Method for manufacturing solar cells and solar cells

Abstract

To provide a method for manufacturing solar cells with high yield and high reliability in power generation, and a solar cell. [Solution] A method for manufacturing a solar cell 100, characterized in that at least a first transparent electrode layer 20, a dense electron transport layer 30, a porous electron transport layer 40, and a porous insulating layer 50 are formed on a transparent substrate 10 in this order, then a precursor solution of a perovskite compound 60 is permeated into the porous electron transport layer 40 and the porous insulating layer 50 to form a perovskite compound in the porous electron transport layer 40 and the porous insulating layer 50, and then a second transparent electrode layer 70 is formed on the porous insulating layer 50.

Description

Technical Field

[0001] The present invention 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 (multilayer porous layered electrode layer) type perovskite solar cell).

[0003] As schematically shown in Fig. 4, the perovskite solar cell (hereinafter, also simply referred to as solar cell) is configured by laminating a transparent substrate 10, a surface 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 80 serving as a back electrode layer in this order from the sunlight receiving side. Titanium oxide particles 41 are used for the porous electron transport layer 40, inorganic fine particles 51 such as zirconium oxide and aluminum oxide are used for the porous insulating layer 50, and carbon particles 81 are used for the porous carbon layer 80. The porous electron transport layer 40, the porous insulating layer 50 and the porous carbon layer 80 are filled with the perovskite compound. It should be noted that what the reference numerals in Fig. 4 for describing the conventional solar cell indicate do not necessarily coincide with what the reference numerals in Figs. 1 to 3 for describing the solar cell according to the present disclosure indicate.

[0004] Each porous layer of the conventional solar cell is obtained by printing a paste material, in which particles, an organic binder, and a high-viscosity solvent are mixed, onto a substrate by screen printing, followed by firing at a high temperature of about 200 to 500°C to evaporate the organic binder and the high-viscosity solvent. Then, a precursor solution 61 of the perovskite compound is dropped from the porous carbon layer 80 side, permeates into the porous electron transport layer 40 and the porous insulating layer 50, and after removing the solvent accompanying heating drying, the perovskite compound is filled into the porous electron transport layer 40, the porous insulating layer 50 and the porous carbon layer 80, thereby completing the solar cell.

Prior Art Literature

Patent Literature

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-523453 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in conventional solar cells as described above, a precursor solution 61 of the perovskite compound is dropped from the porous carbon layer 80 side and allowed to penetrate to the porous electron transport layer 40 and the porous insulating layer 50. After the solvent is removed by heating and drying, the perovskite compound is filled into the porous electron transport layer 40, the porous insulating layer 50 and the porous carbon layer 80. As a result, the yield is poor, and there is a risk of uneven penetration of the precursor solution within the porous electron transport layer 40 and the porous insulating layer 50.

[0007] Furthermore, when the perovskite compound within the porous carbon layer 80 deteriorated, lead iodide, an insulator, was formed, resulting in unstable power generation reliability.

[0008] Furthermore, in recent years, perovskite solar cells are sometimes used as tandem solar cells in combination with silicon solar cells. For this purpose, it is necessary to replace the porous carbon layer in the back electrode layer with a light-transmitting material.

[0009] In this process, it is necessary to form a perovskite compound on the porous insulating layer before laminating the translucent back electrode layer onto the porous insulating layer. This is because, if a translucent material is used as the back electrode layer, its high resistance prevents the perovskite compound precursor solution from being dropped and permeated into the porous electron transport layer or porous insulating layer through the back electrode layer.

[0010] However, if materials constituting the back electrode layer are to be laminated onto a porous insulating layer on which a perovskite compound has been formed by sputtering or the like, the perovskite compound formed on the porous insulating layer may be damaged, potentially negatively impacting the reliability of power generation.

[0011] This disclosure is made in view of the above-mentioned problems and provides a method for manufacturing a solar cell and a solar cell that have a good yield and high reliability in power generation. [Means for solving the problem]

[0012] To achieve the above-mentioned objectives, the present disclosure is a method for manufacturing a solar cell, characterized in that at least a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, and a porous insulating layer are formed on a transparent substrate in this order, or 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 are formed in this order, then a precursor solution of a perovskite compound is permeated into the porous electron transport layer and the porous insulating layer, or the porous hole transport layer, the porous electron transport layer, and the porous insulating layer to form a perovskite compound within the porous electron transport layer and the porous insulating layer, or the porous hole transport layer, the porous insulating layer, and the porous electron transport layer, and then a second transparent electrode layer is formed on the porous insulating layer.

