Perovskite solar cell

Abstract

This perovskite solar cell is provided with: a conductive layer that is disposed on a substrate and is electrically conductive; a plurality of solar battery cells disposed on the conductive layer; a plurality of electrodes that electrically connect the plurality of solar battery cells; and an insulating film that covers at least the solar battery cells and the plurality of electrodes, and insulates between the adjacent electrodes. The film thickness of the insulating film on the conductive layer between the electrodes is less than or equal to half the height of the electrodes.

Description

Perovskite solar cells

[0001] The present disclosure relates to perovskite solar cells.

[0002] A perovskite solar cell is a type of solar cell that converts solar light energy into electrical energy. A perovskite solar cell is formed by stacking a conductive layer, a solar cell having a photoelectric conversion layer, and a counter electrode in this order on a substrate (see, for example, Patent Documents 1 and 2). The counter electrode is a plurality of electrodes arranged on the solar cell with a space between them.

[0003] Patent Document 1 describes the use of a metal such as gold or a metal oxide as electrodes placed on a solar cell. The solar cell and electrodes are covered with a protective layer that protects the perovskite solar cell from oxygen, water, etc., and therefore a protective layer made of resin or the like exists between the electrodes.

[0004] Patent Document 2 describes the use of a carbon electrode as the electrode disposed on the solar cell.

[0005] JP 2018-163938 A JP 2020-88316 A

[0006] In the perovskite solar cell described in Patent Document 1, the electrodes are covered with a sealing layer, and because a sealing layer is present between the electrodes, metal elements in the electrodes are likely to diffuse into the sealing layer, causing leakage current and potentially impairing the insulation between the electrodes. Furthermore, if gold, which has a low diffusion coefficient, is used as an electrode to ensure insulation between the electrodes, there is the problem of increased production costs for the perovskite solar cell.

[0007] The perovskite solar cell described in Patent Document 2 uses carbon with a small diffusion coefficient as a carbon electrode, which can reduce the production cost of the perovskite solar cell while suppressing leakage current. However, because the carbon material that makes up the carbon electrode is an aggregate of particles, if a load is applied to the carbon electrode during the formation of a protective layer, for example, some of the particles or aggregates may fall off between the electrodes, causing a short circuit between the electrodes. This can result in a decrease in the voltage of the perovskite solar cell and a deterioration in performance.

[0008] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a perovskite solar cell that can insulate multiple electrodes formed on the solar cell from one another.

[0009] A characteristic configuration of the perovskite solar cell according to the present disclosure is that it comprises an electrically conductive layer disposed on a substrate, a plurality of solar cells disposed on the conductive layer, a plurality of electrodes electrically connecting the solar cells, and an insulating film covering at least the solar cells and the electrodes and providing insulation between adjacent electrodes, wherein the film thickness of the insulating film on the conductive layer between the electrodes is equal to or less than half the height of the electrodes.

[0010] According to this configuration, the thickness of the insulating film on the conductive layer between the electrodes is less than half the height of the electrodes, so there is no dielectric material between the electrodes, or the amount of dielectric material is small. This significantly reduces the capacitance between the electrodes, and the elements in the electrodes are less likely to diffuse into the insulating film, suppressing an increase in leakage current and ensuring insulation between the electrodes. Furthermore, since metals or metal oxides other than gold can be used as electrodes, the production cost of perovskite solar cells can be reduced. Furthermore, even when carbon electrodes, which are weaker than metal electrodes, are used as electrodes, the insulating film functions as a protective film for the carbon electrodes. Therefore, even if a protective layer or the like is formed to protect the solar cell by thermocompression or the like, portions of the carbon electrodes will not fall off between the electrodes. In this way, a perovskite solar cell has been provided that ensures insulation between the electrodes and prevents short circuits due to electrode damage.

[0011] 1 is a schematic diagram showing the configuration of a perovskite solar cell; 2 is a schematic plan view of a perovskite solar cell; 3 is a schematic diagram showing a longitudinal section of a perovskite solar cell according to another embodiment.

