Solar cell

Abstract

A solar cell 100 has a first electrode 10, a hole transport layer 20, a photoelectric conversion layer 30 containing a perovskite compound, an electron transport layer 40, and a second electrode 50 in this order. At least one of the hole transport layer 20 and the electron transport layer 40 is formed with two layers, and at least one of the two layers is partially provided with an opening.

Description

solar cells

[0001] The present disclosure relates to a solar cell having, in this order, a first electrode, a hole transport layer, a photoelectric conversion layer containing a perovskite compound, an electron transport layer, and a second electrode.

[0002] BACKGROUND ART In recent years, solar cells (solar cell modules) have become increasingly popular as a method for utilizing renewable energy.

[0003] As solar cells, in addition to silicon solar cells that use a crystalline silicon substrate in the photoelectric conversion section, perovskite solar cells in which a perovskite compound is contained in the photoelectric conversion layer, as disclosed in Patent Document 1, are known.

[0004] In order to improve the performance of such solar cells, in conventional silicon solar cells, a passivation layer is provided on the back side of the light-receiving surface of the solar cell (PERC (Passivated Emitter and Rear Cell) technology) to suppress power generation loss caused by recombination of holes and electrons.

[0005] However, the resistance of the photoelectric conversion layer (layer containing a perovskite compound) of a perovskite solar cell is much higher than the resistance of the photoelectric conversion layer in a silicon solar cell, and electrons and holes cannot move in a direction along the layers in the hole transport layer, photoelectric conversion layer, and electron transport layer, resulting in an extreme drop in power generation efficiency. Therefore, there has been a problem in that the PERC technology used in silicon solar cells cannot be simply applied to perovskite solar cells.

[0006] Japanese Patent Application Laid-Open No. 2021-77788

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a solar cell that can achieve low resistance while improving open circuit voltage (Voc) by configuring each of the hole transport layer and the electron transport layer with multiple layers.

[0008] In order to achieve the above-mentioned object, the solar cell according to the present disclosure is a solar cell having, in this order, a first electrode, a hole transport layer, a photoelectric conversion layer containing a perovskite compound, an electron transport layer, and a second electrode, wherein at least one of the hole transport layer and the electron transport layer is composed of two layers, and at least one of the two layers has an opening partially formed therein.

[0009] According to the above-described configuration, the front and back surfaces of the photoelectric conversion layer are covered with the first and second electrodes, allowing holes and electrons to move in the direction along the hole transport layer, photoelectric conversion layer, and electron transport layer in the first and second electrodes, thereby avoiding a decrease in efficiency. Furthermore, by forming the hole transport layer or electron transport layer into a two-layer structure, one of the two layers can function as an intervening layer that suppresses recombination of electrons and holes. Since the recombination of holes and electrons generated in the photoelectric conversion layer is suppressed in the intervening layer, the open-circuit voltage (Voc) can be improved. Furthermore, since the intervening layer has openings in some parts, the resistance can be lower than when the intervening layer does not have openings, ensuring a sufficient current.

[0010] The intermediate layer may be any layer that has the function of suppressing the recombination of electrons and holes, and may be formed using, for example, known layers such as hole transport layers, electron transport layers, hole blocking layers, and electron blocking layers (hereinafter referred to as intermediate layers) and known materials used therein.

[0011] While the use of passivation layers in conventional solar cells is not excluded, given that their use may hinder proper movement of electrons and holes, the use of the intermediate layer may result in higher efficiency than the use of the passivation layer.

[0012] In this disclosure, unless otherwise specified, a layer or film is not necessarily limited to a layer having a constant thickness or width, and may include layers having portions of different thicknesses, or layers having a pattern or island shape. Preferably, a layer or film has a substantially constant thickness. Unless otherwise specified, the terms "substantially" and "approximately" refer to the range of manufacturing error, and preferably allow for a variation of plus or minus 15% of the numerical value.

[0013] The present disclosure may be characterized in that the hole transport layer is composed of a first hole transport layer and a second hole transport layer, the electron transport layer is composed of a first electron transport layer and a second electron transport layer, and the openings are provided in the second hole transport layer and the second electron transport layer.

[0014] According to the above-described configuration, the hole transport layer has a two-layer structure of a first hole transport layer and a second hole transport layer, and the electron transport layer has a two-layer structure of a first electron transport layer and a second electron transport layer, and both the second hole transport layer and the second electron transport layer function as intervening layers that suppress recombination of electrons and holes. This makes it possible to further improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the presence of openings in the second hole transport layer and the second electron transport layer.

[0015] In the present disclosure, the second hole transport layer may be provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer may be provided between the first electron transport layer and the photoelectric conversion layer.

[0016] In the present disclosure, the second hole transport layer may be provided between the first electrode and the first hole transport layer, and the second electron transport layer may be provided between the second electrode and the first electron transport layer.

[0017] In the present disclosure, the hole transport layer may be composed of a first hole transport layer and a second hole transport layer, and the opening may be provided in the second hole transport layer.

[0018] According to the above-described configuration, the hole transport layer has a two-layer structure of the first hole transport layer and the second hole transport layer, and the second hole transport layer functions as an intervening layer that suppresses recombination of electrons and holes. This makes it possible to further improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the openings provided in the second hole transport layer.

[0019] In the present disclosure, the second hole transport layer may be provided between the first hole transport layer and the photoelectric conversion layer.

[0020] In the present disclosure, the second hole transport layer may be provided between the first electrode and the first hole transport layer.

[0021] In the present disclosure, the electron transport layer may be composed of a first electron transport layer and a second electron transport layer, and the opening may be provided in the second electron transport layer.

[0022] According to the above-described configuration, the electron transport layer has a two-layer structure of the first electron transport layer and the second electron transport layer, and the second electron transport layer functions as an intervening layer that suppresses recombination of electrons and holes. This makes it possible to further improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the openings provided in the second electron transport layer.

[0023] In the present disclosure, the second electron transport layer may be provided between the first electron transport layer and the photoelectric conversion layer.

