Solar battery

Abstract

To provide a perovskite tandem solar battery having high photoelectric conversion efficiency without deteriorating the industrial productivity.SOLUTION: A solar battery 100 includes a first cell 101 in which a first electrode layer 2, a first electron transport layer 3, a first photoelectric conversion layer 4, a first hole transport layer 5, and a second electrode layer 6 are stacked in this order on a first substrate 1, and a second cell 102 in which a fourth electrode layer 11, a second hole transport layer 10, a second photoelectric conversion layer 9, a second electron transport layer 8, and a third electrode layer 7 are stacked in this order on a second substrate 12. The first substrate 1, the first electrode layer 2, the second electrode layer 6, and the third electrode layer 7 have light-transmitting properties. The first cell 101 and the second cell 102 are disposed so that light enters from the first substrate 1 side and the second electrode layer 6 and the third electrode layer 7 face each other and are apart from each other. A first perovskite compound included in the first photoelectric conversion layer 4 has a larger band gap than a second perovskite compound included in the second photoelectric conversion layer 9.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, research and development of perovskite solar cells has been progressing as a new solar cell to replace existing silicon-based solar cells.

[0003] In perovskite solar cells, a perovskite compound represented by the chemical formula ABX3 (where A is a monovalent cation, B is a divalent cation, and X is a halogen anion) is used as the photoelectric conversion material.

[0004] Non-Patent Document 1 discloses a perovskite solar cell that uses a perovskite compound represented by the chemical formula CH3NH3PbI3 (hereinafter referred to as "MAPbI3") as the photoelectric conversion material of the perovskite solar cell. In the perovskite solar cell disclosed in Non-Patent Document 1, the perovskite compound represented by MAPbI3, TiO2, and Spiro-OMeTAD are used as the photoelectric conversion material, electron transport material, and hole transport material, respectively.

[0005] Non-Patent Document 2 discloses a perovskite tandem solar cell. The perovskite tandem solar cell has a configuration in which a plurality of solar cells using perovskite compounds with different band gaps are stacked one on top of the other. The perovskite tandem solar cell can improve photoelectric conversion efficiency. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Julian Burschka et al., "Sequential deposition as a route to high-performance perovskite-sensitized solar cells", Nature, vol.499, pp.316-319, 18 July 2013 [DOI:10.1038 / nature12340] [Non-patent document 2] "Monolithic all-perovskite tandem solar cells with 24.8% efficiency exploiting comproportionation to suppress Sn(ii) oxidation in precursor ink", Nature Energy, vol.4, pp.864-873, 2019 [DOI: https: / / doi.org / 10.1038 / s41560-019-0466-3] Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present disclosure is to provide a perovskite tandem solar cell having high photoelectric conversion efficiency without impairing industrial productivity. [Means for solving the problem]

[0008] The solar cell according to the present disclosure comprises: a first cell in which a first electrode layer, a first electron transport layer, a first photoelectric conversion layer, a first hole transport layer, and a second electrode layer are stacked in this order on a first substrate; a second cell in which a fourth electrode layer, a second hole transport layer, a second photoelectric conversion layer, a second electron transport layer, and a third electrode layer are stacked in this order on a second substrate; Equipped with the first substrate, the first electrode layer, the second electrode layer, and the third electrode layer are light-transmitting; the first cell and the second cell are arranged so that light is incident from the first substrate side, and so that the second electrode layer and the third electrode layer face each other and are spaced apart from each other; the first photoelectric conversion layer contains a first perovskite compound; the second photoelectric conversion layer contains a second perovskite compound, The band gap of the first perovskite compound is larger than the band gap of the second perovskite compound. [Effects of the Invention]

[0009] The present disclosure provides a perovskite tandem solar cell with high photoelectric conversion efficiency without compromising industrial productivity. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1A is a cross-sectional view schematically illustrating an example of a typical perovskite tandem solar cell having two terminals. [Figure 1B] FIG. 1B is a cross-sectional view that schematically illustrates a variation of a typical perovskite tandem solar cell having two terminals. [Figure 2] FIG. 2 is a perspective view of the perovskite tandem solar cell according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the perovskite tandem solar cell shown in FIG. 2 taken along line AA. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a perovskite tandem solar cell according to the second embodiment. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a perovskite tandem solar cell according to the third embodiment. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a perovskite tandem solar cell according to the fourth embodiment. [Figure 7] FIG. 7 is a cross-sectional view schematically showing an example of a solar cell module including a perovskite tandem solar cell according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Terminology> As used herein, the term "perovskite compound" refers to a perovskite crystal structure represented by the chemical formula ABX3 (where A is a monovalent cation, B is a divalent cation, and X is a halogen anion) and structures having crystals similar thereto.

[0012] As used herein, the term "lead-based perovskite compound" refers to a perovskite compound that contains Pb cations as divalent cations.

[0013] As used herein, the term "mixed tin-lead perovskite compound" refers to a perovskite compound that contains both Sn and Pb cations as divalent cations.

[0014] As used herein, the term "perovskite solar cell" refers to a solar cell that contains a perovskite compound as a photoelectric conversion material.

[0015] As used herein, the term "lead-based perovskite solar cell" refers to a solar cell that contains a lead-based perovskite compound as a photoelectric conversion material.

[0016] The term "perovskite tandem solar cell" used in this specification refers to a stacked solar cell having a configuration in which multiple solar cells using perovskite compounds with different band gaps are stacked on top of each other.

[0017] <Knowledge that forms the basis of this disclosure> The findings that form the basis of this disclosure will be explained below.

[0018] A perovskite tandem solar cell has a stacked structure consisting of a top cell arranged on the light-incident side and a bottom cell arranged on the opposite side to the light-incident side. The top cell is typically a perovskite solar cell containing a perovskite compound with a large band gap as a photoelectric conversion material. The bottom cell is typically a perovskite solar cell containing a perovskite compound with a band gap smaller than that of the perovskite compound in the top cell as a photoelectric conversion material. This structure enables perovskite tandem solar cells to effectively utilize light over a wide range and improve conversion efficiency.

[0019] Here, a lead-based perovskite compound is generally used as the photoelectric conversion material for the top cell. In the case of solar cells using a lead-based perovskite compound as the photoelectric conversion material, it has been reported that solar cells with a "nip structure" have high photoelectric conversion efficiency. The "nip structure" is a structure in which, from the substrate side, an electron transport layer, a photoelectric conversion layer, and a hole transport layer are arranged in this order. On the other hand, a tin-lead mixed perovskite compound is generally used as the photoelectric conversion material for the bottom cell. In the case of solar cells using a tin-lead mixed perovskite compound, it has been reported that solar cells with a "pin structure" have high photoelectric conversion efficiency. The "pin structure" is a structure in which, from the substrate side, a hole transport layer, a photoelectric conversion layer, and an electron transport layer are arranged in this order.

[0020] The reason for the relationship between the type of perovskite compound used as the photoelectric conversion material and the structure that provides high photoelectric conversion efficiency is unclear, but one possible reason is that usable N-type materials are limited.