[0013] According to the above configuration, before forming the second transparent electrode layer, a precursor solution of the perovskite compound is permeated into the porous electron transport layer and the porous insulating layer, or the porous hole transport layer, the porous electron transport layer and the porous insulating layer. This allows the perovskite compound to be easily formed in every corner of the porous electron transport layer and the porous insulating layer, or in the porous hole transport layer, the porous insulating layer and the porous electron transport layer, resulting in a good yield. Each layer is laminated, for example, by screen printing.

[0014] In this disclosure, “solar cell” means a device that has the function of converting light into electricity. In this disclosure, “layer” or “film” preferably refers to a component having a substantially constant film thickness, but is not limited thereto, and may have parts of different thicknesses, and may be patterned or island-shaped.

[0015] Furthermore, unless otherwise specified, "approximately" or "to the 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.

[0016] 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 can include layers that may contain porosity, such as a porous electron transport layer, a porous hole transport layer, or a porous insulating layer. Preferably, a porous electron transport layer is located on one side (for example, the bottom) in the thickness direction of the porous layer, and a porous insulating layer is located on the opposite side (for example, the top). 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 this 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.

[0017] In this disclosure, unless otherwise specified, "pores of a certain member" means "regions in any region where a certain member is distributed dispersed or continuously, where that member is not present." For example, in a cross-sectional view of a porous member, "pores" means all parts of the cross-sectional view that are not the cross-section of the porous member, and also include parts where a non-porous member is provided. Furthermore, dense material means material with extremely small voids. In other words, in this disclosure, dense material means material in which, upon observation, there are no light-absorbing regions (in this embodiment, a perovskite compound as an example, and hereinafter 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 prevent it from penetrating and not being present 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, dense material is one that suppresses the penetration of perovskite compounds and allows for a state in which there are no perovskite compounds on one side in the thickness direction of the dense material. Even more preferably, dense material means material in which perovskite compounds cannot be contained in the pores, or material that does not have a portion in which perovskite compounds exist continuously throughout the thickness of the dense material portion. In other words, if compaction cannot be confirmed by the maximum width of its voids, it is sufficient if observation by SEM or EDX shows that there are no areas where the perovskite compound penetrates the layer thickness. In this disclosure, unless otherwise contradictory, observation by SEM is sufficient if it is confirmed by observing 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 no areas where the perovskite compound penetrates the layer thickness, then that layer can be said to be compact.

[0018] In this disclosure, transparency or light transmittance means transmitting 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 surface side of the solar cell and transmits light appropriately. This can be considered synonymous with being provided on the light-receiving surface side of the photoelectric conversion element. Therefore, a material can be considered transparent if it is provided on the light-receiving surface 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 the solar cell. In the case of a solar cell capable of receiving light on both sides, all layers placed on both light-receiving surfaces are transparent. 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.

[0019] Furthermore, since the perovskite compound precursor solution is not permeated into the second transparent electrode layer, there is no risk of lead iodide, an insulator, forming, as is the case with solar cells obtained by conventional manufacturing methods, resulting in high reliability of power generation.

[0020] Furthermore, by controlling the growth direction when growing perovskite compounds within the pores of a porous insulating layer, defects can be reduced and uniformity can be ensured. As a result, a high-quality and reliable perovskite layer can be obtained. In addition, when manufacturing solar cells, the presence of a thick porous insulating layer allows for the retention of the perovskite compound precursor solution, making pattern formation easier.

[0021] Because the second transparent electrode layer of this solar cell is light-transmitting, it is possible to combine solar cells with different band gaps (for example, this solar cell and a silicon solar cell) to create a tandem solar cell.

[0022] In this disclosure, the second transparent electrode layer can also be formed by depositing a predetermined transparent electrode layer material using the RPD (Reactive Plasma Deposition) method.

[0023] According to the above configuration, the second transparent electrode layer is formed as a layer without a porous structure by the RPD method. In the manufacturing method according to this disclosure, as described above, the perovskite compound is easily formed in the porous electron transport layer and the porous insulating layer before the second transparent electrode layer is formed, so the second transparent electrode layer does not need to have a porous structure.

