Solar Cell

Abstract

A solar cell 100 includes, in order, 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, a second electrode layer 6, 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 11, and a second substrate 12. The first photoelectric conversion layer 4 includes a first perovskite compound, and the second photoelectric conversion layer 9 includes a second perovskite compound. The band gap of the first perovskite compound is greater than the band gap of the second perovskite compound.

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, the photoelectric conversion material is a compound with the chemical formula ABX 3 (wherein A is a monovalent cation, B is a divalent cation, and X is a halogen anion) is used.

[0004] Non-Patent Document 1 describes a perovskite solar cell with the chemical formula CH 3 NH 3 PbI 3 (hereinafter referred to as "MAPbI 3 The perovskite solar cell disclosed in Non-Patent Document 1 uses a perovskite compound represented by the formula: 3 Perovskite compounds represented by TiO 2 , and Spiro-OMeTAD are used as the photoelectric conversion material, the electron transport material, and the hole transport material, respectively.

[0005] Non-Patent Document 2 discloses a perovskite tandem solar cell. The perovskite tandem solar cell has a structure in which a plurality of solar cells using perovskite compounds with different band gaps are stacked on top of each other. The perovskite tandem solar cell can improve the 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: The semiconductor device comprises, in this order, a first substrate, a first electrode layer, a first electron transport layer, a first photoelectric conversion layer, a first hole transport layer, a second electrode layer, a third electrode layer, a second electron transport layer, a second photoelectric conversion layer, a second hole transport layer, a fourth electrode, and a second substrate; 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. Effect of the Invention

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

[0010] [Figure 1A] FIG. 1A is a cross-sectional view showing a schematic example of a typical perovskite tandem solar cell having two terminals. [Figure 1B] FIG. 1B is a cross-sectional view that illustrates a typical modified example of a perovskite tandem solar cell having two terminals. [Diagram 2] FIG. 2 is a perspective view of the perovskite tandem solar cell according to the first embodiment. [Diagram 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 illustrating a schematic diagram of a perovskite tandem solar cell according to the second embodiment. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a schematic diagram of a perovskite tandem solar cell according to the third embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating a schematic diagram of a perovskite tandem solar cell according to the fourth embodiment. [Figure 7] FIG. 7 is a cross-sectional view illustrating a schematic example of a solar cell module including the perovskite tandem solar cell according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Terminology> As used herein, the term "perovskite compound" refers to a compound having the chemical formula ABX 3 (wherein 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 the divalent cation.

[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] The term "perovskite solar cell" as used in this specification means 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" as used herein means a stacked solar cell having a configuration in which a plurality of solar cells using perovskite compounds having different band gaps are stacked on top of each other.

[0017] <Knowledge that formed the basis of this disclosure> The findings that form the basis of this disclosure are described below.

[0018] The perovskite tandem solar cell has a structure in which a top cell arranged on the light incident surface side and a bottom cell arranged on the opposite side to the light incident surface are stacked. The top cell is usually a perovskite solar cell containing a perovskite compound with a large band gap as a photoelectric conversion material. The bottom cell is usually a perovskite solar cell containing a perovskite compound with a band gap smaller than the band gap of the perovskite compound of the top cell as a photoelectric conversion material. By having such a structure, the perovskite tandem solar cell can effectively utilize light over a wide range to improve the conversion efficiency.

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

[0020] The reason for the above relationship between the type of perovskite compound used as the photoelectric conversion material and the structure that provides high photoelectric conversion efficiency is not clear, but one of the reasons 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 does not dissolve even when a perovskite compound is laminated 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, it is thought that solar cells using lead-based perovskite compounds can achieve high photoelectric conversion efficiency when they have an nip structure in which metal oxide-based N-type materials are generally used.

[0022] On the other hand, in the case of the pin structure, an N-type material is placed on top of the perovskite compound. For this reason, in the case of the pin structure, an N-type material that can be manufactured in a process that does not damage the perovskite compound is required. 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, it is believed that solar cells using tin-lead mixed perovskite compounds can achieve high photoelectric conversion efficiency when they have a pin structure in which a fullerene-based N-type material is generally used.

