Photoelectric conversion element

Abstract

To realize low-cost photoelectric conversion elements. [Solution] The photoelectric conversion element (1) includes a top cell (10) disposed on the light-receiving surface side, a bottom cell (20) disposed on the back side, an upper electrode (31), and a lower electrode (32). The bottom cell has a first photoelectric conversion layer (23) containing silicon, a thin film silicon compound layer (24) located between the first photoelectric conversion layer and the lower electrode, an amorphous silicon layer (25) located between the thin film silicon compound layer and the lower electrode, an intrinsic amorphous semiconductor layer (22) located between the first photoelectric conversion layer and the top cell, and a conductive amorphous semiconductor layer (21) located between the conductive amorphous semiconductor layer and the top cell.

Description

[Technical Field]

[0001] The present disclosure relates to a photoelectric conversion element. [Background Art]

[0002] Patent Document 1 discloses a multi-junction photovoltaic device (photoelectric conversion element) including a first sub-cell disposed on a second sub-cell. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese National Publication of International Patent Application No. 2018-517304 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The photoelectric conversion element disclosed in Patent Document 1 has a problem that the manufacturing cost is increased. [Means for Solving the Problem]

[0005] In order to solve the above problem, a photoelectric conversion element according to one aspect of the present disclosure is a photoelectric conversion element for a tandem solar cell, and includes a top cell disposed on a light-receiving surface side, a bottom cell disposed on a back surface side, an upper electrode, and a lower electrode. The top cell has a second photoelectric conversion layer containing a perovskite compound, and the bottom cell includes a first photoelectric conversion layer containing silicon, a thin film silicon compound layer positioned between the first photoelectric conversion layer and the lower electrode, an amorphous silicon layer positioned between the thin film silicon compound layer and the lower electrode, an intrinsic amorphous semiconductor layer positioned between the first photoelectric conversion layer and the top cell, and a conductive amorphous semiconductor layer positioned between the intrinsic amorphous semiconductor layer and the top cell. [Effect of the Invention]

[0006] According to one aspect of this disclosure, a low-cost photoelectric conversion element can be realized. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view illustrating the configuration of a photoelectric conversion element according to Embodiment 1. [Figure 2] This is a diagram illustrating the method for manufacturing a photoelectric conversion element according to Embodiment 1. [Figure 3] This is a cross-sectional view illustrating the configuration of a photoelectric conversion element as an example of a comparative example. [Figure 4] This is a cross-sectional view illustrating the configuration of a photoelectric conversion element according to a modified example of Embodiment 1. [Figure 5] This is a cross-sectional view illustrating the configuration of a photoelectric conversion element according to Embodiment 2. [Figure 6] This is a cross-sectional view illustrating the configuration of a photoelectric conversion element according to a modified example of Embodiment 2. [Modes for carrying out the invention]

[0008] [Embodiment 1 (N / PVSK / PN / c-Si(n) / P)] An embodiment of this disclosure will be described in detail below. In the following description, "A to B" indicating a numerical range means "greater than or equal to A and less than or equal to B" unless otherwise specified.

[0009] (Photoelectric conversion element 1) Figure 1 is a cross-sectional view illustrating the configuration of a photoelectric conversion element 1 according to one embodiment of the present disclosure. The photoelectric conversion element 1 is a photoelectric conversion element in a tandem solar cell using a perovskite solar cell. A tandem solar cell means a solar cell in which part or all of the light LS (more specifically, light having a certain wavelength band) incident from the light-receiving surface side of the photoelectric conversion element is sequentially absorbed by two or more light-absorbing layers. In Figure 1, the upper surface of the photoelectric conversion element 1 is the light-receiving surface.

[0010] In terms of configuration, in this disclosure, a tandem solar cell may mean a solar cell in which two light-absorbing layers are provided in order from the light-receiving side to the back side of the photoelectric conversion element, starting from the light-receiving side. It is not necessary for the two light-absorbing layers to be completely superimposed when viewed from the light-receiving side; at least a portion must be superimposed. Furthermore, it is desirable that at least one light-absorbing layer is completely superimposed on the other. In other words, in this disclosure, a tandem solar cell is one in which some or all of the light (specifically, light having a certain wavelength band) incident from the light-receiving side of the photoelectric conversion element can pass through one light-absorbing layer and then enter the other light-absorbing layer. The light-absorbing layers do not need to be single layers; they may consist of multiple layers. Here, multiple layers can refer to, for example, a laminated structure consisting of PN junctions.