[0024] In the present disclosure, the second electron transport layer may be provided between the second electrode and the first electron transport layer.

[0025] In the present disclosure, the hole transport layer may be composed of a first hole transport layer and a second hole transport layer, the electron transport layer may be composed of a first electron transport layer and a second electron transport layer, the openings may be provided in the first hole transport layer and the second hole transport layer and the first electron transport layer and the second electron transport layer, the openings provided in the second hole transport layer may be provided at positions that do not overlap with the openings provided in the first hole transport layer, and the openings provided in the second electron transport layer may be provided at positions that do not overlap with the openings provided in the first electron transport layer.

[0026] According to the above-described configuration, the hole transport layer has a two-layer structure of a first hole transport layer and a second hole transport layer, and the electron transport layer has a two-layer structure of a first electron transport layer and a second electron transport layer, with one of the two layers functioning as a hole transport layer or an electron transport layer, and the other functioning as an intervening layer that suppresses recombination of electrons and holes. This makes it possible to further improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the presence of openings in the first hole transport layer and the second hole transport layer, and the first electron transport layer and the second electron transport layer.

[0027] In the present disclosure, the second hole transport layer may be provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer may be provided between the first electron transport layer and the photoelectric conversion layer.

[0028] In the present disclosure, the second hole transport layer may be provided between the first electrode and the first hole transport layer, and the second electron transport layer may be provided between the second electrode and the first electron transport layer.

[0029] The present disclosure may further include a substrate that constitutes a light-receiving surface, and the substrate may hold the first electrode.

[0030] According to the above-described configuration, a so-called inverted structure perovskite solar cell can be obtained.

[0031] The present disclosure may further include a substrate that constitutes the light-receiving surface, and the substrate may hold the second electrode.

[0032] According to the above-described configuration, a so-called planar perovskite solar cell can be obtained.

[0033] In the present disclosure, the photoelectric conversion layer may have a porous layer adjacent to the electron transport layer.

[0034] According to the above-described configuration, a so-called mesoporous perovskite solar cell can be obtained.

[0035] FIG. 1 is a schematic cross-sectional view of a solar cell module. FIG. 2 is a schematic cross-sectional view of a solar cell according to embodiment 1 of the present disclosure. FIG. 3 is an explanatory diagram of the band gap of the solar cell according to embodiment 1 of the present disclosure. FIG. 4 is a schematic cross-sectional view of a modified solar cell according to embodiment 1 of the present disclosure. FIG. 5 is a schematic cross-sectional view of a solar cell according to embodiment 2 of the present disclosure. FIG. 6 is a schematic cross-sectional view of a modified solar cell according to embodiment 2 of the present disclosure. FIG. 7 is a schematic cross-sectional view of a solar cell according to embodiment 3 of the present disclosure. FIG. 8 is a schematic cross-sectional view of a modified solar cell according to embodiment 3 of the present disclosure. FIG. 9 is a schematic cross-sectional view of a solar cell according to embodiment 4 of the present disclosure. FIG. 10 is a schematic cross-sectional view of a modified solar cell according to embodiment 4 of the present disclosure.

[0036] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. The embodiments described below do not unnecessarily limit the content of the present disclosure as defined in the claims, and not all of the configurations described in the following embodiments are necessarily essential to the solutions of the present disclosure. Furthermore, for illustrative purposes, the light-receiving side of the solar cell will be referred to as the lower side and the side opposite the light-receiving side as the upper side. However, this is for convenience and does not affect the installation orientation or recommended installation orientation. The present disclosure can be applied even if the top and bottom are reversed as long as there is no contradiction. In other words, the present disclosure is valid even if the light-receiving side and the side opposite the light-receiving side are reversed as long as there is no contradiction. In the following description, as a general rule, unless otherwise specified, identical components are assigned the same reference numerals, and their names and functions are also the same. Therefore, in such cases, detailed descriptions thereof will not be repeated.

[0037] First Embodiment 1. Solar Cell Fig. 1 is a schematic cross-sectional view of a solar cell module 1 including a solar cell 100 according to this embodiment.

[0038] The solar cell module 1 is configured by arranging a plurality of solar cells 100 in series on a transparent substrate 2 .

[0039] 1 and 2 , each solar cell 100 has a first electrode 10, a hole transport layer 20, a photoelectric conversion layer 30 containing a perovskite compound, an electron transport layer 40, and a second electrode 50 stacked in this order on a transparent substrate 2. The first electrode 10 is in contact with the hole transport layer 20, the hole transport layer 20 is in contact with the photoelectric conversion layer 30, the photoelectric conversion layer 30 is in contact with the electron transport layer 40, and the electron transport layer 40 is in contact with the second electrode 50.

[0040] The first electrode 10 of a solar cell 100 and the second electrode 50 of the solar cell 100 adjacent to that solar cell 100 are connected in series.

[0041] Each configuration will be described in detail below. In the first embodiment, the first electrode 10 is in contact with the hole transport layer 20, the hole transport layer 20 is in contact with the photoelectric conversion layer 30, the photoelectric conversion layer 30 is in contact with the electron transport layer 40, and the electron transport layer 40 is in contact with the second electrode 50. However, this does not exclude the case where they are not in contact with each other and another layer is interposed between them. In any case, adjacent layers from the first electrode 10 to the second electrode 50 are electrically connected to each other.

[0042] [Transparent Substrate] The transparent substrate 2 is made of a transparent material and supports the solar cell 100. Examples of materials for the transparent substrate 2 include transparent glass (more specifically, soda-lime glass, alkali-free glass, etc.) and transparent resins such as heat-resistant organic films.

[0043] The transparent substrate 2 can be made of a plastic such as PET or polyimide, or glass, for example. By using a flexible substrate, the solar cell 100 itself can be made flexible. When the transparent substrate 2 is made of a transparent resin such as an organic film, a barrier layer (not shown) may be provided between the solar cell 100 and the transparent substrate 2. The barrier layer may be made of a material with high gas barrier properties, a dense inorganic material layer, or an insulating material. In this way, it is possible to prevent moisture and the like from penetrating the photoelectric conversion layer 30.