[0021] In the case of the nip structure, the N-type material is placed on the substrate side. Therefore, in the case of the nip structure, there are no process constraints such as temperature during manufacturing, but an N-type material that will not dissolve even if a perovskite compound is layered on top is required. For this reason, metal oxides are generally used. Metal oxide-based N-type materials are said to be compatible with lead-based perovskite compounds. Therefore, solar cells that use lead-based perovskite compounds are thought to achieve high photoelectric conversion efficiency when they have an nip structure that generally uses metal oxide-based N-type materials.

[0022] On the other hand, in the case of a pin structure, an N-type material is placed on top of the perovskite compound. For this reason, a pin structure requires an N-type material that can be manufactured using a process that does not damage the perovskite compound. For this reason, fullerene-based materials are generally used. Fullerene-based N-type materials are said to be compatible with tin-lead mixed perovskite compounds. Therefore, solar cells that use tin-lead mixed perovskite compounds are thought to achieve high photoelectric conversion efficiency when they have a pin structure that generally uses fullerene-based N-type materials.

[0023] However, in perovskite tandem solar cells, it is difficult to stack the top and bottom cells together when combining a top cell with an nip structure and a bottom cell with a pin structure. In a typical perovskite tandem solar cell, the top and bottom cells are joined together by a recombination layer that recombines electrons and holes. In this case, the top and bottom cells are required to have the same structure, i.e., a pin structure or an nip structure. In other words, the perovskite tandem solar cell is required to have the configuration shown in Figures 1A and 1B below, for example.

[0024] FIG. 1A is a cross-sectional view schematically illustrating an example of a typical perovskite tandem solar cell having two terminals. FIG. 1B is a cross-sectional view schematically illustrating a modified example of a typical perovskite tandem solar cell having two terminals. Hereinafter, a structure having two terminals will be referred to as a "two-terminal structure." The perovskite tandem solar cell 1000 shown in FIG. 1A includes a top cell 1001 having a pin structure and a bottom cell 1002 having a pin structure. Specifically, the perovskite tandem solar cell 1000 having a two-terminal structure includes a bottom cell 1002, a recombination layer 1004, and a top cell 1001 provided in this order on a substrate 1003. The top cell 1001 has, in order from the light incident surface, i.e., from the top of FIG. 1A, a first electrode layer 10011, a first electron transport layer 10012, a first photoelectric conversion layer 10013, a first hole transport layer 10014, and a second electrode layer 10015. The bottom cell 1002 has, in order from the light incident surface, i.e., from the top of FIG. 1A, a third electrode layer 10021, a second electron transport layer 10022, a second photoelectric conversion layer 10023, a second hole transport layer 10024, and a fourth electrode layer 10025. The perovskite tandem solar cell 2000 shown in FIG. 1B comprises a top cell 2001 having a nip structure and a bottom cell 2002 having a nip structure. Specifically, perovskite tandem solar cell 2000 includes a bottom cell 2002, a recombination layer 2004, and a top cell 2001 provided in this order on a substrate 2003. Top cell 2001 includes, in order from the light incident surface, i.e., from the top of FIG. 1B, a first electrode layer 20011, a first hole transport layer 20012, a first photoelectric conversion layer 20013, a first electron transport layer 20014, and a second electrode layer 20015. Bottom cell 2002 includes, in order from the light incident surface, i.e., from the top of FIG. 1B, a third electrode layer 20021, a second hole transport layer 20022, a second photoelectric conversion layer 20023, a second hole transport layer 20024, and a fourth electrode layer 20025.

[0025] Therefore, through extensive research, the present inventors have discovered a structure for a perovskite tandem solar cell that allows the top cell and bottom cell to have a structure that can achieve high photoelectric conversion efficiency.

[0026] <Embodiments of the present disclosure> Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0027] (First embodiment) Fig. 2 is a perspective view of the perovskite tandem solar cell according to the first embodiment, and Fig. 3 is a cross-sectional view of the perovskite tandem solar cell shown in Fig. 2 taken along line AA.

[0028] As shown in FIGS. 2 and 3, the solar cell 100 according to the first embodiment has a top cell 10 and a bottom cell 102.

[0029] The top cell 101 has a first substrate 1, a first electrode layer 2, a first electron transport layer 3, a first photoelectric conversion layer 4, a first hole transport layer 5, and a second electrode layer 6. In the top cell 101, the first substrate 1, the first electrode layer 2, the first electron transport layer 3, the first photoelectric conversion layer 4, the first hole transport layer 5, and the second electrode layer 6 are provided in this order from the light incident surface, i.e., from the top of Figure 3.

[0030] As shown in FIG. 3 , in the top cell 101, for example, of the first substrate 1, first electrode layer 2, first electron transport layer 3, first photoelectric conversion layer 4, first hole transport layer 5, and second electrode layer 6 arranged in this order from the light incident surface, two adjacent layers are provided in contact with each other. In other words, the first substrate 1 and the first electrode layer 2 may be provided in contact with each other. The first electrode layer 2 and the first electron transport layer 3 may be provided in contact with each other. The first electron transport layer 3 and the first photoelectric conversion layer 4 may be provided in contact with each other. The first photoelectric conversion layer 4 and the first hole transport layer 5 may be provided in contact with each other. The first hole transport layer 5 and the second electrode layer 6 may be provided in contact with each other.

[0031] Note that, for example, other layers may be provided between the various layers constituting the top cell 101 as appropriate to suppress recombination at the interfaces between the various layers or to bond the various layers together. The other layers will be explained in the section (other layers) below.

[0032] The bottom cell 102 has a third electrode layer 7, a second electron transport layer 8, a second photoelectric conversion layer 9, a second hole transport layer 10, a fourth electrode layer 11, and a second substrate 12. In the bottom cell 102, the third electrode layer 7, the second electron transport layer 8, the second photoelectric conversion layer 9, the second hole transport layer 10, the fourth electrode layer 11, and the second substrate 12 are provided in this order from the light incident surface, i.e., from the top of FIG.

[0033] As shown in FIG. 3 , in the bottom cell 102, for example, in the third electrode layer 7, second electron transport layer 8, second photoelectric conversion layer 9, second hole transport layer 10, fourth electrode layer 11, and second substrate 12 arranged in this order from the light incident surface, two adjacent layers are provided in contact with each other. In other words, the third electrode layer 7 and the second electron transport layer 8 may be provided in contact with each other. The second electron transport layer 8 and the second photoelectric conversion layer 9 may be provided in contact with each other. The second photoelectric conversion layer 9 and the second hole transport layer 10 may be provided in contact with each other. The second hole transport layer 10 and the fourth electrode layer 11 may be provided in contact with each other. The fourth electrode layer 11 and the second substrate 12 may be provided in contact with each other.

[0034] In addition, other layers may be appropriately provided between the various layers constituting the bottom cell 102, for example, to suppress recombination at the interfaces between the various layers or to bond the various layers together.

[0035] In the solar cell 100, a first substrate 1, a first photoelectric conversion layer 4, a second photoelectric conversion layer 9, and a second substrate 12 are provided in this order. In other words, the first photoelectric conversion layer 4 and the second photoelectric conversion layer 9 are provided between the first substrate and the second substrate.

