Solar cell module

Abstract

A solar cell module (100) according to the present disclosure comprises: a substrate (1); and a first unit cell (101A) and a second unit cell (101B) that are disposed on the substrate (1) and are electrically connected to each other. Each of the first unit cell (101A) and the second unit cell (101B) is provided with a first electrode (2), a photoelectric conversion layer (3), an electron transport layer (4), and a second electrode (5) in this order from the substrate (1) side. The photoelectric conversion layer (3) contains a perovskite compound. The second electrode (5) of the first unit cell (101A) is electrically connected to the first electrode (2) of the second unit cell (101B) by means of a connection member (6). The second electrode (5) is formed of a first conductive material. The connection member (6) is formed of a second conductive material that is different from the first conductive material, and is in contact with the photoelectric conversion layer (3) of the first unit cell (101A).

Description

solar cell module

[0001] The present disclosure relates to solar cell modules.

[0002] In recent years, research and development of perovskite solar cells has been progressing, using perovskite crystals represented by the composition formula ABX3 (A is a monovalent cation, B is a divalent cation, and X is a halogen anion) and structures similar to them (hereinafter referred to as "perovskite compounds") as photoelectric conversion materials.

[0003] Perovskite solar cells are classified into a forward stack structure and an inverted stack structure. In a forward stack structure, an electron transport layer is disposed on the light incident side of a photoelectric conversion layer containing a perovskite compound. In a forward stack structure, for example, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an upper electrode are disposed in this order on a transparent electrode. In an inverted stack structure, a hole transport layer is disposed on the light incident side of a photoelectric conversion layer containing a perovskite compound. In an inverted stack structure, for example, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and an upper electrode are disposed in this order on a transparent electrode.

[0004] Patent Document 1 proposes a perovskite solar cell with an inverted stack structure that can have high photoelectric conversion efficiency, and discloses an integrated solar cell module in which perovskite solar cells with an inverted stack structure are connected in series as unit cells.

[0005] Patent No. 7068934

[0006] The present disclosure provides a solar cell module with improved reliability without significantly reducing conversion efficiency.

[0007] The solar cell module of the present disclosure is a solar cell module comprising: a substrate; and a first unit cell and a second unit cell disposed on the substrate and electrically connected to each other, wherein each of the first unit cell and the second unit cell comprises, from the substrate side, a first electrode, a photoelectric conversion layer, an electron transport layer, and a second electrode, in this order; the photoelectric conversion layer contains a perovskite compound; the second electrode of the first unit cell is electrically connected to the first electrode of the second unit cell by a connecting member; the second electrode is made of a first conductive material; and the connecting member is made of a second conductive material different from the first conductive material and is in contact with the photoelectric conversion layer of the first unit cell.

[0008] The present disclosure provides a solar cell module with improved reliability without significantly reducing conversion efficiency.

[0009] FIG. 1 is a cross-sectional view schematically showing a solar cell module according to a first embodiment. FIG. 2 is a cross-sectional view schematically showing a first modified example of the solar cell module according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing a second modified example of the solar cell module according to the first embodiment. FIG. 4 is a cross-sectional view schematically showing a third modified example of the solar cell module according to the first embodiment. FIG. 5 is a cross-sectional view schematically showing a solar cell module according to a second embodiment. FIG. 6 is a cross-sectional view schematically showing a modified example of the solar cell module according to the second embodiment. FIG. 7A is a cross-sectional view schematically showing the configuration of an evaluation sample of Example 1. FIG. 7B is a cross-sectional view schematically showing the configuration of an evaluation sample of Comparative Example 1. FIG. 8 is a cross-sectional view schematically showing a solar cell module fabricated in Comparative Example 2. FIG. 9 is a graph showing IV curves of the evaluation samples of Example 1 and Comparative Example 1. FIG. 10 is a graph showing IV curves of the solar cell modules of Example 2 and Comparative Example 2.

[0010] <Knowledge that forms the basis of the present disclosure> As described in the "Background Art" section, perovskite solar cells have a forward stack structure and an inverted stack structure. In an inverted stack structure, for example, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and an upper electrode are arranged in this order on a transparent electrode that serves as a lower electrode. When perovskite solar cells with such an inverted stack structure are integrated into unit cells to form a module, electrical connection between the unit cells is usually achieved by extending the upper electrode along the sidewall of the unit cell (i.e., the sidewall of the perovskite solar cell) and bringing it into contact with the lower electrode of an adjacent unit cell.

[0011] Solar cell modules using inverted stack perovskite solar cells as unit cells have a problem of decreasing conversion efficiency over time. The inventors of the present invention have investigated this problem and discovered the following facts.

[0012] In inverted-layer perovskite solar cells, a metal material such as silver is typically used for the upper electrode. When a metal upper electrode is extended along the sidewall of the solar cell, the metal material constituting the upper electrode and the perovskite compound contained in the photoelectric conversion layer come into direct contact with the sidewall of the solar cell. In this case, the metal material reacts with elements (e.g., iodine) constituting the perovskite compound, resulting in degradation of the perovskite compound and an increase in the resistance of the upper electrode due to the resulting reactants. It has been discovered that this degradation of the perovskite compound and the resulting increase in electrode resistance are factors that cause the conversion efficiency of solar cell modules to decrease over time. On the other hand, selecting a material for the upper electrode solely based on its reactivity with the perovskite compound results in a significant decrease in the solar cell's performance (specifically, conversion efficiency). Thus, it has been difficult to improve the reliability of solar cell modules by reducing or suppressing the decrease in conversion efficiency over time without significantly reducing conversion efficiency.

[0013] Based on the above facts, the inventors of the present invention have conducted further research and have come up with the solar cell module of the present disclosure. Specifically, the inventors have realized the solar cell module of the present disclosure, which can improve reliability while suppressing a significant decrease in conversion efficiency, by differentiating the material of the upper electrode of the perovskite solar cell used as a unit cell from the material used for electrically connecting the unit cells.

[0014] Embodiments of the Present Disclosure Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0015] First Embodiment FIG. 1 is a cross-sectional view schematically showing a solar cell module according to a first embodiment.