[0023] However, in a perovskite tandem solar cell, it is difficult to stack the top cell and the bottom cell together in a combination of a top cell having a nip structure and a bottom cell having a pin structure. In the case of a general perovskite tandem solar cell, the top cell and the bottom cell are joined together by a recombination layer that recombines electrons and holes. In this case, the top cell and the bottom cell are required to have the same structure, that is, the pin structure or the nip structure. That is, the perovskite tandem solar cell is required to have the configuration shown in, for example, the following Figures 1A and 1B.

[0024] FIG. 1A is a cross-sectional view showing an example of a typical perovskite tandem solar cell having two terminals. FIG. 1B is a cross-sectional view showing a typical modified example of a perovskite tandem solar cell having two terminals. Hereinafter, a structure having two terminals is 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, that is, 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, that is, 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 includes a top cell 2001 having a nip structure and a bottom cell 2002 having a nip structure. Specifically, the 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. The top cell 2001 includes 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 in this order from the light incident surface, i.e., from the top of FIG. 1B. The bottom cell 2002 includes 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 in this order from the light incident surface, i.e., from the top of FIG. 1B.

[0025] Therefore, through intensive research, the present inventors have discovered a perovskite tandem solar cell structure that enables the top cell and bottom cell to have a structure capable of achieving 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 Fig. 3.

[0030] As shown in FIG. 3, in the top cell 101, for example, in 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 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] In addition, another layer may be appropriately provided between the various layers constituting the top cell 101, for example, to suppress recombination at the interface between the various layers or to bond the various layers to each other. The other layer will be explained in the section (other layer) described later.

[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, that is, from the top of FIG.

[0033] As shown in FIG. 3, in the bottom cell 102, for example, in 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 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, between the various layers constituting the bottom cell 102, other layers may be appropriately provided, for example, to suppress recombination at the interfaces between the various layers or to bond the various layers to each other.

[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 more desirable from an industrial standpoint 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 provided at a distance from each other. In order to separate the second electrode layer 6 and the third electrode layer 7, the relative positions of the top cell 101 and the bottom cell 102 may be fixed. For example, the periphery of the first substrate 1 and the periphery of the second substrate 12 may be joined by a sealing body (not shown) to fix the relative positions of the top cell 101 and the bottom cell 102 so that the second electrode layer 6 and the third electrode layer 7 are separated from each other. Here, the second electrode layer 6 and the third electrode layer 7 being separated from each other means 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 separated from each other and are not electrically connected to each other.

[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". The first perovskite compound that can be suitably used as a photoelectric conversion material in the top cell 101 includes, for example, a compound that can realize high photoelectric conversion efficiency by the "nip structure". Therefore, the solar cell 100 according to the first embodiment can include a top cell 101 having a structure that can realize high photoelectric conversion efficiency.

[0041] The bottom cell 102 of the solar cell 100 according to the first embodiment has a structure in which the second hole transport layer 10, the second photoelectric conversion layer 9, and the 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". The second perovskite compound that can be suitably used as a photoelectric conversion material in the bottom cell 102 includes, for example, a compound that can realize high photoelectric conversion efficiency by the "pin structure". Therefore, the solar cell 100 according to the first embodiment can be provided with a bottom cell 102 having a structure that can realize high photoelectric conversion efficiency.

[0042] The electricity generated by the solar cell 100 can be extracted to an external circuit from the second electrode layer 6 and the third electrode layer 7, for example, via electric wires connected to the second electrode layer 6 and the third electrode layer 7, respectively. 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-mentioned configuration, which allows it to have a two-terminal structure that 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 in the following 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, the short wavelength light means light with a wavelength of, for example, 450 nm to 550 nm. And, the second photoelectric conversion layer 9 absorbs light with a long wavelength. Here, the long wavelength light means light with a wavelength of, for example, 600 nm to 780 nm. By adopting such a configuration, the solar cell 100 can efficiently absorb light.

[0045] By virtue of having the above-mentioned configuration, the solar cell 100 according to the first embodiment can have high photoelectric conversion efficiency without impairing industrial productivity.

[0046] Second embodiment Fig. 4 is a cross-sectional view showing a schematic diagram of 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 Fig. 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 shape. However, the second electrode layer 6 and the third electrode layer 7 are separated 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-mentioned configuration and thus can have a two-terminal structure.

[0050] The solar cell 200 according to the second embodiment has a similar configuration to 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-mentioned configuration and can therefore 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 the 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. Then, electricity is taken out to an external circuit via the first electric wire 22 and the second electric wire 23.

