Solar cell, solar module, and method for manufacturing the same

Abstract

To provide a solar battery cell in which the permeability of a perovskite solution is improved.SOLUTION: A solar battery cell 10 has a transparent electrode layer 3, a porous electron transport layer 5, an insulating layer 6, and a second conductive layer 7 provided in this order from a base body 2. The porous electron transport layer 5 and the insulating layer 6 include a porous layer and a light absorption part. The second conductive layer 7 has a window part 7a for exposing a part of an upper surface of the insulating layer 6.SELECTED DRAWING: Figure 4B

Description

Technical Field

[0001] The present disclosure relates to a solar cell, a solar cell module using a perovskite compound, and a method for manufacturing the same.

Background Art

[0002] In recent years, solar cells have been increasingly popular as a means of utilizing renewable energy. As solar cells, solar cells using inorganic optoelectronic conversion elements (for example, silicon-based solar cells, CIGS-based solar cells, and CdTe-based solar cells) have become widespread, but solar cells using organic optoelectronic conversion elements (for example, organic thin-film solar cells, dye-sensitized solar cells, and perovskite solar cells) are also being studied.

[0003] By the way, in a solar cell formed by stacking a plurality of layers, it is necessary to accurately align the positions of each layer, which complicates the manufacturing process. Therefore, a method for simplifying the manufacturing process has been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional solar cell modules are multilayer structures in which at least two solar cells are deposited on a substrate having a down-web direction and a cross-web direction, and include: a first electrode strip disposed on the substrate, extending along the cross-web direction and forming a layer of a first conductive material; an insulating strip disposed on the layer of the first conductive material, determining connection and active regions, and extending along the down-web direction, formed of an insulating material; a functional stack disposed on the layer of the first conductive material and within the active region, including a layer of photoactive semiconductor material that coats the entire web; a second electrode strip disposed in the functional stack and within the active region, extending in the cross-web direction, aligned with the first electrode strip to form a solar cell; and an electrical connection pattern extending on the insulating strip and within the connection region for electrically connecting the second electrode strip of any solar cell to the first electrode strip of an adjacent solar cell.

[0006] Incidentally, when manufacturing perovskite solar cells, a process is carried out in which a perovskite solution is permeated into a porous layer placed beneath the electrodes. However, as with conventional solar cell modules, if the porous layer is covered by electrodes, there is a problem in that it becomes difficult for the perovskite solution to reach the porous layer.

[0007] This disclosure was made to solve the above-mentioned problems and aims to provide solar cells, solar modules, and methods for manufacturing the same, with improved permeability of the perovskite solution. [Means for solving the problem]

[0008] The solar cell according to this disclosure is a solar cell provided with a first conductive layer, a photoelectric conversion layer, and a second conductive layer in that order from a substrate, wherein the photoelectric conversion layer includes a porous layer and a light absorbing portion, and the second conductive layer is provided with a window portion that exposes a part of the upper surface of the photoelectric conversion layer.

[0009] In the solar cell relating to this disclosure, the light-absorbing portion may have a configuration that includes a perovskite compound.

[0010] In the solar cell relating to this disclosure, the light-absorbing portion may have a configuration that includes an organic-inorganic hybrid compound.

[0011] The solar cell according to this disclosure may be configured such that, when the direction along the long side of the second conductive layer is defined as the long side direction, the window portion has a slit shape that extends in a direction intersecting the long side direction.

[0012] The solar cell according to this disclosure may be configured such that, when the direction along the long side of the second conductive layer is defined as the long side direction, the window portion has a meandering shape in a direction intersecting the long side direction.

[0013] In the solar cell relating to this disclosure, the window portion may be configured to have a shape that imitates one of the following: letters, symbols, or patterns.

[0014] In the solar cell according to this disclosure, when the direction along the long side of the second conductive layer is defined as the long side direction, the window portion may be configured as a slit shape extending along the long side direction.

[0015] In the solar cell relating to this disclosure, the window portion may be configured to have a width of 2 μm or less.

[0016] In the solar cell according to this disclosure, the photoelectric conversion layer may include a stacked electron transport layer and an insulating layer, and the electron transport layer and the insulating layer may have a porous structure having voids containing the perovskite compound.

[0017] The solar cell module relating to this disclosure is a solar cell module having a plurality of solar cells relating to this disclosure, characterized in that the plurality of solar cells are connected in series in a monolithic structure.

[0018] The method for manufacturing a solar cell according to the present disclosure includes a step of providing a first conductive layer, a photoelectric conversion layer, and a second conductive layer in order from a substrate. The photoelectric conversion layer includes a porous layer and a light absorption part, and the second conductive layer is provided with a window part that exposes a part of the upper surface of the photoelectric conversion layer.

Advantages of the Invention

[0019] According to the present disclosure, since the second conductive layer is provided with a window part, the perovskite solution can be directly dropped onto the upper surface of the photoelectric conversion layer, and the permeability can be improved. In addition, when viewed from above, the window part can be visually recognized, so the shape of the window part can be appropriately designed to improve the designability.

Brief Description of the Drawings

[0020] [Figure 1A] It is a schematic cross-sectional view (Part 1) showing a solar cell according to an embodiment of the present disclosure. [Figure 1B] It is a schematic cross-sectional view (Part 2) showing a solar cell according to an embodiment of the present disclosure. [Figure 2] It is a schematic cross-sectional view showing a step of dropping a perovskite solution in the method for manufacturing a solar cell. [Figure 3] It is a schematic top view showing a solar cell module according to a first embodiment of the present disclosure. [Figure 4A] It is a schematic top view showing a solar cell module according to a second embodiment of the present disclosure. [Figure 4B] It is a schematic cross-sectional view showing a cross-section at arrow C-C in FIG. 4A. <​​​​​​​​​​​​ [Modes for carrying out the invention]

[0021] (First Embodiment) Hereinafter, a solar cell and a solar cell module according to the first embodiment of this disclosure will be described with reference to the drawings.