[0016] As shown in FIG. 1 , the solar cell module 100 according to the first embodiment includes a substrate 1 and a first unit cell 101A and a second unit cell 101B disposed on the substrate 1 and electrically connected to each other. Each of the first unit cell 101A and the second unit cell 101B includes, in this order from the substrate 1 side, a first electrode 2, a photoelectric conversion layer 3, an electron transport layer 4, and a second electrode 5. The photoelectric conversion layer 3 contains a perovskite compound. The second electrode 5 of the first unit cell 101A is electrically connected to the first electrode 2 of the second unit cell 101B via a connecting member 6. The second electrode 5 is made of a first conductive material. The connecting member 6 is made of a second conductive material different from the first conductive material and is in contact with the photoelectric conversion layer 3 of the first unit cell 101A. In this specification, "the second conductive material is different from the first conductive material" means that the composition of the second conductive material is different from the composition of the first conductive material.

[0017] With the above-described configuration, the solar cell module 100 according to the first embodiment can, for example, select a first conductive material for the second electrode 5 so as to achieve good conversion efficiency, and select a material that is less likely to chemically react with the perovskite compound contained in the photoelectric conversion layer 3 as the second conductive material for the connection member 6. In this way, the solar cell module 100 according to the first embodiment can appropriately select the materials for the second electrode 5 and the connection member 6, thereby suppressing a significant decrease in conversion efficiency while reducing or suppressing a decrease in conversion efficiency over time, thereby improving reliability. It is desirable that the reactivity between the second conductive material and the perovskite compound contained in the photoelectric conversion layer 3 be lower than the reactivity between the first conductive material and the perovskite compound contained in the photoelectric conversion layer 3.

[0018] When light is irradiated onto the solar cell module 100, the photoelectric conversion layer 3 in each of the first unit cell 101A and the second unit cell 101B absorbs the light and generates excited electrons and holes. The excited electrons move to the second electrode 5. Meanwhile, the holes generated in the photoelectric conversion layer 3 move to the first electrode 2. This allows the first unit cell 101A and the second unit cell 101B to extract current, with the first electrode 2 serving as a positive electrode and the second electrode 5 serving as a negative electrode. As described above, the second electrode 5 of the first unit cell 101A and the first electrode 2 of the second unit cell 101B are electrically connected by the connection member 6. That is, in the solar cell module 100, the first unit cell 101A and the second unit cell 101B are connected in series.

[0019] For example, the first conductive material may be a metal material, and the second conductive material may be a conductive oxide material. When the first conductive material is a metal material, electrons excited in the photoelectric conversion layer 3 can efficiently move to the second electrode 5, thereby improving the conversion efficiency of the solar cell module 100. On the other hand, a conductive oxide material is less likely to chemically react with a perovskite compound. Therefore, when the second conductive material is a conductive oxide material, even if the connection member 6 is in contact with the sidewall of the photoelectric conversion layer 3, a decrease in conversion efficiency over time due to a reaction between the second conductive material constituting the connection member 6 and the perovskite compound can be effectively suppressed. Therefore, when the first conductive material is a metal material and the second conductive material is a conductive oxide material, good conversion efficiency and more reliable improved reliability can be achieved.

[0020] When the first conductive material is a metal material, the metal material may include, for example, at least one selected from the group consisting of silver, aluminum, and copper. The second electrode 5 formed from such a metal material allows electrons excited in the photoelectric conversion layer 3 to move more efficiently to the second electrode 5. Therefore, the conversion efficiency of the solar cell module 100 can be further improved.

[0021] When the second conductive material is a conductive oxide material, the conductive oxide material may include, for example, at least one selected from the group consisting of indium tin oxide and fluorine-doped tin oxide. By forming the connection member 6 from such a material, it is possible to realize a connection member 6 that has good conductivity and can more effectively suppress a decrease in conversion efficiency over time due to a reaction with the perovskite compound.

[0022] 1 shows a configuration in which two unit cells are arranged on the substrate 1, but in the solar cell module according to the first embodiment, the number of unit cells provided on the substrate 1 is not limited to two, and three or more unit cells may be provided. FIG. 2 is a cross-sectional view schematically showing a first modified example of the solar cell module according to the first embodiment. The solar cell module 110 of the first modified example shown in FIG. 2 includes three or more unit cells 101 on the substrate 1. In the solar cell module 110, one of two adjacent unit cells 101 electrically connected to each other corresponds to a first unit cell 101A, and the other corresponds to a second unit cell 101B.

[0023] The connecting member 6 only needs to electrically connect the second electrode 5 of the first unit cell 101A and the first electrode 2 of the second unit cell 101B. Therefore, the connecting member 6 does not need to be formed so as to cover the entire surface of the second electrode 5 as shown in Figures 1 and 2. Figure 3 is a cross-sectional view schematically showing a second modified example of the solar cell module according to the first embodiment. As in the solar cell module 120 of the second modified example shown in Figure 3, the connecting member 6 may be configured to contact only a portion of the second electrode 5.

[0024] Hereinafter, each component of the solar cell module according to the first embodiment will be specifically described. In the following, when describing a configuration common to the first unit cell 101A and the second unit cell 101B, the first unit cell 101A and the second unit cell 101B will be referred to as unit cell 101.

[0025] [Substrate 1] The substrate 1 serves to hold the unit cells 101. The substrate 1 has an insulating surface at least on the surface that contacts the unit cells 101. The substrate 1 can be made of a transparent material. For example, a glass substrate or a plastic substrate can be used as the substrate 1. The plastic substrate may be, for example, a plastic film. Materials that can be used for such plastic films include polyimide, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymer. When a plastic substrate is used, it is preferable to form a barrier layer that has weather resistance.

[0026] [First Electrode 2] The first electrode 2 has electrical conductivity.

[0027] The first electrode 2 has a light-transmitting property, and transmits light in the visible to near-infrared region, for example.

[0028] The first electrode 2 is made of, for example, a transparent and conductive material. Examples of such materials include metal oxides and metal nitrides. Examples of such materials include: (i) titanium oxide doped with at least one element selected from the group consisting of lithium, magnesium, niobium, and fluorine; (ii) gallium oxide doped with at least one element selected from the group consisting of tin and silicon; (iii) gallium nitride doped with at least one element selected from the group consisting of silicon and oxygen; (iv) tin oxide doped with at least one element selected from the group consisting of antimony and fluorine; (v) zinc oxide doped with at least one element selected from the group consisting of boron, aluminum, gallium, and indium; (vi) indium-tin composite oxide (i.e., indium tin oxide); or (vii) a composite thereof.

