Perovskite solar cell

Abstract

A perovskite solar cell (10) has an anode electrode (62) which is disposed adjacent to a hole transport layer (5), and in which at least two electrode layers are stacked. The two electrode layers are each composed of a water-repellent electrode layer (62a) that is positioned on the hole transport layer (5) side and contains water-repellent carbon, and an aqueous electrode layer (62b) that is positioned on the opposite side of the hole transport layer (5) across the water-repellent electrode layer (62a) and contains aqueous carbon.

Description

Perovskite solar cells

[0001] The present disclosure relates to perovskite solar cells.

[0002] Solar cells generally use elements such as silicon, compound semiconductors, and organic semiconductors. Recently, perovskite solar cells have been attracting attention due to their high light-harvesting capacity, thin film construction, and low cost.

[0003] Patent Document 1 discloses a perovskite solar cell (solar cell in Patent Document 1) having a photoelectrode (cathode in Patent Document 1), a power generation layer (photoelectric conversion layer in Patent Document 1), and a counter electrode (anode in Patent Document 1) in this order. In this perovskite solar cell, the power generation layer has a structure represented by the general formula R-M-X ３ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). Furthermore, this perovskite solar cell has, between the counter electrode and the power generation layer, a diffusion prevention layer made of at least one material selected from the group consisting of a metal oxide, a metal nitride, and a metal oxynitride containing a metal from Groups 6 to 15 of the periodic table, and carbon.

[0004] International Publication No. 2018 / 056295

[0005] The perovskite solar cell disclosed in Patent Document 1 has a diffusion prevention layer between the counter electrode and the power generation layer to prevent the metal material of the counter electrode from diffusing into the photoelectric conversion layer containing an organic-inorganic perovskite compound. This allows the perovskite solar cell to maintain a high photoelectric conversion efficiency even when a voltage is applied to the perovskite solar cell over a long period of time. However, as shown in Comparative Examples 3 and 4 of Patent Document 1, when a diffusion prevention layer made of carbon is used as the counter electrode, the photoelectric conversion efficiency decreases.

[0006] This phenomenon is observed, for example, when an aqueous carbonaceous liquid is applied as a counter electrode. When the counter electrode is formed by applying an aqueous carbonaceous liquid to a hole transport layer and drying it, the carbonaceous liquid penetrates into the hole transport layer before drying and into the perovskite layer, which is the underlying layer of the hole transport layer. Because the perovskite layer is sensitive to moisture, the penetration of the carbonaceous liquid may reduce the photoelectric conversion efficiency.

[0007] Therefore, there is a demand for a perovskite solar cell that has a counter electrode containing carbon and that suppresses the decline in photoelectric conversion efficiency.

[0008] One embodiment of a perovskite solar cell according to the present disclosure is a perovskite solar cell having an anode electrode disposed adjacent to a hole transport layer and including at least two stacked electrode layers, the two electrode layers comprising a water-repellent electrode layer containing water-repellent carbon located on the hole transport layer side, and an aqueous electrode layer containing aqueous carbon located on the opposite side of the water-repellent electrode layer from the hole transport layer.

[0009] A solution containing water-repellent carbon that becomes a water-repellent electrode layer upon drying has a large contact angle and low wettability. Therefore, when the solution containing water-repellent carbon is applied to a hole transport layer and dried to form the water-repellent electrode layer, the solvent of the solution is unlikely to penetrate into the hole transport layer or the perovskite layer. As a result, even when a water-repellent electrode layer is formed, a decrease in the photoelectric conversion efficiency of the perovskite solar cell is suppressed.

