Solar cell

Abstract

A solar cell 10 according to the present disclosure comprises a first electrode 101, a first transport layer (for example, an electron transport layer 102), a photoelectric conversion layer 103, and a second electrode 105 in this order. The first transport layer has a first main surface 110 in contact with the photoelectric conversion layer 103. The first main surface 110 includes a first flat surface part 111 and a first protrusion 112 protruding from the first flat surface part 111. The first transport layer has a higher elastic modulus than the photoelectric conversion layer 103.

Description

Solar cell

[0001] The present disclosure relates to a solar cell.

[0002] In recent years, research and development of organic thin-film solar cells and perovskite solar cells have been underway as new solar cells to replace existing silicon-based solar cells. Perovskite solar cells use a perovskite-type crystal represented by ABX3 (A is a monovalent cation, B is a divalent cation, and X is a halogen anion) and its similar structures (hereinafter referred to as "perovskite compounds") as the photoelectric conversion material.

[0003] Various technologies for improving the characteristics of perovskite solar cells have been proposed. For example, Patent Document 1 discloses a perovskite solar cell provided with an electron transport layer containing a mixture of SnO2 and a metal oxide different from SnO2 for the purpose of extending the lifespan.

[0004] Japanese Patent Application Laid-Open No. 2023-130980

[0005] In order to enhance the durability of a solar cell, the solar cell is usually sealed with a sealing structure for protection from ambient oxygen and water vapor. In the prior art, there was a problem that during sealing, the solar cell was pressurized by a sealing material or the like, resulting in damage and delamination of the solar cell. Also, there was a problem that defects such as cracks and delamination in the photoelectric conversion layer could occur when forming the photoelectric conversion layer that constitutes the solar cell.

[0006] The present disclosure provides a technique for making it difficult for a solar cell to be damaged, delaminated, and defective in the photoelectric conversion layer that may occur during sealing of the solar cell or when forming the photoelectric conversion layer of the solar cell.

[0007] The solar cell of the present disclosure includes a first electrode, a first transport layer, a photoelectric conversion layer, and a second electrode in this order. The first transport layer has a first main surface in contact with the photoelectric conversion layer. The first main surface includes a first flat portion and a first convex portion protruding from the first flat portion. The first transport layer has a higher elastic modulus than the photoelectric conversion layer.

[0008] According to the technology disclosed herein, damage and delamination of solar cells, as well as defects in the photoelectric conversion layer, which may occur during the encapsulation of solar cells or during the formation of the photoelectric conversion layer of solar cells, can be made less likely.

[0009] Figure 1 shows a cross-sectional view of a solar cell according to Embodiment 1 of the present disclosure. Figure 2 shows a cross-sectional view of a solar cell according to Embodiment 2 of the present disclosure. Figure 3 shows a cross-sectional view of a solar cell according to Embodiment 3 of the present disclosure. Figure 4 shows a cross-sectional view of a solar cell according to Embodiment 4 of the present disclosure. Figure 5 shows a cross-sectional view of a solar cell according to Embodiment 5 of the present disclosure. Figure 6 shows a cross-sectional view of a solar cell according to Embodiment 6 of the present disclosure. Figure 7 shows a cross-sectional view of a solar cell according to Embodiment 7 of the present disclosure. Figure 8 shows a cross-sectional view of a solar cell according to Embodiment 8 of the present disclosure.

[0010] A solar cell according to an embodiment of the present disclosure comprises a first electrode, a first transport layer, a photoelectric conversion layer, and a second electrode in this order. The first transport layer has a first main surface in contact with the photoelectric conversion layer. The first main surface includes a first planar portion and a first convex portion protruding from the first planar portion.

[0011] Herein, in this specification, "flat portion" means a region on the surface where the difference in surface irregularities is 40 nm or less. Furthermore, in this specification, "protruding portion" means a region that protrudes from the flat portion by a height of 200 nm or more.

[0012] Furthermore, the solar cell according to the embodiment of this disclosure may further include other components in addition to the components described above. For example, the solar cell according to the embodiment of this disclosure may further include other layers (e.g., an intermediate layer) disposed between the above components. For example, the solar cell according to the embodiment of this disclosure may further include a hole transport layer disposed between the photoelectric conversion layer and the second electrode.

[0013] Because the first main surface of the first transport layer is in contact with the photoelectric conversion layer by the first main surface including the first protrusion described above, even when the solar cell is pressurized by a sealing material during sealing, damage to the solar cell or delamination is less likely to occur due to, for example, the anchoring effect of the first protrusion. Furthermore, if the first transport layer is, for example, an electron transport layer, cracks and delamination of the photoelectric conversion layer and hole transport layer are less likely to occur when forming the photoelectric conversion layer or hole transport layer that constitutes the solar cell. Therefore, the solar cell according to the embodiment of this disclosure can suppress damage such as cracks and delamination during manufacturing and sealing, thereby maintaining high electrical characteristics and improving reliability.

[0014] Hereinafter, solar cells of embodiments 1 to 8 of the present disclosure will be described with reference to the drawings. In embodiments 1 to 8 described below, a solar cell comprising a first electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and a second electrode in that order will be described as one embodiment of the solar cell of the present disclosure.

[0015] (Embodiment 1) Figure 1 shows a cross-sectional view of a solar cell according to Embodiment 1 of the present disclosure.

[0016] As shown in Figure 1, the solar cell 10 is provided on a substrate 106 in the following order: a first electrode 101, an electron transport layer 102, a photoelectric conversion layer 103, a hole transport layer 104, and a second electrode 105.

[0017] The order in which the layers of the solar cell are formed is not limited to the above, and a reverse configuration in which some or all of the layers are arranged in the opposite order from the photoelectric conversion layer is also possible. For example, the solar cell may be constructed on the substrate 106 in the order of first electrode, hole transport layer, photoelectric conversion layer, electron transport layer, and second electrode.

[0018] (Substrate 106) The substrate 106 plays the role of holding each layer of the solar cell 10.

[0019] The substrate 106 can be formed from a transparent material. As such a substrate 106, a glass substrate or a plastic substrate can be used. The plastic substrate may be a plastic film. The material of the glass substrate is not particularly limited, and various types of glass, such as soda-lime silicate, can be used. The substrate 106 may also be a film, particularly a plastic film. As materials for the plastic substrate and plastic film, polyimide, polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymers, and the like can be used.

