Perovskite solar cell

Abstract

To provide a perovskite solar cell which has a counter electrode containing carbon and in which deterioration of photoelectric conversion efficiency is suppressed.SOLUTION: 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 laminated. The two electrode layers are composed of: a water-repellent layer 62a that is positioned on the hole transport layer 5 side and contains water-repellent carbon; and an aqueous 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.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Solar cells generally use elements such as silicon-based, compound semiconductors, and organic semiconductors. Recently, perovskite solar cells that can achieve high light trapping ability, thin film formation, and cost reduction have attracted attention.

[0003] Patent Document 1 discloses a perovskite solar cell (a solar cell in Patent Document 1) having a photoanode (a cathode in Patent Document 1), a power generation layer (a photoelectric conversion layer in Patent Document 1), and a counter electrode (an anode in Patent Document 1) in this order. In the perovskite solar cell, the power generation layer contains an organic-inorganic perovskite compound represented by the general formula R-M-X3 (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). Further, this perovskite solar cell has a diffusion prevention layer composed of at least one selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides containing metals of Groups 6 to 15 of the periodic table, and carbon, between the counter electrode and the power generation layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The perovskite solar cell disclosed in Patent Document 1 prevents the metal material of the counter electrode from diffusing into the photoelectric conversion layer containing the organic-inorganic perovskite compound by providing a diffusion prevention layer between the counter electrode and the power generation layer. As a result, even when a voltage is applied to the perovskite solar cell for a long period of time, a high photoelectric conversion efficiency can be maintained. However, as shown in Comparative Example 3 and Comparative Example 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 is a phenomenon that can be observed, for example, when an aqueous carbon solution is applied as the counter electrode. When an aqueous carbon solution is applied to the hole transport layer and dried to form the counter electrode, the carbon solution penetrates into the hole transport layer before drying and further penetrates into the perovskite layer, which is the underlying layer of the hole transport layer. Since the perovskite layer is vulnerable to moisture, there is a risk that the photoelectric conversion efficiency will decrease when the carbon solution penetrates.

[0007] Therefore, there is a need for a perovskite solar cell having a counter electrode containing carbon and suppressing a decrease in photoelectric conversion efficiency.

Means for Solving the Problem

[0008] One embodiment of the perovskite solar cell according to the present disclosure is a perovskite solar cell having an anode electrode that is disposed adjacent to the hole transport layer and in which at least two electrode layers are laminated, and the two electrode layers include 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.

[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 a solution containing water-repellent carbon is applied to the hole transport layer and dried to form a water-repellent electrode layer, the solvent of the solution hardly penetrates into the hole transport layer and also hardly penetrates into 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, the water-repellent electrode layer containing water-repellent carbon has a high resistance value. Therefore, in this embodiment, an aqueous electrode layer containing aqueous carbon is formed on the side opposite to the hole transport layer with the water-repellent electrode layer interposed therebetween, and the anode electrode is constituted by the water-repellent electrode layer and the aqueous electrode layer. Although the aqueous electrode layer has a lower resistance value than the water-repellent electrode layer, the solution containing aqueous carbon has a smaller contact angle and higher wettability than the solution containing water-repellent carbon. However, since the solution containing aqueous carbon is applied on the water-repellent electrode layer, the penetration of the solution into the hole transport layer is suppressed by the water-repellent electrode layer. Thus, by configuring the anode electrode with the water-repellent electrode layer and the aqueous electrode layer, a perovskite solar cell having a low-resistance anode electrode and suppressing a decrease in photoelectric conversion efficiency can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the perovskite solar cell according to the present disclosure will be described in detail with reference to the drawings. It should be noted 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 gist thereof.