[0010] On the other hand, a water-repellent electrode layer containing water-repellent carbon has a high resistance value. Therefore, in this embodiment, an aqueous electrode layer containing water-repellent carbon is formed on the opposite side of the water-repellent electrode layer from the hole transport layer, and the water-repellent electrode layer and the aqueous electrode layer constitute an anode electrode. Although the aqueous electrode layer has a lower resistance value than the water-repellent electrode layer, a solution containing water-repellent carbon has a smaller contact angle and higher wettability than a solution containing water-repellent carbon. However, since the solution containing water-repellent carbon is applied onto the water-repellent electrode layer, the water-repellent electrode layer prevents the solution from penetrating into the hole transport layer. Thus, by constructing the anode electrode from a water-repellent electrode layer and an aqueous electrode layer, a perovskite solar cell can be obtained that has an anode electrode with a low resistance value and suppresses a decrease in photoelectric conversion efficiency.

[0011] 1 is a schematic cross-sectional view of a perovskite solar cell; 2 is a perspective view from above of a perovskite solar cell; 3 is a cross-sectional view illustrating the power generation principle of a perovskite solar cell; and 4 is an explanatory diagram illustrating the manufacturing procedure of a perovskite solar cell.

[0012] Hereinafter, embodiments of the perovskite solar cell according to the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are examples for explaining the perovskite solar cell, and the perovskite solar cell is not limited to these embodiments. Therefore, the perovskite solar cell according to the present disclosure can be implemented in various forms without departing from the spirit of the present disclosure.

[0013] [Basic Structure of Solar Cell] As shown in Figures 1 and 2, a perovskite solar cell 10 according to this embodiment (hereinafter simply referred to as solar cell 10) includes a substrate 2 and a laminate 11 provided on the substrate 2. The substrate 2 includes a transparent substrate 21 and a transparent conductive film 22. The laminate 11 includes a blocking layer 3, a power generation layer 4, and a hole transport layer 5. The blocking layer 3 is provided on the transparent conductive film 22 and transfers electrons to the transparent conductive film 22, while separating the hole transport layer 5 from the transparent conductive film 22 to prevent recombination of electrons and holes (reverse electron transfer). The power generation layer 4 is provided on the blocking layer 3 and is formed by laminating a perovskite layer 44, which is excited by light to generate electrons, on a porous semiconductor 41. The hole transport layer 5 is provided on the power generation layer 4 and allows holes generated in the perovskite layer 44 to pass through. Furthermore, a photoelectrode 61 that emits electrons via the transparent conductive film 22 is provided on the surface of the blocking layer 3, and a counter electrode 62 (an example of an anode electrode) that receives electrons is provided on the surface of the hole transport layer 5. The counter electrode 62 is formed from the surface of the hole transport layer 5, passing over the side surfaces of the hole transport layer 5 and the perovskite layer 44, and extending to the surface of the blocking layer 3. Hereinafter, the photoelectrode 61 and the counter electrode 62 will be collectively referred to as electrode 6. The arrangement of the electrode 6 is not particularly limited as long as it allows electron transfer; for example, the photoelectrode 61 may be formed by connecting a conductor to the transparent conductive film 22. Furthermore, to increase the durability of the solar cell 10, the counter electrode 62 may be protected by a transparent substrate 21 or the like.

[0014] The transparent substrate 21 is made of a light-transmitting material. Examples of the transparent substrate 21 include a transparent glass substrate, a frosted semi-transparent glass substrate, and a transparent resin substrate. Examples of the transparent conductive film 22 include fluorine-doped tin oxide (FTO), tin oxide (TO), tin-doped indium oxide (ITO), zinc oxide (ZnO), and aluminum-doped zinc oxide (AZO).