[0022] Figure 1A is a schematic cross-sectional view (part 1) showing a solar cell module according to the first embodiment of this disclosure, and Figure 1B is a schematic cross-sectional view (part 2) showing a solar cell module according to the first embodiment of this disclosure. Figure 1A corresponds to the cross-section indicated by arrow AA in Figure 3, which will be described later, and Figure 1B corresponds to the cross-section indicated by arrow BB in Figure 3, which will be described later. Note that the schematic cross-sectional views of this disclosure show only what is present in the cross-section, and what is visible (or present) behind the cross-section is omitted.

[0023] As shown in Figure 1B, the solar cell 10 according to the first embodiment of this disclosure has a transparent electrode layer 3 (an example of a first conductive layer), a dense electron transport layer 4, a photoelectric conversion layer (a porous electron transport layer 5, an insulating layer 6, and a light absorbing layer in this embodiment), and a second conductive layer 7 laminated on a substrate 2. A solar cell module 1 is also constructed by connecting a plurality of solar cells 10 in series on the substrate 2. For the purpose of explanation below, the direction in which the plurality of solar cells 10 are arranged in series may be referred to as the short side direction X (the direction of the double-headed arrow X in the figure). Also, one of the plurality of solar cells 10 (the solar cell 10 on the right in Figure 1A or Figure 1B, etc.) may be described with focus, and the remaining solar cells 10 (the solar cell 10 on the left in Figure 1A or Figure 1B, etc.) may be referred to as the adjacent solar cell 10.

[0024] The base 2 is the base of the solar cell 10, and is the same as or includes the same as a substrate or base material. It may be hard and rigid, or it may be flexible and less rigid. Examples of the shape of the base 2 include a flat plate and a film. When light is irradiated (light is incident) on the surface of the solar cell 10 that is on the base 2 side (the bottom surface of the base 2 in Figure 1A), that is, when the side of the base 2 is the light-receiving surface, it is preferable that the base 2 is transparent. In this case, examples of materials for the base 2 include glass and heat-resistant transparent resin. When light is irradiated from the opposite side, the base 2 may be opaque. It should be noted that transparency means that light is transmitted, but this does not exclude anything that reflects or absorbs even a little light. It is sufficient that light is transmitted appropriately, and this can be considered synonymous with being provided on the light-receiving surface side of the solar cell (including the part where light is incident, as is the case in this disclosure). Therefore, it can be said that it is transparent if it is provided at least on the light-receiving surface side of the solar cell.

[0025] The first conductive layer, that is, the transparent electrode layer 3 which is an example of the first conductive layer in this embodiment, is a conductive member. The first conductive layer is formed on the substrate 2, on the surface of the substrate 2, or on one side of the substrate 2 (for example, the upper side), and functions as an electrode for extracting the photovoltaic power of the solar cell 10. The transparent electrode layer 3 is divided into multiple sections and arranged in an island-like manner, spaced apart in the short-side direction X. The transparent electrode layer 3 is formed of a transparent conductive material, such as conductive transparent materials such as FTO (fluorine-doped tin oxide), CuI (copper iodide), ITO (indium tin oxide), SnO2 (tin oxide), AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), ATO (antimond-doped tin oxide), or conductive transparent polymers. Note that the chemical formulas are representative examples and any compound name is acceptable (similar in this disclosure). Furthermore, while a stoichiometric composition ratio of the chemical formula is desirable, it is not necessarily required (similarly in this disclosure). The transparent electrode layer 3 may have a configuration in which a conductive metal such as silver or its fine wires are formed on an oxide film of a conductive transparent material. The term "film" does not specify thickness or width, and includes patterned or island-shaped films or films with parts of different thicknesses. Preferably, the film has a substantially constant thickness. Unless otherwise specified, "substantially" 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.

[0026] The dense electron transport layer 4 is a layer capable of transporting electrons generated in the light-absorbing portion (for example, a perovskite compound). The dense electron transport layer 4 naturally possesses this function as long as the solar cell has a photoelectric conversion function, and can be considered equivalent to being located on the electron transport side of the light-absorbing portion of the solar cell. Therefore, as long as it is located on the electron transport side of the perovskite compound, it can be said to have an electron transport function. It is preferable that the dense electron transport layer 4 has a function of blocking hole transport. The dense electron transport layer 4 is dense. Details regarding the dense material are described below, but it is preferable that the layer has few or no pores. Furthermore, it is preferable that most of these pores are independent and not connected. The dense layer can function as a layer where, even if a liquid is dropped onto it, the liquid hardly penetrates the dense layer. In this embodiment, the dense electron transport layer 4 is formed of titanium oxide or tin oxide. Furthermore, the dense electron transport layer 4 is placed on top of the transparent electrode layer 3 and does not exist on the substrate 2.

[0027] A layer does not define thickness or width, and includes patterns, islands, or parts with different thicknesses. Preferably, a layer is a component with approximately constant thickness.

[0028] Compact matter, also known as compact or compact quality, can be the same as or contain the same as these.