[0020] If the second electrode 105 is translucent, the substrate 106 may be made of a material that is not translucent. As such a material, metals, ceramics, or resin materials with low translucency can be used.

[0021] If the first electrode 101 has sufficient strength, the first electrode 101 can hold each layer, so it is not necessary to provide the substrate 106.

[0022] (First electrode 101) The first electrode 101 is conductive. The first electrode 101 plays a role in leading electrons or holes from the solar cell.

[0023] The first electrode 101 may be light-transmitting. For example, the first electrode 101 transmits light from the visible region to the near-infrared region.

[0024] The first electrode 101 may be composed of, for example, a transparent and conductive metal oxide. Examples of such metal oxides include: (i) indium-tin composite oxide, (ii) indium-zinc composite oxide, (iii) antimony-doped tin oxide, (iv) fluorine-doped tin oxide, (v) zinc oxide doped with at least one element selected from the group consisting of boron, aluminum, gallium, and indium, or (vi) composites thereof.

[0025] The first electrode 101 may be formed using an opaque material with a light-transmitting pattern. Examples of light-transmitting patterns include linear (e.g., stripe), wavy, grid (e.g., mesh), or perforated metal-like patterns with a large number of fine through-holes arranged regularly or irregularly. When the first electrode 101 has these patterns, light can be transmitted through areas where there is no electrode material.

[0026] Examples of opaque materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or alloys containing any of these. Conductive carbon materials may also be used as opaque materials.

[0027] The light transmittance of the first electrode 101 may be, for example, 50% or more, or 80% or more. The wavelength of light that the first electrode 101 should transmit depends on the absorption wavelength of the photoelectric conversion layer 103.

[0028] The first electrode 101 may have a thickness of, for example, 1 nm or more and 1000 nm or less.

[0029] (Electron transport layer 102) As described above, the electron transport layer 102 has a first main surface 110 that is in contact with the photoelectric conversion layer 103. The first main surface 110 includes a first flat portion 111 and a first protrusion 112 that protrudes from the first flat portion 111. The first protrusion 112 protrudes from the first flat portion 111 to a height of 200 nm or more, may protrude to a height of 300 nm or more, or may protrude to a height of 500 nm or more. The height of the first protrusion 112 may be, for example, 1.5 μm or less from the first flat portion 111.

[0030] The electron transport layer 102 may have a portion that is thicker than the portion of the first flat surface 111. The thickness of the thicker portion may be twice or more the thickness of the portion of the first flat surface 111, or it may be five times or more.

[0031] The thicker portion described above may be the first protrusion 112. That is, the thickness of the electron transport layer 102 in the first protrusion 112 may be greater than the thickness of the electron transport layer 102 in the first flat portion 111. This makes it possible to more effectively suppress damage such as cracks and delamination of the first protrusion 112 during the manufacturing and sealing of the solar cell 10. Therefore, the solar cell 10 can maintain higher electrical characteristics and have greater reliability.

[0032] The electron transport layer 102 transports electrons. The electron transport layer 102 includes a semiconductor. Preferably, the electron transport layer 102 is formed from a semiconductor with a band gap of 3.0 eV or more. This allows visible light and infrared light to be transmitted to the photoelectric conversion layer 103.

[0033] Examples of semiconductors include organic or inorganic n-type semiconductors, but inorganic n-type semiconductors are preferred. Examples of inorganic n-type semiconductors are metal oxides. Examples of metal oxides are oxides of Cd, Zn, In, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, or Cr. An example of a metal oxide is SnO2.

[0034] It is desirable that the electron transport layer 102 contains a metal oxide. Metal oxides are generally harder than organic materials. Therefore, for example, if the photoelectric conversion layer 103 is an organic layer formed from an organic material such as a perovskite compound, the hard first protrusions 112 of the electron transport layer 102, which is made of a metal oxide, penetrate into the interior of the organic layer that is the photoelectric conversion layer 103, allowing the first protrusions 112 to act more effectively as anchors. Therefore, by including a metal oxide in the electron transport layer 102, damage such as cracks and delamination during the manufacturing and sealing of the solar cell 10 can be more effectively suppressed. As a result, the solar cell 10 can maintain higher electrical characteristics and have higher reliability.

[0035] The electron transport layer 102 may, for example, contain SnO2 as its main component. Here, the main component is the component that has the largest mass proportion among the components constituting the electron transport layer 102. By containing SnO2 as the main component of the electron transport layer 102, a film with excellent light transmittance can be formed at a low temperature that allows for the use of an organic substrate.

[0036] It is desirable that the electron transport layer 102 has a higher elastic modulus than the photoelectric conversion layer 103. This makes cracking and delamination of the photoelectric conversion layer 103 less likely. Furthermore, even when the solar cell 10 is pressurized, damage and delamination are less likely to occur.

[0037] When a hole transport layer 104 is provided, as in the solar cell 10 shown in Figure 1, it is desirable that the electron transport layer 102 has a higher elastic modulus than the photoelectric conversion layer 103 and the hole transport layer 104. This makes cracking and delamination of the photoelectric conversion layer 103 and the hole transport layer 104 less likely. Furthermore, even when the solar cell 10 is pressurized, damage and delamination are less likely to occur.

[0038] The elastic moduli of the electron transport layer 102, the photoelectric conversion layer 103, and the hole transport layer 104 can be confirmed by methods such as nanoindentation.

[0039] As shown in Figure 1, the first protrusion 112 of the electron transport layer 102 is, for example, columnar. This allows the first protrusion 112 to act more effectively as an anchor, thereby more effectively suppressing damage such as cracks and delamination during the manufacturing and sealing of the solar cell 10. Consequently, the solar cell 10 can maintain higher electrical characteristics and have greater reliability.

[0040] The electron transport layer 102 can be formed by coating or printing. For coating methods, examples include slit die coating, spray coating, spin coating, and inkjet coating. For printing methods, examples include gravure printing, flexographic printing, and inkjet printing. However, the method is not limited to these.

