Tandem solar cells

Abstract

To realize a tandem solar cell that contributes to improving the overall reliability of tandem solar cells. [Solution] A tandem solar cell (1) comprises a first transparent substrate (30), a first photoelectric conversion structure (21) containing silicon, a second photoelectric conversion structure (12) containing a perovskite compound, and a second transparent substrate (11), wherein the first transparent substrate (30), the first photoelectric conversion structure (21), the second photoelectric conversion structure (12), and the second transparent substrate (11) are arranged in this order, and the thickness of the first transparent substrate (30) is greater than the thickness of the second transparent substrate (11).

Description

[Technical Field]

[0001] The present disclosure relates to tandem solar cells. [Background Art]

[0002] The joined body of Patent Document 1 includes a structure for improving durability and functionality. Specifically, the joined body of Patent Document 1 has a structure in which a first glass member is arranged on a base material, and a second glass member is further laminated thereon.

[0003] A base material bonding portion is provided between the base material and the first glass member, and an intermediate bonding portion is arranged between the first glass member and the second glass member. With this configuration, a first space and a second space are formed inside the joined body of Patent Document 1. Solar battery cells can be mounted in the first space and the second space.

[0004] By making the second glass member thicker than the first glass member, the mechanical impact resistance of the joined body can be improved. This difference in thickness exerts excellent absorbability against external impact and pressure, and improves the impact resistance of the entire joined body. [Prior Art Literature] [Patent Literature]

[0005] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2021-46337 [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] In tandem solar cells, which use perovskite cells in the upper layer and silicon cells in the lower layer, resistance to external stress and impact is necessary as one of the factors contributing to the reliability of the solar cell, especially when considering outdoor applications. Furthermore, it is necessary to consider cases where the entire tandem solar cell is used for portable applications, taking advantage of the flexibility and light weight characteristics of perovskite cells. For this reason, it is necessary to further enhance the impact resistance of the entire tandem solar cell.

[0007] In particular, solar panels installed outdoors are expected to be subjected to various external loads, such as wind loads, snow loads, rain impact, and hail impact. Bending deformation caused by these loads can adversely affect the performance and lifespan of solar panels. Furthermore, even indoors and in living spaces, panels may be subjected to loads such as being stepped on, leaned on, collided with, or having objects placed on them.

[0008] Therefore, improving the overall impact resistance of tandem solar cells is crucial for enhancing their resistance to these diverse loads. Furthermore, improving the overall impact resistance of tandem solar cells is also necessary to meet the load-bearing test standards for solar panels installed outdoors.

[0009] In the joint described in Patent Document 1, the impact resistance of the entire joint was enhanced by employing a structure in which the thickness of the second glass member was greater than the thickness of the first glass member.

[0010] However, the Disclosers have found that in tandem solar cells, which require resistance to external stress and shock, adopting the structure of Patent Document 1 leads to a decrease in the reliability of the silicon cells and a decrease in the overall reliability of the tandem solar cell.

[0011] One aspect of this disclosure aims to realize a tandem solar cell that contributes to improving the overall reliability of tandem solar cells. [Means for solving the problem]

[0012] To solve the above problems, a tandem solar cell according to one aspect of the present disclosure comprises a first transparent substrate, a first photoelectric conversion structure containing silicon, a second photoelectric conversion structure containing a perovskite compound, and a second transparent substrate, wherein the first transparent substrate, the first photoelectric conversion structure, the second photoelectric conversion structure, and the second transparent substrate are arranged in this order, and the thickness of the first transparent substrate is greater than the thickness of the second transparent substrate. [Effects of the Invention]

[0013] According to one aspect of this disclosure, a tandem solar cell can be realized that contributes to improving the overall reliability of the tandem solar cell. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view showing the schematic configuration of a tandem solar cell according to an embodiment of the present disclosure. [Figure 2] This is a cross-sectional view showing the schematic configuration of a comparative example of the tandem solar cell described above. [Figure 3] This is a schematic diagram illustrating the neutral plane that is created when the above-mentioned tandem solar cell is bent, and shows the tandem solar cell before it is bent. [Figure 4] This is a schematic diagram illustrating the neutral plane that is created when the above-mentioned tandem solar cell is bent, and shows the tandem solar cell after it has been bent. [Modes for carrying out the invention]

[0015] [Embodiment] The embodiments of this disclosure will be described in detail below.

[0016] In the following drawings, the thickness, length, width, etc., of each layer are for illustrative purposes only and do not limit this disclosure. However, matters explicitly defined in the embodiments shall be interpreted in accordance with those definitions.