[0024] When an organic layer is used in the power generation layer, if an attempt is made to form a second transparent electrode layer on the organic layer by ordinary sputtering or the like, the organic layer may be damaged, and the damage will reduce the power generation efficiency.

[0025] The RPD method is a film forming method in which electrons emitted from a plasma gun are guided to an evaporation material by a magnetic field to heat and sublimate the transparent electrode layer material, and the sublimated transparent electrode layer material is activated in high-density plasma to impart high reactivity. Since damage to the perovskite compound in the porous electron transport layer or porous insulating layer on which the second transparent electrode layer is laminated is low, a transparent electrode layer with good crystallinity can be formed. The film thickness distribution can be controlled by adjusting the plasma beam.

[0026] Preferred examples of the transparent electrode layer material used for the second transparent electrode layer include IWO (indium tungsten oxide), ITO (indium tin oxide), and GZO (gallium-doped zinc oxide).

[0027] In order to achieve the above object, a solar cell according to the present disclosure is a solar cell, characterized in that at least a transparent substrate, a first transparent electrode layer, a porous electron transport layer, a porous insulating layer, and a second transparent electrode layer are laminated in this order, the porous electron transport layer and the porous insulating layer are filled with a perovskite compound, and the second transparent electrode layer does not contain the perovskite compound.

[0028] According to the above configuration, the perovskite compound is formed in the porous electron transport layer and the porous insulating layer, and no perovskite compound is present in the second transparent electrode layer, so the second transparent electrode layer can be formed of a light-transmitting material. Since both light-receiving surfaces of the solar cell have light-transmitting properties, the solar cell can be used as a tandem solar cell in which solar cells having different band gaps (for example, the solar cell and a silicon solar cell) are combined with each other.

[0029] Since the perovskite compounds contained within the porous electron transport layer and porous insulating layer have high hole transport properties, a hole transport layer is not essential for this solar cell, thus enabling cost reduction.

[0030] In this disclosure, a porous hole transport layer may be laminated between the porous insulating layer and the second transparent electrode layer, and the porous hole transport layer may be filled with the perovskite compound.

[0031] As described above, a porous hole transport layer may be laminated between the porous insulating layer and the second transparent electrode layer, and the porous hole transport layer may be filled with a perovskite compound.

[0032] To achieve the above-mentioned objectives, the solar cell according to the present disclosure is a solar cell characterized in that at least a transparent substrate, a first transparent electrode layer, a porous hole transport layer, a porous insulating layer, a porous electron transport layer, and a second transparent electrode layer are stacked in this order, and the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are filled with a perovskite compound, but the second transparent electrode layer does not contain the perovskite compound.

[0033] According to the above configuration, perovskite compounds are formed in the porous electron transport layer and the porous insulating layer, and since no perovskite compounds are present in the second transparent electrode layer, the second transparent electrode layer can be formed from a light-transmitting material. Because both light-receiving surfaces of this solar cell are light-transmitting, it can be used as a tandem solar cell by combining solar cells with different band gaps (for example, this solar cell and a silicon solar cell).

[0034] In this disclosure, the second transparent electrode layer may be characterized by not having pores.

[0035] In a configuration where it is not necessary to impregnate the second transparent electrode layer with a precursor solution of the perovskite compound, the second transparent electrode layer does not necessarily have a pore structure.

[0036] In this disclosure, the second transparent electrode layer may be characterized by having an average light transmittance of 80% or more in the wavelength range of 300 nm to 1100 nm.

[0037] According to the above configuration, the second transparent electrode layer has an average light transmittance of 80% or more in the wavelength range of 300 nm to 1100 nm, so the solar cell can transmit light from the first transparent electrode layer side to the first transparent electrode layer side. Therefore, the solar cell can be used as a tandem solar cell in combination with a silicon solar cell. [Effects of the Invention]

[0038] According to this disclosure, it is possible to provide a method for manufacturing solar cells and solar cells that have a good yield and high reliability in power generation. [Brief explanation of the drawing]

[0039] [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 illustrating the manufacturing method of the solar cell according to this disclosure. [Figure 3] Figure 3 is an explanatory diagram illustrating the manufacturing method of the solar cell according to this disclosure. [Figure 4] Figure 4 is an explanatory diagram illustrating a conventional method for manufacturing solar cells. [Modes for carrying out the invention]

[0040] 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.