[0044] The transparent substrate 2 is disposed on the light-receiving surface side of the solar cell 100. Note that "transparent" means that it transmits light, but does not exclude substances that reflect or absorb light even slightly. It is sufficient that it is disposed on the light-receiving surface side of the solar cell and transmits light appropriately, and it can be considered synonymous with being disposed on the light-receiving surface side of the solar cell. Therefore, being disposed at least on the light-receiving surface side can be considered transparent. In other words, the transparent substrate 2 refers to a substrate disposed on the light-receiving surface side of the solar cell 100.

[0045] The transparent substrate 2 has a thickness of approximately 300 μm to 1500 μm, which reduces the risk of moisture or the like penetrating the photoelectric conversion layer 30 and reducing the conversion efficiency and durability of the solar cell 100.

[0046] [First Electrode] The first electrode 10 corresponds to the anode of the solar cell 100. The thickness of the first electrode 10 may be, for example, 30 nm or more and 1000 nm or less. Examples of materials constituting the first electrode 10 include transparent conductive materials (particularly, transparent conductive oxides (TCOs)) and non-transparent conductive materials. Examples of transparent conductive materials include copper iodide (CuI), indium tin oxide (ITO), tin(IV) oxide (SnO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). Non-transparent conductive materials can be opaque but transparent depending on the thickness of the material, and therefore can be used as an electrode on the light-receiving surface of a photoelectric conversion element.

[0047] [Hole Transport Layer] The hole transport layer 20 is a layer containing a material that easily moves holes generated in the photoelectric conversion layer 30 to the first electrode 10. As long as the solar cell 100 has a photoelectric conversion function, it is self-evident that the hole transport layer 20 has a hole transport function as long as the hole transport layer 20 is located on the hole transport side of the photoelectric conversion layer 30, and no confirmation is required. In other words, the hole transport layer 20 refers to one that is located on the hole transport side of the photoelectric conversion layer 30. The thickness of the hole transport layer 20 may be, for example, 40 nm or more and 600 nm or less.

[0048] 2 , the hole transport layer 20 is composed of a first hole transport layer 21 having a function of transporting holes generated in the photoelectric conversion layer 30, and a second hole transport layer 22 having a function of blocking electrons generated in the photoelectric conversion layer 30. In the first embodiment, the second hole transport layer 22 is provided between the first hole transport layer 21 and the photoelectric conversion layer 30, and an opening 23 is provided in the second hole transport layer 22.

[0049] The first hole transport layer 21 and the second hole transport layer 22 can be formed by, for example, sputtering, die coating, screen printing, or the like. The openings 23 provided in the second hole transport layer 22 are formed by sputtering or vapor deposition using patterning or a mask when forming the second hole transport layer 22 after forming the first hole transport layer 21. The patterning can be performed using, for example, a laser scribing device or a mechanical scribing device. The photoelectric conversion layer 30 is formed after forming the second hole transport layer 22 with the openings 23 provided therein. At this time, it is preferable that the first hole transport layer 21 and the photoelectric conversion layer 30 are in direct contact with each other in the area of ​​the openings 23.

[0050] By covering the front and back of the photoelectric conversion layer 30 with the first electrode 10 and the second electrode 50, holes and electrons can move in the first electrode 10 and the second electrode 50 in a direction along the layers of the hole transport layer 20, the photoelectric conversion layer 30, and the electron transport layer 40, thereby avoiding a decrease in efficiency.

[0051] Examples of the hole transport material constituting the hole transport layer 20 (first hole transport layer 21, second hole transport layer 22) include an organic hole transport material, an inorganic hole transport material, and an organic-inorganic hybrid hole transport material.

[0052] In this specification, "organic (organic substance)" typically refers to a substance composed of multiple carbon elements. Carbon materials such as graphite, graphene, carbon nanowires, carbon nanofibers, carbon nanotubes, and carbon or carbon black that function as electrodes are not considered to be organic (organic substance). In other words, "organic" refers to a substance that has multiple carbon elements as one of its constituent elements, excluding carbon materials such as graphite.

[0053] Furthermore, "inorganic" refers to something that is not organic. That is, the hole transport layer 20 refers to a layer that includes a plurality of carbon atoms as one of its constituent elements, or a layer that does not include a plurality of carbon atoms as its constituent elements (for example, metal atoms, halogen atoms, chalcogen atoms, or metal chalcogenides). The same applies to the electron transport layer 40.

[0054] Examples of organic hole transport materials that can be suitably used for the first hole transport layer 21 include Spiro-TTB (2,2',7,7'-tetra(N,N-di-tolyl)amino-spiro-bifluorene), Spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenilamine)-9,9'-spirobifluorene), PTAA (Polytriarylamine), P3CT-N (Polytriarylamine), and CI 111111. Examples of such polymers include poly(3-(4-carboxylatebutyl)thiophene)-CHNH2 (poly-TPD), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine), poly(3-hexylthiophene) (P3HT), and poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT:PSS).

[0055] Examples of organic hole transport materials that can be suitably used for the second hole transport layer 22 include 2PACz ([2-(9H-Carbazol-9-yl)ethyl]phosphonic Acid), 4PACz ([4-(9H-Carbazol-9-yl)butyl]phosphonic Acid), MeO-2PACz ([2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic Acid), MeO-4PACz ((4-(3,6-Dimethoxy-9H-carbazol-9-yl)butyl)phosphonic acid), Me-2PACz ((2-(3,6-Dimethyl-9H-carbazol-9-yl)ethyl)phosphonic acid), and Me-4PACz ([4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid).

[0056] Examples of inorganic hole transport materials that can be suitably used for the first hole transport layer 21 include nickel (II) oxide (NiO), molybdenum dioxide (MoO), tin (II) oxide (SnO), molybdenum disulfide (MoS), copper oxide (CuO), Li ion and Mg ion doped nickel oxide (NiMgLiO), Mg ion doped nickel oxide (NiMgO), Li ion doped nickel oxide (NiLiO), and the like.

