Method for manufacturing solar cells and solar cells

Abstract

By using a non-flowable carbon material for the second electrode layer, there is no risk of leakage even over a large area, and the invention provides a solar cell manufacturing method and solar cell with good conversion efficiency and yield. [Solution] A solar cell 100 is characterized in which a transparent substrate 10, a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, a porous insulating layer 50, and a second electrode layer 70 are stacked in this order, wherein perovskite compounds are arranged in the pores of the porous electron transport layer 40 and the porous insulating layer 50, and the second electrode layer 70 is composed of a porous self-supporting film 71 containing a carbon material.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a solar cell and a solar cell.

Background Art

[0002] In recent years, perovskite solar cells in which a perovskite compound is formed in a power generation layer have attracted attention as solar cells (for example, Patent Document 1 discloses an MPLE (multi-layer porous layered electrode layer) type perovskite solar cell).

[0003] As schematically shown in FIG. 3, the perovskite solar cell (hereinafter, also simply referred to as a solar cell) is configured by laminating a transparent substrate 10, a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, a porous insulating layer 50, and a porous carbon layer serving as a second electrode layer 70 in this order from the light-receiving side of sunlight. Titanium oxide particles 41 are used in the porous electron transport layer 40, inorganic fine particles 51 such as zirconium oxide and aluminum oxide are used in the porous insulating layer 50, carbon particles are used in the porous carbon layer serving as the second electrode layer 70, the porous electron transport layer 40, the porous insulating layer 50, and the porous carbon layer serving as the second electrode layer 70 are filled with the perovskite compound, and the portions corresponding to the porous electron transport layer 40 and the porous insulating layer 50 form the power generation layer 60.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, as shown in Figure 4, if the second electrode layer 70 is composed of fluid carbon particles 81, there was a risk that the carbon particles 81 could leak due to factors such as penetrating between inorganic fine particles 51 in the porous insulating layer 50 before the perovskite compound is filled, which could cause a decrease in conversion efficiency and yield.

[0006] Therefore, the present disclosure aims to provide a solar cell manufacturing method and a solar cell that have good conversion efficiency and yield, by constructing the second electrode layer from a porous self-supporting film containing a non-flowing carbon material, thereby eliminating the risk of leakage even over a large area. [Means for solving the problem]

[0007] To achieve the above-mentioned objectives, the solar cell according to the present disclosure is a solar cell in which a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, a porous insulating layer, and a second electrode layer are stacked in this order on a transparent substrate, wherein a perovskite compound is disposed in the pores of the porous electron transport layer and the porous insulating layer, and the second electrode layer is composed of a porous self-supporting film containing a carbon material. Furthermore, to achieve the above-mentioned objectives, the solar cell according to the present disclosure is a solar cell in which a first transparent electrode layer, a dense hole transport layer, a porous hole transport layer, a porous insulating layer, a porous electron transport layer, and a second electrode layer are stacked in this order on a transparent substrate, wherein a perovskite compound is disposed in the pores of the porous hole transport layer, the porous insulating layer, and the porous electron transport layer, and the second electrode layer is composed of a porous self-supporting film containing a carbon material.

[0008] According to the above configuration, the second electrode layer is composed of a porous, self-supporting film containing at least a carbon material, thus maintaining a stable shape. Therefore, this configuration makes it easy to achieve large-area solar cells. Furthermore, if the second electrode layer contains an ionic compound internally, excellent photoelectric conversion efficiency can be achieved.

[0009] Furthermore, with the above configuration, the risk of carbon particles constituting the second electrode layer penetrating before the perovskite compound is filled into the porous insulating layer can be avoided, thus preventing leakage. Therefore, it is possible to provide a solar cell with good conversion efficiency and yield.

[0010] Furthermore, the presence of a porous insulating layer allows for easier pattern formation of the power generation layer by retaining the precursor solution for forming the perovskite compound. The crystal growth direction of the perovskite compound can also be controlled to some extent.

[0011] Furthermore, if the solar cell has a configuration in which a transparent substrate, a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, a porous insulating layer, and a second electrode layer are stacked in this order, the second electrode layer alone can perform both the function of a hole transport layer and a current collector electrode.

[0012] Here, we will explain porous self-supporting membranes. Electrode materials such as the porous carbon layer conventionally used in the second electrode layer tend to break when peeled off, making it difficult to say that they are self-supporting.

[0013] In contrast, the porous self-supporting film used in the second electrode layer of the solar cell according to this disclosure can be said to be self-supporting because it maintains its shape as a film even when peeled off after deposition. In other words, in this disclosure, "porous self-supporting film" means a film that can be confirmed to be able to be peeled off while maintaining its shape after deposition.

[0014] A porous self-supporting membrane is a membrane in which multiple pores are formed, and after deposition, it can maintain its shape as a membrane even without a support, and when the porous self-supporting membrane is immersed in a predetermined solvent or solution and then removed and attached to a substrate, the membrane does not tear and maintains its shape as a membrane.

[0015] Furthermore, the porous self-supporting membrane used in this disclosure does not tear or deform even when, for example, chlorobenzene or other solvents that are poor for perovskite compounds are dropped onto the membrane, or when handled using jigs used for attaching the membrane. The porous self-supporting membrane used in this disclosure has, for example, a film thickness of 1 μm to 200 μm and an area of ​​1 mm². 2 ~100cm 2 At this size, it is preferable to maintain the film shape without a support.

[0016] In this disclosure, unless otherwise specified, a layer or film is not necessarily limited to having a constant thickness or width, but also includes those with varying thicknesses, patterns, or island-like structures. Preferably, a layer or film has a substantially constant thickness. Layers and films are sometimes also called sheets.

[0017] Furthermore, unless otherwise specified, "approximately" or "to a certain extent" refers to the range of manufacturing tolerances, and preferentially indicates that a variation of plus 15% and minus 15% of that value is acceptable.

[0018] In this disclosure, "porous" is also called "porous" or "mesoporous," and can be the same as or include the same. In this disclosure, "porous" means a material that can contain light-absorbing parts (for example, perovskite compounds) in its pores (which can be expressed in various ways such as air gaps, voids, holes, or holes). A porous layer may include layers that contain porous materials, such as a porous electron transport layer, a porous hole transport layer, and a porous insulating layer. Preferably, a porous electron transport layer is arranged on one side (for example, the bottom side) in the thickness direction of the porous layer, and a porous insulating layer is arranged on the opposite side (for example, the top side). When using expressions meaning "up" or "down" in relation to direction, basically, the direction from the transparent substrate toward the second transparent electrode layer in a solar cell is considered "up," and the opposite direction is considered "down," and this is understood unless otherwise specified. In some cases, the opposite direction may be used, in which case it will be described as appropriate. That is, basically, the light-receiving surface side and the bottom side mean the same thing, and the back side and the top side also mean the same thing. Furthermore, in the case of a single-sided light-receiving solar cell, the light-receiving surface refers directly to the surface on which light enters the element. However, in the case of a double-sided light-receiving solar cell, either one of the two surfaces can be considered the light-receiving surface, and if one surface is considered the light-receiving surface, the opposite surface can be considered the back surface. In other words, if the configuration of the disclosure is present when at least one of the surfaces is considered the light-receiving surface, it can be considered to fall within the technical scope of the disclosure. To put it another way, even if the configuration of the disclosure is not present when one of the surfaces is considered the light-receiving surface, if the configuration of the disclosure is present when the other surface is considered the light-receiving surface, it can be considered to fall within the technical scope of the disclosure.

