Solar cell and method for manufacturing solar cell

Abstract

A solar cell (1) according to the present embodiment comprises a first solar cell panel (11), a second solar cell panel (51), a first sealing layer (84), a second sealing layer (85), a third sealing layer (86), and a first protective material (81). The thickness of the first sealing layer (84) is 50-400 µm. The thickness of the second sealing layer (85) is 30-400 µm. The thickness of the third sealing layer (86) is 50-400 µm. The thickness of the first protective material (81) is 25-200 µm. The thickness of the solar cell (1) is 350-1140 µm at a location at which the first solar cell panel (11) and the second solar cell panel (51) overlap when viewed from the normal vector direction of the light-receiving surface of the first solar cell panel (11).

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to solar cells and methods for manufacturing solar cells. [Background technology]

[0002] There is a tandem solar cell, which is a stack of solar cell panels. A tandem solar cell comprises a first solar cell panel and a light-transmitting second solar cell panel stacked on the light-receiving side of the first solar cell panel. The first solar cell panel and the second solar cell panel are made of semiconductor materials with different absorption wavelength ranges. Compared to conventional solar cells, tandem solar cells can convert a wider range of wavelengths of light into electrical energy and have high energy conversion efficiency. For this reason, tandem solar cells are suitable as a power source for moving objects such as aircraft and mobility vehicles.

[0003] However, when tandem solar cells are installed in a mobile object or the like, they are subject to weight restrictions depending on the equipment on which they are installed. Tandem solar cells are formed by laminating a sealing material and a protective material onto a solar cell panel, so there is room for improvement in the configuration of the sealing material and the protective material from the perspective of achieving weight reduction. However, when tandem solar cells are made thinner in order to reduce weight, there is a possibility that the power generation efficiency will decrease due to the occurrence of surface irregularities, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Republished WO2019 / 180854 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a highly efficient and lightweight solar cell and a method for manufacturing the solar cell. [Means for solving the problem]

[0006] The solar cell of the embodiment has a first solar cell panel, a second solar cell panel, a first encapsulating layer, a second encapsulating layer, a third encapsulating layer, and a first protective material. The second solar cell panel is a light-transmitting type disposed to face the light-receiving surface of the first solar cell panel. The first encapsulating layer is laminated on the second solar cell panel from the side opposite the first solar cell panel. The thickness of the first encapsulating layer is 50 μm or more and 400 μm or less. The second encapsulating layer is disposed between the first solar cell panel and the second solar cell panel. The second encapsulating layer is laminated so as to be in direct contact with the first solar cell panel and the second solar cell panel. The thickness of the second encapsulating layer is 30 μm or more and 400 μm or less. The third encapsulating layer is laminated on the first solar cell panel from the side opposite the second encapsulating layer. The thickness of the third encapsulating layer is 50 μm or more and 400 μm or less. The first protective material is laminated on the first encapsulating layer from the side opposite the second solar cell panel. The thickness of the first protective material is 25 μm or more and 200 μm or less. The thickness of the solar cell is 350 μm or more and 1140 μm or less at the location where the first solar cell panel and the second solar cell panel overlap when viewed from the normal direction of the light-receiving surface of the first solar cell panel. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a plan view showing a layer structure of the tandem solar cell according to the embodiment. [Figure 2] FIG. 2 is a development view of a tandem solar cell according to an embodiment. [Figure 3] FIG. 2 is a plan view showing a bottom module according to the embodiment. [Figure 4] FIG. 2 is a plan view showing a top module according to the embodiment. [Figure 5] FIG. 2 is a plan view showing the positional relationship between a bottom module and a top module according to the embodiment. [Figure 6] Cross-sectional view of a tandem solar cell taken along line VI-VI in Figure 1. [Figure 7] FIG. 4 is a diagram showing an example of a heating step according to the embodiment. [Figure 8] FIG. 10 is a development view of a device including a tandem solar cell according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Solar cells and methods for manufacturing solar cells according to embodiments will be described below with reference to the drawings. In the following description, components having the same or similar functions will be designated by the same reference numerals. Duplicate descriptions of those components may be omitted.

[0009] Fig. 1 is a plan view showing the layer structure of a tandem solar cell according to an embodiment. Fig. 2 is a developed view of the tandem solar cell according to an embodiment. Note that Fig. 1 shows some layers cut away to show the layered structure of the tandem solar cell 1. As shown in Figures 1 and 2, the tandem solar cell 1 is formed in a rectangular flat plate shape. Hereinafter, the thickness direction of the tandem solar cell 1 will be simply referred to as the "thickness direction." For ease of explanation, the +X direction, -X direction, +Y direction, and -Y direction, which are perpendicular to the thickness direction, will be defined. The -X direction is the opposite direction to the +X direction. When the +X direction and the -X direction are not distinguished, they will be simply referred to as the "X direction." The +Y direction and -Y direction are directions perpendicular to the X direction. The -Y direction is the opposite direction to the +Y direction. When the +Y direction and the -Y direction are not distinguished, they will be simply referred to as the "Y direction." Furthermore, one direction in the thickness direction will be defined as the "front side," and the direction opposite to the front side will be defined as the "back side."

[0010] The tandem solar cell 1 comprises a bottom module 10 equipped with solar cells 12 that form a back cell, a top module 50 equipped with solar cells 52 that are arranged on the front side of the bottom module 10 and form a front cell, and a package 80 that houses the bottom module 10 and the top module 50. The tandem solar cell 1 is a four-terminal solar cell that extracts current from each of the bottom module 10 and the top module 50.

