Photoelectric conversion element and photoelectric conversion module

Abstract

A photoelectric conversion element and a photoelectric conversion module capable of suppressing current concentration within a cell in a tandem solar cell are provided. [Solution] A photoelectric conversion element 10 in a tandem solar cell includes a top cell 11 arranged on the light-receiving surface side and a bottom cell 12 arranged on the back side, and the electrode layer on the top side of the top cell 11 (front grid electrode 111 and front transparent electrode 112) and the electrode layer on the back side of the bottom cell 12 (back transparent electrode 124 and back grid electrode 125) are divided into multiple regions. The divided regions in the top electrode layer correspond to the divided regions in the back electrode layer.

Description

[Technical Field]

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

[0002] Tandem solar cells have been proposed in which different types of light absorption layers (or photoelectric conversion layers) are stacked to increase the power generation efficiency of solar cells. One example of a tandem solar cell is a perovskite / silicon thin-film solar cell (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-910 Summary of the Invention [Problem to be solved by the invention]

[0004] In tandem solar cells that have a photoelectric conversion layer (perovskite layer) using perovskite compounds, such as perovskite / silicon thin-film solar cells, current concentration can occur within the cell due to partial short circuits (point defects).

[0005] Fig. 5 is a cross-sectional view showing the schematic configuration of a conventional photoelectric conversion element 50 having a tandem structure. As shown in Fig. 5, the photoelectric conversion element 50 has a configuration in which a top cell 51 and a bottom cell 52 are stacked, with the top cell 51 disposed on the upper surface side and the bottom cell 52 disposed on the lower surface 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 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. An interconnector 60 is connected to the top and back surfaces of the photoelectric conversion element 50.

[0007] 6 is a diagram illustrating the principle of current concentration in a cell due to a short circuit. In the photoelectric conversion element 50 of FIG. 6, it is assumed that a short circuit occurs at one location in the top cell light absorption layer 514.

[0008] When the top cell 51 is a thin-film solar cell, each layer is thin, and therefore, a short circuit may occur inside the cell due to uneven film thickness or the inclusion of foreign matter. If a short circuit occurs anywhere inside the top cell 51, an in-plane current is generated toward the short circuit in the electrode layers of the photoelectric conversion element 50 (the front grid electrode 511, the front transparent electrode 512, the back transparent electrode 524, and the back grid electrode 525), and as a result, current flows concentratedly at the short-circuited location inside the cell.

[0009] In addition to the above-mentioned short circuit, current concentration within the cell can also occur due to an imbalance in photocurrent between the top and bottom due to the tandem structure, the influence of a shadow on the solar cell, and so on.

[0010] For example, when the photoelectric conversion element 50 operates under conditions in which the photocurrent of the bottom cell 52 is significantly greater than the photocurrent of the top cell 51, a reverse voltage is applied to the top cell 51. If the top cell 51 is a perovskite solar cell or the like, the reverse voltage resistance of the top cell 51 is low and varies within the plane, resulting in a phenomenon in which current concentrates in the part with the lowest reverse voltage resistance.

[0011] Furthermore, in a photoelectric conversion module in which multiple photoelectric conversion elements 50 are connected in series, if one photoelectric conversion element 50 is shaded, leaving only a portion of the element, current will flow into the shaded element from other elements connected before and after it that are not shaded. In this case, current will concentrate in the unshaded, operating parts of the shaded element.

[0012] When current concentration occurs, it causes degradation of the cell and heat generation in the current-concentrated area, resulting in reduced reliability and performance. This problem is particularly pronounced in perovskite solar cells. For this reason, it is necessary to suppress current concentration within the cell.

[0013] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a photoelectric conversion element and a photoelectric conversion module that can suppress current concentration within a cell in a tandem solar cell. [Means for solving the problem]

[0014] In order to solve the above problems, the following photoelectric conversion element and photoelectric conversion module are provided.

[0015] (1) Photoelectric conversion element The photoelectric conversion element disclosed herein is a photoelectric conversion element in a tandem solar cell, and includes a top cell arranged on the light-receiving surface side and a bottom cell arranged on the back surface side, wherein an electrode layer on the top surface side of the top cell and an electrode layer on the back surface side of the bottom cell are divided into a plurality of regions, and the divided regions in the electrode layer on the top surface side correspond to the divided regions in the electrode layer on the back surface side.

[0016] (2) Photoelectric conversion module The photoelectric conversion module disclosed herein is a photoelectric conversion module having a photoelectric conversion string in which a plurality of the photoelectric conversion elements described above are connected in series, wherein two adjacent photoelectric conversion elements in the photoelectric conversion string are electrically connected via a connecting member, and at least one connecting member is provided in each of the divided areas of the upper electrode layer and the lower electrode layer of the photoelectric conversion element. [Effects of the Invention]

[0017] In the photoelectric conversion element and photoelectric conversion module of the present disclosure, the electrode layers on the upper and rear surfaces are divided into a plurality of regions, thereby making it possible to suppress current concentration within the cell. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a first embodiment of the present disclosure. [Figure 2] FIG. 1 is a plan view showing a part of a photoelectric conversion module using a photoelectric conversion element. [Figure 3] FIG. 10 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a third embodiment. [Figure 5] FIG. 1 is a cross-sectional view showing a schematic configuration of a conventional photoelectric conversion element having a tandem structure. [Figure 6] 1A and 1B are diagrams illustrating the principle of current concentration occurring in a cell due to a short circuit. DETAILED DESCRIPTION OF THE INVENTION

[0019] [First embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Fig. 1 shows an embodiment of the present disclosure and is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element 10. As shown in Figs.