[0019] In this disclosure, unless otherwise specified, "pores of a certain member" means "regions in any region where a certain member is dispersed or continuously distributed, where a certain member is not present." For example, in a cross-sectional observation image of a porous member, pores mean all parts of the cross-sectional observation image that are not the cross-section of the porous member, and include parts where non-porous members are provided. Furthermore, dense material means material with extremely small voids. In other words, in this disclosure, dense material means material in which, in observation, there can be no light-absorbing portion (in this embodiment, this is a perovskite compound, and hereafter described as a perovskite compound) on one side in the thickness direction of the dense material (for example, the lower side). That is, even if there is a perovskite compound on the upper side of the dense material, it is possible to ensure that it does not penetrate and exist on the lower side of the dense material. Preferably, dense material means material with extremely small voids. Preferably, dense material means material with a maximum void width of less than 5 nm. Preferably, the dense material is one that suppresses the penetration of perovskite compounds, so that perovskite compounds are absent on one side in the thickness direction of the dense material. More preferably, the dense material means that perovskite compounds cannot be contained in the pores, or that there are no portions in which perovskite compounds exist continuously throughout the thickness of the dense material. In other words, if the dense material cannot be confirmed at the maximum width of its voids, it is sufficient that observation by SEM or EDX shows that there are no portions in which perovskite compounds penetrate the thickness of the layer. In this disclosure, unless otherwise contradictory, observation by SEM is sufficient if it is observed and confirmed in a 400 nm wide cross-sectional SEM (or EDX) image. For example, if a single 400 nm wide cross-sectional SEM or EDX observation shows that there are no portions in which perovskite compounds penetrate the thickness of the layer, then that layer can be said to be dense material.

[0020] In this disclosure, transparency or light transmittance means the ability to transmit light, but does not exclude materials that reflect or absorb even a small amount of light. It is sufficient that the material is provided on the light-receiving side of the solar cell and can transmit light appropriately. This can be considered synonymous with being provided on the light-receiving side of the photoelectric conversion element. Therefore, a material can be considered transparent if it is provided on the light-receiving side of the photoelectric conversion element. A transparent electrode layer is simply a material that can transmit light appropriately when provided on the light-receiving surface of a solar cell. In this disclosure, the term "perovskite compound precursor solution" means a solution containing a perovskite compound precursor, but this does not exclude the presence of substances other than the perovskite compound precursor, and also includes cases where the perovskite compound itself is present. Furthermore, it does not exclude cases where some or all of the perovskite compound precursor becomes the perovskite compound and is included.

[0021] In the solar cell according to this disclosure, the perovskite compound may also be arranged in the second electrode layer, and the packing density of the perovskite compound in the second electrode layer may be smaller than the density of the perovskite compound in the porous insulating layer.

[0022] In this disclosure, unless otherwise specified, SEM observation is sufficient if it is performed and confirmed in a 400 nm wide cross-sectional SEM (and / or EDX) image. For example, the abundance of a perovskite compound shown in a single 400 nm wide cross-sectional SEM or EDX observation means the area occupied by the perovskite compound in that 400 nm wide observation image divided by the total area including the other areas. The abundance of a perovskite compound in a particular layer means the area occupied by the perovskite compound within the range of that particular layer (in this case, the height direction of the image) in a 400 nm wide observation image divided by the total area including the other areas.

[0023] To achieve the above object, a method for manufacturing a solar cell according to the present disclosure is a method for manufacturing a solar cell, comprising: a step of laminating at least a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer and a porous insulating layer in this order on a transparent substrate, or a step of laminating said first transparent electrode layer, a dense hole transport layer, a porous hole transport layer, said porous insulating layer and said porous electron transport layer in this order; a step of infiltrating a precursor solution of a perovskite compound to form a perovskite compound in the pores of said porous electron transport layer or the pores of said porous hole transport layer, and the pores of said porous insulating layer; and a step of attaching a porous self-supporting film containing at least a carbon material onto said porous insulating layer or said porous electron transport layer to form a second electrode layer.

[0024] In the method for manufacturing a solar cell according to the present disclosure, at least said first transparent electrode layer, said dense electron transport layer, said porous electron transport layer and said porous insulating layer are laminated in this order on said transparent substrate, or said first transparent electrode layer, said dense hole transport layer, said porous hole transport layer, said porous insulating layer and said porous electron transport layer are laminated in this order; thereafter, said precursor solution of the perovskite compound is infiltrated to form said perovskite compound in the pores of said porous electron transport layer or the pores of said porous hole transport layer, and the pores of said porous insulating layer; thereafter, said porous self-supporting film containing at least said carbon material is attached onto said porous insulating layer or said porous electron transport layer to form the second electrode layer.

[0025] In the method for manufacturing a solar cell according to the present disclosure, at least the first transparent electrode layer, the dense electron transport layer, the porous electron transport layer, and the porous insulating layer are laminated in this order on the transparent substrate, or the first transparent electrode layer, the dense hole transport layer, the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are laminated in this order; thereafter, the porous self-supporting film containing at least the carbon material is attached onto the porous insulating layer or the porous electron transport layer to form the second electrode layer; and then the precursor solution of the perovskite compound is permeated through the second electrode layer to form the perovskite compound in the pores of the porous electron transport layer or the pores of the porous hole transport layer, and the pores of the porous insulating layer.

[0026] In the method for manufacturing a solar cell according to the present disclosure, at least the first transparent electrode layer, the dense electron transport layer, the porous electron transport layer, and the porous insulating layer are laminated in this order on the transparent substrate, or the first transparent electrode layer, the dense hole transport layer, the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are laminated in this order; thereafter, the porous self-supporting film containing at least the carbon material and impregnated with the precursor solution of the perovskite compound is attached onto the porous insulating layer or the porous electron transport layer to form the second electrode layer; and then the precursor solution of the perovskite compound is permeated through the second electrode layer to form the perovskite compound in the pores of the porous electron transport layer or the pores of the porous hole transport layer, and the pores of the porous insulating layer. [Effects of the Invention]

[0027] According to the present disclosure, since a non-flowable carbon material is used for the second electrode layer, there is no risk of leakage even when the solar cell has a large area, whereby a solar cell and a method for manufacturing a solar cell with favorable conversion efficiency and yield can be provided. [Brief Description of the Drawings]

[0028] [Figure 1]Figure 1 is a schematic cross-sectional view showing the configuration of the solar cell according to this disclosure. [Figure 2] Figure 2 is an explanatory diagram of the porous insulating layer and the second electrode layer of the solar cell according to this disclosure. [Figure 3] Figure 3 is a schematic cross-sectional view showing the configuration of a conventional solar cell. [Figure 4] Figure 4 is an explanatory diagram of the porous insulating layer and second electrode layer of a conventional solar cell. [Modes for carrying out the invention]

[0029] The embodiments of the solar cell relating to this disclosure will be described below with reference to the figures. In the following description, unless otherwise specified, the same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0030] [Solar Cells] Figure 1 is a schematic cross-sectional view of a solar cell 100 according to this embodiment. The solar cell 100 is constructed by sequentially stacking a first transparent electrode layer 20, a dense electron transport layer 30, a power generation layer 60 comprising a porous electron transport layer 40 and a porous insulating layer 50, and a second electrode layer 70 on a transparent substrate 10. Perovskite compounds are present in the pores of the porous electron transport layer 40 and the porous insulating layer 50. It is preferable that perovskite compounds are present on the porous surface of the pores of the power generation layer 60. In the solar cell 100, the first transparent electrode layer 20 becomes the negative electrode, and the second electrode layer 70 becomes the anode. The second electrode layer 70 consists of a porous self-supporting film 71 containing at least a carbon material. The porous self-supporting film 71 may contain ionic compounds or the like internally.