[0041] The method for forming the first convex portion 112 of the electron transport layer 102 is not particularly limited, and the above-described methods may be combined. For example, the first planar portion 111 of the electron transport layer 102 can be formed by a coating method, and then the first convex portion 112 can be formed by a printing method. Further, for example, by mixing particles in the solution for forming the electron transport layer 102 and applying the mixture, the first convex portion 112 can be formed by the particles.

[0042] When the precursor material of the electron transport layer is a nanoparticle dispersion of an oxide, such as when the electron transport layer 102 contains a metal oxide, it is desirable to use a coating method as the method for forming the electron transport layer 102. By doing so, the precursor material of the electron transport layer 102 can be made into a particle mist during coating, and the first convex portion 112 can be formed more efficiently.

[0043] In FIG. 1, only one first convex portion 112 is illustrated, but a plurality of first convex portions 112 may be included in the first main surface 110 of the electron transport layer 102. That is, the first convex portions 112 may be formed at a plurality of locations in the solar cell 10. The number and arrangement position of the first convex portions 112 are not particularly limited, but it is desirable to form them randomly or discretely. Conversely, if the first convex portions 112 are formed regularly or continuously, the non-formed surface of the first convex portions 112 becomes a relatively concave portion, and the interface between the electron transport layer 102 and the photoelectric conversion layer 103 becomes a substantially uneven surface. As a result, adverse effects such as uneven formation of the photoelectric conversion layer 103 may occur. In the present disclosure, by forming the first convex portions 112 randomly or discretely, the anchor effect by the first convex portions 112 can be obtained more effectively.

[0044] (Photoelectric conversion layer 103) The photoelectric conversion layer 103 contains a photoelectric conversion material.

[0045] The photoelectric conversion material may be, for example, a perovskite compound. That is, the photoelectric conversion layer 103 may contain a perovskite compound.

[0046] Perovskite compounds have high light absorption coefficients and high carrier mobility in the wavelength range of the solar spectrum. Therefore, solar cells containing perovskite compounds (i.e., perovskite solar cells) have high photoelectric conversion efficiency.

[0047] Perovskite compounds are represented, for example, by the compositional formula ABX3, where A is a monovalent cation, B is a divalent metal cation, and X is a monovalent anion.

[0048] Examples of monovalent cation A are organic cations or alkali metal cations.

[0049] An example of an organic cation is the methylammonium cation (CH3NH3) + ) or formamidinium cation (NH2CHNH2 + )

[0050] Examples of alkali metal cations are Cs cations or Rb cations.

[0051] Examples of divalent cation B include Pb cations, Sn cations, or Ge cations.

[0052] Examples of monovalent anions X are halogen anions. Halogen anions include, for example, chloride anions, bromine anions, or iodine anions.

[0053] A, B, and X may each contain multiple types of ions.

[0054] The thickness of the photoelectric conversion layer 103 depends on the magnitude of its light absorption, but for example, it is between 100 nm and 2000 nm.

[0055] The photoelectric conversion layer 103 can be formed using a solution coating method or the like.

[0056] (Hole transport layer 104) The hole transport layer 104 contains a hole transport material. The hole transport material is a material that transports holes.

[0057] The hole transport material may be a triphenylamine derivative. Examples of triphenylamine derivatives are poly[bis(4-phenyl)(2,4,6-triphenylmethyl)amine] (hereinafter referred to as "PTAA") or PTAA derivatives. In PTAA derivatives, at least some of the hydrogen atoms or methyl groups of PTAA may be replaced with other functional groups. For example, at least some of the methyl groups of PTAA may be replaced with hydrogen atoms or methoxy groups. Alternatively, at least some of the hydrogen atoms of PTAA may be replaced with methyl groups or methoxy groups.

[0058] The hole transport layer 104 may contain not only a triphenylamine derivative but also other hole transport materials. Examples of hole transport materials include organic or inorganic semiconductors.

[0059] Examples of organic materials used as hole transport materials include Poly(3-hexylthiophene-2,5-diyl) (hereinafter referred to as "P3HT") or Poly(3,4-ethylenedioxythiophene) (hereinafter referred to as "PEDOT"). The molecular weight is not particularly limited, but it may be a polymer.

[0060] Inorganic semiconductors used as hole transport materials are p-type semiconductors. Examples of inorganic semiconductors used as hole transport materials include Cu₂O, CuGaO₂, CuSCN, CuI, CuPC, and NiO₂. x MoO y The material is a carbon-based material such as V2O5 or graphene oxide. Here, 0 < x and 1 ≤ x ≤ 1.5 may also be true. Also, 0 < y and 2 ≤ y ≤ 3 may be true.

[0061] The hole transport layer 104 may contain not only the hole transport layer material but also a fluoroboron compound. The fluoroboron compound is added as an additive to increase the hole concentration. The fluoroboron compound has high stability and a suitable redox potential for oxidizing the hole transport material.

[0062] Fluoroboron compounds are, for example, boron compounds having a pentafluorophenyl group. Examples of such compounds include tris(pentafluorophenyl)borane (TPFPB), 4-Isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, or N,N-Dimethylanilinium tetrakis(pentafluorophenyl)borate. Fluoroboron compounds may also be TPFPB or TPFPB derivatives.

[0063] The hole transport layer 104 may include multiple layers formed from different materials.

[0064] The thickness of the hole transport layer 104 may be 1 nm or more and 1000 nm or less, or 10 nm or more and 500 nm or less, in order to reduce resistance.

[0065] Examples of methods for forming the hole transport layer 104 include coating or printing. Examples of coating methods include doctor blade method, bar coating method, spray method, dip coating method, or spin coating method. An example of a printing method is screen printing. The hole transport layer 104 may also be formed by pressurizing or firing a film obtained by mixing multiple materials. If the hole transport material is a low-molecular-weight organic or inorganic semiconductor, the hole transport layer 104 may be formed by vacuum deposition.

[0066] When forming the hole transport layer 104 before the photoelectric conversion layer 103, it is desirable to use a coating method for forming the hole transport layer 104. Furthermore, in order to be suitable for formation using a coating method, it is desirable that the precursor material of the hole transport layer 104 be a dispersion. This allows the precursor material of the hole transport layer 104 to be formed as a particulate mist during coating, enabling the formation of the first protrusion more efficiently.

[0067] The hole transport layer 104 may contain a supporting electrolyte and a solvent. The supporting electrolyte and solvent have the effect of stabilizing the holes in the hole transport layer 104.

