Photoelectric conversion element

Abstract

Provided is a photoelectric conversion element in a tandem solar cell that reduces shear stress between the light absorption layer of a top cell and the light absorption layer of a bottom cell, which occurs due to temperature changes or the like, thereby suppressing peeling between the two light absorption layers. [Solution] The photoelectric conversion element 10 in the tandem solar cell includes a top cell 11 arranged on the light-receiving surface side and a bottom cell 12 arranged on the back surface side, and the top cell light-absorbing layer 114 is divided into multiple regions by voids 14 formed in the top cell light-absorbing layer 114.

Description

Technical Field

[0004] , , , ,

[0005] , , ,

[0001] The present disclosure relates to a photoelectric conversion element in a tandem solar cell.

Background Art

[0002] In order to improve the power generation efficiency of solar cells, tandem solar cells in which different types of light absorption layers (photoelectric conversion layers) are stacked have been proposed. As an example of a tandem solar cell, a perovskite / silicon solar cell can be mentioned (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a tandem solar cell, since different types of light absorption layers are stacked, there is a difference in the coefficient of thermal expansion between the light absorption layer of the top cell and the light absorption layer of the bottom cell. When a temperature change occurs in the tandem solar cell, due to this difference in the coefficient of thermal expansion, shear stress is generated in the region between the light absorption layer of the top cell and the light absorption layer of the bottom cell, and there is a problem that peeling may occur between the two light absorption layers when the temperature change is repeated. In particular, in tandem solar cells having a light absorption layer (perovskite layer) using a perovskite compound, such as perovskite / silicon solar cells and perovskite / compound crystal solar cells, there is a tendency for a difference in the coefficient of thermal expansion to occur between the perovskite layer and other light absorption layers, and the adhesive strength between the layers constituting the cell (especially the adhesive strength of the perovskite layer and the adhesive strength of the self-assembled monolayer as a hole transport layer) tends to be weak, so this problem is significant.

[0005] Figure 6 is a cross-sectional view showing the schematic configuration of a conventional photoelectric conversion element 50 in a tandem solar cell. As shown in Figure 6, the photoelectric conversion element 50 has a stacked configuration of a top cell 51 and a bottom cell 52, with the top cell 51 on the top side and the bottom cell 52 on the back side. Here, the top cell 51 is a perovskite solar cell and the bottom cell 52 is a crystalline silicon solar cell.

[0006] The top cell 51 has, in order from the top side, a surface grid electrode 511, a surface transparent electrode 512, a top cell electron transport layer 513, a top cell light absorption layer 514, and a top cell hole transport layer 515. The bottom cell 52 has, in order from the top side, a bottom cell n-type doped layer 521, a bottom cell light absorption layer 522, a bottom cell p-type doped layer 523, a back surface transparent electrode 524, and a back surface grid electrode 525. An intermediate electrode (or intermediate layer) 53 is provided between the top cell 51 and the bottom cell 52, and the top cell 51 and the bottom cell 52 are connected in series by the intermediate electrode 53. Interconnectors 60 are connected to the top and back surfaces of the photoelectric conversion element 50.

[0007] Furthermore, when using expressions meaning "up" or "down" to describe direction, the expression "up" can be used to refer to the light-receiving side of the element, and the expression "down" can be used to refer to the back side of the element. Unless otherwise specified, this should be understood as such. In other words, the light-receiving side and the top side basically mean the same thing, and the back side and the bottom side also mean the same thing.

[0008] Furthermore, in the case of a single-sided light-receiving solar cell, the light-receiving surface refers directly to the surface on which light enters the element. In the case of a double-sided light-receiving solar cell, either one of the two surfaces can be considered the light-receiving surface, and if one surface is considered the light-receiving surface, the opposite surface can be considered the back surface. In other words, if the configuration of the disclosure is present when at least one of the surfaces is considered the light-receiving surface, it can be considered to fall within the technical scope of the disclosure. To put it another way, even if the configuration of the disclosure is not present when one of the surfaces is considered the light-receiving surface, if the configuration of the disclosure is present when the other surface is considered the light-receiving surface, it can be considered to fall within the technical scope of the disclosure.

[0009] In the photoelectric conversion element 50, shear stress is particularly likely to occur at the interface between the top cell light absorption layer 514 and the bottom cell 52. Due to this shear stress, delamination occurs in areas where the adhesive strength between the layers constituting the cell is low, and as temperature changes are repeated, the cell itself may be damaged. S′ shown in Figure 6 represents the region where shear stress is likely to occur (hereinafter referred to as the shear stress generation region), and the wider the shear stress generation region S′, the greater the shear stress and the more likely delamination is to occur.

