Photoelectric conversion element

Abstract

A photoelectric conversion element is provided that, in a series-connected solar cell, can suppress in-plane current density non-uniformity and achieve current matching between the top cell and the bottom cell. It is configured to include a top cell (11) disposed on the light-receiving side and a bottom cell (12) disposed on the back side. An opening groove (14) is formed in the light-absorbing layer (114) of the top cell, allowing a portion of the light incident from the light-receiving side to bypass the top cell light-absorbing layer (114) and instead enter the bottom cell light-absorbing layer (122).

Description

[Technical Field]

[0001] This disclosure relates to photoelectric conversion elements in tandem solar cells. [Previous Technology]

[0002] To improve the power generation efficiency of solar cells, tandem solar cells in which different types of light-absorbing layers (photoelectric conversion layers) are stacked have been proposed. As an example of a tandem solar cell, a perovskite / silicon solar cell (e.g., Patent Document 1) can be cited. Prior Art Documents Patent Documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-910 [Summary of the Invention]

[0004] The technical problem to be solved by this disclosure is that in a series-connected solar cell, different types of light-absorbing layers are connected in series, but the current-voltage characteristics are different for each light-absorbing layer. Therefore, the current extracted by the series-connected solar cell is limited by the minimum current generated by each light-absorbing layer. Therefore, the series-connected solar cell is designed so that the current generated in each light-absorbing layer is equal, that is, current matching is achieved.

[0005] Figure 7 is a cross-sectional view showing the schematic configuration of a conventional photoelectric conversion element 50 in a series-connected solar cell. As shown in Figure 7, the photoelectric conversion element 50 is configured with a top cell 51 and a bottom cell 52 stacked on top of each other. The top cell 51 is disposed on the upper surface side, and the bottom cell 52 is disposed 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 battery 51, from its upper surface side, sequentially comprises a surface gate 511, a surface transparent electrode 512, a top battery electron transport layer 513, a top battery light absorption layer 514, and a top battery hole transport layer 515. The bottom battery 52, from its upper surface side, sequentially comprises a bottom battery n-type doped layer 521, a bottom battery light absorption layer 522, a bottom battery p-type doped layer 523, a back transparent electrode 524, and a back gate 525. Furthermore, an intermediate electrode (or intermediate layer) 53 is provided between the top battery 51 and the bottom battery 52, and the top battery 51 and the bottom battery 52 are connected in series through the intermediate electrode 53. Interconnectors 60 are connected to the top and back of the photoelectric conversion element 50.

[0007] Furthermore, when using expressions indicating "up" or "down," the light-receiving side of the component can be described as "up," and the back side of the component can be described as "down," unless otherwise specified. That is, basically, the light-receiving side and the up side mean the same thing, and the back side and the down side also mean the same thing.

[0008] Furthermore, the light-receiving surface refers to the side of a single-sided light-receiving solar cell where light directly enters the element. In a double-sided light-receiving solar cell, one side can be considered as the light-receiving surface, and when one side is considered as the light-receiving surface, the opposite side can be considered as the back side. That is, as long as the structure disclosed herein is present, it can be considered to fall within the technical scope of this disclosure when at least one side is considered as the light-receiving surface. In other words, even if the structure disclosed herein is not present when any one side is considered as the light-receiving surface, as long as the structure disclosed herein is present when the other side is considered as the light-receiving surface, it can be considered to fall within the technical scope of this disclosure.

[0009] In the photoelectric conversion element 50, for example, by changing the composition of the perovskite compound contained in the top cell light-absorbing layer 514, its bandgap can be altered, thereby achieving a match between the current generated in the top cell 51 and the current generated in the bottom cell 52. Figure 8 is a graph showing the results of simulating the change in photoelectric conversion efficiency (Pmax in Figure 8) in a series-connected solar cell having the structure shown in Figure 7, where the bandgap of the top cell 51 is changed, thus altering the ratio of the current generated in the top cell 51 to the current generated in the bottom cell 52. As can be seen from the results shown in Figure 8, the bandgap of the top cell light-absorbing layer 514 has a peak photoelectric conversion efficiency around 1.7 eV. Thus, in a series-connected solar cell having the structure shown in Figure 7, it is sometimes necessary to adjust the bandgap of the top cell to a specific value to achieve current matching.

[0010] However, when current matching is achieved by changing the composition of the perovskite compound, the design changes required involve many aspects, such as: the design of the interface with the adjacent layer of the light-absorbing layer in the photoelectric conversion element, the design of the method for forming the light-absorbing layer in the manufacturing process, the design of the thermal history in the formation process, and the design of the resulting impact on other layers. Therefore, changing the bandgap value of the top cell by altering the composition of the perovskite compound has too great an impact on the overall design of the photoelectric conversion element, which becomes a problem.