[0054] The solar cell 300 can have a two-terminal structure by having the above-mentioned configuration. Furthermore, in the solar cell 300, the top cell 101 and the bottom cell 102 are connected in parallel, which provides 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 a similar configuration to 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-mentioned configuration and can therefore have high photoelectric conversion efficiency without impairing industrial productivity.

[0057] (Fourth embodiment) Fig. 6 is a cross-sectional view showing a schematic diagram of 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 sealing body 13, and in that a filler 14 is provided between the second electrode layer 6 and the third electrode layer 7. In Fig. 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, and thereby the relative positions of a top cell 101 and a bottom cell 102 are fixed 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 periphery 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] The filler 14 may contain at least one selected from the group consisting of, for example, an epoxy resin, a silicone resin, and a polyolefin resin. The refractive index between the second electrode layer 6 and the third electrode layer 7 increases when the filler 14 is filled between the second electrode layer 6 and the third electrode layer 7. This reduces the reflection of incident light.

[0061] 6, a solar cell 400 according to the fourth embodiment is provided with a sealant 13. However, the sealant 13 does not have to be provided. For example, when 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 to each other. Figure 7 is a cross-sectional view that illustrates a schematic example of a solar cell module including the perovskite tandem solar cell according to the fourth embodiment.

[0064] The solar cell module 500 shown in Fig. 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 disposed 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 disposed 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 disposed adjacently. The first bottom cell 102, the second bottom cell 202, and the third bottom cell 302 are disposed on the opposite side of 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 disposed 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 disposed adjacently. That is, in the solar cell module 500, the first top cell 101, the second top cell 201, the third top cell 301, the first bottom cell 102, the second bottom cell 202, and the third bottom cell 302 are electrically connected in series. Electricity generated in the solar cell module 500 can be taken out from the second electrode layer 6 of the third top cell 301 and the third electrode layer 7 of the third top cell to an external circuit, for example, via electric wires connected to the second electrode layer 6 and the third electrode layer 7, respectively. Here, in the solar cell module 500 shown in FIG. 7, the first top cell 101 and the first bottom cell 102 have a configuration in which the first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other. In addition, in the solar cell module 500, the second top cell 201 and the second bottom cell 202 have a configuration in which the first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other via the first cell (i.e., the first top cell 101 and the first bottom cell 102). In addition, in the solar cell module 500, the third top cell 201 and the third bottom cell 202 have a configuration in which the first electrode layer 2 and the fourth electrode layer 11 are electrically connected to each other via the first cell and the second cell (i.e., the second top cell 201 and the 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 are 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. In addition, 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 function 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, for example, using 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 of these It is.

[0070] The first electrode layer 2 can be formed by providing a light-transmitting pattern using a non-transparent material. Examples of the light-transmitting pattern include a line-like, wavy-like, lattice-like, or punched metal-like pattern in which a large number of fine through-holes are regularly or irregularly arranged. When the first electrode layer 2 has such a pattern, light can be transmitted through the portion where the electrode layer material is not present. Examples of the non-transparent material are platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or an alloy containing any of these. A conductive carbon material may be used as the non-transparent 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 the first electrode layer 2 should transmit depends on the absorption wavelengths 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] (First 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 desirably formed of a semiconductor having a band gap of 3.0 eV or more. By forming the first electron transport layer 3 with a semiconductor having 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 the semiconductor include organic or inorganic n-type semiconductors.

[0073] 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. The metal oxide preferably contains at least one selected from the group consisting of titanium oxide and tin oxide as a main component. Here, "the metal oxide contains at least one selected from the group consisting of titanium oxide and tin oxide as a main component" means that the metal oxide contained in the first electron transport layer 3 contains 50 mol % or more of titanium oxide and tin oxide in total. Examples of metal oxides include TiO 2 An example of a metal nitride is GaN. An example of a perovskite oxide is SrTiO 3 , CaTiO 3 and ZnTiO 3 It is.

[0074] The first electron transport layer 3 may be formed of a material having a band gap larger than 6.0 eV. Examples of materials having a band gap larger 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 property 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 a first perovskite compound composed of monovalent cations, divalent cations, and halogen anions as a photoelectric conversion material. The photoelectric conversion material is a light absorbing material.