[0068] Examples of supporting electrolytes are ammonium salts or alkali metal salts. Examples of ammonium salts are tetrabutylammonium perchlorate, tetraethylammonium hexafluoride phosphate, imidazolium salts, or pyridinium salts. Examples of alkali metal salts are lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and LiN(SO2CnF). 2n+1 ) 2. LiPF6, LiBF4, lithium perchlorate, or potassium borotetrafluoride.

[0069] The solvent contained in the hole transport layer 104 may have high ionic conductivity. The solvent may be an aqueous solvent or an organic solvent. To stabilize the solute, the solvent may be an organic solvent. Examples of organic solvents are heterocyclic compounds such as 4-tert-butylpyridine (hereinafter referred to as "tBP"), pyridine, and n-methylpyrrolidone.

[0070] Ionic liquids may be used alone as a solvent, or mixed with other solvents. Ionic liquids have low volatility and high flame retardancy.

[0071] Examples of ionic liquids include imidazolium compounds such as 1-ethyl-3-methylimidazolium tetracyanoborate, pyridine compounds, alicyclic amine compounds, aliphatic amine compounds, or azonium amine compounds.

[0072] (Second electrode 105) The second electrode 105 is conductive.

[0073] If the solar cell 10 does not have a hole transport layer 104, the second electrode 105 has blocking properties for electrons from the photoelectric conversion layer 103. In this case, the second electrode 105 does not make ohmic contact with the photoelectric conversion layer 103. Blocking properties for electrons from the photoelectric conversion layer 103 refer to the property of allowing only holes generated in the photoelectric conversion layer 103 to pass through, while preventing electrons from passing through. The Fermi energy of a material having such properties is lower than the energy of the lower end of the conduction band of the photoelectric conversion layer 103. The Fermi energy of a material having such properties may also be lower than the Fermi energy of the photoelectric conversion layer 103. Specific materials include platinum, gold, or carbon materials such as graphene.

[0074] If the solar cell 10 includes a hole transport layer 104, the second electrode 105 does not need to have blocking properties for electrons from the photoelectric conversion layer 103. In this case, the second electrode 105 may be made of a material capable of forming ohmic contact with the photoelectric conversion layer 103. This allows the second electrode 105 to be formed to be translucent.

[0075] The second electrode 105 may be composed of, for example, a transparent and conductive oxide. Examples of such oxides include indium-tin composite oxide, indium-zinc composite oxide, or indium-tungsten composite oxide. Thus, the second electrode 105 may contain a conductive oxide with indium oxide as the base material. From the viewpoint of film quality stability, the second electrode 105 may contain an indium-zinc composite oxide.

[0076] Of the first electrode 101 and the second electrode 105, at least the electrode on the side into which light is incident only needs to be light-transmitting. Therefore, one of the first electrode 101 and the second electrode 105 does not need to be light-transmitting. In other words, one of the first electrode 101 and the second electrode 105 does not need to be made of a light-transmitting material, nor does it need to have a pattern that includes an opening that transmits light.

[0077] An example of a method for forming the second electrode 105 is vapor phase growth. Examples of vapor phase growth methods include chemical vapor deposition or sputtering.

[0078] A protective layer may be formed between the hole transport layer 104 and the second electrode 105. The protective layer may be MoO y V2O5 can be used. By forming a protective layer, the durability of the solar cell against oxygen and moisture can be improved. Here, 0 < y and 2 ≤ y ≤ 3 may also be applicable.

[0079] (Method for manufacturing the solar cell 10) The solar cell 10 according to this embodiment can be manufactured, for example, by the following method.

[0080] First, a first electrode 101 is formed on the surface of the substrate 106, for example by chemical vapor deposition or sputtering. Next, an electron transport layer 102 is formed on the first electrode 101, for example by the coating method described above, having a first main surface 110 including a first flat portion 111 and a first convex portion 112 protruding from the first flat portion 111. Next, a photoelectric conversion layer 103 is formed on the first main surface 110 of the electron transport layer 102, for example by coating, so as to cover the first convex portion 112. Next, a hole transport layer 104 is formed on the photoelectric conversion layer 103, for example by coating. Next, a second electrode 105 is formed on the hole transport layer 104, for example by sputtering.

[0081] In this way, a solar cell 10 is obtained.

[0082] (Embodiment 2) Figure 2 shows a cross-sectional view of a solar cell according to Embodiment 2 of the present disclosure.

[0083] The solar cell 20 according to Embodiment 2 differs from the solar cell 10 according to Embodiment 1 in that the shape of the first protrusion provided on the first main surface of the electron transport layer is different. With respect to all other configurations except the shape of the first protrusion, the solar cell 20 according to Embodiment 2 is the same as the solar cell 10 according to Embodiment 1.

[0084] As shown in Figure 2, in the solar cell 20 according to Embodiment 2, the first protrusion 212 included in the first main surface 210 of the electron transport layer 202 is spherical. That is, in the solar cell 20, the electron transport layer 202 has a first main surface 210 that is in contact with the photoelectric conversion layer 103, and the first main surface 210 includes a first flat portion 211 and a spherical first protrusion 212 that protrudes from the first flat portion 211.

[0085] The electron transport layer 202, which includes a spherical first protrusion 212 on the first main surface 210, can be formed in the same manner as the electron transport layer 102 of the solar cell 10 according to Embodiment 1. In other words, the solar cell 20 can be manufactured in the same manner as the manufacturing method of the solar cell 10 described in Embodiment 1.

[0086] Because the first protrusion 212 is spherical, it becomes easier to form the first protrusion 212 by coating and printing methods. Also, when multiple first protrusions 212 are provided, it becomes easier to make the heights of the multiple first protrusions 212 uniform.

[0087] The first protrusion 212 does not need to be a perfect sphere; it only needs to be spherical in shape. Here, "spherical" includes hemispherical shapes. In Figure 2, the first protrusion 212 has a constricted neck-like shape at the joint between the first protrusion 212 and the first flat portion 211, but the design is not limited to this, and the first protrusion 212 may be hemispherical, protruding from the first flat portion 211.

[0088] Although only one first protrusion 212 is shown in Figure 2, there may be multiple first protrusions 212 on the first main surface 110 of the electron transport layer 202. In other words, there may be multiple first protrusions 212 formed in the solar cell 20. The number and placement of the first protrusions 212 are not particularly limited.

