Photoelectric conversion element

Abstract

This invention provides a photoelectric conversion element that, in a series-connected solar cell, can reduce the shear stress between the top unit light-absorbing layer and the bottom unit light-absorbing layer caused by temperature changes, thereby suppressing peeling between the two light-absorbing layers. The photoelectric conversion element is configured to include a top unit (11) disposed on the light-receiving side and a bottom unit (12) disposed on the back side. The top unit light-absorbing layer (114) is divided into a plurality of regions by a gap (14) formed on the top unit light-absorbing layer (114).

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 with stacked light-absorbing layers (photoelectric conversion layers) of different types have been proposed. As an example of a tandem solar cell, a perovskite / silicon solar cell (e.g., Patent Document 1) can be cited. Previous Art Documents Patent Documents

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

[0004] In tandem solar cells, due to the stacking of different types of light-absorbing layers, the coefficients of thermal expansion differ between the light-absorbing layers of the top and bottom units. If the temperature of the tandem solar cell changes, shear stress is generated in the region between the light-absorbing layers of the top and bottom units due to this difference in thermal expansion coefficients. Repeated temperature changes may lead to delamination between these two light-absorbing layers. This problem is particularly pronounced in tandem solar cells with perovskite / silicon solar cells, perovskite / compound crystal solar cells, and other types of solar cells that utilize a perovskite compound light-absorbing layer (perovskite layer). This is because: the perovskite layer is prone to differences in thermal expansion coefficients with other light-absorbing layers; and the bonding strength between the layers constituting the unit (especially the bonding strength of the perovskite layer and the bonding strength of the self-assembled monolayer acting as a hole transport layer) is often weak.

[0005] Figure 6 is a cross-sectional view showing a schematic configuration of a conventional photoelectric conversion element 50 in a tandem solar cell. As shown in Figure 6, the photoelectric conversion element 50 is configured by stacking top units 51 and 52, with top unit 51 disposed on the upper side and bottom unit 52 disposed on the lower side. Here, top unit 51 is a perovskite solar cell, and bottom unit 52 is a crystalline silicon solar cell.

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

[0007] Furthermore, regarding direction, when using expressions indicating "up" or "down," the expression "up" can be used for the light-receiving side of the component, and the expression "down" can be used for the back side of the component, unless otherwise specified. That is, it can be understood that, basically, the light-receiving side and the up side have the same meaning, and the back side and the down side also have the same meaning.

[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, any one side can be considered as the light-receiving surface, and when any one side is considered as the light-receiving surface, the opposite side can be considered as the back side. That is, when considering at least any one side as the light-receiving surface, as long as it has the structure of this disclosure, it can be considered to fall within the technical scope of this disclosure. In other words, even if one side does not have the structure of this disclosure when considered as the light-receiving surface, but has the structure of this disclosure when considered as the light-receiving surface, it can still be considered to fall within the technical scope of this disclosure.

[0009] In the photoelectric conversion element 50, shear stress is particularly prone to occur at the interface between the top unit light absorption layer 514 and the bottom unit 52. Due to this shear stress, peeling occurs from the weaker adhesive forces between the layers constituting the unit, and the unit itself may be damaged with repeated temperature changes. In Figure 6, S′ represents the region where shear stress is prone to occur (hereinafter referred to as the shear stress generation region). The wider the shear stress generation region S′, the greater the shear stress and the easier it is for peeling to occur.

[0010] This disclosure was made in view of the above-mentioned problems, and its object is to provide a photoelectric conversion element in a series solar cell that can reduce the shear stress generated between the light absorption layer of the top unit and the light absorption layer of the bottom unit due to temperature changes, thereby suppressing the peeling between the two light absorption layers.

[0011] To solve the above problems, the following photoelectric conversion element is provided. The photoelectric conversion element of the present invention is a photoelectric conversion element in a series solar cell, including a top unit disposed on the light-receiving side and a bottom unit disposed on the back side, wherein the light-absorbing layer of the top unit is divided into a plurality of regions by a gap formed on the light-absorbing layer of the top unit.