[0011] As a method for achieving current matching without limiting the bandgap value of the top cell, it is possible to consider forming the top cell to be slightly smaller than the bottom cell. In this case, the top cell is not present on the bottom cell at its periphery. Therefore, at the periphery of the bottom cell, light incident from the light-receiving surface directly enters the bottom cell without passing through the top cell. As a result, the amount of light received by the bottom cell increases, thus enabling current matching between the top and bottom cells. When the in-plane resistance of the intermediate layer (or intermediate electrode) between the top and bottom cells is sufficiently small relative to the size of the top cell, the current generated at the periphery of the bottom cell also reaches the center, thus minimizing problems in current matching.

[0012] However, when the top cell is large, there is a distance between its periphery and center, and the in-plane resistance of the intermediate layer (or intermediate electrode) between the top and bottom cells cannot be reduced, there is a problem that the current generated at the periphery of the bottom cell cannot reach the center. That is, there is a problem that the in-plane current density of the solar cell becomes uneven. In particular, in perovskite / silicon solar cells, from the viewpoint that it is difficult to significantly reduce the resistance of the intermediate layer (or intermediate electrode), or if the width of the top cell is not less than a few centimeters, it is difficult to improve the photoelectric conversion efficiency through current matching. However, considering that in recent years, silicon wafers used in solar cells have become mainstream with a width of 18 cm or more, it is difficult to achieve current matching using this method.

[0013] This disclosure was made in view of the above-mentioned problems, and its object is to provide a photoelectric conversion element in a series-connected solar cell that can suppress in-plane current density non-uniformity and achieve current matching between the top and bottom cells. Technical solution for solving the technical problem

[0014] To solve the above-mentioned problems, a photoelectric conversion element is provided below. The photoelectric conversion element disclosed herein is a photoelectric conversion element in a series-connected solar cell, comprising: a top cell disposed on the light-receiving surface side; and a bottom cell disposed on the back side side. An opening groove is formed in the light-absorbing layer of the top cell, allowing a portion of the light incident from the light-receiving surface side to bypass the light-absorbing layer of the top cell and instead enter the light-absorbing layer of the bottom cell. Beneficial Effects

[0015] According to the photoelectric conversion element disclosed herein, in a series-connected solar cell, while suppressing the uneven density of current in the plane, it achieves excellent effects such as current matching between the top cell and the bottom cell.

Implementation Method

[0017] <First Embodiment> Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. FIG1 is a diagram showing one embodiment of the present disclosure, and is a cross-sectional view showing a schematic configuration of the photoelectric conversion element 10.

[0018] The photoelectric conversion element 10 is a photoelectric conversion element in a series solar cell using a perovskite solar cell. In Figure 1, the upper surface is the light-receiving surface. As shown in Figure 1, the photoelectric conversion element 10 is composed of a top cell 11 and a bottom cell 12 stacked together. The top cell 11 is disposed on the upper side, and the bottom cell 12 is disposed on the back side.

[0019] Furthermore, in this disclosure, a series-type solar cell refers to a solar cell configured such that part or all of the light (specifically, light with a certain wavelength band) incident from the light-receiving surface side of the photoelectric conversion element can be absorbed sequentially by two or more light-absorbing layers.

[0020] In this disclosure, a series-connected solar cell refers to a solar cell in which two light-absorbing layers are sequentially disposed from the light-receiving side to the back side of the photoelectric conversion element, starting from the light-receiving side. Furthermore, when viewed from the light-receiving side, the two light-absorbing layers do not need to completely overlap; at least a partial overlap is sufficient. Preferably, at least one light-absorbing layer completely overlaps with the other. That is, in this disclosure, a series-connected solar cell is defined as one in which a portion or all of the light (specifically, light with a certain wavelength) incident from the light-receiving side of the photoelectric conversion element can pass through one light-absorbing layer to the other. Furthermore, the light-absorbing layers described here do not need to be single-layered; they can be multi-layered. Multi-layered structures, such as those formed by PN junctions, are used.

[0021] Furthermore, the light-absorbing layer is a layer capable of absorbing light incident on the photoelectric conversion element to generate electrons and holes. The generation of electrons and holes by the light-absorbing layer is self-evident as long as the solar cell functions as a solar cell. As long as the light-absorbing layer is made of appropriate materials, it is not necessary to confirm the generation of electron-hole pairs by absorbing light, which is extremely difficult to absorb.

[0022] The top cell 11 of the photoelectric conversion element 10 has, from the top surface side, a surface gate 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, from the top 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 transparent electrode 124, and a back gate 125. In addition, 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 through the intermediate electrode 13.

[0023] In this 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 light-absorbing layer 114 of the top cell is a layer containing a perovskite compound as a photoelectric conversion material, which can be composed solely of the perovskite compound or contain substances other than the perovskite compound.

[0024] Furthermore, in the solar cell (or photoelectric conversion module) using the photoelectric conversion element 10, a surface interconnect 20A is connected to the upper surface of the photoelectric conversion element 10 (i.e., the upper surface of the top battery 11), and a back interconnect 20B is connected to the back surface of the photoelectric conversion element 10 (i.e., the lower surface of the bottom battery 12).