[0029] The first electrode 2 may be formed using a non-transparent material and provided with a light-transmitting pattern. Examples of the light-transmitting pattern include a linear, wavy, lattice, or punched metal pattern in which a large number of fine through-holes are regularly or irregularly arranged. When the first electrode 2 has such a pattern, light can transmit through portions where no electrode material is present. Examples of non-transparent electrode materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or an alloy containing any of these. A conductive carbon material may be used as the non-transparent electrode material.

[0030] The light transmittance of the first electrode 2 may be, for example, 50% or more, or 80% or more. The wavelength of light to be transmitted depends on the absorption wavelength of the photoelectric conversion layer 3.

[0031] The thickness of the first electrode 2 is, for example, in the range of 1 nm to 1000 nm.

[0032] For example, the first electrode 2 of the first unit cell 101A and the first electrode 2 of the second unit cell 101B are separated from each other by a dividing groove 102, which will be described later.

[0033] For example, in the first unit cell 101A, the first electrode 2 is not in contact with the photoelectric conversion layer 3 .

[0034] [Photoelectric Conversion Layer 3] The photoelectric conversion layer 3 contains a perovskite compound. For example, the photoelectric conversion layer 3 contains a perovskite compound represented by the composition formula ABX3. A is a monovalent cation. Examples of the monovalent cation are alkali metal cations or organic cations. Examples of the alkali metal cation are potassium cations (K + ), cesium cation (Cs + ), or rubidium cation (Rb + ) An example of an organic cation is the methylammonium cation (CH3NH3 + ), formamidinium cation (HC(NH2)2 + ), ethylammonium cation (CH3CH2NH3 + ), or guanidinium cation (CH6N3 +) B is a divalent cation. An example of a divalent cation is Sn cation (Sn 2+ ), Ge cation (Ge 2+ ), or Pb cation (Pb 2+ ) The divalent cation may include at least one selected from the group consisting of Sn cations, Ge cations, and Pb cations. X is a monovalent anion. An example of a monovalent anion is a halogen anion. Each of the A, B, and X sites may be occupied by multiple types of ions.

[0035] The thickness of the photoelectric conversion layer 3 is, for example, not less than 50 nm and not more than 10 μm.

[0036] The photoelectric conversion layer 3 can be formed by using a solution coating method, a printing method, a vapor deposition method, a sputtering method, etc. The photoelectric conversion layer 3 may also be formed by cutting out a perovskite compound.

[0037] The photoelectric conversion layer 3 may primarily contain a perovskite compound represented by the composition formula ABX3. Here, "the photoelectric conversion layer 3 primarily contains a perovskite compound represented by the composition formula ABX3" means that the photoelectric conversion layer 3 contains 60 mass% or more of the perovskite compound represented by the composition formula ABX3. The photoelectric conversion layer 3 may also contain 95 mass% or more of the perovskite compound represented by the composition formula ABX3. The photoelectric conversion layer 3 may be made of a perovskite compound represented by the composition formula ABX3. The photoelectric conversion layer 3 may contain a perovskite compound represented by the composition formula ABX3, and may contain defects or impurities.

[0038] The photoelectric conversion layer 3 may further contain another compound different from the perovskite compound represented by the composition formula ABX. Examples of the other compound include a compound having a Ruddlesden-Popper type layered perovskite structure.

[0039] The photoelectric conversion layer 3 of the second unit cell 101B has, for example, an exposed portion on the first unit cell 101A side.

[0040] [Electron Transport Layer 4] The electron transport layer 4 contains an electron transport material. The electron transport material may be a semiconductor. The electron transport layer 4 may be formed from a semiconductor having a band gap of 3.0 eV or more. This allows visible light and infrared light to transmit to the photoelectric conversion layer 3.

[0041] Examples of electron transporting materials are organic or inorganic n-type semiconductors.

[0042] Examples of organic n-type semiconductors include imide compounds, quinone compounds, and fullerenes and their derivatives. Examples of inorganic n-type semiconductors include metal oxides, metal nitrides, and perovskite oxides. Examples of metal oxides include oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, or Cr. Examples of metal oxides include TiO2 or SnO2. Examples of metal nitrides include GaN. Examples of perovskite oxides include SrTiO3 or CaTiO3.

[0043] The electron transport layer 4 may be made of a semiconductor having a band gap of 6.0 eV or more. Examples of such a semiconductor include alkali metal or alkaline earth metal halides such as lithium fluoride and calcium fluoride, alkali metal oxides such as magnesium oxide, and silicon dioxide. In this case, in order to ensure the electron transport properties of the electron transport layer 4, the electron transport layer 4 may have a thickness of, for example, 10 nm or less.

[0044] The electron transport layer 4 is formed by, for example, a coating method, a printing method, or a vapor deposition method. Examples of coating methods include a doctor blade method, a bar coating method, a spray method, a dip coating method, an inkjet method, a slit coating method (i.e., a die coating method), and a spin coating method. An example of a printing method is a screen printing method. If necessary, the electron transport layer 4 may be prepared by mixing multiple materials, and then pressurized or baked. When the material of the electron transport layer 4 is an organic low-molecular-weight substance or an inorganic semiconductor, the electron transport layer 4 can also be prepared by a vacuum vapor deposition method.

[0045] The electron transport layer 4 may include a plurality of layers made of different materials.

[0046] FIG. 4 is a cross-sectional view schematically illustrating a third modified example of the solar cell module according to the first embodiment. As in the solar cell module 130 of the third modified example shown in FIG. 4, the electron transport layer 4 may be composed of multiple layers. In the modified example shown in FIG. 4, the electron transport layer 4 includes, for example, a first layer 9 and a second layer 8. The first layer 9 is provided between the second layer 8 and the second electrode 5. The second layer 8 includes a compound in which a main element having a π-conjugated system is composed of carbon atoms. An example of a compound in which a main element having a π-conjugated system is composed of carbon atoms is fullerene. The first layer 9 includes a phenanthroline derivative. By configuring the electron transport layer 4 in this manner, the solar cell module 130 can improve the electron transport capability from the photoelectric conversion layer 3 to the electron transport layer 4 and further to the second electrode 5. This can further improve the conversion efficiency of the solar cell module.

