Solar battery cell, solar battery module, and manufacturing method for 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 and a solar module using a perovskite compound, and a method for manufacturing the same. [Background technology]

[0002] In recent years, solar cells have become popular as a way to utilize renewable energy. Solar cells using inorganic photoelectric conversion elements (e.g., silicon-based solar cells, CIGS-based solar cells, and CdTe-based solar cells) are widely used, but solar cells using organic photoelectric conversion elements (e.g., organic thin-film solar cells, dye-sensitized solar cells, and perovskite solar cells) are also being considered.

[0003] However, in solar cells formed by stacking multiple layers, it is necessary to accurately align each layer, which makes the manufacturing process complicated. Therefore, a method for simplifying the manufacturing process has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-168842 Summary of the Invention [Problem to be solved by the invention]

[0005] A conventional solar cell module is a multilayer structure in which at least two solar cells are deposited on a substrate having a downweb direction and a crossweb direction, the multilayer structure including: a first electrode strip disposed on the substrate, extending along the crossweb direction, and forming a layer of a first conductive material; an insulating strip disposed on the layer of first conductive material, defining a connection region and an active region, and formed of an insulating material, extending along the downweb direction; a functional stack disposed on the layer of first conductive material and within the active region, including a layer of photoactive semiconductor material coated over the entire web; a second electrode strip disposed within the functional stack and the active region, extending in the crossweb direction, and aligned with the first electrode strip to form a solar cell; and an electrical connection pattern extending over the insulating strip for electrically connecting the second electrode strip of any solar cell to the first electrode strip of an adjacent solar cell within the connection region.

[0006] When manufacturing perovskite solar cells, a process is carried out in which a perovskite solution is permeated into a porous layer provided below an electrode. However, when the porous layer is covered by an electrode, as in conventional solar cell modules, there is an issue in that it is difficult for the perovskite solution to reach the porous layer.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a solar cell and a solar cell module with improved permeability of a perovskite solution, and a method for manufacturing the same. [Means for solving the problem]

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

[0009] In the solar cell according to the present disclosure, the light absorbing portion may include a perovskite compound.

[0010] In the solar cell according to the present disclosure, the light absorbing portion may include an organic-inorganic hybrid compound.

[0011] The solar cell according to the present 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 extending in a direction intersecting the long side direction.

[0012] The solar cell according to the present 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 serpentine shape in a direction intersecting the long side direction.

[0013] In the solar cell according to the present disclosure, the window portion may be configured to have a shape that resembles any one of a letter, a symbol, and a pattern.

[0014] The solar cell according to the present 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 extending along the long side direction.

[0015] In the solar cell according to the present disclosure, the window portion may have a width of 2 μm or less.

[0016] In the solar cell according to the present 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 according to the present disclosure is a solar cell module having a plurality of solar cells according to the present 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 the steps of providing, in order from a base, a first conductive layer, a photoelectric conversion layer, and a second conductive layer, the photoelectric conversion layer including a porous layer and a light absorbing portion, and the second conductive layer having a window portion that exposes a portion of the upper surface of the photoelectric conversion layer. [Effects of the Invention]

[0019] According to the present disclosure, the second conductive layer has a window, which allows the perovskite solution to be dripped directly onto the upper surface of the photoelectric conversion layer, improving permeability. Furthermore, since the window is visible when viewed from above, the shape of the window can be appropriately designed to improve design. [Brief explanation of the drawings]

[0020] [Figure 1A] 1 is a schematic cross-sectional view (part 1) illustrating a solar cell according to an embodiment of the present disclosure. [Figure 1B] FIG. 2 is a schematic cross-sectional view (part 2) illustrating a solar cell according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a step of dripping a perovskite solution in a method for manufacturing a solar cell. [Figure 3] 1 is a schematic top view showing a solar cell module according to a first embodiment of the present disclosure. [Figure 4A] FIG. 4 is a schematic top view showing a solar cell module according to a second embodiment of the present disclosure. [Figure 4B] FIG. 4B is a schematic cross-sectional view showing a cross section taken along the arrow CC in FIG. 4A. [Figure 5] FIG. 10 is a schematic top view showing a solar cell module according to a third embodiment of the present disclosure. [Figure 6] FIG. 10 is a schematic top view showing a solar cell module according to a fourth embodiment of the present disclosure. [Figure 7] FIG. 10 is a schematic top view showing a solar cell module according to a fifth embodiment of the present disclosure. [Figure 8] FIG. 10 is a schematic top view showing a solar cell module according to a sixth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] (First embodiment) A solar cell and a solar cell module according to a first embodiment of the present disclosure will be described below with reference to the drawings.