[0025] The photoelectric conversion element 10 shown in FIG1 can be fabricated by forming the layers required for the top battery 11 on the bottom battery 12. However, the fabrication order of the photoelectric conversion element 10 of this disclosure is not particularly limited. The photoelectric conversion element 10 can be fabricated by other methods, such as bonding the batteries after fabricating the top battery 11 and the bottom battery 12 respectively.

[0026] The photoelectric conversion element 10 shown in Figure 1 illustrates a configuration where current flows from top to bottom, but the direction of current is not limited to this; it can also be a configuration where current flows from bottom to top. In the case of a configuration where current flows from bottom to top, in the top cell 11, the positions of the top cell electron transport layer 113 and the top cell hole transport layer 115 are interchanged, and in the bottom cell 12, the positions of the bottom cell n-type doped layer 121 and the bottom cell p-type doped layer 123 are interchanged. Furthermore, 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; it can be any of PERC (Passivated Emitter and Rear Cell), TOPCon (Tunnel Oxide Passivated Contact), or heterojunction type. In addition to the doped layer, a PERC section, a TOPCon section, or a heterojunction section can also be provided.

[0027] As shown in FIG1, in the photoelectric conversion element 10, an opening slot 14 is formed in the top battery light absorption layer 114 so that a portion of the light incident from the light-receiving surface side (the upper side in FIG1) can be incident on the bottom battery light absorption layer 122 without passing through the top battery light absorption layer 114. Furthermore, in this embodiment, a photoelectric conversion element 10 with an opening slot 14 formed in the top battery 11 is described as an example, so that a portion of the light incident from the light-receiving surface side can be incident on the bottom battery 12 without passing through the top battery 11, but this configuration is not limited to this. That is, a configuration in which the opening slot 14 does not penetrate a part of the layer constituting the top battery 11 is not excluded; in other words, a configuration in which a part of the layer constituting the top battery 11 is provided in the area where the opening slot 14 is located in FIG1.

[0028] In this embodiment, a plurality of opening slots 14 are provided on the top battery 11, and the top battery 11 is divided into a plurality of regions by the opening slots 14. In addition, as a fourth embodiment, as illustrated later, it is also possible to adopt a configuration in which the opening slots 14 are not divided into a plurality of regions.

[0029] Furthermore, "a portion of the light incident from the light-receiving surface side can be incident on the constituent element B without passing through constituent element A" means, for example, specifically, "when constituent element A and constituent element B are sequentially arranged from the light-receiving surface side to the back side of the photoelectric conversion element, in a configuration where, when viewed from the light-receiving surface side, at least a portion of constituent element B does not overlap with constituent element A." Other configurations are not excluded. For example, it is not necessarily limited to the case of viewing from an angle perpendicular to the light-receiving surface; in the case of a structure having light incident at a certain angle, it is also possible to satisfy the above configuration when viewed from that certain angle.

[0030] The opening slot 14 can be formed by removing a portion of the top battery 11 using a scribing method (laser scribing or mechanical scribing). Alternatively, a mask can be used when forming the top battery 11 so that the top battery 11 is not formed in the area that is the opening slot 14 from the beginning.

[0031] FIG2 is a top view showing a portion of a photoelectric conversion module 100 using photoelectric conversion elements 10. The photoelectric conversion module 100 has at least one column of photoelectric conversion strings formed by connecting a plurality of photoelectric conversion elements 10 in series. Alternatively, the photoelectric conversion module 100 may also be a photoelectric conversion array in which multiple columns of photoelectric conversion strings are connected in parallel. In FIG2, two adjacent photoelectric conversion elements 10 in the photoelectric conversion string are shown separately. Here, the photoelectric conversion element 10 on the upper side in the Y direction is designated as the first element 10A, and the photoelectric conversion element 10 on the lower side in the Y direction is designated as the second element 10B. Furthermore, the cross-sectional view in FIG1 is a cross-sectional view of the photoelectric conversion element 10 shown in FIG2 cut off by plane AA.

[0032] The first element 10A and the second element 10B are electrically connected via an interconnect 20. The interconnect 20 is a connection component that integrally connects the surface interconnect 20A and the back interconnect 20B. In the interconnect 20 connecting the first element 10A and the second element 10B, the surface interconnect 20A is connected to the surface gate 111 of the first element 10A, and the back interconnect 20B is connected to the back gate 125 of the second element 10B. Furthermore, although an interconnect is illustrated herein, the connection component is not limited to an interconnect, but refers to a component capable of electrically connecting elements to elements in a relatively wide range.

[0033] As shown in FIG2, the opening slot 14 is formed in a direction parallel to the interconnect 20. That is, all the opening slots 14 in the photoelectric conversion element 10 are formed in parallel. FIG2 illustrates a configuration in which two opening slots 14 are provided on the photoelectric conversion element 10, but as illustrated in the second and third embodiments in the following sections, the number of opening slots 14 is not particularly limited.