[0036] The solar cell 100 may have a four-terminal structure or a two-terminal structure. In order to reduce the amount of wiring required for the electrode layer, the solar cell 100 may have a two-terminal structure. The two-terminal structure is industrially more desirable than the four-terminal structure.

[0037] In FIG. 3, the solar cell 100 has a two-terminal structure.

[0038] In the solar cell 100, the first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other. For example, as shown in FIG. 3, the first electrode layer 2 and the fourth electrode layer 11 are connected to each other by an electric wire 20. Note that, as long as they are electrically connected, the shape of the electric wire is not limited to a linear shape. For example, the shape of the electric wire may be a flat plate shape.

[0039] In the solar cell 100, the second electrode layer 6 and the third electrode layer 7 are spaced apart. To space the second electrode layer 6 and the third electrode layer 7 apart, the relative positions of the top cell 101 and the bottom cell 102 may be fixed. For example, by joining the periphery of the first substrate 1 and the periphery of the second substrate 12 with a sealing body (not shown), the relative positions of the top cell 101 and the bottom cell 102 can be fixed so that the second electrode layer 6 and the third electrode layer 7 are spaced apart. Here, the phrase "the second electrode layer 6 and the third electrode layer 7 being spaced apart" refers to a state in which the second electrode layer 6 and the third electrode layer 7 are not in direct contact with each other. In the solar cell 100, the second electrode layer 6 and the third electrode layer 7 are spaced apart from each other and are not electrically connected.

[0040] The top cell 101 of the solar cell 100 according to the first embodiment has a structure in which a first electron transport layer 2, a first photoelectric conversion layer 3, and a first hole transport layer 4 are arranged in this order from the first substrate 1 side. That is, the top cell 101 has a "nip structure." First perovskite compounds that can be suitably used as photoelectric conversion materials in the top cell 101 include, for example, compounds that can achieve high photoelectric conversion efficiency due to the "nip structure." Therefore, the solar cell 100 according to the first embodiment can be provided with a top cell 101 having a structure that can achieve high photoelectric conversion efficiency.

[0041] The bottom cell 102 of the solar cell 100 according to the first embodiment has a structure in which a second hole transport layer 10, a second photoelectric conversion layer 9, and a second electron transport layer 8 are arranged in this order from the second substrate 12 side. That is, the bottom cell 102 has a "pin structure." Second perovskite compounds that can be suitably used as photoelectric conversion materials in the bottom cell 102 include, for example, compounds that can achieve high photoelectric conversion efficiency due to the "pin structure." Therefore, the solar cell 100 according to the first embodiment can include a bottom cell 102 having a structure that can achieve high photoelectric conversion efficiency.

[0042] The electricity generated by the solar cell 100 can be extracted from the second electrode layer 6 and the third electrode layer 7 to an external circuit, for example, via electric wires connected to the second electrode layer 6 and the third electrode layer 7. That is, in the solar cell 100, the top cell 101 and the bottom cell 102 are electrically connected in series.

[0043] The solar cell 100 has the above-described configuration, which allows it to have a two-terminal structure, which is an industrially desirable structure. The space between the second electrode layer 6 and the third electrode layer 7, which are spaced apart from each other, is filled with, for example, air.

[0044] The first photoelectric conversion layer 4 contains a first perovskite compound. The second photoelectric conversion layer 9 contains a second perovskite compound. Details of the first perovskite compound and the second perovskite compound will be described later in the sections (First Photoelectric Conversion Layer 4) and (Second Photoelectric Conversion Layer 9). Here, the band gap of the first perovskite compound is larger than the band gap of the second perovskite compound. Therefore, the first photoelectric conversion layer 4 absorbs light with a short wavelength. Here, short wavelength light means light with a wavelength of 450 nm to 550 nm, for example. And the second photoelectric conversion layer 9 absorbs light with a long wavelength. Here, long wavelength light means light with a wavelength of 600 nm to 780 nm, for example. With this configuration, the solar cell 100 can efficiently absorb light.

[0045] The solar cell 100 according to the first embodiment has the above-described configuration, and thus can have high photoelectric conversion efficiency without impairing industrial productivity.

[0046] (Second embodiment) Figure 4 is a cross-sectional view schematically showing a perovskite tandem solar cell according to the second embodiment. The solar cell 200 according to the second embodiment differs from the solar cell 100 according to the first embodiment in the method of electrically connecting the top cell 101 and the bottom cell 102. In Figure 4, the solar cell 200 has a two-terminal structure.

[0047] In the solar cell 200 according to the second embodiment, the top cell 101 and the bottom cell 102 are electrically connected by electrically connecting the second electrode layer 6 and the third electrode layer 7. For example, as shown in FIG. 4, the second electrode layer 6 and the third electrode layer 7 are connected to each other by an electric wire 21. Note that, as long as they are electrically connected, the shape of the electric wire is not limited to a linear shape. For example, the shape of the electric wire may be a flat plate. However, the second electrode layer 6 and the third electrode layer 7 are spaced apart from each other and are not in direct contact with each other.

[0048] The electricity generated by the solar cell 200 can be extracted to an external circuit from the first electrode layer 2 and the fourth electrode layer 11, for example, via electric wires connected to the first electrode layer 2 and the fourth electrode layer 11, respectively. That is, in the solar cell 200, the top cell 101 and the bottom cell 102 are electrically connected in series.

[0049] The solar cell 200 has the above-described configuration, and thus can have a two-terminal structure.

[0050] The solar cell 200 according to the second embodiment has the same configuration as the solar cell 100 according to the first embodiment, except that the electrical connections between the top cell 101 and the bottom cell 102 are different.

[0051] The solar cell 200 according to the second embodiment has the above-described configuration, and thus can have high photoelectric conversion efficiency without impairing industrial productivity.

[0052] (Third embodiment) Fig. 5 shows a solar cell 300 according to a third embodiment. The solar cell 300 according to the third embodiment differs from the solar cell 100 according to the first embodiment in the method of electrically connecting the top cell 101 and the bottom cell 102. In Fig. 5, the solar cell 300 has a two-terminal structure.

[0053] In a solar cell 300 according to the third embodiment, the top cell 101 and the bottom cell 102 are electrically connected in parallel to each other. As shown in Fig. 5, the first electrode layer 2 and the third electrode layer 7 are electrically connected to each other, and the second electrode layer 6 and the fourth electrode layer 11 are electrically connected to each other. The first electrode layer 2 and the third electrode layer 7 are electrically connected to each other, for example, via a first electric wire 22. The second electrode layer 6 and the fourth electrode layer 11 are electrically connected to each other, for example, via a second electric wire 23. Electricity is then extracted to an external circuit via the first electric wire 22 and the second electric wire 23.

[0054] The above-described configuration allows the solar cell 300 to have a two-terminal structure. Furthermore, in the solar cell 300, the top cell 101 and the bottom cell 102 are connected in parallel, which has the effect of stabilizing the photoelectric conversion efficiency in an environment where the current is likely to change.