[0010] This disclosure has been made in view of the above-mentioned problems, and aims to provide a photoelectric conversion element in a tandem solar cell that reduces the shear stress between the light absorption layer of the top cell and the light absorption layer of the bottom cell that occurs due to temperature changes, thereby suppressing delamination between the two light absorption layers. [Means for solving the problem]

[0011] To solve the above problems, the following photoelectric conversion element is provided. The photoelectric conversion element of the present disclosure is a photoelectric conversion element in a tandem solar cell, and includes a top cell disposed on the light-receiving surface side and a bottom cell disposed on the back side, characterized in that the light-absorbing layer of the top cell is divided into a plurality of regions by a void formed in the light-absorbing layer of the top cell. [Effects of the Invention]

[0012] The photoelectric conversion element disclosed herein offers excellent effects, such as reducing the shear stress between the light-absorbing layer of the top cell and the light-absorbing layer of the bottom cell that occurs due to temperature changes in a tandem solar cell, thereby suppressing delamination between the two light-absorbing layers. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing the schematic configuration of a photoelectric conversion element according to the first embodiment of this disclosure. [Figure 2] Figure 1 is a plan view showing a part of a photoelectric conversion module using the photoelectric conversion element. [Figure 3] This is a cross-sectional view showing the schematic configuration of a photoelectric conversion element according to the second embodiment of this disclosure. [Figure 4] This is a cross-sectional view showing the schematic configuration of a photoelectric conversion element according to the third embodiment of this disclosure. [Figure 5] This is a cross-sectional view showing the schematic configuration of a photoelectric conversion element according to the fourth embodiment of this disclosure. [Figure 6] This is a cross-sectional view showing the schematic configuration of a conventional photoelectric conversion element in a tandem solar cell. [Modes for carrying out the invention]

[0014] [First Embodiment] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Figure 1 shows one embodiment of the present disclosure and is a cross-sectional view showing the schematic configuration of the photoelectric conversion element 10.

[0015] In this disclosure, a tandem solar cell means a solar cell in which some or all of the light (more specifically, light having a certain wavelength band) incident from the light-receiving surface side of the photoelectric conversion element is sequentially absorbed by two or more light-absorbing layers.

[0016] Described in terms of the structure, in the present disclosure, a tandem solar cell may mean a solar cell in which two light absorption layers are provided in order from the light-receiving surface side to the back surface side of the photoelectric conversion element. Note that in the form seen from the light-receiving surface side, the two light absorption layers do not have to completely overlap, and it is sufficient if at least a part thereof overlaps. Also, it is desirable that at least one of the light absorption layers completely overlaps the other light absorption layer. That is, in the present disclosure, a tandem solar cell means that part or all of the light (specifically, light having a certain wavelength band) incident from the light-receiving surface side of the photoelectric conversion element can enter the other light absorption layer via one light absorption layer. Note that the light absorption layer here does not have to be a single layer and may be composed of a plurality of layers. The plurality of layers here can mean, for example, a stacked structure composed of a PN junction or the like.

[0017] Note that the light absorption layer is a layer that can absorb the light incident on the photoelectric conversion element and generate electrons and holes. The fact that the light absorption layer absorbs light and generates electrons and holes is self-evident as long as the solar cell functions as a solar cell, and as long as the light absorption layer is composed of an appropriate material, it is not necessary to confirm that it absorbs light that is very difficult to confirm and generates electron-hole pairs.

[0018] The photoelectric conversion element 10 is a photoelectric conversion element in a tandem solar cell using a perovskite solar cell. In FIG. 1, the upper surface side is the light-receiving surface. As shown in FIG. 1, the photoelectric conversion element 10 has a structure in which a top cell 11 and a bottom cell 12 are stacked, and the top cell 11 is disposed on the upper surface side and the bottom cell 12 is disposed on the back surface side.

[0019] The top cell 11 has, in order from the upper surface side, a surface grid electrode 111, a surface transparent electrode 112, a top cell electron transport layer 113, a top cell light absorption layer 114, and a top cell hole transport layer 115. The bottom cell 12 has, in order from the upper surface side, a bottom cell n-type doped layer 121, a bottom cell light absorption layer 122, a bottom cell p-type doped layer 123, a back surface transparent electrode 124, and a back surface grid electrode 125. Further, in the photoelectric conversion element 10, an intermediate electrode 13 is provided between the top cell 11 and the bottom cell 12, and the top cell 11 and the bottom cell 12 are connected in series by the intermediate electrode 13.

[0020] In the present embodiment, the top cell 11 is a perovskite solar cell, and the bottom cell 12 uses a crystalline silicon solar cell as a silicon-based solar cell. That is, the top cell light absorption layer 114 is a layer containing a perovskite compound that is a photoelectric conversion material, and may be composed of only the perovskite compound, or may contain substances other than the perovskite compound.

[0021] Furthermore, in a solar cell (or a photoelectric conversion module) using the photoelectric conversion element 10, a front surface interconnector 20A is connected to the upper surface of the photoelectric conversion element 10 (that is, the upper surface of the top cell 11), and a back surface interconnector 20B is connected to the back surface of the photoelectric conversion element 10 (that is, the lower surface of the bottom cell 12).

[0022] The photoelectric conversion element 10 shown in FIG. 1 can be manufactured by forming each layer required for the top cell 11 on the bottom cell 12. However, the manufacturing procedure of the photoelectric conversion element 10 of the present disclosure is not particularly limited. The photoelectric conversion element 10 may be manufactured by other methods, for example, by separately manufacturing the top cell 11 and the bottom cell 12 and then bonding these cells together.