[0034] In the top battery 11 of the photoelectric conversion element 10, at least one interconnect 20 is connected to each of the divided regions. In this embodiment, a configuration is adopted in which one interconnect 20 is connected to one divided region of the top battery 11. However, as in the third embodiment, as illustrated later, two or more interconnects 20 may be connected to one divided region.

[0035] In the photoelectric conversion element 10, an opening slot 14 is formed on the top cell 11, thereby reducing the amount of light received by the top cell 11. Furthermore, light passing through the opening slot 14 directly enters the bottom cell 12 without passing through the top cell 11, thus increasing the amount of light received by the bottom cell 12. That is, the current generated in the top cell 11 decreases, while the current generated in the bottom cell 12 increases. Therefore, by adopting this configuration, current matching between the top cell 11 and the bottom cell 12 can be achieved. Moreover, during the design phase of the photoelectric conversion element 10, it is not necessary to change the composition of the perovskite compound in the light absorption layer 114 of the top cell. Therefore, the problem of excessive impact on the overall design of the photoelectric conversion element 10 caused by design changes to the light absorption layer 114 of the top cell can be eliminated.

[0036] In addition, by forming the opening slot 14 along the direction parallel to the inner connector 20, an area that is not covered by the top battery 11 and can be exposed to light can be effectively provided on the bottom battery 12, which has the advantage that the power collection efficiency of the interconnect 20 will not decrease.

[0037] Furthermore, since the interconnects 20 are connected to the divided regions of the top battery 11, the current flowing through each of the interconnects 20 can be equalized. That is, the deterioration of the current-voltage characteristics caused by the formation of the opening slot 14 in the top battery 11 can be suppressed.

[0038] Furthermore, in this embodiment, an intermediate electrode 13 is provided on the bottom battery 12, so that the light incident on the opening slot 14 passes strictly through the intermediate electrode 13 before reaching the bottom battery 12. As a variation of this embodiment, it may include a configuration in which the intermediate electrode 13 is not provided between the top battery 11 and the bottom battery 12 (a configuration in which the top battery 11 and the bottom battery 12 are directly connected).

[0039] Next, the preferred aperture ratio of the top battery 11 formed by the opening slot 14 in the photoelectric conversion element 10 will be explained. Here, the aperture ratio of the top battery 11 in this disclosure refers to a value calculated as the ratio of the opening area of ​​the opening slot 14 in the top battery 11 to the area of ​​one side of the bottom battery 12 (or, the area of ​​one side of the top battery 11 in the state before the opening slot 14 is formed). An example of the aperture ratio of the top battery 11 is 3% or more and 20% or less. A specific calculation example will be described later using the second embodiment as an example.

[0040] Figure 9 is a graph showing the relationship between the aperture ratio of the top cell and the photoelectric conversion efficiency (Pmax) for three of the six cells (curves 6) with band gaps changed as shown in Figure 8 (which have band gaps below 1.7 eV). According to Figure 9, the smaller the band gap, the stronger the trend of increasing cell output as the aperture ratio of the top cell increases.

[0041] The results show that in a battery with a band gap of 1.65 eV, the battery output is maximized when the aperture ratio is around 5% (e.g., 2% to 8%, more preferably 3% to 7%). In a battery with a band gap of 1.55 eV, the battery output is maximized when the aperture ratio is around 15% (e.g., 2% to 30%, more preferably 3% to 20%, more preferably 6% to 15%). Furthermore, in a battery with a band gap of 1.46 eV, it is inferred that the battery output is maximized when the aperture ratio is greater than 15%.

[0042] As can be seen from this result, when the current generated in the bottom battery is smaller than that generated in the top battery when using a top battery with a band gap of 1.7 eV or less, the output of the battery can be improved by adopting a configuration of a photoelectric conversion element 10 with an opening slot 14 formed on the top battery 11.

[0043] For example, CH3NH3PbI3 is known as a perovskite compound for perovskite solar cells, but its band gap is 1.55 eV to 1.6 eV. As the top cell of a series solar cell, its band gap is relatively narrow, which makes it difficult to improve the photoelectric conversion efficiency. Even when CH3NH3PbI3 is used as the photoelectric conversion material of the light absorption layer 114 of the top cell, by forming the opening groove 14 with an aperture ratio of about 10% (for example, more than 5% and less than 15%), the output of the cell can be improved compared with the case where the opening groove 14 is not formed.

[0044] Hereinafter, the structure of each layer in the photoelectric conversion element 10 will be described as an example. However, known technologies can be applied to the materials and film formation methods of each layer in the photoelectric conversion element 10. Therefore, the structure of each layer applicable to this embodiment is not limited to this example. That is, as long as it has the function of a photoelectric conversion element in a series solar cell, layers that can be omitted can be omitted, layers other than those described below can be included, and one layer can also function as another layer.