[0031] The power generation layer 60 has pores inside, and for example, when a precursor solution of a perovskite compound is dropped into it, it penetrates into the interior. Therefore, the precursor solution fills the pores of the porous electron transport layer 40 and the porous insulating layer 50.

[0032] Since the solar cell 60 is formed by impregnating a precursor solution of a perovskite compound into the pores of the porous electron transport layer 40 and the porous insulating layer 50 and crystallizing it, the thickness of the power generation layer 60 can be easily controlled. Furthermore, this structure has the effect of suppressing local current leakage between the first transparent electrode layer 20 and the second electrode layer 70 formed on the transparent substrate 10. Therefore, the solar cell 100 according to this disclosure is suitable for use in large-area solar cell modules.

[0033] The following describes each component of the solar cell 100 in order.

[0034] [Transparent base] The transparent substrate 10 may be hard and rigid, or it may be flexible and have low rigidity. Examples of the shape of the transparent substrate 10 include a flat plate, a sheet, or a cylindrical shape. The transparent substrate 10 only needs to be translucent, and the transparent substrate 10 may be composed of, for example, translucent glass or resin. Examples of glass include soda-lime glass and alkali-free glass. Examples of resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyamideimide (PAI), and polyethylene naphthalate (PEN).

[0035] The thickness of the transparent substrate 10 is not particularly limited and should be any thickness that allows it to maintain its shape as a substrate for the solar cell 100. For example, the thickness of the transparent substrate 10 can be between 0.1 mm and 10 mm.

[0036] [First transparent electrode layer (negative electrode)] The first transparent electrode layer 20, which serves as the negative electrode, is a conductive and light-transmitting layer. The first transparent electrode layer 20 is deposited on the transparent substrate 10 by known deposition methods such as sputtering or chemical vapor deposition (CVD).

[0037] Examples of materials constituting the first transparent electrode layer 20 include copper iodide (CuI), indium tin oxide (ITO), tin oxide (SnO2), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). Examples of opaque conductive materials include sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, aluminum-aluminum oxide mixture (Al / Al2O3), and aluminum-lithium fluoride mixture (Al / LiF). These may be used individually or in combination of two or more types.

[0038] The thickness of the first transparent electrode layer 20 is not particularly limited and can be any thickness that allows it to exhibit the desired properties (e.g., electron transportability and light transmittance).

[0039] [Dense electron transport layer] The dense electron transport layer 30 is a layer that transports electrons generated in the power generation layer 60 to the first transparent electrode layer 20, which is the negative electrode. The dense electron transport layer 30 also suppresses the movement of holes generated in the power generation layer 60 to the first transparent electrode layer 20.

[0040] As long as the solar cell 100 functions as a solar cell, it is self-evident that the electron transport layer located on the electron transport side of the power generation layer 60 or on the electron transport side of the power generation layer 60 has the function of transporting electrons, and no confirmation is required. In other words, as long as the solar cell 100 functions as a solar cell, the layer located on the electron transport side of the power generation layer 60 or on the electron transport side of the power generation layer 60 is called the electron transport layer. The electron transport side can be rephrased as the negative electrode side of the solar cell 100.

[0041] The dense electron transport layer 30 is composed mainly of an electron transport material. Examples of electron transport materials include metal oxides (N-type metal oxides) such as titanium oxide, zinc oxide, indium oxide, tin oxide, aluminum oxide, and gallium oxide; and metal sulfides (N-type metal sulfides) such as tin sulfide, indium sulfide, and zinc sulfide. Components other than the electron transport material contained in the dense electron transport layer 30 include organic binder resins and plasticizers.

[0042] Because the dense electron transport layer 30 has a low porosity, the precursor solution of the perovskite compound used to form the power generation layer 60 does not easily penetrate into the interior of the dense electron transport layer 30 during the manufacturing of the solar cell 100. Therefore, by including the dense electron transport layer 30 in the solar cell 100, contact between the first transparent electrode layer 20 and the power generation layer 60 is suppressed. In addition, by including the dense electron transport layer 30 in the solar cell 100, contact between the first transparent electrode layer 20 and the second electrode layer 70, which is a factor in the decrease of electromotive force, is suppressed.

[0043] [Power generation layer] The power generation layer 60 is a layer that absorbs incident light and generates electrons and holes. The electrons generated in the power generation layer 60 move to the first transparent electrode layer 20 via the porous electron transport layer 40, and the holes move to the second electrode layer 70.

[0044] The power generation layer 60 may include a porous layer and a light-absorbing layer, and means all or part of the layer between the first transparent electrode layer 20 and the second electrode layer 70. The light-absorbing layer is often located between the first transparent electrode layer and the second electrode layer, in which case the photoelectric conversion layer is also located only between the first transparent electrode layer and the second electrode layer. However, if the first transparent electrode layer and the second electrode layer have a special shape such as being porous, the light-absorbing layer may include the region encompassing the first transparent electrode layer and the second electrode layer themselves, and in such cases, the power generation layer can include the first transparent electrode layer and the second electrode layer themselves, which constitute the portion where the light-absorbing layer is located. Even in that case, at least the power generation layer (including a part of the power generation layer) is located between the first transparent electrode layer and the second electrode layer. In other words, in all cases, a solar cell is provided with the first transparent electrode layer, the power generation layer (including a part of the power generation layer), and the second electrode layer in that order from the substrate, and this does not exclude the first transparent electrode layer and the second electrode layer themselves from being included, nor does it exclude the existence of a power generation layer in a part other than between the first transparent electrode layer and the second electrode layer. In this embodiment, the structure includes a porous layer comprising a porous electron transport layer 40 and a porous insulating layer 50, and a light-absorbing layer disposed on the porous surface of the pores of the porous layer. The light-absorbing layer can be said to be a collection of light-absorbing portions (perovskite compounds in this disclosure) disposed on the porous surface of the pores of the porous electron transport layer 40 and the porous insulating layer 50. However, the light-absorbing portion can mean a certain region or part of the light-absorbing layer. Furthermore, the light-absorbing layer can mean a collection of light-absorbing portions that exist discretely in a region in a certain direction having a thickness (which does not need to be constant). The perovskite compound will be described later.

[0045] Furthermore, the fact that the power generation layer 60 absorbs light and generates electrons and holes is self-evident as long as the solar cell 100 functions as a solar cell, and does not require verification. As long as it contains a material that has the function of absorbing light, it can be assumed that the power generation layer 60 absorbs light and generates electrons and holes.

[0046] [Porous electron transport layer] The porous electron transport layer 40 is a layer that transports electrons generated in the power generation layer 60 to the first transparent electrode layer 20, which is the negative electrode.

[0047] As long as the solar cell 100 functions as a solar cell, it is self-evident that the electron transport layer located on the electron transport side of the power generation layer 60 or on the electron transport side of the power generation layer 60 has the function of transporting electrons, and no confirmation is required. In other words, as long as the solar cell 100 functions as a solar cell, the layer located on the electron transport side of the power generation layer 60 or on the electron transport side of the power generation layer 60 is called the electron transport layer. The electron transport side can be rephrased as the negative electrode side of the solar cell 100.

[0048] The porous electron transport layer 40 is composed mainly of an electron transport material. Examples of electron transport materials include metal oxides (N-type metal oxides) such as titanium oxide, zinc oxide, indium oxide, tin oxide, aluminum oxide, and gallium oxide; and metal sulfides (N-type metal sulfides) such as tin sulfide, indium sulfide, and zinc sulfide. Other components that the porous electron transport layer 40 may contain include organic binder resins and plasticizers. Preferably, the porous electron transport layer 40 is composed of metal oxide particles.