[0011] 3 is a plan view showing the bottom module of the embodiment, in which the outline of the package 80 is shown by imaginary lines. As shown in FIG. 3, the bottom module 10 includes multiple bottom solar cell panels 11 (first solar cell panel, other solar cell panels) connected in series. All of the bottom solar cell panels 11 are arranged along a common XY plane. At least one solar cell 12 is formed in the bottom solar cell panel 11. The bottom solar cell panel 11 may include a single solar cell 12 or multiple solar cell cells 12 connected in series and parallel. The solar cell 12 is a silicon-based solar cell that uses Si, an indirect transition semiconductor, in its light absorption layer. The solar cell 12 is, for example, a back-contact crystalline silicon solar cell having an n-type electrode and a p-type electrode on the back side of the light absorption layer. The solar cell 12 may also be a crystalline silicon solar cell or other solar cell type. Examples of the solar cell 12 include silicon-based solar cells such as monocrystalline, polycrystalline, heterojunction, and amorphous solar cells, as well as CIS-based and CIGS-based compound solar cells. Furthermore, the cell electrode structure (p-electrode, n-electrode) of the solar cell 12 may be a combination of a metal wrap-through structure and a bifacial light-receiving structure. The bottom solar cell panels 11 are arranged with their light-receiving surfaces facing the front. That is, the normal direction of the light-receiving surfaces of the bottom solar cell panels 11 is along the thickness direction. Each bottom solar cell panel 11 is formed in a rectangular shape with one pair of sides extending in the X direction and the other pair of sides extending in the Y direction in a plan view from the thickness direction. In this embodiment, each bottom solar cell panel 11 is formed in a rectangular shape with the X direction as the longitudinal direction in a plan view.

[0012] The bottom module 10 includes a plurality of bottom panel rows 11R (at least one first solar cell panel) formed by a plurality of bottom solar cell panels 11 connected in series. In each bottom panel row 11R, the bottom solar cell panels 11 are lined up at intervals in the X direction. The overall outer shape of each bottom panel row 11R is formed into a rectangular shape with the X direction as the longitudinal direction in a plan view. The bottom panel rows 11R are lined up at intervals in the Y direction. As a result, the plurality of bottom solar cell panels 11 are aligned in the X and Y directions. The overall outer shape of the aligned plurality of bottom solar cell panels 11 is formed into a rectangular shape with the X direction as the longitudinal direction. In the illustrated example, the bottom module 10 includes five bottom panel rows 11R, each formed by four bottom solar cell panels 11. However, the number of bottom solar cell panels 11 is not particularly limited. Hereinafter, the bottom panel column 11R located furthest in the +Y direction among the plurality of bottom panel columns 11R will be used as a reference, and the bottom panel column 11R located Nth in the -Y direction will be referred to as the "Nth bottom panel column 11R." The same applies to the top panel column 51R described later.

[0013] The bottom solar cell panel 11 includes a negative electrode terminal 13 electrically connected to the n-type electrode and a positive electrode terminal 14 electrically connected to the p-type electrode. When the solar cell 12 is a back-contact type solar cell, the negative electrode terminal 13 and the positive electrode terminal 14 are provided on the back surface of the bottom solar cell panel 11. The negative electrode terminal 13 is provided at the end of the bottom solar cell panel 11 in the +X direction in the odd-numbered bottom panel columns 11R, and is provided at the end of the bottom solar cell panel 11 in the -X direction in the even-numbered bottom panel columns 11R. The positive electrode terminal 14 is provided at the end of each bottom solar cell panel 11 opposite the negative electrode terminal 13.

[0014] The bottom module 10 includes an interconnector 16 , a panel row end connector 17 , and a bottom bus bar 20 .

[0015] The interconnector 16 connects adjacent bottom solar cell panels 11 in series within the bottom panel row 11R. The interconnector 16 is formed of a metal plate. For example, the interconnector 16 is formed of a copper plate, copper wire, or copper foil having solder plating layers on both main surfaces. The interconnector 16 extends across the gap between a pair of bottom solar cell panels 11 adjacent to each other in the X direction in plan view. The interconnector 16 is connected to the negative terminal 13 of one bottom solar cell panel 11 and the positive terminal 14 of the other bottom solar cell panel 11.

[0016] The panel row end connectors 17 are connected to the negative and positive terminals 13 and 14 of the bottom solar cell panels 11 in each bottom panel row 11R that are not connected to the interconnectors 16. In other words, the panel row end connectors 17 are connected to the negative and positive terminals 13 and 14 that form the electrical ends of the bottom panel row 11R. The panel row end connectors 17 are formed from a metal plate. For example, the panel row end connectors 17 are formed from the same material as the interconnectors 16. The panel row end connectors 17 protrude in the X direction from the bottom panel row 11R in a plan view.

[0017] The bottom bus bar 20 is arranged around the entire plurality of bottom solar cell panels 11 in a plan view. In this embodiment, the entire periphery of the plurality of bottom solar cell panels 11 means the periphery of the panel when the plurality of bottom solar cell panels 11 are considered as a single rectangular panel. The bottom bus bar 20 is formed of a metal plate. For example, the bottom bus bar 20 is formed of a copper plate having solder plating layers on both main surfaces. The bottom bus bar 20 extends along the Y direction. The bottom bus bars 20 are arranged so as not to contact each other. The bottom bus bar 20 includes an inter-panel bus bar 21 and a terminal bus bar 22.

[0018] The inter-panel bus bars 21 connect adjacent bottom panel columns 11R in series via the panel column end connectors 17. The inter-panel bus bars 21 are arranged on both sides of the bottom panel column 11R in the +X direction and the -X direction in a plan view. The +X direction inter-panel bus bar 21 connects the nth bottom panel column 11R and the (n+1)th bottom panel column 11R in series, where n is an even number. Specifically, the +X direction inter-panel bus bar 21 is connected to the +X direction panel column end connector 17 connected to the nth bottom panel column 11R and the +X direction panel column end connector 17 connected to the (n+1)th bottom panel column 11R. The -X direction inter-panel bus bar 21 connects the mth bottom panel column 11R and the (m+1)th bottom panel column 11R in series, where m is an odd number. Specifically, the -X direction inter-panel bus bar 21 is connected to the -X direction panel row end connector 17 connected to the mth bottom panel row 11R and the -X direction panel row end connector 17 connected to the (m+1)th bottom panel row 11R.

[0019] The terminal busbars 22 are connected to the panel row end connectors 17 that are not connected to the inter-panel busbars 21. In other words, when the series-connected bottom solar cell panels 11 are considered as one solar cell, the terminal busbars 22 are connected to the negative terminal 13 and the positive terminal 14, which are the electrical ends of one solar cell, via the panel row end connectors 17. The terminal busbars 22 are arranged on both the +X direction and the -X direction of the bottom panel row 11R in a plan view. The +X direction terminal busbar 22 is connected to the +X direction panel row end connector 17 connected to the first bottom panel row 11R. The +X direction terminal busbar 22 extends in the +Y direction from the connection with the panel row end connector 17 and is drawn out to the outside of the package 80. The -X direction terminal busbar 22 is connected to the -X direction panel row end connector 17 connected to the Nth bottom panel row 11R, where N is the number of bottom panel rows 11R. The terminal bus bar 22 in the −X direction extends in the −Y direction from the connection portion with the panel row end connector 17 and is drawn out to the outside of the package 80.