[0045] (Surface Gate, Back Gate) The surface gate 111 and the back gate 125 are composed of a plurality of parallel conductive members. These conductive members extend along a first direction (the X direction shown in Figures 1 and 2) and are arranged parallel to each other along a second direction (the Y direction shown in Figures 1 and 2) at intervals. The plurality of conductive members in the surface gate 111 (back gate 125) are connected by a gate disposed on or below the interconnect 20. Specifically, the interconnect 20 is configured to extend along the second direction and be orthogonal to the plurality of conductive members. The second direction is along the short side of the photoelectric conversion element 10; therefore, by arranging it in such a way that it extends along this direction, the resistance of the interconnect 20 can be reduced.

[0046] The surface gate 111 (back gate 125) is also referred to as a finger electrode, and the interconnect 20 is also referred to as a bus electrode. The material of the conductive components is not particularly limited; for example, metals such as silver, copper, and aluminum can be used. The conductive components of the surface gate 111 (back gate 125) are configured to be narrower than the interconnect 20, allowing light to enter the interior of the photoelectric conversion element 10 through the gaps between adjacent conductive components. Furthermore, since the back gate 125 is on the side opposite to the light-receiving surface, it can be configured to be light-blocking.

[0047] (Front transparent electrode, back transparent electrode) The front transparent electrode 112 and the back transparent electrode 124 are thin-film electrodes that are both conductive and transparent. Examples of materials used 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 materials can be used individually or in combination. Furthermore, since the back transparent electrode 124 is the side opposite to the light-receiving surface, it can also be configured to be opaque.

[0048] (Top Battery Electron Transport Layer) The top battery electron transport layer 113 is a layer that transports electrons generated in the top battery light absorption layer 114 to the surface transparent electrode 112. The top battery electron transport layer 113 preferably also functions as a hole blocking layer to suppress the movement of holes generated in the top battery light absorption layer 114 towards the surface transparent electrode 112. Examples of materials for the top battery electron transport layer 113 include tin oxide, titanium oxide, and zinc oxide.

[0049] Furthermore, as long as the top battery 11 has a photoelectric conversion function, it is obvious that the portion located on the electron transport side (or negative electrode side, which is the same in this disclosure) or within the electron transport side of the top battery light absorption layer 114 has the function of electron transport, and it is not necessary to confirm an electron transport function that is actually difficult to confirm. That is, as long as the top battery 11 has a photoelectric conversion function, the layer located on the electron transport side or within the top battery light absorption layer 114 and made of a suitable material can be regarded as the top battery electron transport layer 113.

[0050] In addition, the top battery electron transport layer 113 can also function as the surface transparent electrode 112, and vice versa. Therefore, the photoelectric conversion element 10 may not have both the surface transparent electrode 112 and the top battery electron transport layer 113, or it may have only one of them, with one functioning as the other.

[0051] (Top Battery Light Absorption Layer) The top battery light absorption layer 114 may be a layer containing a perovskite compound as a photoelectric conversion material. The top battery light absorption layer 114 is a layer capable of absorbing at least a portion of the light incident on the photoelectric conversion element 10 and generating electrons and holes. Electrons move to the top battery electron transport layer 113, and holes move to the top battery hole transport layer 115. The top battery light absorption layer 114 may be composed solely of a perovskite compound, or it may contain substances other than a perovskite compound.

[0052] The perovskite compound is composed of a compound with the general formula: ABX3··(1). However, it is preferred that the ratio of each component is 1:1:3, but it is not necessarily 1:1:3, and the content of each element can also be appropriately adjusted.

[0053] In general formula (1), A is an organic molecule (containing an organic group or an organic cation, the same in this disclosure), an inorganic atom or molecule (containing an inorganic group or an inorganic cation, the same in this disclosure) or a combination thereof, B is a metal atom or molecule (containing a metal cation, the same in this disclosure), and X is a halogen atom or molecule, or a chalcogenide atom or molecule (containing a halide anion or a chalcogenide anion, the same in this disclosure). In general formula (1), the three Xs may be the same or different from each other.

[0054] 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.

[0055] Furthermore, as long as it is known that the top battery light absorption layer 114 has photoelectric conversion function and contains A, B, and X, it can be identified as a perovskite compound without confirming that it has a crystal structure. For example, it can be identified as having organic molecules, metal atoms, and halogen atoms as A, B, and X, or having inorganic atoms, metal atoms, and halogen atoms as A, B, and X.

[0056] In general formula (1), examples of organic molecules represented by A include alkylamines, alkylammonium compounds, and nitrogen-containing heterocyclic compounds. In perovskite compounds (1), the organic molecule represented by A can be only one organic molecule or two or more organic molecules.

[0057] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentanamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentanamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentanamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentanamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0058] Alkylammonium is the ionized form of the above-mentioned alkylamine. Examples of 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.

[0059] Examples of nitrogen-containing heterocyclic compounds include imidazoles, azoles, pyrroles, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, azoles, imidazolines, and zozoles. Nitrogen-containing heterocyclic compounds can be ionized compounds. Phenethylammonium is preferably used as an ionized nitrogen-containing heterocyclic compound.