[0012] According to the photoelectric conversion element disclosed herein, in a series-connected solar cell, the shear stress generated between the light absorption layer of the top unit and the light absorption layer of the bottom unit due to temperature changes, etc., can be reduced, thereby suppressing the peeling between the two light absorption layers and achieving excellent results.

Implementation Method

[0014] [First Embodiment] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. FIG1 shows an embodiment of the present disclosure and is a cross-sectional view showing a schematic configuration of the photoelectric conversion element 10.

[0015] Furthermore, in this disclosure, a series-connected solar cell refers to a solar cell configured such that part or all of the light (specifically, light of a certain wavelength) incident from the light-receiving side of the photoelectric conversion element can be absorbed sequentially by two or more light-absorbing layers.

[0016] In terms of structure, in this disclosure, a series-connected solar cell can also refer 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. Furthermore, viewed from the light-receiving side, the two light-absorbing layers do not need to completely overlap; at least a partial overlap is sufficient. Additionally, it is preferable that at least one light-absorbing layer completely overlaps with the other light-absorbing layer. That is, in this disclosure, a series-connected solar cell refers to a solar cell 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 mentioned here do not need to be single-layered; they can be multi-layered. Multi-layered structures, for example, can refer to a stacked structure composed of PN junctions.

[0017] Furthermore, the light-absorbing layer refers to a layer that can absorb light incident on the photoelectric conversion element and generate electrons and holes. The absorption of light and the generation of electrons and holes by the light-absorbing layer is a self-evident premise for a solar cell to function as a solar cell. As long as the light-absorbing layer is made of suitable materials, there is no need to confirm whether it absorbs light that is extremely difficult to observe and generates electron-hole pairs.

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

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

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

[0021] Further, 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 unit 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 unit 12).

[0022] The photoelectric conversion element 10 shown in FIG1 can be manufactured by forming the required layers of the top unit 11 on the bottom unit 12. However, the manufacturing process of the photoelectric conversion element 10 of this disclosure is not particularly limited. For example, the photoelectric conversion element 10 can also be manufactured by other methods such as bonding the top unit 11 and the bottom unit 12 together after manufacturing them separately.

[0023] The photoelectric conversion element 10 shown in Figure 1 has a configuration where the current flows from top to bottom, but the direction of current flow is not limited to this, and it can also be configured where the current flows from bottom to top. In the case of the configuration where the current flows from bottom to top, in the top unit 11, the positions of the top unit electron transport layer 113 and the top unit hole transport layer 115 are interchanged, and in the bottom unit 12, the positions of the bottom unit n-type doped layer 121 and the bottom unit p-type doped layer 123 are interchanged. In addition, the type of doped layer (bottom unit n-type doped layer 121 or bottom unit p-type doped layer 123) in the bottom unit 12 is not particularly limited, and 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.

[0024] As shown in FIG1, in the photoelectric conversion element 10, the top unit light absorption layer 114 is divided into a plurality of regions. In this embodiment, the gap 14 is opened on the upper side of the top unit 11, forming an opening groove that extends from the surface grid electrode 111 to the hole transport layer 115 of the top unit. Through this opening groove, the top unit 11 is divided into a plurality of regions. The gap 14, which is the opening groove, can be formed by removing a portion of the top unit 11 using a scribing method (laser scribing or mechanical scribing). Alternatively, by using a mask when forming the top unit 11, the top unit 11 can be prevented from being formed in the region that will become the gap 14 from the beginning.

[0025] That is, in the photoelectric conversion element 10, the interface on the bottom unit 12 side of the top unit light absorption layer 114 is divided into multiple regions. In other words, as shown in FIG1, the shear stress generation region S in the photoelectric conversion element 10 is divided into multiple regions. Therefore, compared with the shear stress generation region S' in the conventional photoelectric conversion element 50 shown in FIG6, the shear stress generated in the divided region of the shear stress generation region S is smaller. Furthermore, the overall shear stress generated between the top unit light absorption layer 114 and the bottom unit light absorption layer 122 is smaller, and peeling between the two light absorption layers can be suppressed.