[0012] Hereinafter, embodiments of a perovskite solar cell and a method for manufacturing a perovskite solar cell according to the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0013] 1, a perovskite solar cell 100 includes a laminate 10 and an insulating film 5. The laminate 10 is formed by laminating a substrate 1, a conductive layer 2, a solar cell 3, and an electrode 4 in this order.

[0014] [Substrate] The substrate 1 functions as a support for the conductive layer 2, the solar cell 3, etc. The substrate 1 is a transparent glass substrate, a semi-transparent glass substrate, a transparent resin substrate, etc., and has insulating properties. As shown in Fig. 2, the substrate 1 has a rectangular shape when viewed along the Z direction.

[0015] As shown in FIG. 1 , a conductive conductive layer 2 is stacked on a substrate 1. The orientation of the perovskite solar cell 100 during use is not particularly limited, but it is preferable that the perovskite solar cell 100 be used so that light is incident in the direction from the substrate 1 to the conductive layer 2. Hereinafter, the direction from the substrate 1 to the conductive layer 2 will be referred to as the "Z1 direction" (an example of a stacking direction), the opposite direction will be referred to as the "Z2 direction," and the Z1 direction and Z2 direction will be collectively referred to as the "Z direction." Furthermore, one of the directions perpendicular to the Z direction will be referred to as the "X direction," and the direction perpendicular to the Z direction and the X direction will be referred to as the "Y direction" (see FIG. 2 ). Furthermore, one side in the X direction will be referred to as the "X1 side," and the opposite side will be referred to as the "X2 side." Note that FIG. 2 is a view of the perovskite solar cell 100 shown in FIG. 1 as viewed along the Z direction.

[0016] [Conductive Layer] The conductive layer 2 is formed on one surface (the surface on the Z1 side) of the substrate 1 by CVD (chemical vapor deposition), sputtering, or the like. In this embodiment, the conductive layer 2 is formed on the entire surface of one surface of the substrate 1. The conductive layer 2 contains, for example, fluorine-doped tin oxide (FTO), tin oxide (TO), or the like as a material. The solar cell 3 is arranged (stacked) on the conductive layer 2 (the surface on the Z1 side).

[0017] [Solar Cell] In this embodiment, a plurality of (three) solar cells 3 are arranged in parallel along the X direction. In the following, when distinguishing between the three solar cells 3, the solar cell 3 arranged on the X2 side will be referred to as solar cell 3A, the solar cell 3 adjacent to solar cell 3A will be referred to as solar cell 3B, and the solar cell 3 adjacent to solar cell 3B and arranged on the X1 side will be referred to as solar cell 3C. Solar cell cells 3A to 3C are configured to have the same size (area) when viewed along the Z direction.

[0018] The solar cell 3 converts light energy into electrical energy. The solar cell 3 has an electron transport layer 31, a photoelectric conversion layer 32, and a hole transport layer 33, which are arranged in this order along the Z1 direction. When viewed along the Z direction, the electron transport layer 31, the photoelectric conversion layer 32, and the hole transport layer 33 each have a rectangular shape. In this embodiment, when viewed along the Z direction, the electron transport layer 31, the photoelectric conversion layer 32, and the hole transport layer 33 each have the same size (area).

[0019] The electron transport layer 31 is disposed on the Z1-side surface of the conductive layer 2. The electron transport layer 31 transmits (transports) electrons received from the photoelectric conversion layer 32 (described later). The electron transport layer 31 includes, as a material, a metal oxide such as titanium oxide, tin oxide, or zinc oxide. In this embodiment, the electron transport layer 31 includes multiple (three in this embodiment) insulating layers 311 extending into multiple (three in this embodiment) recesses 21 formed by removing portions of the conductive layer 2. The insulating layers 311 divide the conductive layer 2 in contact with each solar cell 3 into two sections (in the example shown in FIG. 1 , each section is divided into two sections in the X direction). While electrons can move in the electron transport layer 31 in the Z direction, they have difficulty moving in directions perpendicular to the Z direction (the X and Y directions), restricting their movement between the two sections of the conductive layer 2. The electron transport layer 31 is sometimes referred to as a "blocking layer."