[0017] Also, in the following drawings, only components necessary mainly for explaining the present disclosure are described, and components not necessary for explaining the present disclosure may be omitted.

[0018] (Schematic Configuration of Tandem Solar Cell) FIG. 1 is a cross-sectional view showing a schematic configuration of a tandem solar cell according to an embodiment of the present disclosure. FIG. 1 is an arbitrary cut surface obtained by cutting the tandem solar cell 1 along a plane perpendicular to the light receiving surface 11A of the tandem solar cell 1 on which light LS is incident, and is a schematic diagram for facilitating understanding of the configuration of the tandem solar cell 1.

[0019] As shown in FIG. 1, the tandem solar cell 1 includes a perovskite cell 10 disposed in an upper layer, a silicon cell 20 disposed in a lower layer, a first transparent substrate 30, and an intermediate film 14 disposed between the perovskite cell 10 and the silicon cell 20. Hereinafter, as viewed from the tandem solar cell 1, the direction from which the light LS arrives is defined as "upper", and the opposite direction is defined as "lower".

[0020] The light LS passes through the perovskite cell 10 and the silicon cell 20 in this order. The perovskite cell 10 is a perovskite solar cell. The silicon cell 20 is a silicon solar cell. From the viewpoint of photoelectric conversion efficiency of the perovskite solar cell and the silicon solar cell, the perovskite cell 10 and the silicon cell 20 are arranged in this order with respect to the direction from which the light LS arrives, so that the light LS passes through the tandem solar cell 1 in the above-mentioned order. With this ordered arrangement, the perovskite cell 10 can efficiently absorb light in a relatively short wavelength region, and the silicon cell 20 can efficiently convert transmitted light in a relatively long wavelength region.

[0021] With this arrangement, the light-receiving surface 11A of the tandem solar cell 1 is the surface of the perovskite cell 10 on the side from which the light LS arrives. Furthermore, due to its thin-film structure, the perovskite cell 10 is lightweight and has excellent flexibility, contributing to weight reduction of the entire tandem solar cell 1 and improvement of bending resistance. Note that this also includes cases where the light LS is incident from the back surface opposite to the light-receiving surface 11A, which is the side of the silicon cell 20, and contributes to photoelectric conversion. Furthermore, the present disclosure does not exclude cases where the back surface opposite to the light-receiving surface 11A shown in FIG. 1 is used as a light-receiving surface; in such cases, it is only required that the constituent members on the back surface side according to the present disclosure have light-transmitting properties, or if not, they may be formed to have light-transmitting properties. As long as there is no inconsistency, the configuration of the present disclosure may be applied as it is, or may be modified appropriately and applied. Furthermore, the present disclosure does not exclude application as a double-sided light-receiving type; as long as there is no inconsistency, the configuration of the present disclosure may be applied as it is, or may be modified appropriately and applied.

[0022] The tandem solar cell 1 is a so-called mechanical tandem solar cell in which a perovskite cell 10 and a silicon cell 20 are mechanically assembled. This configuration enables combining different types of solar cells, and can achieve reduction in manufacturing cost and facilitation of maintenance.

[0023] The perovskite cell 10 includes a second transparent substrate 11, a second photoelectric conversion structure 12, and a sealing member 13. The second transparent substrate 11 serves as a supporting substrate when producing the second photoelectric conversion structure 12.

[0024] The second photoelectric conversion structure 12 contains a perovskite compound, and has a structure in which a thin film layer containing the perovskite compound and a plurality of thin film layers are stacked. The second photoelectric conversion structure 12 is produced by stacking these plurality of thin film layers on the second transparent substrate 11.

[0025] The second photoelectric conversion structure 12 is provided with an output terminal 12C consisting of two extraction electrodes 12A and 12B. The current generated from the second photoelectric conversion structure 12 is extracted to the outside of the tandem solar cell 1 via the output terminal 12C. The second photoelectric conversion structure 12 may be a photoelectric conversion element containing a perovskite compound, and may be a photoelectric conversion module in which multiple such photoelectric conversion elements are provided and these multiple photoelectric conversion elements are integrated.

[0026] The sealing member 13 is positioned to cover the second photoelectric conversion structure 12. Specifically, since the second photoelectric conversion structure 12 is positioned on the second transparent substrate 11, the sealing member 13 is positioned to cover the second photoelectric conversion structure 12 from the side opposite to the second transparent substrate 11 as viewed from the second photoelectric conversion structure 12. The sealing member 13 is made of, for example, resin, to ensure the long-term reliability of the second photoelectric conversion structure 12.