[0015] Metal oxides are suitable for the blocking layer 3 and the porous semiconductor 41, and titanium dioxide (TiO ２ ), zinc oxide (ZnO), niobium oxide (Nb ２ O５ ), tin dioxide (SnO ２ ) and aluminum oxide (Al ２ O ３ In particular, titanium dioxide (TiO ) is used, which can secure a large surface area for laminating the perovskite layer 44. ２ ) sintered body. Furthermore, a portion of the blocking layer 3 extends into a recess 221 formed by removing a portion of the transparent conductive film 22 to form an insulating layer 31, thereby dividing the transparent conductive film 22 into two. In the blocking layer 3, electrons can move in the stacking direction but have difficulty moving laterally, perpendicular to the stacking direction. Furthermore, electrons cannot move between the two transparent conductive films 22 separated by the insulating layer 31. In other words, electrons that enter the blocking layer 3 move smoothly in the stacking direction of the transparent conductive film 22 and are supplied to the photoelectrode 61, but the insulating layer 31 prevents them from moving laterally toward the counter electrode 62, so that the photoelectrode 61 and the counter electrode 62 are not short-circuited.

[0016] The perovskite layer 44 is an organic-inorganic hybrid compound. Specifically, the perovskite layer 44 is a compound composed of lead and a halogen element X (PbX ２ , X = halogen element) and methylammonium iodide (CH ３ NH ３ Specifically, a solution containing lead and a halogen element X (for example, PbI) is formed in the pores of the porous semiconductor 41. ２ The perovskite compound (CH when X=I) that forms the perovskite layer 44 is formed by permeating the perovskite layer 44 with a solution of MAI (N,N-dimethylformamide solution of CH when X=I) and drying the perovskite layer 44. ３ NH ３ PbI ３ The halogen element X can be iodine, bromine, chlorine, or the like, and it is particularly preferable to use iodine, which has high morphological stability. The halogen element X can also be a mixture of MABr and 0.2M lead bromide (PbBr ２ ), FAI and lead iodide (PbI ２) using mixed cation-mixed halide ((FAPbI ３ ) １－ｘ (MAPbBr ３ ) ｘ In this case, for example, (FAPbI ３ ) ０．８５ (MAPbBr ３ ) ０．１５ etc. can be suitably used.

[0017] A hole transport material described later is used for the hole transport layer 5. For the photoelectrode 61, for example, an elemental metal or alloy of a metal such as gold, platinum, silver, or copper, or an oxide conductor such as fluorine-doped tin oxide (FTO) or tin-doped indium oxide (ITO) is used.

[0018] The counter electrode 62 is a carbon electrode made of carbon nanotubes (hereinafter, sometimes abbreviated as CNT). CNTs are highly conductive and have a fibrous continuum. Because they are continuum, they have low interparticle resistance, which allows the resistance of the electrode itself to be reduced. The counter electrode 62 according to this embodiment is constructed by stacking two types of carbon electrodes. Specifically, as shown in FIG. 3 , the counter electrode 62 includes a first CNT film 62a (an example of an electrode layer and a water-repellent electrode layer) containing water-repellent carbon and located on the hole transport layer 5 side, and a second CNT film 62b (an example of an electrode layer and a water-repellent electrode layer) containing aqueous carbon and located on the opposite side of the hole transport layer 5 across the first CNT film 62a.

[0019] Here, the principle of how the solar cell 10 generates electricity will be described with reference to Figure 3. When light such as sunlight or room light is incident from the transparent substrate 21 side, this incident light is transmitted through the substrate 2 and blocking layer 3 without being absorbed much, and most of it reaches the power generation layer 4. When the incident light that has reached the power generation layer 4 is irradiated onto the perovskite layer 44, this perovskite layer 44 absorbs the light energy and becomes excited. When this excitation raises the energy level of the perovskite layer 44 to a predetermined level higher than the conduction band potential of the metal oxide that is the porous semiconductor 41, electrons are injected from the perovskite layer 44 into the porous semiconductor 41. The injected electrons pass through the blocking layer 3 and are collected by the photoelectrode 61.

[0020] On the other hand, holes generated in the perovskite layer 44 reach the counter electrode 62 via the hole transport layer 5, where they recombine with electrons that have passed through the external load 7. In other words, a potential gradient is generated between the photoelectrode 61 and the counter electrode 62, and power can be supplied by connecting the external load 7 between the two electrodes.