[0029] Porous, also known as porous or mesoporous, can be the same as or include the same as these. In this disclosure, porous means a material that can contain light-absorbing portions (for example, perovskite compounds) in its voids (which can be expressed in various ways, such as gaps, holes, or pores). The porous layer may include a porous electron transport layer or an insulating layer, or a porous electron transport layer and an insulating layer. Preferably, the porous electron transport layer is located on one side of the thickness direction of the porous layer (for example, the bottom side), and the insulating layer is located on the opposite side (for example, the top side). The porous layer may also include a second conductive layer.

[0030] Furthermore, dense material means material with extremely small voids. In other words, in this disclosure, dense material means material in which, upon observation, no light-absorbing portion (in this embodiment, a perovskite compound, and hereafter described as a perovskite compound) is present on one side in the thickness direction of the dense material (for example, the lower side). That is, even if a perovskite compound is present 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 suppresses the penetration of perovskite compounds, and allows for a state where no perovskite compounds are present 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 voids, 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.

[0031] The porous electron transport layer 5 (an example of an electron transport layer) functions as an electron transport layer that transports electrons generated in the light absorption section to the electrodes. For example, titanium oxide, tin oxide, and aluminum oxide can be used as materials for the porous electron transport layer 5. Furthermore, any N-type inorganic oxide is preferable for the porous electron transport layer 5. As previously described in detail, the porous layer preferably has numerous pores within it, with these pores interconnected. Because it is porous, when a liquid (with good wettability) is dropped onto the porous layer (where the pores are hollow), the liquid can permeate into the porous layer, functioning as a layer. The porous electron transport layer 5, like the dense electron transport layer 4, is a layer capable of transporting electrons generated by the perovskite compound, and naturally possesses this function only insofar as it functions as a solar cell. That is, as long as it is located on the electron transport side (or negative electrode side, similarly in this disclosure) of the perovskite compound in the solar cell, it can be considered to have an electron transport function. The porous electron transport layer 5 may preferably be a mesoporous layer. Furthermore, it would be even better if the porous electron transport layer 5 were a mesoporous nanocrystalline layer.

[0032] In this embodiment, the porous electron transport layer 5 is located on top of the dense electron transport layer 4, and is provided in a narrower area in the short-side direction X than the dense electron transport layer 4. Therefore, there is an area on the upper surface of the dense electron transport layer 4 that is not covered by the porous electron transport layer 5. Furthermore, the porous electron transport layer 5 is located near the edge of the dense electron transport layer 4 in the short-side direction X (the right edge in Figure 1A).

[0033] In this embodiment, the dense electron transport layer 4 is arranged on the transparent electrode layer 3 with the same width (width in the short-side direction X in Figure 1B), but it is not necessarily required that the widths be the same. At the end in the short-side direction X (the left end in Figure 1B), a portion of the transparent electrode layer 3 may be formed to be exposed and not covered by the dense electron transport layer 4. Doing so improves the electrical connection between the transparent electrode layer 3 of the solar cell (the solar cell on the right in Figure 1B) and the second conductive layer 7 of the adjacent solar cell (the solar cell on the left in Figure 1B).

[0034] The insulating layer 6 is made of a porous material. Examples of materials for the insulating layer 6 include metal oxides containing titanium oxide, zirconium dioxide, and aluminum oxide, and oxides containing silicon dioxide. It should be noted that insulation does not need to completely prevent the movement of charge; depending on its thickness and structure, it is acceptable if it can suppress charge movement even if it cannot completely prevent it. Adding an insulating layer increases the distance between the first conductive layer (including the electron transport layer if present) and the second conductive layer (including the hole transport layer if present), suppressing physical contact between the materials on both sides and preventing the recombination of electrons and holes generated in the light absorption area. In other words, adding an insulating layer can improve the performance of the solar cell and contribute to achieving commercialization level performance. Therefore, the insulating layer exists between the first conductive layer (including the electron transport layer if present) and the second conductive layer (including the hole transport layer if present), contributing to increasing the distance between each side. As a result, if the solar cell is commercialized, verification is sufficient, and it is not necessary to verify the physical properties of the insulating performance. Furthermore, the insulating layer 6 is a porous layer containing voids, preferably having many voids with a size of 20 nm or more. In other words, the insulating layer 6 is occupied by its constituent metal oxides and voids, which are the gaps between the metal oxides. The insulating layer 6 also has voids with a size of less than 20 nm, and the porosity is determined by including these small voids. In addition, light-absorbing portions that absorb irradiated light are provided in the voids of the insulating layer 6.

[0035] In this embodiment, the insulating layer 6 is located on the porous electron transport layer 5 and extends over a wider area in the short-side direction X than the porous electron transport layer 5. Specifically, one end of the insulating layer 6 in the short-side direction X (the left end in Figure 1A) covers a portion of the upper surface of the dense electron transport layer 4, while the other end in the short-side direction X (the right end in Figure 1A) extends outside the dense electron transport layer 4, covering the transparent electrode layer 3 and the side surface of the dense electron transport layer 4. The other end of the insulating layer 6 in the short-side direction X does not reach the transparent electrode layer 3 and dense electron transport layer 4 of the adjacent solar cell 10, and is spaced apart.