[0026] Furthermore, in this embodiment, a gap 14 is formed as an opening slot penetrating to the top unit hole transport layer 115. However, when the gap 14 is formed as an opening slot, it is acceptable as long as it penetrates at least from the upper side of the top unit 11 to the top unit light absorption layer 114. Specifically, as illustrated later in the second embodiment, the gap 14, as an opening slot, can penetrate to the top unit light absorption layer 114, but not the top unit hole transport layer 115. Further, the gap 14 can also be configured not to open on the upper side of the top unit 11. Specifically, as illustrated later in the third embodiment, the gap 14 can also be a structure that divides the top unit light absorption layer 114 into a plurality of regions. The reason for this is that as long as the shear stress generation region S is divided into a plurality of regions, the generated shear stress can be reduced, thereby suppressing peeling between the top unit light absorption layer 114 and the bottom unit light absorption layer 122. Given the ease of unit fabrication, the gap 14 is preferably formed as an opening groove that divides the top unit 11 into a plurality of regions, as in this embodiment.

[0027] Figure 2 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. Furthermore, the photoelectric conversion module 100 may also be a photoelectric conversion array obtained by connecting multiple columns of photoelectric conversion strings in parallel. Figure 2 illustrates two adjacent photoelectric conversion elements 10 in a photoelectric conversion string. Here, the photoelectric conversion element 10 on the upper side of the Y direction in the figure is designated as the first element 10A, and the photoelectric conversion element 10 on the lower side of the Y direction in the figure is designated as the second element 10B. Furthermore, the cross-sectional view in Figure 1 is a cross-sectional view of the photoelectric conversion element 10 shown in Figure 2 cut off from plane AA.

[0028] 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 grid electrode 111 of the first element 10A, and the back interconnect 20B is connected to the back grid electrode 125 of the second element 10B. Furthermore, although the term interconnect is used as an example here for the purpose of describing a connection component, it is not limited to interconnects, but broadly refers to components capable of electrically connecting elements to each other.

[0029] As shown in FIG2, in the bottom unit 12 of the photoelectric conversion element 10, a silicon wafer with a generally rectangular shape (for example, a silicon wafer obtained by halving a generally square silicon wafer) can be used. The shape of the bottom unit 12 is not limited to this. When the bottom unit 12 is generally rectangular, the gap 14 is preferably formed along a direction perpendicular to the long side of the bottom unit 12. In the state where the gap 14 is not provided, the long side of the bottom unit 12 is the long side of the shear stress generation region S. Therefore, by dividing the shear stress generation region S along a direction perpendicular to this long side, the shear stress caused by temperature changes, etc., can be effectively reduced. Furthermore, peeling between the top unit light absorption layer 114 and the bottom unit light absorption layer 122 can be suppressed.

[0030] As shown in FIG2, the gaps 14 are formed along a direction parallel to the interconnects 20. That is, all the gaps 14 in the photoelectric conversion element 10 are formed in parallel. In FIG2, although a configuration in which gaps 14 as two opening slots are provided on the photoelectric conversion element 10 is illustrated, the number of gaps 14 is not particularly limited. In addition, the number of interconnects 20 is not particularly limited. For example, if the gaps 14 are provided in such a way that the top unit light absorption layer 114 is divided between all adjacent interconnects 20, and the number of interconnects 20 on the top unit 11 is set to n, then n-1 gaps 14 can be formed along a direction parallel to the interconnects 20.

[0031] By forming a gap 14 along a direction parallel to the interconnect 20, the area without the top unit light absorption layer 114 does not overlap with the area where the interconnect 20 is located. Therefore, the power collection of the interconnect 20 to the unit is prevented from being blocked by the gap 14, and the influence of setting the gap 14 on the battery characteristics can be minimized.

[0032] In addition, by forming the gap 14 along the direction parallel to the interconnect 20, an area that can receive light without the light absorption layer 114 of the top unit can be effectively provided on the bottom unit 12, which has the advantage that the current collection efficiency of the interconnect 20 will not be reduced.

[0033] In the top unit 11 of the photoelectric conversion element 10, each segmented region is connected to at least one interconnect 20. In this embodiment, one interconnect 20 is connected to one segmented region of the top unit 11 (i.e., one segmented region of the top unit light absorption layer 114), but two or more interconnects 20 may be connected to one segmented region. In other words, the gap 14 may not be provided in such a way that it divides the top unit light absorption layer 114 between all adjacent interconnects 20, but rather the gap 14 may be provided in such a way that it divides the top unit light absorption layer 114 between every other adjacent interconnect 20.