[0077] In this embodiment, the first perovskite compound has the chemical formula A1B1X1 3 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 site, B1 site, and X1 site, respectively.

[0079] In this embodiment, the first perovskite compound has the chemical formula A1B1X1 3 As an 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 monovalent cations are organic cations or alkali metal cations. Examples of organic cations are methylammonium cation (i.e., CH 3 NH 3 + ), formamidinium cation (i.e., NH 2 CHNH 2 + ), phenylethylammonium cation (i.e., C 6 H 5 C 2 H 4 NH 3 + ), or guanidinium cations (i.e., CH 6 N 3 +). An example of an alkali metal cation is the cesium cation (i.e., Cs + ).

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

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

[0083] (B1 site) The divalent cation located at the B1 site is not limited. Examples of the divalent cation are divalent cations of elements in groups 13 to 15. For example, the B1 site is 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] A specific example of the first perovskite compound is CH 3 NH 3 PbI 3 , C.H. 3 CH 2 NH 3 PbI 3 , HC(NH 2 ) 2 PbI 3 , C.H. 3 NH 3 PbBr 3 , C.H. 3 NH 3 Cl 3, CsPbI 3 , or CsPbBr 3 etc.

[0087] The first photoelectric conversion layer 4 may contain a material other than the photoelectric conversion material. For example, the first photoelectric conversion layer 4 may further contain a quencher substance for reducing 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 sentence "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 mass% or more (preferably 80 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 by using a solution coating method, a co-evaporation method, or the like.

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

[0093] The top cell 101 needs to transmit light with a long wavelength to the bottom cell 102. In other words, the top cell 101 is required to absorb light with a short wavelength. 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. A hole transport material is a material that transports holes. Examples of hole transport materials are organic or inorganic semiconductors.

[0095] Representative examples of organic substances 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 may be a polymer. Specific examples of representative organic substances 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"), or copper phthalocyanine (hereinafter referred to as "CuPc").

[0096] Inorganic semiconductors are p-type semiconductors. Examples of inorganic semiconductors are CuO, Cu 2 O, 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. If 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, if 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, so that light is converted to electricity with high efficiency.

[0099] The method for forming the film can employ various known coating or printing methods. Examples of the coating method include a doctor blade method, a bar coating method, a spray method, a dip coating method, or a spin coating method. An example of the printing method is a screen printing method.

[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 are ammonium salts or alkali metal salts. Examples of the ammonium salts are tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, imidazolium salts, or pyridinium salts. Examples of the alkali metal salts are lithium perchlorate or 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 the organic solvent 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 a mixture with other solvents. Ionic liquids are desirable in terms of low volatility and high flame retardancy.

[0104] Examples of ionic liquids are imidazolium compounds such as 1-ethyl-3-methylimidazolium tetracyanoborate, pyridine compounds, cycloaliphatic 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. In addition, 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 light, for example, from the visible region to the near infrared region. The second electrode layer 6 and the third electrode layer 7 can be formed, for example, using 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 of these It is.

[0106] The second electrode layer 6 and the third electrode layer 7 can be formed by using a non-transparent material and providing a light-transmitting pattern. Examples of the light-transmitting pattern are a line-like, wavy-like, lattice-like, or punched metal-like pattern in which a large number of fine through-holes are regularly or irregularly arranged. When the second electrode layer 6 and the third electrode layer 7 have such a pattern, light can be transmitted through the portion where the electrode layer material is not present. Examples of the non-transparent material are platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or an alloy containing any of these. A conductive carbon material may be used as the non-transparent 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 the second electrode layer 6 and the third electrode layer 7 should transmit 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 desirably formed of a semiconductor having a band gap of 3.0 eV or more. By forming the first electron transport layer 3 with a semiconductor having 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 the semiconductor 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. TiO 2 An example of a metal nitride is GaN. An example of a perovskite oxide is SrTiO 3 , CaTiO 3 and ZnTiO 3 It is.

[0110] The second electron transport layer 8 may be formed of a material having a band gap larger than 6.0 eV. Examples of materials having a band gap larger than 6.0 eV include: (i) Alkali metal or alkaline earth metal halides, 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 property 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 a plurality of 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 a second perovskite compound composed of monovalent cations, divalent cations, and halogen anions as a photoelectric conversion material. The photoelectric conversion material is a light absorbing material.