[0047] The phenanthroline derivative can improve device characteristics by being provided between an organic material and an electrode. That is, in a solar cell module, for example, when an organic material is used as an electron transport material, it is desirable that the electron transport layer 4 include a first layer containing a phenanthroline derivative. In this case, the first layer is provided so as to be in contact with the second electrode 5, for example. An example of the phenanthroline derivative is bathocuproine.

[0048] When the electron transport layer 4 includes a first layer containing a phenanthroline derivative, the first conductive material constituting the second electrode 5 is preferably a metal material, and particularly preferably contains at least one selected from the group consisting of silver, aluminum, and copper. Diffusion of the metal material into the phenanthroline derivative improves the electron transport ability of the electron transport layer 4, thereby improving the conversion efficiency of the solar cell module.

[0049] [Second Electrode 5] The second electrode 5 has electrical conductivity and is made of a first conductive material.

[0050] The second electrode 5 does not have to be light-transmitting. The second electrode 5 is disposed, for example, so as to face the first electrode 2 with the photoelectric conversion layer 3 interposed therebetween. In other words, the second electrode 5 is disposed on the opposite side of the photoelectric conversion layer 3 from the first electrode 2.

[0051] As described above, the first conductive material is, for example, a metal material. When the first conductive material is a metal material, a good electron transport capability can be achieved from the photoelectric conversion layer 3 to the second electrode 5. Therefore, the conversion efficiency of the solar cell module 100 can be improved.

[0052] The metal material may include, for example, at least one selected from the group consisting of silver, aluminum, and copper, or may be at least one selected from the group consisting of silver, aluminum, and copper. The second electrode 5 formed from such a metal material can further improve the conversion efficiency of the solar cell module 100. Note that, when the second electrode 5 includes at least one selected from the group consisting of silver, aluminum, and copper, the electron transport ability of the electron transport layer 4 is improved, thereby achieving a further improvement in conversion efficiency.

[0053] [Connection Member 6] The connection member 6 electrically connects the second electrode 5 of the first unit cell 101A and the first electrode 2 of the second unit cell 101B. The connection member 6 is conductive. The connection member 6 is made of a second conductive material.

[0054] 1 and 2, the connection member 6 may be provided so as to cover the entire surface of the second electrode 5, or may be provided so as to be in contact with a portion of the second electrode 5 as shown in Fig. 3. The connection member 6, for example, is in contact with at least a portion of the second electrode 5 and is disposed along the sidewall of the first unit cell 101A so as to be in contact with the first electrode 2 of the second unit cell 101B.

[0055] As described above, the second conductive material is, for example, a conductive oxide material. When the second conductive material is a conductive oxide material, even if the connecting member 6 is in contact with the photoelectric conversion layer 3 on the side wall of the unit cell 101A, it is possible to effectively suppress a decrease in conversion efficiency over time due to a reaction between the second conductive material constituting the connecting member 6 and the perovskite compound.

[0056] The conductive oxide material may include, for example, at least one selected from the group consisting of indium tin oxide and fluorine-doped tin oxide, or may be at least one selected from the group consisting of indium tin oxide and fluorine-doped tin oxide. By forming the connection member 6 from such a material, it is possible to realize a connection member 6 that has good conductivity and can more effectively suppress a decrease in conversion efficiency over time due to a reaction with the perovskite compound.

[0057] [Method for Manufacturing Solar Cell Module 100] The solar cell module 100 can be manufactured, for example, by the following method.

[0058] The unit cells 101 arranged on the substrate 1 can be fabricated using known methods for fabricating unit cells in solar cell modules. For example, first, a precursor layer for the first electrode 2 is formed on the surface of the substrate 1. The precursor layer for the first electrode 2 can be formed, for example, by chemical vapor deposition or sputtering. Next, dividing grooves 102 are formed to divide the precursor layer for the first electrode 2 into multiple unit cells. The dividing grooves 102 can be formed by laser scribing, which focuses and irradiates a laser beam, or mechanical scribing, which scrapes the precursor layer with a hardened metal blade. Next, a multilayer film is formed including a precursor layer for the photoelectric conversion layer 3, a precursor layer for the electron transport layer 4, and a precursor layer for the second electrode 5. The precursor layer for the photoelectric conversion layer 3 can be formed, for example, by solution coating, printing, or vapor deposition. The precursor layer for the electron transport layer 4 can be formed, for example, by solution coating, printing, or vapor deposition. The precursor layer for the second electrode 5 can be formed, for example, by chemical vapor deposition or sputtering. Dividing grooves 103 are formed to divide the multilayer film into a plurality of unit cells. In this manner, a plurality of unit cells are formed on the substrate 1. Next, a connecting member 6 is formed to electrically connect adjacent unit cells. The connecting member 6 can be formed, for example, by forming a thin film for forming the connecting member 6 using chemical vapor deposition or sputtering, and then patterning the thin film into a predetermined shape. The patterning method is not particularly limited, and examples that can be used include patterning using a metal mask, or separation by laser scribing or mechanical scribing. In this manner, the solar cell module 100 is obtained.

[0059] Second Embodiment FIG. 5 is a cross-sectional view schematically showing a solar cell module according to a second embodiment.

[0060] As shown in FIG. 5 , the solar cell module 200 according to the second embodiment differs from the solar cell module 100 according to the first embodiment in that the first unit cell 201A and the second unit cell 201B further include a hole transport layer 7 disposed between the photoelectric conversion layer 3 and the first electrode 2.

[0061] By providing the hole transport layer 7 in the first unit cell 201A and the second unit cell 201B, the conversion efficiency of the solar cell module can be improved.

[0062] The hole transport layer 7 may be provided in only one of the first unit cell 201A and the second unit cell 201B. That is, at least one selected from the group consisting of the first unit cell 201A and the second unit cell 201B may include the hole transport layer 7.

[0063] The hole transport layer 7 will be specifically described below.