[0049] Examples of the structure of the porous electron transport layer 40 include a structure in which multiple electron transport material particles are bonded together by an organic binder resin, and a structure in which multiple electron transport material particles are molded or sintered.

[0050] Because the porous electron transport layer 40 has a high porosity, the precursor solution of the perovskite compound used to form the power generation layer 60 during the manufacturing of the solar cell 100 easily penetrates into the pores of the porous electron transport layer 40. As a result, crystals of the perovskite compound are formed within the pores of the porous electron transport layer 40, forming a composite layer composed of the perovskite compound and the porous electron transport layer 40. This increases the contact area between the perovskite compound and the porous electron transport layer 40, allowing electrons generated by photoexcitation in the perovskite compound to be efficiently transferred to the porous electron transport layer 40, while blocking holes generated by photoexcitation from moving to the porous electron transport layer 40.

[0051] [Porous insulating layer] Next, the porous insulating layer 50 will be described. The porous insulating layer 50 is a porous layer composed of, for example, inorganic fine particles 51 of an insulating material. By including the porous insulating layer 50, the solar cell 100 according to this disclosure can prevent contact between the porous electron transport layer 40 and the second electrode layer 70, thereby suppressing the generation of short-circuit current. Furthermore, by adding the porous insulating layer 50, the distance between the first transparent electrode layer 20 and the dense electron transport layer 30 and the second electrode layer 70 can be increased, suppressing physical contact between the materials on both sides, and preventing the recombination of electrons and holes generated in the power generation layer 60.

[0052] The porous insulating layer 50 is mainly composed of an insulating material or a high-resistance semiconductor material. Examples of insulating materials or high-resistance semiconductor materials include metal oxides containing titanium oxide, zirconium dioxide, or aluminum oxide, and oxides containing silicon dioxide. Components other than insulating materials and high-resistance semiconductor materials that the porous insulating layer 50 may contain include organic binder resins and plasticizers. Preferably, the porous insulating layer 50 is composed of metal oxide particles.

[0053] Examples of the structure of the porous insulating layer 50 include a structure in which multiple insulating material particles or high-resistance semiconductor material particles are bonded together by an organic binder resin, and a structure in which multiple insulating material particles or high-resistance semiconductor material particles are molded or sintered.

[0054] Furthermore, by controlling the crystal growth direction when growing the perovskite compound within the pores of the porous insulating layer 50, it is possible to reduce defects and ensure uniformity of the crystal orientation. As a result, a high-quality and reliable power generation layer 60 can be obtained. In addition, when manufacturing the solar cell 100, the presence of a thick porous insulating layer 50 allows for the retention of the perovskite compound precursor solution, making pattern formation easier.

[0055] Crystals of perovskite compounds are formed within the pores of these porous electron transport layer 40 and porous insulating layer 50, constituting the power generation layer 60.

[0056] Returning to the description of the power generation layer 60, the perovskite compound included in the power generation layer 60 is not particularly limited, and any known perovskite compound can be used.

[0057] Perovskite compounds are compounds represented by the general formula ABX3. While the composition ratio of A, B, and X is preferably 1:1:3, it is not necessarily 1:1:3, and the content of each element may be adjusted as appropriate.

[0058] Furthermore, it is not necessary for each constituent element to be of only one type. As long as the power generation layer 60 has a photoelectric conversion function, the perovskite compound contained in the power generation layer 60 is exhibiting that photoelectric conversion function. Therefore, it is reasonable to assume that it is exhibiting that function even if it has the degree of freedom in composition as described in terms of composition ratio and types of constituent elements.

[0059] In general formula (1), A is an organic molecule (containing an organic group or an organic cation, as is the case in this disclosure) or an inorganic atom or molecule (containing an inorganic group or an inorganic cation, as is the case in this disclosure) or a combination thereof; B is a metal atom or molecule (containing a metal cation, as is the case in this disclosure); and X is a halogen atom or molecule or a chalcogen atom or molecule (containing a halogen anion or a chalcogen anion, as is the case in this disclosure).

[0060] In general formula (1), the three X's may be the same or different from each other. As long as the solar cell 100 has a photoelectric conversion function, the light-absorbing material that forms the perovskite compound contained in the power generation layer 60 is exhibiting a photoelectric conversion function, and this should be taken into consideration. That is, if it can be confirmed that the light-absorbing material that forms the perovskite compound has A, B, and X, it is reasonable to consider it as a light-absorbing material that forms a perovskite compound that exhibits a photoelectric conversion function, for example, if it can be found to have organic molecules, metal atoms, and halogen atoms.

[0061] Furthermore, the presence of a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the solar cell 100 has a photoelectric conversion function. For example, as organic molecules, molecules containing carbon, nitrogen, and hydrogen are preferred, and therefore, it is sufficient if carbon, nitrogen, hydrogen, metallic elements, and halogens or chalcogens are detected. Alternatively, a light-absorbing material that forms a perovskite compound only needs to contain A, B, and X, for example, it is sufficient if it is found to contain inorganic atoms, metallic atoms, and halogen atoms.

[0062] Furthermore, the presence of a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the solar cell 100 has a photoelectric conversion function. For example, cesium or rubidium are preferred as inorganic atoms, and therefore, it is sufficient if cesium or rubidium, a metallic element, and a halogen or chalcogen are detected. Also, the presence of a crystalline structure is not required, as it is a natural consequence that the solar cell 100 has a photoelectric conversion function, and therefore confirmation of the presence of a crystalline structure is not necessary. The power generation layer 60 may contain materials other than the perovskite compound.

[0063] For example, it is preferable that A is at least one alkylamine or alkali element, B is at least one lead, tin, or germanium, and X is at least one iodine, bromine, or chlorine, or that A is an alkali element, B is at least one lead, tin, or germanium, and X is at least one iodine, bromine, or chlorine.

[0064] The method for preparing the precursor solution containing the light-absorbing material that forms the perovskite compound is not particularly limited, but for example, it can be prepared by mixing the AX solution and the BX2 solution.

[0065] [Second electrode layer] The second electrode layer 70, which acts as the positive electrode, is a layer that transports holes generated in the power generation layer 60. It is clear that, as long as the solar cell 100 functions as a solar cell, any layer located on the hole-transporting side of the power generation layer 60, or on the hole-transporting side of the power generation layer 60, has the function of transporting holes, and therefore no confirmation is required. In other words, as long as the solar cell 100 functions as a solar cell, any layer located on the hole-transporting side of the power generation layer 60, or on the hole-transporting side of the power generation layer 60, can be called a "hole-transporting layer." The hole-transporting side can be rephrased as the positive electrode side of the solar cell 100.

[0066] The second electrode layer 70 is composed of a porous self-supporting membrane 71. Here, the porous self-supporting membrane 71 is a membrane made of at least a carbon material. By using a porous self-supporting membrane 71 containing a carbon material, the second electrode layer 70 can be given excellent hole transport layer functionality and current collecting electrode functionality. Furthermore, an ionic compound may be contained inside the second electrode layer 70, in which case it is preferable that it is present at least at the interface between the power generation layer 60 and the second electrode layer 70. Note that this ionic compound may be contained not only inside the second electrode layer 70 but also inside the power generation layer 60 (for example, near the interface between the power generation layer 60 and the second electrode layer 70).

[0067] [Porous self-supporting membrane] The carbon material contained in the porous self-supporting membrane 71 preferably contains a carbon material having the following properties. For example, the carbon material contained in the porous self-supporting membrane 71 preferably has a ratio (3σ / Av) of the value obtained by multiplying the standard deviation of the diameter (σ) by 3 (3σ) to the average diameter (Av) which is greater than 0.20, more preferably greater than 0.25, even more preferably greater than 0.50, and preferably less than 0.60. If 3σ / Av is greater than 0.20 and less than 0.60, even if the amount of carbon material contained in the porous self-supporting membrane 71 is small, it is possible to impart sufficient hole transport layer function and current collecting electrode function to the second electrode layer 70.