[0060] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentamine, hexylammonium or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium or propylammonium, and even more preferably methylammonium.

[0061] 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 can 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 properties of perovskite compounds, lead or tin atoms are preferred as the metal atom represented by B. From the viewpoint of reducing lead content, tin atoms are preferred.

[0062] In general formula (1), the halogen atom represented by X can be, for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The chalcogen atom represented by X can be, for example, an oxygen atom, a sulfur atom, a selenium atom, and a tellurium atom. In perovskite compounds, the halogen atom or chalcogen atom represented by X can be one or more. From the viewpoint that perovskite compounds can utilize light in a wide wavelength range, the iodine atom is preferred as the halogen atom represented by X. In detail, it is preferred that at least one of the three X's represents an iodine atom, and more preferably that all three X's represent an iodine atom.

[0063] As a perovskite compound, a compound represented by the general formula "CH3NH3PbX3 (where X represents a halogen atom)" is preferred, and CH3NH3PbI3 is more preferred. By using a compound represented by the general formula "CH3NH3PbX3" (especially CH3NH3PbI3) as a 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.

[0064] As a method for forming the top solar cell light absorption layer 114 containing a perovskite compound, an example is a method of forming a film by coating a precursor solution obtained by dissolving a precursor compound of the perovskite compound in an organic solvent using a known method such as spin coating or bar coating.

[0065] (Top Battery Hole Transport Layer) The top battery hole transport layer 115 is a layer that transports holes generated in the top battery light absorption layer 114 to the intermediate electrode 13. The top battery hole transport layer 115 preferably also functions as an electron blocking layer to suppress the movement of electrons generated in the top battery light absorption layer 114 to the intermediate electrode 13.

[0066] The top battery hole transport layer 115 is constructed primarily of a hole transport material. Specifically, the top battery hole transport layer 115 preferably contains 70% by mass or more of a hole transport material, 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., Cu2O, NiO, ZnS), with spiro-OMeTAD being the most preferred.

[0067] Furthermore, as long as the top battery 11 has a photoelectric conversion function, it is obvious that the portion located on the hole transport side (or positive electrode side, which is the same in this disclosure) or within the top battery light absorption layer 114, which is closer to the hole transport side, is obvious, and it is not necessary to confirm a hole transport function that is actually difficult to confirm. That is, as long as the top battery 11 has a photoelectric conversion function, the layer located on the hole transport side or within the top battery light absorption layer 114, which is closer to the hole transport side and is made of a suitable material, can be regarded as the top battery hole transport layer 115.

[0068] (Intermediate Layer) In this embodiment, an intermediate electrode 13 is exemplified as the intermediate layer. The intermediate electrode 13 is an electrode that electrically connects the top cell and the bottom cell, and is configured such 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 conductive and transparent material, such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-fluorine-doped zinc oxide (AZO), indium zinc oxide (IZO), gallium-fluorine-doped zinc oxide (GZO), and other conductive and transparent materials. These can be used alone or in combination of two or more.

[0069] In addition, the intermediate layer is not limited to the intermediate electrode 13. Other well-known structures such as highly doped impurity doped layers, highly doped PN junction layers, and tunnel junction layers, which are disposed between the top and bottom cells in a series configuration, can also be used.

[0070] The intermediate layer can simply be a structure positioned between the top and bottom cells in a series-connected solar cell. As long as the solar cell functions as a solar cell, it is self-evident that such a structure functions as an intermediate layer, and there is no need to wait for confirmation of the intermediate layer's physical properties such as conductivity and transmittance. Furthermore, an intermediate layer is not mandatory; layers on the bottom cell side of the top cell and layers on the top cell side of the bottom cell, having the same structure as the intermediate layer, can replace it. As long as the series-connected solar cell with these top and bottom cells functions as a series-connected solar cell, it is self-evident that these layers can replace the intermediate layer, and there is no need to wait for confirmation of the physical properties of these layers such as conductivity and transmittance.

[0071] (Bottom Cell n-type Doped Layer, Bottom Cell Light Absorbing 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 adopt a configuration used in known silicon solar cells. For example, by adding dopants 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. By adding phosphorus, arsenic, or the like as dopants, the bottom cell n-type doped layer 121 can be formed, and by adding boron, gallium, or the like, the bottom cell p-type doped layer 123 can be formed.

[0072] Furthermore, when using a heterojunction silicon structure, for example, a non-monocrystalline silicon thin film such as amorphous silicon or microcrystalline silicon can be formed on a monocrystalline silicon substrate serving as the bottom cell light absorption layer 122, forming an n-type doped layer 121 and a p-type doped layer 123 for the bottom cell. Examples of materials for the silicon thin films used as the n-type doped layer 121 and the 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 can be used individually or in combination of two or more.

[0073] <Second Embodiment> FIG3 is a top view showing a portion of a photoelectric conversion module 100 using the photoelectric conversion element 10 of the second embodiment of the present disclosure. In the photoelectric conversion element 10 of this embodiment, except as described below, the same configuration as in the first embodiment can be adopted.