[0020] Since the substrate 1, the conductive layer 2, and the electron transport layer 31 are optically transparent, light such as sunlight and indoor light is guided to the photoelectric conversion layer 32 without being substantially absorbed (or without being absorbed) by the substrate 1, the conductive layer 2, and the electron transport layer 31.

[0021] The photoelectric conversion layer 32 absorbs light energy and converts it into electrical energy. Specifically, the photoelectric conversion layer 32 absorbs light and transfers excited electrons and holes to perform photoelectric conversion. The photoelectric conversion layer 32 includes a perovskite layer made of a perovskite compound. The photoelectric conversion layer 32 also includes a porous oxide semiconductor layer (e.g., a porous titanium layer).

[0022] The hole transport layer 33 passes through (transports holes) the holes received from the photoelectric conversion layer 32. The hole transport layer 33 contains, for example, an organic compound such as chlorobenzene as a material. An electrode 4 is disposed on the hole transport layer 33 (on the Z1 side) of each solar cell 3. Therefore, the perovskite solar cell 100 in this embodiment has multiple electrodes 4 (three in this embodiment).

[0023] [Electrode] The electrode 4 is conductive and functions as a positive electrode. The electrode 4 is electrically connected to a bus bar (not shown) via the conductive layer 2. As shown in FIGS. 1 and 2 , the multiple electrodes 4 are arranged in parallel along the X direction, spaced a predetermined distance apart from each other. Each electrode 4 is arranged on the Z1-side surface (partial region) of the conductive layer 2, extending from the Z1-side surface of the hole transport layer 33 along the Z direction, via the X1-side surface of each solar cell 3. This electrically connects the solar cell 3A and the solar cell 3B via the electrode 4 and the conductive layer 2, and the solar cell 3B and the solar cell 3C via the electrode 4 and the conductive layer 2, thereby connecting the solar cells 3A to 3C in series. The multiple electrodes 4 protrude from the Z1-side surface and the X1-side surface of the solar cell 3 to the Z1-side or X1-side by the thickness of the electrode 4. A space 41 is formed between adjacent electrodes 4 (between opposing electrodes 4).

[0024] The electrode 4 is formed using, for example, a metal such as gold, platinum, silver, or copper, an alloy thereof, or an oxide conductor such as FTO or indium tin oxide (ITO). The electrode 4 may be a carbon electrode, or may contain graphite, carbon black, carbon nanotubes, carbon nanofibers, carbon fibers, graphene, fullerene, or the like as a material. The electrode 4 may contain only one of the above-mentioned materials, or may contain two or more of these materials.

[0025] Light such as sunlight enters the perovskite solar cell 100 in the Z1 direction. When the light reaches the photoelectric conversion layer 32 via the substrate 1, conductive layer 2, and electron transport layer 31, it is absorbed in the photoelectric conversion layer 32, resulting in the generation of electrons and holes. The electrons generated in the photoelectric conversion layer 32 move to the conductive layer 2 (negative electrode) via the electron transport layer 31. At the same time, the holes generated in the photoelectric conversion layer 32 move to the electrode 4 (positive electrode) electrically connected to the hole transport layer 33. When a load (not shown) is connected between the conductive layer 2 and the electrode 4, the holes combine with the electrons that have passed through the load. As a result, electricity is generated. Electricity is partitioned by the insulating layer 311, for example, and flows in the following order: conductive layer 2 located closest to the X2 side, solar cell 3A, electrode 4 formed on solar cell 3A, conductive layer 2 connecting solar cell 3A and solar cell 3B, solar cell 3B, electrode 4 formed on solar cell 3B, conductive layer 2 connecting solar cell 3B and solar cell 3C, and solar cell 3C. Note that electrons moving through the electron transport layer 31 move smoothly along the Z2 direction to reach the conductive layer 2, but as described above, movement in a direction perpendicular to the Z direction is restricted by the insulating layer 311. In other words, the perovskite solar cell 100 is configured to prevent short-circuiting.