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

[0023] As shown in FIG. 1B , a solar cell 10 according to the first embodiment of the present disclosure includes 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 portion in this embodiment), and a second conductive layer 7 stacked on a substrate 2. A solar cell module 1 is configured by connecting a plurality of solar cells 10 in series on the substrate 2. For ease of explanation, 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). The following description focuses on one of the plurality of solar cells 10 (the right-hand solar cell 10 in FIG. 1A or 1B, etc.), and the remaining solar cells 10 (such as the left-hand solar cell 10 in FIG. 1A or 1B, etc.) may be referred to as adjacent solar cells 10.

[0024] The base 2 is the base of the solar cell 10 and may be the same as or include the substrate or base material. It may be hard and highly rigid, or it may be flexible or have low rigidity. The base 2 may be, for example, flat or film-like in shape. When light is irradiated (light is incident) on the surface of the solar cell 10 facing the base 2 (the lower surface of the base 2 in FIG. 1A), i.e., when the side facing the base 2 is the light-receiving surface, the base 2 is preferably transparent. In this case, examples of materials for the base 2 include glass and heat-resistant transparent resins. When light is irradiated from the opposite side, the base 2 may be opaque. While "transparent" means that light is transmitted through the base 2, this does not exclude materials that reflect or absorb light even slightly. It is sufficient for the base 2 to transmit light appropriately, and this can be considered synonymous with being located on the light-receiving surface side of the solar cell (including the portion where light is incident, as in the present disclosure). Therefore, a material can be considered transparent simply by being located on at least the light-receiving surface side of the solar cell.

[0025] The first conductive layer, i.e., 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 photovoltaic power from the solar cell 10. The transparent electrode layer 3 is divided into multiple island-like layers spaced apart in the short side direction X. The transparent electrode layer 3 is formed of a transparent conductive material, 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 (antimony-doped tin oxide), or a conductive transparent polymer. Note that the chemical formulas are representative examples and may be compound names (as in the present disclosure). Furthermore, while it is desirable for the composition ratio of the chemical formula to be stoichiometric, it does not necessarily have to be stoichiometric (as in the present disclosure). The transparent electrode layer 3 may be configured such that a conductive metal such as silver or thin wires thereof are formed on an oxide film of a conductive transparent material or the like. The term "film" does not specify thickness or width, and includes patterned or island-shaped films and films with portions of different thicknesses. Preferably, the film has a substantially constant thickness. Unless otherwise specified, "approximately" or "approximately" refers to the range of manufacturing error, and preferably indicates that a variation of plus or minus 15% of the numerical value is allowed.

[0026] The dense electron transport layer 4 is a layer capable of transporting electrons generated in the light absorbing portion (e.g., a perovskite compound). The dense electron transport layer 4 naturally has this function as long as the solar cell has a photoelectric conversion function, and it can be considered synonymous with being disposed on the electron transport side of the light absorbing portion of the solar cell. Therefore, as long as it is disposed at least on the electron transport side of the perovskite compound, it can be said to have an electron transport function. The dense electron transport layer 4 preferably has a function of blocking hole transport. The dense electron transport layer 4 is dense. Details of the dense material will be 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 in which liquid hardly penetrates into the dense layer even when dropped onto the dense layer. In this embodiment, the dense electron transport layer 4 is formed of titanium oxide or tin oxide. The dense electron transport layer 4 is provided over the transparent electrode layer 3 and is not present on the substrate 2 .

[0027] The term "layer" does not specify thickness or width, and includes a pattern or island shape, or a layer having portions of different thickness. A layer is preferably a member having a substantially constant thickness.

[0028] Dense matter may also be called compact, compact substance, etc., and may be the same as or include these.