[0074] The photoelectric conversion element 10 of this embodiment is configured to have eight opening slots 14. The opening slots 14 formed on the top battery 11 are formed in a direction parallel to the interconnect 20, and the interconnect 20 is connected to each of the divided regions of the top battery 11, which is the same as in the first embodiment.

[0075] When the configuration is such that each interconnect 20 is connected to a divided region of the top battery 11, if the number of interconnects 20 on the top battery 11 is set to n, then the top battery 11 is divided by n-1 opening slots 14.

[0076] In the example shown in Figure 3, the photoelectric conversion element 10 is a half-size battery made of a 166mm square silicon wafer, and the width of the opening slot 14 is 2mm. When using this example to calculate the aperture ratio of the top battery 11, the calculation formula is as follows: Aperture ratio of the top battery = [width of opening slot 14] × [short side of battery] × [number of opening slots 14] ÷ ([long side of battery] × [short side of battery] - [area of ​​C-side (corner notch) of battery] × 2) = 2 × 83 × (9-1) ÷ (166 × 83 - 8.55 × 8.55 ÷ 2 × 2) = 9.69%

[0077] The aperture ratio of the top battery 11 can be adjusted by changing the width of the opening slot 14. As described above, since the preferred range of the aperture ratio of the top battery 11 varies depending on the band gap of the battery, a photoelectric conversion element 10 with high output can be obtained by adjusting its aperture ratio according to the band gap of the top battery 11.

[0078] <Third Embodiment> FIG4 is a top view showing a portion of a photoelectric conversion module 100 using the photoelectric conversion element 10 of the third embodiment of the present disclosure. In the photoelectric conversion element 10 of this embodiment, except as described below, the same configuration as in the first embodiment can be adopted.

[0079] The photoelectric conversion element 10 of this embodiment is configured to connect two interconnects 20 to each of the divided regions of the top battery 11. In other words, instead of providing opening slots 14 between all adjacent interconnects 20 as in the first and second embodiments, an opening slot 14 is provided every other one. In this configuration, since the interconnects 20 are provided in an equal number in each of the divided regions of the top battery 11, the current flowing through each interconnect 20 can be equalized. That is, the deterioration of current-voltage characteristics caused by forming opening slots 14 on the top battery 11 can be suppressed.

[0080] <Fourth Embodiment> FIG5 is a top view showing a portion of a photoelectric conversion module 100 using the photoelectric conversion element 10 of the fourth embodiment of the present disclosure. In the photoelectric conversion element 10 of this embodiment, except as described below, the same configuration as in the first embodiment can be adopted.

[0081] In this embodiment of the photoelectric conversion element 10, the opening slot 14 formed on the top battery 11 is formed in a direction parallel to the interconnect 20, similar to the first to third embodiments, but the opening slot 14 is configured not to extend to the end (long side) of the top battery 11. Thus, even if the opening slot 14 is not provided in a manner that divides the top battery 11 into multiple regions, the amount of light received by the top battery 11 decreases while the amount of light received by the bottom battery 12 increases, just as in the first embodiment. Therefore, in the photoelectric conversion element 10 of this embodiment, current matching between the top battery 11 and the bottom battery 12 can also be achieved.

[0082] Furthermore, according to the configuration of the opening groove 14 in this embodiment, even if the opening groove 14 is not formed to the end of the top cell 11, it has the same effect as dividing the top cell 11 into multiple regions by the opening groove 14. Therefore, the density of the current in the surface of the solar cell can also be kept uniform.

[0083] <Fifth Embodiment> FIG6 is a cross-sectional view showing the schematic configuration of the photoelectric conversion element 10 according to the fifth embodiment of the present disclosure. In the photoelectric conversion element 10 of this embodiment, except as described below, the same configuration as that of the first embodiment can be adopted.

[0084] In the photoelectric conversion element 10 of this embodiment, a segmented groove 1251 is formed on the back gate 125, and the back gate 125 is divided into a plurality of regions. The top battery 11 is divided into a plurality of regions by the opening groove 14, as in the first embodiment. The segmented regions in the back gate 125 correspond to the segmented regions in the surface gate 111 (top battery 11).

[0085] In the photoelectric conversion element 10 of this embodiment, the number of segmented regions in the surface gate 111 and the back gate 125 is the same, and the arrangement direction of the segmented regions in the surface gate 111 and the back gate 125 is the same. At this time, the segmented regions arranged in the same order along the arrangement direction by the surface gate 111 and the back gate 125 are designated as corresponding segmented regions to each other. The corresponding segmented regions overlap each other in at least a portion when viewed from above, and preferably completely overlap when viewed from above. Furthermore, "corresponding" here does not refer to a specific physical connection, but rather to a physical connection between adjacent elements, thus implying a relationship. That is, a certain constituent element (e.g., XA) in the first element 10A is physically connected to a constituent element (e.g., YB) of the second element 10B, which is an adjacent element, through a connecting member. When the first element 10A has a constituent element (e.g., YA) corresponding to constituent element YB, constituent element XA and constituent element YA are sometimes referred to as "corresponding". Here, for example, element XA refers to a segmented element of the surface gate 111, and elements YA and YB refer to a segmented element of the back gate 125.