[0026] 1 and 2, the insulating film 5 is disposed so as to cover the conductive layer 2, the solar cell 3, and the electrode 4. Specifically, the insulating film 5 covers a part of the Z1-side surface of the conductive layer 2, the side surfaces of the solar cell 3 that are not covered by the electrode 4, and the Z1-side surface and its side surfaces of the electrode 4. As shown in FIG. 1, the insulating film 5 is disposed in a space 41 formed between the electrodes 4, 4, thereby ensuring insulation between adjacent electrodes 4, 4.

[0027] The film thickness (dimension in the Z direction) of the insulating film 5 is preferably equal to or less than half the height of the electrode 4, preferably equal to or less than 1 / 5, and more preferably equal to or less than 1 / 10. If the film thickness of the insulating film 5 is greater than half the height of the electrode 4, elements contained in the electrode 4 are more likely to diffuse into the insulating film 5, resulting in an increase in leakage current. By making the insulating film 5 have such a film thickness, materials that could serve as a dielectric can be excluded from the space 41, allowing gas such as the atmosphere to exist in the space 41, making it possible to reduce the electrostatic capacitance between the electrodes 4, 4 to close to zero. This ensures electrical insulation between the electrodes 4, 4.

[0028] The thickness of the insulating film 5 disposed on the surface of the electrode 4 may be different from the thickness of the insulating film 5 disposed on the surface of the conductive layer 2 or the solar cell 3. Furthermore, as long as the insulating film 5 covers the surface of the electrode 4, the insulating film 5 does not need to be provided on the surface (the surface on the Z1 side) of the conductive layer 2. This allows the electrostatic capacitance between the electrodes 4, 4 to approach zero.

[0029] When the electrode 4 is a carbon electrode, a portion of the particles or aggregates may protrude from the edge of the carbon electrode during formation, forming a protrusion. When an external force is applied to such a carbon electrode, the protrusion falls off the carbon electrode, and a portion of the carbon electrode becomes positioned between the electrodes 4, 4, causing a short circuit. However, if the carbon electrode is covered with the insulating film 5, the carbon electrode can be prevented from falling off even if an external force is applied to the carbon electrode, and therefore, a short circuit between the electrodes 4, 4 can be suppressed.

[0030] The insulating film 5 is preferably made of an insulating material that is soluble in an alcohol-based solvent. Examples of alcohol solvents include isopropyl alcohol, isobutyl alcohol, and ethanol. The insulating material may contain, for example, perfluorocarbon and polyvinyl acetal resin. Fluorine-based resin may be included instead of polyvinyl acetal resin. The perfluorocarbon content in the insulating film 5 is preferably 1 to 10 wt %. Since the insulating film 5 is made of an insulating material that is soluble in an alcohol-based solvent, the insulating material can be dissolved in the alcohol-based solvent to prepare a solution, and the solution can be applied to the surface of the electrode 4 to form the insulating film 5.

[0031] [Method for manufacturing perovskite solar cell] Next, a description will be given of a method for manufacturing the perovskite solar cell 100. The method for manufacturing the perovskite solar cell 100 in this embodiment includes a stack formation step of forming the stack 10, and an insulating film formation step of forming the insulating film 5 on the surface of the stack 10.

[0032] First, a laminate formation step is performed to form the laminate 10. In the laminate formation step, a conductive layer 2 is formed on the Z1-side surface of the substrate 1. The conductive layer 2 may be formed by, for example, CVD (chemical vapor deposition) or sputtering. Next, laser scribing is performed to partially remove the conductive layer 2, thereby forming recesses 21. Thereafter, the solar cell 3 and the electrode 4 are formed on the Z1-side surface of the conductive layer 2 by a known method.