[0021] [Procedure for Manufacturing Solar Cell] <Example> Next, an example of the solar cell 10 according to this embodiment will be described. First, the procedure for manufacturing the solar cell 10 will be described with reference to FIG. 4. The solar cell 10 can be manufactured with reference to known techniques such as Michael Saliba et al., "Correction to 'How to Make over 20% Efficient Perovskite Solar Cells in Regular (nip) and Inverted (pin) Architectures'", Chem. Mater., 2018, 30, 4193-4218.

[0022] First, the substrate 2 is fabricated by forming a transparent conductive film 22 on a transparent substrate 21. The transparent conductive film 22 is laminated on the transparent substrate 21 by, for example, CVD (chemical vapor deposition) or sputtering. Next, the transparent conductive film 22 is partially removed by laser scribing to form recesses 221 for the insulating layer 31, and then the substrate is cleaned. Next, a blocking layer 3 is formed on the entire surface of the substrate 2 by ALD (atomic layer deposition) or SPD (spray pyrolysis). The blocking layer 3 is preferably made of TiO ２ Next, a porous semiconductor 41, which is a nanoparticle sintered layer, is formed near the center on the masked substrate 2 and blocking layer 3. The porous semiconductor 41 is preferably TiO ２ Porous layer (p-TiO ２ This porous semiconductor 41 is formed by diluting the nanoparticle paste with a solvent, applying it by spin coating at a rotation speed of 4000 rpm to 6000 rpm, drying it, and then removing the masking and heating it at 450°C to 550°C to sinter it.

[0023] Next, for example, PbI２ An N,N-dimethylformamide solution of the above is prepared and dropped onto the porous semiconductor 41, and then the pores (p-TiO ２ ) Permeate the inside and remove excess solution. Dry at 60 to 120°C (preferably 70 to 90°C) to remove PbI ２ Form a layer.

[0024] MAI (CH ３ NH ３ The substrate 2, the blocking layer 3, and the porous semiconductor 41 permeated with lead iodide are immersed in an isopropyl alcohol solution (2 mg / ml to 20 mg / ml) of PbI at 0°C to 80°C (preferably at room temperature) (MAI immersion method). ２ and MAI react to form a perovskite compound [(CH ３ NH ３ ) PbI ３ (MAPbI ３ After forming the perovskite layer 44 inside and on top of the pores of the porous semiconductor 41, the layer is irrigated with a pure isopropyl alcohol solution and dried at 60°C to 120°C (preferably 70°C to 100°C). ３ ) １－ｘ (MAPbBr ３ ) ｘ )-based perovskite compounds can also be prepared in a similar manner.

[0025] The above-described manufacturing procedure involves controlling the crystal growth of the perovskite compound that forms the perovskite layer 44 in two steps, but this may also be performed in one step. For example, ３ NH ３ ) PbI ３ The solution is then permeated into the pores of the porous semiconductor 41 by spin coating. Next, toluene is added dropwise during spinning to precipitate microcrystals and make the surface mirror-finished (poor solvent precipitation method).

[0026] The hole transport material according to this example is prepared as a 60 mg / ml to 90 mg / ml chlorobenzene solution. The solution is dropped onto the perovskite layer 44, excess solution is removed by spin coating, and the solution is dried to form the hole transport layer 5. An additive such as TPFB may be added to the hole transport material. When TPFB is added, the TPFB content of the hole transport material is preferably 0.01 wt % to 100 wt %, and more preferably 0.1 wt % to 50 wt %. For example, the hole transport material according to this example is weighed out to a concentration of 30 mM, and TPFB equivalent to 10 wt % of that is added. The hole transport layer 5 can be formed by dissolving these in chlorobenzene. The thickness of the hole transport layer 5 in this example and Comparative Examples 1 to 4 described below is 200 nm, and the contact angle is 75 degrees.