[0027] The second transparent substrate 11 is positioned on the outermost part of the tandem solar cell 1 and protects the tandem solar cell 1 from external impacts. Furthermore, together with the sealing member 13, the second transparent substrate 11 also plays a role in more completely sealing the second photoelectric conversion structure 12. This sealing structure prevents the intrusion of moisture and contaminants, improving the overall durability of the second photoelectric conversion structure 12. In addition, the second transparent substrate 11 has excellent light transmittance, contributing to improved light reception efficiency.

[0028] The silicon cell 20 includes a first photoelectric conversion structure 21 and a sealing member 22. The first photoelectric conversion structure 21 contains silicon and is specifically manufactured by cutting it out from a silicon substrate after undergoing various processes on the silicon substrate.

[0029] Furthermore, this disclosure is not limited to a configuration in which the first photoelectric conversion structure 21 includes silicon, but may also include a single-crystal compound semiconductor such as gallium arsenide. In this case, the first photoelectric conversion structure 21 is manufactured by cutting it from a compound semiconductor substrate after various processes have been carried out on the compound semiconductor substrate.

[0030] Furthermore, the first photoelectric conversion structure 21 may be a single photoelectric conversion element containing silicon, or it may be a photoelectric conversion module in which multiple such photoelectric conversion elements are provided and these multiple photoelectric conversion elements are integrated.

[0031] The first photoelectric conversion structure 21 has an output terminal 21C consisting of extraction electrodes 21A and 21B, and the current generated from the first photoelectric conversion structure 21 is extracted to the outside of the tandem solar cell 1 via the output terminal 21C.

[0032] The sealing member 22 seals the first photoelectric conversion structure 21 by covering it. This sealing structure protects the first photoelectric conversion structure 21 from moisture, contaminants, mechanical stress, etc. from the external environment, ensuring long-term durability and reliability.

[0033] The first transparent substrate 30 and the second transparent substrate 11 are light-transmitting substrates LS. From the viewpoint of protecting the first photoelectric conversion structure 21 and the second photoelectric conversion structure 12 and protecting them from water vapor and the like, the first transparent substrate 30 and the second transparent substrate 11 are preferably made of glass. However, this disclosure is not limited to a configuration in which the first transparent substrate 30 and the second transparent substrate 11 are made of glass, and transparent resin materials such as polycarbonate or acrylic may also be used.

[0034] In this embodiment, when the tandem solar cell 1 is observed from the side opposite to the light-receiving surface 11A, the first transparent substrate 30 is positioned as the outermost element among the components constituting the tandem solar cell 1. In this case, the first transparent substrate 30 plays a role in protecting the tandem solar cell 1 from external impacts. Furthermore, the first transparent substrate 30 also has the function of completely sealing the first photoelectric conversion structure 21, preventing the intrusion of moisture and contaminants, thereby improving the overall durability of the first photoelectric conversion structure 21.

[0035] The intermediate film 14 is a component used to bond the perovskite cell 10 and the silicon cell 20. Specifically, the intermediate film 14 plays a role in reliably insulating the second photoelectric conversion structure 12 of the perovskite cell 10 from the first photoelectric conversion structure 21 of the silicon cell 20.

[0036] However, if the perovskite cell 10 and the silicon cell 20 can be reliably bonded together by the adhesion between the sealing member 13 of the perovskite cell 10 and the sealing member 22 of the silicon cell 20, then the intermediate film 14 is not necessarily required.

[0037] Furthermore, even if the laminated structure of the sealing member 13 of the perovskite cell 10 and the sealing member 22 of the silicon cell 20 ensures reliable insulation between the second photoelectric conversion structure 12 of the perovskite cell 10 and the first photoelectric conversion structure 21 of the silicon cell 20, the use of the intermediate film 14 is not essential.

[0038] Therefore, the intermediate film 14 is not an essential component in the configuration of this disclosure.

[0039] Next, we will briefly explain the manufacturing process of the tandem solar cell 1.

[0040] The perovskite cell 10 is fabricated as follows: A second photoelectric conversion structure 12 is fabricated on a second transparent substrate 11, and a sealing member 13 is placed on top of it to complete the perovskite cell 10.

[0041] The silicon cell 20 is manufactured as follows: a first photoelectric conversion structure 21 is manufactured, and a sealing member 22 is placed over the first photoelectric conversion structure 21, thereby protecting the first photoelectric conversion structure 21 from the external environment.