[0013] 〔Basic Structure of Solar Cell〕 As shown in FIGS. 1 and 2, the perovskite solar cell 10 (hereinafter simply referred to as the solar cell 10) according to the present embodiment includes a substrate 2 and a laminate 11 provided on the substrate 2. The substrate 2 has a transparent substrate 21 and a transparent conductive film 22. The laminate 11 includes a blocking layer 3, a light-emitting layer 4, and a hole transport layer 5. The blocking layer 3 is provided on the transparent conductive film 22, transfers electrons to the transparent conductive film 22, and separates the hole transport layer 5 from the transparent conductive film 22 to prevent recombination (reverse electron transfer) of electrons and holes. The light-emitting layer 4 is provided on the blocking layer 3, and is formed by laminating a perovskite layer 44 that is excited by light to generate electrons on a porous semiconductor 41. The hole transport layer 5 is provided on the light-emitting layer 4, and holes generated in the perovskite layer 44 pass therethrough. Further, a photoelectrode 61 that emits electrons through 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 via the side surfaces of the hole transport layer 5 and the perovskite layer 44 across the surface of the blocking layer 3. Hereinafter, when the photoelectrode 61 and the counter electrode 62 are collectively referred to, they are called the electrode 6. The arrangement of the electrode 6 is not particularly limited as long as electron transfer is possible, for example, by forming the photoelectrode 61 by wire connection to the transparent conductive film 22. Further, in order to improve the durability of the solar cell 10, the counter electrode 62 may be protected by the transparent substrate 21 or the like.

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

[0015] A metal oxide is suitable for the blocking layer 3 and the porous semiconductor 41, and titanium dioxide (TiO2), zinc oxide (ZnO), niobium pentoxide (Nb2O5), tin dioxide (SnO2), aluminum oxide (Al2O3), etc. are used. In particular, it is preferably configured using a sintered body of titanium dioxide (TiO2) capable of securing a large surface area for laminating the perovskite layer 44. A part of the blocking layer 3 extends into a recess 221 formed by removing a part of the transparent conductive film 22 to form an insulating layer 31, whereby the transparent conductive film 22 is partitioned into two. In the blocking layer 3, electrons can move in the stacking direction, but it is difficult for them to move in the lateral direction perpendicular to the stacking direction. Also, electrons cannot move between the two transparent conductive films 22 separated by the insulating layer 31. That is, the electrons that have entered the blocking layer 3 smoothly move in the stacking direction of the transparent conductive film 22 and are supplied to the photoelectrode 61, but the insulating layer 31 prevents the lateral movement toward the counter electrode 62, so that the photoelectrode 61 and the counter electrode 62 do not short-circuit.

[0016] The perovskite layer 44 is an organic and inorganic hybrid compound. Specifically, the perovskite layer 44 is formed by reacting a compound composed of lead and halogen element X (PbX2, X = halogen element) with methylammonium iodide (CH3NH3I: hereinafter may be abbreviated as "MAI"). Specifically, after infiltrating and drying a solution containing lead and halogen element X (for example, an N,N-dimethylformamide solution of PbI2) inside the pores of the porous semiconductor 41, and then immersing it in a mixed solution of MAI, crystals of the perovskite compound (when X = I, CH3NH3PbI3) that forms the perovskite layer 44 are rapidly generated. Note that as the halogen element X, iodine, bromine, chlorine, etc. can be used, and it is particularly preferable to use iodine with high morphological stability. Also, the halogen element X can be used as a mixed cation-mixed halide ((FAPbI3) 1-x (MAPbBr3) x ). In this case, for example, (FAPbI3) 0.85 (MAPbBr3) 0.15 etc. can be preferably used.

[0017] For the hole transport layer 5, a hole transport material described later is used. For the photoanode 61, for example, a single metal such as gold, platinum, silver, copper, etc., an alloy, 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 using carbon nanotubes (hereinafter sometimes abbreviated as CNT). CNT is a highly conductive and fibrous continuum. Due to the continuum, the resistance between particles is low, and the resistance of the electrode itself can be reduced. The counter electrode 62 according to the present embodiment is configured by laminating 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 located on the side of the hole transport layer 5, and a second CNT film 62b (an example of an electrode layer and a water-based carbon electrode layer) containing water-based carbon located on the side opposite to the hole transport layer 5 with the first CNT film 62a interposed therebetween.