[0011] A light-absorbing layer is a layer that absorbs light incident on a photoelectric conversion element and generates electrons and holes. The fact that a light-absorbing layer absorbs light and generates electrons and holes is self-evident as long as the solar cell has the function of photoelectric conversion as a solar cell, and as long as the light-absorbing layer is made of appropriate materials, it is not necessary to confirm that it absorbs light and generates electron-hole pairs, which is extremely difficult to confirm.

[0012] As shown in Figure 1, the photoelectric conversion element 1 includes a top cell 10, a bottom cell 20, an upper electrode 31, and a lower electrode 32. In the photoelectric conversion element 1, the top cell 10 is located on the top side and the bottom cell 20 is located on the back side.

[0013] When using expressions meaning "up" or "down" to describe direction, "up" can be used to refer to the light-receiving surface of the photoelectric conversion element, and "down" can be used to refer to the back surface of the photoelectric conversion element. Unless otherwise specified, this should be understood. In other words, the light-receiving surface and the top side basically mean the same thing, and the back side and the bottom side also mean the same thing. Furthermore, in the case of a single-sided photoelectric conversion element, the light-receiving surface refers directly to the surface on which light enters the element. However, in the case of a double-sided photoelectric conversion element, either one of the surfaces can be considered the light-receiving surface, and if one surface is considered the light-receiving surface, the opposite surface can be considered the back surface. In other words, if the configuration of this disclosure is present when at least one of the surfaces is considered the light-receiving surface, it can be considered to fall within the technical scope of this disclosure. To put it another way, even if the configuration of this disclosure is not present when one of the surfaces is considered the light-receiving surface, if the configuration of this disclosure is present when the other surface is considered the light-receiving surface, it can be considered to fall within the technical scope of this disclosure.

[0014] (Top Cell 10) The top cell 10 is a perovskite solar cell. The top cell 10 has a second photoelectric conversion layer 13. The top cell 10 further has a surface transparent electrode 11, a top cell electron transport layer 12, and a top cell hole transport layer 14. These elements are located in the following order from the light-receiving surface: surface transparent electrode 11, top cell electron transport layer 12, second photoelectric conversion layer 13, and top cell hole transport layer 14.

[0015] In the present disclosure, the terms "transparent" and "light-transmitting" mean that a material transmits light. This does not exclude materials that slightly reflect or absorb light, and means that the relevant member is provided on the light-receiving surface side (including the portion where light is incident; the same applies hereinafter in the present disclosure) relative to the photoelectric conversion layer (either the first photoelectric conversion layer or the second photoelectric conversion layer) of the photoelectric conversion element, or on the light-receiving surface side relative to the light absorbing portion (for example, a perovskite compound) of the photoelectric conversion layer. Accordingly, a member provided at least on the aforementioned light-receiving surface side can be regarded as transparent. That is, a transparent electrode means an electrode provided on the light-receiving surface side of the photoelectric conversion element.

[0016] In addition, the terms "layer" and "film" do not define thickness or width, and include patterned or island-shaped members and members having portions with different thicknesses. Layers or films are preferably those having a substantially constant thickness. Unless otherwise specified, the terms "substantially" and "approximately" mean the range of manufacturing errors, and preferentially indicate that a variation of plus 15% and minus 15% of the numerical value is allowed.

[0017] The surface transparent electrode 11 is an electrode disposed on the surface of the photoelectric conversion element on the light-receiving surface side. The surface transparent electrode 11 is preferably a thin-film electrode having conductivity and light transmittance. Examples of the material for the surface transparent electrode 11 include conductive transparent materials such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). These materials may be used alone, or two or more types may be used in combination.

[0018] The top cell electron transport layer 12 is a layer that transports electrons generated in the second photoelectric conversion layer 13 to the surface transparent electrode 11. The top cell electron transport layer 12 preferably also functions as a hole blocking layer that suppresses migration of holes generated in the second photoelectric conversion layer 13 to the surface transparent electrode 11. Examples of materials for the top cell electron transport layer 12 include tin oxide, titanium oxide, and zinc oxide.