[0042] The fabricated perovskite cell 10 and silicon cell 20 are bonded together via an intermediate film 14. In this process, from the viewpoint of protecting the second photoelectric conversion structure 12 of the perovskite cell 10 from the external environment, it is preferable to bond the perovskite cell 10 and silicon cell 20 as soon as possible after the perovskite cell 10 is fabricated. This is to ensure that the second photoelectric conversion structure 12 is sealed early and reliably on the sealing member 13 side. The longer the period between the fabrication of the perovskite cell 10 and the bonding of the perovskite cell 10 and silicon cell 20, the higher the risk that the second photoelectric conversion structure 12 will be affected by moisture, oxygen, and other external environmental factors.

[0043] After the perovskite cell 10 and the silicon cell 20 are bonded together, the first transparent substrate 30 is placed on the underside of the silicon cell 20 to complete the tandem solar cell 1.

[0044] (Background of this disclosure) In tandem solar cells 1, improving the overall reliability of the tandem solar cell 1 is a crucial issue. In this regard, the distance between the neutral bending surface X1 of the tandem solar cell 1 and the center surface Y1 of the silicon cell 20, as shown in Figure 1, is key. The neutral bending surface X1 is the surface where tensile and compressive stresses due to bending do not act. The greater the distance from the neutral bending surface X1, the greater the tensile and compressive stresses applied by bending. Since tensile and compressive stresses can affect the long-term performance maintenance of the tandem solar cell 1, careful consideration is necessary from a reliability standpoint.

[0045] As described in "Problems the Invention Aims to Solve" above, the tandem solar cell 1 requires resistance to external stress and shock, therefore, structural improvements are needed to minimize the impact of stress distribution on the overall reliability of the tandem solar cell 1.

[0046] As shown in Figure 1, by making the thickness T1 of the first transparent substrate 30 thicker than the thickness T2 of the second transparent substrate 11, the stress on the silicon cell 20 is effectively relieved, so that the distance H1 between the bending neutral surface X1 of the tandem solar cell 1 and the center surface Y1 of the silicon cell 20 is reduced. The disclosers have found that this stress relief not only protects the silicon cell 20 itself but also contributes to improving the reliability of the entire tandem solar cell 1, thereby ensuring the long-term reliability of the tandem solar cell 1.

[0047] (neutral plane) Referring to Figures 1 to 4, the thickness T1 of the first transparent substrate 30, the thickness T2 of the second transparent substrate 11, and the neutral plane X1 that is formed within the tandem solar cell 1 when it is bent will be explained.

[0048] Figure 2 is a cross-sectional view of a tandem solar cell 101 in which the relative thickness T1 of the first transparent substrate 30 and the thickness T2 of the second transparent substrate 11 are reversed compared to Figure 1. Each element in Figure 2 corresponds to each element in Figure 1, and the number "10" is added to the beginning of the component number. In the configuration of Figure 2, the thickness T102 of the second transparent substrate 1011 is thicker than the thickness T101 of the first transparent substrate 1030. The only difference between Figure 2 and Figure 1 is this relative thickness. When the tandem solar cell 101 is bent, the position of the neutral plane X101 changes due to the reversal of the relative thickness T101 of the first transparent substrate 1030 and the thickness T102 of the second transparent substrate 1011.

[0049] Figures 3 and 4 are schematic diagrams illustrating the neutral plane X1 that is created when the tandem solar cell 1 shown in Figure 1 is folded. Figure 3 shows the tandem solar cell 1 before folding, and Figure 4 shows the tandem solar cell 1 after folding.

[0050] By comparing Figure 1 and Figure 2, it can be seen that by making the thickness T1 (thickness T101) of the first transparent substrate 30 (first transparent substrate 1030) thicker than the thickness T2 (thickness T102) of the second transparent substrate 11 (second transparent substrate 1011), the neutral plane X1 (neutral plane X101) moves closer to the silicon cell 20 (silicon cell 1020). More specifically, in the example shown in Figure 1, the neutral plane X1 is located inside the silicon cell 20, and even more specifically, inside the first photoelectric conversion structure 21 of the silicon cell 20. When the neutral plane X1 is in this position, the stress distribution across the entire silicon cell 20 is optimized.

[0051] Under ideal conditions, the stress applied within the first photoelectric conversion structure 21 is minimized, and theoretically, the stress becomes zero when the central plane Y1 and the neutral plane X1 of the first photoelectric conversion structure 21 coincide. However, in this disclosure, it is not necessarily required that the central plane Y1 and the neutral plane X1 of the first photoelectric conversion structure 21 coincide.