[0089] The height range of the first protrusion 212 from the first flat surface 211 may be the same as the height range of the first protrusion 112 from the first flat surface 111 in the solar cell 10 described in Embodiment 1.

[0090] (Embodiment 3) Figure 3 shows a cross-sectional view of a solar cell according to Embodiment 3 of the present disclosure.

[0091] The solar cell 30 according to Embodiment 3 differs from the solar cell 10 according to Embodiment 1 in that the first protrusion provided on the first main surface of the electron transport layer is different. With respect to the other components except for the first protrusion, the solar cell 30 according to Embodiment 3 is the same as the solar cell 10 according to Embodiment 1.

[0092] As shown in Figure 3, in the solar cell 30 according to Embodiment 3, the first protrusion 312 included in the first main surface 310 of the electron transport layer 302 penetrates the photoelectric conversion layer 103 and is in contact with the hole transport layer 104. That is, in the solar cell 30, the electron transport layer 302 has a first main surface 310 that is in contact with the photoelectric conversion layer 103, and the first main surface 310 includes a first flat portion 311 and a first protrusion 312 that protrudes from the first flat portion 311 and is in contact with the hole transport layer 104.

[0093] The electron transport layer 302, which has a first protrusion 312 that penetrates the photoelectric conversion layer 103 and contacts the hole transport layer 104, can be formed in the same way as the electron transport layer 102 of the solar cell 10 according to Embodiment 1. Specifically, the electron transport layer 302 can be formed using the method for forming the electron transport layer 102 described in Embodiment 1, such that the height of the first protrusion 312 protruding from the first planar portion 311 is greater than the thickness of the photoelectric conversion layer 103. In other words, the solar cell 30 can be manufactured in the same way as the solar cell 10 manufacturing method described in Embodiment 1.

[0094] The configuration in which the first protrusion 312 penetrates the photoelectric conversion layer 103 and contacts the hole transport layer 104 makes it less likely for the solar cell 30 to be damaged or delamination to occur even when the solar cell 30 is pressurized by a sealing material during sealing. It also makes it less likely for cracks to occur in the photoelectric conversion layer 103. As a result, the first protrusion 312 can more effectively suppress damage such as cracks and delamination that occur during the manufacturing and sealing of the solar cell 30. Therefore, the solar cell 30 can maintain higher electrical characteristics and have higher reliability.

[0095] Furthermore, as described above, an n-type semiconductor may be used for the electron transport layer 302, and a p-type semiconductor may be used for the hole transport layer 104. When an n-type semiconductor is used for the electron transport layer 302 and a p-type semiconductor is used for the hole transport layer 104, a pn junction is formed when the first protrusion 312 comes into contact with the hole transport layer 104. This pn junction can act as a bypass to release electricity when a large voltage is applied locally to the solar cell 30. Therefore, the solar cell 30 can maintain even higher electrical characteristics and further improve reliability.

[0096] As described above, the solar cell 30 according to Embodiment 3 can have higher performance because, in addition to suppressing damage and delamination of the solar cell 30 due to the anchoring effect of the first protrusion 312, it also benefits from the bypass effect due to the formation of a pn junction.

[0097] Although only one first protrusion 312 is shown in Figure 3, multiple first protrusions 312 may be included on the first main surface 310 of the electron transport layer 302. In other words, multiple first protrusions 312 may be formed in the solar cell 30. The number and placement of the first protrusions 312 are not particularly limited.

[0098] Although Figure 3 shows an example where the first protrusion 312 in contact with the hole transport layer 104 is columnar, the shape of the first protrusion 312 may be spherical, as described in Embodiment 2.

[0099] The height range of the first protrusion 312 from the first planar portion 311 may be the same as the height range of the first protrusion 112 from the first planar portion 111 in the solar cell 10 described in Embodiment 1.

[0100] (Embodiment 4) Figure 4 shows a cross-sectional view of a solar cell according to Embodiment 4 of the present disclosure.

[0101] The solar cell 40 according to Embodiment 4 differs from the solar cell 10 according to Embodiment 1 in that the first protrusion provided on the first main surface of the electron transport layer is different. With respect to the other components except for the first protrusion, the solar cell 40 according to Embodiment 4 is the same as the solar cell 10 according to Embodiment 1.

[0102] As shown in Figure 4, in the solar cell 40 according to Embodiment 4, the first protrusion 412 included in the first main surface 410 of the electron transport layer 402 penetrates the photoelectric conversion layer 103 and the hole transport layer 104 and is in contact with the second electrode 105. That is, in the solar cell 40, the electron transport layer 402 has a first main surface 410 that is in contact with the photoelectric conversion layer 103, and the first main surface 410 includes a first flat portion 411 and a first protrusion 412 that protrudes from the first flat portion 411 and is in contact with the second electrode 105.

[0103] The electron transport layer 402, which has a first protrusion 412 that penetrates the photoelectric conversion layer 103 and the hole transport layer 104 and contacts the second electrode 105, can be formed in the same manner as the electron transport layer 102 of the solar cell 10 according to Embodiment 1. Specifically, using the electron transport layer 102 formation method described in Embodiment 1, the first protrusion 412 protruding from the first planar portion 411 should be formed to be greater than the sum of the thickness of the photoelectric conversion layer 103 and the thickness of the hole transport layer 104. In other words, the solar cell 40 can be manufactured in the same manner as the solar cell 10 manufacturing method described in Embodiment 1.

[0104] The configuration in which the first protrusion 412 penetrates the photoelectric conversion layer 103 and the hole transport layer 104 and contacts the second electrode 105 makes it less likely for the solar cell 40 to be damaged or delamination to occur even when the solar cell 40 is pressurized by the sealing material during sealing. It also makes it less likely for cracks to occur in the photoelectric conversion layer 103. As a result, the first protrusion 412 can more effectively suppress damage such as cracks and delamination that occur during the manufacturing and sealing of the solar cell 40. Therefore, the solar cell 40 can maintain higher electrical characteristics and have higher reliability.

[0105] Although only one first protrusion 412 is shown in Figure 4, multiple first protrusions 412 may be included on the first main surface 410 of the electron transport layer 402. In other words, multiple first protrusions 412 may be formed in the solar cell 40. The number and placement of the first protrusions 412 are not particularly limited.