[0020] The photoelectric conversion element 10 is a photoelectric conversion element in a tandem solar cell using a perovskite solar cell, and in FIG. 1, the top surface side is the light-receiving surface. As shown in FIG. 1, the photoelectric conversion element 10 has a configuration in which a top cell 11 and a bottom cell 12 are stacked, with the top cell 11 disposed on the top surface side and the bottom cell 12 disposed on the back surface side. In this disclosure, when simply referring to the light-receiving surface side, it means the light-receiving surface side or the side mainly used as the light-receiving surface. Similarly, when simply referring to the back surface side, it means the back surface side or the side mainly used as the back surface.

[0021] In addition, when an expression meaning "up" or "down" is used to describe a direction, it can refer to the light-receiving surface side of the element and the back side of the element, and it will be understood in this way unless otherwise specified. Similarly, the light-receiving surface side can refer to the top side, and the back side can refer to the bottom side.

[0022] Furthermore, in a monofacial solar cell, the light-receiving surface refers to the surface on which light is directly incident into the element. However, in a bifacial solar cell, either one of the surfaces can be considered the light-receiving surface. In this case, when either one of the surfaces is considered as the light-receiving surface, the surface opposite to that surface can be considered as the back surface. Furthermore, if at least one of the surfaces is considered as the light-receiving surface, the configuration of the present disclosure can be considered to be used. In other words, even if the configuration of the present disclosure is not used when one of the surfaces is considered as the light-receiving surface, the configuration of the present disclosure can be considered to be used as long as the configuration of the present disclosure is used when the other surface is considered as the light-receiving surface.

[0023] In the present disclosure, a tandem solar cell refers to a solar cell configured such that light (specifically, light having a certain wavelength band) incident from the light-receiving surface side of a photoelectric conversion element can be partially or entirely absorbed by two or more light-absorbing layers. Alternatively, in the present disclosure, a tandem solar cell may refer to a solar cell configured such that two light-absorbing layers are provided in sequence from the light-receiving surface side to the back side of a photoelectric conversion element as viewed from the light-receiving surface side. The two light-absorbing layers do not necessarily overlap completely as viewed from the light-receiving surface side, as long as they overlap at least partially. It is also desirable for at least one light-absorbing layer to completely overlap the other light-absorbing layer. Alternatively, in the present disclosure, a tandem solar cell refers to a solar cell configured such that light (specifically, light having a certain wavelength band) incident from the light-receiving surface side of a photoelectric conversion element can partially or entirely pass through one light-absorbing layer and enter the other light-absorbing layer. The light absorbing layer does not have to be a single layer, but may be made up of multiple layers, where multiple layers can mean, for example, a stacked structure made up of a PN junction.

[0024] The light absorbing layer is a layer that can absorb light incident on a photoelectric conversion element and generate electrons and holes. It is self-evident that the light absorbing layer absorbs light and generates electrons and holes as long as the solar cell functions as a solar cell, and so as long as the light absorbing layer is made of an appropriate material, there is no need to confirm that it absorbs light and generates electron-hole pairs, which is very difficult to confirm.

[0025] The top cell 11 has, in order from the top 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 top 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. In addition, in the photoelectric conversion element 10, an intermediate electrode 13 is provided as an intermediate layer 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.

[0026] In this embodiment, the top cell 11 is a perovskite solar cell, and the bottom cell 12 is a silicon-based solar cell that is a crystalline silicon solar cell. That is, the top cell light absorbing layer 114 is a layer containing a perovskite compound, which is a photoelectric conversion material, and may be composed of a perovskite compound alone, or may contain a substance other than a perovskite compound.

[0027] Furthermore, in a solar cell (or photoelectric conversion module) using the photoelectric conversion element 10, a surface interconnector 20A is connected to the upper surface of the photoelectric conversion element 10 (i.e., 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 (i.e., the lower surface of the bottom cell 12).

[0028] 1 can be fabricated by forming each layer required for the top cell 11 on the bottom cell 12. However, the fabrication procedure for the photoelectric conversion element 10 of the present disclosure is not particularly limited. The photoelectric conversion element 10 may also be fabricated by other methods, such as fabricating the top cell 11 and the bottom cell 12 separately and then bonding these cells together.