[0052] The effects of this disclosure can be fully obtained as long as the neutral plane X1 is located near the first photoelectric conversion structure 21, whether inside or outside the first photoelectric conversion structure 21. For example, the configuration of this disclosure also includes the case where the neutral plane X1 is located inside the sealing member 22 that seals the first photoelectric conversion structure 21, which is considered to be near the first photoelectric conversion structure 21.

[0053] Furthermore, "nearby" is preferably a range that satisfies the following relationship: In a cross-sectional view obtained by cutting the tandem solar cell 1 with a plane perpendicular to the light-receiving surface 11A of the tandem solar cell 1, the range is one in which the distance between the neutral plane X1 and the first photoelectric conversion structure 21 is shorter than the distance between the neutral plane X1 and the second photoelectric conversion structure 12. More preferably, when a plane is defined as a virtual plane where the distance from the first photoelectric conversion structure 21 and the distance from the second photoelectric conversion structure 12 are equal, the range is one in which the distance between the neutral plane X1 and the first photoelectric conversion structure 21 is shorter than the distance between the neutral plane X1 and the virtual plane.

[0054] Furthermore, "nearby" is more preferably a range that satisfies the following relationship: In a cross-sectional view obtained by cutting the tandem solar cell 1 with a plane perpendicular to the light-receiving surface 11A of the tandem solar cell 1, the distance between the neutral plane X1 and the first photoelectric conversion structure 21 is within a range of 0.1 times the total thickness of the tandem solar cell 1 or less. In other words, it is more preferable that the neutral plane X1 is located within the range between a plane that can be formed at a distance 0.1 times the total thickness of the tandem solar cell 1 above the upper end surface of the first photoelectric conversion structure 21 and a plane that can be formed at a distance 0.1 times the total thickness of the tandem solar cell 1 below the lower end surface of the first photoelectric conversion structure 21.

[0055] As a result, when comparing the distance H1 between the silicon cell 20 and the neutral plane X1 shown in Figure 1 with the distance H101 between the silicon cell 1020 and the neutral plane X101 shown in Figure 2, the distance H1 shown in Figure 1 is smaller than the distance H101 shown in Figure 2. Here, distances H1 and H101 represent the distance from the central plane Y1 (central plane Y101) in the thickness direction of the silicon cell 20 (silicon cell 1020) to the neutral plane X1 (neutral plane X101) in a cross-sectional view of the tandem solar cell 1 (tandem solar cell 101).

[0056] In other words, in Figure 1, compared to Figure 2, the silicon cell 20 is closer to the neutral plane X1, and the stress applied to the silicon cell 20 is reduced. As a result, the reliability of the tandem solar cell 1 is improved. This is effective in improving the stress resistance of the silicon cell 20 by making it less susceptible to the effects of stress application.

[0057] Furthermore, when the thickness T1 of the first transparent substrate 30 is greater than the thickness T2 of the second transparent substrate 11, the larger the difference between thickness T2 and thickness T1, the closer the neutral plane X1 gets to the center plane Y1 of the first photoelectric conversion structure 21 of the silicon cell 20. This is because the proportion of the thickness T1 of the first transparent substrate 30 to the overall thickness of the tandem solar cell 1 becomes larger. However, the upper limit of the difference between thickness T2 and thickness T1 needs to be determined considering the overall durability of the tandem solar cell 1 and the required thickness of the second transparent substrate 11, which is located in the outermost layer and protects the entire tandem solar cell 1.

[0058] Next, a method for identifying the neutral plane will be explained. However, the identification method described below typically assumes that the bending resistance and material properties of each layer in the cross-sectional structure of the tandem solar cell 1 are substantially the same, and that the entire tandem solar cell 1 is considered to be an ideal plate-like member. However, regardless of the material properties of the layers used in the cross-sectional structure of the tandem solar cell 1, the identification method for the neutral plane described below can be used, and the effects of this disclosure will be achieved when the identified neutral plane has the configuration of this disclosure.

[0059] As shown in Figure 3, in a cross-sectional view of the tandem solar cell 1, imaginary lines S1, S2, and S3 are drawn perpendicular to the thickness direction of the first photoelectric conversion structure 21. In Figure 3, three imaginary lines S1, S2, and S3 are drawn, but this number can be appropriately changed depending on the thickness, structure, and precision requirements of the tandem solar cell 1. Figure 3 shows the state of the tandem solar cell 1 before it is bent, and the three imaginary lines S1, S2, and S3 are all straight lines. The length L2 of the imaginary lines S1, S2, and S3 indicates the distance between the two end faces V1 and V2 of the tandem solar cell 1.