[0057] The above hole transport materials are merely examples, and any of the materials listed as being suitable for use in the first hole transport layer 21 can also be used in the second hole transport layer 22, and any of the materials listed as being suitable for use in the second hole transport layer 22 can also be used in the first hole transport layer 21. Materials not listed as examples above can also be used as long as they can exhibit similar functions.

[0058] [Photoelectric Conversion Layer] The photoelectric conversion layer 30 is a layer capable of absorbing light and generating holes and electrons. It preferably contains a perovskite compound. The photoelectric conversion layer 30 can be formed by a known film formation method such as spin coating, die coating, or inkjet printing. The thickness of the photoelectric conversion layer 30 may be, for example, 100 nm or more and 1000 nm or less.

[0059] The perovskite compound contained in the photoelectric conversion layer 30 is preferably composed of a compound (perovskite compound) represented by the general formula: ABX3 (1). However, although the composition ratio of each element is preferably 1:1:3, it is not necessarily 1:1:3, the content ratio of each element may be appropriately increased or decreased, and each constituent element does not necessarily have to be of one type, and as long as the photoelectric conversion layer has a photoelectric conversion function, there is a degree of freedom in the configuration as described above.

[0060] In general formula (1), A is an organic molecule (including an organic group or an organic cation), or an inorganic atom or molecule (including an inorganic group or an inorganic cation), or a combination thereof, B is a metal atom or molecule (including a metal cation), and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion). In general formula (1), the three Xs may be the same or different.

[0061] When contained in the photoelectric conversion layer 30, the perovskite compound is capable of absorbing light and converting it into electricity, and this fact should also be taken into consideration. That is, a perovskite compound can be determined by, for example, containing organic molecules, metal atoms, and halogen atoms.

[0062] Furthermore, a perovskite compound can be determined by detecting elements corresponding to A, B, and X, as long as the photoelectric conversion layer 30 has a photoelectric conversion function. 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 element or a chalcogen element. Alternatively, a perovskite compound can be determined by containing A, B, and X, for example, by detecting an inorganic atom, a metal atom, and a halogen atom.

[0063] Furthermore, as long as the photoelectric conversion layer has a photoelectric conversion function, the presence of a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X. For example, cesium or rubidium is suitable as the inorganic atom, and therefore, it is sufficient if cesium or rubidium, a metal element, and a halogen or chalcogen are detected.

[0064] Furthermore, the presence of a perovskite compound is not necessarily required, since it is a natural consequence that the photoelectric conversion layer must have a crystalline structure in order to have a photoelectric conversion function. The photoelectric conversion layer 30 may include compounds other than perovskite compounds.

[0065] The photoelectric conversion layer 30 may contain an organic-inorganic hybrid compound. The organic-inorganic hybrid compound refers to a compound containing an inorganic material and an organic material.

[0066] Solar cells using perovskite compounds, which are organic-inorganic hybrid compounds, are also called organic-inorganic hybrid solar cells. The term "organic-inorganic hybrid compound" refers to a compound that contains multiple carbon atoms as one of its constituent elements, and also contains compounds that do not contain multiple carbon atoms as constituent elements, such as metal atoms, halogen atoms, or chalcogen atoms.

[0067] [Electron Transport Layer] The electron transport layer 40 is a layer containing a material that easily transfers electrons generated in the photoelectric conversion layer 30 to the second electrode 50. As long as the solar cell 100 has a photoelectric conversion function, it is self-evident that the electron transport layer 40 has the function of transporting electrons as long as the electron transport layer 40 is located on the electron transport side of the photoelectric conversion layer 30, and no confirmation is required. In other words, the electron transport layer 40 refers to a layer that is located on the electron transport side of the photoelectric conversion layer 30. The thickness of the electron transport layer 40 may be, for example, 10 nm to 200 nm.

[0068] 2 , the electron transport layer 40 is composed of a first electron transport layer 41 having a function of transporting electrons generated in the photoelectric conversion layer 30, and a second electron transport layer 42 having a function of blocking electrons generated in the photoelectric conversion layer 30. In the first embodiment, the second electron transport layer 42 is provided between the first electron transport layer 41 and the photoelectric conversion layer 30, and an opening 23 is provided in the second electron transport layer 42.

[0069] The first electron transport layer 41 and the second electron transport layer 42 can be formed by, for example, sputtering, die coating, or screen printing. The openings 43 provided in the second electron transport layer 42 are formed by patterning when the second electron transport layer 42 is formed after the photoelectric conversion layer 30 is formed. For example, a laser scribing device or a mechanical scribing device can be used for the patterning. The first electron transport layer 41 is formed after the second electron transport layer 42 having the openings 43 is formed. At this time, it is preferable that the photoelectric conversion layer 30 and the first electron transport layer 41 are in direct contact with each other at the openings 43.

[0070] By covering the front and back of the photoelectric conversion layer 30 with the first electrode 10 and the second electrode 50, holes and electrons can move in the first electrode 10 and the second electrode 50 in a direction along the layers of the hole transport layer 20, the photoelectric conversion layer 30, and the electron transport layer 40, thereby avoiding a decrease in efficiency.

[0071] Examples of the electron transport material constituting the electron transport layer 40 (first electron transport layer 41, second electron transport layer 42) include organic electron transport materials and inorganic electron transport materials.

[0072] Examples of organic electron transport materials that can be suitably used for the first electron transport layer 41 include PCBM ([6,6]-Phenyl-C 61 -Butyric Acid Methyl Ester), C ６０ (Fullerene), etc.

[0073] Examples of organic electron transport materials that can be suitably used for the second electron transport layer 42 include BCP (1-Bromo-3-chloropropane) and NBphen ([2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline]).

[0074] Examples of inorganic electron transport materials that can be suitably used for the first electron transport layer 41 include tin(IV) oxide (SnO), zinc tin composite oxide (ZTO), indium tin oxide (IZO), titanium(IV) oxide (TiO), and zinc oxide (ZnO).