[0055] The solar cell 300 according to the third embodiment has the same configuration as the solar cell 100 according to the first embodiment, except that the electrical connections between the top cell 101 and the bottom cell 102 are different.

[0056] The solar cell 300 according to the third embodiment has the above-described configuration, and thus can have high photoelectric conversion efficiency without impairing industrial productivity.

[0057] (Fourth embodiment) Figure 6 is a cross-sectional view schematically showing a perovskite tandem solar cell according to a fourth embodiment. The solar cell 400 according to the fourth embodiment differs from the solar cell 100 according to the first embodiment in that the periphery of the first substrate 1 and the periphery of the second substrate 12 are joined to each other by a sealant 13, and in that a filler 14 is provided between the second electrode layer 6 and the third electrode layer 7. Note that in Figure 6, the solar cell 400 has a two-terminal structure.

[0058] As shown in Fig. 6, in a solar cell 400 according to the fourth embodiment, a sealing body 13 is provided, thereby fixing the relative positions of a top cell 101 and a bottom cell 102 so that, for example, a second electrode layer 6 and a third electrode layer 7 are spaced apart from each other. In the solar cell 400, for example, the inside of a space surrounded by a first substrate 1, a second substrate 12, and the sealing body 13 is sealed. As shown in Fig. 6, the top cell 101 and the bottom cell 102 are housed inside this space, and the peripheries of the top cell 101 and the bottom cell 102 may be filled with a filler 14.

[0059] The sealing body 13 can be made of, for example, a resin material such as an ultraviolet curable resin or a thermosetting resin, or a rubber material such as butyl rubber.

[0060] Filler 14 may contain, for example, at least one selected from the group consisting of epoxy resin, silicone resin, and polyolefin resin. Filling the space between second electrode layer 6 and third electrode layer 7 with filler 14 increases the refractive index between second electrode layer 6 and third electrode layer 7. This reduces reflection of incident light.

[0061] 6, a solar cell 400 according to the fourth embodiment includes a sealant 13. However, the sealant 13 does not have to be provided. For example, if the filler 14 can also function as a sealant, the sealant can fix the positions of the top cell 101 and the bottom cell 102 such that the second electrode layer 6 and the third electrode layer 7 are spaced apart from each other.

[0062] 6, in the solar cell 400 according to the fourth embodiment, the first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other, thereby connecting the top cell 101 and the bottom cell 102 in series. However, the second electrode layer 6 and the third electrode layer 7 may be electrically connected to each other, thereby connecting the top cell 101 and the bottom cell 102 in series, or the top cell 101 and the bottom cell 102 may be connected in parallel as in the solar cell 300 according to the third embodiment.

[0063] For example, a solar cell module can be formed by connecting a plurality of solar cells 400. Figure 7 is a cross-sectional view schematically showing an example of a solar cell module including a perovskite tandem solar cell according to the fourth embodiment.

[0064] 7 includes a top cell 101 (i.e., the first top cell 101), a second top cell 201, a third top cell 301, a bottom cell 102 (i.e., the first bottom cell 102), a second bottom cell 202, and a third bottom cell 302. The first top cell 101 and the second top cell 102 have the same configuration as the solar cell 400 shown in FIG. 6. Note that in FIG. 7, the solar cell module 500 has a two-terminal structure.

[0065] The first top cell 101, the second top cell 201, and the third top cell 301 are arranged on the light incident surface side of the solar cell module 500. The second electrode layer 6 of the first top cell 101 is electrically connected to the first electrode layer 2 of the second top cell 201 arranged adjacently. The second electrode layer 6 of the second top cell 201 is electrically connected to the first electrode layer 2 of the third top cell 301 arranged adjacently. The first bottom cell 102, the second bottom cell 202, and the third bottom cell 302 are arranged on the side opposite the light incident surface of the solar cell module 500. The third electrode layer 7 of the first bottom cell 102 is electrically connected to the fourth electrode layer 11 of the second bottom cell 202 arranged adjacently. The third electrode layer 7 of the second bottom cell 202 is electrically connected to the fourth electrode layer 11 of the third bottom cell 302 arranged adjacently. That is, in solar cell module 500, first top cell 101, second top cell 201, third top cell 301, first bottom cell 102, second bottom cell 202, and third bottom cell 302 are electrically connected in series. Electricity generated in solar cell module 500 can be extracted to an external circuit from second electrode layer 6 of third top cell 301 and third electrode layer 7 of the third top cell, for example, via electric wires connected to second electrode layer 6 and third electrode layer 7, respectively. Here, in solar cell module 500 shown in FIG. 7 , first top cell 101 and first bottom cell 102 have a configuration in which first electrode layer 2 and fourth electrode layer 11 are electrically connected to each other. In solar cell module 500, second top cell 201 and second bottom cell 202 have a configuration in which first electrode layer 2 and fourth electrode layer 11 are electrically connected to each other via the first cell (i.e., first top cell 101 and first bottom cell 102). In solar cell module 500, third top cell 201 and third bottom cell 202 have a configuration in which first electrode layer 2 and fourth electrode layer 11 are electrically connected to each other via the first cell and second cell (i.e., second top cell 201 and second bottom cell 202).

[0066] Although the solar cell module 500 shown in this embodiment has a configuration in which three top cells and three bottom cells are provided, the number of cells is not limited to this.

[0067] The various layers will be described in detail below.

[0068] (First substrate 1) The first substrate 1 holds each layer of the top cell 101. The first substrate 1 can be made of a transparent material. For example, a glass substrate or a plastic substrate (including a plastic film) can be used. Furthermore, if the first electrode layer 2 has sufficient strength, the first electrode layer 2 can hold each layer, so in this case the first substrate 1 may also serve as the first electrode layer 2. In other words, a first electrode layer 2 that can also function as the first substrate 1 may be used.

[0069] (1st electrode layer 2) The first electrode layer 2 is conductive. The first electrode layer 2 is also translucent. For example, the first electrode layer 2 transmits light from the visible region to the near-infrared region. The first electrode layer 2 can be formed using, for example, a transparent and conductive metal oxide. Examples of such metal oxides include: (i) indium-tin composite oxide, (ii) antimony-doped tin oxide; (iii) fluorine-doped tin oxide; (iv) zinc oxide doped with at least one selected from the group consisting of boron, aluminum, gallium, and indium, or (v) or a combination thereof is.

[0070] The first electrode layer 2 can be formed using an opaque material and providing a light-transmitting pattern. Examples of light-transmitting patterns include linear, wavy, lattice, and punched metal patterns with numerous fine through-holes arranged regularly or irregularly. When the first electrode layer 2 has such a pattern, light can pass through areas where the electrode layer material is not present. Examples of opaque materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or alloys containing any of these. A conductive carbon material may also be used as the opaque material.

[0071] The light transmittance of the first electrode layer 2 may be, for example, 50% or more, or 80% or more. The wavelength of light that should be transmitted through the first electrode layer 2 depends on the absorption wavelength of the first photoelectric conversion layer 4 and the second photoelectric conversion layer 9. The thickness of the first electrode layer 2 is, for example, 1 nm or more and 1000 nm or less.