[0027] More than PbI ２ The steps from layer formation to hole transport layer 5 formation are preferably carried out in a dry nitrogen atmosphere such as in a glove box. Finally, the electrode 6 is formed. The photoelectrode 61 is formed by adhering a thin film of gold or the like to the surface of the blocking layer 3 by vacuum deposition or the like.

[0028] As described above, the counter electrode 62 is a carbon electrode using CNTs. In this embodiment, the counter electrode 62 includes a first CNT film 62a containing water-repellent carbon and located on the hole transport layer 5 side, and a second CNT film 62b containing water-repellent carbon and located on the opposite side of the hole transport layer 5 with the first CNT film 62a in between. In other words, the counter electrode 62 is configured by laminating the first CNT film 62a and the second CNT film 62b.

[0029] The first CNT film 62a is formed by applying a solution (hereinafter also referred to as the first CNT solution 63a) in which first CNTs containing water-repellent carbon, a resin binder, and a stabilizer component (hereinafter referred to as the binder, etc.) are dispersed in a solvent onto the hole transport layer 5, and then evaporating the solvent. This dries the first CNT residue, resulting in the first CNT film 62a. Similarly, the second CNT film 62b is formed by applying a solution (hereinafter also referred to as the second CNT solution 63b) in which second CNTs containing aqueous carbon and a resin binder, etc. are dispersed in a solvent onto the first CNT film 62a, and then evaporating the solvent. This dries the second CNT residue, resulting in the second CNT film 62b. The manufacturing methods for the first CNT film 62a and the second CNT film 62b are described in detail below.

[0030] First, the first CNT solution 63a is applied to the surface of the hole transport layer 5 and dried. Specifically, the first CNT solution 63a is obtained by dispersing 0.05 wt % to 4.0 wt % of water-repellent first CNTs and 1.0 wt % to 4.0 wt % of a resin binder and stabilizer component (hereinafter referred to as the first binder, etc.) in 98.5 wt % to 92.0 wt % of a solvent. The first CNT preferably have a diameter of 5 nm to 20 nm and a length of 1 μm to 3 mm. The first binder, etc. is preferably an acrylic, fluorine-based, ethylene oxide-based, paraffin-based, wax-based, anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant, etc. The solvent is preferably an alcohol, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, or 1-pentanol.

[0031] The first CNT solution 63a prepared as described above is applied to the surface of the hole transport layer 5 to a thickness of, for example, 150 μm. The solvent is then evaporated to dry the first CNTs. The solvent is evaporated, for example, by heating at 80°C for 5 minutes. Once the solvent has evaporated, the remaining first CNTs become the first CNT film 62a. The thickness of the first CNT film 62a is 1 μm to 5 μm. The amount of the first CNT solution 63a applied to the surface of the hole transport layer 5 is not limited to 150 μm, and can be adjusted so that the thickness of the first CNT film 62a is 1 μm to 5 μm. In this embodiment, the thickness of the first CNT film 62a is 5 μm. The resistance of the water-repellent carbon is approximately 100 to 200 times that of the water-soluble carbon, which is significantly higher than the resistance of the water-soluble carbon. Therefore, it is desirable to make the thickness of the first CNT film 62a as thin as possible.

[0032] Next, the second CNT solution 63b is applied to the surface of the first CNT film 62a and dried. Specifically, the second CNT solution 63b is obtained by dispersing 1.0 wt % to 20.0 wt % of aqueous second CNT and 0.9 wt % to 17.0 wt % of a resin binder and dispersant component (hereinafter referred to as the second binder, etc.) in 98.1 wt % to 63.0 wt % of a solvent (water). The second CNT preferably have a diameter of 5 nm to 20 nm and a length of 1 μm to 3 mm. The second binder, etc., is preferably acrylic, polyvinyl alcohol, hydroxycellulose, or the like.

