Solar cell element, solar cell module, and method for manufacturing solar cell element

Abstract

According to one embodiment, a solar cell element is provided with: a first electrode section (106); a photoelectric conversion unit (104); and a first carrier transport unit (105). The first carrier transport section (105) is positioned between the first electrode section (106) and the photoelectric conversion section (104). The first carrier transport section (105) has: a first surface (CF1) that is in contact with the photoelectric conversion section (104); and a second surface (CF2) that is in contact with the first electrode part (106). In the first carrier transport section (105), a first energy level (EL1), which is an energy level that occupies the highest molecular orbital in a first interface region (Ab1) along the first surface (CF1), is smaller than a second energy level (EL2), which is an energy level that occupies the highest molecular orbital in a second interface region (Ab2) along the second surface (CF2).

Description

[0001] Cross-references of related applications

[0002] This application claims priority from Japanese application No. 2022-141521 (filed on September 6, 2022), the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a solar cell element, a solar cell module and a method for manufacturing a solar cell element. Background Art

[0004] Patent Document 1 describes a technique related to the energy level of an electron transport layer in a solar cell element. In recent years, there has been an increasing demand for improved power generation efficiency in solar cell elements and solar cell modules.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-31990 Summary of the invention

[0008] One embodiment of a solar cell element comprises: a first electrode portion; a photoelectric conversion portion; and a first carrier transport portion, the first carrier transport portion being located between the first electrode portion and the photoelectric conversion portion. The first carrier transport portion comprises: a first surface, the first surface being in contact with the photoelectric conversion portion; and a second surface, the second surface being in contact with the first electrode portion. In the first carrier transport portion, the energy level of the highest occupied molecular orbital in a first interface region along the first surface, i.e., a first energy level, is smaller than the energy level of the highest occupied molecular orbital in a second interface region along the second surface, i.e., a second energy level.

[0009] A solar cell element in one embodiment comprises: a first electrode portion; a photoelectric conversion portion; and a first carrier transport portion, the first carrier transport portion being located between the first electrode portion and the photoelectric conversion portion. The first carrier transport portion comprises: a first surface, the first surface being in contact with the photoelectric conversion portion; and a second surface, the second surface being in contact with the first electrode portion. In the first carrier transport portion, a carrier density in a first interface region along the first surface is greater than a carrier density in a second interface region along the second surface.

[0010] A solar cell module in one embodiment includes: a first electrode portion; a photoelectric conversion portion; and a first carrier transport portion, the first carrier transport portion being located between the first electrode portion and the photoelectric conversion portion. The first carrier transport portion includes: a first surface, the first surface being in contact with the photoelectric conversion portion; and a second surface, the second surface being in contact with the first electrode portion. In the first carrier transport portion, the energy level of the highest occupied molecular orbital in a first interface region along the first surface, i.e., a first energy level, is smaller than the energy level of the highest occupied molecular orbital in a second interface region along the second surface, i.e., a second energy level.

[0011] One mode of a method for manufacturing a solar cell element includes: a first step of forming a photoelectric conversion unit; a second step of forming a first carrier transport unit on the photoelectric conversion unit; and a third step of forming a first electrode unit on the first carrier transport unit. The second step includes a second A step, a second B step, and a second C step. In the second A step, a first layer is formed on the photoelectric conversion unit. In the second B step, a second layer is formed on the first layer. In the second C step, the first layer and the second layer are heated to diffuse a dopant contained in the first layer into the second layer, thereby generating the first carrier transport unit from the first layer and the second layer. The first layer has a higher dopant concentration than the second layer. The second layer has a lower dopant concentration than the first layer, or the second layer does not contain a dopant. The second layer contains a semiconductor material constituting the first carrier transport unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram schematically showing a first example of the cross-sectional structure of the solar cell element according to the first embodiment.

[0013] Figure 2 This is an energy band diagram showing a first example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the first embodiment.

[0014] Figure 3 It is a diagram schematically showing a second example of the cross-sectional structure of the solar cell element according to the first embodiment.

[0015] Figure 4 This is an energy band diagram showing a second example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the first embodiment.

[0016] Figure 5 It is a diagram schematically showing a third example of the cross-sectional structure of the solar cell element according to the first embodiment.

[0017] Figure 6 This is an energy band diagram showing a third example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the first embodiment.

[0018] Figure 7 It is a diagram schematically showing a fourth example of the cross-sectional structure of the solar cell element according to the first embodiment.

[0019] Figure 8 This is an energy band diagram showing a fourth example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the first embodiment.

[0020] Fig. 9 This is a flowchart showing an example of the flow of the method for manufacturing the solar cell element according to the first embodiment.