[0041] [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 transparent electrode layer 70 on a transparent substrate 10. Perovskite compounds are present in the pores of the power generation layer 60. 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 transparent electrode layer 70 becomes the anode.

[0042] The solar cell 100 can allow sunlight (an example of light) to enter the power generation layer 60 from both the first transparent electrode layer 20 side and the second transparent electrode layer 70 side. Furthermore, the solar cell 100 can transmit light incident from either the first transparent electrode layer 20 side or the second transparent electrode layer 70 side outward through the second transparent electrode layer 70 or the first transparent electrode layer 20. The reverse is also true.

[0043] 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.

[0044] 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 transparent 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.

[0045] The following describes each component of the solar cell 100 in order.

[0046] [Transparent substrate 10] 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).

[0047] 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.

[0048] [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).

[0049] 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.

[0050] The thickness of the first transparent electrode layer 20 is not particularly limited and can be any thickness that allows it to exhibit desired properties (e.g., electron transportability and transparency).

[0051] [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.

[0052] 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.

[0053] 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.

[0054] 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 transparent electrode layer 70, which is a factor in the decrease of electromotive force, is suppressed.

[0055] [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 transparent electrode layer 70.

[0056] The power generation layer 60 may include a porous layer and a light-absorbing layer, and refers to all or part of the layer between the first transparent electrode layer 20 and the second transparent electrode layer 70. The light-absorbing layer is often located between the first transparent electrode layer and the second conductive layer, in which case the photoelectric conversion layer is also located only between the first transparent electrode layer and the second transparent electrode layer. However, if the first transparent electrode layer and the second transparent electrode layer have a special shape such as being porous, the light-absorbing layer may include a region encompassing the first transparent electrode layer and the second transparent electrode layer themselves, in which case the power generation layer can also include the first transparent electrode layer and the second transparent 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 transparent electrode layer. In other words, in any case, a solar cell is provided with a first transparent electrode layer, a power generation layer (including a part of the power generation layer), and a second transparent electrode layer in that order from the substrate, and this does not exclude the first and second transparent electrode layers themselves from being included, nor does it exclude the existence of a power generation layer in a part other than between the first and second transparent electrode layers. In this embodiment, the solar cell is composed of a porous layer including 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.

[0057] 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.

[0058] [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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 also blocking holes generated by photoexcitation from moving to the porous electron transport layer 40.

[0063] [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 of an insulating material. The solar cell 100 according to this disclosure, by including the porous insulating layer 50, can prevent contact between the porous electron transport layer 40 and the second transparent 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 transparent electrode layer 70 can be increased, suppressing physical contact between the materials on both sides, and suppressing the recombination of electrons and holes generated in the power generation layer 60.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] 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.

[0073] 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.

[0074] 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.

[0075] For example, it is preferable that A is at least one alkylamine or alkali element, B is at least one of lead, tin, or germanium, and X is at least one of iodine, bromine, or chlorine, or that A is an alkali element, B is at least one of lead, tin, or germanium, and X is at least one of iodine, bromine, or chlorine.

[0076] 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.

[0077] [Second transparent electrode layer] The second transparent electrode layer 70, acting as the positive electrode, is a layer that transports holes generated in the power generation layer 60. The second transparent electrode layer 70 is conductive and translucent, and has an average light transmittance of 80% or more in the wavelength range of 300 nm to 1100 nm. As long as the solar cell 100 functions as a solar cell, it is clear that the layer on the hole transport side of the power generation layer 60 or on the hole transport side of the power generation layer 60 has the function of transporting holes, and no confirmation is required. In other words, as long as the solar cell 100 functions as a solar cell, the layer on the hole transport side of the power generation layer 60 or on the hole transport side of the power generation layer 60 can be called a "hole transporting layer". The hole transport side can be rephrased as the positive electrode side of the solar cell 100.

[0078] The second transparent electrode layer 70 is mainly composed of a transparent electrode material. Examples of transparent electrode materials include conductive transparent materials such as 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); conductive fine particles such as silver nanowires and carbon nanofibers; and transparent conductive polymers such as polymers containing poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT / PSS).