[0033] The second CNT solution 63b prepared as described above is applied to the surface of the first CNT film 62a to a thickness of, for example, 1200 μm. The solvent (water) is then evaporated to dry the second CNTs. The solvent is evaporated, for example, by heating at 100°C for 5 minutes. Once the solvent has evaporated, the second CNT residue becomes the second CNT film 62b. The thickness of the second CNT film 62b is 20 μm to 25 μm. The amount of the second CNT solution 63b applied to the surface of the first CNT film 62a is not limited to 1200 μm, and can be adjusted so that the thickness of the second CNT film 62b is 20 μm to 25 μm. In this embodiment, the thickness of the second CNT film 62b is 20 μm.

[0034] Comparative Example 1 The solar cell of Comparative Example 1 differs from solar cell 10 of the present example in that the counter electrode does not have a first CNT film, but is composed only of a second CNT film made of gold with a film thickness of 0.1 μm. The other configurations are the same as those of solar cell 10 of the present example.

[0035] <Comparative Example 2> The solar cell of Comparative Example 2 differs from solar cell 10 of this example in that the counter electrode does not have a first CNT film, but is composed only of a second CNT film made of aqueous carbon with a film thickness of 19 μm. The other configurations are the same as those of solar cell 10 of this example.

[0036] Comparative Example 3 The solar cell of Comparative Example 3 differs from solar cell 10 of the present example in that the counter electrode does not have a first CNT film, but is composed only of a second CNT film made of water-repellent carbon with a film thickness of 20 μm. The other configurations are the same as those of solar cell 10 of the present example.

[0037] Comparative Example 4 The solar cell of Comparative Example 4 differs from solar cell 10 of the present example in that the counter electrode is composed of a first CNT film made of non-water-repellent carbon with a film thickness of 5 μm and a second CNT film made of water-repellent carbon with a film thickness of 20 μm. The other configurations are the same as those of solar cell 10 of the present example.

[0038] For the solar cell 10 in Example and Comparative Examples 1 to 4 manufactured using the above-described manufacturing method, the contact angle of the first CNT film, the resistance of the counter electrode, and the photoelectric conversion efficiency of the solar cell were measured. The contact angle measurements for this Example and Comparative Examples 1 to 4 were performed in accordance with JIS R3257, "Test method for wettability of substrate glass surfaces." The contact angle was measured using a contact angle measuring instrument "CAM-004" manufactured by FLOWDESIGN. Resistance measurements were performed in accordance with JIS K7194, "Test method for resistivity of conductive plastics using the four-probe method." The counter electrode 62 used for resistance measurement had a rectangular shape measuring 26 mm x 30 mm. The photoelectric conversion efficiency of the solar cell 10 is expressed as a relative value (hereinafter also referred to as the relative value of photoelectric conversion efficiency) when the photoelectric conversion efficiency of Comparative Example 1 is set to 1. The measurement results are shown in Table 1 below.

[0039]

[0040] As can be seen from Table 1, in the solar cell 10 of this example, the contact angle of the first CNT film 62a was 103 degrees, the resistance of the counter electrode 62 was 10 Ω / sq, and the relative value of the photoelectric conversion efficiency was 0.96. Generally, a contact angle of 90 degrees or greater is considered to be water-repellent, so the first CNT film 62a of this example is water-repellent. The relative value of the photoelectric conversion efficiency of this example was 0.96, which is close to 1, indicating that the solvent of the first CNT solution 63a used in forming the first CNT film 62a hardly penetrated into the hole transport layer 5 and the perovskite layer 44, and that penetration was suppressed.

[0041] Generally, the resistance value of the counter electrode 62 in a solar cell is preferably 20 Ω / sq or less, and more preferably 10 Ω / sq or less. The resistance value of the solar cell 10 of this embodiment is 10 Ω / sq, which satisfies the desirable resistance value requirement. Furthermore, the counter electrode 62 of the solar cell 10 of this embodiment is made of carbon, which is more cost-effective than gold. Therefore, the solar cell 10 of this embodiment is practical in terms of resistance value, photoelectric conversion efficiency, and cost. To further reduce the resistance value, the thickness of the second CNT film 62b should be made thicker than 20 μm.