[0034] Furthermore, in this embodiment, an intermediate electrode 13 is provided on the bottom unit 12. However, as a variation of this embodiment, a configuration in which no intermediate electrode 13 is provided between the top unit 11 and the bottom unit 12 (a configuration in which the top unit 11 and the bottom unit 12 are directly connected) can be included.

[0035] Hereinafter, the structure of each layer in the photoelectric conversion element 10 will be described as an example. However, since the materials and film formation methods of each layer in the photoelectric conversion element 10 can be applied using known technologies, the structure of each layer that can be applied to this embodiment is not limited to this example. That is, as long as it has the function of being a photoelectric conversion element in a series solar cell, layers that can be omitted may be omitted, layers other than those described below may be included, and a certain layer may also have the functions of other layers.

[0036] (Surface Grid Electrode, Back Grid Electrode) The surface grid electrode 111 and the back grid electrode 125 are composed of a plurality of parallel conductive components. These conductive components extend in a first direction (the X direction shown in Figures 1 and 2) and are arranged parallel to each other in a second direction (the Y direction shown in Figures 1 and 2) with intervals between them. The plurality of conductive components in the surface grid electrode 111 (back grid electrode 125) are connected via an interconnect 20 or a grid electrode disposed at the lower part of the interconnect 20. Specifically, the interconnect 20 extends along the second direction and is configured orthogonal to the plurality of conductive components. Since the second direction is along the short side of the photoelectric conversion element 10, the resistance of the interconnect 20 can be reduced by extending along this direction.

[0037] The surface grid electrode 111 (back grid electrode 125) is also referred to as a finger electrode, and the interconnect 20 is also referred to as a busbar electrode. The material of the conductive components is not particularly limited, but examples include metals such as silver, copper, and aluminum. The conductive components in the surface grid electrode 111 (back grid electrode 125) are narrower than the width of the interconnect 20, and are configured such that light enters the interior of the photoelectric conversion element 10 through the gaps between adjacent conductive components. Furthermore, since the back grid electrode 125 is located on the opposite side of the light-receiving surface, it can also be configured to be opaque.

[0038] (Surface transparent electrode, back transparent electrode) The surface 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). They can be used individually or in combination. Furthermore, since the back transparent electrode 124 is located on the opposite side of the light-receiving surface, it can also be constructed to be opaque.

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

[0040] As long as the top unit 11 has photoelectric conversion function, it is self-evident that the electron transmission side (or negative electrode side, the same meaning in this disclosure) of the top unit light absorption layer 114 or the portion of the electron transmission side within the top unit light absorption layer 114 has electron transmission function, and there is no need to confirm the electron transmission function that is difficult to confirm in practice. As long as the top unit 11 has photoelectric conversion function, the electron transmission side of the top unit light absorption layer 114 or the electron transmission side within the top unit light absorption layer 114, and the layer made of appropriate material, can all be regarded as the top unit electron transmission layer 113.

[0041] In addition, the top unit 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 unit electron transport layer 113, or it may have only one of the two functions.

[0042] (Top Unit Light Absorbing Layer) The top unit light absorbing layer 114 may be a layer containing a perovskite compound as a photoelectric conversion material. The top unit light absorbing layer 114 is a layer capable of absorbing at least a portion of the light incident on the photoelectric conversion element 10 to generate electrons and holes. Electrons move to the top unit electron transport layer 113, and holes move to the top unit hole transport layer 115. The top unit light absorbing layer 114 may be composed solely of a perovskite compound, or it may contain substances other than a perovskite compound.

[0043] The perovskite compounds are composed of compounds represented by the general formula: ABX₃…(1). However, the preferred composition ratio is 1:1:3, but it may not be 1:1:3, and the content of each element may vary appropriately.

[0044] In general formula (1), A is an organic molecule (including organic groups or organic cations, which have the same meaning in this disclosure), an inorganic atom or molecule (including inorganic groups or inorganic cations, which have the same meaning in this disclosure), or a combination thereof; B is a metal atom or molecule (including metal cations, which have the same meaning in this disclosure); X is a halogen atom or molecule, or a chalcogenide atom or molecule (including halide anions or chalcogenide anions, which have the same meaning in this disclosure). In general formula (1), the three Xs can be the same or different from each other.