[0023] The photoelectric conversion element 10 shown in Figure 1 illustrates a configuration in which current flows from top to bottom in the figure, but the direction of the current is not limited to this, and it may also be configured in which the current flows from bottom to top. In the configuration in which the current flows from bottom to top, the positions of the top cell electron transport layer 113 and the top cell hole transport layer 115 are swapped in the top cell 11, and the positions of the bottom cell n-type doped layer 121 and the bottom cell p-type doped layer 123 are swapped in the bottom cell 12. Furthermore, the type of doped layer in the bottom cell 12 (bottom cell n-type doped layer 121 or bottom cell p-type doped layer 123) is not particularly limited, and may be any of PERC (Passivated Emitter and Rear Cell) type, TOPCon (Tunnel Oxide Passivated Contact) type, or heterojunction type, and in addition to the doped layer, a PERC section, TOPCon section, or heterojunction section may also be provided.

[0024] As shown in Figure 1, in the photoelectric conversion element 10, the top cell light absorption layer 114 is divided into multiple regions. In this embodiment, the void portion 14 is formed as an opening groove that opens on the upper surface side of the top cell 11 and penetrates from the surface grid electrode 111 to the top cell hole transport layer 115, and the entire top cell 11 is divided into multiple regions by this opening groove. This void portion 14 as an opening groove can be formed by removing a part of the top cell 11 by a scribing method (laser scribing method or mechanical scribing method). Alternatively, a mask can be used when forming the top cell 11 so that the top cell 11 is not formed in the region that will become the void portion 14 from the beginning.

[0025] In other words, in the photoelectric conversion element 10, the interface on the bottom cell 12 side of the top cell light absorption layer 114 is divided into multiple regions. To put it another way, as shown in Figure 1, the shear stress generation region S in the photoelectric conversion element 10 is divided into multiple regions. Therefore, compared to the shear stress generation region S' in the conventional photoelectric conversion element 50 shown in Figure 6, the shear stress generated in each divided region of the shear stress generation region S is smaller. Consequently, the shear stress generated throughout the entire space between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 is reduced, and delamination between the two light absorption layers can be suppressed.

[0026] In this embodiment, the void portion 14 is formed as an opening groove that penetrates to the top cell hole transport layer 115. However, when forming the void portion 14 as an opening groove, it is sufficient that it penetrates at least from the upper surface of the top cell 11 to the top cell light absorption layer 114. Specifically, as illustrated later in the second embodiment, the void portion 14 as an opening groove may penetrate to the top cell light absorption layer 114, but not to the top cell hole transport layer 115. Furthermore, the void portion 14 may not be open to the upper surface of the top cell 11. Specifically, as illustrated later in the third embodiment, the void portion 14 may be configured to divide only the top cell light absorption layer 114 into multiple regions. The reason for this is that if the shear stress generation region S is divided into multiple regions, the generated shear stress can be reduced, and consequently, delamination between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 can be suppressed. Considering the ease of cell fabrication, it is preferable that the void portion 14 is formed as an opening groove that divides the entire top cell 11 into multiple regions, as in this embodiment.

[0027] Figure 2 is a plan view showing a part of a photoelectric conversion module 100 using photoelectric conversion elements 10. The photoelectric conversion module 100 has at least one row of photoelectric conversion strings in which multiple photoelectric conversion elements 10 are connected in series. Alternatively, the photoelectric conversion module 100 may be a photoelectric conversion array in which multiple rows of photoelectric conversion strings are connected in parallel. In Figure 2, two adjacent photoelectric conversion elements 10 in the photoelectric conversion string are shown separately, with the upper photoelectric conversion element 10 in the Y direction in the figure being referred to as the first element 10A, and the lower photoelectric conversion element 10 in the Y direction in the figure being referred to as the second element 10B. Note that the cross-sectional view in Figure 1 is a cross-sectional view of the photoelectric conversion element 10 shown in Figure 2, cut across plane AA.

[0028] The first element 10A and the second element 10B are electrically connected via an interconnector 20. The interconnector 20 is a connecting member in which a front interconnector 20A and a back interconnector 20B are integrally connected. In the interconnector 20 connecting the first element 10A and the second element 10B, the front interconnector 20A is connected to the front grid electrode 111 of the first element 10A, and the back interconnector 20B is connected to the back grid electrode 125 of the second element 10B. Note that while an interconnector is used as an example here, the term "connecting member" is not limited to interconnectors and broadly refers to any member capable of electrically connecting elements.

[0029] As shown in Figure 2, a substantially rectangular silicon wafer (for example, a substantially square silicon wafer cut in half) can be used for the bottom cell 12 in the photoelectric conversion element 10. The shape of the bottom cell 12 is not limited to this, but when the bottom cell 12 is substantially rectangular in this way, it is preferable that the void portion 14 is formed along a direction perpendicular to the long side of the bottom cell 12. In the state without the void portion 14, the long side of the bottom cell 12 is the long side of the shear stress generation region S, so by dividing the shear stress generation region S along a direction perpendicular to its long side, the shear stress generated by temperature changes, etc., can be effectively reduced. Consequently, delamination between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 can be suppressed.