[0060] It should be noted that, while this assumes the two end faces V1 and V2 are flat surfaces without irregularities, in actual products, the two end faces of the product may not be perfectly flat. In such cases, two ideal end faces can be virtually set up inside the product and used as the basis for determination.

[0061] Next, Figure 4 shows the state of the tandem solar cell 1 after it has been bent, as shown in Figure 3. In Figure 4, both ends of the tandem solar cell 1 are bent in the direction through which the light LS shown in Figure 1 passes.

[0062] As shown in Figure 4, the three imaginary lines S1, S2, and S3 are all curves. Note that in Figure 3, the imaginary lines S1, S2, and S3 were straight lines representing a plane perpendicular to the thickness direction of the tandem solar cell 1, but in Figure 4, they are curves representing a curved surface with both ends bent along the thickness direction of the tandem solar cell 1.

[0063] Here, if any of the virtual lines S1, S2, and S3 represent the neutral plane, the length of that virtual line coincides with the length L2 shown in Figure 3. This is because the neutral plane is a surface to which neither tensile nor compressive stress is applied, so if a virtual line represents the neutral plane, the deformation due to stress will be minimized before and after bending the tandem solar cell 1, and its length will not change. The lengths of the virtual lines S1, S2, and S3 are denoted as SL201, SL202, and SL203, respectively.

[0064] For example, in Figure 4, if the length SL202 of the hypothetical curved line S2 is the same as the length L2 of the hypothetical straight line S2 in Figure 3, then the plane indicated by the hypothetical line S2 is identified as the neutral plane.

[0065] If, for any of the imaginary lines S1, S2, and S3, their lengths do not all match the length L2 shown in Figure 3, the neutral plane can be identified by redrawing the imaginary lines and repeating the procedure described above.

[0066] Note that, in this explanation, we assume that the lengths of the three virtual lines S1, S2, and S3 in Figure 3 are all equal to length L2, but this is not the only case. For example, in Figure 3, the lengths of the three virtual lines S1, S2, and S3 may be different from each other, and the lengths of the three virtual lines S1, S2, and S3 may all be different from length L2. In that case, one can compare the length of the straight line virtual line S1 shown in Figure 3 with the length of the curved line virtual line S1 shown in Figure 4, the straight line virtual line S2 shown in Figure 3 with the length of the curved line virtual line S2 shown in Figure 4, and the straight line virtual line S3 shown in Figure 3 with the length of the curved line virtual line S3 shown in Figure 4.

[0067] Furthermore, there are cases where it is sufficient to determine that the neutral plane is located within at least a certain range, even without specifying its exact location. A method for determining that the neutral plane is located within at least a certain range, used in such cases, is described below. As described above, imaginary lines S1, S2, and S3 are drawn, and their lengths are measured before and after folding. If, for example, the length of imaginary line S1 after folding is longer than the length of imaginary line S1 before folding, the length of imaginary line S2 before folding is longer than the length of imaginary line S2 after folding, and the length of imaginary line S3 before folding is longer than the length of imaginary line S3 after folding, then the neutral plane can be determined to be located at least between imaginary line S1 and imaginary line S3, and furthermore, between imaginary line S1 and imaginary line S2. Similarly, if the measurement results show, for example, that the length of the virtual line S2 after bending is longer than the length of the virtual line S2 before bending, and the length of the virtual line S3 before bending is longer than the length of the virtual line S3 after bending, then the neutral plane can be determined to be located at least between the virtual lines S2 and S3.

[0068] [Definition] (Tandem-type solar cells) In this disclosure, “tandem solar cell” means a solar cell in which some or all of the light incident from the light-receiving side of the solar cell (more specifically, light having a certain wavelength band) is absorbed sequentially by two or more photoelectric conversion structures (i.e., including photoelectric conversion elements or photoelectric conversion modules; similarly in this disclosure). Alternatively, in this disclosure, “tandem solar cell” may mean a solar cell in which, in terms of configuration, two or more photoelectric conversion structures are provided sequentially from the light-receiving side to the back side of the solar cell, as viewed from the light-receiving side.

[0069] Furthermore, it is not necessary for the two or more photoelectric conversion structures to be completely superimposed when viewed from the light-receiving surface; at least a portion of them must be superimposed. Ideally, however, at least one photoelectric conversion structure should be completely superimposed on the other.