[0020] Each bottom bus bar 20 extends further in the +Y direction than each bottom panel column 11R connected to that bottom bus bar 20. For example, where m is an odd number, the +X-direction inter-panel bus bar 21 extends further in the +Y direction from its connection with the m-th bottom panel column 11R than the m-th bottom panel column 11R and connects to the (m-1)-th bottom panel column 11R. Furthermore, the +X-direction inter-panel bus bar 21 extends further in the +Y direction from its connection with the (m-1)-th bottom panel column 11R than the (m-1)-th bottom panel column 11R.

[0021] The bottom module 10 includes a flexible substrate 30 and a bypass diode 40. A flexible substrate 30 is provided for each bottom panel row 11R. The flexible substrates 30 are connected in parallel to the bottom panel row 11R to form a bypass line for the bottom panel row 11R. The flexible substrate 30 is connected to a negative terminal 13 and a positive terminal 14, which are the electrical ends of the bottom panel row 11R, via a bottom bus bar 20 and a panel row end connector 17. The flexible substrate 30 is disposed on the back side of the bottom solar cell panel 11 and overlaps the bottom solar cell panel 11 in a planar view. The flexible substrate 30 extends along the longitudinal direction (i.e., the X direction) of the bottom panel row 11R with a constant width in a planar view.

[0022] The flexible substrate 30 is disposed with both main surfaces facing in the thickness direction. The flexible substrate 30 includes wiring 31 and a substrate 32 supporting the wiring 31. For example, the wiring 31 is formed of copper foil or the like. The wiring 31 extends substantially the entire length of the flexible substrate 30. The substrate 32 is formed in a sheet shape from an insulating material such as polyimide. The substrate 32 exposes the wiring 31 to the front side at both ends of the flexible substrate 30. The wiring 31 is exposed from the substrate 32 to the front side at both ends of the flexible substrate 30. However, flying leads may be used near both ends of the flexible substrate 30, so that the wiring 31 is exposed to both the front and back sides of the substrate 32. The wiring 31 is connected to the back side of the bottom bus bar 20 at both ends of the flexible substrate 30.

[0023] The bypass diode 40 is mounted on the flexible substrate 30. The bypass diode 40 is connected to a midpoint of the wiring 31. The bypass diode 40 rectifies the wiring 31. The bypass diode 40 is connected to the back surface of the wiring 31 and protrudes from the flexible substrate 30 to the back side.

[0024] 4 is a plan view showing a top module according to an embodiment, in which the outline of a package 80 is shown by imaginary lines. As shown in FIG. 4, the top module 50 has multiple top solar cell panels 51 (second solar cell panels). All of the top solar cell panels 51 are arranged along a common XY plane. The number of top solar cell panels 51 is the same as the number of bottom solar cell panels 11. One solar cell 52 is formed in the top solar cell panel 51. However, the top solar cell panel 51 may have multiple solar cell cells connected in series and parallel. The solar cell 52 is a light-transmitting solar cell that uses a direct transition semiconductor for its light absorption layer. The solar cell 52 has a light absorption layer with a wider band gap than the light absorption layer of the solar cell 12 of the bottom module 10. The light absorption layer of the solar cell 52 contains cuprous oxide (CuO) as a direct transition semiconductor. The solar cell 52 has a configuration in which a p-electrode, a p-light absorption layer, an n-compound layer, and an n-electrode are stacked in this order on the front side of a glass substrate. The p-electrode is exposed on the front side at the end of the top solar cell panel 51 in the +Y direction. The n-electrode is exposed on the front side at the end of the top solar cell panel 51 in the -Y direction. The p-electrode and n-electrode function as terminals for extracting current on the front surface of the top solar cell panel 51. The top solar cell panel 51 is arranged with its light-receiving surface facing the front side. In other words, the normal direction of the light-receiving surface of the top solar cell panel 51 is along the thickness direction.

[0025] The top module 50 includes multiple top panel rows 51R each formed by a plurality of top solar cell panels 51 connected in parallel. In each top panel row 51R, the top solar cell panels 51 are aligned in the X direction at intervals. The overall outer shape of each top panel row 51R is formed into a rectangular shape with the X direction as the longitudinal direction in a plan view. The top panel rows 51R are connected in series to each other. The top panel rows 51R are aligned in the Y direction at intervals. As a result, the multiple top solar cell panels 51 are aligned in the X and Y directions. The overall outer shape of the aligned multiple top solar cell panels 51 is formed into a rectangular shape with the X direction as the longitudinal direction. The top solar cell panels 51 are arranged so that one top solar cell panel 51 overlaps each bottom solar cell panel 11. As a result, in the illustrated example, the top module 50 includes five top panel rows 51R each formed by four top solar cell panels 51.

[0026] FIG. 5 is a plan view showing the positional relationship between the bottom module and the top module of the embodiment. As shown in FIG. 5, each top solar cell panel 51 is arranged to face the light-receiving surface (front surface) of the bottom solar cell panel 11 of the bottom module 10. The top solar cell panels 51 are formed to be equal to or larger in size than the bottom solar cell panels 11. The top solar cell panels 51 entirely overlap the bottom solar cell panels 11 in a planar view. The solar cell cells 52 of the top solar cell panel 51 entirely overlap the solar cell cells 12 of the bottom solar cell panel 11 in a planar view. In other words, the entire solar cell 12 of the bottom solar cell panel 11 is arranged inside the outline of the solar cell cells 52 of the top solar cell panel 51 in a planar view.