[0029] Porous may be referred to as porous or mesoporous, and may be the same as or include these. In the present disclosure, porous means that light-absorbing portions (for example, perovskite compounds) can be contained in voids (which can be variously expressed as gaps, holes, or holes). 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 disposed on one side (for example, the lower side) of the porous layer in the thickness direction, and an insulating layer is disposed on the opposite side (for example, the upper side). The porous layer may also include a second conductive layer.

[0030] Furthermore, a dense material refers to a material having extremely small voids. That is, in the present disclosure, a dense material refers to a material that can be observed such that no light-absorbing portion (in this embodiment, as an example, a perovskite compound, hereinafter referred to as a perovskite compound) is present on one side (for example, the lower side) of the dense material in the thickness direction. That is, even if a perovskite compound is present on the upper side of the dense material, it is possible to ensure that it does not penetrate to the lower side of the dense material. Preferably, a dense material refers to a material having extremely small voids. Preferably, a dense material refers to a material in which the maximum void width is less than 5 nm. Preferably, a dense material is one that suppresses the penetration of the perovskite compound, and is capable of being free of the perovskite compound on one side of the dense material in the thickness direction. More preferably, a dense material refers to a material that cannot contain a perovskite compound in the voids or does not have a portion where the perovskite compound is continuously present throughout the thickness of the dense material. That is, when a dense material cannot be confirmed by the maximum width of the voids it has, it is sufficient if observation by SEM or EDX reveals that there are no portions where the perovskite compound exists throughout the layer thickness. In the present disclosure, unless otherwise stated, SEM observation should be performed on a 400 nm wide cross-sectional SEM (or EDX) image and confirmed. For example, if observation by SEM or EDX of a single 400 nm wide cross-section reveals no portions where the perovskite compound exists throughout the layer thickness, the layer can be said to be dense.

[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 absorbing section to the electrode. Examples of materials that can be used for the porous electron transport layer 5 include titanium oxide, tin oxide, and aluminum oxide. Furthermore, an n-type inorganic oxide is suitable for the porous electron transport layer 5. As already described in detail, a porous layer preferably has numerous pores within the layer, and these pores are interconnected. Because of its porosity, when a liquid (with good wettability) is dropped onto the porous layer (with hollow pores), the liquid can permeate the porous layer. Like the dense electron transport layer 4, the porous electron transport layer 5 is also a layer capable of transporting electrons generated in the perovskite compound. Naturally, the porous electron transport layer 5 also functions as a solar cell. That is, as long as it is disposed on the electron transport side (or negative electrode side, as in the present disclosure) of the perovskite compound of the solar cell, it can be considered to have the electron transport function. The porous electron transport layer 5 may preferably be a mesoporous layer. Furthermore, it is even more preferable if the porous electron transport layer 5 is a mesoporous nanocrystalline layer.

[0032] In this embodiment, the porous electron transport layer 5 is provided on the dense electron transport layer 4, in an area narrower in the short side direction X than the dense electron transport layer 4. Therefore, there is a region on the upper surface of the dense electron transport layer 4 that is not covered with the porous electron transport layer 5. The porous electron transport layer 5 is also disposed near the end of the dense electron transport layer 4 in the short side direction X (the right end in FIG. 1A ).

[0033] In this embodiment, the dense electron transport layer 4 is disposed on the transparent electrode layer 3 with the same width (width in the short side direction X in FIG. 1B), but the width does not necessarily have to be the same. At the end in the short side direction X (left end in FIG. 1B), a part of the transparent electrode layer 3 may be formed so as to be exposed and not covered by the dense electron transport layer 4. This improves the electrical connection between the transparent electrode layer 3 of the solar cell (the solar cell on the right in FIG. 1B) and the second conductive layer 7 of the adjacent solar cell (the solar cell on the left in FIG. 1B).