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

[0046] Furthermore, as long as it is known that the top unit light absorption layer 114 has photoelectric conversion function and contains A, B and X, it can be identified as a perovskite compound without confirming whether it has a crystal structure. For example, it can be identified as long as it is known that it contains organic molecules, metal atoms and halogen atoms as A, B and X, or contains inorganic atoms, metal atoms and halogen atoms as A, B and X.

[0047] In general formula (1), the organic molecule represented by A can be, for example, alkylamines, alkylammonium compounds, and nitrogen-containing heterocyclic compounds. In perovskite compound (1), the organic molecule represented by A can be only one organic molecule or can be two or more organic molecules.

[0048] 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.

[0049] Alkylammonium is an 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.

[0050] Examples of nitrogen-containing heterocyclic compounds include imidazoles, azoles, pyrroles, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, aziridines, imidazolines, and zozoles. Nitrogen-containing heterocyclic compounds can also be ionized compounds. Phenethylammonium is preferably used as an ionized nitrogen-containing heterocyclic compound.

[0051] 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, ethylammonium or propylammonium, and even more preferably methylammonium.

[0052] In general formula (1), the metal atom represented by B can be, for example, 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 atom. 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.

[0053] 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 sulfur atom can be, for example, an oxygen atom, a sulfur atom, a selenium atom, and a tellurium atom. In the perovskite compound, the halogen atom or chalcogenide atom represented by X can be one or more. From the viewpoint of enabling the perovskite compound to utilize a wide range of light, 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.

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

[0055] As a method for forming the upper battery 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.

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

[0057] The top unit hole transport layer 115 is configured to use a hole transport material as the main material. Specifically, the top unit hole transport layer 115 preferably contains 70% or more of a hole transport material by mass, and more preferably contains 85% or more and 100% or less of a hole transport material by mass. 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.

[0058] Furthermore, as long as the top unit 11 has photoelectric conversion function, it is self-evident that the portion located on the hole transmission side (or positive electrode side, the same meaning in this disclosure) of the top unit light absorption layer 114 or the portion within the top unit light absorption layer 114 has hole transmission function, and there is no need to confirm the hole transmission function, which is difficult to confirm in practice. That is, as long as the top unit 11 has photoelectric conversion function, the layer located on the hole transmission side of the top unit light absorption layer 114 or the hole transmission side within the top unit light absorption layer 114, and made of a suitable material, can be regarded as the top unit hole transmission layer 115.

[0059] (Intermediate Layer) In this embodiment, an intermediate electrode 13 is exemplified as an intermediate layer. The intermediate electrode 13 is an electrode that electrically connects the top unit and the bottom unit, and is configured such that light not absorbed by the top unit 11 can reach the bottom unit 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-doped zinc oxide (AZO), indium zinc oxide (IZO), gallium-doped zinc oxide (GZO), and other conductive and transparent materials. They can be used alone or in combination of two or more.

[0060] As an intermediate layer, it is not limited to the intermediate electrode 13. Other highly doped impurity doped layers, highly doped PN junction layers, tunnel junction layers, etc., can also be used in the structure between the known series-type top and bottom cells.

[0061] The intermediate layer can simply be a structure disposed between the top and bottom units of 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; 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 necessarily required. As long as the layers on the bottom unit side of the top unit and the layers on the top unit side of the bottom unit have the same structure as the intermediate layer, they can replace the intermediate layer. As long as the series-connected solar cell with these layers functions as a series-connected solar cell, it is self-evident that these layers replace the intermediate layer; there is no need to wait for confirmation of the physical properties of these layers such as conductivity and transmittance.

[0062] (Bottom unit n-type doped layer, bottom unit light-absorbing layer, bottom unit p-type doped layer) The bottom unit n-type doped layer 121, bottom unit light-absorbing layer 122, and bottom unit p-type doped layer 123 can adopt the configuration used in known silicon solar cells. For example, by adding dopants to the surface of a crystalline silicon substrate, the bottom unit n-type doped layer 121 can be formed on one side of the bottom unit light-absorbing layer 122, which serves as the crystalline silicon substrate, and the bottom unit p-type doped layer 123 can be formed on the other side. By adding phosphorus, arsenic, or the like as dopants, the bottom unit n-type doped layer 121 can be formed, and by adding boron, gallium, or the like, the bottom unit p-type doped layer 123 can be formed.