[0030] As shown in Figure 2, the voids 14 are formed along a direction parallel to the interconnectors 20. That is, all the voids 14 in the photoelectric conversion element 10 are formed to be parallel. Figure 2 illustrates a configuration in which the photoelectric conversion element 10 is provided with voids 14 as two opening grooves, but the number of voids 14 is not particularly limited. Similarly, the number of interconnectors 20 is not particularly limited. For example, if voids 14 are provided so that the top cell light absorption layer 114 is divided between all adjacent interconnectors 20, then if the number of interconnectors 20 on the top cell 11 is n, then n-1 voids 14 should be formed along a direction parallel to the interconnectors 20.

[0031] By forming the void portion 14 along a direction parallel to the interconnector 20, the region without the top cell light absorption layer 114 and the region where the interconnector 20 is located do not overlap. This prevents the interconnector 20 from hindering the collection of current from the cell by the void portion 14, and consequently minimizes the impact of the void portion 14 on the battery characteristics.

[0032] Furthermore, by forming the void portion 14 along a direction parallel to the interconnector 20, it is possible to effectively provide a region on the bottom cell 12 where there is no top cell light absorption layer 114 and where light can be received, which has the advantage of not reducing the current collection efficiency of the interconnector 20.

[0033] In the top cell 11 of the photoelectric conversion element 10, at least one interconnector 20 is connected to each of the divided regions. In this embodiment, one interconnector 20 is connected to one divided region of the top cell 11 (i.e., one divided region of the top cell light absorption layer 114), but two or more interconnectors 20 may be connected to one divided region. In other words, instead of providing gaps 14 so that the top cell light absorption layer 114 is divided between all adjacent interconnectors 20, gaps 14 may be provided so that the top cell light absorption layer 114 is divided between every other or every two adjacent interconnectors 20.

[0034] In this embodiment, an intermediate electrode 13 is provided on the bottom cell 12. However, as a modification of this embodiment, a configuration in which the intermediate electrode 13 is not provided between the top cell 11 and the bottom cell 12 (a configuration in which the top cell 11 and the bottom cell 12 are directly joined) can be included.

[0035] In the following description, the configuration of each layer in the photoelectric conversion element 10 will be explained using examples. However, since known technologies can be applied to the materials and film deposition methods of each layer in the photoelectric conversion element 10, the configuration of each layer applicable to this embodiment is not limited to these examples. That is, as long as it functions as a photoelectric conversion element in a tandem solar cell, any optional layers may be omitted, and there may be layers other than those described below, and one layer may also perform the function of another layer.

[0036] (Front grid electrode, back grid electrode) The surface grid electrode 111 and the back grid electrode 125 are composed of multiple conductive members that are parallel to each other. These multiple conductive members extend in a first direction (the X direction shown in Figures 1 and 2) and are arranged parallel to each other with spacing between them in a second direction (the Y direction shown in Figures 1 and 2). The multiple conductive members in the surface grid electrode 111 (back grid electrode 125) are connected by an interconnector 20 or a grid electrode located below the interconnector 20. Specifically, the interconnector 20 extends in the second direction and is arranged to be perpendicular to these multiple conductive members. Since the second direction is along the short side of the photoelectric conversion element 10, arranging the interconnector 20 to extend in this direction can reduce its electrical resistance.

[0037] The front grid electrode 111 (back grid electrode 125) is also called a finger electrode, and the interconnector 20 is also called a busbar electrode. The material of the conductive member is not particularly limited, but examples include metals such as silver, copper, and aluminum. The conductive member in the front grid electrode 111 (back grid electrode 125) is narrower than the interconnector 20, and light is incident into the interior of the photoelectric conversion element 10 through the gap between adjacent conductive members. Note that the back grid electrode 125 is on the opposite side from the light-receiving surface, so it may be configured so that light does not pass through it.

[0038] (Surface transparent electrode, back transparent electrode) The front transparent electrode 112 and the back transparent electrode 124 are thin-film electrodes that are conductive and light-transmitting. Examples of materials for these electrodes include conductive transparent materials such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). These may be used individually or in combination of two or more. The back transparent electrode 124 is on the opposite side from the light-receiving surface, so it may be configured not to be light-transmitting.

[0039] (Top cell electron transport layer) The top cell electron transport layer 113 is a layer that transports electrons generated in the top cell light absorption layer 114 to the surface transparent electrode 112. Preferably, the top cell electron transport layer 113 also functions as a hole blocking layer that suppresses the movement of holes generated in the top cell light absorption layer 114 to the surface transparent electrode 112. Examples of materials for the top cell electron transport layer 113 include tin oxide, titanium oxide, and zinc oxide.

[0040] Furthermore, as long as the top cell 11 has a photoelectric conversion function, it is self-evident that the portion located on the electron transport side (or negative electrode side, similarly in this disclosure) of the top cell light absorption layer 114 or on the electron transport side within the top cell light absorption layer 114 has an electron transport function, and there is no need to verify the electron transport function, which is difficult to actually confirm. In other words, as long as the top cell 11 has a photoelectric conversion function, any layer located on the electron transport side of the top cell light absorption layer 114 or on the electron transport side within the top cell light absorption layer 114 and made of an appropriate material can be considered the top cell electron transport layer 113.

[0041] Furthermore, the top cell electron transport layer 113 can also function as the surface transparent electrode 112, and vice versa. Therefore, the photoelectric conversion element 10 does not necessarily have to be configured to include both the surface transparent electrode 112 and the top cell electron transport layer 113; it may be configured to include only one of them, with one of them performing the function of the other.