[0029] In the following, the configuration of each layer in the photoelectric conversion element 10 will be described as an example, but known techniques can be applied to the materials and film formation methods of each layer in the photoelectric conversion element 10, and therefore the configuration of each layer that can be applied to this embodiment is not limited to this example. In other words, as long as the function of a photoelectric conversion element in a tandem solar cell is maintained, optional layers may be omitted, layers other than those described below may be included, and one layer may also serve the function of another layer.

[0030] (Front grid electrode, rear grid electrode) The front grid electrode 111 and the rear grid electrode 125 are composed of a plurality of conductive members that are parallel to one another. These conductive members extend in a first direction (the X direction shown in FIG. 2 ) and are arranged parallel to one another at intervals in a second direction (the Y direction shown in FIG. 2 ). The conductive members in the front grid electrode 111 (rear grid electrode 125) are connected by the interconnector 20 or a grid electrode arranged below the interconnector. Specifically, the interconnector 20 extends in the second direction and is arranged perpendicular to the conductive members. Because the second direction is a direction along the short sides of the photoelectric conversion element 10, the electrical resistance of the interconnector 20 can be reduced by arranging the interconnector 20 to extend in this direction.

[0031] The front surface grid electrode 111 (rear surface grid electrode 125) is also called a finger electrode, and the interconnector 20 is also called a bus bar 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 surface grid electrode 111 (rear surface grid electrode 125) is narrower than the interconnector 20, and light is incident into the inside of the photoelectric conversion element 10 through gaps between adjacent conductive members. Note that the rear surface grid electrode 125 is on the opposite side to the light-receiving surface, so it may be configured so that light does not pass through it.

[0032] (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 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 materials may be used alone or in combination of two or more. The back transparent electrode 124 is located on the opposite side from the light-receiving surface, so it may not be light-transmitting.

[0033] (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. The top cell electron transport layer 113 preferably also functions as a hole blocking layer that inhibits holes generated in the top cell light absorption layer 114 from migrating 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.

[0034] As long as the top cell 11 has a photoelectric conversion function, it is self-evident that a portion located on the electron transport side (or on the negative electrode side, similarly in the present disclosure) of the top cell light absorbing layer 114 or on the electron transport side within the top cell light absorbing layer 114 has an electron transport function, and there is no need to confirm the electron transport function, which is difficult to confirm in practice. In other words, as long as the top cell 11 has a photoelectric conversion function, a layer located on the electron transport side of the top cell light absorbing layer 114 or on the electron transport side within the top cell light absorbing layer 114 and made of an appropriate material can be considered to be the top cell electron transport layer 113.

[0035] Furthermore, the top cell electron transport layer 113 may also function as the surface transparent electrode 112, and vice versa. Therefore, the photoelectric conversion element 10 does not necessarily have to have both the surface transparent electrode 112 and the top cell electron transport layer 113, and may have only one of them, with one layer also functioning as the other.

[0036] (Top cell light absorption layer) The top cell light absorbing layer 114 can be a layer containing a perovskite compound, which is a photoelectric conversion material. The top cell light absorbing layer 114 is a layer that can absorb at least a portion of light incident on the photoelectric conversion element 10 and generate electrons and holes. Of these, the electrons move to the top cell electron transport layer 113, and the holes move to the top cell hole transport layer 115. The top cell light absorbing layer 114 may be composed solely of a perovskite compound, or may contain a substance other than a perovskite compound.

[0037] The perovskite compound is composed of compounds represented by the general formula: ABX3 (1). The composition ratio of each element is preferably 1:1:3, but it does not necessarily have to be 1:1:3, and the content of each element may be increased or decreased as appropriate.

[0038] In general formula (1), A is an organic molecule (including an organic group or an organic cation, the same applies in this disclosure), an inorganic atom or molecule (including an inorganic group or an inorganic cation, the same applies in this disclosure), or a combination thereof, B is a metal atom or molecule (including a metal cation, the same applies 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, the same applies in this disclosure). In general formula (1), the three Xs may be the same or different from one another.

[0039] 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.

[0040] 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, and it is not necessary to confirm that it has a crystalline structure. For example, it can be determined if it is known that A, B, and X contain organic molecules, metal atoms, and halogen atoms, or that A, B, and X contain inorganic atoms, metal atoms, and halogen atoms.

[0041] In the general formula (1), examples of the organic molecule represented by A include alkylamine, alkylammonium, and nitrogen-containing heterocyclic compounds. In the perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or may be two or more types of organic molecules.

[0042] 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.

[0043] The alkylammonium is an ionized product of the above-mentioned alkylamine. Examples of the alkylammonium 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.

[0044] Examples of the nitrogen-containing heterocyclic compound include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. The nitrogen-containing heterocyclic compound may be an ionized compound. As the ionized nitrogen-containing heterocyclic compound, phenethylammonium is preferred.

[0045] 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.

[0046] In general formula (1), examples of the metal atom 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 the perovskite compound, the metal atom represented by B may be only one type of metal atom, or may be two or more types of metal atoms. From the viewpoint of improving the light absorption properties and charge generation properties of the perovskite compound, the metal atom represented by B is preferably a lead atom or a tin atom. From the viewpoint of reducing lead, a tin atom is preferred.