[0106] Although Figure 4 shows an example where the first protrusion 412 in contact with the hole transport layer 104 is columnar, the shape of the first protrusion 412 may be spherical, as described in Embodiment 2.

[0107] The height range of the first protrusion 412 from the first flat portion 411 may be the same as the height range of the first protrusion 112 from the first flat portion 111 in the solar cell 10 described in Embodiment 1.

[0108] As a modification of the solar cell 40 according to Embodiment 4, a configuration is provided in which the first protrusion 412, which penetrates the photoelectric conversion layer 103 and the hole transport layer 104, is in contact with the second electrode 105 via another layer. For example, a cover layer may be provided on the top of the first protrusion 412, and the first protrusion 412 may be in contact with the second electrode 105 via the cover layer. By configuring the solar cell 40 so that the first protrusion 412 and the second electrode 105 are not in direct contact, the electrical characteristics of the solar cell 40 can be improved. The material used for the cover layer may be, for example, MoO y This can be used. Here, 0 < y and 2 ≤ y ≤ 3 may also be applicable.

[0109] (Embodiment 5) Figure 5 shows a cross-sectional view of a solar cell 50 according to one embodiment of the present disclosure.

[0110] The solar cell 50 according to Embodiment 5 differs from the solar cell 20 according to Embodiment 2 in that it has a different photoelectric conversion layer. Aside from the photoelectric conversion layer, the solar cell 50 according to Embodiment 5 is the same as the solar cell 20 according to Embodiment 2.

[0111] As shown in Figure 5, the photoelectric conversion layer 503 has a second main surface 510 opposite to the surface in contact with the first main surface 210 of the electron transport layer 202. In the configuration shown in Figure 5, the second main surface 510 of the photoelectric conversion layer 503 is the surface in contact with the hole transport layer 104 in the photoelectric conversion layer 503. The photoelectric conversion layer 503 is formed to follow the shape of the first main surface 210 of the electron transport layer 202, and the second main surface 510 has a second protrusion 512 at a position corresponding to the first protrusion 212 of the first main surface 210. That is, the second main surface 510 of the photoelectric conversion layer 503 has a second flat surface 511 and a second protrusion 512 at positions corresponding to the first flat surface 211 and the first protrusion 212 of the first main surface 210, respectively.

[0112] In the solar cell 50, the photoelectric conversion layer 503 may have, for example, a second protrusion 512 that protrudes from the second planar portion 511 in the same manner as the protrusion axis 130 of the first protrusion 212 included in the first main surface 210. Note that the statement that the second protrusion 512 protrudes in the same manner as the protrusion axis 130 of the first protrusion 212 is not limited to the protrusion axis of the second protrusion 512 perfectly coinciding with the protrusion axis 130 of the first protrusion 212. For example, it is sufficient if the distance between the protrusion axis of the second protrusion 512 and the protrusion axis 130 of the first protrusion 212 is less than or equal to the radius of the first protrusion 212, or if the protrusion axis of the second protrusion 512 is contained within the first protrusion 212. In this specification, the protrusion axis of a protrusion refers to a vertical line passing through the center of the circle inscribed in the protrusion when viewed from the main surface.

[0113] Aside from the features of the second main surface 510, the second flat portion 511, and the second protrusion 512 described above, the other configurations of the photoelectric conversion layer 503 are the same as those of the photoelectric conversion layer 103 described in Embodiment 1.

[0114] The solar cell 50 can be formed in the same manner as the solar cell 20 according to Embodiment 2. For example, a method such as inkjet coating or spray coating may be used so that the photoelectric conversion layer 503 conforms to the shape of the first main surface 210 of the electron transport layer 202.

[0115] Although Figure 5 shows an example where the first protrusion 212 is spherical, the shape of the first protrusion 212 may also be columnar, as described in Embodiment 1 for the first protrusion 112.

[0116] (Embodiment 6) Figure 6 shows a cross-sectional view of a solar cell 60 according to one embodiment of the present disclosure.

[0117] The solar cell 60 according to Embodiment 6 differs from the solar cell 50 according to Embodiment 5 in that it has a different hole transport layer. Aside from the hole transport layer, the solar cell 60 according to Embodiment 6 is the same as the solar cell 50 according to Embodiment 5.

[0118] As shown in Figure 6, the hole transport layer 604 has a third main surface 610 that is in contact with the second electrode 105. The hole transport layer 604 is formed to follow the shape of the first main surface 210 of the electron transport layer 202, and the third main surface 610 has a third protrusion 612 at a position corresponding to the first protrusion 212 of the first main surface 210. That is, the third main surface 610 of the hole transport layer 604 has a third flat surface 611 and a third protrusion 612 at positions corresponding to the first flat surface 211 and the first protrusion 212 of the first main surface 210, respectively.

[0119] In the solar cell 60, the hole transport layer 604 may have, for example, a third protrusion 612 that protrudes from the third planar portion 611 in the same manner as the protruding axis 130 of the first protrusion 212 included in the first main surface 210. Note that the statement that the third protrusion 612 protrudes in the same manner as the protruding axis 130 of the first protrusion 212 is not limited to the protruding axis of the third protrusion 612 perfectly coinciding with the protruding axis 130 of the first protrusion 212. For example, it is sufficient if the distance between the protruding axis of the third protrusion 612 and the protruding axis 130 of the first protrusion 212 is less than or equal to the radius of the first protrusion 212, or if the protruding axis of the third protrusion 612 is included inside the first protrusion 212.

[0120] Aside from the features of the third main surface 610, the third flat portion 611, and the third convex portion 612 described above, the hole transport layer 604 is the same as the hole transport layer 104 described in Embodiment 1.

[0121] The solar cell 60 can be formed in the same manner as the solar cell 50 according to Embodiment 5. For example, a method such as inkjet coating or spray coating may be used so that the hole transport layer 604 conforms to the shape of the first main surface 210 of the electron transport layer 202.

[0122] Although Figure 6 shows an example where the first protrusion 212 is spherical, the shape of the first protrusion 212 may also be columnar, as described in Embodiment 1 for the first protrusion 112.