[0034] The insulating layer 6 is made of a porous material. Examples of materials for the insulating layer 6 include metal oxides, such as titanium oxide, zirconium dioxide, and aluminum oxide, and oxides, such as silicon dioxide. Note that insulation does not necessarily have to completely prevent charge transfer; it is acceptable for the thickness and structure of the insulating layer to suppress, but not completely prevent, charge transfer. 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), thereby reducing physical contact between the materials on both sides and suppressing the recombination of electrons and holes generated in the light-absorbing region. In other words, adding an insulating layer improves the performance of solar cells and contributes to achieving commercialized 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) and contributes to increasing the distance between the two sides. As a result, it is sufficient to confirm the physical properties of the insulating layer if the solar cell is commercialized; it is not necessary to verify the insulating performance. The insulating layer 6 is a porous layer containing voids, and preferably has a large number of voids with a size of 20 nm or more. In other words, the insulating layer 6 is occupied by, for example, the metal oxide that constitutes the insulating layer 6 itself and the voids that 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 set to include these small voids. Furthermore, 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 provided on the porous electron transport layer 5 and has 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 FIG. 1A ) covers part of the upper surface of the dense electron transport layer 4, and the other end of the insulating layer 6 in the short side direction X (the right end in FIG. 1A ) protrudes outside the dense electron transport layer 4 and covers the side surfaces of the transparent electrode layer 3 and 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 the dense electron transport layer 4 of the adjacent solar cell 10 and is separated therefrom.

[0036] The second conductive layer 7 is a conductive member. It functions as an electrode for extracting photovoltaic power from the solar cell 10. It has the function of collecting photoexcited holes in the light absorbing portion and is preferably formed of a porous carbon material. The second conductive layer 7 is provided in a range where it partially 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 FIG. 1B ) does not reach the end of the insulating layer 6, exposing a portion of the upper surface of the insulating layer 6 (the upper surface 6a of the insulating layer). The other end of the second conductive layer 7 in the short side direction X (the right end in FIG. 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, the end of the second conductive layer 7 contacts the dense electron transport layer 4 of the adjacent solar cell 10, electrically connecting the adjacent solar cell 10.

[0037] The second conductive layer 7 can be, for example, a metal film with a work function of 5 eV or more. By using a metal with a high work function (5 eV or more) for the second conductive layer 7, a bending of the band structure that allows holes to flow smoothly is easily generated at the interface between the second conductive layer and the light absorbing layer or the light absorbing section or the layer on the light absorbing section side. The second conductive layer 7 can be made of, for example, metals such as Ni, Pt, and Pd. The thickness of the second conductive layer 7 is preferably about 50 nm to 150 nm. The second conductive layer 7 can be formed by, for example, a sputtering method or a vacuum deposition method. Alternatively, conductive carbon materials such as graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon black can be used. Basically, any conductive material can be used.

[0038] The second conductive layer 7 has a window 7a that exposes a portion of the upper surface 6a of the insulating layer. The window 7a is provided in a region that overlaps at least a portion of the insulating layer 6, and the upper surface 6a of the insulating layer is exposed in the region where the window 7a is provided. That is, as shown in FIG. 1A, which is a schematic cross-sectional view taken along arrow AA of the portion where the window 7a is formed in FIG. 3, the second conductive layer 7 is removed in the region where the window 7a is provided, exposing the upper surface 6a of the insulating layer. In contrast, in FIG. 1B, which is a schematic cross-sectional view taken along arrow BB of the portion where the window 7a is not formed in FIG. 3, the second conductive layer 7 is formed because the window 7a is not provided, and the portion of the upper surface 6a of the insulating layer where the second conductive layer 7 is formed is covered by the second conductive layer 7. The window 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 7a when viewed from above will be described with reference to FIG. 3 below.

[0039] The light-absorbing portion described above includes a perovskite compound. In this embodiment, the porous electron transport layer 5, the insulating layer 6, and the second conductive layer 7 also contain light-absorbing portions. That is, the light-absorbing portions are disposed in the voids (which can also be variously expressed as gaps, holes, or cavities) of these layers. Preferably, these layers are filled with light-absorbing portions. The voids in the porous electron transport layer 5, the insulating layer 6, and the second conductive layer 7 are desirably 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 charges are separated. As long as the solar cell has a photoelectric conversion function, it can be confirmed that electrons and holes are generated by light absorption in areas containing appropriate materials. There is no need to confirm the photoelectric conversion properties of the light-absorbing portion to confirm that it is a light-absorbing portion.