[0079] The thickness of the second transparent electrode layer 70 is not particularly limited as long as it is thick enough to impart the desired conductivity to the power generation layer 60, and a thickness of about 200 nm is sufficient. Furthermore, the second transparent electrode layer 70 may be formed over the entire surface of the power generation layer 60, or it may be formed on only a part of the surface of the power generation layer 60.

[0080] The thickness of the second transparent electrode layer 70 is not particularly limited and can be any thickness that allows it to exhibit the desired properties (e.g., hole transport).

[0081] Since the second transparent electrode layer 70 does not contain perovskite compounds, there is no risk of lead iodide, an insulator, forming, as is the case with solar cells obtained by conventional manufacturing methods, thus resulting in high reliability of power generation.

[0082] [Method of manufacturing solar cells] The method for manufacturing the solar cell 100 related to this disclosure will be described below.

[0083] [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.

[0084] [Formation of the first transparent electrode layer] Subsequently, 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.

[0085] [Formation of a dense electron transport layer] Subsequently, 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 can be formed, for example, 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.

[0086] 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.

[0087] [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.

[0088] [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.

[0089] [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. As shown in Figure 3, a precursor solution 61 of the perovskite compound is dropped onto the porous insulating layer 50, allowing it to penetrate into the pores of the porous insulating layer 50 and the porous electron transport layer 40, and then dried. This forms crystals of the perovskite compound in the pores of the porous insulating layer 50 and the porous electron transport layer 40, thus obtaining the power generation layer 60.

[0090] The method for dropping the perovskite compound precursor solution 61 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.

[0091] [Formation of the second transparent electrode layer] After forming the power generation layer 60, a second transparent electrode layer 70 is formed on top of the power generation layer 60. Specifically, the second transparent electrode layer 70 is formed by depositing transparent electrode layer materials such as IWO (indium tungsten oxide), ITO (indium tin oxide), and GZO (gallium-doped zinc oxide) using the RPD (Reactive Plasma Deposition) method without preheating the power generation layer 60.

[0092] Since the second transparent electrode layer 70 is formed by the RPD method, the effect on the perovskite compound contained in the power generation layer 60 is extremely small.

[0093] [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 transparent electrode layer 70 on a transparent substrate 10. However, the configuration of the solar cell 100 is not limited to this.

[0094] A porous hole transport layer may be provided between the porous insulating layer 50 and the second transparent 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 transparent electrode layer 70 on a transparent substrate 10. Even in the manufacturing method of such a solar cell 100, the formation of the second transparent electrode layer 70 is carried out after the formation of the power generation layer 60 comprising the porous electron transport layer 40, the porous insulating layer 50, and the porous hole transport layer. Furthermore, it is desirable that no perovskite compound is provided between the porous hole transport layer and the second transparent electrode layer 70. The presence of the perovskite compound on the porous hole transport layer may lead to the formation of insulating material from the decomposition of the perovskite compound, potentially causing a degradation in reliability. Therefore, by not providing the perovskite compound on the porous hole transport layer, i.e., between the porous hole transport layer and the second transparent electrode layer 70, the degradation of reliability can be suppressed. Alternatively, a dense hole transport layer may be provided instead of the porous hole transport layer, or a dense hole transport layer may be provided on top of the porous hole transport layer. Additionally, the structure may include a portion near the upper end of the porous hole transport layer where the pores of the porous hole transport layer do not contain the perovskite compound. Furthermore, a layer where the pores of the porous hole transport layer do not contain the perovskite compound may be formed separately from the existing porous hole transport layer as a cover layer or coating layer. Furthermore, if the structure is reversed, the hole transport layer and electron transport layer can be swapped, as long as no contradictions arise.

[0095] [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 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 transparent electrode layer 70 on a transparent substrate 10. However, the configuration of the solar cell 100 is not limited to this.

[0096] The order in which the porous electron transport layer 40 and the porous hole transport layer are stacked 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 porous hole transport layer, a porous insulating layer 50, and a porous electron transport layer 40, and a second transparent electrode layer 70 on a transparent substrate 10 in this order. Even in the manufacturing method of such a solar cell 100, the formation of the second transparent electrode layer 70 is carried out after the power generation layer 60 comprising the porous hole transport layer, the porous insulating layer 50, and the porous electron transport layer 40 has been formed.

[0097] 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.