[0019] Provided that the photoelectric conversion element 1 has a photoelectric conversion function, it is self-evident that a portion located on the electron transport side relative to the second photoelectric conversion layer 13 (or on the negative electrode side, the same applies in the present disclosure) or on the electron transport side within the second photoelectric conversion layer 13 has an electron transport function, and confirmation of the electron transport function that is actually difficult to verify is not required. That is, provided that the photoelectric conversion element 1 has a photoelectric conversion function, a layer that is located on the electron transport side relative to the second photoelectric conversion layer 13 or on the electron transport side within the second photoelectric conversion layer 13 and is composed of an appropriate material can be regarded as the top-cell electron transport layer 12.

[0020] In addition, the top-cell electron transport layer 12 can also serve the function of the surface transparent electrode 11, and vice versa. Therefore, the photoelectric conversion element 1 does not need to have a configuration including both the surface transparent electrode 11 and the top-cell electron transport layer 12, and may have a configuration including only one of them, where one serves the function of the other.

[0021] The second photoelectric conversion layer 13 may be a layer containing a perovskite compound that is a photoelectric conversion material. The second photoelectric conversion layer 13 is a layer capable of absorbing at least part of light incident on the photoelectric conversion element 1 and generating electrons and holes. Among these, electrons move to the top-cell electron transport layer 12, and holes move to the top-cell hole transport layer 14. The second photoelectric conversion layer 13 may be composed of the perovskite compound alone, or may contain substances other than the perovskite compound.

[0022] The perovskite compound is composed of a compound represented by the general formula: ABX3···(1). Although the respective composition ratio is preferably 1:1:3, it does not necessarily have to be 1:1:3, and the content of each element may be appropriately adjusted up or down.

[0023] In general formula (1), A is an organic molecule (including an organic group or an organic cation, as is the case in this disclosure), an inorganic atom or molecule (including an inorganic group or an inorganic cation, as is the case in this disclosure), or a combination thereof; B is a metal atom or molecule (including a metal cation, as is the case in this disclosure); and X is a halogen atom or molecule or a chalcogen atom or molecule (including a halogen anion or a chalcogen anion, as is the case in this disclosure). In general formula (1), the three Xs may be the same or different from one another.

[0024] 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.

[0025] Furthermore, it is possible to determine that a perovskite compound is present if it is confirmed that the photoelectric conversion element 1 possesses a photoelectric conversion function and contains A, B, and X; confirmation of the presence of a crystalline structure is not required. For example, it is possible to determine if A, B, and X contain organic molecules, metal atoms, and halogen atoms (or chalcogen atoms; the same applies hereinafter), or if A, B, and X contain inorganic atoms, metal atoms, and halogen atoms. Moreover, as long as the photoelectric conversion element 1 possesses a photoelectric conversion function, it can be confirmed if the elements corresponding to A, B, and X are detected. For example, as organic molecules, molecules containing carbon, nitrogen, and hydrogen are preferable; therefore, it is sufficient if carbon, nitrogen, hydrogen, metal elements, and halogens or chalcogens are detected. Alternatively, it is sufficient if it contains A, B, and X to be considered a perovskite compound; for example, it is sufficient if it contains inorganic atoms, metal atoms, and halogen atoms. Furthermore, the presence of a perovskite compound can be confirmed by detecting elements corresponding to A, B, and X, as long as the photoelectric conversion element 1 has a photoelectric conversion function. For example, cesium or rubidium are preferred as inorganic atoms; therefore, it is sufficient if cesium or rubidium, a metallic element, and a halogen or chalcogen are detected.

[0026] The term "light-absorbing region" can refer to any portion that absorbs light (for example, a region containing a perovskite compound). If there are other light-absorbing regions besides the indicated light-absorbing region, they can be collectively described as a light-absorbing layer. In other words, the light-absorbing region can mean any portion of the light-absorbing layer. Furthermore, the light-absorbing layer can mean a collection of light-absorbing regions that exist discretely or continuously in a region mainly in a certain direction, having a thickness (similar to the definition of a "layer," it does not need to be constant, for example). In this embodiment, the light-absorbing region means a perovskite compound. However, this does not exclude the inclusion of materials other than perovskite compounds in the light-absorbing region.

[0027] Examples of organic molecules represented by A in general formula (1) include alkylamines, alkylammonium compounds, and nitrogen-containing heterocyclic compounds. In perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or it may be two or more types of organic molecules.

[0028] Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

[0029] Alkylammonium compounds are ionized compounds of the alkylamines mentioned above. Examples of alkylammonium compounds include methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, dimethylammonium, diethylammonium, dipropylammonium, dibutylammonium, dipentylammonium, dihexylammonium, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexylammonium, ethylmethylammonium, methylpropylammonium, butylmethylammonium, methylpentylammonium, hexylmethylammonium, ethylpropylammonium, and ethylbutylammonium.