[0036] The second conductive layer 7 is a conductive material. It functions as an electrode for extracting the photovoltaic power of the solar cell 10. It has the function of collecting holes photoexcited in the light absorption section, and is preferably formed of a porous carbon material. The second conductive layer 7 is provided in a region where a portion overlaps with the insulating layer 6 in the short-side direction X. Specifically, one end of the second conductive layer 7 in the short-side direction X (the left end in Figure 1B) does not reach the end of the insulating layer 6, and a portion of the upper surface of the insulating layer 6 (the upper surface 6a of the insulating layer) is exposed. The other end of the second conductive layer 7 in the short-side direction X (the right end in Figure 1B) extends outside the insulating layer 6 and reaches the transparent electrode layer 3 and dense electron transport layer 4 of the adjacent solar cell 10. In other words, since the end of the second conductive layer 7 is in contact with the dense electron transport layer 4 of the adjacent solar cell 10, the adjacent solar cells 10 are electrically connected to each other.

[0037] As the second conductive layer 7, for example, a metal film with a work function of 5 eV or higher can be used. By having the second conductive layer 7 composed of a metal with a deep work function (5 eV or higher), it becomes easier to generate a band structure bend that smooths the flow of holes at the interface between the light-absorbing layer or light-absorbing portion or the layer on the light-absorbing portion side and the second conductive layer. As the material for the second conductive layer 7, for example, metals such as Ni, Pt, and Pd can be used. The film thickness of the second conductive layer 7 is preferably around 50 nm to 150 nm. The second conductive layer 7 can be formed by, for example, a sputtering deposition method or a vacuum deposition method. In addition, conductive carbon materials such as graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon black can be used. In principle, any material that is conductive is not excluded from application.

[0038] Furthermore, the second conductive layer 7 is provided with a window portion 7a that exposes a part of the upper surface 6a of the insulating layer. The window portion 7a is provided in a region that overlaps with the insulating layer 6 at least partially, and in the region where the window portion 7a is provided, the upper surface 6a of the insulating layer is exposed. That is, as shown in Figure 1A, a schematic cross-sectional view at arrow AA, which is a cross-section of the portion where the window portion 7a is formed in Figure 3, the second conductive layer 7 is removed in the region where the window portion 7a is provided, and the upper surface 6a of the insulating layer is exposed. In contrast, in Figure 1B, a schematic cross-sectional view at arrow BB, which is a cross-section of the portion where the window portion 7a is not formed in Figure 3, the second conductive layer 7 is formed because the window portion 7a is not provided, and the upper surface 6a of the insulating layer is covered by the second conductive layer 7 in the portion where the second conductive layer 7 is formed. The window portion 7a may be provided in a region that overlaps with the substrate 2 or the dense electron transport layer 4. The shape of the window portion 7a when viewed from above will be explained with reference to Figure 3, which will be described later.

[0039] The light-absorbing portion described above contains a perovskite compound. In this embodiment, the porous electron transport layer 5, the insulating layer 6, and the second conductive layer 7 also have light-absorbing portions. That is, the light-absorbing portions are arranged in the voids (which can be expressed in various ways, such as gaps, holes, or pores) of these layers. Preferably, these layers are filled with light-absorbing portions. It is desirable that the voids in the porous electron transport layer 5, the insulating layer 6, and the second conductive layer 7 be filled with light-absorbing portions. As long as a solar cell has a photoelectric conversion function, it naturally includes a light-absorbing portion as a component. The light-absorbing portion generates electrons and holes by absorbing light, the electrons generated in the light-absorbing portion move to the electron transport layer, and the holes generated in the light-absorbing portion move to the second conductive layer 7, where the charge is separated. As long as a solar cell has a photoelectric conversion function, it can be confirmed that electrons and holes are generated by absorbing light in the portion with the appropriate material, and it is not necessary to check the physical properties of the photoelectric conversion of the light-absorbing portion in order to confirm that it is a light-absorbing portion.

[0040] A light-absorbing region refers to a specific area (for example, a perovskite compound) that absorbs light, and this region can be collectively described as a light-absorbing layer. Here, a light-absorbing region can mean a specific area or part of the light-absorbing layer. Furthermore, a light-absorbing layer can mean a collection of light-absorbing regions that exist discretely in a region with a certain thickness (which does not need to be constant) in a certain direction.

[0041] The perovskite compound contained in the light-absorbing portion is composed of a compound represented by the general formula: ABX3···(1). However, while the composition ratio of each is preferably 1:1:3, it is not necessarily 1:1:3, the content of each element may be adjusted as appropriate, and each constituent element does not need to be of only one type. As long as the light-absorbing portion has a photoelectric conversion function, the perovskite compound contained in the light-absorbing portion is exhibiting that photoelectric conversion function, and therefore it is reasonable to assume that it is exhibiting that function even with the degree of freedom in composition as described in terms of composition ratio and type of constituent element. In general formula (1), A is an organic molecule (including an organic group or organic cation, as is the case in this disclosure) or an inorganic atom or molecule (including an inorganic group or inorganic cation, as is the case in this disclosure) or a combination thereof, B is a metal atom or molecule (including a metal cation, as is the case in this disclosure), and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or chalcogen anion, as is the case in this disclosure). In general formula (1), the three X's may be the same or different from each other. As long as a solar cell has a photoelectric conversion function, the perovskite compound contained in the light-absorbing part is exhibiting a photoelectric conversion function, and this should be taken into consideration. That is, if it can be confirmed that a compound is a perovskite compound, it is reasonable to consider it a perovskite compound that exhibits a photoelectric conversion function if it has A, B, and X. For example, it is sufficient if it is found to have an organic molecule, a metal atom, and a halogen atom. Furthermore, as long as a solar cell has a photoelectric conversion function, it can be confirmed that a compound is a perovskite compound if elements corresponding to A, B, and X are detected. For example, as organic molecules, molecules containing carbon, nitrogen, and hydrogen are suitable, and therefore, it is sufficient if carbon, nitrogen, hydrogen, a metal element, and a halogen or chalcogen are detected. Alternatively, a compound is a perovskite compound if it has A, B, and X. For example, it is sufficient if it is found to have an inorganic atom, a metal atom, and a halogen atom. Furthermore, the presence of a perovskite compound can be confirmed if elements A, B, and X are detected, as long as the solar cell has a photoelectric conversion function.For example, cesium or rubidium are preferred as inorganic atoms; therefore, it is sufficient if cesium or rubidium, a metallic element, and a halogen or chalcogen are detected. Furthermore, the fact that it is a perovskite compound is based on the premise that a solar cell has a crystalline structure as long as it has a photoelectric conversion function, and therefore confirmation of the presence of a crystalline structure is not required. The light-absorbing portion may contain substances other than the perovskite compound.