[0047] In general formula (1), examples of halogen atoms represented by X include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Examples of chalcogen atoms include oxygen atoms, sulfur atoms, selenium atoms, and tellurium atoms. In the perovskite compound, the halogen atoms or chalcogen atoms represented by X may be one type or two or more types. The halogen atom represented by X is preferably an iodine atom, from the viewpoint of enabling the perovskite compound to utilize light in a wide wavelength range. Specifically, of the three Xs, it is preferable that at least one X represents an iodine atom, and it is more preferable that all three Xs represent iodine atoms.

[0048] As the perovskite compound, a compound represented by the general formula "CH3NH3PbX3 (wherein X represents a halogen atom)" is preferred, with CH3NH3PbI3 being more preferred. By using a compound represented by the general formula "CH3NH3PbX3" (particularly 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 the solar cell can be further improved.

[0049] An example of a method for forming the top cell light absorbing layer 114 containing a perovskite compound is a method in which a precursor solution prepared by dissolving a precursor compound of the perovskite compound in an organic solvent is applied by a known method such as spin coating or bar coating to form a film.

[0050] (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. The top cell hole transport layer 115 preferably 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.

[0051] The top cell hole transport layer 115 is mainly composed 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 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, and metal sulfides (e.g., CuO, NiO, and ZnS), and spiro-OMeTAD is preferred.

[0052] As long as the top cell 11 has a photoelectric conversion function, it is self-evident that a portion located on the hole transport side (or on the positive electrode side, similarly in this disclosure) of the top cell light absorbing layer 114 or on the hole transport side within the top cell light absorbing layer 114 has a hole transport function, and there is no need to confirm the hole transport function, which is difficult to confirm in practice. In other words, as long as the top cell 11 has a photoelectric conversion function, a layer located on the hole transport side of the top cell light absorbing layer 114 or on the hole transport side within the top cell light absorbing layer 114 and made of an appropriate material can be considered to be the top cell hole transport layer 115.

[0053] (middle class) In this disclosure, 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 to allow light not absorbed by the top cell 11 to reach the bottom cell 12. That is, the intermediate electrode 13 can be made of a material that is conductive and optically transparent, such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), or gallium-doped zinc oxide (GZO). These materials can be used alone or in combination of two or more. Furthermore, the intermediate layer is not limited to the intermediate electrode 13, and other known structures disposed 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, can also be used. The intermediate layer may be any structure disposed between the top cell and the bottom cell of a tandem solar cell, and as long as the solar cell functions as a solar cell, it is self-evident that it is an intermediate layer and functions as such, regardless of whether its electrical conductivity, transmittance, or other physical properties are confirmed. Furthermore, it is not necessary to use an intermediate layer; a layer on the bottom cell side of the top cell and a layer on the top cell side of the bottom cell, having a similar structure to the intermediate layer, can be used in place of an intermediate layer, and as long as the top cell and bottom cell of a tandem solar cell function as a tandem solar cell, it is self-evident that it functions in place of an intermediate layer, regardless of whether its electrical conductivity, transmittance, or other physical properties are confirmed.

[0054] (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, bottom cell light absorbing layer 122, and bottom cell p-type doped layer 123 can have the same configuration as that used in known silicon solar cells. For example, by adding a doping impurity to the surface of a crystalline silicon substrate, the bottom cell n-type doped layer 121 can be 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 can be formed on the other side. The bottom cell n-type doped layer 121 can be formed by adding phosphorus, arsenic, or the like as a doping impurity, and the bottom cell p-type doped layer 123 can be formed by adding boron, gallium, or the like.

[0055] Furthermore, in a configuration using heterojunction silicon, for example, a configuration can be adopted in which a non-monocrystalline silicon-based thin film such as amorphous silicon or microcrystalline silicon is formed as the bottom cell n-type doped layer 121 and the bottom cell p-type doped layer 123 on a single-crystalline silicon substrate as the bottom cell light absorption layer 122. Examples of materials for the silicon-based thin film as the bottom cell n-type doped layer 121 and the bottom cell p-type doped layer 123 include amorphous silicon, microcrystalline silicon, amorphous silicon alloys, and microcrystalline silicon alloys. Examples of silicon alloys include silicon oxide, silicon carbide, silicon nitride, and silicon germanium. These may be used alone or in combination of two or more.

[0056] Although the photoelectric conversion element 10 shown in FIG. 1 illustrates a configuration in which photocurrent flows from top to bottom in the figure, the direction of the photocurrent is not limited thereto and the photocurrent may flow from bottom to top. In a configuration in which photocurrent 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. The type of doped layer (bottom cell n-type doped layer 121 or bottom cell p-type doped layer 123) in the bottom cell 12 is not particularly limited and may be any of a PERC (Passivated Emitter and Rear Cell) type, a TOPCon (Tunnel Oxide Passivated Contact) type, or a heterojunction type. In addition to the doped layer, a PERC section, a TOPCon section, or a heterojunction section may be provided.