[0075] Examples of inorganic electron transport materials that can be suitably used for the second electron transport layer 42 include lithium fluoride (LiF), sodium fluoride (NaF), magnesium fluoride (MgF), and calcium fluoride (CaF).

[0076] The above electron transport materials are merely examples, and any of the materials listed as being suitable for use in the first electron transport layer 41 can also be used in the second electron transport layer 42, and any of the materials listed as being suitable for use in the second electron transport layer 42 can also be used in the first electron transport layer 41. Materials not listed as examples above can also be used as long as they can exhibit similar functions.

[0077] FIG. 3 is a graph showing the energy levels in the first hole transport layer 21, the second hole transport layer 22, the photoelectric conversion layer 30, the second electron transport layer 42, and the first electron transport layer 41, with the electron energy being higher at the top.

[0078] The materials constituting the first hole transport layer 21 and the second hole transport layer 22 and the materials constituting the first electron transport layer 41 and the second electron transport layer 42 are exemplified above. In this case, the first hole transport layer 21 and the second hole transport layer 22 are preferably designed so that the VBM of the first hole transport layer 21 is shallower than the VBM of the second hole transport layer 22. Furthermore, the first electron transport layer 41 and the second electron transport layer 42 are preferably designed so that the CBM of the first electron transport layer 41 is deeper than the CBM of the second electron transport layer 42.

[0079] Here, VBM refers to the upper end of the valence band (Valence Band Maximum), and CBM refers to the lower end of the conduction band (Conduction Band Minimum). VBM and CBM represent energy levels for electrons below the vacuum level. The absolute value of the difference between the vacuum level and VBM can be rephrased as the (absolute value of) ionization potential, and the absolute value of the difference between the vacuum level and CBM can be rephrased as the (absolute value of) electron affinity. Furthermore, a "shallow" VBM or CBM means that the corresponding electron affinity or ionization energy is small or close to the vacuum level, and a "deep" VBM or CBM means that the corresponding electron affinity or ionization energy is large or far from the vacuum level. With the above-described configuration, charges generated in the photoelectric conversion layer 30 can be efficiently flowed toward the second electrode 50.

[0080] When light is absorbed by the photoelectric conversion layer 30 and the perovskite compound is photoexcited, electrons are generated in the conduction band of the perovskite compound, and holes are generated in the valence band of the perovskite compound. The generated electrons cannot move to the second hole transport layer 22 because the CBM of the second hole transport layer 22 is shallower than the CBM of the photoelectric conversion layer 30, and are instead guided to the second electron transport layer 42. In other words, the generated electrons move from top to bottom in FIG. 3. On the other hand, the generated holes cannot move to the second electron transport layer 42, which has a deep VBM, and are instead repelled and guided to the first hole transport layer 21 via the second hole transport layer 22. In other words, the generated holes move from bottom to top in FIG. 3. In this way, charges are separated and electricity is generated.

[0081] In the solar cell 100, recombination of holes and electrons is one of the causes of a decrease in the open circuit voltage of the element, but by configuring as described above, recombination is suppressed, the open circuit voltage is improved, and the element performance can be improved.

[0082] 3, the VBM of the first hole transport layer 21 may be shallower than the VBM of the second hole transport layer 22. Similarly, the CBM of the first electron transport layer 41 may be deeper than the CBM of the second electron transport layer 42. The VBM of the second hole transport layer 22 may be shallower than the VBM of the photoelectric conversion layer 30. Similarly, the CBM of the second electron transport layer 42 may be deeper than the CBM of the photoelectric conversion layer 30. In this way, the separated electrons and holes can be efficiently transported to the electrode, thereby improving power generation efficiency.

[0083] 3 , the VBM of the second hole transport layer 22 may be configured to be shallower than the VBM of the photoelectric conversion layer 30. Similarly, the CBM of the second electron transport layer 42 may be configured to be shallower than the CBM of the photoelectric conversion layer 30. This is because, even with such a configuration, holes and electrons can move to the first hole transport layer 21 and the first electron transport layer 41 through the openings 23 and 43. Furthermore, if the materials, thicknesses, polarities, and the like of the second hole transport layer 22 and the second electron transport layer 42 are appropriately designed (to enable conduction such as tunneling conduction), holes and electrons can move to the first hole transport layer 21 and the first electron transport layer 41 by the quantum tunneling effect or the like.

[0084] Holes generated in the photoelectric conversion layer 30 are directly guided from the photoelectric conversion layer 30 to the first hole transport layer 21 at the opening 23. Electrons generated in the photoelectric conversion layer 30 are directly guided from the photoelectric conversion layer 30 to the first electron transport layer 41 at the opening 43.

[0085] As described above, by making the hole transport layer 20 a two-layer structure consisting of the first hole transport layer 21 and the second hole transport layer 22 and having the second hole transport layer 22 function as an intervening layer that suppresses recombination of electrons and holes, the recombination of holes and electrons generated in the photoelectric conversion layer 30 is suppressed in the second hole transport layer 22, thereby improving the open circuit voltage (Voc).

[0086] Openings 23 are partially provided in the second hole transport layer 22. The first hole transport layer 21 and the photoelectric conversion layer 30 are in direct contact with each other through the openings 23 provided in the second hole transport layer 22, so it is possible to lower the resistance compared to when the second hole transport layer 22 is interposed between them. Therefore, the resistance is lower than when there are no openings 23, and it is possible to ensure a current.

[0087] Similarly, by making the electron transport layer 40 a two-layer structure of a first electron transport layer 41 and a second electron transport layer 42, and having the second electron transport layer 42 function as an intervening layer that suppresses recombination of electrons and holes, the recombination of holes and electrons generated in the photoelectric conversion layer 30 is suppressed in the second electron transport layer 42, thereby improving the open-circuit voltage (Voc).

