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 photoelectric conversion structure (21) containing silicon, a first transparent substrate (11), a second photoelectric conversion structure (12) containing a perovskite compound, and a second transparent substrate (14), wherein the first photoelectric conversion structure (21), the first transparent substrate (11), the second photoelectric conversion structure (12), and the second transparent substrate (14) are arranged in this order, and the thickness (T1) of the first transparent substrate (11) is greater than the thickness (T2) of the second transparent substrate (14).

Description

Technical Field

[0001] This disclosure relates to tandem solar cells.

Background Art

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

[0003] A base material joint is provided between the base material and the first glass member, and an intermediate joint is disposed between the first glass member and the second glass member. With this configuration, a first space and a second space are formed inside the bonded body of Patent Document 1. Solar cell 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, it is possible to improve the mechanical shock resistance of the bonded body. Due to this difference in thickness, excellent absorbability against external shocks and pressures is exhibited, and the shock resistance of the entire bonded body is improved.

Prior Art Documents

Patent Documents

[0005] [[ID=3​​​​​​​​​​​​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 photoelectric conversion structure containing silicon, a first transparent substrate, a second photoelectric conversion structure containing a perovskite compound, and a second transparent substrate, wherein the first photoelectric conversion structure, the first transparent substrate, 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 Embodiment 1 of this 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. [Figure 5] This is a cross-sectional view showing the schematic configuration of a tandem solar cell according to Embodiment 2 of the present disclosure. [Figure 6] This is a cross-sectional view showing the schematic configuration of a comparative example of the tandem solar cell described above. [Modes for carrying out the invention]

[0015] [Embodiment 1] Embodiment 1 of this disclosure will be described in detail below.

[0016] In the following drawings, the thickness, length, width, etc. of each layer are merely schematic diagrams and do not limit the present disclosure. However, for matters clearly defined in the embodiments, the present disclosure shall be interpreted in accordance with those provisions.

[0017] Also, in the following drawings, only the configurations necessary for mainly explaining the present disclosure are described, and configurations that are 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 Embodiment 1 of the present disclosure. FIG. 1 is an arbitrary cross-section obtained by cutting the tandem solar cell 1 in a plane perpendicular to the light-receiving surface 14A of the tandem solar cell 1 where the light LS is incident, and is a schematic diagram for facilitating the 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 the upper layer, a silicon cell 20 disposed in the lower layer, and a backsheet 30 disposed below the silicon cell 20. Hereinafter, when viewed from the tandem solar cell 1, the direction in which the light LS arrives is defined as "up", and the opposite direction is defined as "down".

[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 perspective of the 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 in which the light LS arrives so that the light LS passes through the tandem solar cell 1 in the above order. With this sequential arrangement, the perovskite cell 10 can efficiently absorb light in a relatively short wavelength range, and the silicon cell 20 can efficiently convert the relatively long wavelength light that has passed through.

[0021] With this arrangement, the light-receiving surface 14A of the tandem solar cell 1 becomes the surface of the perovskite cell 10 in the direction from which the light LS arrives. Furthermore, the perovskite cell 10 is lightweight and highly flexible due to its thin-film structure, contributing to the overall weight reduction and improved bending resistance of the tandem solar cell 1. This also includes cases where the light LS is incident from the back surface opposite to the light-receiving surface 14A, which is the side of the silicon cell 20, and contributes to photoelectric conversion. Moreover, this does not exclude cases where the back surface opposite to the light-receiving surface 14A shown in Figure 1 is used as the light-receiving surface. In such cases, the components on the back side of this disclosure only need to be transparent, or if not, they should be made transparent, etc., and the configuration of this disclosure can be applied as is or with appropriate modifications, as long as there are no contradictions. Furthermore, this does not exclude cases where it is used as a double-sided light-receiving type. The configuration of this disclosure can be applied as is or with appropriate modifications, as long as there are no contradictions.

[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 makes it possible to combine different types of solar cells, thereby reducing manufacturing costs and simplifying maintenance. The perovskite cell 10 has a first transparent substrate 11, a second photoelectric conversion structure 12, a sealing member 13, and a second transparent substrate 14. The first transparent substrate 11 serves as a support substrate when fabricating the second photoelectric conversion structure 12.

[0023] 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 fabricated by stacking these plurality of thin film layers on the first transparent substrate 11.

[0024] 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.

[0025] 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 first transparent substrate 11, the sealing member 13 is positioned to cover the second photoelectric conversion structure 12 from the side opposite to the first 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.

[0026] The second transparent substrate 14 is positioned on the outermost side of the elements constituting the tandem solar cell 1 and serves to protect the tandem solar cell 1 from external impacts. Furthermore, the second transparent substrate 14, together with the first transparent substrate 11 and the sealing member 13, also plays a role in more completely sealing the second photoelectric conversion structure 12. This sealing structure prevents the intrusion of moisture and contaminants, thereby improving the overall durability of the second photoelectric conversion structure 12. In addition, the second transparent substrate 14 has excellent light transmittance, contributing to improved light reception efficiency.