[0040] The light-absorbing portion refers to a specific portion (e.g., a certain portion of a perovskite compound) that absorbs light, and these portions can be collectively referred to as a light-absorbing layer. Here, the light-absorbing portion can refer to a portion that is a specific region in the light-absorbing layer. Furthermore, the light-absorbing layer can refer to a collection of light-absorbing portions that exist discretely in a region having a thickness (which does not need to be constant) in a specific direction.

[0041] The perovskite compound contained in the light-absorbing portion is composed of a compound represented by the general formula: ABX3 (1). While the composition ratio of each element is preferably 1:1:3, it does not necessarily have to be 1:1:3. The content ratio of each element may vary as appropriate, and each element does not necessarily have to be a single type. As long as the light-absorbing portion has a photoelectric conversion function, the perovskite compound contained in the light-absorbing portion exhibits the photoelectric conversion function. Therefore, even if there is a degree of freedom in the composition as described above regarding the composition ratio and the type of constituent elements, it is reasonable to consider that the function is exhibited. In general formula (1), A is an organic molecule (including an organic group or an organic cation, as defined herein), an inorganic atom or molecule (including an inorganic group or an inorganic cation, as defined herein), or a combination thereof; B is a metal atom or molecule (including a metal cation, as defined herein); and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion, as defined herein). In general formula (1), the three Xs may be the same or different. As long as a solar cell has a photoelectric conversion function, the perovskite compound contained in the light absorbing portion exhibits the photoelectric conversion function, and this should be taken into consideration. That is, if it is confirmed that a compound is a perovskite compound, it is reasonable to consider it a perovskite compound exhibiting a photoelectric conversion function. For example, it is sufficient to know that it contains organic molecules, metal atoms, and halogen atoms. Furthermore, as long as a solar cell has a photoelectric conversion function, it is sufficient to confirm that it is a perovskite compound if elements corresponding to A, B, and X are detected. For example, molecules containing carbon, nitrogen, and hydrogen are suitable as organic molecules, and therefore it is sufficient to detect carbon, nitrogen, hydrogen, a metal element, and a halogen or chalcogen. Alternatively, it is sufficient to confirm that a compound is a perovskite compound if it contains A, B, and X. For example, it is sufficient to confirm that it contains inorganic atoms, metal atoms, and halogen atoms. Furthermore, the perovskite compound can be confirmed if elements corresponding to A, B, and X are detected, so long as the solar cell has a photoelectric conversion function.For example, cesium or rubidium is suitable as the inorganic atom, and therefore, it is sufficient to detect cesium or rubidium, a metal element, and a halogen or chalcogen. Furthermore, since it is a natural consequence that a solar cell has a crystalline structure as long as it has a photoelectric conversion function, it is not necessary to confirm that the compound is a perovskite compound. This does not exclude the inclusion of compounds other than perovskite compounds in the light-absorbing portion.

[0042] The light absorbing portion may contain an organic-inorganic hybrid compound. An organic-inorganic hybrid compound refers to a compound containing an inorganic material and an organic material. Organic-inorganic hybrid compounds also include perovskite compounds, and solar cells using perovskite compounds are also called organic-inorganic hybrid solar cells. "Organic" typically refers to a material composed of multiple carbon atoms. Note that graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon materials such as carbon and carbon black that function as electrodes are not considered to be organic materials. In other words, organic refers to a material that contains multiple carbon atoms as one of its constituent elements, excluding the above-mentioned carbon materials such as graphite. "Inorganic" refers to a material that is not organic.