[0086] According to this configuration, since the area collected by one interconnect 20 becomes a segmented region corresponding to the surface gate 111 and the back gate 125, the current flowing through each of the interconnects 20 can be more clearly equalized.

[0087] The embodiments disclosed herein are illustrative in all respects and are not the basis for limiting interpretation. Therefore, the technical scope of this disclosure is not limited to the above-described embodiments, but is defined based on the description in the claim. Furthermore, this includes all modifications within the scope and meaning equivalent to the claim.

[0088] [Note] This disclosure includes the following methods.

[0089] (Method 1) A photoelectric conversion element, which is a photoelectric conversion element in a series solar cell, includes: a top cell disposed on the light-receiving side; and a bottom cell disposed on the back side, wherein an opening groove is formed in the light-absorbing layer of the top cell, so that a portion of the light incident from the light-receiving side can be incident on the light-absorbing layer of the bottom cell without passing through the light-absorbing layer of the top cell.

[0090] (Method 2) In the photoelectric conversion element according to Method 1, the opening slot is formed in such a way that the top battery is divided into a plurality of regions.

[0091] (Method 3) In the photoelectric conversion element according to Method 1 or 2, the opening slot is formed such that a portion of the light incident from the light-receiving surface side can be incident on the bottom battery without passing through the top battery.

[0092] (Method 4) The photoelectric conversion element according to any one of Methods 1 to 3, wherein the top cell has a gate composed of a plurality of conductive members parallel to each other, an interconnect is provided on the top cell, the interconnect connecting the plurality of conductive members in the gate, and the opening slot is formed along a direction parallel to the interconnect.

[0093] (Method 5) The photoelectric conversion element according to any one of Methods 1 to 4, wherein the top battery has a light-absorbing layer containing a perovskite compound.

[0094] (Method 6) According to any one of Methods 1 to 5, the opening ratio of the top battery, calculated as the ratio of the opening area formed by the opening slot in the top battery to the area of ​​one surface of the bottom battery, is 3% or more and 20% or less. [Simplified Explanation of the Diagram]

[0016] FIG1 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a first embodiment of the present disclosure. FIG2 is a top view showing a portion of a photoelectric conversion module using the photoelectric conversion element of FIG1. ​​FIG3 is a top view showing a portion of a photoelectric conversion module using the photoelectric conversion element according to a second embodiment of the present disclosure. FIG4 is a top view showing a portion of a photoelectric conversion module using the photoelectric conversion element according to a third embodiment of the present disclosure. FIG5 is a top view showing a portion of a photoelectric conversion module using the photoelectric conversion element according to a fourth embodiment of the present disclosure. FIG6 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a fifth embodiment of the present disclosure. FIG7 is a cross-sectional view showing a schematic configuration of a conventional photoelectric conversion element for a series-connected solar cell. FIG8 is a graph showing the relationship between the band gap of the light-absorbing layer of the top cell in a series-connected solar cell and the photoelectric conversion efficiency. FIG9 is a graph showing the relationship between the aperture ratio of the top cell and the photoelectric conversion efficiency.

Claims

1. A photoelectric conversion element, which is a photoelectric conversion element in a series-connected solar cell, wherein, include: Top battery, which is positioned on the light-receiving side; The device includes a bottom battery disposed on the back side, and an opening groove formed in the light-absorbing layer of the top battery, which allows a portion of the light incident from the light-receiving surface to be incident on the light-absorbing layer of the bottom battery without passing through the light-absorbing layer of the top battery. The bottom battery has a back gate disposed on the back side, and the back gate has a segmented groove formed therein. The back gate is divided into a plurality of regions, and the segmented regions in the back gate correspond to the segmented regions in the surface gate of the top battery.

2. The photoelectric conversion element according to claim 1, wherein, The opening slot is formed in such a way that the top battery is divided into multiple regions.

3. The photoelectric conversion element according to claim 1 or 2, wherein, The opening slot is formed such that a portion of the light incident from the light-receiving surface can be incident on the bottom battery without passing through the top battery.

4. The photoelectric conversion element according to claim 1 or 2, wherein, The top battery has a gate composed of a plurality of parallel conductive components. An interconnect is provided on the top battery, the interconnect connecting the plurality of conductive components in the gate. The opening slot is formed along a direction parallel to the interconnect.

5. The photoelectric conversion element according to claim 1 or 2, wherein, The top battery has a light-absorbing layer containing a perovskite compound.

6. The photoelectric conversion element according to claim 1 or 2, wherein, The opening ratio of the top battery, calculated as the ratio of the opening area formed by the opening slot in the top battery to the area of ​​one surface of the bottom battery, is 3% or more and 20% or less.

Images