[0064] [Hole Transport Layer 7] The hole transport layer 7 contains a hole transport material. The hole transport material is a material that transports holes. The hole transport material is, for example, an organic semiconductor or an inorganic semiconductor.

[0065] Examples of organic semiconductors are triphenylamine, triallylamine, phenylbenzidine, phenylenevinylene, tetrathiafulvalene, vinylnaphthalene, vinylcarbazole, thiophene, aniline, pyrrole, carbazole, triptycene, fluorene, azulene, pyrene, pentacene, perylene, acridine, or phthalocyanine.

[0066] Representative examples of organic semiconductors used as hole transport materials include 2,2',7,7'-tetrakis[N,N-di-P-methoxyphenylamino]-9,9'-spirobifluorene (hereinafter referred to as "spiro-OMeTAD"), poly[bis(4-phenyl)(2,4,6-triphenylmethyl)amine] (hereinafter referred to as "PTAA"), poly(3-hexylthiophene-2,5-diyl) (hereinafter referred to as "P3HT"), poly(3,4-ethylenedioxythiophene) (hereinafter referred to as "PEDOT"), and copper phthalocyanine (hereinafter referred to as "CuPC").

[0067] The inorganic semiconductor used as the hole transport material is a p-type semiconductor. Examples of inorganic semiconductors include CuO, CuGaO, CuSCN, CuI, and NiO. x , MoO x, VO, or a carbon material such as graphene oxide, where x satisfies x>0.

[0068] The hole transport layer 7 may include multiple layers made of different materials. For example, multiple layers may be stacked so that the ionization potentials of the hole transport layers 7 are successively smaller than the ionization potential of the photoelectric conversion layer 3, thereby improving the hole transport properties.

[0069] The thickness of the hole transport layer 7 may be 1 nm or more and 1000 nm or less, or 10 nm or more and 50 nm or less. This allows sufficient hole transport properties to be exhibited. Therefore, the solar cell module 200 can maintain low resistance and achieve high photoelectric conversion efficiency.

[0070] The hole transport layer 7 is formed by, for example, a coating method, a printing method, or a vapor deposition method. Examples of coating methods include a doctor blade method, a bar coating method, a spray method, a dip coating method, an inkjet method, a slit coating method (i.e., a die coating method), and a spin coating method. An example of a printing method is a screen printing method. If necessary, the hole transport layer 7 may be prepared by mixing multiple materials, and then pressurized or baked. When the material of the hole transport layer 7 is an organic low-molecular-weight substance or an inorganic semiconductor, the hole transport layer 7 can also be prepared by a vacuum vapor deposition method.

[0071] The hole transport layer 7 may contain not only a hole transport material but also an additive to enhance conductivity. Examples of the additive are a supporting electrolyte, a solvent, or a dopant. The supporting electrolyte and the solvent have the effect of stabilizing holes in the hole transport layer 7. The dopant has the effect of increasing the number of holes in the hole transport layer 7.

[0072] Examples of supporting electrolytes include ammonium salts, alkaline earth metal salts, and transition metal salts. Examples of ammonium salts include tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, imidazolium salts, and pyridinium salts. Examples of alkali metal salts include lithium perchlorate and potassium tetrafluoride. Examples of alkaline earth metal salts include lithium bis(trifluoromethanesulfonyl)imide and calcium(II) bis(trifluoromethanesulfonyl)imide. Examples of transition metal salts include zinc(II) bis(trifluoromethanesulfonyl)imide and tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalt(III) tris(trifluoromethanesulfonyl)imide.

[0073] An example of the dopant is a fluorine-containing aromatic boron compound, such as tris(pentafluorophenyl)borane.

[0074] The solvent contained in the hole transport layer 7 may have excellent ion conductivity. The solvent may be an aqueous solvent or an organic solvent. To further stabilize the solute, the solvent contained in the hole transport layer 7 may be an organic solvent. Examples of organic solvents are heterocyclic compound solvents such as tert-butylpyridine, pyridine, and n-methylpyrrolidone.

[0075] Ionic liquids may be used as the solvent. The ionic liquids may be used alone or in combination with other solvents. Ionic liquids are desirable because of their low volatility and high flame retardancy.

[0076] Examples of ionic liquids are imidazolium-based ionic liquids such as 1-ethyl-3-methylimidazolium tetracyanoborate, pyridine-based ionic liquids, alicyclic amine-based ionic liquids, aliphatic amine-based ionic liquids, or azonium amine-based ionic liquids.

[0077] FIG. 6 is a cross-sectional view schematically illustrating a modified solar cell module according to the second embodiment. As in the modified solar cell module 210 illustrated in FIG. 6 , the electron transport layer 4 may be composed of multiple layers. In the modified example illustrated in FIG. 6 , the electron transport layer 4 includes a first layer 9 containing, for example, a phenanthroline derivative and a second layer 8 containing a compound having a π-conjugated system in which the main element is composed of carbon atoms. The first layer 9 is provided between the second layer 8 and the second electrode 5. The first layer 9 and the second layer 8 are as described for the solar cell module 130 according to the third modified example of the first embodiment. The electron transport layer 4 having such a configuration in the solar cell module 210 can improve the electron transport capability from the photoelectric conversion layer 3 to the electron transport layer 4 and further to the second electrode 4. Therefore, the conversion efficiency of the solar cell module can be further improved.

[0078] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0079] (Technology 1) A solar cell module comprising: a substrate; and a first unit cell and a second unit cell disposed on the substrate and electrically connected to each other, wherein each of the first unit cell and the second unit cell comprises, from the substrate side, a first electrode, a photoelectric conversion layer, an electron transport layer, and a second electrode, in this order; the photoelectric conversion layer contains a perovskite compound; the second electrode of the first unit cell is electrically connected to the first electrode of the second unit cell by a connecting member; the second electrode is made of a first conductive material; and the connecting member is made of a second conductive material different from the first conductive material and is in contact with the photoelectric conversion layer of the first unit cell.

[0080] With the above configuration, the solar cell module of Technology 1 can appropriately select the first conductive material constituting the second electrode and the second conductive material constituting the connecting member, and therefore can maintain good conversion efficiency while suppressing a decrease in conversion efficiency over time and improving reliability.