[0019] Here, the principle of power generation of the solar cell 10 will be described with reference to FIG. 3. When light such as sunlight or indoor light is incident from the side of the transparent substrate 21, most of this incident light passes through the substrate 2 and the blocking layer 3 without being absorbed, and most of it reaches the power generation layer 4. Then, when the incident light that has reached the power generation layer 4 irradiates the perovskite layer 44, the perovskite layer 44 absorbs and excites the light energy. Due to this excitation, when the energy level of the perovskite layer 44 becomes higher than the conduction band potential of the metal oxide that is the porous semiconductor 41 by a predetermined level or more, electrons are injected from the perovskite layer 44 into the porous semiconductor 41. The injected electrons are collected by the photoelectrode 61 through the blocking layer 3.

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

Example

[0021] 〔Procedure for fabricating a solar cell〕 <Example> Next, an example of the solar cell 10 according to the present embodiment will be described. First, the manufacturing procedure of the solar cell 10 will be described with reference to FIG. 4. The solar cell 10 can be manufactured by referring to known techniques such as Michael Saliba et al., “Correction to “How to Make over 20% Efficient Perovskite Solar Cells in Regular (n-i-p) and Inverted (p-i-n) Architectures””, Chem. Mater., 2018, 30, 4193-4218, etc.

[0022] First, a transparent conductive film 22 is formed on a transparent substrate 21 to produce a substrate 2. The transparent conductive film 22 is laminated on the transparent substrate 21 by, for example, CVD (chemical vapor deposition) or sputtering. Next, after laser scribing is performed to partially remove the transparent conductive film 22 to form a recess 221 into which an insulating layer 31 enters, it is washed. Next, a blocking layer 3 is formed on the entire surface of the substrate 2 by the ALD method (atomic layer deposition method), the SPD method (spray pyrolysis method), or the like. The blocking layer 3 is preferably formed as a TiO2 dense layer. Next, a porous semiconductor 41, which is a nanoparticle sintered layer, is formed near the center on the masked substrate 2 and the blocking layer 3. The porous semiconductor 41 is preferably formed as a porous layer of TiO2 (p-TiO2). This porous semiconductor 41 is formed by diluting a nanoparticle paste with a solvent, applying it by, for example, the spin coating method at a rotation speed of 4000 rpm to 6000 rpm, drying it, then removing the masking and heating it at 450 °C to 550 °C for sintering.

[0023] Next, for example, a solution of PbI2 in N,N-dimethylformamide is prepared, dropped onto the porous semiconductor 41, and then, for example, penetration into the pores (p-TiO2) and removal of the excess solution are performed by spin coating at a rotation speed of 5000 rpm to 8000 rpm. It is dried at 60 °C to 120 °C (preferably 70 °C to 90 °C) to form a PbI2 layer.

[0024] Immerse the substrate 2, the blocking layer 3, and the porous semiconductor 41 infiltrated with lead iodide in an isopropyl alcohol solution of MAI (CH3NH3I) (2 mg / ml to 20 mg / ml) at 0 °C to 80 °C (preferably room temperature) (MAI immersion method). After PbI2 and MAI react to form a perovskite compound [(CH3NH3)PbI3 (MAPbI3)] as the perovskite layer 44 inside and on top of the pores of the porous semiconductor 41, rinse with pure isopropyl alcohol solution and dry at 60 °C to 120 °C (preferably 70 °C to 100 °C). Mixed cation-mixed halide ((FAPbI3) 1-x (MAPbBr3) x )-based perovskite compounds can be prepared in the same manner.

[0025] The above preparation procedure controls the crystal growth of the perovskite compound forming the perovskite layer 44 in two steps, but this may also be performed in one step. For example, a perovskite ((CH3NH3)PbI3) solution is infiltrated into the pores of the porous semiconductor 41 by the spin coating method. Next, toluene is dropped during spinning to precipitate microcrystals and mirror-polish the surface (poor solvent precipitation method).