[0027] As shown in FIG. 4, the top module 50 includes an interconnector 60 and a top bus bar 70. For example, the interconnector 60 is formed of copper wire, copper plate, copper foil, or conductive tape having solder plating layers on both main surfaces. A pair of interconnectors 60 is provided for each top panel row 51R. The interconnector 60 includes a first interconnector 61 electrically connected to the p-electrode of the top solar cell panel 51 and a second interconnector 62 electrically connected to the n-electrode of the top solar cell panel 51, for each top panel row 51R. Each interconnector 60 has a constant width in a plan view and extends along the alignment direction of the top solar cell panels 51 in the top panel row 51R (i.e., the X direction). The first interconnector 61 is joined to the surface of the end of the top solar cell panel 51 in the +Y direction of each top panel row 51R. The first interconnector 61 commonly connects the p-electrodes of the top solar cell panels 51 in each top panel row 51R. The second interconnector 62 is joined to the surface of the end portion in the -Y direction of the top solar cell panel 51 of each top panel row 51R. The second interconnector 62 commonly connects the n-electrodes of the top solar cell panels 51 of each top panel row 51R. It is desirable that the interconnector 60 is arranged so as not to overlap the solar cell cells 12 of the bottom solar cell panel 11 in a plan view.

[0028] The interconnectors 60 extend further in the +X direction or the -X direction than the top panel columns 51R. The first interconnectors 61 joined to odd-numbered top panel columns 51R extend further in the -X direction than the top panel columns 51R. The first interconnectors 61 joined to even-numbered top panel columns 51R extend further in the +X direction than the top panel columns 51R. The second interconnectors 62 joined to odd-numbered top panel columns 51R extend further in the +X direction than the top panel columns 51R. The second interconnectors 62 joined to even-numbered top panel columns 51R extend further in the -X direction than the top panel columns 51R. The interconnectors 60 are connected to the top bus bars 70 at locations that protrude in the X direction than the top panel columns 51R.

[0029] The top bus bar 70 is arranged on both sides of the top panel row 51R in the +X direction and the -X direction in a plan view. The top bus bar 70 is arranged around the entire periphery of the multiple top solar cell panels 51 in a plan view. In this embodiment, the entire periphery of the multiple top solar cell panels 51 means the periphery of the multiple top solar cell panels 51 when the multiple top solar cell panels 51 are considered as a single rectangular panel. The top bus bar 70 is arranged at the same position in the X direction as the bottom bus bar 20. The top bus bar 70 is formed of a metal plate. For example, the top bus bar 70 is formed of the same material as the bottom bus bar 20. The top bus bar 70 extends along the Y direction. The top bus bars 70 are arranged so as not to contact each other. The top bus bar 70 includes an inter-panel bus bar 71 and a terminal bus bar 72.

[0030] The inter-panel bus bars 71 connect adjacent top panel columns 51R in series via the interconnectors 60. The inter-panel bus bars 71 are arranged on both sides of the top panel column 51R in the +X direction and the -X direction in a plan view. When m is an odd number, the +X direction inter-panel bus bar 71 is connected to the +X direction end of the second interconnector 62 connected to the m-th top panel column 51R and the +X direction end of the first interconnector 61 connected to the (m+1)-th top panel column 51R. When n is an even number, the -X direction inter-panel bus bar 71 is connected to the -X direction end of the second interconnector 62 connected to the n-th top panel column 51R and the -X direction end of the first interconnector 61 connected to the (n+1)-th top panel column 51R.

[0031] When the series-parallel connected top solar cell panels 51 are considered as one solar cell, the terminal bus bars 72 are connected via the interconnector 60 to the p-electrode and n-electrode, which are the electrical ends of one solar cell. The terminal bus bars 72 are arranged on both the +X and -X directions of the top panel row 51R in a plan view. The -X direction terminal bus bar 72 is connected to the -X direction end of the first interconnector 61 connected to the first top panel row 51R. The -X direction terminal bus bar 72 extends in the +Y direction from the connection with the first interconnector 61 and is drawn out to the outside of the package 80. When the number of top panel rows 51R is N, the +X direction terminal bus bar 72 is connected to the +X direction end of the second interconnector 62 connected to the Nth top panel row 51R. The +X direction terminal bus bar 72 extends in the -Y direction from the connection with the second interconnector 62 and is drawn out to the outside of the package 80.

[0032] Although not shown, a bypass diode may be connected in parallel to each top solar cell panel 51. For example, one bypass diode may be provided for each top panel row 51R. In this case, the bypass diode may be connected to the first interconnector 61 and the second interconnector 62 at a position in the +X direction or the −X direction of the top panel row 51R.

[0033] As shown in Fig. 1, the package 80 houses the bottom module 10 with the terminal bus bar 22 of the bottom bus bar 20 pulled out, and houses the top module 50 with the top bus bar 70 pulled out. The package 80 includes a front cover 81 (first protective material) and a back cover 82 (second protective material). The front cover 81 is disposed on the front side of the bottom module 10 and the top module 50. The back cover 82 is disposed on the back side of the bottom module 10 and the top module 50.

[0034] The front cover 81 is a light-transmitting single-layer film made of a fluorine-based resin. Examples of fluorine-based resins include tetrafluoroethylene-ethylene copolymer (ETFE) and chlorotrifluoroethylene-ethylene copolymer (ECTFE). The front cover 81 is formed in a rectangular shape with one pair of sides extending in the X direction and the other pair of sides extending in the Y direction in a planar view. The front cover 81 is arranged so as to overlap, in a planar view, the entire bottom module 10 except for the tips of the terminal bus bars 22 and the entire top module 50 except for the tips of each top bus bar 70. Hereinafter, the portions of the bottom module 10 and the top module 50 that are overlapped by the front cover 81 in a planar view are referred to as "main portions." The front surface of the front cover 81 forms the light incident surface of the tandem solar cell 1.

[0035] The back cover 82 is a light-transmitting single-layer film made of a fluorine-based resin, similar to the front cover 81. The back cover 82 is formed to have the same shape and size as the front cover 81 in a plan view. The back cover 82 is disposed so as to completely overlap the front cover 81 in a plan view.

[0036] As shown in FIG. 2, the package 80 includes a sealing material 83. The sealing material 83 is disposed between a front cover 81 and a back cover 82. The sealing material 83 is made of a resin material that is light-transmitting and insulating. The sealing material 83 is formed by laminating a plurality of insulating films 90 between the front cover 81 and the back cover 82 and integrating them with each other by heat treatment. Each insulating film 90 is a single-layer film containing at least one of an ethylene vinyl acetate copolymer, a polyolefin resin, and an ionomer resin.