[0030] Examples of nitrogen-containing heterocyclic compounds include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. Nitrogen-containing heterocyclic compounds may also be ionized. Phenethylammonium is preferred as an ionized nitrogen-containing heterocyclic compound.

[0031] In general formula (1), the organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium, or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium, or propylammonium, and even more preferably methylammonium.

[0032] In general formula (1), examples of metal atoms represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In perovskite compounds, the metal atom represented by B may be only one type of metal atom or two or more types of metal atoms. From the viewpoint of improving the light absorption and charge generation characteristics of perovskite compounds, lead atoms or tin atoms are preferred as the metal atom represented by B. From the viewpoint of reducing lead, tin atoms are preferred.

[0033] Examples of halogen atoms represented by X in general formula (1) include fluorine, chlorine, bromine, and iodine atoms. Examples of chalcogen atoms include oxygen, sulfur, selenium, and tellurium atoms. In a perovskite compound, the halogen atom or chalcogen atom represented by X may be one or two or more. From the viewpoint of enabling the perovskite compound to utilize light in a wide wavelength range, iodine is preferred as the halogen atom represented by X. More specifically, it is preferable that at least one of the three Xs represents an iodine atom, and it is more preferable that all three Xs represent iodine atoms.

[0034] As the perovskite compound, compounds represented by the general formula "CH3NH3PbX3 (where X represents a halogen atom)" are preferred, and CH3NH3PbI3 is more preferred. By using a compound represented by the general formula "CH3NH3PbX3" (especially CH3NH3PbI3) as the perovskite compound, electrons and holes can be generated more efficiently in the perovskite compound, and as a result, the photoelectric conversion efficiency of solar cells can be further improved.

[0035] As a method for forming the second photoelectric conversion layer 13 containing the perovskite compound, an example is to coat a precursor solution, obtained by dissolving a precursor compound of the perovskite compound in an organic solvent, using known methods such as spin coating or bar coating to form the film. Alternatively, the second photoelectric conversion layer 13 may be formed using a dry process such as vapor deposition or sputtering.

[0036] The top cell hole transport layer 14 is a layer that transports holes generated in the second photoelectric conversion layer 13 to the bottom cell 20. Preferably, the top cell hole transport layer 14 also functions as an electron blocking layer that suppresses the movement of electrons generated in the second photoelectric conversion layer 13 to the bottom cell 20.

[0037] The top cell hole transport layer 14 is composed mainly of a hole transport material. Specifically, the top cell hole transport layer 14 preferably contains 70% by mass or more of the hole transport material, and more preferably contains 85% by mass or more and 100% by mass or less. Examples of hole transport materials include P-type organic semiconductors, conductive polymers, metal oxides, metal sulfides (e.g., Cu2O, NiO, ZnS), and spiro-OMeTAD is preferred.

[0038] Furthermore, as long as the photoelectric conversion element 1 has a photoelectric conversion function, it is self-evident that the portion located on the hole transport side (or positive electrode side, similarly in this disclosure) of the second photoelectric conversion layer 13 or on the hole transport side within the second photoelectric conversion layer 13 has a hole transport function, and there is no need to verify the hole transport function, which is difficult to actually confirm. In other words, as long as the photoelectric conversion element 1 has a photoelectric conversion function, the layer located on the hole transport side of the second photoelectric conversion layer 13 or on the hole transport side within the second photoelectric conversion layer 13 and made of an appropriate material can be considered as the top cell hole transport layer 14.

[0039] (Bottom cell 20) The bottom cell 20 is a crystalline silicon solar cell. The bottom cell 20 has, in order from the light-receiving surface, a conductive amorphous semiconductor layer 21, an intrinsic amorphous semiconductor layer 22, a first photoelectric conversion layer 23, a thin-film silicon compound layer 24, and an amorphous silicon layer 25.

[0040] The first photoelectric conversion layer 23 is a layer that absorbs at least a portion of the light incident on the photoelectric conversion element 1 and generates electrons and holes. Of these, the electrons move to the intrinsic amorphous semiconductor layer 22, and the holes move to the thin film silicon compound layer 24. The first photoelectric conversion layer 23 can be a silicon-containing layer. For example, the first photoelectric conversion layer 23 is made of an n-type single crystal silicon substrate.