[0033] Next, an insulating film formation step is performed to form an insulating film 5 on the surface of the laminate 10. First, an insulating material is dissolved in an alcohol-based solvent to prepare a solution. In preparing the solution, the concentration of the insulating material may be adjusted so that the solution has a predetermined viscosity (e.g., 20 to 300 cps). Next, the solution with the adjusted concentration is applied to the surface of the laminate 10. The application may be performed using a known method such as an inkjet method, a spin coating method, a dipping method, or a screen printing method. This allows the solution to be applied to the surface, making it possible to obtain an insulating film 5 with a large area and a uniform film thickness. After applying the solution, the laminate 10 is vacuum-dried or heated to volatilize the solvent, thereby obtaining a perovskite solar cell 100.

[0034] Second Embodiment A perovskite solar cell 100 according to a second embodiment will be described with reference to Fig. 3. The perovskite solar cell 100 according to this embodiment includes a protective layer 6 that protects the solar cell 3 and the electrode 4.

[0035] As shown in FIG. 3 , the protective layer 6 includes an insulating portion 61, a conductive portion 62, and a film portion 63. The insulating portion 61 may have adhesive properties, gas barrier properties, and waterproof properties, and may be made of, for example, an olefin-based adhesive, an epoxy-based adhesive, or an acrylic-based adhesive. The insulating portion 61 may also include a getter material that adsorbs moisture and gas. The conductive portion 62 is conductive and includes, as its material, a metal oxide such as aluminum oxide or silicon oxide, or a metal such as aluminum. The film portion 63 includes, as its material, a resin such as polyethylene terephthalate. The protective layer 6 is formed by laminating the insulating portion 61, the conductive portion 62, and the film portion 63 in this order.

[0036] The protective layer 6 is rectangular in plan view and is disposed so that the insulating portion 61 faces the Z1-side surfaces of the solar cell 3 and the electrode 4. The protective layer 6 is attached to the Z1-side surfaces of the electrodes 4 by thermocompression or the like, and a load is applied to the electrodes 4 when the protective layer 6 is pressed. If the electrodes 4 are relatively low-strength carbon electrodes, without the insulating film 5, the load applied from the protective layer 6 to the electrodes 4 may cause portions of the ends of the electrodes 4 or protruding portions from the ends to chip and fall between the electrodes 4 (i.e., carbon particles and their aggregates contained in the electrodes 4 may fall between the electrodes 4). In this embodiment, the electrodes 4 are covered with the insulating film 5, which protects the ends and protruding portions of the electrodes 4. Therefore, even if a load is applied when the protective layer 6 is pressed, carbon particles or aggregates will not fall between the electrodes 4. Therefore, even when carbon electrodes are used as the electrodes 4, the insulating film 5 protects the electrodes 4, thereby preventing short circuits between the electrodes 4.

[0037] In this embodiment, the protective layer 6 has approximately the same area as the substrate 1 in a plan view, but it may be smaller or larger than the substrate 1 as long as it protects the solar cell 3 and the electrode 4.

[0038] The above-described embodiment contemplates the following configuration: (1) A perovskite solar cell 100 comprising an electrically conductive layer 2 disposed on a substrate 1, a plurality of solar cells 3 disposed on the conductive layer 2, electrodes 4 electrically connecting the plurality of solar cells 3, and an insulating film 5 covering at least the plurality of solar cells 3 and the plurality of electrodes 4 and providing insulation between adjacent electrodes 4, wherein the film thickness of the insulating film 5 on the conductive layer 2 between the electrodes 4, 4 is equal to or less than half the height of the electrodes 4.