[0042] (Top cell light absorption layer) The top cell light absorption layer 114 can be a layer containing a perovskite compound, which is a photoelectric conversion material. The top cell light absorption layer 114 is a layer that absorbs at least a portion of the light incident on the photoelectric conversion element 10 and can generate electrons and holes. Of these, electrons move to the top cell electron transport layer 113, and holes move to the top cell hole transport layer 115. The top cell light absorption layer 114 may consist of a perovskite compound alone, or it may contain substances other than perovskite compounds.

[0043] The perovskite compound is composed of compounds represented by the general formula: ABX3···(1). While the compositional ratio is preferably 1:1:3, it does not necessarily have to be 1:1:3, and the content of each element may be adjusted as appropriate.

[0044] In general formula (1), A is an organic molecule (including an organic group or an organic cation, as is the case in this disclosure), an inorganic atom or molecule (including an inorganic group or an inorganic cation, as is the case in this disclosure), or a combination thereof; B is a metal atom or molecule (including a metal cation, as is the case in this disclosure); and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion, as is the case in this disclosure). In general formula (1), the three Xs may be the same or different from one another.

[0045] In general formula (1), the organic molecule represented by A is preferably a molecule containing carbon, nitrogen, and hydrogen, and the inorganic atom represented by A is preferably cesium or rubidium.

[0046] Furthermore, it is possible to determine that a compound is a perovskite compound if it is known that the top cell light-absorbing layer 114 has a photoelectric conversion function and contains A, B, and X; confirmation of the presence of a crystalline structure is not required. For example, it is possible to determine this by knowing that A, B, and X contain organic molecules, metal atoms, and halogen atoms, or by knowing that A, B, and X contain inorganic atoms, metal atoms, and halogen atoms.

[0047] Examples of organic molecules represented by A in general formula (1) include alkylamines, alkylammonium compounds, and nitrogen-containing heterocyclic compounds. In perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or it may be two or more types of organic molecules.

[0048] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0049] Alkylammonium compounds are ionized compounds of the alkylamines mentioned above. Examples of alkylammonium compounds include methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, dipentylammonium, dihexylammonium, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexylammonium, ethylmethylammonium, methylpropylammonium, butylmethylammonium, methylpentylammonium, hexylmethylammonium, ethylpropylammonium, and ethylbutylammonium.

[0050] Examples of nitrogen-containing heterocyclic compounds include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. Nitrogen-containing heterocyclic compounds may also be ionized. Phenethylammonium is preferred as an ionized nitrogen-containing heterocyclic compound.

[0051] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium, or propylammonium, and even more preferably methylammonium.

[0052] In general formula (1), examples of metal atoms represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In perovskite compounds, the metal atom represented by B may be only one type of metal atom or two or more types of metal atoms. From the viewpoint of improving the light absorption and charge generation characteristics of perovskite compounds, lead atoms or tin atoms are preferred as the metal atom represented by B. From the viewpoint of reducing lead, tin atoms are preferred.

[0053] Examples of halogen atoms represented by X in general formula (1) include fluorine, chlorine, bromine, and iodine atoms. Examples of chalcogen atoms include oxygen, sulfur, selenium, and tellurium atoms. In a perovskite compound, the halogen atom or chalcogen atom represented by X may be one or two or more. From the viewpoint of enabling the perovskite compound to utilize light in a wide wavelength range, iodine is preferred as the halogen atom represented by X. More specifically, it is preferable that at least one of the three Xs represents an iodine atom, and it is more preferable that all three Xs represent iodine atoms.

[0054] As the perovskite compound, compounds represented by the general formula "CH3NH3PbX3 (where X represents a halogen atom)" are preferred, and CH3NH3PbI3 is more preferred. By using a compound represented by the general formula "CH3NH3PbX3" (especially CH3NH3PbI3) as the perovskite compound, electrons and holes can be generated more efficiently in the perovskite compound, and as a result, the photoelectric conversion efficiency of solar cells can be further improved.

[0055] As a method for forming the top cell light-absorbing layer 114 containing the perovskite compound, an example is to coat a precursor solution, obtained by dissolving a precursor compound of the perovskite compound in an organic solvent, using known methods such as spin coating or bar coating to form the film.

[0056] (Top cell hole transport layer) The top cell hole transport layer 115 is a layer that transports holes generated in the top cell light absorption layer 114 to the intermediate electrode 13. Preferably, the top cell hole transport layer 115 also functions as an electron blocking layer that suppresses the movement of electrons generated in the top cell light absorption layer 114 to the intermediate electrode 13.

[0057] The top cell hole transport layer 115 is composed mainly of a hole transport material. Specifically, the top cell hole transport layer 115 preferably contains 70% by mass or more of the hole transport material, and more preferably contains 85% by mass or more and 100% by mass or less. Examples of hole transport materials include P-type organic semiconductors, conductive polymers, metal oxides, metal sulfides (e.g., Cu2O, NiO, ZnS), and spiro-OMeTAD is preferred.