[0070] Alternatively, in this disclosure, "tandem solar cell" means, in other words, a solar cell in which some or all of the light incident from the light-receiving surface side (more specifically, light having a certain wavelength band) can pass through one photoelectric conversion structure and be incident on the other photoelectric conversion structure.

[0071] (Light receiving surface) In this disclosure, "light-receiving surface" refers to the surface on which light enters the element in a single-sided light-receiving solar cell. However, in a double-sided light-receiving solar cell, either one of the surfaces may be considered the light-receiving surface, and in that case, if one surface is considered the light-receiving surface, the opposite surface may be considered the back surface. Furthermore, if at least one of the surfaces is considered the light-receiving surface, it may be considered that the configuration of this disclosure is being used.

[0072] In other words, even if one side does not have the configuration of the Disclosure when considered as a light-receiving surface, if the other side has the configuration of the Disclosure when considered as a light-receiving surface, it can be considered that the configuration of the Disclosure is being used.

[0073] (Sealed) In this disclosure, "sealing" means that in any one cross-section of a solar cell cut perpendicular to the light-receiving surface, a resin or a low-moisture-permeable material having equivalent or less moisture permeability to a resin is arranged to cover the area where the photoelectric conversion structure is located. The resin or low-moisture-permeable material may be arranged to cover the area with a single layer, or it may be arranged to cover the area with multiple layers of resin or low-moisture-permeable material. It should be noted that even if a component is part of the photoelectric conversion structure, such as an extraction electrode, the part that exchanges electricity or other information with the outside does not necessarily need to be covered.

[0074] Furthermore, as stated above, in order to define a structure as "sealed," it is sufficient to confirm that it is a sealed structure in any one cross-section; confirmation in multiple or every cross-section is not necessary. In practice, it is impossible to confirm sealing in every cross-section, and in this disclosure, confirmation in any one cross-section is sufficient to understand that it has a similar effect in at least that cross-section or an equivalent area; this is considered sealing. It is even more preferable to confirm sealing in two cross-sections perpendicular to each other. It is even more preferable to confirm sealing in multiple arbitrary cross-sections.

[0075] (neutral plane) In this disclosure, "neutral plane" means a plane on which, when a member is bent, the length of the straight section before bending is the same as the length of the curved section after bending. However, when actually observing a cross-section, it means the "neutral line" that indicates the neutral plane, and "neutral line" means a line on which, in any cross-section obtained by cutting a member, the length of the straight section before bending is the same as the length of the curved section after bending.

[0076] Furthermore, if the aspect ratio (here, the width / height value) of the cross-section of a certain member is 20 or greater, it is sufficient to observe only a portion of the member with an arbitrarily selected aspect ratio of approximately 20.

[0077] Furthermore, when observing, multiple straight lines can be marked, and the line where the length of the marked straight line before bending is the same as the length of the marked curve after bending can be designated as the neutral line.

[0078] (transparent) In this disclosure, "transparent" or "light-transmitting" means that light is transmitted, but this does not exclude anything that reflects or absorbs even a little light. It is sufficient that it is provided on the light-receiving side of the solar cell and transmits light appropriately, and this can be considered synonymous with being provided on the light-receiving side of the photoelectric conversion structure. Therefore, as long as a tandem solar cell is performing its photoelectric conversion function as a solar cell, it can be considered transparent or light-transmitting simply by being provided on the light-receiving side of the photoelectric conversion structure, and it is not necessary to confirm the physical properties of the transmittance.

[0079] [Note] (Aspect 1) A tandem solar cell according to Embodiment 1 of the present disclosure comprises a first transparent substrate, a first photoelectric conversion structure containing silicon, a second photoelectric conversion structure containing a perovskite compound, and a second transparent substrate, wherein the first transparent substrate, the first photoelectric conversion structure, the second photoelectric conversion structure, and the second transparent substrate are arranged in this order, and the thickness of the first transparent substrate is greater than the thickness of the second transparent substrate.

[0080] (Aspect 2) In the tandem solar cell according to aspect 2 of the present disclosure, in aspect 1, in a cross-sectional view obtained by cutting the tandem solar cell with a plane perpendicular to the light-receiving surface of the tandem solar cell, the distance between the neutral surface and the first photoelectric conversion structure is shorter than the distance between the neutral surface and the second photoelectric conversion structure in the bent tandem solar cell.

[0081] (Aspect 3) In the tandem solar cell according to aspect 3 of the present disclosure, in aspect 2, when a virtual plane is defined in which the distance from the first photoelectric conversion structure and the distance from the second photoelectric conversion structure are equal, the distance between the neutral plane and the first photoelectric conversion structure is shorter than the distance between the neutral plane and the virtual plane.