[0041] The thin-film silicon compound layer 24 transports holes generated in the first photoelectric conversion layer 23 to the amorphous silicon layer 25. The thin-film silicon compound layer 24 is located between the first photoelectric conversion layer 23 and the lower electrode 32. The thin-film silicon compound layer 24 may contain, for example, SiN, SiO, or SiO2.

[0042] In this context, a thin film refers to a film with a thickness in the range of 0.1 nm to 5 nm. Furthermore, the thin film is preferably in the range of 1 nm to 3 nm, and more preferably in the range of 1.5 nm to 2 nm. In particular, the thickness of the thin-film silicon compound layer 24 is preferably such that tunnel conduction is possible. For example, the thickness of the thin-film silicon compound layer 24 is preferably 0.1 nm to 2 nm.

[0043] The amorphous silicon layer 25 improves the passivation properties of the first photoelectric conversion layer 23. The amorphous silicon layer 25 is located between the thin film silicon compound layer 24 and the lower electrode 32. The amorphous silicon layer 25 may have a structure in which an amorphous silicon layer is doped with a dopant. The term "amorphous" means not in a single-crystal state, for example, a polycrystalline or amorphous state. The dopant may be, for example, boron or aluminum.

[0044] The amorphous silicon layer 25 is located on the opposite side of the photoelectric conversion element 1 from the light-receiving surface. Therefore, the influence of the light transmittance of the amorphous silicon layer 25 on the power generation performance of the photoelectric conversion element 1 is smaller than when the amorphous silicon layer 25 is located on the side of the photoelectric conversion element 1 from the light-receiving surface. For this reason, the amorphous silicon layer 25 may be formed thicker in the photoelectric conversion element 1 compared to when the amorphous silicon layer 25 is located on the side of the light-receiving surface. This improves the passivation properties of the first photoelectric conversion layer 23. As a result, recombination of electrons and holes in the first photoelectric conversion layer 23 is suppressed, and the efficiency of photoelectric conversion is improved.

[0045] The intrinsic amorphous semiconductor layer 22 is a layer that transports electrons generated in the first photoelectric conversion layer 23 to the conductive amorphous semiconductor layer 21. The intrinsic amorphous semiconductor layer 22 is located between the first photoelectric conversion layer 23 and the top cell 10. The intrinsic amorphous semiconductor layer 22 does not mean only a semiconductor layer without dopants, and does not exclude the presence of low concentrations of dopants. Here, for clarity, "low concentration" means a semiconductor layer with a dopant concentration smaller than that of the conductive amorphous semiconductor layer 21. Furthermore, it is preferable that the dopant concentration is two orders of magnitude smaller or more than that of the conductive amorphous semiconductor layer 21. Moreover, it is even more preferable that the dopant concentration is four orders of magnitude smaller or more than that of the conductive amorphous semiconductor layer 21. The intrinsic amorphous semiconductor layer 22 may be an amorphous semiconductor layer to which N-type dopants are added.

[0046] In this specification, "semiconductor" means a material having a certain band gap. A "semiconductor" typically includes silicon. That is, the semiconductor in the intrinsic amorphous semiconductor layer 22 may be silicon. The dopant may be, for example, phosphorus, antimony, or arsenic.

[0047] The conductive amorphous semiconductor layer 21 is a semiconductor layer containing dopants. The conductive amorphous semiconductor layer 21 is located between the intrinsic amorphous semiconductor layer 22 and the top cell 10. The conductive amorphous semiconductor layer 21 is in contact with the top cell hole transport layer 14. For example, the conductive amorphous semiconductor layer 21 may be an amorphous semiconductor layer with a higher dopant concentration compared to the intrinsic amorphous semiconductor layer 22. The semiconductor may be silicon, as in the example of the intrinsic amorphous semiconductor layer 22 described above.

[0048] The conductive amorphous semiconductor layer 21 and the intrinsic amorphous semiconductor layer 22 may contain silicon. The inclusion of silicon in the conductive amorphous semiconductor layer 21 and the intrinsic amorphous semiconductor layer 22 enables efficient power generation.

[0049] The silicon contained in the amorphous silicon layer 25 may be in a polycrystalline state. A polycrystalline state refers to a state in which grain boundaries can be observed on the surface. If grain boundaries cannot be observed, a polycrystalline state may refer to a state in which, when electron diffraction analysis is performed using a TEM (Tunnel Electron Microscope), the diffraction pattern forms a concentric ring pattern. However, the amorphous silicon layer 25 does not necessarily have to be in a polycrystalline state; for example, it may be in an amorphous state.