[0037] FIG. 6 is a cross-sectional view of the tandem solar cell taken along line VI-VI in FIG. 2 and 6, the multiple insulating films 90 include a first insulating film 91 (first sealing material) disposed between the top module 50 and the front cover 81, a second insulating film 92 (second sealing material) disposed between the bottom module 10 and the top module 50, and a third insulating film 93 (third sealing material) disposed between the bottom module 10 and the back cover 82. As a result, the bottom module 10 and the top module 50 are disposed between the insulating film 90 layers. A flexible substrate 30 is embedded in the third insulating film 93. Like the front cover 81 and the back cover 82, each insulating film 90 overlaps the entire main portion of each of the bottom module 10 and the top module 50 in a planar view. Furthermore, the insulating films 90 overlap each other on the outer sides of the bottom module 10 and the top module 50 in a planar view.

[0038] As shown in FIG. 6 , the encapsulant 83 includes a first encapsulating layer 84, a second encapsulating layer 85, and a third encapsulating layer 86. The first encapsulating layer 84 is laminated on the top solar cell panel 51 from the side opposite the bottom solar cell panel 11 so as to be in direct contact with the top solar cell panel 51. The first encapsulating layer 84 is a portion of the first insulating film 91 that overlaps with the top solar cell panel 51 in a planar view. The second encapsulating layer 85 is disposed between the bottom solar cell panel 11 and the top solar cell panel 51. The second encapsulating layer 85 is a portion of the second insulating film 92 that overlaps with the bottom solar cell panel 11 and the top solar cell panel 51 in a planar view. As a result, only the second encapsulating layer 85 is disposed between the bottom solar cell panel 11 and the top solar cell panel 51. The third encapsulating layer 86 is laminated on the bottom solar cell panel 11 from the side opposite the second encapsulating layer 85 so as to be in direct contact with the bottom solar cell panel 11. The third sealing layer 86 is a portion of the third insulating film 93 that overlaps with the bottom solar cell panel 11 in a plan view.

[0039] The thickness of each component of the tandem solar cell 1 will be described with reference to FIG. The thickness of the front cover 81 is 25 μm or more and 200 μm or less, preferably 50 μm or more and 150 μm or less, and more preferably 50 μm or more and 100 μm or less. The thickness of the first encapsulating layer 84 is 50 μm or more and 400 μm or less, preferably 50 μm or more and 200 μm or less, and more preferably 100 μm or more and 200 μm or less. The thickness of the top solar cell panel 51 is 30 μm or more and 150 μm or less, and preferably 35 μm or more and 80 μm or less. For example, the thickness of the top solar cell panel 51 is the thickness of a glass substrate. The thickness of the second encapsulating layer 85 is 30 μm or more and 400 μm or less, preferably 35 μm or more and 200 μm or less, and more preferably 100 μm or more and 200 μm or less. The thickness of the bottom solar cell panel 11 is 100 μm or more and 150 μm or less. For example, the thickness of the bottom solar cell panel 11 is the thickness of a silicon wafer (silicon substrate). The thickness of the third encapsulating layer 86 is 50 μm to 400 μm, preferably 50 μm to 200 μm, and more preferably 100 μm to 200 μm. If a flexible substrate 30 is embedded in the third encapsulating layer 86, the thickness of the third encapsulating layer 86 includes the thickness of the flexible substrate 30. The thickness of the back cover 82 is 25 μm to 200 μm, preferably 50 μm to 150 μm, and more preferably 50 μm to 100 μm. Furthermore, the thickness of the tandem solar cell 1 is 375 μm to 1290 μm in plan view at the point where the bottom solar cell panel 11 and the top solar cell panel 51 overlap. For example, the thickness of each part of the tandem solar cell 1 is measured using a cross-sectional SEM or the like.

[0040] A method for manufacturing the tandem solar cell 1 will now be described. In this embodiment, the tandem solar cell 1 is formed by heating and integrating the laminate 2, which is made by laminating the above-mentioned front cover 81, back cover 82, bottom module 10, top module 50, and insulating film 90. The manufacturing method of this embodiment includes a preheating step, a lamination step, and a heating step.

[0041] First, a preheating step is performed. In the preheating step, at least one of the first insulating film 91, the second insulating film 92, and the third insulating film 93 is heated alone to shrink the insulating film in advance. In the preheating step, it is desirable to place a fluororesin sheet between the insulating film to be heated and the heating body to prevent the insulating film from welding to the heating body. Note that the preheating step may not be performed depending on the thickness, material, etc. of the protective material or insulating film. Specifically, in the heating step described below, if the thickness of the protective material on the heating surface side of the first protective material and the second protective material exceeds 100 μm (preferably 150 μm or more) and if the thickness of the insulating film exceeds 100 μm, the preheating step may not be performed.

[0042] Next, a lamination process is performed. In the lamination process, a laminate 2 is formed by laminating the front cover 81, first insulating film 91, top module 50, second insulating film 92, bottom module 10, third insulating film 93, and back cover 82 in this order. The top module 50 is positioned so that the top solar cell panel 51 faces the light-receiving surface of the bottom solar cell panel 11. The first insulating film 91 is overlaid on the top module 50 from the side opposite the bottom module 10. A second insulating film 92 is overlaid on the bottom module 10 and top module 50 between the bottom solar cell panel 11 and the top solar cell panel 51. A third insulating film 93 is overlaid on the bottom module 10 from the side opposite the second insulating film 92. A back cover 82 is overlaid on the third insulating film 93 from the side opposite the bottom module 10. A front cover 81 is overlaid on the first insulating film 91 from the side opposite the top module 50. The laminate 2 is thus formed. The order in which the component overlaying processes are performed is not particularly limited, as long as the laminate 2 is formed by laminating the components in the above-described order. For example, the laminate 2 is formed by stacking the front cover 81, the first insulating film 91, the top module 50, the second insulating film 92, the bottom module 10, the third insulating film 93, and the back cover 82 in this order.

[0043] Here, the insulating films 90 overlap each other on the outside of the bottom module 10 and the top module 50 in a plan view. As a result, the first insulating film 91 and the second insulating film 92 directly overlap each other on the outside of the top module 50. In addition, the second insulating film 92 and the third insulating film 93 overlap each other on the outside of the bottom module 10.

