0093] 5, the conversion efficiency (PCE) of sample D, in which the CNT transparent electrode was not doped with the electron-donating material 32, was 3.4%, whereas the conversion efficiency of samples A to C, in which the CNT transparent electrode was doped with the electron-donating material 32, was significantly increased to 5.4% or more. Specifically, the conversion efficiency of sample A was 5.9%, the conversion efficiency of sample B was 6.0%, and the conversion efficiency of sample C was 5.4%.

[0094] In the embodiment described above, the carbon nanotubes 31 of the electron collecting electrode 3 are doped with the electron donating material 32. This allows the main carriers of the electron collecting electrode 3 to be changed from holes to electrons. Therefore, even if a carbon nanotube film is used as the electron collecting electrode 3, it is possible to collect electrons generated in the active layer 1. Therefore, since a carbon nanotube film can be used as the electron collecting electrode 3, there is no need to use rare metals. As a result, it is possible to achieve high energy conversion efficiency while reducing material costs.

[0095] As a comparative example, Fig. 6 shows the layered structure of the electron collecting electrode 3, electron transport layer 6, and active layer 1 in a solar cell 10 that uses a metal electrode as the electron collecting electrode 3. As shown in Fig. 6, in the solar cell 10 of the comparative example, the electron collecting electrode 3 is made of metal and has a high density, so that a sufficient interface can be formed between the electron collecting electrode 3 and the electron transport layer 6. This makes it possible to easily receive electrons generated in the active layer 1.

[0096] On the other hand, when a carbon nanotube film is used as the electron collecting electrode 3, the low density makes it impossible to form a sufficient interface between the electron collecting electrode 3 and the electron transport layer 6, making it difficult to receive electrons generated in the active layer 1. In other words, the small number of contact points between the electron collecting electrode 3 (i.e., the carbon nanotubes 31) and the electron transport layer 6 makes it difficult for electrons to flow from the electron transport layer 6 to the carbon nanotubes 31.

[0097] In contrast, in the solar cell 10 of this embodiment, the carbon nanotubes 31 of the electron collecting electrode 3 are doped with an electron transport material 33. As a result, as shown in Fig. 2, the electron transport material 33 can increase the number of contact points between the electron collecting electrode 3 and the electron transport layer 6, allowing electrons to flow efficiently from the electron transport layer 6 to the carbon nanotubes 31.

[0098] The present disclosure is not limited to the above-described embodiments, and various modifications can be made as follows within the scope of the present disclosure.

[0099] (1) In the above embodiment, an example was described in which an indium tin oxide electrode (ITO electrode) was used as the hole-collecting electrode 2, but the present invention is not limited to this. For example, a carbon nanotube film may be used as the hole-collecting electrode 2.

[0100] (2) In the above embodiment, a solar cell 10 is used as a solar cell element having an inverted structure in which a light-transmitting substrate 4, a hole collecting electrode 2, a hole transport layer 5, an active layer 1, an electron transport layer 6, and an electron collecting electrode 3 are formed in this order, but this is not limited to this. For example, the electron side and the hole side may be reversed with respect to the layered structure of the solar cell 10 in the above embodiment. That is, as shown in FIG. 7 , a solar cell 10 may be used as a solar cell element in which a light-transmitting substrate 4, an electron collecting electrode 3, an electron transport layer 6, an active layer 1, a hole transport layer 5, and a hole collecting electrode 2 are formed in this order.

[0101] The technical features of the solar cell disclosed in this specification are as follows: (Item 1) A solar cell comprising a pair of electrodes (2, 3) and an active layer (1) located between the pair of electrodes and absorbing light to generate electrons and holes, wherein the pair of electrodes comprises an electron collecting electrode (3) that collects the electrons and a hole collecting electrode (2) that collects the holes, and the electron collecting electrode contains carbon nanotubes (31) and an electron donating material (32). (Item 2) The solar cell according to item 1, wherein the electron collecting electrode has a negative Seebeck coefficient. (Item 3) The solar cell according to item 1 or 2, wherein the electron collecting electrode contains an electron transport material (33). (Item 4) The solar cell according to any one of items 1 to 3, wherein the electron donating material is at least one of a substance capable of partially donating electrons to another material due to the properties of a lone pair of electrons or an anionic moiety, and a substance capable of donating electrons to another material due to an alkali metal or alkaline earth metal. (Item 5) The solar cell according to any one of Items 1 to 3, wherein the electron donating material is at least one compound selected from the group consisting of compounds represented by the above-mentioned chemical formulas 1 to 8. (Item 6) The electron transporting material has an electron mobility of 1×10 －８ cm ２ Item 7: The solar cell according to item 3, wherein the electron transport material is at least one of a substance having a valence of 0.1 V / Vs or more and an n-type organic semiconductor containing a fullerene or a fullerene derivative. ２ S ３ , InGaZnO ４ , SnO ２ , SnS ２ , SrSnO ３ , SrTiO ３ , TiO ２ , Zn ２ SO ４ , ZnO, ZnTiO ３ , ZrSnO ４ , C ６０ Fullerene, C ７０ Fullerene, diphenylmethanofullerene (DPM), oligoether (OE), C ６０ derivative, C ７０The solar cell according to item 3, wherein the active layer is at least one compound selected from the group consisting of a perovskite compound, a derivative thereof, and the compounds represented by the above-mentioned chemical formulas 9 to 30. (Item 8) The solar cell according to any one of items 1 to 7, wherein the active layer is composed of a perovskite compound.

[0102] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A solar cell comprising a pair of electrodes (2, 3) and an active layer (1) located between the pair of electrodes that absorbs light and generates electrons and holes, wherein the pair of electrodes is composed of an electron collecting electrode (3) that collects the electrons and a hole collecting electrode (2) that collects the holes, and the electron collecting electrode contains carbon nanotubes (31) and an electron donating material (32).

2. The solar cell according to claim 1, wherein the electron collecting electrode has a negative Seebeck coefficient.

3. The solar cell according to claim 1 or 2, wherein the electron collecting electrode contains an electron transport material (33).

4. The solar cell according to claim 1 or 2, wherein the electron donating material is at least one of a substance capable of partially donating electrons to other materials due to the properties of a lone pair of electrons or an anionic moiety, and a substance capable of donating electrons to other materials due to an alkali metal or alkaline earth metal.

5. The solar cell according to claim 1 or 2, wherein the electron donating material is at least one compound selected from the group consisting of compounds represented by the following chemical formulas 1 to 8:

6. The electron transport material has an electron mobility of 1×10 －８ cm ２ 4. The solar cell according to claim 3, wherein the n-type organic semiconductor is at least one of a substance having a conductivity of 1 / Vs or more and an n-type organic semiconductor containing a fullerene or a fullerene derivative.

7. The electron transport material is CdS, GaN, In ２ S ３ , InGaZnO ４ , SnO ２ , SnS ２ , SrSnO ３ , SrTiO ３ , TiO ２ , Zn ２ SO ４ , ZnO, ZnTiO ３ , ZrSnO ４ , C ６０ Fullerene, C ７０ Fullerene, diphenylmethanofullerene (DPM), oligoether (OE), C ６０ derivative, C ７０ 4. The solar cell according to claim 3, wherein the compound is at least one compound selected from the group consisting of derivatives and compounds represented by the following chemical formulas 9 to 30: However, in the above-mentioned chemical formula 30, R ２ is a group represented by the following chemical formula 31.

8. The solar cell according to claim 1 or 2, wherein the active layer is made of a perovskite compound.

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