[0063] Furthermore, when using a heterojunction silicon structure, for example, the following configuration can be adopted: A non-monocrystalline silicon thin film, such as amorphous silicon or microcrystalline silicon, is deposited on a monocrystalline silicon substrate serving as the bottom unit light-absorbing layer 122 to form the bottom unit n-type doped layer 121 and the bottom unit p-type doped layer 123. Examples of materials for the silicon thin films used as the bottom unit n-type doped layer 121 and the bottom unit 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 germanide. They can be used individually or in combination.

[0064] [Second Embodiment] FIG3 is a cross-sectional view showing a schematic configuration of the photoelectric conversion element 10 according to the second embodiment of the present disclosure. In the photoelectric conversion element 10 according to this embodiment, except as described below, the same configuration as in the first embodiment may be adopted.

[0065] In the photoelectric conversion element 10 according to this embodiment, the gap 14, which is an opening slot on the upper side of the top unit 11, is configured to penetrate to the top unit light absorption layer 114 but not to penetrate the top unit hole transport layer 115. Even with this configuration, since the gap 14 divides the top unit light absorption layer 114 into multiple regions, the shear stress generated between the top unit light absorption layer 114 and the bottom unit light absorption layer 122 is reduced, thereby suppressing peeling between the top unit light absorption layer 114 and the bottom unit light absorption layer 122.

[0066] [Third Embodiment] FIG4 is a cross-sectional view showing a schematic configuration of the photoelectric conversion element 10 according to the third embodiment of the present disclosure. In the photoelectric conversion element 10 according to this embodiment, except as described below, the same configuration as in the first embodiment may be adopted.

[0067] In the photoelectric conversion element 10 according to this embodiment, the gap 14 is formed as a gap located inside the top unit 11. In this example, it is configured such that only the top unit light absorption layer 114 is divided into a plurality of regions. The gap 14 can be formed by using a mask when forming the top cell light absorption layer 114 so that the area that would originally be the gap 14 is not formed in the top cell light absorption layer 114 from the beginning. Alternatively, it can be formed by removing the portion up to the top unit absorption layer 114 from the top side of the top unit 11 using a scribing method (laser scribing or mechanical scribing), and then refilling the layer other than the top unit light absorption layer 114.

[0068] Even with such a structure, since the gap 14 divides the top unit light absorption layer 114 into multiple regions, the shear stress generated between the top unit light absorption layer 114 and the bottom unit light absorption layer 122 will be reduced, thereby suppressing the peeling between the top unit light absorption layer 114 and the bottom unit light absorption layer 122.

[0069] [Fourth Embodiment] FIG5 is a cross-sectional view showing the schematic configuration of the photoelectric conversion element 10 according to the fourth embodiment of the present disclosure. In the first to third embodiments, a 2-junction type photoelectric conversion element 10 with two overlapping light absorption layers is shown, but in this embodiment, a 3-junction type photoelectric conversion element 10 with three overlapping light absorption layers is shown. In addition, in this disclosure, 2-junction type means that the number of light absorption layers capable of sequentially absorbing light in a series solar cell is two, and the description of the configuration of the light absorption layer can be applied to the description of a series solar cell. Similarly, 3-junction type means that the number of light absorption layers capable of sequentially absorbing light in a series solar cell is three, and the description of the configuration of the light absorption layer can be applied to the description of a series solar cell. Furthermore, the term "junction" used here is not "junction" in the literal sense, but is a term conventionally used to indicate the number of light absorption layers in a series solar cell, so "junction" can be understood as "light absorption layer".