[0043] The light-absorbing portion may contain quantum dots. Quantum dots refer to dots with a maximum width of 100 nm or less. The shape of the quantum dots is not particularly limited as long as it satisfies the above-mentioned maximum width, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). For example, they may have a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with an uneven surface, or a combination thereof. The quantum dots are typically made of a semiconductor. The semiconductor may be any material capable of absorbing light and may include at least the materials described below. The semiconductor may include, for example, at least one selected from the group consisting of II-VI group compounds, III-V group compounds, chalcogenides, and perovskite compounds. The II-VI group compounds refer to compounds containing II and VI elements, and the III-V group compounds refer to compounds containing III and V elements. Furthermore, Group II elements may include Group 2 and Group 12 elements, Group III elements may include Group 3 and Group 13 elements, Group V elements may include Group 5 and Group 15 elements, and Group VI elements may include Group 6 and Group 16 elements. Here, the numbering of element groups using Roman numerals is based on the old IUPAC system or the old CAS system, and the numbering of element groups using Arabic numerals is based on the current IUPAC system. The semiconductor may 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] In the general formula (1), examples of the organic molecule represented by A include alkylamine, alkylammonium, and nitrogen-containing heterocyclic compounds. In the perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or 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] The alkylammonium is an ionized product of the alkylamine. Examples of the alkylammonium 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 the nitrogen-containing heterocyclic compound include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. The nitrogen-containing heterocyclic compound may be an ionized compound. As the ionized nitrogen-containing heterocyclic compound, phenethylammonium is preferred.

[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 the metal atom 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 the perovskite compound, the metal atom represented by B may be only one type of metal atom, or may be two or more types of metal atoms. From the viewpoint of improving the light absorption properties and charge generation properties of the perovskite compound, the metal atom represented by B is preferably a lead atom or a tin atom. From the viewpoint of reducing lead, a tin atom is preferred.

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

[0051] The perovskite compound is preferably a compound represented by the general formula "CH3NH3PbX3 (wherein X represents a halogen atom)", and more preferably CH3NH3PbI3. By using a compound represented by the general formula "CH3NH3PbX3" (particularly 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] The photoelectric conversion layer is a layer that converts light into electricity. It can include a porous layer and a light-absorbing portion, and refers to a layer located between the first and second conductive layers. The light-absorbing portion is often located between the first and second conductive layers. In such cases, 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 porous, the light-absorbing portion may be present in the area including the first and second conductive layers themselves. In such cases, the first and second conductive layers themselves, where the light-absorbing portion is located, can also be considered as the photoelectric conversion layer. Even in such cases, the photoelectric conversion layer is located at least between the first and second conductive layers. In other words, in any case, 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. This does not exclude the first and second conductive layers from being included in the photoelectric conversion layer themselves, nor does it exclude the photoelectric conversion layer being present in areas other than between the first and second conductive layers.

[0053] In this embodiment, a hole transport layer (same as the hole transport layer) may be disposed between the perovskite compound, which is the light absorbing section, and the second conductive layer 7. The hole transport layer has the function of transporting holes generated in the light absorbing section to the second conductive layer 7. It is self-evident that, as long as a solar cell has a photoelectric conversion function, a hole transport layer located on the hole transport side of the light absorbing section or on the hole transport side of the light absorbing section has a hole transport function, and no confirmation is required. In other words, as long as the solar cell functions as a solar cell, a layer located on the hole transport side of the light absorbing section (or on the positive electrode side, similarly in this disclosure) or on the hole transport side of the light absorbing section is referred to as a hole transport layer. The hole transport layer may be made of, for example, a material having a band gap of 2 eV or more and an ionization potential smaller (shallower) than 5.4 eV. The hole transport layer may be made of an inorganic material. The thickness of the hole transport layer may be, for example, approximately 30 nm or more and 100 nm or less. Specific materials constituting the hole transport layer include oxides and sulfides such as copper oxide (CuO), zinc sulfide (ZnS), and nickel oxide. Fine particles of oxides or sulfides may also be used. Organic materials may also be used. The hole transport layer may be capable of inhibiting electron transport (electron blocking). The hole transport layer may also be accompanied by a separate electron blocking layer. Alternatively, there may be no hole transport layer, and an electron blocking layer may be used instead.

[0054] Next, a method for manufacturing the solar cell 10 will be described with reference to FIG.

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

[0056] Fig. 2 shows a schematic cross section of a portion corresponding to the window portion 7a of a solar cell 10 (solar cell module 1) during the step of dripping the perovskite solution 8. The first porous layer 51 in Fig. 2 corresponds to the porous electron transport layer 5 before dripping the perovskite solution 8, and the second porous layer 61 in Fig. 2 corresponds to the insulating layer 6 before dripping the perovskite solution 8.