[0072] (1st electron transport layer 3) The first electron transport layer 3 transports electrons. The first electron transport layer 3 includes a semiconductor. The first electron transport layer 3 is preferably formed from a semiconductor with a band gap of 3.0 eV or more. By forming the first electron transport layer 3 from a semiconductor with a band gap of 3.0 eV or more, visible light and infrared light can be transmitted to the first photoelectric conversion layer 4. Examples of semiconductors include organic or inorganic n-type semiconductors.

[0073] Examples of organic n-type semiconductors include imide compounds, quinone compounds, fullerenes, and fullerene derivatives. Examples of inorganic n-type semiconductors include metal oxides, metal nitrides, and perovskite oxides. Examples of metal oxides include oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, and Cr. The metal oxide preferably contains at least one selected from the group consisting of titanium oxide and tin oxide as a primary component. Here, "the metal oxide contains at least one selected from the group consisting of titanium oxide and tin oxide as a primary component" means that the metal oxide contained in the first electron transport layer 3 contains at least 50 mol% of titanium oxide and tin oxide in total. TiO2 is preferred as the metal oxide. An example of a metal nitride is GaN. Examples of perovskite oxides are SrTiO3, CaTiO3, and ZnTiO3.

[0074] The first electron transport layer 3 may be formed of a material having a band gap greater than 6.0 eV. Examples of materials having a band gap greater than 6.0 eV include: (i) an alkali metal or alkaline earth metal halide, such as lithium fluoride or barium fluoride, or (ii) alkaline earth metal oxides, such as magnesium oxide; In this case, in order to ensure the electron transporting properties of the first electron transporting layer 3, the thickness of the first electron transporting layer 3 may be, for example, 10 nm or less.

[0075] The first electron transport layer 3 may include a plurality of layers made of different materials.

[0076] (First photoelectric conversion layer 4) The first photoelectric conversion layer 4 contains a first perovskite compound. That is, the first photoelectric conversion layer 4 contains, as a photoelectric conversion material, a first perovskite compound composed of monovalent cations, divalent cations, and halogen anions. The photoelectric conversion material is a light-absorbing material.

[0077] In this embodiment, the first perovskite compound may be a compound represented by the chemical formula A1B1X13, where A1 is a monovalent cation, B1 is a divalent cation, and X1 is a halogen anion.

[0078] In accordance with the terminology commonly used for perovskite compounds, A1, B1, and X1 are also referred to herein as A1 sites, B1 sites, and X1 sites, respectively.

[0079] In this embodiment, the first perovskite compound may have a perovskite-type crystal structure represented by the chemical formula A1B1X13, where, for example, a monovalent cation is located at the A1 site, a divalent cation is located at the B1 site, and a halogen anion is located at the X1 site.

[0080] (A1 site) The monovalent cation located at the A1 site is not limited. Examples of the monovalent cation are organic cations or alkali metal cations. Examples of the organic cation are methylammonium cation (i.e., CH3NH3 + ), formamidinium cation (i.e., NH2CHNH2 + ), phenylethylammonium cation (i.e., C6H5C2H4NH3 + ), or guanidinium cation (i.e., CH6N3 + ) An example of an alkali metal cation is the cesium cation (i.e., Cs + )

[0081] For high photoelectric conversion efficiency, the A1 site is occupied by, for example, Cs + , formamidinium cation and methylammonium cation.

[0082] The cations constituting the A1 site may be a mixture of the above-described organic cations, or may be a mixture of at least one of the above-described organic cations and at least one of the above-described metal cations.

[0083] (B1 site) The divalent cation located at the B1 site is not limited. Examples of divalent cations include divalent cations of elements from Group 13 to Group 15. For example, the B1 site may be a Pb cation, i.e., Pb 2+ Includes:

[0084] (X1 site) The halogen anion located at the X1 site is not limited.

[0085] The elements, ie, ions, located at each of the A1, B1, and X1 sites may be of one type or of multiple types.

[0086] Specific examples of the first perovskite compound include CH3NH3PbI3, CH3CH2NH3PbI3, HC(NH2)2PbI3, CH3NH3PbBr3, CH3NH3Cl3, CsPbI3, and CsPbBr3.

[0087] The first photoelectric conversion layer 4 may contain materials other than the photoelectric conversion material. For example, the first photoelectric conversion layer 4 may further contain a quencher substance to reduce the defect density of the first perovskite compound. The quencher substance is a fluorine compound such as tin fluoride. The molar ratio of the quencher substance to the photoelectric conversion material may be 5% or more and 20% or less.

[0088] The first photoelectric conversion layer 4 may mainly contain a first perovskite compound composed of monovalent cations, divalent cations, and halogen anions.

[0089] The phrase "the first photoelectric conversion layer 4 mainly contains a first perovskite compound composed of monovalent cations, divalent cations, and halogen anions" means that the first photoelectric conversion layer 4 contains 70% by mass or more (preferably 80% by mass or more) of the first perovskite compound composed of monovalent cations, divalent cations, and halogen anions.

[0090] The first photoelectric conversion layer 4 may contain impurities. The first photoelectric conversion layer 4 may further contain a compound other than the above-mentioned first perovskite compound.

[0091] The first photoelectric conversion layer 4 may have a thickness of, for example, about 100 nm or more and 2000 nm or less. The first perovskite compound contained in the first photoelectric conversion layer 4 may be formed using a solution coating method, a co-evaporation method, or the like.

[0092] Furthermore, the first photoelectric conversion layer 4 may be in a form in which it is partially mixed with the first electron transport layer 3 described above and the first hole transport layer 5 described below, or it may be in a form in which it has a large area of interface with the first electron transport layer 3 and the first hole transport layer 5 within the film.

[0093] The top cell 101 is required to transmit long wavelength light to the bottom cell 102. In other words, the top cell 101 is required to absorb short wavelength light. Therefore, the band gap of the first perovskite compound contained in the first photoelectric conversion layer 4 is larger than the band gap of the second photoelectric conversion layer contained in the second photoelectric conversion layer 9.

[0094] (First hole transport layer 5) The first hole transport layer 5 contains a hole transport material. The hole transport material is a material that transports holes. Examples of hole transport materials are organic or inorganic semiconductors.

[0095] Typical examples of organic compounds used as hole transport materials include phenylamine or triphenylamine derivatives containing a tertiary amine in the skeleton, and poly(3,4-ethylenedioxythiophene) (hereinafter referred to as "PEDOT") compounds containing a thiophene structure. The molecular weight is not particularly limited, but polymers may also be used. Specific examples of typical organic compounds used as hole transport materials include 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene (hereinafter referred to as "spiro-OMeTAD"), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (hereinafter referred to as "PTAA"), poly(3-hexylthiophene-2,5-diyl) (hereinafter referred to as "P3HT"), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (hereinafter referred to as "PEDOT:PSS"), and copper phthalocyanine (hereinafter referred to as "CuPc").

[0096] Inorganic semiconductors are p-type semiconductors. Examples of inorganic semiconductors are CuO, Cu2O, CuSCN, or nickel oxide.

[0097] The first hole transport layer 5 may include a plurality of layers formed from different materials.