[0042] The light-absorbing portion may contain organic-inorganic hybrid compounds. An organic-inorganic hybrid compound refers to a compound containing both inorganic and organic materials. Perovskite compounds are also included in organic-inorganic hybrid compounds, and solar cells using perovskite compounds are also called organic-inorganic hybrid solar cells. "Organic" typically refers to materials composed of multiple carbon atoms. However, carbon materials such as graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon or carbon black that function as electrodes are not specifically considered organic materials. In other words, organic refers to materials that, excluding the above-mentioned carbon materials such as graphite, have multiple carbon atoms as one of their constituent elements. "Inorganic" refers to materials that are not organic.

[0043] The light-absorbing portion may include quantum dots. A quantum dot is defined as a dot with a maximum width of 100 nm or less. The shape of the quantum dot is not particularly restricted and is not limited to a spherical three-dimensional shape (circular cross-sectional shape), as long as it satisfies the above maximum width. For example, it may have a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branch-shaped three-dimensional shape, a three-dimensional shape with irregularities on the surface, or a combination thereof. The quantum dot is typically made of a semiconductor. A semiconductor is any material that can absorb light and may include at least the materials described below. The semiconductor includes, for example, at least one selected from the group consisting of group II-VI compounds, group III-V compounds, chalcogenides, and perovskite compounds. Note that group II-VI compounds mean compounds containing group II and group VI elements, and group III-V compounds mean compounds containing group III and group V elements. Furthermore, Group II elements include Group 2 and Group 12 elements, Group III elements include Group 3 and Group 13 elements, Group V elements include Group 5 and Group 15 elements, and Group VI elements may include Group 6 and Group 16 elements. Here, the group numbering of elements using Roman numerals is based on the old IUPAC or old CAS system, and the group numbering of elements using Arabic numerals is based on the current IUPAC system. Semiconductors include, for example, at least one selected from the group consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, GaAs, GaP, InN, InAs, InP, and InSb.

[0044] Examples of organic molecules represented by A in general formula (1) include alkylamines, alkylammonium compounds, and nitrogen-containing heterocyclic compounds. In perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or it may be two or more types of organic molecules.

[0045] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0046] Alkylammonium compounds are ionized compounds of the alkylamines mentioned above. Examples of alkylammonium compounds include methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, dipentylammonium, dihexylammonium, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexylammonium, ethylmethylammonium, methylpropylammonium, butylmethylammonium, methylpentylammonium, hexylmethylammonium, ethylpropylammonium, and ethylbutylammonium.

[0047] Examples of nitrogen-containing heterocyclic compounds include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. Nitrogen-containing heterocyclic compounds may also be ionized. Phenethylammonium is preferred as an ionized nitrogen-containing heterocyclic compound.

[0048] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium, or propylammonium, and even more preferably methylammonium.

[0049] In general formula (1), examples of metal atoms represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In perovskite compounds, the metal atom represented by B may be only one type of metal atom, or it may be two or more types of metal atoms. From the viewpoint of improving the light absorption and charge generation characteristics of perovskite compounds, lead atoms or tin atoms are preferred as the metal atom represented by B. From the viewpoint of reducing lead, tin atoms are preferred.

[0050] In general formula (1), examples of halogen atoms represented by X include fluorine, chlorine, bromine, and iodine atoms, while examples of chalcogen atoms include oxygen, sulfur, selenium, and tellurium atoms. In a perovskite compound, the halogen atom or chalcogen atom represented by X may be one or two or more. From the viewpoint of enabling the perovskite compound to utilize light in a broad wavelength range, iodine is preferred as the halogen atom represented by X. More specifically, it is preferable that at least one of the three Xs represents an iodine atom, and more preferably that all three Xs represent iodine atoms.

[0051] As the perovskite compound, compounds represented by the general formula "CH3NH3PbX3 (where X represents a halogen atom)" are preferred, and CH3NH3PbI3 is more preferred. By using a compound represented by the general formula "CH3NH3PbX3" (especially CH3NH3PbI3) as the perovskite compound, electrons and holes can be generated more efficiently in the perovskite compound, and as a result, the photoelectric conversion efficiency of the solar cell 10 can be further improved.