[0098] [Note] (Aspect 1) A method for manufacturing solar cells, At least a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, and a porous insulating layer are formed on a transparent substrate in this order, or 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 are formed in this order. Subsequently, a precursor solution of the perovskite compound is permeated into the porous electron transport layer and the porous insulating layer, or the porous hole transport layer, the porous electron transport layer and the porous insulating layer, to form the perovskite compound within the porous electron transport layer and the porous insulating layer, or within the porous hole transport layer, the porous insulating layer and the porous electron transport layer. A method for manufacturing a solar cell, characterized by subsequently forming a second transparent electrode layer on the porous insulating layer. (Aspect 2) The method for manufacturing a solar cell according to embodiment 1, characterized in that the second transparent electrode layer is obtained by depositing a predetermined transparent electrode layer material by RPD (Reactive Plasma Deposition). (Aspect 3) It is a solar cell, At a minimum, a transparent substrate, a first transparent electrode layer, a porous electron transport layer, a porous insulating layer, and a second transparent electrode layer are laminated in this order. A solar cell characterized in that the porous electron transport layer and the porous insulating layer are filled with a perovskite compound, but the second transparent electrode layer does not contain the perovskite compound. (Aspect 4) A porous hole transport layer is laminated between the porous insulating layer and the second transparent electrode layer. The solar cell according to embodiment 3, characterized in that the porous hole transport layer is filled with the perovskite compound. (Appendix 5) It is a solar cell, At a minimum, a transparent substrate, a first transparent electrode layer, a porous hole transport layer, a porous insulating layer, a porous electron transport layer, and a second transparent electrode layer are laminated in this order. A solar cell characterized in that the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are filled with a perovskite compound, but the second transparent electrode layer does not contain the perovskite compound. (Aspect 6) The solar cell according to any one of embodiments 3 to 5, characterized in that the second transparent electrode layer does not have pores. (Aspect 7) The solar cell according to any one of embodiments 3 to 6, characterized in that the second transparent electrode layer has an average light transmittance of 80% or more in the wavelength range of 300 nm to 1100 nm. [Industrial applicability]

[0099] According to the present invention, it is possible to provide a method for manufacturing a solar cell with a high yield and high reliability in power generation, as well as a solar cell itself. [Explanation of Symbols]

[0100] 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 61: Precursor solution 70: Second transparent electrode layer 100: Solar cell

Claims

1. A method for manufacturing solar cells, At least a first transparent electrode layer, a dense electron transport layer, a porous electron transport layer, and a porous insulating layer are formed on a transparent substrate in this order, or 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 are formed in this order. Subsequently, a precursor solution of the perovskite compound is permeated into the porous electron transport layer and the porous insulating layer, or the porous hole transport layer, the porous electron transport layer and the porous insulating layer, to form the perovskite compound within the porous electron transport layer and the porous insulating layer, or within the porous hole transport layer, the porous insulating layer and the porous electron transport layer. A method for manufacturing a solar cell, characterized by subsequently forming a second transparent electrode layer on the porous insulating layer.

2. The method for manufacturing a solar cell according to claim 1, characterized in that the second transparent electrode layer is obtained by forming a predetermined transparent electrode layer material by RPD (Reactive Plasma Deposition).

3. It is a solar cell, At a minimum, a transparent substrate, a first transparent electrode layer, a porous electron transport layer, a porous insulating layer, and a second transparent electrode layer are laminated in this order. A solar cell characterized in that the porous electron transport layer and the porous insulating layer are filled with a perovskite compound, but the second transparent electrode layer does not contain the perovskite compound.

4. A porous hole transport layer is laminated between the porous insulating layer and the second transparent electrode layer. The solar cell according to claim 3, characterized in that the porous hole transport layer is filled with the perovskite compound.

5. It is a solar cell, At a minimum, a transparent substrate, a first transparent electrode layer, a porous hole transport layer, a porous insulating layer, a porous electron transport layer, and a second transparent electrode layer are laminated in this order. A solar cell characterized in that the porous hole transport layer, the porous insulating layer, and the porous electron transport layer are filled with a perovskite compound, but the second transparent electrode layer does not contain the perovskite compound.

6. The solar cell according to claim 3 or 5, characterized in that the second transparent electrode layer does not have pores.

7. The solar cell according to claim 3 or 5, characterized in that the second transparent electrode layer has an average light transmittance of 80% or more in the wavelength range of 300 nm to 1100 nm.

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