[0044] The thickness of each insulating film 90 is 50 μm or more and 400 μm or less, preferably 50 μm or more and 200 μm or less, and more preferably 100 μm or more and 200 μm or less. If a preheating step is performed, the thickness of each insulating film 90 is the thickness before the preheating step. The thicknesses of the front cover 81, the back cover 82, the bottom solar cell panel 11, and the top solar cell panel 51 are the same as the respective thicknesses of the finished tandem solar cell 1.

[0045] Next, a heating step is performed. In the heating step, the laminate 2 is heated to melt the insulating film 90. The melted insulating film 90 is bonded to the components overlapping the insulating film 90. This bonds the bottom module 10, the top module 50, the front cover 81, the back cover 82, the first insulating film 91, the second insulating film 92, and the third insulating film 93 to one another. The first insulating film 91 and the second insulating film 92 are welded and integrated to one another on the outer side of the top module 50 in a planar view. The second insulating film 92 and the third insulating film 93 are welded and integrated to one another on the outer side of the bottom module 10 in a planar view. As a result, the first insulating film 91, the second insulating film 92, and the third insulating film 93 are integrated to have continuity, forming the sealing material 83.

[0046] FIG. 7 is a diagram illustrating an example of a heating step according to an embodiment. As shown in FIG. 7 , in the heating step, the laminate 2 is heated by bringing a high-temperature heating device 100 into direct contact with the laminate 2. The heating device 100 includes a glass body 101 that is in direct contact with the laminate 2, and a heater 102 that heats the glass body 101. The glass body 101 is made of silicate glass. The glass body 101 is, for example, a glass plate. The glass body 101 has a flat heating surface 103 that is in contact with the front cover 81 or the back cover 82 (the back cover 82 in the illustrated example) of the laminate 2, and a flat heated surface 104 facing the opposite side to the heating surface 103. The heating surface 103 is formed to a size that contacts the entire surface of the front cover 81 or the back cover 82. The heater 102 is made of metal. The heater 102 is in contact with the heated surface 104 of the glass body 101. It is desirable that the heater 102 contacts at least the entire area of ​​the heated surface 104 that coincides with the contact portion between the heated surface 103 and the laminate 2, when viewed from the normal direction of the heated surface 103. For example, the heater 102 contacts the entire heated surface 104.

[0047] In the heating step, the laminate 2 may be sandwiched between the glass body 101 and the pressing member 105 from both sides in the thickness direction. It is desirable that the pressing member 105 contacts the entire surface of the front cover 81 or the back cover 82 (front cover 81 in the illustrated example). For example, the pressing member 105 presses the laminate 2 by its own weight. However, an external force pressing the laminate 2 may also be applied to the pressing member 105. Furthermore, in addition to heating the laminate 2 by the heating device 100, the laminate 2 may also be heated by the high-temperature pressing member 105. In this case, the pressing member 105 may be formed by a glass body and a heater, similar to the heating device 100.

[0048] This completes the formation of the tandem solar cell 1. Furthermore, by carrying out the heating step of this embodiment, the insulating film 90 melts, and the sealing layers 84, 85, and 86 having the above-mentioned thicknesses are formed.

[0049] As described above, the tandem solar cell 1 of this embodiment is formed by heating the first insulating film 91, the second insulating film 92, and the third insulating film 93 to bond the bottom module 10, the top module 50, the first insulating film 91, the second insulating film 92, the third insulating film 93, the front cover 81, and the back cover 82 together. The thickness of each insulating film 90 is set to 50 μm or more and 400 μm or less, the thickness of the front cover 81 is set to 25 μm or more and 200 μm or less, and the thickness of the back cover 82 is set to 25 μm or more and 200 μm or less. As a result, in the completed tandem solar cell 1, the first encapsulating layer 84 has a thickness of 50 μm or more and 400 μm or less, the second encapsulating layer 85 has a thickness of 30 μm or more and 400 μm or less, and the third encapsulating layer 86 has a thickness of 50 μm or more and 400 μm or less. It was confirmed that by keeping the thickness of each layer of the tandem solar cell 1 within the above range and setting the thickness of the area where the bottom solar cell panel 11 and the top solar cell panel 51 overlap in a plan view of the tandem solar cell 1 to 375 μm or more and 1290 μm or less, it is possible to form a tandem solar cell 1 with no wrinkles in the front cover 81 and no defects in the sealing layers 84, 85, and 86. This makes it possible to reduce the thickness of the tandem solar cell 1 while suppressing a decrease in power generation efficiency. As a result, a highly efficient and lightweight tandem solar cell 1 can be obtained.

[0050] In particular, when the thickness of second sealing layer 85 is 30 μm or more, second sealing layer 85 has a volume resistivity of 1.0×10 14 When a material having a resistance of 3.0×10 [Ω·cm] or more is used, the resistance in the thickness direction of second sealing layer 85 is 3.0×10 11 Therefore, by setting the thickness of second encapsulation layer 85 to 30 μm or more as in this embodiment, insulation between bottom solar cell panel 11 and top solar cell panel 51 can be ensured in a thinned tandem solar cell 1.

[0051] The thickness of the bottom solar cell panel 11 is set to 100 μm or more and 150 μm or less, and the thickness of the top solar cell panel 51 is set to 30 μm or more and 150 μm or less. This ensures both bending strength by thinning the solar cell panels 11 and 51 and strength against thermal stress during heating. Therefore, a thin tandem solar cell 1 with excellent practical strength is obtained.

[0052] The front cover 81 is a light-transmitting film containing a fluorine-based resin. This configuration makes it possible to seal the top solar cell panel 51 and the bottom solar cell panel 11 while suppressing attenuation of light incident on them and ensuring electrical insulation. In particular, because the front cover 81 of this embodiment is a single-layer film, it can be made lighter than a front cover made of a multilayer film. This allows the tandem solar cell 1 to be made lightweight.

[0053] The bottom solar cell panel 11 has an indirect transition semiconductor layer. The top solar cell panel 51 has a direct transition semiconductor layer. With this configuration, the absorption wavelength range of the bottom solar cell panel 11 can be made different from the absorption wavelength range of the top solar cell panel 51. Therefore, a solar cell with higher efficiency can be formed compared to a solar cell including a solar cell panel having a single type of semiconductor layer.