[0068] Furthermore, the average diameter (Av) of the carbon material is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and more preferably 10 nm or less. If the average diameter (Av) of the carbon material is 0.5 nm or more, aggregation of the carbon material can be suppressed, and the dispersibility of the carbon material in the second electrode layer 70 can be improved. Also, if the average diameter (Av) of the carbon material is 15 nm or less, the second electrode layer 70 can fully perform its function as a current collecting electrode.

[0069] Furthermore, it is preferable that the carbon material exhibits an upwardly convex shape in the t-plot obtained from the adsorption isotherm. More preferably, the carbon material is one that has not undergone any opening treatment. Using a carbon material that exhibits an upwardly convex shape in the t-plot obtained from the adsorption isotherm allows for the creation of a second electrode layer 70 with superior strength.

[0070] Furthermore, the inflection point of the t-plot for the carbon material is preferably in the range satisfying 0.2 ≤ t(nm) ≤ 1.5, more preferably in the range of 0.45 ≤ t(nm) ≤ 1.5, and even more preferably in the range of 0.55 ≤ t(nm) ≤ 1.0. The measurement of the adsorption isotherm of the carbon material, the creation of the t-plot, and the analysis of the t-plot can be performed, for example, using a commercially available measuring device such as "BELSORP(registered trademark)-mini" (manufactured by Nippon Bell Co., Ltd.).

[0071] Carbon materials having the above-described properties can be efficiently manufactured, for example, by synthesizing carbon materials by chemical vapor deposition (CVD) on a substrate having a catalyst layer on its surface, by supplying raw material compounds and a carrier gas, and dramatically improving the catalytic activity of the catalyst layer by introducing a small amount of oxidizing agent (catalyst activator) into the system (Supergrowth method; see International Publication No. 2006 / 011655), and by forming the catalyst layer on the substrate surface by a wet process.

[0072] In particular, from the viewpoint of easily obtaining a porous, self-supporting film 71 with a large film thickness, it is preferable to use a carbon material obtained by the super-growth method as the carbon material.

[0073] Furthermore, the porous self-supporting membrane 71 may contain the material constituting the power generation layer 60 (e.g., a perovskite compound) within its interior. More specifically, the porous self-supporting membrane 71 may contain the material constituting the power generation layer 60 (e.g., a perovskite compound) within its multiple pores.

[0074] The proportion of carbon material contained in the porous self-supporting membrane 71 is not particularly limited, but is preferably 50% by mass or more, and more preferably 75% by mass or more.

[0075] Furthermore, materials other than carbon materials that may be optionally included in the porous self-supporting film 71 include, for example, organic materials and inorganic materials as p-type semiconductors, and fibrous carbon nanostructures other than carbon materials.

[0076] Examples of organic materials that may be included in the porous self-supporting membrane 71 include 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-MeOTAD), poly(3-hexylthiophene) (P3HT), and polytrialylamine (PTAA).

[0077] Furthermore, examples of inorganic materials that may be included in the porous self-supporting membrane 71 include CuI, CuSCN, CuO, and Cu2O.

[0078] The thickness of the porous self-supporting membrane 71 is usually preferably 20 μm or more, more preferably 30 μm or more, preferably 200 μm or less, and more preferably 80 μm or less. If the thickness of the porous self-supporting membrane 71 is 20 μm or more and 200 μm or less, the second electrode layer 70 can exhibit a better function as a current collecting electrode.

[0079] [Method for manufacturing porous self-supporting membranes] The method for producing the porous self-supporting membrane 71 is not particularly limited, and for example, a method can be employed that includes a step of removing the solvent from a dispersion of fibrous carbon nanostructures containing at least a carbon material, a dispersant, and a solvent to form a porous self-supporting membrane 71 (film formation step). Furthermore, the method for producing the porous self-supporting membrane 71 may optionally include a step of preparing the dispersion of fibrous carbon nanostructures by dispersing a crude dispersion containing at least a carbon material, a dispersant, and a solvent before the film formation step (dispersion preparation step).

[0080] In the dispersion preparation step described above, it is preferable to prepare a fibrous carbon nanostructure dispersion by subjecting a crude dispersion containing at least a fibrous carbon nanostructure containing carbon material, a dispersant, and a solvent to a dispersion treatment that provides a cavitation effect or a deburring effect, although this treatment is not particularly limited and will be described in more detail later, to disperse the fibrous carbon nanostructure containing carbon material. By performing a dispersion treatment that provides a cavitation effect or a deburring effect in this way, a fibrous carbon nanostructure dispersion in which the fibrous carbon nanostructure containing carbon material is well dispersed can be obtained. Then, by fabricating a porous self-supporting membrane 71 using the fibrous carbon nanostructure in which the carbon material is well dispersed, a porous self-supporting membrane 71 can be obtained in which the carbon material is uniformly dispersed and which has excellent properties such as conductivity, thermal conductivity, and mechanical properties. Note that the fibrous carbon nanostructure dispersion used in the production of the porous self-supporting membrane 71 may also be prepared by dispersing the fibrous carbon nanostructure containing carbon material in a solvent using a known dispersion treatment other than those described above.

[0081] The fibrous carbon nanostructures used in preparing the dispersion of fibrous carbon nanostructures only need to contain at least a carbon material, and may be, for example, a mixture of a carbon material and a fibrous carbon nanostructure other than a carbon material (e.g., a multilayer carbon material).

[0082] Here, the dispersion of fibrous carbon nanostructures can have a content ratio of carbon material to fibrous carbon nanostructures other than carbon material, for example, 50 / 50 to 75 / 25 by mass ratio (carbon material / fibrous carbon nanostructures other than carbon material).

[0083] The dispersant used in preparing the fibrous carbon nanostructure dispersion is not particularly limited, as long as it can disperse fibrous carbon nanostructures containing at least carbon material and is soluble in the solvent used in preparing the fibrous carbon nanostructure dispersion. For example, surfactants, synthetic polymers, or natural polymers can be used as such dispersants.

[0084] Examples of surfactants include sodium dodecyl sulfonate, sodium deoxycholate, sodium cholate, and sodium dodecylbenzenesulfonate.

[0085] Examples of synthetic polymers include polyetherdiols, polyesterdiols, polycarbonatediols, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymers, ethylene-vinyl alcohol-vinyl acetate copolymer resins, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resins, epoxy resins, modified epoxy resins, phenoxy resins, modified phenoxy resins, phenoxy ether resins, phenoxy ester resins, fluorine resins, melamine resins, alkyd resins, phenolic resins, polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.

[0086] Furthermore, examples of natural polymers include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, cellulose, and their salts or derivatives. Derivatives refer to conventionally known compounds such as esters and ethers.

[0087] These dispersants can be used individually or in combination of two or more. Among them, surfactants are preferred as dispersants because they exhibit excellent dispersibility of fibrous carbon nanostructures containing carbon materials, and sodium deoxycholate is more preferred.

[0088] The solvent for the fibrous carbon nanostructure dispersion is not particularly limited and includes, for example, water, methanol, ethanol, alcohols such as n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane, and tetrahydrofuran; amide-based polar organic solvents such as N,N-dimethylformamide and N-methylpyrrolidone; and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene. These may be used individually or in combination of two or more.