[0057] As shown in FIG. 1, in the photoelectric conversion element 10, the upper electrode layer (surface grid electrode 111 and surface transparent electrode 112) and the back electrode layer (back transparent electrode 124 and back grid electrode 125) are each divided into multiple regions. Specifically, multiple dividing grooves 14 are formed in each of the upper and back electrode layers, and these dividing grooves 14 divide the electrode layer into multiple regions, or the electrode layer is divided into multiple regions along a predetermined arrangement direction. The dividing grooves 14 can be formed by etching a portion of the electrode layer. Alternatively, a mask may be used during deposition of the electrode layer so that the electrode layer is not initially formed in the regions that will become the dividing grooves 14.

[0058] FIG. 2 is a plan view showing a portion of a photoelectric conversion module 100 using a photoelectric conversion element 10. The photoelectric conversion module 100 has at least one photoelectric conversion string in which a plurality of photoelectric conversion elements 10 are connected in series. Alternatively, the photoelectric conversion module 100 may be a photoelectric conversion array in which a plurality of photoelectric conversion strings are connected in parallel. In FIG. 2, two adjacent photoelectric conversion elements 10 in the photoelectric conversion string are extracted and illustrated. Here, the photoelectric conversion element 10 on the upper side in the Y direction in the figure is referred to as the first element 10A, and the photoelectric conversion element 10 on the lower side in the Y direction in the figure is referred to as the second element 10B. Note that the cross-sectional view of FIG. 1 is a cross-sectional view of the photoelectric conversion element 10 shown in FIG. 2 taken along the AA plane.

[0059] The first element 10A and the second element 10B are electrically connected via an interconnector 20. The interconnector 20 is a connection member in which a front interconnector 20A and a back interconnector 20B are integrally connected. In the interconnector 20 that connects the first element 10A and the second element 10B, the front interconnector 20A is connected to an electrode layer on the top surface of the first element 10A, and the back interconnector 20B is connected to an electrode layer on the back surface of the second element 10B. Note that although an interconnector is used here as an example of a connection member, it is not limited to an interconnector and broadly refers to a member that can electrically connect elements to each other.

[0060] Therefore, in the photoelectric conversion element 10, the electrode layer on the top surface of the top cell 11 and the electrode layer on the back surface of the bottom cell 12 are divided into multiple regions, and the divided regions in the electrode layer on the top surface correspond to the divided regions in the electrode layer on the back surface. In the present disclosure, the phrase "the divided regions in the electrode layer on the top surface correspond to the divided regions in the electrode layer on the back surface" does not specifically mean that the divided regions in the electrode layer on the top surface and the divided regions in the electrode layer on the back surface are physically connected to each other, but rather means that the electrode layer on the top surface of the first element 10A is physically connected to the electrode layer on the back surface of the second element 10B, which is an adjacent element. In other words, "corresponding" refers to a relationship in which a certain component (e.g., XA) in the first element 10A is at least physically connected to a component (e.g., YB) in the second element 10B, which is an adjacent element, by a connecting member, and the first element 10A has a component (e.g., YA) corresponding to component YB. Here, for example, the component XA indicates one divided element of the upper electrode layer, and the components YA and YB indicate one divided element of the lower electrode layer.

[0061] As shown in FIG. 2, the dividing grooves 14 are formed in a direction parallel to the interconnector 20. That is, all of the dividing grooves 14 in the photoelectric conversion element 10 are formed so as to be parallel to each other. FIG. 2 illustrates a configuration in which two dividing grooves 14 are provided in each of the electrode layers on the top and back sides of the photoelectric conversion element 10, but the number of dividing grooves 14 (i.e., the number of divided regions in the electrode layer) is not particularly limited. However, the divided regions in the electrode layer on the top side correspond to the divided regions in the electrode layer on the back side, and the number of dividing grooves 14 in the electrode layers on the top and back sides is the same. Furthermore, by forming the dividing grooves 14 in a direction parallel to the interconnector 20, it is possible to effectively provide a region above the bottom cell 12 where the top cell 11 is not present and which is capable of receiving light, which has the advantage of not reducing the current collection efficiency of the interconnector 20.

[0062] The number of divided regions may be the same on the top surface side and the back surface side, and the arrangement direction of the divided regions may be the same on the top surface side and the back surface side. In this case, in the photoelectric conversion element 10, the divided regions in the electrode layer on the top surface side and the divided regions in the electrode layer on the back surface side not only correspond to each other, but also correspond to each other on the top surface side and the back surface side in the same arrangement order along the arrangement direction. Furthermore, the corresponding divided regions at least partially overlap each other in a plan view, and it is more preferable that they completely overlap in a plan view.

[0063] At least one interconnector 20 is connected to each of the divided regions in the electrode layer on the top and back sides of the photoelectric conversion element 10. Although Figures 1 and 2 show an example of a configuration in which one interconnector 20 is connected to one divided region of the electrode layer, two or more interconnectors 20 may be connected to one divided region.