[0082] (Aspect 4) In the tandem solar cell according to aspect 4 of the present disclosure, in aspect 2, the distance between the neutral plane and the first photoelectric conversion structure is 0.1 times or less the thickness of the tandem solar cell.

[0083] (Appendix 5) In the tandem solar cell according to aspect 5 of the present disclosure, in any of aspects 2 to 4 above, the neutral plane is the boundary between the compressive stress and the tensile stress applied to the tandem solar cell in the folded tandem solar cell.

[0084] (Aspect 6) In any of embodiments 1 to 5 above, the tandem solar cell according to embodiment 6 of this disclosure comprises the first transparent substrate, and the second transparent substrate, which comprises glass.

[0085] (Aspect 7) In the tandem solar cell according to embodiment 7 of the present disclosure, in any of embodiments 1 to 6 above, the first photoelectric conversion structure and the second photoelectric conversion structure each have an output terminal, and the current generated in the first photoelectric conversion structure and the second photoelectric conversion structure is taken out from their respective output terminals.

[0086] (Pattern 8) A tandem solar cell according to embodiment 8 of the present disclosure further comprises, in any of embodiments 1 to 7 above, a sealing structure for sealing the second photoelectric conversion structure, wherein the sealing structure has the second transparent substrate.

[0087] (Aspect 9) In the tandem solar cell according to embodiment 9 of the present disclosure, in embodiment 8, the sealing structure comprises the second transparent substrate and a sealing member disposed to cover the second photoelectric conversion structure from the side opposite to the side on which the second transparent substrate is arranged.

[0088] (Aspect 10) The tandem solar cell according to embodiment 10 of the present disclosure further comprises a sealing member for sealing the first photoelectric conversion structure in any of embodiments 1 to 9 above.

[0089] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. [Explanation of Symbols]

[0090] 1. 101 Tandem Solar Cells 10 Perovskite Cells 11, 1011 Second transparent substrate 11A light receiving surface 12. Second Photoelectric Conversion Structure 12C, 21C output terminals 13, 22 Sealing member 14 Intermediate film 20 Silicon Cells 21 First Photoelectric Conversion Structure 30 First transparent substrate X1 midplane

Claims

1. First transparent substrate and, A first photoelectric conversion structure containing silicon, A second photoelectric conversion structure containing a perovskite compound, Second transparent substrate and Equipped with, The first transparent substrate, the first photoelectric conversion structure, the second photoelectric conversion structure, and the second transparent substrate are arranged in this order. A tandem solar cell in which the thickness of the first transparent substrate is greater than the thickness of the second transparent substrate.

2. The tandem solar cell according to claim 1, wherein, in a cross-sectional view obtained by cutting the tandem solar cell with a plane perpendicular to the light-receiving surface of the tandem solar cell, the distance between the neutral surface and the first photoelectric conversion structure is shorter than the distance between the neutral surface and the second photoelectric conversion structure in the bent tandem solar cell.

3. The tandem solar cell according to claim 2, wherein, when a virtual plane is defined such that the distance from the first photoelectric conversion structure is equal to the distance from the second photoelectric conversion structure, the distance between the neutral plane and the first photoelectric conversion structure is shorter than the distance between the neutral plane and the virtual plane.

4. The tandem solar cell according to claim 2, wherein the distance between the neutral plane and the first photoelectric conversion structure is 0.1 times or less the thickness of the tandem solar cell.

5. The tandem solar cell according to any one of claims 2 to 4, wherein the neutral plane is the boundary between the compressive stress and the tensile stress applied to the tandem solar cell in the folded tandem solar cell.

6. The first transparent substrate includes glass, The tandem solar cell according to any one of claims 1 to 4, wherein the second transparent substrate includes glass.

7. The first photoelectric conversion structure and the second photoelectric conversion structure each have an output terminal, The tandem solar cell according to any one of claims 1 to 4, wherein the current generated in the first photoelectric conversion structure and the second photoelectric conversion structure is taken out from their respective output terminals.

8. The second photoelectric conversion structure is further provided with a sealing structure, The tandem solar cell according to any one of claims 1 to 4, wherein the sealing structure has the second transparent substrate.

9. The tandem solar cell according to claim 8, wherein the sealing structure comprises the second transparent substrate and a sealing member disposed to cover the second photoelectric conversion structure from the side opposite to the side on which the second transparent substrate is disposed.

10. A tandem solar cell according to any one of claims 1 to 4, further comprising a sealing member for sealing the first photoelectric conversion structure.

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