[0050] The semiconductors contained in the conductive amorphous semiconductor layer 21 and the intrinsically amorphous semiconductor layer 22 may be in an amorphous state. An amorphous state refers to a state in which no grain boundaries can be observed on the surface. Furthermore, an amorphous state may also refer to a state in which, when electron diffraction analysis is performed by TEM, the diffraction pattern forms a concentric halo pattern. However, the semiconductors contained in the conductive amorphous semiconductor layer 21 and the intrinsically amorphous semiconductor layer 22 do not necessarily have to be in an amorphous state; for example, they may be in a polycrystalline state.

[0051] In addition, in the configuration of the photoelectric conversion element 1 described above, electrons and holes may be reversed. For example, the components of the top cell 10 may be arranged in the following order from the light-receiving surface: surface transparent electrode 11, top cell hole transport layer 14, second photoelectric conversion layer 13, and top cell electron transport layer 12. In this case, the intrinsic amorphous semiconductor layer 22 may be a layer of P-type amorphous semiconductor.

[0052] (Upper electrode 31 and lower electrode 32) The upper electrode 31 and lower electrode 32 are electrodes for extracting power from the photoelectric conversion element 1. For simplicity, only two upper electrodes 31 and two lower electrodes 32 are shown in Figure 1. However, in an actual photoelectric conversion element 1, the upper electrodes 31 and lower electrodes 32 extend in a comb-like manner across the entire surface of the photoelectric conversion element 1, both the light-receiving surface and the opposite surface. The upper electrodes 31 and lower electrodes 32 may be formed from materials commonly used for electrodes.

[0053] (Method for manufacturing photoelectric conversion element 1) Figure 2 is a diagram illustrating the manufacturing method of the photoelectric conversion element 1. In Figure 2, intermediate stages in the manufacturing method of the photoelectric conversion element 1 are shown by reference numerals 201 to 204.

[0054] When manufacturing the photoelectric conversion element 1, first, a first photoelectric conversion layer 23 is prepared as shown by reference numeral 201. Next, a thin film silicon compound layer 24 is formed as shown by reference numeral 202, and then an amorphous silicon layer 25 is formed as shown by reference numeral 203. In this state, the thin film silicon compound layer 24 and the amorphous silicon layer 25 are heat-treated at a high temperature and cleaned with hydrofluoric acid. After that, the other parts are formed sequentially to form the top cell 10 and the bottom cell 20 as shown by reference numeral 204. Furthermore, by forming the upper electrode 31 on the top cell 10 and the lower electrode 32 on the bottom cell 20, the photoelectric conversion element 1 shown in Figure 1 is manufactured.

[0055] In the manufacturing method of the photoelectric conversion element 1, high-temperature processes are required only in the formation of the thin-film silicon compound layer 24 and the amorphous silicon layer 25. For example, when forming a polycrystalline amorphous silicon layer 25 using LPCVD (Low Pressure Chemical Vapor Deposition), the layer is amorphous at the time of LPCVD formation. Subsequently, it is necessary to heat the amorphous silicon layer 25 to about 800°C to change it from an amorphous state to a polycrystalline state. Furthermore, high-temperature processing is also required for ion implantation and diffusion into the amorphous silicon layer 25, which has become polycrystalline.

[0056] In the manufacturing method shown in Figure 2, the thin-film silicon compound layer 24 and the amorphous silicon layer 25, which require high-temperature processes, are formed in advance, eliminating the need for high-temperature processes in subsequent steps. Therefore, the manufacturing cost of the photoelectric conversion element 1 can be reduced.

[0057] (Advantages of the tandem type) Figure 3 is a cross-sectional view illustrating the configuration of a photoelectric conversion element 1A as a comparative example. Photoelectric conversion element 1A differs from photoelectric conversion element 1 in that it does not have a top cell 10, i.e., it is not a tandem type. Therefore, in photoelectric conversion element 1A, the upper electrode 31 is directly connected to the conductive amorphous semiconductor layer 21 of the bottom cell 20.