[0026] The hole transport material according to this example is prepared, for example, as a chlorobenzene solution of 60 mg / ml to 90 mg / ml. The solution is dropped onto the perovskite layer 44, and excess solution is removed by the spin coating method and dried to form the hole transport layer 5. Additives such as TPFB may be added to the hole transport material. When adding TPFB, TPFB is preferably 0.01 wt% to 100 wt% of the hole transport material, and particularly preferably 0.1 wt% to 50 wt%. For example, the hole transport material according to this example is weighed to be 30 mM, and TPFB corresponding to 10 wt% thereof is added, and the hole transport layer 5 can be formed using a solution obtained by dissolving these in chlorobenzene. Note that the film thickness of the hole transport layer 5 in this example and Comparative Examples 1 to 4 described later is 200 nm, and the contact angle is 75 degrees.

[0027] The steps from the formation of the above PbI2 layer to the formation of the hole transport layer 5 are preferably carried out in a dry nitrogen atmosphere such as a glove box. Finally, the electrode 6 is formed. The photoelectrode 61 is formed by attaching a thin film such as gold to the surface of the blocking layer 3 by a vacuum evaporation method or the like.

[0028] As described above, the counter electrode 62 is a carbon electrode using CNT. In this embodiment, the counter electrode 62 includes a first CNT film 62a containing water-repellent carbon located on the side of the hole transport layer 5, and a second CNT film 62b containing water-based carbon located on the side opposite to the hole transport layer 5 with the first CNT film 62a interposed therebetween. That is, 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 obtained by applying a solution (hereinafter also referred to as the first CNT solution 63a) in which a first CNT containing water-repellent carbon, a resin binder, and a stabilizer component (hereinafter referred to as a binder, etc.) are dispersed in a solvent onto the hole transport layer 5 and then evaporating the solvent. As a result, the residue, the first CNT, dries to obtain the first CNT film 62a. Similarly, the second CNT film 62b is obtained by applying a solution (hereinafter also referred to as the second CNT solution 63b) in which a second CNT containing water-based carbon and a resin binder, etc. are dispersed in a solvent onto the first CNT film 62a and then evaporating the solvent. As a result, the residue, the second CNT, dries to obtain the second CNT film 62b. Hereinafter, the manufacturing methods of the first CNT film 62a and the second CNT film 62b will be described in detail.

[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 first CNTs having a water-repellent function, 1.0 wt% to 4.0 wt% of a resin binder, and a 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 has a diameter of 5 nm or more and 20 nm or less, and a length of 1 μm or more and 3 mm or less. The first binder, etc. are preferably acrylic, fluorine-based, ethylene oxide-based, paraffin-based, wax-based, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. The solvent is preferably alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, etc.

[0031] The first CNT solution 63a prepared as described above is applied to the surface of the hole transport layer 5, for example, to a thickness of 150 μm. Then, the solvent is evaporated to dry the first CNT. The method of evaporating the solvent is, for example, heating at 80°C for 5 minutes. When the solvent evaporates, the residue, the first CNT, becomes the first CNT film 62a. The film thickness of the first CNT film 62a is 1 μm to 5 μm. The coating amount of the first CNT solution 63a on the surface of the hole transport layer 5 is not limited to 150 μm, and can be adjusted so that the film thickness of the first CNT film 62a is 1 μm to 5 μm. Note that the film thickness of the first CNT film 62a in this example is 5 μm. The resistance value of the water-repellent carbon is about 100 to 200 times that of the water-based carbon, and is significantly higher than that of the water-based carbon. Therefore, it is desirable to make the film 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, 0.9 wt% to 17.0 wt% of a resin binder, and a 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 has a diameter of 5 nm or more and 20 nm or less and a length of 1 μm or more and 3 mm or less. The second binder, etc. is preferably an acrylic-based, polyvinyl alcohol-based, hydroxycellulose-based, or the like.