[0123] (Embodiment 7) Figure 7 shows a cross-sectional view of a solar cell 70 according to one embodiment of the present disclosure.

[0124] The solar cell 70 according to Embodiment 7 differs from the solar cell 60 according to Embodiment 6 in that the second electrode is different. With respect to the other components except for the second electrode, the solar cell 70 according to Embodiment 7 is the same as the solar cell 60 according to Embodiment 6.

[0125] As shown in Figure 7, the second electrode 705 has a fourth main surface 710 that includes the surface of the solar cell 70. The second electrode 705 is formed to follow the shape of the first main surface 210 of the electron transport layer 202, and the fourth main surface 710 has a fourth protrusion 712 at a position corresponding to the first protrusion 212 of the first main surface 210. That is, the fourth main surface 710 of the second electrode 705 has a fourth flat surface 711 and a fourth protrusion 712 at positions corresponding to the first flat surface 211 and the first protrusion 212 of the first main surface 210, respectively.

[0126] In the solar cell 70, the second electrode 705 may have, for example, a fourth protrusion 712 that protrudes from the fourth planar portion 711 in the same manner as the protruding axis 130 of the first protrusion 212 included in the first main surface 210. Note that the statement that the fourth protrusion 712 protrudes in the same manner as the protruding axis 130 of the first protrusion 212 is not limited to the protruding axis of the fourth protrusion 712 perfectly coinciding with the protruding axis 130 of the first protrusion 212. For example, it is sufficient if the distance between the protruding axis of the fourth protrusion 712 and the protruding axis 130 of the first protrusion 212 is less than or equal to the radius of the first protrusion 212, or if the protruding axis of the fourth protrusion 712 is included inside the first protrusion 212.

[0127] Aside from the features of the fourth main surface 710, the fourth flat portion 711, and the fourth convex portion 712 described above, the second electrode 705 is the same as the second electrode 105 described in Embodiment 1.

[0128] The solar cell 70 can be formed in the same manner as the solar cell 60 according to Embodiment 6. For example, a method such as inkjet coating or spray coating may be used so that the second electrode 705 conforms to the shape of the first main surface 210 of the electron transport layer 202.

[0129] Although Figure 7 shows an example where the first protrusion 212 is spherical, the shape of the first protrusion 212 may also be columnar, as described in Embodiment 1 for the first protrusion 112.

[0130] (Embodiment 8) Figure 8 shows a cross-sectional view of a solar cell 80 according to one embodiment of the present disclosure.

[0131] The solar cell 80 differs from the solar cell 70 only in that the first protrusion 212 penetrates the photoelectric conversion layer 503 and is in contact with the hole transport layer 604, and can be manufactured in the same manner as the solar cell 70.

[0132] The configuration in which the first protrusion 212 penetrates the photoelectric conversion layer 503 and contacts the hole transport layer 604 makes it less likely for the solar cell 80 to be damaged or delamination to occur even when the solar cell 80 is pressurized by a sealing material during sealing. Furthermore, cracks in the photoelectric conversion layer 503 are also less likely to occur. As a result, the first protrusion 212 can more effectively suppress damage such as cracks and delamination during the manufacturing and sealing of the solar cell 80. Therefore, the solar cell 80 can maintain higher electrical characteristics and achieve greater reliability.

[0133] Furthermore, as described above, an n-type semiconductor may be used for the electron transport layer 202, and a p-type semiconductor may be used for the hole transport layer 604. When an n-type semiconductor is used for the electron transport layer 202 and a p-type semiconductor is used for the hole transport layer 604, a pn junction is formed when the first protrusion 212 comes into contact with the hole transport layer 604. This pn junction can act as a bypass to release electricity when a large voltage is applied locally to the solar cell 80. Therefore, the solar cell 80 can maintain even higher electrical characteristics and further improve reliability.

[0134] As described above, the solar cell 80 according to Embodiment 8 can have higher performance because, in addition to suppressing damage and delamination of the solar cell 80 due to the anchoring effect of the first protrusion 212, it also benefits from the bypass effect due to the formation of a pn junction.

[0135] (Other Embodiments) (Note) The above description of embodiments discloses the following technologies.

[0136] (Technology 1) A solar cell comprising a first electrode, a first transport layer, a photoelectric conversion layer, and a second electrode in this order, wherein the first transport layer has a first main surface in contact with the photoelectric conversion layer, the first main surface includes a first planar portion and a first convex portion protruding from the first planar portion, and the first transport layer has a higher modulus of elasticity than the photoelectric conversion layer.

[0137] According to the solar cell of Technology 1, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0138] (Technical 2) The solar cell according to Technical 1, wherein the thickness of the first transport layer in the first convex portion is greater than the thickness of the first transport layer in the first planar portion.

[0139] According to the solar cell of Technology 2, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which can occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0140] (Technology 3) The solar cell according to Technology 1 or 2, wherein the first protrusion is columnar.

[0141] According to the solar cell of Technology 3, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which can occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0142] (Technical 4) The solar cell according to any one of Technical 1 to 3, wherein the first protrusion is spherical.

[0143] According to the solar cell of Technology 4, the first protrusion can be formed more easily. Therefore, damage and delamination of the solar cell, as well as defects in the photoelectric conversion layer, which may occur during the sealing of the solar cell or the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0144] (Technical 5) The photoelectric conversion layer has a second main surface opposite to the surface in contact with the first main surface of the first transport layer, the photoelectric conversion layer is formed to follow the shape of the first main surface of the first transport layer, and the second main surface has a second protrusion at a position corresponding to the first protrusion of the first main surface, according to any one of Technical 1 to 4.

[0145] According to the solar cell of Technology 5, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0146] (Technical 6) The photoelectric conversion layer has a second main surface opposite to the surface in contact with the first main surface of the first transport layer, the second main surface includes a second planar portion and a second convex portion protruding from the second planar portion, and the second convex portion protrudes from the second planar portion with the same projection axis as the first convex portion of the first main surface, the solar cell according to any one of Technical 1 to 5.

[0147] According to the solar cell of Technology 6, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0148] (Technical 7) The solar cell according to any one of Technical 1 to 6, further comprising a second transport layer disposed between the photoelectric conversion layer and the second electrode.

[0149] According to Technology 7, it is possible to provide a solar cell with excellent properties.