[0058] In the photoelectric conversion element 1A, the lower electrode 32 is directly connected to the first photoelectric conversion layer 23. Direct connection of the lower electrode 32 to the first photoelectric conversion layer 23 requires a high-temperature process. On the other hand, the conductive amorphous semiconductor layer 21 is temperature sensitive and easily damaged. Therefore, in order to directly connect the upper electrode 31 to the conductive amorphous semiconductor layer 21, as in the photoelectric conversion element 1A, a low-temperature process separate from the high-temperature process used to directly connect the lower electrode 32 to the first photoelectric conversion layer 23 is required. Printing is an example of a low-temperature process, but it is not limited to this. Thus, because the lower electrode 32 and the upper electrode 31 need to be formed using separate processes, the manufacturing cost of the photoelectric conversion element 1A is high.

[0059] On the other hand, in the photoelectric conversion element 1 described above, the upper electrode 31 is connected to the top cell 10 rather than the first photoelectric conversion layer 23. Therefore, it is not necessary to form the upper electrode 31 using a low-temperature process. Consequently, the photoelectric conversion element 1 having a bottom cell 20 and a top cell 10 can be manufactured without undergoing the extra process required to create a structure with a bottom cell 20 and a top cell 10.

[0060] (modified version) Figure 4 is a cross-sectional view illustrating the configuration of a modified photoelectric element 1B according to Embodiment 1. As shown in Figure 4, the photoelectric element 1B includes an intermediate connection layer 40 in addition to the configuration of the photoelectric element 1. The intermediate connection layer 40 is inserted between the top cell hole transport layer 14 and the conductive amorphous semiconductor layer 21. The intermediate connection layer 40 is a layer that electrically connects the top cell 10 and the bottom cell 20. The intermediate connection layer 40 is preferably made of a material that is conductive and transparent. As an example of the material for the intermediate connection layer 40, a transparent conductive film such as ITO or IWO can be selected. It should be noted that the conductivity of the intermediate connection layer 40 is self-evident as long as the photoelectric element 1B has the function of photoelectric conversion as a solar cell, and as long as it is properly arranged, it is not necessary to confirm that it can conduct electricity.

[0061] [Embodiment 2 (p / PVSK / np / c-Si(p) / n)] Another embodiment of the present disclosure is described below. For simplicity, components that can be used in the same way as in Embodiment 1 are given the same names in the description. Therefore, there is no duplication of explanations that are the same as in Embodiment 1, and the explanations in Embodiment 1 above may be applied mutatis mutandis unless they contradict each other.

[0062] Figure 5 is a cross-sectional view illustrating the configuration of the photoelectric conversion element 2 according to Embodiment 2. As shown in Figure 5, the photoelectric conversion element 2 differs from the photoelectric conversion element 1 in that it includes a top cell 10A and a bottom cell 20A instead of a top cell 10 and a bottom cell 20.

[0063] (Top Cell 10A) The top cell 10A is a perovskite solar cell. The top cell 10A has a second photoelectric conversion layer 13. The top cell 10A further has a surface transparent electrode 11, a top cell electron transport layer 12, and a top cell hole transport layer 14. In the top cell 10A, these elements are located in the following order from the light-receiving surface: surface transparent electrode 11, top cell hole transport layer 14, second photoelectric conversion layer 13, and top cell electron transport layer 12.

[0064] (Bottom cell 20A) The bottom cell 20A is a crystalline silicon solar cell. The bottom cell 20A has, in order from the light-receiving surface, a conductive amorphous semiconductor layer 21A, an intrinsic amorphous semiconductor layer 22A, a first photoelectric conversion layer 23A, a thin-film silicon compound layer 24A, and an amorphous silicon layer 25A.

[0065] The first photoelectric conversion layer 23A is a layer that absorbs at least a portion of the light incident on the photoelectric conversion element 1 and generates electrons and holes. Of these, the holes move to the intrinsic amorphous semiconductor layer 22A, and the electrons move to the thin film silicon compound layer 24A. The first photoelectric conversion layer 23A can be a silicon-containing layer. The first photoelectric conversion layer 23A is made of, for example, a p-type single crystal silicon substrate.

[0066] The amorphous silicon layer 25A improves the passivation properties of the first photoelectric conversion layer 23A. The amorphous silicon layer 25A is located between the thin film silicon compound layer 24A and the lower electrode 32. The amorphous silicon layer 25A may have a structure in which an amorphous silicon layer is doped with a dopant. The term "amorphous" means not in a single-crystal state, for example, a polycrystalline or amorphous state. The dopant may be, for example, phosphorus, antimony, or arsenic.