[0081] (Technology 2) The solar cell module according to Technology 1, wherein at least one selected from the group consisting of the first unit cell and the second unit cell further includes a hole transport layer disposed between the photoelectric conversion layer and the first electrode.

[0082] With the above configuration, holes generated in the photoelectric conversion layer can be efficiently transferred to the first electrode, thereby realizing a solar cell module with improved conversion efficiency.

[0083] (Technology 3) The solar cell module according to Technology 1 or 2, wherein the electron transport layer includes a first layer containing a phenanthroline derivative, and the first layer is in contact with the second electrode.

[0084] With the above configuration, electrons generated in the photoelectric conversion layer can be efficiently transferred to the second electrode, thereby realizing a solar cell module with improved conversion efficiency.

[0085] (Technology 4) The solar cell module according to any one of Technologies 1 to 3, wherein the electron transport layer includes: a first layer including a phenanthroline derivative; and a second layer including a compound having a π-conjugated system in which a main element is composed of carbon atoms; and the first layer is provided between the second layer and the second electrode.

[0086] With the above configuration, electrons generated in the photoelectric conversion layer can be efficiently transferred to the second electrode, thereby realizing a solar cell module with improved conversion efficiency.

[0087] (Technology 5) The solar cell module according to any one of Technologies 1 to 4, wherein the first conductive material is a metal material, and the second conductive material is a conductive oxide material.

[0088] With the above configuration, the solar cell module of Technique 5 can achieve good conversion efficiency and more reliably suppress the deterioration of conversion efficiency over time.

[0089] (Technology 6) The solar cell module according to Technology 5, wherein the metal material includes at least one selected from the group consisting of silver, aluminum, and copper.

[0090] With the above configuration, electrons generated in the photoelectric conversion layer can be efficiently transferred to the second electrode, thereby realizing a solar cell module with improved conversion efficiency.

[0091] (Technology 7) The solar cell module according to Technology 5 or 6, wherein the conductive oxide material is at least one selected from the group consisting of indium tin oxide and fluorine-doped tin oxide.

[0092] The above-described configuration makes it possible to realize a connecting member that has good electrical conductivity and can more effectively suppress a decrease in conversion efficiency over time due to a reaction with a perovskite compound.

[0093] (Technology 8) The solar cell module according to any one of Technologies 1 to 7, wherein the first electrode of the first unit cell and the first electrode of the second unit cell are separated from each other by a dividing groove.

[0094] With the above configuration, it is possible to maintain good conversion efficiency while suppressing deterioration of the conversion efficiency over time, thereby improving reliability.

[0095] (Technology 9) The solar cell module according to any one of Technologies 1 to 8, wherein the second electrode of the first unit cell and the second electrode of the second unit cell are spaced apart from each other.

[0096] With the above configuration, it is possible to maintain good conversion efficiency while suppressing deterioration of the conversion efficiency over time, thereby improving reliability.

[0097] (Technology 10) The solar cell module according to any one of Technologies 1 to 9, wherein in the first unit cell, the second electrode is not in contact with the photoelectric conversion layer.

[0098] With the above configuration, it is possible to maintain good conversion efficiency while suppressing deterioration of the conversion efficiency over time, thereby improving reliability.

[0099] (Technology 11) The solar cell module according to any one of Technologies 1 to 10, wherein the reactivity between the second conductive material and the perovskite compound is lower than the reactivity between the first conductive material and the perovskite compound.

[0100] With the above configuration, it is possible to maintain good conversion efficiency while suppressing deterioration of the conversion efficiency over time, thereby improving reliability.

[0101] (Technology 12) The solar cell module according to any one of Techniques 1 to 11, wherein the photoelectric conversion layer of the second unit cell has an exposed portion on the first unit cell side.

[0102] With the above configuration, it is possible to maintain good conversion efficiency while suppressing deterioration of the conversion efficiency over time, thereby improving reliability.

[0103] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present invention is not limited to the following examples.

[0104] (Example 1 and Comparative Example 1) In Example 1, one cell having the same configuration as the first unit cell 201A shown in FIG. 6 was fabricated on a substrate and used as an evaluation sample for evaluating conversion efficiency. In Comparative Example 1, the evaluation sample was the cell of Example 1 without the second electrode. Conversion efficiency was evaluated using the evaluation samples of Example 1 and Comparative Example 1. FIG. 7A is a cross-sectional view schematically showing the configuration of the evaluation sample of Example 1, and FIG. 7B is a cross-sectional view schematically showing the configuration of the evaluation sample of Comparative Example 1.

[0105] The components and connecting members of the cell fabricated on the substrate in Example 1 are as follows. Comparative Example 1 is the cell of Example 1 except that the second electrode 5 is removed, and all other components are the same as those of Example 1. That is, in Comparative Example 1, as shown in FIG. 7B, the connecting member 6 was provided in direct contact with the bathocuproine layer 9. Note that "FA" represents "NHCHNH" and "MA" represents "CHNH". Substrate 1: Glass substrate (thickness: 0.6 mm) First electrode 2: Indium tin oxide (ITO) (thickness: 150 nm) Hole transport layer 7: PEDOT:PSS (thickness: 30 nm) Photoelectric conversion layer 3: FAMAPbSnI3 (thickness: 900 nm) Fullerene layer 8: Fullerene (C60) (thickness: 20 nm) Bathocuproine layer 9: Bathocuproine (thickness: 6 nm) Second electrode 5: Silver (thickness: 30 nm) Connecting member 6: Indium tin oxide (ITO) (thickness: 150 nm)

[0106] In Example 1, a cell was prepared as an evaluation sample in the following manner.

[0107] First, a glass substrate cut into a 25 mm square was prepared as the substrate 1 .

[0108] Next, a first electrode 2 made of ITO having a thickness of 150 nm was formed on the substrate 1 by sputtering.

[0109] Next, the first electrode 2 was cut using a laser patterning device.

[0110] Next, a hole transport layer raw material solution was applied onto the first electrode 2 by spin coating to form a hole transport layer 7. A PEDOT:PSS dispersion liquid (manufactured by Heraeus) was used as the hole transport layer raw material solution.