[0089] Furthermore, in the dispersion preparation step, it is preferable to perform a dispersion treatment that yields, for example, the cavitation effect or disintegration effect shown below.

[0090] The dispersion process that achieves the cavitation effect utilizes shock waves generated when vacuum bubbles in a liquid burst after high energy is applied to the liquid. By using this dispersion method, carbon materials can be dispersed effectively.

[0091] Here, specific examples of dispersion treatments that yield a cavitation effect include ultrasonic dispersion, jet mill dispersion, and high-shear stirring dispersion. These dispersion treatments may be performed individually or in combination. More specifically, for example, an ultrasonic homogenizer, a jet mill, and a high-shear stirring device are preferably used. Conventional known devices may be used for these purposes.

[0092] When using an ultrasonic homogenizer to disperse carbon materials, the crude dispersion should be irradiated with ultrasound using the ultrasonic homogenizer. The irradiation time should be set appropriately depending on the amount of carbon material, for example, 3 minutes or more is preferred, 30 minutes or more is more preferred, 5 hours or less is preferred, and 2 hours or less is even more preferred. Also, for example, the output is preferably 20W to 500W, more preferably 100W to 500W, and the temperature is preferably 15°C to 50°C.

[0093] Furthermore, when using a jet mill, the number of processing cycles can be appropriately set depending on the amount of carbon material, for example, two or more cycles are preferable, five or more cycles are more preferable, 100 or fewer cycles are preferable, and 50 or fewer cycles are more preferable. Also, for example, the pressure is preferably 20 MPa to 250 MPa, and the temperature is preferably 15°C to 50°C.

[0094] Furthermore, when using high-shear stirring, the crude dispersion can be stirred and sheared using a high-shear stirring device. The faster the swirling speed, the better. For example, the operating time (the time the machine is rotating) is preferably 3 minutes to 4 hours, the peripheral speed is preferably 5 m / sec to 50 m / sec, and the temperature is preferably 15°C to 50°C.

[0095] Furthermore, the dispersion treatment that yields the cavitation effect described above is more preferably carried out at a temperature of 50°C or lower, because this suppresses concentration changes due to solvent volatilization.

[0096] Dispersion treatments that achieve a disintegration effect are advantageous not only because they allow for uniform dispersion of carbon materials in the solvent, but also because they can suppress damage to the carbon materials caused by shock waves when bubbles disappear, compared to the dispersion treatments that achieve the cavitation effect described above.

[0097] In this dispersion process, which achieves this disintegration effect, shear force is applied to the crude dispersion to disintegrate and disperse aggregates of fibrous carbon nanostructures containing carbon material. Furthermore, back pressure is applied to the crude dispersion, and if necessary, the crude dispersion is cooled, thereby suppressing the generation of bubbles while uniformly dispersing the carbon material in the solvent.

[0098] When applying back pressure to a crude dispersion, the back pressure applied to the crude dispersion may be reduced all at once to atmospheric pressure, but it is preferable to reduce the pressure in multiple stages.

[0099] In the film formation process, the solvent is removed from the fibrous carbon nanostructure dispersion described above to form a porous self-supporting film 71. Specifically, in the film formation process, the solvent is removed from the fibrous carbon nanostructure dispersion using either of the following methods (A) or (B) to form a porous self-supporting film 71. (A) A method of coating a fibrous carbon nanostructure dispersion onto a film-forming substrate, and then drying the coated fibrous carbon nanostructure dispersion. (B) A method of filtering a dispersion of fibrous carbon nanostructures using a porous film-forming substrate and drying the resulting filtrate.

[0100] Here, the film-forming substrate is not particularly limited, and any known substrate can be used.

[0101] Specifically, examples of film-forming substrates to which the fibrous carbon nanostructure dispersion is coated in the above method (A) include resin substrates and glass substrates. Here, examples of resin substrates include those made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, polymethyl methacrylate, alicyclic acrylic resin, cycloolefin resin, and triacetylcellulose. Examples of glass substrates include those made of ordinary soda glass.

[0102] Furthermore, examples of film-forming substrates for filtering the fibrous carbon nanostructure dispersion in the above method (B) include filter paper and porous sheets made of cellulose, nitrocellulose, alumina, etc.

[0103] In the above method (A), known coating methods can be used for coating the fibrous carbon nanostructure dispersion onto the film-forming substrate. Specifically, coating methods such as dipping, roll coating, gravure coating, knife coating, air knife coating, roll knife coating, die coating, screen printing, spray coating, and gravure offset can be used.

[0104] In method (B) described above, known filtration methods can be used to filter the dispersion of fibrous carbon nanostructures using a film-forming substrate. Specifically, filtration methods such as natural filtration, reduced pressure filtration, pressure filtration, and centrifugal filtration can be used.

[0105] In method (A) above, a known drying method can be used to dry the fibrous carbon nanostructure dispersion applied to the film-forming substrate or the filtrate obtained in method (B) above. Examples of drying methods include hot air drying, vacuum drying, hot roll drying, and infrared irradiation. The drying temperature is not particularly limited, but is usually between room temperature and 200°C, and the drying time is not particularly limited, but is usually between 0.1 and 150 minutes.

[0106] [Post-treatment of porous self-supporting membrane 71] Here, the porous self-supporting film 71 formed as described above typically contains components that were present in the fibrous carbon nanostructure dispersion, such as carbon material, fibrous carbon nanostructures other than carbon material, and dispersants, in the same proportions as the fibrous carbon nanostructure dispersion. Therefore, in the method for manufacturing the porous self-supporting film 71, the porous self-supporting film 71 formed in the film formation step may optionally be washed to remove the dispersant from the porous self-supporting film 71. Removing the dispersant from the porous self-supporting film 71 can further enhance its properties, such as conductivity.

[0107] The porous self-supporting membrane 71 can be cleaned by contacting it with a solvent capable of dissolving the dispersant, thereby eluting the dispersant in the porous self-supporting membrane 71 into the solvent. The solvent capable of dissolving the dispersant in the porous self-supporting membrane 71 is not particularly limited, and the aforementioned solvents that can be used as solvents for fibrous carbon nanostructure dispersions, preferably the same solvent as the fibrous carbon nanostructure dispersion, can be used. Contact between the porous self-supporting membrane 71 and the solvent can be performed by immersing the porous self-supporting membrane 71 in the solvent or by applying the solvent to the porous self-supporting membrane 71. Furthermore, the porous self-supporting membrane 71 after cleaning can be dried using known methods.

[0108] Furthermore, when manufacturing the porous self-supporting membrane 71, the voids may be adjusted as needed, for example, by pressing the porous self-supporting membrane 71 formed in the film formation process to further increase its density. From the viewpoint of suppressing the deterioration of properties due to damage or fracture of the carbon material, the pressing pressure during pressing is preferably less than 3 MPa, and it is even more preferable not to perform pressing.

[0109] [Ionic compounds] When an ionic compound is included inside the second electrode layer 70, the ionic compound is not particularly limited, and known ionic compounds can be used. Specifically, as the cation constituting the ionic compound, for example, metal cations, organic cations, etc., can be used. These may be used individually or in combination of two or more types. Among these, the inclusion of metal cations is preferable.

[0110] The cations constituting the ionic compound are not particularly limited and include, for example, metal cations such as lithium ions, sodium ions, and potassium ions, and organic cations such as guanidinium ions. These may be used individually or in combination of two or more. The anions constituting the ionic compound are not particularly limited and include, for example, imide ions such as bis(trifluoromethanesulfonyl)imide ions and bis(fluorosulfonyl)imide ions, halogen ions such as fluoride ions and chloride ions. These may be used individually or in combination of two or more.