[0098] The thickness of the first hole transport layer 5 is preferably 1 nm or more and 1000 nm or less, more preferably 10 nm or more and 500 nm or less, and even more preferably 10 nm or more and 50 nm or less. When the thickness of the first hole transport layer 5 is 1 nm or more and 1000 nm or less, sufficient hole transport properties can be exhibited. Furthermore, when the thickness of the first hole transport layer 5 is 1 nm or more and 1000 nm or less, the resistance of the hole transport layer 5 is low, and light is converted to electricity with high efficiency.

[0099] The film can be formed by any of various known coating or printing methods. Examples of coating methods include doctor blade coating, bar coating, spray coating, dip coating, and spin coating. An example of printing methods is screen printing.

[0100] The first hole transport layer 5 may contain a supporting electrolyte and a solvent. The supporting electrolyte and the solvent have the effect of stabilizing holes in the first hole transport layer 5, for example.

[0101] Examples of the supporting electrolyte include ammonium salts or alkali metal salts. Examples of the ammonium salt include tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, imidazolium salts, and pyridinium salts. Examples of the alkali metal salt include lithium perchlorate and potassium boron tetrafluoride.

[0102] The solvent contained in the first hole transport layer 5 may have high ionic conductivity. The solvent may be an aqueous solvent or an organic solvent. From the viewpoint of stabilizing the solute, an organic solvent is preferable. Examples of organic solvents include heterocyclic compounds such as tert-butylpyridine (hereinafter referred to as "t-BP"), pyridine, or n-methylpyrrolidone.

[0103] The solvent contained in the first hole transport layer 5 may be an ionic liquid. The ionic liquid may be used alone or in combination with other solvents. Ionic liquids are desirable because of their low volatility and high flame retardancy.

[0104] Examples of ionic liquids are imidazolium compounds such as 1-ethyl-3-methylimidazolium tetracyanoborate, pyridine compounds, alicyclic amine compounds, aliphatic amine compounds, or azonium amine compounds.

[0105] (Second electrode layer 6, third electrode layer 7) The second electrode layer 6 and the third electrode layer 7 are conductive. Furthermore, the second electrode layer 6 and the third electrode layer 7 are translucent. The second electrode layer 6 and the third electrode layer 7 transmit, for example, light in the visible to near-infrared region. The second electrode layer 6 and the third electrode layer 7 can be formed using, for example, a transparent and conductive metal oxide. Examples of such metal oxides include: (i) indium-tin composite oxide, (ii) antimony-doped tin oxide; (iii) fluorine-doped tin oxide; (iv) zinc oxide doped with at least one of boron, aluminum, gallium, and indium; or (v) or a combination thereof is.

[0106] The second electrode layer 6 and the third electrode layer 7 can also be formed using an opaque material with a light-transmitting pattern. Examples of light-transmitting patterns include linear, wavy, lattice, and punched metal patterns with numerous fine through-holes arranged regularly or irregularly. When the second electrode layer 6 and the third electrode layer 7 have such patterns, light can pass through areas where no electrode layer material is present. Examples of opaque materials include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or alloys containing any of these. A conductive carbon material may also be used as the opaque material.

[0107] The light transmittance of the second electrode layer 6 and the third electrode layer 7 may be, for example, 50% or more, or 80% or more. The wavelength of light that should be transmitted through the second electrode layer 6 and the third electrode layer 7 depends on the absorption wavelength of the second photoelectric conversion layer 9. The thickness of the second electrode layer 6 and the third electrode layer 7 is, for example, 1 nm or more and 1000 nm or less.

[0108] (Second electron transport layer 8) The second electron transport layer 8 transports electrons. The second electron transport layer 8 includes a semiconductor. The second electron transport layer 8 is preferably formed from a semiconductor with a band gap of 3.0 eV or more. By forming the first electron transport layer 3 from a semiconductor with a band gap of 3.0 eV or more, visible light and infrared light can be transmitted to the first photoelectric conversion layer 4. Examples of semiconductors include organic or inorganic n-type semiconductors.

[0109] Examples of organic n-type semiconductors are imide compounds, quinone compounds, fullerenes, or fullerene derivatives. Examples of inorganic n-type semiconductors are metal oxides, metal nitrides, or perovskite oxides. Examples of metal oxides are oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, or Cr. TiO2 is preferred. An example of a metal nitride is GaN. Examples of perovskite oxides are SrTiO3, CaTiO3, and ZnTiO3.

[0110] The second electron transport layer 8 may be formed of a material having a band gap greater than 6.0 eV. Examples of materials having a band gap greater than 6.0 eV include: (i) an alkali metal or alkaline earth metal halide, such as lithium fluoride or barium fluoride; or (ii) alkaline earth metal oxides, such as magnesium oxide; In this case, in order to ensure the electron transporting properties of the second electron transporting layer 8, the thickness of the second electron transporting layer 8 may be, for example, 10 nm or less.

[0111] The second electron transport layer 8 may include multiple layers made of different materials.

[0112] (Second photoelectric conversion layer 9) The second photoelectric conversion layer 9 contains a second perovskite compound. That is, the second photoelectric conversion layer 9 contains, as a photoelectric conversion material, a second perovskite compound composed of monovalent cations, divalent cations, and halogen anions. The photoelectric conversion material is a light-absorbing material.

[0113] In this embodiment, the second perovskite compound may be a compound represented by the chemical formula A2B2X23, where A2 is a monovalent cation, B2 is a divalent cation, and X2 is a halogen anion.

[0114] In accordance with the terminology commonly used for perovskite compounds, A2, B2, and X2 are also referred to herein as A2 sites, B2 sites, and X2 sites, respectively.

[0115] In this embodiment, the second perovskite compound may have a perovskite-type crystal structure represented by the chemical formula A2B2X23, where, for example, a monovalent cation is located at the A2 site, a divalent cation is located at the B2 site, and a halogen anion is located at the X2 site.

[0116] (A2 site) The monovalent cation located at the A2 site is not limited. Examples of the monovalent cation are organic cations or alkali metal cations. Examples of the organic cation are methylammonium cation (i.e., CH3NH3 + ), formamidinium cation (i.e., NH2CHNH2 + ), phenylethylammonium cation (i.e., C6H5C2H4NH3 + ), or guanidinium cation (i.e., CH6N3 + ) An example of an alkali metal cation is the cesium cation (i.e., Cs + )

[0117] For high photoelectric conversion efficiency, the A2 site is used for, for example, Cs +, formamidinium cation and methylammonium cation.

[0118] The cations constituting the A2 site may be a mixture of the above-described organic cations, or may be a mixture of at least one of the above-described organic cations and at least one of the above-described metal cations.

[0119] (B2 site) The divalent cation located at the B2 site is not limited. Examples of divalent cations include divalent cations of Group 13 to Group 15 elements. For example, the B2 site may be a Pb cation (i.e., Pb 2+ ) and Sn cations (i.e., Sn 2+ The B2 site includes, for example, a Pb cation and a Sn cation.

[0120] (X2 site) The halogen anion located at the X2 site is not limited.