[0064] In the photoelectric conversion element 10, the electrode layers on the top and back sides are divided into multiple regions, so that in-plane current in these electrode layers occurs only within each region, and does not occur throughout the entire electrode layer. Therefore, even if a cause of current concentration, such as a short circuit, occurs within the photoelectric conversion element 10, the current concentration occurs only within the region containing that cause, and current concentration does not occur in other regions. This significantly reduces current concentration within the cell. The effect of suppressing current concentration in the photoelectric conversion element 10 increases as the number of regions divided into the electrode layers increases.

[0065] In the photoelectric conversion element 10, layers other than the electrode layers on the top and back sides have low electrical resistance in the direction perpendicular to the junction surface with other layers (i.e., the film thickness direction), but high electrical resistance in the direction parallel to the junction surface (i.e., the in-plane direction). Alternatively, the scale in the in-plane direction and the scale in the film thickness direction differ by a much larger order of magnitude than shown in the figure. Considering a layer with a constant resistivity higher than that of the electrode, the scale in the film thickness direction is small, allowing current to flow easily, but the scale in the in-plane direction is much larger, making it difficult for in-plane current to occur. Therefore, in-plane current is unlikely to occur in layers other than the electrode layers on the top and back sides. Therefore, the photoelectric conversion element 10 can achieve the effect of suppressing current concentration by dividing only the electrode layers that are prone to in-plane current.

[0066] The intermediate electrode 13 as an intermediate layer in the photoelectric conversion element 10 is formed between the top cell 11 and the bottom cell 12 for the purpose of reducing electrical resistance in the film thickness direction, but in many cases the film thickness of the intermediate layer or intermediate electrode 13 is extremely thin, resulting in high electrical resistance in the in-plane direction. In this case, the effect of suppressing current concentration in the photoelectric conversion element 10 can be sufficiently obtained even without dividing the intermediate layer or intermediate electrode 13. However, by forming a separation groove similar to that for the electrode layer and separating the intermediate layer or intermediate electrode 13, an even greater effect of suppressing current concentration can be obtained.

[0067] The reason for dividing not only the upper electrode layer but also the back electrode layer in the photoelectric conversion element 10 is as follows. For example, assume that a cause of current concentration (short circuit) occurs on the first element 10A side in the photoelectric conversion module 100 shown in FIG. 2 . In addition, assume that the upper electrode layer of the first element 10A is divided as shown in the figure, but the back electrode layer of the second element 10B is not divided. In this case, the upper electrode layer of the first element 10A and the back electrode layer of the second element 10B are connected by the interconnector 20, and an in-plane current is generated in the back electrode layer of the second element 10B. As a result, the current is concentrated in the interconnector 20 connected to the region where the power concentration is occurring, among the three interconnectors 20 in the first element 10A. Therefore, in the first element 10A, the effect of dividing the upper electrode layer is not realized, and current concentration occurs. By dividing not only the upper electrode layer but also the back electrode layer, current concentration through the electrodes connected by the interconnector 20 can be prevented.

[0068] 2, the front grid electrode 111 and the front transparent electrode 112 are upper electrode layers, and the back transparent electrode 124 and the back grid electrode 125 are back electrode layers, and all of these electrodes are divided. However, if the front transparent electrode 112 and the back transparent electrode 124 are thin and the in-plane electrical resistance of the front transparent electrode 112 and the back transparent electrode 124 is sufficiently high, the effects of the present invention can be achieved even if the front transparent electrode 112 and the back transparent electrode 124 are not divided, and only the front grid electrode 111 and the back grid electrode 125 are divided. In other words, only the front grid electrode 111 and the back grid electrode 125 may be considered as the upper and back electrode layers that need to be divided.

[0069] Furthermore, in this disclosure, unless otherwise specified, the thickness or width of a layer or film is not specified, and includes patterned or island-shaped layers and layers with portions of different thicknesses. Layers and films preferably have a substantially constant thickness. Unless otherwise specified, the terms "substantially" and "approximately" refer to the range of manufacturing error, and preferably allow for a variation of plus or minus 15% of the numerical value.

[0070] Second Embodiment 3 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element 10 according to a second embodiment of the present disclosure. The photoelectric conversion element 10 according to this embodiment can have the same configuration as that of the first embodiment, except as described below.

[0071] In this embodiment, the dividing grooves 14 formed on the upper surface side of the photoelectric conversion element 10 divide not only the electrode layers (surface grid electrode 111 and surface transparent electrode 112), but also other layers in the top cell 11 (top cell electron transport layer 113, top cell light absorption layer 114, and top cell hole transport layer 115) and the intermediate electrode 13. That is, in this embodiment, the dividing grooves 14 divide the entire top cell 11 and the intermediate electrode 13 into multiple regions in the same layout as the electrode layers on the upper surface side.