[0052] A photoelectric conversion layer is a layer that converts light into electricity. It can include a porous layer and a light-absorbing layer, and refers to the layer located between the first conductive layer and the second conductive layer. The light-absorbing layer is often located between the first and second conductive layers, in which case the photoelectric conversion layer is also located only between the first and second conductive layers. However, if the first and second conductive layers have a special shape, such as being porous, the light-absorbing layer may include the region encompassing the first and second conductive layers themselves. In such cases, the photoelectric conversion layer can also include the first and second conductive layers themselves, which constitute the portion where the light-absorbing layer is located. Even in this case, the photoelectric conversion layer is located at least between the first and second conductive layers. In other words, in all cases, a solar cell is provided with a first conductive layer, a photoelectric conversion layer, and a second conductive layer in that order from the substrate, and this does not exclude the first and second conductive layers themselves from being included, nor does it exclude the possibility that the photoelectric conversion layer exists in a portion other than between the first and second conductive layers.

[0053] In this embodiment, the hole transport layer (same as the positive electrode layer) may be placed between the perovskite compound, which is the light-absorbing portion, and the second conductive layer 7. The hole transport layer is a layer that has the function of moving holes generated in the light-absorbing portion to the second conductive layer 7. It is self-evident that, as long as the solar cell has a photoelectric conversion function, the hole transport layer located on the hole transport side of the light-absorbing portion or on the hole transport side of the light-absorbing portion has the function of transporting holes, and no confirmation is required. That is, as long as the solar cell functions as a solar cell, the layer located on the hole transport side of the light-absorbing portion (or on the positive electrode side, similarly in this disclosure) or on the hole transport side of the light-absorbing portion is called the hole transport layer. The hole transport layer may be made of a material with, for example, a band gap of 2 eV or more and an ionization potential smaller than 5.4 eV (shallow). The hole transport layer may be made of an inorganic material. The thickness of the hole transport layer can be, for example, about 30 nm to 100 nm. Specific materials that constitute the hole transport layer include oxides and sulfides such as copper oxide (Cu2O), zinc sulfide (ZnS), and nickel oxide. Fine particles of oxides or sulfides may also be used. Organic materials may also be used. Furthermore, the hole transport layer may inhibit electron transport (electron blocking). The hole transport layer may also be accompanied by a separate electron blocking layer. Alternatively, the hole transport layer may be absent, and instead, an electron blocking layer may be present.

[0054] Next, the manufacturing method of the solar cell 10 will be explained with reference to Figure 2.

[0055] Figure 2 is a schematic cross-sectional view showing the step of dropping a perovskite solution in a solar cell manufacturing method.

[0056] Figure 2 schematically shows a cross-section of the solar cell 10 (solar cell module 1) at the window portion 7a during the process of dropping the perovskite solution 8. In Figure 2, the first porous layer 51 corresponds to the porous electron transport layer 5 before dropping the perovskite solution 8, and the second porous layer 61 corresponds to the insulating layer 6 before dropping the perovskite solution 8.

[0057] When fabricating the solar cell 10, first, a laminated substrate is fabricated using general photolithography or screen printing processes to appropriately define the areas for each layer of the solar cell 10. Specifically, a glass substrate having a fluorine-doped tin oxide film was used for the substrate 2 and the transparent electrode layer 3. Then, a dense titanium oxide layer (dense electron transport layer 4) was formed on the fluorine-doped tin oxide film using a spray pyrolysis method. Next, a titanium oxide porous layer (first porous layer 51) was formed by applying a titanium oxide paste onto the dense titanium oxide layer and drying it. Next, a zirconium dioxide porous layer (second porous layer 61) was formed by applying a zirconium dioxide paste onto the porous titanium oxide layer and drying it. Finally, a carbon porous layer (second conductive layer 7) was formed by applying a carbon paste onto the porous zirconium dioxide layer and drying it. As described above, photolithography and screen printing processes may be performed between the processes for forming each layer of the laminated substrate, and the areas where each layer is provided may be appropriately set or shaped.

[0058] The fabricated laminated substrate has a porous layer, and a perovskite precursor solution (perovskite solution 8) containing a perovskite compound is dropped onto the top of the laminated substrate and fired to produce a solar cell 10. In this embodiment, perovskite solution 8 was prepared by mixing and stirring methylamine iodide (1.14 M), lead iodide (1.2 M), 5-aminovaleric acid hydroiodide (0.06 M), and γ-butyrolactone (solvent).

[0059] The perovskite solution 8 dropped onto the laminated substrate penetrates the second conductive layer 7, the second porous layer 61, and the first porous layer 51. Since the second conductive layer 7 has a window 7a, the perovskite solution 8 can be directly dropped onto the upper surface 6a of the insulating layer, improving the penetration of the perovskite solution 8 into the first porous layer 51 and the second porous layer 61. Furthermore, in the short-side direction X, the area near the end of the insulating layer 6 that protrudes outward from the second conductive layer 7 is not covered by the second conductive layer 7 and functions similarly to the area directly below the window 7a. The perovskite solution 8 dropped onto the second conductive layer 7 also gradually seeps in from the top to the bottom of the second conductive layer 7, reaching the second porous layer 61.

[0060] Subsequently, by firing to evaporate the perovskite solution 8, light-absorbing portions are formed in the pores of the second conductive layer 7, the second porous layer 61, and the first porous layer 51. In other words, by dropping the perovskite solution 8 and firing, the first porous layer 51 is transformed into a porous electron transport layer 5, and the second porous layer 61 is transformed into an insulating layer 6.

[0061] Figure 3 is a schematic top view showing a solar cell module according to the first embodiment of this disclosure.

[0062] As shown in Figure 3, the solar cell 10 is roughly rectangular in shape, and each layer is shaped accordingly. For explanatory purposes below, the direction along the long side of the second conductive layer 7 when viewed from above may be referred to as the long side direction Y.