[0121] The elements, ie, ions, located at each of the A2, B2, and X2 sites may be of one type or of multiple types.

[0122] Specific examples of the second perovskite compound are CH3NH3PbI3, CH3CH2NH3PbI3, CH3NH3SnI3, CH3CH2NH3SnI3, CH3NH3Pb 0.5 Sn 0.5 I3, or CH3CH2NH3Pb 0.5 Sn 0.5 It is magnitude I3.

[0123] The second photoelectric conversion layer 9 may contain a material other than the photoelectric conversion material. For example, the ninth photoelectric conversion layer 9 may further contain a quencher substance to reduce the defect density of the second perovskite compound. The quencher substance is a fluorine compound such as tin fluoride. The molar ratio of the quencher substance to the photoelectric conversion material may be 5% or more and 20% or less.

[0124] The second photoelectric conversion layer 9 may contain impurities. The second photoelectric conversion layer 9 may further contain a compound other than the second perovskite compound.

[0125] The second photoelectric conversion layer 9 may have a thickness of, for example, about 100 nm or more and 2000 nm or less. The second perovskite contained in the second photoelectric conversion layer 9 may be formed using a solution coating method, a co-evaporation method, or the like.

[0126] The second photoelectric conversion layer 9 may be in a form in which it is partially mixed with the second electron transport layer 8 described above and the second hole transport layer 10 described below, or may be in a form in which it has a large area of interface with the second electron transport layer 8 and the second hole transport layer 10 within the film.

[0127] (Second hole transport layer 10) The second hole transport layer 10 contains a hole transport material. A hole transport material is a material that transports holes. Examples of hole transport materials are organic or inorganic semiconductors.

[0128] Typical examples of organic substances and inorganic semiconductors used as the hole transport material contained in the second hole transport layer 10 are the same as those used as the hole transport material contained in the first hole transport layer 5.

[0129] The second hole transport layer 10 may include multiple layers formed from different materials.

[0130] The thickness of the second hole transport layer 10 is preferably 1 nm or more and 1000 nm or less, more preferably 10 nm or more and 500 nm or less, and even more preferably 10 nm or more and 50 nm or less. If the thickness of the second hole transport layer 10 is 1 nm or more and 1000 nm or less, sufficient hole transport properties can be exhibited. Furthermore, if the thickness of the second hole transport layer 10 is 1 nm or more and 1000 nm or less, the resistance of the second hole transport layer 10 is low, and light can be converted to electricity with high efficiency.

[0131] The film can be formed by any of various known coating or printing methods. Examples of coating methods include doctor blade coating, bar coating, spray coating, dip coating, and spin coating. An example of printing methods is screen printing.

[0132] The second hole transport layer 10 may contain a supporting electrolyte and a solvent. The supporting electrolyte and the solvent have the effect of stabilizing holes in the second hole transport layer 10, for example.

[0133] Examples of the supporting electrolyte and solvent that may be contained in the second hole transport layer 10 are the same as the examples of the supporting electrolyte and solvent that may be contained in the first hole transport layer 5.

[0134] (4th electrode layer 11) The fourth electrode layer 11 may or may not be light-transmitting.

[0135] When the fourth electrode layer 11 is a light-transmitting electrode layer, light in the visible to near-infrared region can be transmitted through the fourth electrode layer 11. The light-transmitting electrode layer can be made of a transparent and conductive material.

[0136] Examples of such materials are: (i) titanium oxide doped with at least one element selected from the group consisting of lithium, magnesium, niobium, and fluorine; (ii) gallium oxide doped with at least one selected from the group consisting of tin and silicon; (iii) gallium nitride doped with at least one selected from the group consisting of silicon and oxygen; (iv) indium-tin composite oxide, (v) tin oxide doped with at least one selected from the group consisting of antimony and fluorine; (vi) zinc oxide doped with at least one of boron, aluminum, gallium, and indium, or (vii) Compounds of these is.

[0137] The light-transmitting electrode layer can be formed by using a non-transparent material and providing a light-transmitting pattern. Examples of the light-transmitting pattern include a linear, wavy, lattice, or punched metal pattern in which a large number of fine through-holes are regularly or irregularly arranged. When the light-transmitting electrode layer has such a pattern, light can be transmitted through the areas where the electrode layer material is not present. Examples of the non-transparent material include platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or an alloy containing any of these. A conductive carbon material may also be used as the non-transparent material.

[0138] (Second substrate 12) The second substrate 12 holds each layer of the bottom cell 102. The second substrate 12 can be made of, for example, a transparent material. For example, a glass substrate or a plastic substrate (including a plastic film) can be used. The second substrate 12 may also be made of a non-transparent material. If the fourth electrode layer 11 has sufficient strength, the fourth electrode layer 11 can hold each layer, and in this case, the second substrate 12 may also serve as the fourth electrode layer 11. In other words, a fourth electrode layer 11 that can also function as the second substrate 12 may be used.

[0139] (another layer) Another example of a layer is a porous layer. The porous layer is located, for example, between the first electron transport layer 3 and the first photoelectric conversion layer 4. The porous layer includes a porous body. The porous body includes pores. The pores included in the porous layer located between the first electron transport layer 3 and the first photoelectric conversion layer 4 are connected from the portion in contact with the first electron transport layer 3 to the portion in contact with the first photoelectric conversion layer 4. The pores are typically filled with the material constituting the first photoelectric conversion layer 4, and electrons can move directly from the first photoelectric conversion layer 4 to the electron transport layer 3.

[0140] The porous layer can serve as a base when the first photoelectric conversion layer 4 is formed on the first electron transport layer 3. The porous layer does not hinder the light absorption of the first photoelectric conversion layer 4 or the movement of electrons from the first photoelectric conversion layer 4 to the first electron transport layer 3.

[0141] The porous body that can constitute the porous layer is composed of, for example, a series of insulating or semiconductor particles. Examples of insulating particles include aluminum oxide particles and silicon oxide particles. Examples of semiconductor particles include inorganic semiconductor particles. Examples of inorganic semiconductors include oxides of metal elements, perovskite oxides of metal elements, sulfides of metal elements, and metal chalcogenides. Examples of oxides of metal elements include oxides of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, and Cr. A specific example of an oxide of a metal element is TiO2. Examples of perovskite oxides of metal elements are SrTiO3 and CaTiO3. Examples of sulfides of metal elements are CdS, ZnS, In2S3, PbS, Mo2S, WS2, Sb2S3, Bi2S3, ZnCdS2 and Cu2S. Examples of metal chalcogenides are CdSe, In2Se3, WSe2, HgS, PbSe and CdTe.

[0142] The thickness of the porous layer may be 0.01 μm or more and 10 μm or less, or 0.1 μm or more and 1 μm or less. The porous layer may have a large surface roughness. Specifically, the surface roughness coefficient of the porous layer, given by the effective area / projected area value, may be 10 or more, or may be 100 or more. The projected area is the area of the shadow cast behind an object when the object is illuminated with light from directly in front of it. The effective area is the actual surface area of the object. The effective area can be calculated from the volume determined from the projected area and thickness of the object and the specific surface area and bulk density of the material that makes up the object.