[0072] In the first embodiment, the layers other than the electrode layer in the top cell 11 and the intermediate electrode 13 have high electrical resistance in the in-plane direction, making it difficult for in-plane current to occur in the layers other than the electrode layer and the intermediate electrode 13, and it was thought that dividing only the electrode layer would have the effect of suppressing current concentration. However, this does not mean that in-plane current does not occur at all in the layers other than the electrode layer and the intermediate electrode 13. For this reason, in the present embodiment, by dividing the entire top cell 11 and even the intermediate electrode 13 by the dividing grooves 14, the in-plane current in the top cell 11 and the intermediate electrode 13 can be blocked for each divided top cell 11 and each divided intermediate electrode 13, thereby further improving the effect of suppressing current concentration.

[0073] As in the first embodiment, the dividing grooves 14 in this embodiment can be formed by etching away the layer in which the dividing grooves 14 are to be formed, or by using a mask when depositing the layer in which the dividing grooves 14 are to be formed. Alternatively, the dividing grooves 14 can be formed by a scribing method (laser scribing or mechanical scribing).

[0074] As a modified example of this embodiment, a configuration in which the entire top cell 11 is divided by the dividing groove 14, but the intermediate electrode 13 is not divided, may be included. Alternatively, a configuration in which the electrode layers (surface grid electrode 111 and surface transparent electrode 112) and the intermediate electrode 13 of the top cell 11 are divided, but the other layers in the top cell 11 (top cell electron transport layer 113, top cell light absorption layer 114, and top cell hole transport layer 115) are not divided may be included. Note that a configuration in which, in addition to dividing the electrode layers (surface grid electrode 111 and surface transparent electrode 112) and the intermediate electrode 13 of the top cell 11, any of the other layers (applicable layers including the top cell electron transport layer 113, top cell light absorption layer 114, and top cell hole transport layer 115) are divided, but the others are not divided, may be appropriately selected and is not excluded.

[0075] Third Embodiment FIG. 4 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element 10 according to a third embodiment of the present disclosure. While the first and second embodiments illustrate a two-junction photoelectric conversion element 10 in which two types of light absorption layers (photoelectric conversion layers) are stacked, this embodiment illustrates a three-junction photoelectric conversion element 10 in which three types of light absorption layers (photoelectric conversion layers) are stacked. In this disclosure, the term "two-junction" refers to a tandem solar cell having two light absorption layers capable of sequentially absorbing light, and the description of the tandem solar cell can be applied to the configuration of the light absorption layers. Similarly, the term "three-junction" refers to a tandem solar cell having three light absorption layers capable of sequentially absorbing light, and the description of the tandem solar cell can be applied to the configuration of the light absorption layers. Note that the term "junction" here does not literally mean "junction," but is a term commonly used to describe the number of light absorption layers in a tandem solar cell. In practice, the term "junction" can be understood as "light absorption layer."

[0076] The photoelectric conversion element 10 in FIG. 4 has a configuration in which a middle cell 15 is stacked in addition to a top cell 11 and a bottom cell 12. Specifically, the top cell 11 is disposed on the upper surface side, the bottom cell 12 is disposed on the back surface side, and the middle cell 15 is disposed between the top cell 11 and the bottom cell 12. The configurations of the top cell 11 and the bottom cell 12 in this embodiment can be similar to those of the top cell 11 and the bottom cell 12 in the first and second embodiments. Furthermore, as intermediate layers, 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 configured similarly to the intermediate layer or intermediate electrode 13 in the first and second embodiments.

[0077] The middle cell 15 has, in order from the top side, a middle cell electron transport layer 151, a middle cell light absorbing layer 152, and a middle cell hole transport layer 153. Like the top cell 11, the middle cell 15 is a perovskite solar cell, but it is preferable that at least some of the materials used in the middle cell 15 are different from those in the top cell 11, and that the wavelength of light to be photoelectrically converted is different from that of the top cell 11. That is, more specifically, it is preferable that the wavelength range of light that can be absorbed by the top cell light absorbing layer 114 and the middle cell light absorbing layer 152 differ. In particular, if the wavelength range of light that can be absorbed by the light absorbing layer of the middle cell 15 is longer than the wavelength range of light that can be absorbed by the light absorbing layer of the top cell 11, the photoelectric conversion efficiency of the element can be further improved.

[0078] In this triple-junction photoelectric conversion element 10, as in the case of the two-junction type, the effect of suppressing current concentration can be achieved by dividing the upper electrode layer (the front grid electrode 111 and the front transparent electrode 112) and the back electrode layer (the back transparent electrode 124 and the back grid electrode 125) into multiple regions. In other words, current concentration can be suppressed whether the cause of current concentration, such as a short circuit, is in the top cell 11 or the middle cell 15.

[0079] 4, only the upper electrode layer (the surface grid electrode 111 and the surface transparent electrode 112) and the rear electrode layer (the rear transparent electrode 124 and the rear grid electrode 125) are divided into regions, but the electron transport layer, the light absorption layer, and the hole transport layer in the top cell 11 and the middle cell 15 may or may not be divided into regions. The example described in the second embodiment can be applied as appropriate and without contradiction to the form of region division.

[0080] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be determined based on the claims.