[0111] Next, a photoelectric conversion layer raw material solution was applied onto the hole transport layer 7 using a spin coating method to form a photoelectric conversion layer 3. The photoelectric conversion layer raw material solution was prepared by preparing 0.58 mol / L PbI (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.87 mol / L SnI (manufactured by Sigma-Aldrich Co., Ltd.), 0.087 mol / L SnF (manufactured by Sigma-Aldrich Co., Ltd.), 0.58 mol / L formamidinium iodide (manufactured by GreatCell Solar, hereinafter referred to as "FAI"), and 0.87 mol / L methylammonium iodide (manufactured by GreatCell Solar, hereinafter referred to as "MAI") and dissolving them in a mixed solution of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and N,N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The mixing ratio of dimethyl sulfoxide to N,N-dimethylformamide in the mixed solution was 1:4 (volume ratio).

[0112] Next, a 20 nm thick fullerene layer 8 and a 6 nm thick bathocuproine layer 9 were successively formed on the photoelectric conversion layer 3 by vapor deposition, thereby forming the electron transport layer 4 .

[0113] Next, a silver film having a thickness of 30 nm was formed on the electron transport layer 4 by vapor deposition to form a second electrode 5 .

[0114] Next, using a laser patterning device, the periphery of the stack of the hole transport layer 7, the photoelectric conversion layer 3, the electron transport layer 4, and the second electrode 5 was removed with a laser.

[0115] Next, a sputtering method was used to form ITO having a thickness of 150 nm, thereby forming a connection member 6 that contacts the side walls of the hole transport layer 7, photoelectric conversion layer 3, and electron transport layer 4 from above the second electrode 5 and contacts the first electrode.

[0116] An evaluation sample of Example 1 was obtained by the above method.

[0117] In Comparative Example 1, an evaluation sample was produced in the same manner as in Example 1, except that the process of producing the second electrode 5 was not carried out.

[0118] The obtained evaluation samples of Example 1 and Comparative Example 1 were evaluated for conversion efficiency by the method described below.

[0119] (Example 2 and Comparative Example 2) In Example 2, a solar cell module was fabricated in which five combinations of first unit cell 201A and second unit cell 201B shown in Fig. 6 were provided, i.e., six unit cells were arranged on a substrate and connected to each other in series. In Comparative Example 2, the unit cells of Example 1 were not provided with a connecting member, and instead, the second electrode was extended along the side wall of the unit cell and brought into contact with the first electrode of the adjacent unit cell, thereby achieving electrical connection between the unit cells. In Comparative Example 2, as in Example 1, a solar cell module was fabricated in which six unit cells were connected to each other in series.

[0120] The components and connecting members of the unit cells fabricated on the substrate in Example 2 are as follows. As described above, in Comparative Example 2, the connecting member 6 was not fabricated, and the second electrode 5 was extended to connect the unit cells, but all other components were the same as in Example 2. FIG. 8 is a cross-sectional view schematically showing the solar cell module fabricated in Comparative Example 2. Substrate 1: Glass substrate (thickness: 0.6 mm) First electrode 2: Indium tin oxide (ITO) (thickness: 150 nm) Hole transport layer 7: PEDOT:PSS (thickness: 30 nm) Photoelectric conversion layer 3: FAMAPbSnI3 (thickness: 900 nm) Second layer 8: Fullerene (C60) (thickness: 20 nm) First layer 9: Bathocuproine (thickness: 6 nm) Second electrode 5: Silver (thickness: 100 nm) Connecting member 6: Indium tin oxide (ITO) (thickness: 150 nm)

[0121] In Example 2, a solar cell module was fabricated as follows.

[0122] First, a glass substrate cut into a 25 mm square was prepared as the substrate 1 .

[0123] Next, a first electrode 2 made of ITO having a thickness of 150 nm was formed on the substrate 1 by sputtering.

[0124] Next, in the first separation step, a laser patterning device was used to separate the first electrode 2 into six pieces.

[0125] Next, a hole transport layer raw material solution was applied onto the first electrode 2 by spin coating to form a hole transport layer 7. A PEDOT:PSS dispersion liquid (manufactured by Heraeus) was used as the hole transport layer raw material solution.

[0126] Next, a photoelectric conversion layer raw material solution was applied onto the hole transport layer 7 by spin coating to form the photoelectric conversion layer 3. The photoelectric conversion layer raw material solution was the same as in Example 1.

[0127] Next, a 20 nm thick fullerene layer 8 and a 6 nm thick bathocuproine layer 9 were successively formed on the photoelectric conversion layer 3 by vapor deposition, thereby forming the electron transport layer 4 .

[0128] Next, a silver film having a thickness of 100 nm was formed on the electron transport layer 4 by vapor deposition to form a second electrode 5 .

[0129] Next, in the second separation step, a laser patterning device was used to separate the hole transport layer 7, the photoelectric conversion layer 3, the electron transport layer 4, and the second electrode 5 into six pieces.

[0130] Next, a sputtering method was used to form ITO having a thickness of 150 nm, thereby forming a connection member 6 that contacts the side walls of the hole transport layer 7, photoelectric conversion layer 3, and electron transport layer 4 from above the second electrode 5 and that contacts the first electrode 2.

[0131] Next, in the third separation step, the connecting member 6 was separated into six pieces using a laser patterning device.

[0132] Through the above steps, the solar cell module of Example 2 was obtained.

[0133] In Comparative Example 2, the process for producing the second electrode 5 was different from that in Example 2, and furthermore, the connecting member 6 was not formed. Otherwise, the solar cell module of Comparative Example 2 was produced in the same manner as in Example 2.

[0134] In Comparative Example 2, a second separation step was performed before the step of forming the second electrode 5 in the steps of Example 2. After the second separation step, the second electrode 5 was formed instead of the connection member 6. After the second electrode was formed, the second electrode 5 was separated into six pieces by a third separation step.

[0135] The solar cell modules obtained in Example 2 and Comparative Example 2 were evaluated for conversion efficiency and change in conversion efficiency over time by the methods described below.

[0136] (Evaluation of Conversion Efficiency (Initial Efficiency)) The evaluation samples of Example 1 and Comparative Example 1 and the solar cell modules of Example 2 and Comparative Example 2 were evaluated for current-voltage characteristics (i.e., IV characteristics).