[0042] In the solar cell of Comparative Example 1, the resistance value of the counter electrode was 0.6 Ω / sq, and the relative value of the photoelectric conversion efficiency was 1. Comparative Example 1 is excellent in both the resistance value and the photoelectric conversion efficiency and is therefore practical, but is not practical from the viewpoint of cost because the counter electrode is made of gold, which is expensive.

[0043] In the solar cell of Comparative Example 2, the resistance value of the counter electrode was 8 Ω / sq, and the relative value of the photoelectric conversion efficiency was 0. In other words, the solar cell of Comparative Example 2 did not generate electricity. In the solar cell of Comparative Example 2, the first CNT film was not used, and aqueous carbon was used as the material for the second CNT film. Therefore, it is thought that the solvent of the second CNT solution used in forming the second CNT film penetrated into the hole transport layer 5 and the perovskite layer 44, preventing power generation. Therefore, the solar cell of Comparative Example 2 is practical from the perspective of resistance value, but not practical from the perspective of photoelectric conversion efficiency.

[0044] In the solar cell of Comparative Example 3, the resistance value of the counter electrode was 204 Ω / sq, and the relative value of the photoelectric conversion efficiency was 0.1. In the solar cell of Comparative Example 3, the first CNT film was not used, and water-repellent carbon was used as the material for the second CNT film. Therefore, although the solvent of the second CNT solution used in forming the second CNT film was prevented from penetrating into the hole transport layer 5 and the perovskite layer 44, the resistance value of the counter electrode increased, which is thought to have resulted in a decrease in the photoelectric conversion efficiency. Therefore, the solar cell of Comparative Example 3 is not practical in terms of either the resistance value or the photoelectric conversion efficiency.

[0045] In the solar cell of Comparative Example 4, the resistance value of the counter electrode was 10 Ω / sq, and the relative value of the photoelectric conversion efficiency was 0.03. In the solar cell of Comparative Example 3, non-water-repellent carbon was used as the material for the first CNT film, and aqueous carbon was used as the material for the second CNT film. Therefore, it is thought that the solvents of the first CNT solution and the second CNT solution used in forming the first CNT film and the second CNT film permeated into the hole transport layer 5 and the perovskite layer 44, resulting in a decrease in photoelectric conversion efficiency. Therefore, the solar cell of Comparative Example 4 is practical in terms of resistance value, but not practical in terms of photoelectric conversion efficiency.

[0046] [Outline of the above embodiment] Hereinafter, the perovskite solar cell (10) described in the above embodiment has the following configuration.

[0047] <1> One embodiment of the perovskite solar cell (10) is a perovskite solar cell (10) having an anode electrode (62) arranged adjacent to a hole transport layer (5) and including at least two stacked electrode layers, the two electrode layers being composed of a water-repellent electrode layer (62a) containing water-repellent carbon and located on the hole transport layer (5) side, and an aqueous electrode layer (62b) containing aqueous carbon and located on the opposite side of the water-repellent electrode layer (62a) from the hole transport layer (5).

[0048] The solution (63a) containing water-repellent carbon, which becomes the water-repellent electrode layer (62a) upon drying, has a large contact angle and low wettability. Therefore, when the solution (63a) containing water-repellent carbon is applied to the hole transport layer (5) and dried to form the water-repellent electrode layer (62a), the solvent of the solution (63a) is unlikely to penetrate into the hole transport layer (5) or the perovskite layer (44). As a result, even when the water-repellent electrode layer (62a) is formed, a decrease in the photoelectric conversion efficiency of the perovskite solar cell (10) is suppressed.