[0057] When fabricating the solar cell 10, a laminated substrate is first fabricated using a typical photolithography process, screen printing process, or the like, in which the portions where each layer of the solar cell 10 will be provided are appropriately set. Specifically, a glass substrate having a fluorine-doped tin oxide film was used for the substrate 2 and the transparent electrode layer 3. A titanium oxide dense layer (dense electron transport layer 4) was then formed on the fluorine-doped tin oxide film using a spray pyrolysis method. Next, a titanium oxide paste was applied to the titanium oxide dense layer and dried to form a titanium oxide porous layer (first porous layer 51). Next, a zirconium dioxide paste was applied to the titanium oxide porous layer and dried to form a zirconium dioxide porous layer (second porous layer 61). Next, a carbon paste was applied to the zirconium dioxide porous layer and dried to form a carbon porous layer (second conductive layer 7). As described above, a photolithography step or a screen printing step may be performed between steps of forming each layer in the laminated substrate, and the portion where each layer is to be 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 dripped onto the laminated substrate from above and baked to fabricate a solar cell 10. In this embodiment, the 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 permeates the second conductive layer 7, the second porous layer 61, and the first porous layer 51. Because the second conductive layer 7 has the window 7a, the perovskite solution 8 can be dropped directly onto the insulating layer upper surface 6a, improving the permeability of the perovskite solution 8 into the first porous layer 51 and the second porous layer 61. The vicinity of the end of the insulating layer 6 that protrudes outward beyond the second conductive layer 7 in the short-side direction X is not covered by the second conductive layer 7 and functions similarly to the portion directly below the window 7a. The perovskite solution 8 dropped onto the second conductive layer 7 also gradually permeates from the top to the bottom of the second conductive layer 7, reaching the second porous layer 61.

[0060] Thereafter, firing is performed to evaporate the perovskite solution 8, thereby forming light absorbing portions in the pores of the second conductive layer 7, the second porous layer 61, and the first porous layer 51. In other words, by undergoing the steps of dropping the perovskite solution 8 and firing, the first porous layer 51 is transformed into the porous electron transport layer 5, and the second porous layer 61 is transformed into the insulating layer 6.

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

[0062] 3, the solar cell 10 has a substantially rectangular shape, and each layer has a corresponding shape. For ease of explanation 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 has a slit shape extending in the short side direction X, and extends so that both ends reach the opposing long sides 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 portion of the window portion 7a may be provided directly on the base 2 or the dense electron transport layer 4. The number of window portions 7a provided in one solar cell 10 may be set as appropriate, and in the configuration shown in FIG. 3, the window portions 7a are provided at three locations spaced apart in the long side direction Y.

[0064] As in the present embodiment, by reducing the area where the window portion 7a is provided while giving it a shape that allows it to fully exhibit its functionality, it is possible to minimize the impairment of the characteristics of the solar cell 10. Furthermore, because the window portion 7a can be seen when viewed from above, the shape of the window portion 7a can be designed appropriately to improve the design.

[0065] The width of the window portion 7a in the direction (long side direction Y) perpendicular to the extending direction (short side direction X in FIG. 3) is preferably 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, and the characteristics of the solar cell 10 can be prevented from being impaired.

[0066] In the solar cell module 1, the plurality of solar cells 10 are connected in series in a monolithic structure. Note that Fig. 3 shows an enlarged view of the vicinity of some of the solar cells 10 in the solar cell module 1, and many more solar cells 10 may be arranged in the short side direction X. Furthermore, even more solar cells 10 may be provided on the base 2, and multiple rows of solar cells 10 arranged in the short side direction X may be arranged in the long side direction Y.

[0067] (Second embodiment) Next, a solar cell module 1 according to a second embodiment of the present 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, and therefore the same reference numerals are used for common parts, and description thereof will be omitted.

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

[0069] The second embodiment differs from the first embodiment in the range over which the window portion 7a extends. Specifically, the window portion 7a in this embodiment has 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 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. However, the present invention is not limited to this, and the range over which the window portion 7a extends may be such that one end reaches the long side of the second conductive layer 7 and 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 a third embodiment of the present 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, and therefore the same reference numerals are used for common parts, and description thereof will be omitted.

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

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

[0073] (Fourth embodiment) Next, a solar cell module 1 according to a fourth embodiment of the present 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, and therefore the same reference numerals are used for common parts, and description thereof will be omitted.