[0033] The second CNT solution 63b prepared as described above is applied to the surface of the first CNT film 62a, for example, in an amount of 1200 μm. Then, the solvent (water) is evaporated to dry the second CNT. The method of evaporating the solvent is, for example, heating at 100 °C for 5 minutes. When the solvent evaporates, the residue, the second CNT, becomes the second CNT film 62b. The film thickness of the second CNT film 62b is 20 μm to 25 μm. The coating amount of the second CNT solution 63b on the surface of the first CNT film 62a is not limited to 1200 μm and can be adjusted so that the film thickness of the second CNT film 62b is 20 μm to 25 μm. Note that the film thickness of the second CNT film 62b in this example is 20 μm.

[0034] <Comparative Example 1> The solar cell of Comparative Example 1 is different from the solar cell 10 of this example in that the counter electrode does not have a first CNT film and is composed only of a second CNT film made of gold with a film thickness of 0.1 μm. Other configurations are the same as those of the solar cell 10 of this example.

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

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

[0037] <Comparative Example 4> The solar cell of Comparative Example 4 is different from the solar cell 10 of the present embodiment 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-based carbon with a film thickness of 20 μm. Other configurations are the same as those of the solar cell 10 of the present embodiment.

[0038] For the examples of the solar cell 10 and Comparative Examples 1 to 4 manufactured by the above manufacturing method, the contact angle of the first CNT film, the resistance value of the counter electrode, and the photoelectric conversion efficiency of the solar cell were measured. The contact angle measurement in the present example and Comparative Examples 1 to 4 was carried out according to JIS R3257 "Test method for wettability of substrate glass surface". The contact angle was measured using a contact angle measuring machine "CAM-004" manufactured by FLOWDESIGN Co., Ltd. Also, the resistance value was measured according to JIS K7194 "Test method for resistivity of conductive plastics by four-probe method". The shape of the counter electrode 62 during the resistance value measurement is a rectangular shape of 26 mm × 30 mm. The photoelectric conversion efficiency of the solar cell 10 is represented by the relative value (hereinafter, also referred to as the relative value of the 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]

Table 1

[0040] 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 value of the counter electrode 62 was 10 Ω / sq, and the relative value of the photoelectric conversion efficiency was 0.96. Generally, if the contact angle is 90 degrees or more, it can be said to have water repellency. Therefore, the first CNT film 62a of this example has water repellency. Since the relative value of the photoelectric conversion efficiency of this example is 0.96 and is close to 1, it can be seen that the solvent of the first CNT solution 63a used when forming the first CNT film 62a hardly penetrated into the hole transport layer 5 and the perovskite layer 44, and the penetration was suppressed.

[0041] Generally, it is desirable that the resistance value of the counter electrode 62 in a solar cell is 20 Ω / sq or less, and more desirably 10 Ω / sq or less. Since the resistance value of the solar cell 10 of this example is 10 Ω / sq, it satisfies the requirement of the desirable resistance value. Furthermore, since the material of the counter electrode 62 of the solar cell 10 of this example is carbon, it is advantageous in terms of cost compared to gold. Therefore, the solar cell 10 of this example has practicality from all viewpoints of resistance value, photoelectric conversion efficiency, and cost. Note that to further lower the resistance value, the film thickness of the second CNT film 62b may 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. Although Comparative Example 1 is excellent in both resistance value and photoelectric conversion efficiency and has practicality, since the material of the counter electrode is gold and it is expensive, it does not have practicality from the viewpoint of cost.

[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. That is, 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 of the second CNT film. Therefore, it is considered that the solvent of the second CNT solution used when forming the second CNT film penetrated into the hole transport layer 5 and the perovskite layer 44 and did not generate electricity. Therefore, the solar cell of Comparative Example 2 has practicality from the viewpoint of resistance value, but does not have practicality from the viewpoint 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 of the second CNT film. Therefore, although the intrusion of the solvent of the second CNT solution used when forming the second CNT film into the hole transport layer 5 and the perovskite layer 44 was suppressed, the resistance value of the counter electrode increased, and for this reason, the photoelectric conversion efficiency is considered to have also decreased. Therefore, the solar cell of Comparative Example 3 does not have practicality from the viewpoints of both the resistance value and the photoelectric conversion efficiency.