[0113] In this embodiment, the second perovskite compound has the chemical formula A2B2X2 3 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 site, B2 site, and X2 site, respectively.

[0115] In this embodiment, the second perovskite compound has the chemical formula A2B2X2 3 As an 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 monovalent cations are organic cations or alkali metal cations. Examples of organic cations are methylammonium cation (i.e., CH 3 NH 3 + ), formamidinium cation (i.e., NH 2 CHNH 2 + ), phenylethylammonium cation (i.e., C 6 H5 C 2 H 4 NH 3 + ), or guanidinium cations (i.e., CH 6 N 3 + ). An example of an alkali metal cation is the cesium cation (i.e., Cs + ).

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

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

[0119] (B2 site) The divalent cation located at the B2 site is not limited. Examples of divalent cations are divalent cations of Groups 13 to 15. For example, the B2 site is 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] A specific example of the second perovskite compound is CH 3 NH 3 PbI3 , C.H. 3 CH 2 NH 3 PbI 3 , C.H. 3 NH 3 SnI 3 , C.H. 3 CH 2 NH 3 SnI 3 , C.H. 3 NH 3 Pb 0.5 Sn 0.5 I 3 , or C.H. 3 CH 2 NH 3 Pb 0.5 Sn 0.5 I 3 etc.

[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 for reducing 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 above-mentioned 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 by using a solution coating method, a co-evaporation method, or the like.

[0126] In addition, the second photoelectric conversion layer 9 may be in a form in which it is partially mixed with the above-mentioned second electron transport layer 8 and the second hole transport layer 10 described later, or it 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] Representative 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 a plurality of 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, so that light can be converted to electricity with high efficiency.

[0131] The method for forming the film can employ various known coating or printing methods. Examples of the coating method include a doctor blade method, a bar coating method, a spray method, a dip coating method, or a spin coating method. An example of the printing method is a screen printing method.

[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 the solvent that may be contained in the second hole transport layer 10 are the same as the examples of the supporting electrolyte and the 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 have light-transmitting properties.

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

[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 element 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) any combination of these It is.

[0137] The electrode layer having light transmission can be formed by providing a light transmitting pattern using a non-transparent material. Examples of the light transmitting pattern are a line shape, a wavy line shape, a lattice shape, or a punching metal pattern in which a large number of fine through holes are arranged regularly or irregularly. When the electrode layer having light transmission has these patterns, light can transmit through the part where the electrode layer material does not exist. Examples of the non-transparent material are platinum, gold, silver, copper, aluminum, rhodium, indium, titanium, iron, nickel, tin, zinc, or an alloy containing any of these. A conductive carbon material may 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, so in this case, the second substrate 12 may also function 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) An example of another 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 a 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 impede light absorption by the first photoelectric conversion layer 4 and transfer 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, for example, composed of a series of insulating or semiconductor particles. Examples of insulating particles are aluminum oxide particles and silicon oxide particles. Examples of semiconductor particles are inorganic semiconductor particles. Examples of inorganic semiconductors are oxides of metal elements, perovskite oxides of metal elements, sulfides of metal elements, and metal chalcogenides. Examples of oxides of metal elements are oxides of the metal elements Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, and Cr. Specific examples of oxides of metal elements include TiO 2An example of a perovskite oxide of a metal element is SrTiO 3 and CaTiO 3 Examples of sulfides of metallic elements are CdS, ZnS, In 2 S 3 , PbS, Mo 2 S., W.S. 2 , Sb 2 S 3 , Bi 2 S 3 , ZnCdS 2 and Cu 2 S. Examples of metal chalcogenides are CdSe, In 2 Se 3 , WSe 2 , 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 value of effective area / projected area may be 10 or more, or may be 100 or more. The projected area is the area of ​​the shadow that is formed behind an object when the object is illuminated with light from the front. The effective area is the actual surface area of ​​the object. The effective area can be calculated from the volume calculated from the projected area and thickness of the object, and the specific surface area and bulk density of the material that constitutes the object.

[0143] Another example of the 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 suppress damage to the first hole transport layer 5 or the second electron transport layer 8 that serves as the base when the second electrode layer 6 or the third electrode layer 7 is formed, and is required not to inhibit the transport of electrons or holes. Examples of materials constituting the buffer layer include compounds containing organic substances and inorganic semiconductors. In particular, examples include oxides containing transition metals such as molybdenum oxide or tungsten oxide.