[0058] Furthermore, as long as the top cell 11 has a photoelectric conversion function, it is self-evident that the portion located on the hole transport side (or positive electrode side, similarly in this disclosure) of the top cell light absorption layer 114 or on the hole transport side within the top cell light absorption layer 114 has a hole transport function, and there is no need to verify the hole transport function, which is difficult to actually confirm. In other words, as long as the top cell 11 has a photoelectric conversion function, any layer located on the hole transport side of the top cell light absorption layer 114 or on the hole transport side within the top cell light absorption layer 114 and made of an appropriate material can be considered as the top cell hole transport layer 115.

[0059] (Middle class) In this embodiment, an intermediate electrode 13 is exemplified as an intermediate layer. The intermediate electrode 13 is an electrode that electrically connects the top cell and the bottom cell, and is configured so that light not absorbed by the top cell 11 can reach the bottom cell 12. That is, the material of the intermediate electrode 13 can be a material that has conductivity and light transmittance, and examples of conductive transparent materials include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). These may be used individually or in combination of two or more.

[0060] Furthermore, the intermediate layer is not limited to the intermediate electrode 13, but can also be any other known structure placed between the tandem top cell and bottom cell, such as a highly doped impurity-doped layer, a highly doped PN junction layer, or a tunnel junction layer.

[0061] The intermediate layer can be any structure placed between the top cell and the bottom cell in a tandem solar cell. As long as the solar cell is functioning as a solar cell, it is self-evident that such a structure functions as an intermediate layer without needing to verify its physical properties such as conductivity and transmittance. Furthermore, an intermediate layer is not necessarily required; the layer on the bottom cell side of the top cell and the layer on the top cell side of the bottom cell can serve as a substitute, having a similar configuration. As long as the tandem solar cell containing these top and bottom cells is functioning as a tandem solar cell, it is self-evident that these layers function as a substitute for the intermediate layer without needing to verify their physical properties such as conductivity and transmittance.

[0062] (Bottom cell n-type doped layer, bottom cell light absorption layer, bottom cell p-type doped layer) The bottom cell n-type doped layer 121, the bottom cell light-absorbing layer 122, and the bottom cell p-type doped layer 123 can employ configurations used in known silicon solar cells. For example, by adding doping impurities to the surface of a crystalline silicon substrate, a configuration can be achieved in which the bottom cell n-type doped layer 121 is formed on one side of the bottom cell light-absorbing layer 122, which is a crystalline silicon substrate, and the bottom cell p-type doped layer 123 is formed on the other side. The bottom cell n-type doped layer 121 can be formed by adding phosphorus, arsenic, etc., as doping impurities, and the bottom cell p-type doped layer 123 can be formed by adding boron, gallium, etc.

[0063] Furthermore, when using a heterojunction silicon configuration, for example, a non-single-crystal silicon-based thin film, such as amorphous silicon or microcrystalline silicon, can be deposited on a single-crystal silicon substrate as the bottom cell light absorption layer 122, forming the bottom cell n-type doping layer 121 and the bottom cell p-type doping layer 123. Examples of materials for the silicon-based thin film as the bottom cell n-type doping layer 121 and the bottom cell p-type doping layer 123 include amorphous silicon, microcrystalline silicon, amorphous silicon alloy, and microcrystalline silicon alloy. Examples of silicon alloys include silicon oxide, silicon carbide, silicon nitride, and silicon germanium. These may be used individually or in combination of two or more.

[0064] [Second Embodiment] Figure 3 is a cross-sectional view showing the schematic configuration of a photoelectric conversion element 10 according to the second embodiment of this disclosure. In the photoelectric conversion element 10 according to this embodiment, the configuration can be the same as that of the first embodiment, except as described below.

[0065] In the photoelectric conversion element 10 according to this embodiment, the void portion 14, which serves as an opening groove opening on the upper surface side of the top cell 11, penetrates to the top cell light absorption layer 114 but does not penetrate the top cell hole transport layer 115. Even with this configuration, since the top cell light absorption layer 114 is divided into multiple regions by the void portion 14, the shear stress generated between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 is reduced, and delamination between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 can be suppressed.

[0066] [Third Embodiment] Figure 4 is a cross-sectional view showing the schematic configuration of a photoelectric conversion element 10 according to the third embodiment of this disclosure. In the photoelectric conversion element 10 according to this embodiment, the configuration can be the same as that of the first embodiment, except as described below.

[0067] In the photoelectric conversion element 10 according to this embodiment, the void portion 14 is formed as a void located inside the top cell 11, and in this example, only the top cell light absorption layer 114 is divided into multiple regions. This void portion 14 can be formed by using a mask when forming the top cell light absorption layer 114, so that the top cell light absorption layer 114 is not formed in the region that will become the void portion 14 from the beginning. Alternatively, it may be formed by removing the layer from the upper surface of the top cell 11 up to the top cell light absorption layer 114 by a scribing method (laser scribing method or mechanical scribing method), and then refilling the layers other than the top cell light absorption layer 114.

[0068] Even with this configuration, the top cell light absorption layer 114 is divided into multiple regions by the void 14, which reduces the shear stress generated between the top cell light absorption layer 114 and the bottom cell light absorption layer 122, thereby suppressing delamination between the top cell light absorption layer 114 and the bottom cell light absorption layer 122.