[0063] In this embodiment, the window portion 7a is a slit shape extending in the short-side direction X, with both ends extending to the opposing long side of the second conductive layer 7. In other words, the second conductive layer 7 is divided in the long-side direction Y by the window portion 7a, and there are portions that do not extend in the long-side direction Y. The window portion 7a only needs to be provided so as to include a portion that overlaps with the insulating layer 6 when viewed from above, and a part of it may be provided directly above the substrate 2 or the dense electron transport layer 4. In addition, the number of window portions 7a provided in one solar cell 10 can be set as appropriate, and in the configuration shown in Figure 3, window portions 7a are provided at three locations spaced apart in the long-side direction Y.

[0064] As in this embodiment, by reducing the area in which the window portion 7a is provided while maintaining a shape that allows it to function sufficiently, the characteristics of the solar cell 10 can be minimized. Furthermore, since the window portion 7a is visible when viewed from above, the shape of the window portion 7a can be appropriately designed to improve the aesthetic appearance.

[0065] Preferably, the width of the window portion 7a in the direction perpendicular to the direction of extension (short side direction X in Figure 3) (long side direction Y) is 2 μm or less. When the width of the window portion 7a is 2 μm or less, carriers (electrons) can pass through the portion corresponding to the window portion 7a, so as not to impair the characteristics of the solar cell 10.

[0066] In the solar cell module 1, multiple solar cells 10 are connected in series in a monolithic structure. Figure 3 shows a magnified view of the vicinity of some of the solar cells 10 in the solar cell module 1, and many solar cells 10 may be arranged in a row in the short side direction X. Furthermore, many more solar cells 10 may be provided on the substrate 2, and multiple rows of solar cells 10 arranged in the short side direction X may be arranged in a row in the long side direction Y.

[0067] (Second Embodiment) Next, a solar cell module 1 according to the second embodiment of this disclosure will be described with reference to the drawings. Note that the structure of the solar cell module 1 according to the second embodiment is substantially the same as that of the first embodiment shown in Figures 1A to 3; therefore, common parts are denoted by the same reference numerals and their descriptions are omitted.

[0068] Figure 4A is a schematic top view showing a solar cell module according to a second embodiment of this disclosure, and Figure 4B is a schematic cross-sectional view showing the cross-section indicated by arrow CC in Figure 4A.

[0069] The second embodiment differs from the first embodiment in the extent to which the window portion 7a extends. Specifically, the window portion 7a in this embodiment is a slit shape extending in the short-side direction X, but both ends do not reach the opposing long sides of the second conductive layer 7. In other words, the second conductive layer 7 is not completely separated in the long-side direction Y by the window portion 7a, and there are parts that do not extend in the long-side direction Y. However, the embodiment is not limited to this, and the extent to which the window portion 7a extends may be such that one end reaches the long side of the second conductive layer 7, while the other end does not reach the long side of the second conductive layer 7.

[0070] (Third embodiment) Next, a solar cell module 1 according to the third embodiment of this disclosure will be described with reference to the drawings. Note that the structure of the solar cell module 1 according to the third embodiment is substantially the same as that of the first and second embodiments shown in Figures 1A to 4B; therefore, common parts are denoted by the same reference numerals and their descriptions are omitted.

[0071] Figure 5 is a schematic top view showing a solar cell module according to the third embodiment of this disclosure.

[0072] In the third embodiment, the direction in which the window portion 7a extends is different from that of the first embodiment. Specifically, in this embodiment, the window portion 7a has a slit shape that extends in a direction inclined (intersecting) with respect to the short side direction X, and both ends extend to the opposing long side of the second conductive layer 7. In this embodiment, the range in which the window portion 7a extends may be set as appropriate, and as in the second embodiment, it may be set so that the ends do not reach the long side of the second conductive layer 7.

[0073] (Fourth Embodiment) Next, a solar cell module 1 according to the fourth embodiment of this disclosure will be described with reference to the drawings. Note that the structure of the solar cell module 1 according to the fourth embodiment is substantially the same as that of the first to third embodiments shown in Figures 1A to 5; therefore, common parts are denoted by the same reference numerals and their descriptions are omitted.

[0074] Figure 6 is a schematic top view showing a solar cell module according to the fourth embodiment of this disclosure.

[0075] The fourth embodiment differs from the first embodiment in the shape of the window portion 7a. Specifically, the window portion 7a in this embodiment has a shape that meanders in the short side direction X and extends in the long side direction Y. In other words, the window portion 7a has a slit shape that extends like a curve that bends at multiple points. By making the window portion 7a meander while changing direction in this way, the portion of the photoelectric conversion layer that is far away from the window portion 7a is reduced, and the perovskite solution 8 can permeate the entire photoelectric conversion layer. Figure 6 shows a configuration in which each solar cell 10 has one long, connected window portion 7a, but it is not limited to this, and multiple window portions 7a may be provided in one solar cell 10.

[0076] (Fifth embodiment) Next, a solar cell module 1 according to the fifth embodiment of this disclosure will be described with reference to the drawings. Note that the structure of the solar cell module 1 according to the fifth embodiment is substantially the same as that of the first to fourth embodiments shown in Figures 1A to 6; therefore, common parts are denoted by the same reference numerals and their descriptions are omitted.

[0077] Figure 7 is a schematic top view showing a solar cell module according to the fifth embodiment of this disclosure.