[0081] [Note]

[0082] (Aspect 1) A photoelectric conversion element in a tandem solar cell, a top cell disposed on the light-receiving surface side and a bottom cell disposed on the back surface side, an electrode layer on an upper surface side of the top cell and an electrode layer on a back surface side of the bottom cell are divided into a plurality of regions; A photoelectric conversion element, wherein the divided regions in the electrode layer on the upper surface side correspond to the divided regions in the electrode layer on the rear surface side.

[0083] (Aspect 2) The photoelectric conversion element according to aspect 1, an electrode layer on an upper surface side of the top cell and an electrode layer on a back surface side of the bottom cell are divided into a plurality of divided regions along a predetermined arrangement direction; A photoelectric conversion element characterized in that the number of divided regions in the electrode layer on the upper surface side and the number of divided regions in the electrode layer on the back surface side are the same, and the arrangement direction of the divided regions on the upper surface side and the back surface side is the same.

[0084] (Aspect 3) The photoelectric conversion element according to aspect 1 or 2, A photoelectric conversion element characterized in that the entire top cell is divided into a plurality of regions corresponding to the upper electrode layer and the rear electrode layer.

[0085] (Aspect 4) The photoelectric conversion element according to any one of Aspects 1 to 3, an intermediate layer disposed between the top cell and the bottom cell; A tandem solar cell, wherein the intermediate layer is divided into a plurality of regions corresponding to the upper electrode layer and the back electrode layer.

[0086] (Aspect 5) The photoelectric conversion element according to any one of aspects 1 to 4, The photoelectric conversion element is characterized in that the top cell has a light absorption layer containing a perovskite compound.

[0087] (Aspect 6) The photoelectric conversion element according to any one of aspects 1 to 5, A photoelectric conversion element comprising a middle cell disposed between the top cell and the bottom cell.

[0088] (Aspect 7) A photoelectric conversion module having a photoelectric conversion string in which a plurality of photoelectric conversion elements according to any one of aspects 1 to 6 are connected in series, two adjacent photoelectric conversion elements in the photoelectric conversion string are electrically connected via a connection member; A photoelectric conversion module, characterized in that at least one of the connecting members is provided in each of the divided regions of the upper electrode layer and the lower electrode layer of the photoelectric conversion element. [Explanation of symbols]

[0089] 10 Photoelectric conversion element 100 Photoelectric conversion module 11 Top Cell 111 Surface grid electrode (top electrode layer) 112 Surface transparent electrode (top electrode layer) 113 Top cell electron transport layer 114 Top cell light absorption layer 115 Top cell hole transport layer 12 Bottom Cell 121 Bottom cell n-type doped layer 122 Bottom cell light absorption layer 123 Bottom cell p-type doped layer 124 Rear transparent electrode (rear electrode layer) 125 Back grid electrode (back electrode layer) 13,131,132 Intermediate electrode 14 Dividing groove 15 Middle Cell 151 Middle cell electron transport layer 152 Middle cell light absorption layer 153 Middle cell hole transport layer 20 Interconnector (connecting member) 20A Surface Interconnector 20B rear interconnector

Claims

1. A photoelectric conversion element in a tandem solar cell, a top cell disposed on the light-receiving surface side and a bottom cell disposed on the back surface side, an electrode layer on an upper surface side of the top cell and an electrode layer on a back surface side of the bottom cell are divided into a plurality of regions; A photoelectric conversion element, wherein the divided regions in the electrode layer on the upper surface side correspond to the divided regions in the electrode layer on the rear surface side.

2. The photoelectric conversion element according to claim 1, an electrode layer on an upper surface side of the top cell and an electrode layer on a back surface side of the bottom cell are divided into a plurality of divided regions along a predetermined arrangement direction; A photoelectric conversion element characterized in that the number of divided regions in the electrode layer on the upper surface side and the number of divided regions in the electrode layer on the back surface side are the same, and the arrangement direction of the divided regions on the upper surface side and the back surface side is the same.

3. The photoelectric conversion element according to claim 1, A photoelectric conversion element characterized in that the entire top cell is divided into a plurality of regions corresponding to the upper electrode layer and the rear electrode layer.

4. The photoelectric conversion element according to claim 1, an intermediate layer disposed between the top cell and the bottom cell; A tandem solar cell, wherein the intermediate layer is divided into a plurality of regions corresponding to the upper electrode layer and the back electrode layer.

5. The photoelectric conversion element according to claim 1, The photoelectric conversion element is characterized in that the top cell has a light absorption layer containing a perovskite compound.

6. The photoelectric conversion element according to claim 1, A photoelectric conversion element comprising a middle cell disposed between the top cell and the bottom cell.

7. A photoelectric conversion module having a photoelectric conversion string in which a plurality of photoelectric conversion elements according to any one of claims 1 to 6 are connected in series, two adjacent photoelectric conversion elements in the photoelectric conversion string are electrically connected via a connection member; A photoelectric conversion module, characterized in that at least one of the connection members is provided in each of the divided regions of the upper electrode layer and the lower electrode layer of the photoelectric conversion element.

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