[0070] The photoelectric conversion element 10 in FIG5 is configured to have an intermediate unit 15 stacked in addition to the top unit 11 and the bottom unit 12. Specifically, the top unit 11 is located on the top side, the bottom unit 12 is located on the back side, and the intermediate unit 15 is located between the top unit 11 and the bottom unit 12. The top unit 11 and the bottom unit 12 in this embodiment can be configured in the same way as the top unit 11 and the bottom unit 12 in the first to third embodiments. In addition, as an intermediate layer, an intermediate electrode 131 is provided between the top unit 11 and the intermediate unit 15, and an intermediate electrode 132 is provided between the intermediate unit 15 and the bottom unit 12. The intermediate electrodes 131 and 132 can be configured in the same way as the intermediate layer or the intermediate electrode 13 in the first to third embodiments.

[0071] The intermediate unit 15, from the top side, sequentially comprises an intermediate unit electron transport layer 151, an intermediate unit light absorption layer 152, and an intermediate unit hole transport layer 153. The intermediate unit 15 is the same as the top unit 11, being a perovskite solar cell, but preferably at least a portion of its material differs from that of the top unit 11, and preferably the wavelength of the light after photoelectric conversion is different from that of the top unit 11. That is, more specifically, it is preferable that the wavelengths of light absorbed in the top unit light absorption layer 114 and the intermediate unit light absorption layer 152 are staggered. In particular, when the wavelength of light absorbed by the intermediate unit light absorption layer 152 is more biased towards a longer wavelength than that absorbed by the top unit light absorption layer 114, the photoelectric conversion efficiency of the element can be further improved.

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

[0073] In the photoelectric conversion element 10 according to this embodiment, the number of segmented regions in the top unit light absorption layer 114 and the middle unit light absorption layer 152 is the same, and the arrangement direction of the segmented regions in the top unit light absorption layer 114 and the middle unit light absorption layer 152 is the same. At this time, in the top unit light absorption layer 114 and the middle unit light absorption layer 152, the segmented regions that are arranged in the same order along the arrangement direction are regarded as corresponding segmented regions. Between the corresponding segmented regions, it is sufficient that there is at least a partial overlap between them when viewed from above. In this case, it can be said that "the segmented regions of the top unit light absorption layer 114 and the segmented regions of the middle unit light absorption layer 152 correspond to each other". Furthermore, it is preferable that the corresponding segmented regions completely overlap each other when viewed from above.

[0074] As with the photoelectric conversion element 10 according to this embodiment, as long as a gap 14 is formed in the upper side of the top unit 11 as an opening slot that extends at least to the light absorption layer 152 of the middle unit, then the corresponding segmented regions will inevitably overlap at least partially when viewed from above. Furthermore, if the gap 14, which is the opening slot, is formed along a direction perpendicular to the upper surface of the top unit 11 (i.e., the Z direction shown in FIG. 5), then it can be said that the corresponding segmented regions completely overlap when viewed from above.

[0075] Even in such a 3-bonded photoelectric conversion element 10, since the top unit light absorption layer 114 and the middle unit light absorption layer 152 are each divided into multiple regions by the gap portion 14, peeling can be suppressed between the top unit light absorption layer 114 and the bottom unit light absorption layer 122 (for example, the middle unit 15 side interface of the top unit light absorption layer 114 and the bottom unit 12 side interface of the middle unit light absorption layer 152).

[0076] This embodiment is an example of applying the 2-bonded photoelectric conversion element 10 of the first embodiment to a 3-bonded type. However, as a variation of this embodiment, it may include examples of applying the 2-bonded photoelectric conversion element 10 of the second and third embodiments to a 3-bonded type. That is, it may be configured such that the gap portion 14, which is an opening slot on the upper side of the top unit 11, extends through to the light absorption layer 152 of the intermediate unit, but does not extend through the hole transport layer 153 of the intermediate unit. Furthermore, the gap portion 14 may not be an opening slot, but may be configured as a gap located inside the top unit 11 and inside the intermediate unit 15.

[0077] The embodiments disclosed herein are merely examples in all respects and are not intended to be limiting. Therefore, the technical scope of this disclosure is not limited to the above embodiments, but is defined based on the claims. Furthermore, it also includes all modifications that have the same meaning and scope as the claims.

[0078] [Note] This disclosure includes the following methods.