[0074] FIG. 6 is a schematic top view showing a solar cell module according to a fourth embodiment of the present 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. That is, the window portion 7a has a slit shape that extends like a curve that bends at multiple points. By providing the window portion 7a with a meandering shape that changes direction in this way, the portion of the photoelectric conversion layer that is far away from the window portion 7a can be reduced, and the perovskite solution 8 can be permeated throughout the photoelectric conversion layer. While FIG. 6 shows a configuration in which one long, continuous window portion 7a is provided for each solar cell 10, this is not limiting, and one solar cell 10 may have multiple window portions 7a.

[0076] (Fifth embodiment) Next, a solar cell module 1 according to a fifth embodiment of the present 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, and therefore the same reference numerals are used for common parts, and description thereof will be omitted.

[0077] FIG. 7 is a schematic top view showing a solar cell module according to a fifth embodiment of the present 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 any one of letters, symbols, and patterns. In this way, designs such as letters, symbols, and patterns can be drawn on the second conductive layer 7 through the window portion 7a, further improving the design. A single solar cell 10 may have a plurality of window portions 7a, or a plurality of window portions 7a with different shapes may be combined to form, for example, a character string. Furthermore, each solar cell 10 may have a window portion 7a with a different shape.

[0079] (Sixth embodiment) Next, a solar cell module 1 according to a sixth embodiment of the present 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, and therefore the same reference numerals are used for common parts, and description thereof will be omitted.

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

[0081] The sixth embodiment differs from the first embodiment in the direction in which the window portions 7a extend. Specifically, the window portions 7a in this embodiment are slit-shaped and extend along the long side direction Y. By providing the window portions 7a with slit shapes that extend along the long side direction Y in this manner, the portions of the photoelectric conversion layer that are far away from the window portions 7a are reduced, and the perovskite solution 8 can be permeated throughout the photoelectric conversion layer.

[0082] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [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 Top surface of insulating layer 7 Second conductive layer 7a Window 8 Perovskite solution 10 solar cells X Short Side Direction Y Long side direction

Claims

1. A solar cell including a base, a first conductive layer, a photoelectric conversion layer, and a second conductive layer provided in this order, the photoelectric conversion layer includes a porous layer and a light absorbing portion, The second conductive layer has a window portion that exposes a part of the upper surface of the photoelectric conversion layer. A solar cell characterized by:

2. The solar cell according to claim 1 , The light absorbing portion contains a perovskite compound. A solar cell characterized by:

3. The solar cell according to claim 1 , The light absorbing portion contains an organic-inorganic hybrid compound. A solar cell characterized by:

4. The solar cell according to claim 1 , When the direction along the long side of the second conductive layer is defined as the long side direction, The window portion is formed in a slit shape extending in a direction intersecting with the long side direction. A solar cell characterized by:

5. The solar cell according to claim 1 , When the direction along the long side of the second conductive layer is defined as the long side direction, The window portion has a serpentine shape in a direction intersecting with the long side direction. A solar cell characterized by:

6. The solar cell according to claim 1 , The window portion is shaped to resemble any one of letters, symbols, and patterns. A solar cell characterized by:

7. The solar cell according to claim 1 , When the direction along the long side of the second conductive layer is defined as the long side direction, The window portion is formed in a slit shape extending along the long side direction. A solar cell characterized by:

8. The solar cell according to claim 1 , The window has a width of 2 μm or less. A solar cell characterized by:

9. The solar cell according to claim 1 , the photoelectric conversion layer includes a stacked electron transport layer and an insulating layer, The electron transport layer and the insulating layer have a porous structure having voids containing the perovskite compound. A solar cell characterized by:

10. A solar cell module having a plurality of solar cells according to claim 1, The plurality of solar cells are connected in series by a monolithic structure. A solar cell module characterized by:

11. The method includes providing a first conductive layer, a photoelectric conversion layer, and a second conductive layer in this order from a substrate; the photoelectric conversion layer includes a porous layer and a light absorbing portion, The second conductive layer has a window portion that exposes a part of the upper surface of the photoelectric conversion layer. A method for manufacturing a solar cell, comprising:

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