[0067] The intrinsic amorphous semiconductor layer 22A is a layer that transports holes generated in the first photoelectric conversion layer 23A to the conductive amorphous semiconductor layer 21A. The intrinsic amorphous semiconductor layer 22A is located between the first photoelectric conversion layer 23A and the top cell 10. The intrinsic amorphous semiconductor layer 22A may be an amorphous semiconductor layer doped with a P-type dopant.

[0068] The conductive amorphous semiconductor layer 21A is a semiconductor layer containing dopants. The conductive amorphous semiconductor layer 21A is located between the intrinsic amorphous semiconductor layer 22A and the top cell 10. The conductive amorphous semiconductor layer 21A is in contact with the top cell electron transport layer 12. For example, the conductive amorphous semiconductor layer 21A may be an amorphous semiconductor layer with a higher dopant concentration compared to the intrinsic amorphous semiconductor layer 22A. The semiconductor may be silicon, as in the example of the intrinsic amorphous semiconductor layer 22 described above.

[0069] (modified version) Figure 6 is a cross-sectional view illustrating the configuration of a photoelectric conversion element 2A according to a modified example of Embodiment 2. As shown in Figure 6, the photoelectric conversion element 2A includes an intermediate connection layer 40 in addition to the configuration of the photoelectric conversion element 2. The intermediate connection layer 40 is inserted between the top cell electron transport layer 12 and the conductive amorphous semiconductor layer 21A. The function and material of the intermediate connection layer 40 are as described in the modified example of Embodiment 1.

[0070] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0071] [Note] (Aspect 1) A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving surface side, a bottom cell located on the back side, an upper electrode, and a lower electrode. The top cell has a second photoelectric conversion layer containing a perovskite compound, The bottom cell is A first photoelectric conversion layer containing silicon, A thin film silicon compound layer located between the first photoelectric conversion layer and the lower electrode, An amorphous silicon layer located between the thin film silicon compound layer and the lower electrode, An intrinsic amorphous semiconductor layer located between the first photoelectric conversion layer and the top cell, A conductive amorphous semiconductor layer located between the intrinsic amorphous semiconductor layer and the top cell, A photoelectric conversion element having the following characteristics.

[0072] (Aspect 2) The photoelectric conversion element according to embodiment 1, characterized in that the intrinsic amorphous semiconductor layer and the conductive amorphous semiconductor layer contain silicon.

[0073] (Aspect 3) The photoelectric conversion element according to embodiment 1 or 2, wherein the silicon contained in the amorphous silicon layer is in a polycrystalline state.

[0074] (Aspect 4) The photoelectric conversion element according to any one of embodiments 1 to 3, wherein the semiconductor contained in the intrinsic amorphous semiconductor layer and the conductive amorphous semiconductor layer is in an amorphous state. [Explanation of Symbols]

[0075] 1, 1A, 1B, 2, 2A Photoelectric conversion element 10, 10A top cell 13. Second Photoelectric Conversion Layer 20, 20A bottom cell 21, 21A Conductive amorphous semiconductor layer 22, 22A Intrinsic amorphous semiconductor layer 23, 23A First photoelectric conversion layer 24, 24A Thin film silicon compound layer 25, 25A Amorphous silicon layer 31 Upper electrode 32 Lower electrode

Claims

1. A photoelectric conversion element in a tandem solar cell, It includes a top cell located on the light-receiving surface side, a bottom cell located on the back side, an upper electrode, and a lower electrode. The top cell has a second photoelectric conversion layer containing a perovskite compound, The bottom cell is A first photoelectric conversion layer containing silicon, A thin film silicon compound layer located between the first photoelectric conversion layer and the lower electrode, An amorphous silicon layer located between the thin film silicon compound layer and the lower electrode, An intrinsic amorphous semiconductor layer located between the first photoelectric conversion layer and the top cell, A conductive amorphous semiconductor layer located between the intrinsic amorphous semiconductor layer and the top cell, A photoelectric conversion element having the following characteristics.

2. The photoelectric conversion element according to claim 1, characterized in that the intrinsic amorphous semiconductor layer and the conductive amorphous semiconductor layer contain silicon.

3. The photoelectric conversion element according to claim 1, wherein the silicon contained in the amorphous silicon layer is in a polycrystalline state.

4. The photoelectric conversion element according to claim 1, wherein the semiconductors contained in the intrinsic amorphous semiconductor layer and the conductive amorphous semiconductor layer are in an amorphous state.

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