[0137] The characteristics were evaluated using a solar simulator (manufactured by Bunkoukeiki Co., Ltd.) and an electrochemical analyzer ALS (manufactured by BAS Co., Ltd.). The solar cell module was irradiated with simulated sunlight at 1 sun. The output of the solar simulator was 100 mW / cm. 2 The output current value was measured using an electrochemical analyzer while changing the applied voltage, thereby measuring the IV characteristics of the evaluation samples of Example 1 and Comparative Example 1 and the solar cell modules of Example 2 and Comparative Example 2.

[0138] 9 is a graph showing IV curves of the evaluation samples of Example 1 and Comparative Example 1. FIG. 10 is a graph showing IV curves of the solar cell modules of Example 2 and Comparative Example 2.

[0139] The measurement results for the evaluation samples of Example 1 and Comparative Example 1 are shown in Table 1. The measurement results for the solar cell modules of Example 2 and Comparative Example 2 are shown in Table 2. In the table, J SC represents the short-circuit current density, and V oc represents the open circuit voltage, FF represents the fill factor, and PCE represents the conversion efficiency.

[0140] (Evaluation of Changes in Conversion Efficiency Over Time) The solar cell modules of Example 2 and Comparative Example 2 were stored at 25°C for 32 days from the day of production. For each solar cell module, the conversion efficiency on the first day (initial efficiency) and the conversion efficiency after 32 days were determined, and the ratio of the conversion efficiency after 32 days to the initial efficiency (conversion efficiency after 32 days / initial efficiency) was calculated as the retention rate. The results are shown in Table 3.

[0141]

[0142]

[0143]

[0144] As shown in Table 1, the evaluation sample of Example 1, in which both the second electrode 5 and the connecting member 6 were provided and the second electrode was in contact with the bathocuproine layer 9 of the electron transport layer, had a higher conversion efficiency than the evaluation sample of Comparative Example 1, in which the second electrode 5 was not provided and the connecting member 6 also served as the second electrode 5. It was confirmed that by providing the second electrode 5 and the connecting member 6 separately and using suitable conductive materials for each, as in Example 1, a higher conversion efficiency could be obtained than by using a single conductive material for both.

[0145] The results in Table 3 show that the solar cell module of Example 2 had a higher maintenance rate than the solar cell module of Comparative Example 2. In the solar cell module of Comparative Example 2, the silver constituting the second electrode 5 was in contact with the photoelectric conversion layer 3 on the sidewall of the unit cell, which presumably caused a reaction between the silver and the perovskite compound contained in the photoelectric conversion layer 3, resulting in degradation of the perovskite compound, and therefore a decrease in conversion efficiency. On the other hand, in the solar cell module of Example 2, the conductive materials for the second electrode 5 and the connecting member 6 were different from each other, and ITO, which does not easily react with perovskite compounds, was used for the connecting member 6. Therefore, in the solar cell module of Example 2, a decrease in conversion efficiency over time was suppressed, and reliability was presumably improved.

[0146] In the solar cell module of Example 2, a second electrode 5 and a connecting member 6 are provided, and the conductive materials of the second electrode 5 and the connecting member 6 are different from each other. However, the solar cell module of Example 2 has an initial efficiency almost the same as that of a conventional solar cell module (the solar cell module of Comparative Example 2) in which the second electrode 5 also functions as a connecting member, and is able to maintain a good conversion efficiency.

[0147] From the above results, it was confirmed that a solar cell module having a second electrode made of a first conductive material and a connecting member made of a second conductive material different from the first conductive material can improve reliability without significantly reducing conversion efficiency.

[0148] The present disclosure can maintain good conversion efficiency for a long period of time, and therefore has extremely high industrial applicability.

[0149] REFERENCE SIGNS LIST 1 substrate 2 first electrode 3 photoelectric conversion layer 4 electron transport layer 5 second electrode 6 connection member 7 hole transport layer 8 second layer 9 first layer 100, 110, 120, 130, 200, 210 solar cell module 101A, 201A first unit cell 101B, 201B second unit cell

Claims

1. A solar cell module comprising: a substrate; and a first unit cell and a second unit cell arranged on the substrate and electrically connected to each other, wherein each of the first unit cell and the second unit cell comprises, from the substrate side, a first electrode, a photoelectric conversion layer, an electron transport layer, and a second electrode, in this order; the photoelectric conversion layer contains a perovskite compound; the second electrode of the first unit cell is electrically connected to the first electrode of the second unit cell by a connecting member; the second electrode is made of a first conductive material; and the connecting member is made of a second conductive material different from the first conductive material and is in contact with the photoelectric conversion layer of the first unit cell.

2. The solar cell module according to claim 1, wherein at least one selected from the group consisting of the first unit cell and the second unit cell further comprises a hole transport layer disposed between the photoelectric conversion layer and the first electrode.

3. The solar cell module according to claim 1, wherein the electron transport layer includes a first layer containing a phenanthroline derivative, and the first layer is in contact with the second electrode.

4. The solar cell module according to claim 1, wherein the electron transport layer includes a first layer containing a phenanthroline derivative and a second layer containing a compound having a π-conjugated system in which a main element is composed of carbon atoms, and the first layer is provided between the second layer and the second electrode.

5. The solar cell module according to claim 1, wherein the first conductive material is a metal material, and the second conductive material is a conductive oxide material.

6. The solar cell module according to claim 5, wherein the metal material includes at least one selected from the group consisting of silver, aluminum, and copper.

7. The solar cell module according to claim 5, wherein the conductive oxide material includes at least one selected from the group consisting of indium tin oxide and fluorine-doped tin oxide.

8. The solar cell module according to claim 1, wherein the first electrode of the first unit cell and the first electrode of the second unit cell are separated from each other by a dividing groove.

9. The solar cell module according to claim 1, wherein the second electrode of the first unit cell and the second electrode of the second unit cell are spaced apart from each other.

10. The solar cell module according to claim 1, wherein in the first unit cell, the second electrode does not contact the photoelectric conversion layer.

11. The solar cell module according to claim 1, wherein the reactivity between the second conductive material and the perovskite compound is lower than the reactivity between the first conductive material and the perovskite compound.

12. The solar cell module according to claim 1, wherein the photoelectric conversion layer of the second unit cell has an exposed portion on the side of the first unit cell.

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