[0069] [Fourth Embodiment] Figure 5 is a cross-sectional view showing the schematic configuration of a photoelectric conversion element 10 according to the fourth embodiment of this disclosure. In the first to third embodiments, a two-junction type photoelectric conversion element 10 with two types of light-absorbing layers stacked on top of each other was shown, but in this embodiment, a three-junction type photoelectric conversion element 10 with three types of light-absorbing layers stacked on top of each other is shown. In this disclosure, a two-junction type refers to a tandem solar cell in which there are two light-absorbing layers capable of sequentially absorbing light, and the description of the configuration of the light-absorbing layers can be applied to the description of a tandem solar cell. Similarly, a three-junction type refers to a tandem solar cell in which there are three light-absorbing layers capable of sequentially absorbing light, and the description of the configuration of the light-absorbing layers can be applied to the description of a tandem solar cell. Note that the term "junction" here does not mean a literal "junction," but is a conventional expression used to represent the number of light-absorbing layers in a tandem solar cell, so in substance, "junction" can be understood as "light-absorbing layer."

[0070] The photoelectric conversion element 10 in Figure 5 has a configuration in which a middle cell 15 is stacked in addition to the top cell 11 and bottom cell 12. Specifically, the top cell 11 is located on the upper side, the bottom cell 12 is located on the back side, and the middle cell 15 is located between the top cell 11 and the bottom cell 12. The configuration of the top cell 11 and bottom cell 12 in this embodiment can be the same as the configuration of the top cell 11 and bottom cell 12 in the first to third embodiments. Furthermore, as an intermediate layer, an intermediate electrode 131 is provided between the top cell 11 and the middle cell 15, and an intermediate electrode 132 is provided between the middle cell 15 and the bottom cell 12. The intermediate electrodes 131 and 132 can be the same as the intermediate layer or intermediate electrode 13 in the first to third embodiments.

[0071] The middle cell 15 has, in order from the top side, a middle cell electron transport layer 151, a middle cell light absorption layer 152, and a middle cell hole transport layer 153. The middle cell 15 is a perovskite solar cell, just like the top cell 11, but it is preferable that at least some of the materials differ from those of the top cell 11, and that the wavelength of the light that is photoelectrically converted differs from that of the top cell 11. More specifically, it is preferable that the wavelength bands of light that can be absorbed by the top cell light absorption layer 114 and the middle cell light absorption layer 152 are offset. In particular, if the wavelength band of light that can be absorbed by the middle cell light absorption layer 152 is on the longer wavelength side compared to the wavelength band of light that can be absorbed by the top cell light absorption layer 114, the photoelectric conversion efficiency of the device can be made more efficient.

[0072] In the photoelectric conversion element 10 according to this embodiment, a void portion 14 is formed as an opening groove that opens on the upper surface side of the top cell 11 and penetrates from the surface grid electrode 111 in the top cell 11 to the middle cell hole transport layer 153 in the middle cell 15. That is, in addition to the top cell light absorption layer 114, the middle cell light absorption layer 152 is also divided into multiple regions, and the divided regions of the top cell light absorption layer 114 and the divided regions of the middle cell light absorption layer 152 correspond to each other.

[0073] In the photoelectric conversion element 10 according to this embodiment, the number of divided regions is the same in the top cell light absorption layer 114 and the middle cell light absorption layer 152, and the arrangement direction of the divided regions is the same in the top cell light absorption layer 114 and the middle cell light absorption layer 152. In this case, divided regions in the top cell light absorption layer 114 and the middle cell light absorption layer 152 that have the same arrangement order along the arrangement direction are considered to be corresponding divided regions. It is sufficient that the corresponding divided regions overlap in at least a portion of their regions in a plan view, in which case it can be said that "the divided regions of the top cell light absorption layer 114 and the divided regions of the middle cell light absorption layer 152 correspond to each other." It is preferable that the corresponding divided regions completely overlap in a plan view.

[0074] If a void 14 is formed as an opening groove that opens to the upper surface of the top cell 11 and penetrates at least to the middle cell light absorption layer 152, as in the photoelectric conversion element 10 according to this embodiment, then corresponding divided regions will inevitably overlap in at least a portion of their regions in a plan view. Furthermore, if the void 14 as an opening groove is formed along a direction perpendicular to the upper surface of the top cell 11 (i.e., the Z direction shown in Figure 5), then it can be said that corresponding divided regions will completely overlap in a plan view.

[0075] In this type of three-junction photoelectric conversion element 10, the top cell light absorption layer 114 and the middle cell light absorption layer 152 are each divided into multiple regions by the void portion 14, thereby suppressing delamination between the top cell light absorption layer 114 and the bottom cell light absorption layer 122 (for example, at the interface of the top cell light absorption layer 114 on the middle cell 15 side, or at the interface of the middle cell light absorption layer 152 on the bottom cell 12 side).

[0076] This embodiment is an example of applying the two-junction type photoelectric conversion element 10 according to the first embodiment to a three-junction type. However, as a modification of this embodiment, examples of applying the two-junction type photoelectric conversion element 10 according to the second and third embodiments to a three-junction type can be included. That is, the void portion 14 as an opening groove opening on the upper surface side of the top cell 11 may penetrate to the middle cell light absorption layer 152, but not to the middle cell hole transport layer 153. Alternatively, the void portion 14 may be provided not as an opening groove, but as a void located inside the top cell 11 and the middle cell 15.