[0111] The ionic compounds are not particularly limited and include, for example, lithium salts such as lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide, and sodium salts such as sodium bis(trifluoromethanesulfonyl)imide and sodium bis(fluorosulfonyl)imide. These may be used individually or in combination of two or more types.

[0112] In the solar cell 100 according to this disclosure, the functions of a hole transport layer and a current collector can be performed by a single second electrode layer 70. Furthermore, since the second electrode layer 70 is composed of a porous self-supporting film 71 containing at least a carbon material, its shape is stable. Therefore, with this configuration, it is possible to easily realize the large-area production of solar cells.

[0113] Furthermore, the solar cell 100 of this disclosure is an integrated laminate in which the order of the above-described components is maintained, and as long as the second conductive layer consists of a porous self-supporting film 71 containing at least a carbon material and contains an ionic compound inside, it may further include other layers, etc., to the extent that it does not impair the effects of this disclosure.

[0114] [Method of manufacturing solar cells] The manufacturing method for the solar cell 100 of this disclosure requires the steps of laminating the porous self-supporting film 71 onto the power generation layer 60 while at least one junction surface of the power generation layer 60 and the porous self-supporting film 71 holds a predetermined solvent, and applying a solution containing an ionic compound to the porous self-supporting film 71 laminated on the power generation layer 60 and drying it. The above-mentioned "junction surface" refers to the corresponding side of the power generation layer 60 and the porous self-supporting film 71. The manufacturing method for the solar cell 100 according to this disclosure will be described below.

[0115] [Preparation of the transparent substrate] In the method for manufacturing the solar cell 100 according to this disclosure, a transparent substrate 10 is prepared. The transparent substrate 10 is heated at a temperature of approximately 150°C for approximately 1 hour, thereby evaporating the moisture contained in the transparent substrate 10. After the transparent substrate 10 has been dried in this manner is cooled to room temperature, the following steps are performed.

[0116] [Formation of the first transparent electrode layer] Next, a first transparent electrode layer 20 is formed on the transparent substrate 10. The method for forming the first transparent electrode layer 20 is not particularly limited, and known methods such as sputtering and vapor deposition can be employed.

[0117] [Formation of a dense electron transport layer] Next, a dense electron transport layer 30 is formed on the first transparent electrode layer 20. The method for forming the dense electron transport layer 30 is not particularly limited, and for example, it can be formed by spraying a solution containing a material for forming an n-type semiconductor onto the first transparent electrode layer 20. Here, examples of methods for spraying fine particles include spray pyrolysis, aerosol deposition, electrostatic spraying, and cold spraying.

[0118] Furthermore, when forming the first transparent electrode layer 20 and the dense electron transport layer 30, mask patterning in the film deposition process and insulating decomposition treatment by laser scribing or the like after the formation of the first transparent electrode layer 20 and the dense electron transport layer 30 are also performed as appropriate in order to form the cell patterns necessary for module formation by cellization and cell integration. Once the first transparent electrode layer 20 and the dense electron transport layer 30 are formed, the process of forming the power generation layer 60 is then carried out.

[0119] [Formation of porous electron transport layer] Next, as shown in Figure 2, a porous electron transport layer 40 is formed on the dense electron transport layer 30. The method for forming the porous electron transport layer 40 is not particularly limited, and for example, it can be formed by coating titanium oxide particles 41 onto the dense electron transport layer 30 using known methods such as screen printing, spin coating, or bar coating.

[0120] [Formation of a porous insulating layer] Furthermore, as shown in Figure 2, a porous insulating layer 50 is formed on the porous electron transport layer 40. The method for forming the porous insulating layer 50 is not particularly limited, and for example, it can be formed by coating inorganic fine particles 51 onto the porous electron transport layer 40 using known methods such as screen printing, spin coating, or bar coating.

[0121] [Formation of a power generation layer] After the porous electron transport layer 40 and porous insulating layer 50 are formed as described above, the power generation layer 60 is formed. The method for forming the power generation layer 60 can be vacuum deposition or coating, but is not particularly limited. For example, if a precursor solution of a perovskite compound is dropped onto the porous insulating layer 50 and allowed to penetrate into the pores of the porous insulating layer 50 and the porous electron transport layer 40 and then dried, crystals of the perovskite compound will form in the pores of the porous insulating layer 50 and the porous electron transport layer 40, and the power generation layer 60 will be obtained.

[0122] Examples of perovskite compound precursors include lead iodide (PbI2) and methylammonium iodide (CH3NH3I). The solvent contained in the precursor solution is not particularly limited; for example, N,N-dimethylformamide and dimethyl sulfoxide can be used. After coating with these solutions, it is also possible to promote the precipitation of the perovskite compound using a poor solvent. In this specification, a poor solvent refers to a solvent in which the perovskite compound is substantially unchanged during the preparation process. If no visible changes in the perovskite compound, such as turbidity of the film, are observed during the preparation process, then it can be said that the compound is substantially unchanged.

[0123] Here, the concentration of the perovskite compound precursor solution can be set to an appropriate concentration depending on the solubility of the materials constituting the perovskite compound, for example, it can be set to about 0.5 M to 1.5 M.

[0124] The method for dropping the perovskite compound precursor solution onto the porous insulating layer 50 is not particularly limited, and known coating methods such as spin coating, spraying, and bar coating can be employed.

[0125] [Formation of the second electrode layer] After forming the power generation layer 60, a second electrode layer 70 is formed on top of the power generation layer 60. Specifically, the porous self-supporting membrane 71 is laminated onto the power generation layer 60 while at least one bonding surface of the power generation layer 60 and the porous self-supporting membrane 71 holds a predetermined solvent. This allows the porous self-supporting membrane 71 to be efficiently attached to the power generation layer 60.

[0126] The specified solvent is not particularly limited, and examples include poor solvents such as chlorobenzene, toluene, and anisole. By using these poor solvents, the porous self-supporting membrane 71 can be successfully attached to the power generation layer 60, which is a perovskite layer made of a perovskite compound.

[0127] Furthermore, by using a porous self-supporting membrane 71 impregnated with a predetermined solvent, the predetermined solvent can be well retained at at least one of the bonding surfaces between the power generation layer 60 and the porous self-supporting membrane 71. Here, the porous self-supporting membrane 71 impregnated with the predetermined solvent can be obtained, for example, by immersing the porous self-supporting membrane 71 in the predetermined solvent and then removing it. In this case, the immersion time is not particularly limited and can be set appropriately depending on the type of solvent used.

[0128] According to the manufacturing method described above, a solar cell 100 exhibiting excellent photoelectric conversion efficiency can be easily manufactured. However, the manufacturing method of the solar cell of the present invention is not limited to the method described above, and may include other steps besides those described above, as long as they do not impair the effects of the present invention.

[0129] As described above, perovskite compounds are arranged in the pores of at least the porous electron transport layer 40 and the porous insulating layer 50. However, the packing density of the perovskite compounds in the second electrode layer 70 is smaller than the density of the perovskite compounds in the porous insulating layer 50.

[0130] [Second Embodiment] In the above-described embodiment, the solar cell 100 was constructed by sequentially stacking a first transparent electrode layer 20, a dense electron transport layer 30, a power generation layer 60 comprising a porous electron transport layer 40 and a porous insulating layer 50, and a second electrode layer 70 on a transparent substrate 10. However, the configuration of the solar cell 100 is not limited to this.