[0054] Furthermore, p-electrodes and n-electrodes are formed on the front side of the glass substrate of top solar cell panel 51. With this configuration, even if second sealing layer 85 between top solar cell panel 51 and bottom solar cell panel 11 is thin, the glass substrate ensures electrical insulation between top solar cell panel 51 and bottom solar cell panel 11. Therefore, by thinning second sealing layer 85, tandem solar cell 1 can be formed with a light weight.

[0055] If the thickness of the glass substrate of the top solar cell panel 51 is 30 μm or more, the volume resistivity of the glass substrate is 7.9×10 11 [Ω·cm] or more, the resistance in the thickness direction of the glass substrate is 2.0×109 [Ω] or more. Therefore, in a thinned tandem solar cell 1, insulation between the bottom solar cell panel 11 and the top solar cell panel 51 can be more reliably ensured.

[0056] The manufacturing method for the tandem solar cell 1 of this embodiment also includes a heating step of bringing the stack 2 formed by the bottom solar cell panel 11, the top solar cell panel 51, the first insulating film 91, the second insulating film 92, the third insulating film 93, the back cover 82, and the front cover 81 into contact with a heated glass body 101 and heating it. With this method, glass has a significantly lower thermal conductivity than metal materials, so rapid heat transfer to the stack 2 can be suppressed compared to a method in which the stack is heated by contacting it with a heated metal body. Therefore, the stack 2 can be heated evenly, and the occurrence of local defects in the tandem solar cell 1 can be suppressed.

[0057] The method for manufacturing the tandem solar cell 1 of this embodiment also includes a preheating step of heating at least one of the first insulating film 91, the second insulating film 92, and the third insulating film 93 alone. This method allows a preheated insulating film to be used in the heating step, thereby suppressing thermal shrinkage of the insulating film in the heating step and preventing defects such as wrinkles and chips from occurring in the sealing layers 84, 85, and 86. This is particularly effective when the insulating film is made of a thermoplastic resin or a material with a relatively large thermal shrinkage rate.

[0058] If the insulating film (third insulating film 93 in this embodiment) that is positioned closest to the heating device 100 during the heating process has a thickness of 100 μm or less, a defect with a thickness of about 30 μm or less, including a step or a cavity, may occur after the heating process. This may result in a decrease in the water vapor barrier property of the sealing layer, electrode corrosion, expansion of air in the defect due to changes in air pressure, etc. Furthermore, when the thickness of the protective material on the heated surface side in the heating process is greater than 100 μm (preferably 150 μm or more), the hardness of the protective material suppresses shrinkage of the insulating film, but when the thickness of the protective material is 100 μm or less, wrinkles are likely to occur in the insulating film. Therefore, when the thickness of the protective material or insulating film on the heated surface side in the heating process is 100 μm or less, performing a preheating process can effectively suppress the occurrence of the above-mentioned problems, so it is preferable to perform a preheating process.

[0059] A modification of the embodiment will be described with reference to Fig. 8. Fig. 8 is a development view of a device equipped with a tandem solar cell according to the modification of the embodiment. In the above embodiment, the sealing material 83 is laminated on the back cover 82. However, as in the tandem solar cell 1A shown in FIG. 8 , the sealing material 83 may be laminated on a part of the device 200 on which the tandem solar cell 1A is mounted, instead of on the back cover 82. In this case, the tandem solar cell 1A is fixed to the device 200 by adhesive or the like. For example, the sealing material 83 is laminated on the upper surface of the wing of an aircraft or the roof of a mobility vehicle. Even in this case, the thicknesses of the bottom solar cell panel 11, the top solar cell panel 51, the first sealing layer 84, the second sealing layer 85, the third sealing layer 86, and the front cover 81 are the same as in the above embodiment. Furthermore, the thickness of the tandem solar cell 1A is 350 μm or more and 1140 μm or less at the overlapping portion of the bottom solar cell panel 11 and the top solar cell panel 51 in a plan view. This allows the tandem solar cell 1A to achieve the same effects as the tandem solar cell 1 of the embodiment.

[0060] The tandem solar cell 1A of this modification can be formed by the same manufacturing method as the tandem solar cell 1 of the embodiment. In this case, in the heating step, it is desirable to bring the heating device 100 into contact with the front cover 81 of the laminate formed by stacking the front cover 81, the bottom module 10, the top module 50, and the insulating film 90.

[0061] In the above embodiment, the front cover 81 is a single-layer film made of a fluorine-based resin, but this configuration is not limited thereto. The front cover may also be a single-layer film made of weather-resistant polyethylene terephthalate. The front cover may also have a structure in which a primer, a top coat, or the like is applied to any of the above-mentioned single-layer films. The front cover may also be a multilayer film containing at least one of a fluorine-based resin and weather-resistant polyethylene terephthalate. For example, the multilayer film may be a film formed by bonding a fluorine-based resin film on the light incident side to a weather-resistant polyethylene terephthalate film on the sealing material side. In either of the above configurations, as long as the front cover is a translucent film containing at least one of a fluorine-based resin and weather-resistant polyethylene terephthalate, it can seal the top solar cell panel 51 and the bottom solar cell panel 11 while ensuring electrical insulation and suppressing attenuation of light incident on the top solar cell panel 51 and the bottom solar cell panel 11. However, the front cover may also be made of a transparent resin material other than the above-mentioned materials, glass, or the like. The same applies to the back cover.

[0062] In the above embodiment, all bottom solar panels 11 are connected in series, but this configuration is not limiting. Multiple bottom solar panels may be connected in parallel or in a combination of series and parallel. Also, a single bottom solar panel may be provided in the bottom module.

[0063] In the above embodiment, the multiple top solar cell panels 51 are connected to each other in a combination of parallel and series, but this configuration is not limiting. The multiple top solar cell panels may be connected to each other in series or parallel. Also, a single top solar cell panel may be provided in the top module.

[0064] In the above embodiment, the tandem solar cell 1 is a four-terminal solar cell, but is not limited to this configuration. The tandem solar cell may also be a two-terminal solar cell in which the bottom module and the top module are connected in series. The positions of the positive and negative terminals in the tandem solar cell are not particularly limited.