[0143] Another example of a separate layer is a buffer layer. The buffer layer is located between the second electrode layer 6 and the first hole transport layer 5 or between the third electrode layer 7 and the second electron transport layer 8. The buffer layer is provided to prevent damage to the underlying first hole transport layer 5 or second electron transport layer 8 when forming the second electrode layer 6 or the third electrode layer 7, and is required not to inhibit the transport of electrons or holes. Materials constituting the buffer layer include compounds containing organic substances and inorganic semiconductors. In particular, oxides containing transition metals such as molybdenum oxide or tungsten oxide are included.

[0144] (Effects of solar cells) In the solar cells according to the first to fourth embodiments, the first substrate 1, the first electrode layer 2, the second electrode layer 7, and the third electrode layer 8 are translucent. Light is incident on the surface on the first substrate 1 side (e.g., the upper side in FIG. 3). When light is irradiated onto the solar cells according to the first to fourth embodiments, the first photoelectric conversion layer 3 absorbs the short-wavelength light. The second photoelectric conversion layer 9 absorbs the long-wavelength light. As a result, excited electrons and holes are generated in the solar cell 100. Electrons excited in the top cell 101 move to the first electrode layer 2 via the first electron transport layer 3. Holes excited in the top cell 101 move to the second electrode layer 6 via the first hole transport layer 5. Electrons excited in the bottom cell 102 move to the third electrode layer 7 via the second electron transport layer 8. Holes excited in the bottom cell 102 move to the fourth electrode layer 11 via the second hole transport layer 10.

[0145] In the solar cell 100 according to the first embodiment and the solar cell 400 according to the fourth embodiment, the first electron transport layer 3 is electrically connected to the first electrode layer 2. The second hole transport layer 10 is electrically connected to the fourth electrode layer 11. The first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other. Therefore, electrons that migrate from the first electron transport layer 3 to the first electrode layer 2 and holes that migrate from the second hole transport layer 10 to the fourth electrode layer 11 recombine. Holes that migrate from the first hole transport layer 5 to the second electrode layer 6 and electrons that migrate from the second electron transport layer 8 to the third electrode layer 7 are extracted as current from the second electrode layer 6 and the third electrode layer 7. The current extracted from the top cell 101 and the bottom cell 102 is extracted to an external circuit.

[0146] In the solar cell 200 according to the second embodiment, the first hole transport layer 5 is electrically connected to the second electrode layer 6. The second electron transport layer 8 is electrically connected to the third electrode layer 7. The second electrode layer 6 and the third electrode layer 7 are electrically connected to each other. Therefore, holes that move from the first hole transport layer 5 to the second electrode layer 6 and electrons that move from the second electron transport layer 8 to the third electrode layer 7 recombine. The electrons that move from the first electron transport layer 2 to the first electrode layer 2 and the holes that move from the second hole transport layer 10 to the fourth electrode layer 11 are extracted as current from the first electrode layer 2 and the fourth electrode layer 10. The current extracted from the top cell 101 and the bottom cell 102 is extracted to an external circuit.

[0147] In the solar cell 300 according to the third embodiment, the first electron transport layer 3 is electrically connected to the first electrode layer 2. The first hole transport layer 5 is electrically connected to the second electrode layer 6. The second electron transport layer 8 is electrically connected to the third electrode layer 7. The second hole transport layer 10 is electrically connected to the fourth electrode layer 11. The first electrode layer 2 and the third electrode layer 7 are electrically connected to each other. The second electrode layer 6 and the fourth electrode layer 11 are electrically connected to each other. Therefore, electrons that move from the first electron transport layer 3 to the first electrode layer 2 and electrons that move from the second electron transport layer 8 to the third electrode layer 7 are extracted from the first wiring 22. Holes that move from the first hole transport layer 5 to the second electrode layer 6 and holes that move from the second hole transport layer 10 to the fourth electrode layer 11 are extracted from the second wiring 23. That is, electrons and holes excited in the top cell 101 and bottom cell 102 connected in parallel are extracted as a current from the first wiring 22 and the second wiring 23 to an external circuit.

[0148] (An example of solar cell manufacturing method) In the solar cell according to this embodiment, the first electron transport layer 2, the first photoelectric conversion layer 3, the first hole transport layer 4, and the first electrode layer 5 can be formed on the first substrate 1 as the top cell 101 using a coating method such as spin coating, spray coating, die coating, inkjet, gravure coating, and flexo coating, a physical vapor deposition (PVD) method such as evaporation and sputtering, or a chemical vapor deposition (CVD) method using heat, light, or plasma. Similarly, the bottom cell 102 can be formed on the second substrate 11 as the first hole transport layer 10, the second photoelectric conversion layer 9, the first electron transport layer 8, and the second electrode layer 7 can be formed on the second substrate 11 using a coating method such as spin coating, spray coating, die coating, inkjet, gravure coating, and flexo coating, or a PVD method such as evaporation and sputtering, or a CVD method using heat, light, or plasma. Thereafter, the top cell 101 and the bottom cell 102 are integrated together using, for example, a spacer or a filler, and then the top cell 101 and the bottom cell 102 are electrically connected together with an electric wire or the like to form a solar cell. [Industrial Applicability]

[0149] The solar cell of the present disclosure is useful as a variety of solar cells, such as a solar cell to be installed on a roof. [Explanation of symbols]

[0150] 1 First board 2 First electrode layer 3 First electron transport layer 4. First photoelectric conversion layer 5. First hole transport layer 6 Second electrode layer 7 Third electrode layer 8 Second electron transport layer 9 Second photoelectric conversion layer 10 Second hole transport layer 11 4th electrode layer 12 Second board 13 Sealing body 14 Filling material 20,21 Wiring 22 1st wiring 23 2nd wiring 100,200,300,400 solar cells 101 Top Cell (1st Top Cell) 102 Bottom cell (first bottom cell) 201 2nd Top Cell 202 Second Bottom Cell 301 3rd Top Cell 302 3rd Bottom Cell

Claims

1. a first cell in which a first electrode layer, a first electron transport layer, a first photoelectric conversion layer, a first hole transport layer, and a second electrode layer are stacked in this order on a first substrate; a second cell in which a fourth electrode layer, a second hole transport layer, a second photoelectric conversion layer, a second electron transport layer, and a third electrode layer are stacked in this order on a second substrate; Equipped with the first substrate, the first electrode layer, the second electrode layer, and the third electrode layer are light-transmitting; the first cell and the second cell are arranged so that light is incident from the first substrate side, and so that the second electrode layer and the third electrode layer face each other and are spaced apart from each other; the first photoelectric conversion layer contains a first perovskite compound, the second photoelectric conversion layer contains a second perovskite compound, The band gap of the first perovskite compound is larger than the band gap of the second perovskite compound. Solar cell.

2. a space between the second electrode layer and the third electrode layer is filled with air or a filler material; The solar cell according to claim 1 .

3. The filler includes at least one selected from the group consisting of an epoxy resin, a silicone resin, and a polyolefin resin. The solar cell according to claim 2 .

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