[0144] (Effects of solar cells) In the solar cell 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 from the surface on the first substrate 1 side (for example, the upper part in FIG. 3). When the solar cell according to the first to fourth embodiments is irradiated with light, the first photoelectric conversion layer 3 absorbs the light with a short wavelength. Then, the second photoelectric conversion layer 9 absorbs the light with a long wavelength. As a result, excited electrons and holes are generated in the solar cell 100. The electrons excited in the top cell 101 move to the first electrode layer 2 through the first electron transport layer 3. The holes excited in the top cell 101 move to the second electrode layer 6 through the first hole transport layer 5. The electrons excited in the bottom cell 102 move to the third electrode layer 7 through the second electron transport layer 8. The holes excited in the bottom cell 102 move to the fourth electrode layer 11 through 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, the electrons that have moved from the first electron transport layer 3 to the first electrode layer 2 and the holes that have moved from the second hole transport layer 10 to the fourth electrode layer 11 are recombined. The holes that have moved from the first hole transport layer 5 to the second electrode layer 6 and the electrons that have moved from the second electron transport layer 8 to the third electrode layer 7 are extracted as a 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 case of 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, the holes that have moved from the first hole transport layer 5 to the second electrode layer 6 and the electrons that have moved from the second electron transport layer 8 to the third electrode layer 7 are recombined. The electrons that have moved from the first electron transport layer 2 to the first electrode layer 2 and the holes that have moved from the second hole transport layer 10 to the fourth electrode layer 11 are extracted as a 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 case of 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, the electrons that have moved from the first electron transport layer 3 to the first electrode layer 2 and the electrons that have moved from the second electron transport layer 8 to the third electrode layer 7 are taken out from the first wiring 22. The holes that have moved from the first hole transport layer 5 to the second electrode layer 6 and the holes that have moved from the second hole transport layer 10 to the fourth electrode layer 11 are taken out from the second wiring 23. That is, electrons and holes excited in top cell 101 and bottom cell 102 connected in parallel are extracted as a current from first wiring 22 and second wiring 23 to an external circuit.

[0148] (An example of how solar cells are manufactured) In the solar cell according to the present 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 by using a coating method such as spin coating, spray coating, die coating, inkjet, gravure coating, and flexo coating, as well as a physical vapor deposition (PVD) method such as vapor deposition and sputtering, and a chemical vapor deposition (CVD) method using heat, light, or plasma. Similarly, 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 as the bottom cell 102 by using a coating method such as spin coating, spray coating, die coating, inkjet, gravure coating, and flexo coating, as well as a PVD method such as vapor deposition and sputtering, and 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 (1st Bottom Cell) 201 2nd Top Cell 202 Second Bottom Cell 301 3rd Top Cell 302 3rd Bottom Cell

Claims

1. A solar cell comprising: The solar cell 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 cell and the second cell are arranged such that light is incident from the first electrode layer side, and the second electrode layer and the third electrode layer face each other and are spaced apart from each other; a space between the second electrode layer and the third electrode layer is filled with air or a filler; 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; The solar cell has the following configuration (i), (ii), or (iii): (i) the first electrode layer and the fourth electrode layer are electrically connected to each other; (ii) the second electrode layer and the third electrode layer are electrically connected to each other; or (iii) the first electrode layer and the third electrode layer are electrically connected to each other, and the second electrode layer and the fourth electrode layer are electrically connected to each other; Solar cell.

2. the first electron transport layer comprises a metal oxide; The solar cell according to claim 1 .

3. The metal oxide contains at least one selected from the group consisting of titanium oxide and tin oxide as a main component. The solar cell according to claim 2 .

4. 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 1 .

5. The solar cell satisfies the configuration (i), The first electrode layer and the fourth electrode layer are connected to each other by an electric wire. The solar cell according to claim 1 .

6. The solar cell satisfies the configuration (ii), The second electrode layer and the third electrode layer are connected to each other by an electric wire. The solar cell according to claim 1 .

7. The solar cell satisfies the configuration (iii), the first electrode layer and the third electrode layer are connected to each other by an electric wire; and The second electrode layer and the fourth electrode layer are connected to each other by an electric wire. The solar cell according to claim 1 .

Images