[0088] Openings 43 are partially provided in the second electron transport layer 42. Because the photoelectric conversion layer 30 and the first electron transport layer 41 are in direct contact with each other through the openings 43 provided in the second electron transport layer 42, it is possible to lower the resistance compared to when the second electron transport layer 42 is interposed therebetween. Therefore, the resistance is lower than when there are no openings 43, and it is possible to ensure a current.

[0089] [Second Electrode] The second electrode 50 corresponds to the cathode of the solar cell 100. The thickness of the second electrode 50 may be, for example, 50 nm or more and 300 nm or less. Examples of materials constituting the second electrode 50 include metals, transparent conductive inorganic materials, conductive fine particles, and conductive polymers (particularly, transparent conductive polymers).

[0090] Examples of metals include nickel (Ni), gold (Au), silver (Ag), platinum (Pt), and palladium (Pd). Examples of transparent conductive inorganic materials include copper iodide (CuI), indium tin oxide (ITO), tin(IV) oxide (SnO2), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). Examples of conductive particles include silver nanowires and carbon nanofibers. Examples of transparent conductive polymers include PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). Furthermore, carbon materials such as graphite can also be used for the second electrode 50.

[0091] It is not necessary to use an opaque material for the second electrode 50. When the second electrode 50 is a transparent electrode, the same material as that of the first electrode 10 described above may be used.

[0092] The solar cell 100 may be provided with a second barrier layer (not shown) so as to cover an upper portion of the second electrode 50 and sides of the electron transport layer 40 and the second electrode 50. The second barrier layer may be made of a material with high gas barrier properties, a dense inorganic material layer, or an insulating material.

[0093] <Modification of First Embodiment> A modification of the solar cell 100 according to the first embodiment will be described. As shown in Fig. 4 , in the solar cell 101 according to this modification, the order of the first hole transport layer 21 and the second hole transport layer 22 is reversed, and the order of the first electron transport layer 41 and the second electron transport layer 42 is reversed.

[0094] Even with this configuration, similarly to the solar cell 100 shown in FIG. 2 , by making both the second hole transport layer 22 and the second electron transport layer 42 function as intervening layers that suppress the recombination of electrons and holes, it is possible to further improve the open circuit voltage (Voc), while suppressing an increase in resistance due to the openings 23 provided in the second hole transport layer 22 and the openings 43 provided in the second electron transport layer 42.

[0095] 2 and the solar cell 101 shown in Fig. 4 have been described as having the opening 23 provided in the second hole transport layer 22 and the opening 43 provided in the second electron transport layer 42, but the present invention is not limited to this. Alternatively, the second hole transport layer 22 may have the opening 23 but the second electron transport layer 42 may not have the opening 43, or the second hole transport layer 22 may have the opening 23 but the second electron transport layer 42 may have the opening 43.

[0096] Second Embodiment As shown in FIG. 5, in a solar cell 200 according to a second embodiment, the hole transport layer 20 is made up of two layers, but the electron transport layer 40 is made up of one layer.

[0097] The hole transport layer 20 in the solar cell 200 is composed of a first hole transport layer 21 having the function of transporting holes generated in the photoelectric conversion layer 30, and a second hole transport layer 22 having the function of blocking electrons generated in the photoelectric conversion layer 30, similar to the solar cell 100 according to the first embodiment shown in Figure 2, and the second hole transport layer 22 is provided between the first hole transport layer 21 and the photoelectric conversion layer 30, and an opening 23 is provided in the second hole transport layer 22.

[0098] At least in the hole transport layer 20, by making the second hole transport layer 22 function as an intervening layer that suppresses the recombination of electrons and holes, it is possible to further improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the opening 23 provided in the second hole transport layer 22.

[0099] <Modification of Second Embodiment> A modification of the solar cell 200 according to the second embodiment will be described. As shown in Fig. 6 , in the solar cell 201 according to this modification, the order of the first hole transport layer 21 and the second hole transport layer 22 is reversed.

[0100] Even with this configuration, as with the solar cell 200 shown in FIG. 5 , by making the second hole transport layer 22 function as an intervening layer that suppresses the recombination of electrons and holes, it is possible to further improve the open circuit voltage (Voc), while suppressing an increase in resistance due to the openings 23 provided in the second hole transport layer 22.

[0101] Third Embodiment As shown in FIG. 7, in a solar cell 300 according to a third embodiment, the hole transport layer 20 is made up of one layer, but the electron transport layer 40 is made up of two layers.

[0102] The electron transport layer 40 in the solar cell 300 is composed of a first electron transport layer 41 having a function of transporting electrons generated in the photoelectric conversion layer 30 and a second electron transport layer 42 having a function of blocking holes generated in the photoelectric conversion layer 30, similar to the solar cell 100 according to the first embodiment shown in FIG. 2 , and the second electron transport layer 42 is provided between the first electron transport layer 41 and the photoelectric conversion layer 30, and an opening 43 is provided in the second electron transport layer 42.

[0103] At least in the electron transport layer 40, the second electron transport layer 42 functions as an intervening layer that suppresses recombination of electrons and holes, thereby further improving the open circuit voltage (Voc) while suppressing an increase in resistance due to the openings 43 provided in the second electron transport layer 42.

[0104] <Modification of Third Embodiment> A modification of the solar cell 300 according to the third embodiment will be described. As shown in Fig. 8 , in the solar cell 301 according to this modification, the order of the first hole transport layer 21 and the second hole transport layer 22 is reversed.

[0105] Even with this configuration, as with the solar cell 300 shown in FIG. 7 , by making the second hole transport layer 22 function as an intervening layer that suppresses the recombination of electrons and holes, it is possible to further improve the open circuit voltage (Voc), while suppressing an increase in resistance due to the openings 23 provided in the second hole transport layer 22.

[0106] Fourth Embodiment As shown in FIG. 9, in a solar cell 400 according to a fourth embodiment, the hole transport layer 20 and the electron transport layer 40 each include two layers.