[0078] The fifth embodiment differs from the first embodiment in the shape of the window portion 7a. Specifically, the window portion 7a in this embodiment is shaped to resemble either letters, symbols, or patterns. In this way, patterns such as letters, symbols, and patterns can be drawn on the second conductive layer 7 by the window portion 7a, further improving the design. Multiple window portions 7a may be provided on a single solar cell 10, and multiple window portions 7a of different shapes may be combined to form, for example, a string of characters. Furthermore, each solar cell 10 may be provided with window portions 7a of different shapes.

[0079] (Sixth Embodiment) Next, a solar cell module 1 according to the sixth embodiment of this disclosure will be described with reference to the drawings. Note that the structure of the solar cell module 1 according to the sixth embodiment is substantially the same as that of the first to fifth embodiments shown in Figures 1A to 7; therefore, common parts are denoted by the same reference numerals and their descriptions are omitted.

[0080] Figure 8 is a schematic top view showing a solar cell module according to the sixth embodiment of this disclosure.

[0081] The sixth embodiment differs from the first embodiment in that the window portion 7a extends in a different direction. Specifically, the window portion 7a in this embodiment has a slit shape that extends along the long side direction Y. By having a slit-shaped window portion 7a along the long side direction Y, the portion of the photoelectric conversion layer that is far from the window portion 7a is reduced, and the perovskite solution 8 can permeate the entire photoelectric conversion layer.

[0082] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of symbols]

[0083] 1. Solar cell module 2 Base 3 Transparent electrode layer 4 Dense electron transport layer 5 Porous electron transport layer 6. Insulating layer 6a Upper surface of the insulating layer 7. Second conductive layer 7a Window section 8 Perovskite solution 10 solar cells X Short side direction Y-direction (longer side)

Claims

1. A solar cell comprising a substrate that is the light-receiving surface, in which a first conductive layer, a photoelectric conversion layer, and a second conductive layer are provided in that order, The photoelectric conversion layer includes a porous layer and a light-absorbing portion. The second conductive layer includes a porous conductive layer made of porous material, and is provided with a window portion that exposes a part of the upper surface of the photoelectric conversion layer. The window portion is a dropping window portion through which a solution is dropped onto the porous layer. A solar cell characterized by the following features.

2. A solar cell according to Claim 1, The photoelectric conversion layer includes a porous layer which is an insulating layer made of porous material, and a light absorbing portion. A solar cell characterized by the following features.

3. A solar cell according to Claim 1, The photoelectric conversion layer includes a porous layer which is an insulating layer made of porous material, and a light absorbing portion. The porous insulating layer has voids including the light-absorbing portion. A solar cell characterized by the following features.

4. A solar cell according to claim 2, The porous insulating layer excludes the porous insulating layer made of titanium oxide. A solar cell characterized by the following features.

5. A solar cell according to any one of claims 1 to 4, The second conductive layer is provided on the back side opposite to the side from which light is incident. A solar cell characterized by the following features.

6. A solar cell according to any one of claims 2 to 4, The photoelectric conversion layer includes a porous electron transport layer made of porous material. The porous insulating layer and the porous electron transport layer are arranged in a stacked manner. A solar cell characterized by the following features.

7. A solar cell according to claim 6, The porous electron transport layer contains titanium oxide, The porous insulating layer contains zirconium oxide. A solar cell characterized by the following features.

8. A solar cell according to any one of claims 2 to 4, The photoelectric conversion layer includes a hole transport layer made of fine particles, The porous insulating layer and the hole transport layer are arranged in a laminated manner. A solar cell characterized by the following features.

9. A solar cell according to any one of claims 1 to 4, The second conductive layer includes a light-absorbing portion in the void. A solar cell characterized by the following features.

10. A solar cell according to any one of claims 1 to 4, The light-absorbing portion contains a perovskite compound. A solar cell characterized by the following features.

11. A solar cell according to any one of claims 1 to 4, The light-absorbing portion includes an organic-inorganic hybrid compound. A solar cell characterized by the following features.

12. A solar cell according to any one of claims 1 to 4, When the direction along the longer side of the second conductive layer is defined as the longer side direction, The window portion has a slit shape that extends in a direction intersecting the direction of the long side. A solar cell characterized by the following features.

13. A solar cell according to any one of claims 1 to 4, When the direction along the longer side of the second conductive layer is defined as the longer side direction, The window portion has a meandering shape in a direction intersecting the direction of the long side. A solar cell characterized by the following features.

14. A solar cell according to any one of claims 1 to 4, The aforementioned window portion shall be shaped to resemble any of the letters, symbols, or patterns. A solar cell characterized by the following features.

15. A solar cell according to any one of claims 1 to 4, When the direction along the longer side of the second conductive layer is defined as the longer side direction, The window portion is shaped like a slit extending along the long side direction. A solar cell characterized by the following features.

16. A solar cell according to any one of claims 1 to 4, The window portion has a width of 2 μm or less. A solar cell characterized by the following features.

17. A solar cell module having a plurality of solar cells according to any one of claims 1 to 4, Multiple of the aforementioned solar cells are connected in series by a monolithic structure. A solar cell module characterized by the following features.

18. A method for manufacturing a solar cell, wherein a first conductive layer, a photoelectric conversion layer, and a second conductive layer are provided in order from the substrate which is the light-receiving surface, The photoelectric conversion layer includes a porous layer and a light-absorbing portion. The second conductive layer includes a porous layer made of porous material, and is provided with a window portion that exposes a part of the upper surface of the photoelectric conversion layer. The process includes forming the light-absorbing portion by dropping a solution onto the porous layer through the window portion provided in the second conductive layer. A method for manufacturing solar cells characterized by the following.

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