[0077] The embodiments disclosed herein are illustrative in all respects and are not intended to be restrictive. Therefore, the technical scope of this disclosure is not construed solely by the embodiments described above, but is defined by the claims. This includes all modifications within the meaning and scope of the claims.

[0078] [Note] This disclosure includes the following aspects:

[0079] (Aspect 1) A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving side and a bottom cell located on the back side, A photoelectric conversion element characterized in that the light absorption layer of the top cell is divided into multiple regions by voids formed in the light absorption layer of the top cell.

[0080] (Aspect 2) A photoelectric conversion element according to Aspect 1, The photoelectric conversion element is characterized in that the void portion is formed along a direction perpendicular to the long side of the bottom cell.

[0081] (Aspect 3) A photoelectric conversion element according to Aspect 1 or Aspect 2, The top cell has grid electrodes composed of a plurality of conductive members parallel to each other, An interconnector for connecting the plurality of conductive members in the grid electrode is provided on the top cell. The photoelectric conversion element is characterized in that the gap portion is formed along a direction parallel to the interconnector.

[0082] (Aspect 4) A photoelectric conversion element according to any one of aspects 1 to 3, The photoelectric conversion element is characterized in that the void portion is formed as a groove that penetrates at least from the upper surface side of the top cell to the light absorption layer of the top cell.

[0083] (Aspect 5) A photoelectric conversion element according to any one of aspects 1 to 4, The photoelectric conversion element is characterized in that the light-absorbing layer of the top cell contains a perovskite compound.

[0084] (Aspect 6) A photoelectric conversion element according to any one of aspects 1 to 5, It includes a middle cell positioned between the top cell and the bottom cell, The light absorption layer of the middle cell is divided into multiple regions, A photoelectric conversion element characterized in that the divided region of the light absorption layer of the top cell and the divided region of the light absorption layer of the middle cell correspond to each other. [Explanation of symbols]

[0085] 10 Photoelectric conversion element 100 Photoelectric Conversion Modules 11 Top Cells 111 Surface grid electrode 112 Surface transparent electrode 113 Top cell electron transport layer 114 Top cell light absorption layer 115 Top cell hole transport layer 12 bottom cells 121 Bottom cell n-type doped layer 122 Bottom cell light absorption layer 123 Bottom cell p-type doped layer 124 Back side transparent electrode 125 Backside grid electrode 13 Intermediate electrode 14 Cavity 15 Middle Cells 151 Middle cell electron transport layer 152 Middle cell light absorption layer 153 Middle cell hole transport layer 20 interconnectors 20A Surface Interconnector 20B Rear Interconnector

Claims

1. A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving side and a bottom cell located on the back side, The light absorption layer of the top cell is divided into multiple regions by the voids formed in the light absorption layer of the top cell. The top cell has grid electrodes composed of a plurality of conductive members parallel to each other, An interconnector for connecting the plurality of conductive members in the grid electrode is provided on the top cell. The photoelectric conversion element is characterized in that the gap portion is formed along a direction parallel to the interconnector.

2. A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving side and a bottom cell located on the back side, The light absorption layer of the top cell is divided into multiple regions by the voids formed in the light absorption layer of the top cell. The top cell has a hole transport layer located on the back side of the light absorption layer of the top cell, The photoelectric conversion element is characterized in that the void portion is formed as a groove opening on the light-receiving surface side of the top cell, penetrates to the light-absorbing layer of the top cell, but does not penetrate the hole transport layer.

3. A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving side and a bottom cell located on the back side, The light absorption layer of the top cell is divided into multiple regions by the voids formed in the light absorption layer of the top cell. The top cell has a surface transparent electrode located on the light-receiving surface side of the light-absorbing layer of the top cell, A photoelectric conversion element characterized in that at least the surface-transparent electrode is located on the light-receiving surface side of the void, so that the void is located inside the top cell.

4. A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving side and a bottom cell located on the back side, The light absorption layer of the top cell is divided into multiple regions by the voids formed in the light absorption layer of the top cell. It includes a middle cell positioned between the top cell and the bottom cell, The light absorption layer of the middle cell is divided into multiple regions, A photoelectric conversion element characterized in that the divided region of the light absorption layer of the top cell and the divided region of the light absorption layer of the middle cell correspond to each other.

5. A photoelectric conversion element according to any one of claims 1 to 4, The photoelectric conversion element is characterized in that the void portion is formed along a direction perpendicular to the long side of the bottom cell.

6. A photoelectric conversion element according to any one of claims 2 to 4, The top cell has grid electrodes composed of a plurality of conductive members parallel to each other, An interconnector for connecting the plurality of conductive members in the grid electrode is provided on the top cell. The photoelectric conversion element is characterized in that the gap portion is formed along a direction parallel to the interconnector.

7. A photoelectric conversion element according to Claim 1, The photoelectric conversion element is characterized in that the void portion is formed as a groove that penetrates at least from the upper surface side of the top cell to the light absorption layer of the top cell.

8. A photoelectric conversion element according to any one of claims 1 to 4, The photoelectric conversion element is characterized in that the light-absorbing layer of the top cell contains a perovskite compound.

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