[0049] The water-repellent electrode layer (62a) containing water-repellent carbon has a high resistance value. Therefore, in the above embodiment, an aqueous electrode layer (62b) containing aqueous carbon is formed on the opposite side of the water-repellent electrode layer (62a) from the hole transport layer (5), and the water-repellent electrode layer (62a) and the aqueous electrode layer (62b) constitute the anode electrode (62). Although the aqueous electrode layer (62b) has a lower resistance value than the water-repellent electrode layer (62a), the solution (63b) containing aqueous carbon has a smaller contact angle and higher wettability than the solution (63a) containing water-repellent carbon. However, because the solution (63b) containing aqueous carbon is applied on the water-repellent electrode layer (62a), the water-repellent electrode layer (62a) prevents the solution from penetrating into the hole transport layer (5). In this way, by configuring the anode electrode (62) from the water-repellent electrode layer (62a) and the water-repellent electrode layer (62b), a perovskite solar cell (10) can be obtained which has an anode electrode (62) with a low resistance value and in which a decrease in photoelectric conversion efficiency is suppressed.

[0050] <2> In the perovskite solar cell (10) described in <1> above, it is preferable that the contact angle of the water-repellent electrode layer (62a) is 90 degrees or more.

[0051] Generally, a contact angle of 90 degrees or greater is considered to be water-repellent, and so the water-repellent electrode layer (62a) is water-repellent. Therefore, when a solution (63a) containing water-repellent carbon is applied and dried to form the water-repellent electrode layer (62a), the solution (63a) is unlikely to penetrate into the hole transport layer (5) or the perovskite layer (44). This makes it possible to obtain a perovskite solar cell (10) in which a decrease in photoelectric conversion efficiency is suppressed.

[0052] <3> In the perovskite solar cell (10) described in <1> or <2> above, it is preferable that the resistance value of the anode electrode (62) is 10 Ω / sq or less.

[0053] In general, it is desirable that the resistance value of the anode electrode (62) in a solar cell is 20 Ω / sq or less. Therefore, a perovskite solar cell (10) having an anode electrode (62) with a resistance value of 10 Ω / sq or less is practical from the viewpoint of resistance value.

[0054] <4> In the perovskite solar cell (10) according to any one of <1> to <3> above, it is preferable that the thickness of the aqueous electrode layer (62b) is greater than the thickness of the water-repellent electrode layer (62a).

[0055] The resistance value of the water-repellent electrode layer (62a) is higher than the resistance value of the aqueous electrode layer (62b). Furthermore, the anode electrode (62) of the perovskite solar cell (10) is required to have low resistance. Therefore, by making the thickness of the aqueous electrode layer (62b) thicker than the thickness of the water-repellent electrode layer (62a), and by manufacturing the perovskite solar cell (10) using the above-described simple process, it is possible to obtain a perovskite solar cell (10) having an anode electrode (62) with low resistance and in which a decrease in photoelectric conversion efficiency is suppressed.

[0056] The present disclosure is applicable to perovskite solar cells.

[0057] 5: hole transport layer, 10: perovskite solar cell, 62: counter electrode (anode electrode), 62a: first CNT film (electrode layer, water-repellent electrode layer), 62b: second CNT film (electrode layer, aqueous electrode layer)

Claims

1. A perovskite solar cell having an anode electrode in which at least two electrode layers are laminated adjacent to a hole transport layer, wherein the two electrode layers are composed of a water-repellent electrode layer containing water-repellent carbon located on the side of the hole transport layer and a water-based electrode layer containing water-based carbon located on the side opposite to the hole transport layer with the water-repellent electrode layer interposed therebetween.

2. The perovskite solar cell according to claim 1, wherein the contact angle of the water-repellent electrode layer is 90 degrees or more.

3. The perovskite solar cell according to claim 1, wherein the resistance value of the anode electrode is 10 Ω / sq or less.

4. The perovskite solar cell according to any one of claims 1 to 3, wherein the thickness of the water-based electrode layer is thicker than the thickness of the water-repellent electrode layer.

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