[0150] (Technical 8) The solar cell according to Technical 7, wherein the first protrusion is in contact with the second transport layer.

[0151] According to the solar cell of Technology 8, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which can occur during encapsulation or formation of the photoelectric conversion layer of the solar cell, can be made less likely. Furthermore, when the first transport layer is, for example, an electron transport layer and an n-type semiconductor is used for the electron transport layer, and the second transport layer is, for example, a hole transport layer and a p-type semiconductor is used for the hole transport layer, a pn junction is formed when the first protrusion comes into contact with the hole transport layer. This pn junction can act as a bypass to dissipate electricity when a large voltage is applied locally to the solar cell. Therefore, the solar cell can maintain even higher electrical characteristics and further improve reliability.

[0152] (Technical 9) The solar cell according to Technical 7 or 8, wherein the second transport layer has a third main surface in contact with the second electrode, the second transport layer is formed to follow the shape of the first main surface of the first transport layer, and the third main surface has a third protrusion at a position corresponding to the first protrusion of the first main surface.

[0153] According to the solar cell of Technology 9, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0154] (Technical 10) The solar cell according to any one of Technical 7 to 9, wherein the second transport layer has a third main surface in contact with the second electrode, the third main surface includes a third planar portion and a third convex portion protruding from the third planar portion, and the third convex portion protrudes from the third planar portion with the same projection axis as the first convex portion of the first main surface.

[0155] According to the solar cell of technology 10, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0156] (Technical 11) The solar cell according to any one of Technical 1 to 10, wherein the first protrusion is in contact with the second electrode.

[0157] According to the solar cell of Technology 11, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0158] (Technical 12) The solar cell according to any one of Technical 1 to 11, wherein the second electrode has a fourth main surface including the surface of the solar cell, the second electrode is formed to follow the shape of the first main surface of the first transport layer, and the fourth main surface has a fourth protrusion at a position corresponding to the first protrusion of the first main surface.

[0159] According to the solar cell of Technology 12, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0160] (Technical 13) The solar cell according to any one of Technical 1 to 12, wherein the second electrode has a fourth main surface including the surface of the solar cell, the fourth main surface includes a fourth planar portion and a fourth convex portion protruding from the fourth planar portion, and the fourth convex portion protrudes from the fourth planar portion with the same projection axis as the first convex portion of the first main surface.

[0161] According to the solar cell of Technology 13, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0162] (Technical 14) The solar cell according to any one of Technical 1 to 13, wherein the first transport layer is an electron transport layer containing a metal oxide.

[0163] According to the solar cell of Technology 14, damage and delamination of the solar cell, as well as malfunctions of the photoelectric conversion layer, which may occur during the sealing of the solar cell or during the formation of the photoelectric conversion layer of the solar cell, can be made less likely.

[0164] (Technical 15) The solar cell according to Technical 14, wherein the first transport layer contains SnO2 as its main component.

[0165] According to the solar cell of Technology 15, a film with excellent light transmittance can be formed as the first transport layer at a low temperature that allows for the use of an organic substrate.

[0166] (Technical 16) The photoelectric conversion layer comprises a perovskite compound, as described in any one of Technical 1 to 15.

[0167] According to Technology 16, a solar cell with excellent properties can be provided.

[0168] This disclosure can be applied to solar cells, which require high reliability, and has extremely high potential for industrial use.

Claims

1. A solar cell comprising a first electrode, a first transport layer, a photoelectric conversion layer, and a second electrode in this order, wherein the first transport layer has a first main surface in contact with the photoelectric conversion layer, the first main surface includes a first planar portion and a first convex portion protruding from the first planar portion, and the first transport layer has a higher elastic modulus than the photoelectric conversion layer.

2. The solar cell according to claim 1, wherein the thickness of the first transport layer in the first convex portion is greater than the thickness of the first transport layer in the first planar portion.

3. The solar cell according to claim 1, wherein the first protrusion is columnar.

4. The solar cell according to claim 1, wherein the first protrusion is spherical.

5. The photoelectric conversion layer has a second main surface opposite to the surface in contact with the first main surface of the first transport layer, the photoelectric conversion layer is formed to follow the shape of the first main surface of the first transport layer, and the second main surface has a second protrusion at a position corresponding to the first protrusion of the first main surface, according to claim 1.

6. The photoelectric conversion layer has a second main surface opposite to the surface in contact with the first main surface of the first transport layer, the second main surface includes a second planar portion and a second convex portion protruding from the second planar portion, the second convex portion protruding from the second planar portion with the same projection axis as the first convex portion of the first main surface, the solar cell according to claim 1.

7. The solar cell according to claim 1, further comprising a second transport layer disposed between the photoelectric conversion layer and the second electrode.

8. The solar cell according to claim 7, wherein the first protrusion is in contact with the second transport layer.

9. The solar cell according to claim 7, wherein the second transport layer has a third main surface in contact with the second electrode, the second transport layer is formed to follow the shape of the first main surface of the first transport layer, and the third main surface has a third protrusion at a position corresponding to the first protrusion of the first main surface.

10. The solar cell according to claim 7, wherein the second transport layer has a third main surface in contact with the second electrode, the third main surface includes a third planar portion and a third convex portion protruding from the third planar portion, and the third convex portion protrudes from the third planar portion with the same projection axis as the first convex portion of the first main surface.

11. The solar cell according to claim 1, wherein the first protrusion is in contact with the second electrode.

12. The solar cell according to claim 1, wherein the second electrode has a fourth main surface including the surface of the solar cell, the second electrode is formed to follow the shape of the first main surface of the first transport layer, and the fourth main surface has a fourth protrusion at a position corresponding to the first protrusion of the first main surface.

13. The solar cell according to claim 1, wherein the second electrode has a fourth main surface including the surface of the solar cell, the fourth main surface includes a fourth planar portion and a fourth convex portion protruding from the fourth planar portion, and the fourth convex portion protrudes from the fourth planar portion with the same projection axis as the first convex portion of the first main surface.

14. The solar cell according to claim 1, wherein the first transport layer is an electron transport layer containing a metal oxide.

15. The solar cell according to claim 14, wherein the first transport layer contains SnO2 as its main component.

16. The solar cell according to claim 1, wherein the photoelectric conversion layer comprises a perovskite compound.

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