[0045]

[0044] 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 of the first CNT film, and water-based carbon was used as the material of the second CNT film. Therefore, the solvents of the first CNT solution and the second CNT solution used when forming the first CNT film and the second CNT film invaded the hole transport layer 5 and the perovskite layer 44, and the photoelectric conversion efficiency is considered to have decreased. Therefore, the solar cell of Comparative Example 4 has practicality from the viewpoint of the resistance value, but does not have practicality from the viewpoint of the photoelectric conversion efficiency.

[0046] 〔Outline of the above embodiment〕 The following configuration is recalled in the perovskite solar cell (10) described in the above embodiment.

[0047] <1>One aspect of the perovskite solar cell (10) is a perovskite solar cell (10) having a counter electrode (62) in which at least two electrode layers are laminated adjacent to the hole transport layer (5), and the two electrode layers are a water-repellent electrode layer (62a) containing water-repellent carbon located on the side of the hole transport layer (5), and a water-based electrode layer (62b) containing water-based carbon located on the side opposite to the hole transport layer (5) with the water-repellent electrode layer (62a) interposed therebetween.

[0048] The solution (63a) containing water-repellent carbon, which becomes the water-repellent electrode layer (62a) by 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) hardly penetrates into the hole transport layer (5) and also hardly penetrates into 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 side opposite to the hole transport layer (5) with the water-repellent electrode layer (62a) interposed therebetween, and the anode electrode (62) is constituted by the water-repellent electrode layer (62a) and the aqueous electrode layer (62b). 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, since the solution (63b) containing aqueous carbon is applied on the water-repellent electrode layer (62a), the penetration of the solution into the hole transport layer (5) is suppressed by the water-repellent electrode layer (62a). Thus, by configuring the anode electrode (62) with the water-repellent electrode layer (62a) and the aqueous electrode layer (62b), a perovskite solar cell (10) having a low-resistance anode electrode (62) and in which a decrease in the photoelectric conversion efficiency is suppressed can be obtained.

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

[0051] Generally, if the contact angle is 90 degrees or more, it can be said to have water repellency. Therefore, the water-repellent electrode layer (62a) has water repellency. For this reason, when applying and drying a solution (63a) containing water-repellent carbon to form the water-repellent electrode layer (62a), it is difficult for the solution (63a) to penetrate into the hole transport layer (5) and also difficult to penetrate into the perovskite layer (44). Thus, a perovskite solar cell (10) with suppressed reduction in photoelectric conversion efficiency can be obtained.

[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] Generally, it is desirable that the resistance value of the anode electrode (62) in a solar cell is 20 Ω / sq or less. Therefore, the perovskite solar cell (10) in which the resistance value of the anode electrode (62) is 10 Ω / sq or less has practicality from the viewpoint of the resistance value.

[0054] <4>In the perovskite solar cell (10) described in any one of <1> to <3> above, it is preferable that the thickness of the hydrophilic electrode layer (62b) is thicker 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 hydrophilic electrode layer (62b). Also, the anode electrode (62) of the perovskite solar cell (10) is required to have low resistance. Therefore, by making the thickness of the hydrophilic electrode layer (62b) thicker than the thickness of the water-repellent electrode layer (62a), a perovskite solar cell (10) having a low-resistance anode electrode (62) and suppressed reduction in photoelectric conversion efficiency can be obtained by manufacturing the perovskite solar cell (10) by the simple process as described above.

Industrial Applicability

[0056] The present disclosure can be applied to perovskite solar cells.

Explanation of Reference Numerals

[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, water-based electrode layer)

Claims

1. A perovskite solar cell having an anode electrode that is disposed adjacent to a hole transport layer and in which at least two electrode layers are stacked, 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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