[0107] 2 according to the first embodiment, the electron transport layer 40 in the solar cell 300 is composed of a first electron transport layer 41 having a function of transporting electrons generated in the photoelectric conversion layer 30, and a second electron transport layer 42 having a function of blocking holes generated in the photoelectric conversion layer 30. In the fourth embodiment, the second hole transport layer 22 is provided between the first hole transport layer 21 and the photoelectric conversion layer 30.

[0108] An opening 44 is provided in the first hole transport layer 21, and an opening 43 is provided in the second hole transport layer 22. In this case, the opening 43 provided in the second hole transport layer 22 is provided at a position that does not overlap with the opening 44 provided in the first hole transport layer 21.

[0109] The openings 24 provided in the first hole transport layer 21 are formed by patterning or the like when the first hole transport layer 21 is formed. The openings 23 provided in the second hole transport layer 22 are formed by patterning or the like at positions that do not overlap with the openings 43 provided in the first hole transport layer 21 when the second hole transport layer 22 is formed. For example, a laser scribing device or a mechanical scribing device can be used for this patterning. After the first hole transport layer 21 and the second hole transport layer 22 are formed, the photoelectric conversion layer 30 is formed.

[0110] In the opening 24, the first electrode 10 and the second hole transport layer 22 are preferably in direct contact with each other. In the opening 23, the first hole transport layer 21 and the photoelectric conversion layer 30 are preferably in direct contact with each other.

[0111] As described above, by making the hole transport layer 20 a two-layer structure consisting of the first hole transport layer 21 and the second hole transport layer 22 and having the second hole transport layer 22 function as an intervening layer that suppresses recombination of electrons and holes, the recombination of holes and electrons generated in the photoelectric conversion layer 30 is suppressed in the second hole transport layer 22, thereby improving the open circuit voltage (Voc).

[0112] An opening 24 is provided in the first hole transport layer 21, and the first electrode 10 and the photoelectric conversion layer 30 are in direct contact at the opening 24, and an opening 23 is provided in the second hole transport layer 22, and the first hole transport layer 21 and the photoelectric conversion layer 30 are in direct contact at the opening 23, so that the resistance is low because it does not go through the first hole transport layer 21 or the second hole transport layer 22. Therefore, the resistance is lower than when there is no opening 24 in the first hole transport layer 21 or no opening 23 in the second hole transport layer 22, and it is possible to ensure current.

[0113] Similarly, by making the electron transport layer 40 a two-layer structure of a first electron transport layer 41 and a second electron transport layer 42, and having the second electron transport layer 42 function as an intervening layer that suppresses recombination of electrons and holes, the recombination of holes and electrons generated in the photoelectric conversion layer 30 is suppressed in the second electron transport layer 42, thereby improving the open-circuit voltage (Voc).

[0114] The first electron transport layer 41 has an opening 44, where the second electrode 50 and the photoelectric conversion layer 30 are in direct contact with each other, and the second electron transport layer 42 has an opening 43, where the first electron transport layer 41 and the photoelectric conversion layer 30 are in direct contact with each other, so that the resistance is low without going through the first electron transport layer 41 or the second electron transport layer 42. Therefore, the resistance is lower than when there is no opening 44 in the first electron transport layer 41 or no opening 43 in the second electron transport layer 42, and it is possible to ensure a current.

[0115] <Modification of Fourth Embodiment> A modification of the solar cell 400 according to the fourth embodiment will be described. As shown in Fig. 10 , in a solar cell 401 according to this modification, the order of the first hole transport layer 21 and the second hole transport layer 22 is reversed, and the order of the first electron transport layer 41 and the second electron transport layer 42 is reversed.

[0116] Even with this configuration, the same effects as those of the solar cell 400 shown in FIG. 9 can be achieved.

[0117] From the description of the present disclosure, a solar cell having, in this order, a first electrode, a hole transport layer, a photoelectric conversion layer containing a perovskite compound, an electron transport layer, and a second electrode, wherein at least either the hole transport layer or the electron transport layer is composed of two layers, and at least one of the two layers has an opening partially provided therein, can at least improve the open circuit voltage (Voc) while suppressing an increase in resistance due to the opening, thereby obtaining a solar cell with improved power generation efficiency.

[0118] <Other embodiments> The solar cell 100 according to the first embodiment, the solar cell 200 according to the second embodiment, the solar cell 300 according to the third embodiment, the solar cell 400 according to the fourth embodiment, and their modified examples all have a configuration in which the first electrode 10, the hole transport layer 20, the photoelectric conversion layer 30 containing a perovskite compound, the electron transport layer 40, and the second electrode 50 are stacked in this order on the transparent substrate 2, but the present invention is not limited to this.

[0119] That is, in the solar cell 100 according to the first embodiment, the solar cell 200 according to the second embodiment, the solar cell 300 according to the third embodiment, the solar cell 400 according to the fourth embodiment, and their modified examples, a second electrode 50, an electron transport layer 40, a photoelectric conversion layer 30 containing a perovskite compound, a hole transport layer 20, and a first electrode 10 may be laminated in this order on a transparent substrate 2. In this case, the first electrode 10 is in contact with the electron transport layer 40, the electron transport layer 40 is in contact with the photoelectric conversion layer 30, the photoelectric conversion layer 30 is in contact with the hole transport layer 20, and the hole transport layer 20 is in contact with the second electrode 50.

[0120] Furthermore, the photoelectric conversion layer 30 may have a porous layer adjacent to the electron transport layer 40, that is, a so-called mesoporous structure.