[0039] According to this configuration, the thickness of the insulating film 5 on the conductive layer 2 between the electrodes 4, 4 is less than half the height of the electrodes 4, so that there is no dielectric material or only a small amount of dielectric material in the space 41 between the electrodes 4, 4. This significantly reduces the capacitance between the electrodes 4, and also makes it difficult for elements in the electrodes 4 (metal elements and carbon) to diffuse into the insulating film 5, suppressing leakage current and ensuring insulation between the electrodes 4. Furthermore, since metals and metal oxides other than gold can be used for the electrodes 4, the production cost of the perovskite solar cell 100 can be reduced. Furthermore, even when carbon electrodes, which have lower strength than metal electrodes, are used as the electrodes 4, the insulating film 5 functions as a protective film for the electrodes 4. Therefore, even when a protective layer 6 or the like is formed by thermocompression bonding or the like to protect the solar cell 3, portions of the electrodes 4 will not fall off between the electrodes 4. This also prevents short circuits between the electrodes 4 due to damage to the electrodes 4.

[0040] (2) In the perovskite solar cell 100 of (1), the electrode 4 is preferably a carbon electrode.

[0041] According to this configuration, because the electrode 4 is a carbon electrode containing a carbon material with a small diffusion coefficient, carbon is less likely to diffuse into the insulating film 5 disposed between the electrodes 4, 4. This suppresses the occurrence of leakage current between the electrodes 4, 4 and improves the insulation between the electrodes 4, 4. This prevents short circuits between the electrodes 4, 4 and makes it possible to suppress a drop in the voltage of the perovskite solar cell 100.

[0042] (3) In the perovskite solar cell 100 of (1) or (2), the insulating film 5 is preferably made of an insulating material that is soluble in an alcohol-based solvent.

[0043] According to this configuration, the insulating material is dissolved in an alcohol-based solvent to form a solution, and the solution can be applied to the surface of the laminate 10 to form the insulating film 5. This allows the insulating film 5 to be formed over a large area with a uniform thickness, making it easy to form the insulating film 5.

[0044] (4) In the perovskite solar cell 100 of any one of (1) to (3), the perovskite solar cell 100 preferably further comprises a protective layer 6 that protects the solar cell 3 and the electrode 4, and the protective layer 6 is disposed on the insulating film 5.

[0045] According to this configuration, the protective layer 6 protects the solar cell 3 and the electrode 4, thereby suppressing deterioration of the perovskite solar cell 100 due to contact with oxygen, water, etc., and improving durability. Furthermore, even if a carbon electrode, which is weaker than a metal electrode because it is an agglomerate of particles, is used as the electrode, the insulating film 5 functions as a protective film for the electrode 4, so even if a protective layer 6 or the like that protects the solar cell 3 is formed by thermocompression bonding or the like, a portion of the electrode 4 will not fall off between the electrodes 4, 4. This prevents a short circuit between the electrodes 4, 4 due to damage to the electrode 4, and makes it possible to suppress a drop in the voltage of the perovskite solar cell 100.

[0046] The present disclosure is applicable to perovskite solar cells having a solar cell disposed on a conductive layer and a plurality of electrodes electrically connecting the solar cell.

[0047] 1: Substrate, 2: Conductive layer, 3: Solar cell, 4: Electrode, 5: Insulating film, 6: Protective layer, 100: Perovskite solar cell

Claims

1. A perovskite solar cell comprising: an electrically conductive layer disposed on a substrate; a plurality of solar cells disposed on the conductive layer; a plurality of electrodes electrically connecting the solar cells; and an insulating film covering at least the solar cells and the electrodes and providing insulation between adjacent electrodes, wherein the film thickness of the insulating film on the conductive layer between the electrodes is less than half the height of the electrodes.

2. The perovskite solar cell according to claim 1, wherein the electrode is a carbon electrode.

3. The perovskite solar cell according to claim 1, wherein the insulating film is made of an insulating material that is soluble in an alcohol-based solvent.

4. The perovskite solar cell according to any one of claims 1 to 3, further comprising a protective layer that protects the solar cell and the electrodes, the protective layer being disposed on the insulating film.

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