[0131] The solar cell 100 may have a porous hole transport layer between the porous insulating layer 50 and the second electrode layer 70. That is, the solar cell 100 may be constructed by sequentially stacking a first transparent electrode layer 20, a dense electron transport layer 30, a power generation layer 60 comprising a porous electron transport layer 40, a porous insulating layer 50, and a porous hole transport layer, and a second electrode layer 70 on a transparent substrate 10. Even with such a configuration, in the manufacturing method, the formation of the second electrode layer 70 can be carried out after the power generation layer 60 comprising the porous electron transport layer 40, the porous insulating layer 50, and the porous hole transport layer has been formed.

[0132] [Third Embodiment] In the second embodiment described above, the solar cell 100 was constructed by sequentially stacking a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, a porous insulating layer 50, and the porous hole transport layer on a transparent substrate 10, and a second electrode layer 70. However, the configuration of the solar cell 100 is not limited to this.

[0133] The order in which the porous electron transport layer 40 and the porous hole transport layer are stacked in the solar cell 100 may differ. That is, the solar cell 100 may be constructed by stacking a first transparent electrode layer 20, a power generation layer 60 comprising a dense hole transport layer, a porous hole transport layer, a porous insulating layer 50, and a porous electron transport layer 40, and a second electrode layer 70 in this order on a transparent substrate 10. Even with such a configuration, in the manufacturing method, the formation of the second electrode layer 70 can be carried out after the power generation layer 60 comprising the dense hole transport layer, a porous hole transport layer, a porous insulating layer 50, and a porous electron transport layer 40 has been formed.

[0134] [Fourth Embodiment] In the first embodiment described above, the method for manufacturing the solar cell 100 was described as forming a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, and a porous insulating layer 50 in that order on a transparent substrate 10, then impregnating a precursor solution of a perovskite compound to form a perovskite compound in the porous electron transport layer 40 and the porous insulating layer 50, and then attaching a porous self-supporting film 71 containing at least a carbon material on the porous insulating layer 50 to form a second electrode layer 70. However, the method for manufacturing the solar cell 100 is not limited to this.

[0135] For example, as a method for manufacturing the solar cell 100, a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, and a porous insulating layer 50 may be stacked on a transparent substrate 10 in this order, or a first transparent electrode layer 20, a dense hole transport layer, a porous hole transport layer, a porous insulating layer 50, and a porous electron transport layer 40 may be stacked in this order, and then a porous self-supporting film 71 containing at least a carbon material may be attached to the porous insulating layer 50 or the porous electron transport layer 40 to form a second electrode layer 70, and then a precursor solution of a perovskite compound may be permeated through the second electrode layer 70 to form a perovskite compound in the pores of the porous electron transport layer 40 or the porous hole transport layer, and in the pores of the porous insulating layer 50.

[0136] [Fifth Embodiment] Furthermore, as a method for manufacturing the solar cell 100, a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, and a porous insulating layer 50 may be laminated on a transparent substrate 10 in this order, or a first transparent electrode layer 20, a dense hole transport layer, a porous hole transport layer, a porous insulating layer 50, and a porous electron transport layer 40 may be laminated in this order, and then a porous self-supporting film 71 containing at least a carbon material and impregnated with a precursor solution of a perovskite compound may be attached on the porous insulating layer 50 or the porous electron transport layer 40 to form a second electrode layer 70, and then the precursor solution of the perovskite compound may be permeated through the second electrode layer 70 to form a perovskite compound in the pores of the porous electron transport layer 40 or the pores of the porous hole transport layer and the pores of the porous insulating layer 50.

[0137] The configurations disclosed in any of the embodiments described above can be applied in combination with the configurations disclosed in other embodiments, insofar as they do not conflict with each other. Furthermore, the embodiments disclosed herein are illustrative and not limited to those disclosed herein, and can be modified as appropriate without departing from the purpose of this disclosure. [Industrial applicability]

[0138] According to this disclosure, by using a non-fluid carbon material for the second electrode layer, there is no risk of leakage even over a large area, and it is possible to provide a solar cell and a method for manufacturing a solar cell with good conversion efficiency and yield. [Explanation of symbols]

[0139] 10: Transparent base 20: First transparent electrode layer 30: Dense electron transport layer 40: Porous electron transport layer 50: Porous insulating layer 60: Power generation layer 70:Second electrode layer 71: Porous self-supporting membrane 100: Solar cell

Claims

1. A solar cell in which a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, a porous insulating layer, and a second electrode layer are stacked in this order on a transparent substrate, Perovskite compounds are arranged in the pores of the porous electron transport layer and the porous insulating layer. The solar cell is characterized in that the second electrode layer is composed of a porous, self-supporting film containing a carbon material.

2. A solar cell in which a first transparent electrode layer, a dense hole transport layer, a porous hole transport layer, a porous insulating layer, a porous electron transport layer, and a second electrode layer are stacked in this order on a transparent substrate, Perovskite compounds are arranged in the pores of the porous hole transport layer, the porous insulating layer, and the porous electron transport layer. The solar cell is characterized in that the second electrode layer is composed of a porous, self-supporting film containing a carbon material.

3. The perovskite compound is also arranged in the second electrode layer. The solar cell according to claim 1 or 2, characterized in that the packing density of the perovskite compound in the second electrode layer is smaller than the presence of the perovskite compound in the porous insulating layer.

4. A method for manufacturing solar cells, A step of laminating at least a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer and a porous insulating layer on a transparent substrate in this order, or a step of laminating the first transparent electrode layer, a dense hole transport layer, a porous hole transport layer, the porous insulating layer and the porous electron transport layer in this order. A step of permeating a perovskite compound precursor solution into the pores of the porous electron transport layer or the porous hole transport layer, and the pores of the porous insulating layer to form the perovskite compound. A method for manufacturing a solar cell, characterized by comprising the step of forming a second electrode layer by attaching a porous self-supporting film containing at least a carbon material to the porous insulating layer or the porous electron transport layer.

5. At least the first transparent electrode layer, the dense electron transport layer, the porous electron transport layer, and the porous insulating layer are laminated on the transparent substrate in this order, or the first transparent electrode layer, the dense hole transport layer, the porous hole transport layer, the porous insulating layer, the porous electron transport layer, and the second electrode layer are laminated in this order. Subsequently, the precursor solution of the perovskite compound is permeated to form the perovskite compound in the pores of the porous electron transport layer or the porous hole transport layer, and in the pores of the porous insulating layer. The method for manufacturing a solar cell according to claim 4, characterized in that the porous self-supporting film containing at least the carbon material is then attached to the porous insulating layer or the porous electron transport layer to form the second electrode layer.

6. At least the first transparent electrode layer, the dense electron transport layer, the porous electron transport layer, and the porous insulating layer are laminated on the transparent substrate in this order, or the first transparent electrode layer, the dense hole transport layer, the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are laminated in this order. Subsequently, the porous self-supporting film containing at least the carbon material is attached to the porous insulating layer or the porous electron transport layer to form the second electrode layer. The method for manufacturing a solar cell according to claim 4, characterized in that the precursor solution of the perovskite compound is then permeated through the second electrode layer to form the perovskite compound in the pores of the porous electron transport layer or the porous hole transport layer and the pores of the porous insulating layer.

7. At least the first transparent electrode layer, the dense electron transport layer, the porous electron transport layer, and the porous insulating layer are laminated on the transparent substrate in this order, or the first transparent electrode layer, the dense hole transport layer, the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are laminated in this order. Subsequently, the porous self-supporting film containing at least the carbon material and impregnated with the precursor solution of the perovskite compound is attached to the porous insulating layer or the porous electron transport layer to form the second electrode layer. The method for manufacturing a solar cell according to claim 4, characterized in that the precursor solution of the perovskite compound is then permeated through the second electrode layer to constitute the perovskite compound in the pores of the porous electron transport layer or the porous hole transport layer and the pores of the porous insulating layer.

Images