[0121] <Additional Notes> [Aspect 1] A solar cell having, in this order, a first electrode, a hole transport layer, a photoelectric conversion layer containing a perovskite compound, an electron transport layer, and a second electrode, wherein at least one of the hole transport layer or the electron transport layer is composed of two layers, and at least one of the two layers is partially provided with an opening. [Aspect 2] The solar cell according to Aspect 1, wherein the hole transport layer is composed of a first hole transport layer and a second hole transport layer, the electron transport layer is composed of a first electron transport layer and a second electron transport layer, and the openings are provided in the second hole transport layer and the second electron transport layer. [Aspect 3] The solar cell according to Aspect 2, wherein the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer. [Aspect 4] The solar cell according to Aspect 2, wherein the second hole transport layer is provided between the first electrode and the first hole transport layer, and the second electron transport layer is provided between the second electrode and the first electron transport layer. [Aspect 5] The solar cell according to Aspect 1, wherein the hole transport layer is composed of a first hole transport layer and a second hole transport layer, and the opening is provided in the second hole transport layer. [Aspect 6] The solar cell according to Aspect 5, wherein the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer. [Aspect 7] The solar cell according to Aspect 5, wherein the second hole transport layer is provided between the first electrode and the first hole transport layer. [Aspect 8] The solar cell according to Aspect 1, wherein the electron transport layer is composed of a first electron transport layer and a second electron transport layer, and the opening is provided in the second electron transport layer. [Aspect 9] The solar cell according to Aspect 8, wherein the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer. [Aspect 10] The solar cell according to Aspect 8, wherein the second electron transport layer is provided between the second electrode and the first electron transport layer.[Aspect 11] The solar cell of Aspect 1, wherein the hole transport layer is composed of a first hole transport layer and a second hole transport layer, the electron transport layer is composed of a first electron transport layer and a second electron transport layer, the openings are provided in the first hole transport layer and the second hole transport layer and in the first electron transport layer and the second electron transport layer, the openings in the second hole transport layer are provided at positions that do not overlap with the openings in the first hole transport layer, and the openings in the second electron transport layer are provided at positions that do not overlap with the openings in the first electron transport layer. [Aspect 12] The solar cell of Aspect 11, wherein the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer. [Aspect 13] The solar cell of Aspect 11, wherein the second hole transport layer is provided between the first electrode and the first hole transport layer, and the second electron transport layer is provided between the second electrode and the first electron transport layer. [Aspect 14] The solar cell of any one of Aspects 1 to 13, further comprising a substrate that forms a light-receiving surface, the substrate supporting the first electrode. [Aspect 15] The solar cell of any one of Aspects 1 to 13, further comprising a substrate that forms a light-receiving surface, the substrate supporting the second electrode. [Aspect 16] The solar cell of any one of Aspects 1 to 15, wherein the photoelectric conversion layer has a porous layer adjacent to the electron transport layer.

[0122] The configuration disclosed in any of the above-described embodiments can be applied in combination with the configuration disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present disclosure are not limited thereto and can be modified as appropriate within the scope of the present disclosure.

[0123] This application claims priority from Japanese Patent Application No. 2024-146960, filed on August 28, 2024, the entire contents of which are incorporated herein by reference.

[0124] The present disclosure can be applied to applications in which the hole transport layer and the electron transport layer are each composed of multiple layers, thereby improving the open circuit voltage (Voc) while also achieving low resistance.

[0125] 1 Solar cell module 2: Transparent substrate 10: First electrode 20: Hole transport layer 21: First hole transport layer 22: Second hole transport layer 23: Opening 24: Opening 30: Photoelectric conversion layer 40: Electron transport layer 41: First electron transport layer 42: Second electron transport layer 43: Opening 44: Opening 50: Second electrode 100: Solar cell 101: Solar cell 200: Solar cell 201: Solar cell 300: Solar cell 301: Solar cell 400: Solar cell 401: Solar cell

Claims

1. A solar cell having, in this order, a first electrode, a hole transport layer, a photoelectric conversion layer containing a perovskite compound, an electron transport layer, and a second electrode, wherein at least one of the hole transport layer and the electron transport layer is composed of two layers, and at least one of the two layers has an opening partially formed therein.

2. The solar cell according to claim 1, wherein the hole transport layer is composed of a first hole transport layer and a second hole transport layer, the electron transport layer is composed of a first electron transport layer and a second electron transport layer, and the openings are provided in the second hole transport layer and the second electron transport layer.

3. The solar cell described in claim 2, characterized in that the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer.

4. The solar cell described in claim 2, characterized in that the second hole transport layer is provided between the first electrode and the first hole transport layer, and the second electron transport layer is provided between the second electrode and the first electron transport layer.

5. The solar cell according to claim 1, wherein the hole transport layer is composed of a first hole transport layer and a second hole transport layer, and the opening is provided in the second hole transport layer.

6. The solar cell according to claim 5, wherein the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer.

7. The solar cell according to claim 5, wherein the second hole transport layer is provided between the first electrode and the first hole transport layer.

8. The solar cell according to claim 1, wherein the electron transport layer is composed of a first electron transport layer and a second electron transport layer, and the opening is provided in the second electron transport layer.

9. The solar cell according to claim 8, wherein the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer.

10. The solar cell according to claim 8, wherein the second electron transport layer is provided between the second electrode and the first electron transport layer.

11. The solar cell according to claim 1, characterized in that the hole transport layer is composed of a first hole transport layer and a second hole transport layer, the electron transport layer is composed of a first electron transport layer and a second electron transport layer, the openings are provided in the first hole transport layer and the second hole transport layer and the first electron transport layer and the second electron transport layer, the openings provided in the second hole transport layer are provided at positions that do not overlap with the openings provided in the first hole transport layer, and the openings provided in the second electron transport layer are provided at positions that do not overlap with the openings provided in the first electron transport layer.

12. The solar cell described in claim 11, characterized in that the second hole transport layer is provided between the first hole transport layer and the photoelectric conversion layer, and the second electron transport layer is provided between the first electron transport layer and the photoelectric conversion layer.

13. The solar cell described in claim 11, characterized in that the second hole transport layer is provided between the first electrode and the first hole transport layer, and the second electron transport layer is provided between the second electrode and the first electron transport layer.

14. A solar cell according to any one of claims 1 to 13, further comprising a substrate that constitutes the light-receiving surface, said substrate supporting said first electrode.

15. A solar cell according to any one of claims 1 to 13, further comprising a substrate that constitutes the light-receiving surface, the substrate supporting the second electrode.

16. The solar cell according to any one of claims 1 to 15, characterized in that the photoelectric conversion layer has a porous layer adjacent to the electron transport layer.

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