[0027] The first transparent substrate 11 and the second transparent substrate 14 are light-transmitting substrates LS. From the viewpoint of protecting the second photoelectric conversion structure 12 and protecting it from water vapor, the first transparent substrate 11 and the second transparent substrate 14 are preferably made of glass. However, this disclosure is not limited to a configuration in which the first transparent substrate 11 and the second transparent substrate 14 are made of glass, and transparent resin materials such as polycarbonate or acrylic may also be used.

[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 backsheet 30 protects the tandem solar cell 1 and enhances its durability. Since the tandem solar cell 1 consists of stacked perovskite cells 10 and silicon cells 20, the backsheet 30 requires high flexibility and adhesive properties.

[0034] Next, we will briefly explain the manufacturing process of the tandem solar cell 1.

[0035] The perovskite cell 10 is fabricated as follows: A second photoelectric conversion structure 12 is fabricated on a first transparent substrate 11, and a sealing member 13 is placed on top of it. Subsequently, the second transparent substrate 14 is placed on top of the sealing member 13 to complete the perovskite cell 10.

[0036] The silicon cell 20 is manufactured as follows: The second photoelectric conversion structure 12 is manufactured, and the sealing member 22 is placed so as to cover the second photoelectric conversion structure 12, thereby protecting the second photoelectric conversion structure 12 from the external environment.

[0037] The fabrication of the perovskite cell 10 and the silicon cell 20 may be carried out at different times and locations, but of course, it is also possible to fabricate the perovskite cell 10 and the silicon cell 20 consecutively in that order.

[0038] Finally, the tandem solar cell 1 is completed by attaching the backsheet 30 to the attached perovskite cell 10 and silicon cell 20 from the silicon cell 20 side.

[0039] (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.

[0040] As described in the "Problems the Invention Aims to Solve" section 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.

[0041] As shown in Figure 1, by making the thickness T1 of the first transparent substrate 11 thicker than the thickness T2 of the second transparent substrate 14, the stress on the silicon cell 20 is effectively relieved, so that the distance between the neutral plane X1 of the tandem solar cell 1 and the center plane 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.

[0042] (neutral plane) Referring to Figures 1 to 4, the thickness T1 of the first transparent substrate 11, the thickness T2 of the second transparent substrate 14, and the neutral surface X1 that is created within the tandem solar cell 1 when the tandem solar cell 1 is bent will be explained.

[0043] Figure 2 is a cross-sectional view of a tandem solar cell 101 in which the relative thickness T1 of the first transparent substrate 11 and the thickness T2 of the second transparent substrate 14 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 1014 is thicker than the thickness T101 of the first transparent substrate 1011. 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 1011 and the thickness T102 of the second transparent substrate 1014.

[0044] 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.

[0045] By comparing Figure 1 and Figure 2, it can be seen that by making the thickness T1 (thickness T101) of the first transparent substrate 11 (first transparent substrate 1011) thicker than the thickness T2 (thickness T102) of the second transparent substrate 14 (second transparent substrate 1014), the neutral plane X1 (neutral plane X101) moves closer to the silicon cell 20 (silicon cell 1020). As a result, 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) to the neutral plane X1 (neutral plane X101) in the thickness direction of the silicon cell 20 (silicon cell 1020) in a cross-sectional view of the tandem solar cell 1 (tandem solar cell 101).

[0046] 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.

[0047] As shown in Figure 1, as the silicon cell 20 approaches the neutral plane X1, the neutral plane X1 is located within the first transparent substrate 11 in a cross-sectional view of the tandem solar cell 1. Here, the expression "the silicon cell 20 approaches the neutral plane X1" indicates that 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. Furthermore, the expression "gets closer" means that, if we define 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 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 above-mentioned virtual plane.

[0048] Furthermore, when the thickness T1 of the first transparent substrate 11 is greater than the thickness T2 of the second transparent substrate 14, the larger the difference between thickness T2 and thickness T1, the closer the neutral plane X1 gets to the center plane in the thickness direction of the first transparent substrate 11. This is because the proportion of the thickness T1 of the first transparent substrate 11 to the total 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 14, which is located in the outermost layer and protects the entire tandem solar cell 1.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] [Embodiment 2] Embodiment 2 of this disclosure will be described below. Note that Embodiment 2 will differ from Embodiment 1 in this description. The background and method of identifying the neutral plane described in Embodiment 1 are also applicable to Embodiment 2, but will not be explained again to avoid duplication.