[0065] Furthermore, in the above embodiment, the flexible substrate 30 of the bottom module 10 is disposed on the back side of the bottom solar cell panel 11, but this configuration is not limiting. For example, the flexible substrate may be disposed around the bottom panel row 11R so as not to overlap the bottom solar cell panel 11. For example, the flexible substrate may be disposed along the bottom panel row 11R at a position offset in the Y direction from the bottom panel row 11R connected in parallel to the flexible substrate.

[0066] In the above embodiment, the solar cells 12 of the bottom solar cell panel 11 are back-contact solar cells having an n-type electrode and a p-type electrode on the back side, but the present invention is not limited to this configuration. For example, the solar cells of the bottom solar cell panel may have a structure in which an n-electrode is on the front side and a p-electrode is on the back side. In this case, the interconnector connecting the pair of bottom solar cell panels may be a wire-like member that connects the p-electrode on the back side of one bottom solar cell panel to the n-electrode on the front side of the other bottom solar cell panel.

[0067] According to at least one of the embodiments described above, by setting the thickness at the overlapping portion of the bottom solar cell panel and the top solar cell panel to 350 μm or more and 1140 μm or less in the thickness direction, a tandem solar cell can be formed in which the front cover is free of wrinkles and the sealing layer is free of defects. This makes it possible to reduce the thickness of the tandem solar cell while suppressing a decrease in power generation efficiency. As a result, a highly efficient and lightweight tandem solar cell can be obtained.

[0068] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as set forth in the claims.

Claims

1. a first solar panel; a second light-transmitting solar cell panel disposed opposite the light-receiving surface of the first solar cell panel; a first sealing layer having a thickness of 50 μm or more and 400 μm or less, laminated on the second solar cell panel from the side opposite to the first solar cell panel; a second encapsulation layer having a thickness of 30 μm or more and 400 μm or less, which is disposed between the first solar cell panel and the second solar cell panel and laminated so as to be in direct contact with the first solar cell panel and the second solar cell panel; a third encapsulating layer having a thickness of 50 μm or more and 400 μm or less, laminated on the first solar cell panel from the side opposite to the second encapsulating layer; a first protective material having a thickness of 25 μm or more and 200 μm or less, laminated on the first encapsulating layer from the side opposite to the second solar cell panel; Equipped with the first sealing layer, the second sealing layer, and the third sealing layer are films formed of at least one material selected from the group consisting of an ethylene-vinyl acetate copolymer, a polyolefin-based resin, and an ionomer-based resin; the first protective material is a light-transmitting single-layer film made of a fluorine-based resin or weather-resistant polyethylene terephthalate, or a light-transmitting multi-layer film formed by bonding a film made of the fluorine-based resin and a film made of the weather-resistant polyethylene terephthalate, A solar cell having a thickness of 350 μm or more and 1140 μm or less at a location where the first solar cell panel and the second solar cell panel overlap when viewed from the normal direction of the light receiving surface of the first solar cell panel.

2. The solar cell according to claim 1 , a second protective material having a thickness of 25 μm or more and 200 μm or less, laminated on the third sealing layer from the side opposite to the first protective material; the second protective material is a light-transmitting single-layer film formed from the fluorine-based resin or the weather-resistant polyethylene terephthalate, or a light-transmitting multilayer film formed by bonding a film formed from the fluorine-based resin and a film formed from the weather-resistant polyethylene terephthalate, A solar cell having a thickness of 375 μm or more and 1290 μm or less at a location where the first solar cell panel and the second solar cell panel overlap when viewed from the normal direction of the light receiving surface of the first solar cell panel.

3. The solar cell according to claim 1 or 2, The thickness of the first solar cell panel is 100 μm or more and 150 μm or less, The thickness of the second solar cell panel is 30 μm or more and 150 μm or less. Solar cell.

4. The solar cell according to claim 1 or 2, The first protective material is a single-layer film. Solar cell.

5. The solar cell according to claim 1 or 2, The first protective material is a multilayer film. Solar cell.

6. The solar cell according to claim 1 or 2, the first solar cell panel has an indirect transition semiconductor layer, the second solar cell panel has a direct transition semiconductor layer; Solar cell.

7. a second light-transmitting solar cell panel is disposed so as to face the light-receiving surface of the first solar cell panel; a first sealing material selected from the group consisting of ethylene vinyl acetate copolymer, polyolefin resin, and ionomer resin, having a thickness of 50 μm or more and 400 μm or less, is superimposed on the second solar cell panel from the side opposite to the first solar cell panel; a second sealing material selected from the group consisting of the ethylene vinyl acetate copolymer, the polyolefin resin, and the ionomer resin, having a thickness of 50 μm or more and 400 μm or less, is overlaid on the first solar cell panel and the second solar cell panel between the first solar cell panel and the second solar cell panel; a third sealing material selected from the group consisting of the ethylene vinyl acetate copolymer, the polyolefin resin, and the ionomer resin, the third sealing material having a thickness of 50 μm or more and 400 μm or less, is superimposed on the first solar cell panel from the opposite side to the second sealing material; a first protective material having a thickness of 25 μm or more and 200 μm or less, the first protective material being a light-transmitting monolayer film formed from a fluorine-based resin or weather-resistant polyethylene terephthalate, or a light-transmitting multilayer film formed by bonding a film formed from the fluorine-based resin and a film formed from the weather-resistant polyethylene terephthalate, and the first protective material being superimposed on the first sealing material from the side opposite to the second solar cell panel; heating the first sealing material, the second sealing material, and the third sealing material to bond the first solar cell panel, the second solar cell panel, the first sealing material, the second sealing material, the third sealing material, and the first protective material to one another, and setting the thickness of the overlapping portion of the first solar cell panel and the second solar cell panel to 350 μm or more and 1140 μm or less when viewed from the normal direction of the light-receiving surface of the first solar cell panel; How solar cells are manufactured.

8. The method for manufacturing a solar cell according to claim 7, a heating step of contacting a stack of the first solar cell panel, the second solar cell panel, the first sealing material, the second sealing material, the third sealing material, and the first protective material with a heated glass body and heating the stack. How solar cells are manufactured.

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