[0079] (Method 1) A photoelectric conversion element, which is a photoelectric conversion element in a series solar cell, wherein it includes a top unit disposed on the light-receiving side and a bottom unit disposed on the back side, and the light-absorbing layer of the top unit is divided into a plurality of regions by a gap formed on the light-absorbing layer of the top unit.

[0080] (Method 2) The photoelectric conversion element according to Method 1, wherein the gap is formed along a direction perpendicular to the long side of the bottom unit.

[0081] (Method 3) The photoelectric conversion element according to Method 1 or Method 2, wherein the top unit has a grid electrode composed of a plurality of mutually parallel conductive components, an interconnect connected to the plurality of conductive components in the grid electrode is provided on the top unit, and the gap is formed along a direction parallel to the interconnect.

[0082] (Method 4) The photoelectric conversion element according to any one of Methods 1 to 3, wherein the void portion is formed as a groove extending at least from the upper side of the top unit to the light absorption layer of the top unit.

[0083] (Scheme 5) The photoelectric conversion element according to any one of Schemes 1 to 4, wherein the light-absorbing layer of the top unit comprises a perovskite compound.

[0084] (Method 6) The photoelectric conversion element according to any one of Methods 1 to 5, wherein it includes an intermediate unit disposed between the top unit and the bottom unit, the light absorption layer of the intermediate unit is divided into a plurality of regions, and the divided regions of the light absorption layer of the top unit correspond to the divided regions of the light absorption layer of the intermediate unit. [Simplified Explanation of the Diagram]

[0013] 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 in FIG1. ​​FIG3 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a second embodiment of the present disclosure. FIG4 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a third embodiment of the present disclosure. FIG5 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to a fourth embodiment of the present disclosure. FIG6 is a cross-sectional view showing a schematic configuration of a conventional photoelectric conversion element in a tandem solar cell.

Claims

1. A photoelectric conversion element, which is a photoelectric conversion element in a series-connected solar cell, wherein, The device includes a top unit disposed on the light-receiving side and a bottom unit disposed on the back side. The light-absorbing layer of the top unit is divided into multiple regions by a gap formed on the light-absorbing layer of the top unit. The gap is formed along a direction perpendicular to the long side of the bottom unit. The top unit has a grid electrode composed of a multiple parallel conductive members. An interconnect is provided on the top unit, and the interconnect connects the multiple conductive members in the grid electrode. The gap is formed along a direction parallel to the interconnect.

2. A photoelectric conversion element, which is a photoelectric conversion element in a series-connected solar cell, wherein, It includes a top unit disposed on the light-receiving side and a bottom unit disposed on the back side. The light-absorbing layer of the top unit is divided into multiple regions by a gap formed on the light-absorbing layer of the top unit. The gap is formed by extending continuously from one side edge to the other side edge along a direction perpendicular to the long side of the bottom unit.

3. The photoelectric conversion element according to claim 1 or claim 2, wherein, The aforementioned top unit has a hole transport layer located on the back side of the light absorption layer of the aforementioned top unit. The aforementioned gap is formed as a groove that opens on the light-receiving side of the aforementioned top unit. The aforementioned groove penetrates the light absorption layer of the aforementioned top unit but does not penetrate the aforementioned hole transport layer.

4. The photoelectric conversion element according to claim 1 or claim 2, wherein, The aforementioned top unit has a surface transparent electrode located on the light-receiving side of the light-absorbing layer of the aforementioned top unit, and the aforementioned void portion has at least the aforementioned surface transparent electrode on the light-receiving side, thereby placing the aforementioned void portion inside the aforementioned top unit.

5. The photoelectric conversion element according to claim 1 or claim 2, wherein, The aforementioned gap is formed as a groove that extends at least from the top side of the aforementioned top unit to the light-absorbing layer of the aforementioned top unit.

6. The photoelectric conversion element according to claim 1 or claim 2, wherein, The light-absorbing layer of the aforementioned top unit contains a perovskite compound.

7. The photoelectric conversion element according to claim 1 or claim 2, wherein, It includes an intermediate unit disposed between the aforementioned top unit and the aforementioned bottom unit. The light absorption layer of the aforementioned intermediate unit is divided into multiple regions, and the divided regions of the light absorption layer of the aforementioned top unit correspond to the divided regions of the light absorption layer of the aforementioned intermediate unit.

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