[0060] Furthermore, in order to understand the configuration of Embodiment 2, the correspondence with Embodiment 1 will be clear, and the components that use common terminology can be easily understood by appropriately changing the component numbers.

[0061] Figure 5 is a cross-sectional view showing the schematic configuration of a tandem solar cell 2 according to Embodiment 2 of this disclosure. Embodiment 2 employs a superstraight type configuration.

[0062] In Embodiment 1, a substrate-type configuration is adopted. As shown in Figure 1, in the substrate type, the first transparent substrate 11 supporting the second photoelectric conversion structure 12 is positioned on the side opposite to the light-receiving surface. On the other hand, in Embodiment 2, as shown in Figure 5, the second transparent substrate 41 supporting the second photoelectric conversion structure 42 is positioned on the light-receiving surface side.

[0063] As shown in Figure 5, the tandem solar cell 2 comprises a perovskite cell 40 arranged in the upper layer, a silicon cell 50 arranged in the lower layer, and a backsheet 60 arranged below the silicon cell 50. Hereafter, with reference to the tandem solar cell 2, the direction from which light LS arrives will be defined as "up," and the opposite direction will be defined as "down."

[0064] The light LS passes through the perovskite cell 40 and then the silicon cell 50. The perovskite cell 40 is a perovskite solar cell. The silicon cell 50 is a silicon solar cell. With this arrangement, the light-receiving surface of the tandem solar cell 2 is the surface of the perovskite cell 40 that is in the direction from which the light LS arrives.

[0065] The tandem solar cell 2 is a so-called mechanical tandem solar cell in which a perovskite cell 40 and a silicon cell 50 are mechanically assembled.

[0066] The perovskite cell 40 comprises a first transparent substrate 44, a sealing member 43, a second photoelectric conversion structure 42, and a second transparent substrate 41. The second transparent substrate 41 serves as a support substrate when fabricating the second photoelectric conversion structure 42.

[0067] The second photoelectric conversion structure 42 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 42 is fabricated by stacking these plurality of thin film layers on the second transparent substrate 41.

[0068] The sealing member 43 is positioned to cover the second photoelectric conversion structure 42. Specifically, since the second photoelectric conversion structure 42 is positioned on the second transparent substrate 41, the sealing member 43 is positioned to cover the second photoelectric conversion structure 42 from the side opposite to the second transparent substrate 41 as viewed from the second photoelectric conversion structure 42. The first transparent substrate 44, the second transparent substrate 41, and the sealing member 43 constitute a sealing structure that more completely seals the second photoelectric conversion structure 42.

[0069] The silicon cell 50 includes a first photoelectric conversion structure 51 and a sealing member 52. The first photoelectric conversion structure 51 contains silicon and is specifically manufactured by cutting it out from a silicon substrate after various processes have been carried out on the silicon substrate.

[0070] The backsheet 60 protects the tandem solar cells 2 and enhances their durability.

[0071] Next, we will briefly explain the manufacturing process of the tandem solar cell 2.

[0072] The perovskite cell 40 is fabricated as follows: A second photoelectric conversion structure 42 is fabricated on a second transparent substrate 41, and a sealing member 43 is placed on top of it. Subsequently, the first transparent substrate 44 is placed on the sealing member 43 to complete the perovskite cell 40.

[0073] The silicon cell 50 is manufactured as follows: a first photoelectric conversion structure 51 is manufactured, and a sealing member 52 is placed over the first photoelectric conversion structure 51, thereby protecting the first photoelectric conversion structure 51 from the external environment.

[0074] The fabrication of the perovskite cell 40 and the silicon cell 50 may be carried out at different times and locations, but of course, it is also possible to fabricate the perovskite cell 40 and the silicon cell 50 consecutively in that order.

[0075] Finally, the tandem solar cell 1 is completed by attaching the backsheet 60 to the attached perovskite cell 40 and silicon cell 50 from the silicon cell 50 side.

[0076] Next, with reference to Figures 5 and 6, we will explain the thickness T21 of the first transparent substrate 44, the thickness T22 of the second transparent substrate 41, and the neutral plane X2 that is created within the tandem solar cell 2 when the tandem solar cell 2 is bent.

[0077] Figure 6 is a cross-sectional view of a tandem solar cell 201 in which the relative thickness T21 of the first transparent substrate 44 and the thickness T22 of the second transparent substrate 41 are reversed compared to Figure 5. Each element in Figure 6 corresponds to each element in Figure 5, and the number "20" is added to the beginning of the component number. In the configuration of Figure 6, the thickness T2022 of the second transparent substrate 2041 is thicker than the thickness T2021 of the first transparent substrate 2044. The only difference between Figure 6 and Figure 5 is this relative thickness. The position of the neutral plane X202 when the tandem solar cell 201 is bent changes due to the reversal of the relative thickness T2021 of the first transparent substrate 2044 and the thickness T2022 of the second transparent substrate 2041.

[0078] By comparing Figure 5 and Figure 6, it can be seen that by making the thickness T21 (thickness T2021) of the first transparent substrate 44 (first transparent substrate 2044) thicker than the thickness T22 (thickness T2022) of the second transparent substrate 41 (second transparent substrate 2041), the neutral plane X2 (neutral plane X202) moves closer to the silicon cell 50 (silicon cell 2050). As a result, comparing the distance H2 between the silicon cell 50 and the neutral plane X2 shown in Figure 5 with the distance H202 between the silicon cell 2050 and the neutral plane X202 shown in Figure 6, the distance H2 shown in Figure 5 is smaller than the distance H202 shown in Figure 6. Here, distances H2 and H202 represent the distance from the central plane Y2 (central plane Y202) to the neutral plane X2 (neutral plane X202) in the thickness direction of the silicon cell 50 (silicon cell 2050) in a cross-sectional view of the tandem solar cell 2 (tandem solar cell 202).

[0079] In other words, in Figure 5, compared to Figure 6, the silicon cell 50 is closer to the neutral plane X2, and the stress applied to the silicon cell 50 is reduced. As a result, the reliability of the tandem solar cell 2 is improved.

[0080] [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.

[0081] 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.

[0082] 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.

[0083] (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.

[0084] 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, then it can be considered that the configuration of the Disclosure is being used.

[0085] (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.

[0086] 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.

[0087] (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.

[0088] 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.

[0089] 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.

[0090] (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.

[0091] [Note] (Aspect 1) A tandem solar cell according to Embodiment 1 of the present disclosure comprises a first photoelectric conversion structure containing silicon, a first transparent substrate, a second photoelectric conversion structure containing a perovskite compound, and a second transparent substrate, wherein the first photoelectric conversion structure, the first transparent substrate, 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.

[0092] (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 neutral surface of the bent tandem solar cell is located within the first transparent substrate.

[0093] (Aspect 3) In the tandem solar cell according to aspect 3 of the present disclosure, in aspect 2, the distance between the neutral plane and the first photoelectric conversion structure is shorter than the distance between the neutral plane and the second photoelectric conversion structure.

[0094] (Aspect 4) In the tandem solar cell according to aspect 4 of the present disclosure, in aspect 3, 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.

[0095] (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.

[0096] (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.

[0097] (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.

[0098] (Pattern 8) A tandem solar cell according to aspect 8 of the present disclosure further comprises a sealing structure for sealing the second photoelectric conversion structure in any of aspects 1 to 7, wherein the sealing structure has at least one of the first transparent substrate or the second transparent substrate.

[0099] (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.

[0100] (Aspect 10) In the tandem solar cell according to embodiment 10 of the present disclosure, in embodiment 8, the sealing structure includes the first transparent substrate and a sealing member disposed to cover the second photoelectric conversion structure from the side opposite to the side on which the first transparent substrate is disposed relative to the second photoelectric conversion structure.

[0101] (Aspect 11) The tandem solar cell according to embodiment 11 of the present disclosure further comprises a sealing member for sealing the first photoelectric conversion structure in any of embodiments 1 to 10 above.

[0102] 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]

[0103] 1, 2 Tandem Solar Cells 10, 40 perovskite cells 11, 44 First transparent substrate 12, 42 Second Photoelectric Conversion Structure 12C, 21C output terminals 13, 22, 43, 52 Sealing member 14, 41 Second transparent substrate 14A light receiving surface 20, 50 Silicon Cells 21, 51 First Photoelectric Conversion Structure 30, 60 Backseat X1, X2 midplane

Claims

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

2. The tandem solar cell according to claim 1, 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.

3. The tandem solar cell according to claim 1 or 2, 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.

4. The first transparent substrate includes glass, The tandem solar cell according to claim 1 or 2, wherein the second transparent substrate includes glass.

5. The first photoelectric conversion structure and the second photoelectric conversion structure each have an output terminal, The tandem solar cell according to claim 1 or 2, wherein the current generated in the first photoelectric conversion structure and the second photoelectric conversion structure is taken out from their respective output terminals.

6. The second photoelectric conversion structure is further provided with a sealing structure, The tandem solar cell according to claim 1 or 2, wherein the sealing structure comprises at least one of the first transparent substrate or the second transparent substrate.

7. The tandem solar cell according to claim 6, 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.

8. The tandem solar cell according to claim 6, wherein the sealing structure comprises the first transparent substrate and a sealing member disposed to cover the second photoelectric conversion structure from the side opposite to the side on which the first transparent substrate is disposed.

9. The tandem solar cell according to claim 1 or 2, further comprising a sealing member for sealing the first photoelectric conversion structure.

Images