[0021] Fig.10 This is a diagram schematically showing an example of a cross-sectional structure of a solar cell module according to the first embodiment.

[0022] Fig.11 It is a diagram schematically showing a first example of the cross-sectional structure of the solar cell element according to the second embodiment.

[0023] Fig.12 This is an energy band diagram showing a first example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the second embodiment.

[0024] Fig.13 This is a flowchart showing an example of the flow of the method for manufacturing a solar cell element according to the second embodiment.

[0025] Fig.14 It is a diagram schematically showing a second example of the cross-sectional structure of the solar cell element according to the second embodiment.

[0026] Fig.15 This is an energy band diagram showing a second example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the second embodiment.

[0027] Fig.16 It is a diagram schematically showing a third example of the cross-sectional structure of the solar cell element according to the second embodiment.

[0028] Fig.17This is an energy band diagram showing a third example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the second embodiment.

[0029] Fig.18 It is a diagram schematically showing a fourth example of the cross-sectional structure of the solar cell element according to the second embodiment.

[0030] Fig.19 This is an energy band diagram showing a fourth example of the energy level relationship among the first electrode portion, the first carrier transport portion, the photoelectric conversion portion, and the second carrier transport portion of the solar cell element according to the second embodiment. DETAILED DESCRIPTION

[0031] For example, there is a solar cell element having a structure in which a first electrode portion, a first carrier transport portion for transporting holes, a photoelectric conversion portion, a second carrier transport portion for transporting electrons, and a second electrode portion are stacked in the order described. Typically, the Fermi level and the energy level of the highest occupied molecular orbital (HOMO) in the first carrier transport portion (hereinafter also referred to as the HOMO level) are constant or approximately constant in the thickness direction of the first carrier transport portion.

[0032] For solar cell elements, for example, the viewpoint of reducing energy loss caused by an energy barrier (hereinafter also referred to as an energy barrier) generated by the contact between a semiconductor and an electrode such as a metal or the contact between semiconductors is considered. From this viewpoint, ideally, the Fermi level in the first electrode portion, the Fermi level or the energy level of the highest occupied molecular orbital (HOMO level) in the first carrier transport portion, and the energy level of the valence band maximum (VBM) in the photoelectric conversion portion (hereinafter also referred to as the VBM level) or the energy level of the highest occupied molecular orbital (HOMO level) are considered to be consistent.

[0033] However, sometimes these energy levels cannot be made consistent. In this case, it is considered to reduce the difference in energy levels at the interface between the first electrode unit and the first carrier transport unit and the difference in energy levels at the interface between the first carrier transport unit and the photoelectric conversion unit. Here, the Fermi level and HOMO level in the first carrier transport unit are set to be below the Fermi level in the first electrode unit and above the VBM level or HOMO level in the photoelectric conversion unit.

[0034] Here, it is considered to increase the photoelectromotive force in the solar cell element to improve the conversion efficiency of the solar cell element. The photoelectromotive force is determined by the difference between the Fermi level of the material of the second carrier transport part and the Fermi level of the material of the first carrier transport part, assuming that the second carrier transport part, the photoelectric conversion part, the first carrier transport part, and the first electrode part are not connected. Therefore, in order to increase the photoelectromotive force in the solar cell element, it is considered to reduce the Fermi level and HOMO level of the material of the first carrier transport part to make it close to the VBM level or HOMO level of the material of the photoelectric conversion part.

[0035] However, when the Fermi level and HOMO level of the material of the first carrier transporting part are reduced, the difference between the Fermi level and HOMO level of the material of the first carrier transporting part and the Fermi level of the material of the first electrode part becomes larger. As a result, in the solar cell element, the energy barrier at the interface between the first carrier transporting part and the first electrode part can become larger. As a result, the power generation efficiency in the solar cell element is reduced.

[0036] In addition, in the solar cell element, in order to reduce the energy barrier at the interface between the first carrier transport part and the first electrode part, it is considered to make the Fermi level and HOMO level of the material of the first carrier transport part close to the Fermi level of the material of the first electrode part. In this case, the difference between the Fermi level of the material of the second carrier transport part and the Fermi level of the material of the first carrier transport part can be reduced. Therefore, the photoelectromotive force in the solar cell element is reduced.

[0037] In summary, usually, the Fermi level and HOMO level in the first carrier transport section have a constant or substantially constant distribution in the thickness direction of the first carrier transport section. Therefore, it is difficult to balance the increase in the photoelectromotive force of the solar cell element and the reduction in energy loss caused by the energy barrier at the interface between the first carrier transport section and the first electrode section. Therefore, there is still room for improvement in terms of improving the power generation efficiency of the solar cell element and the solar cell module.

[0038] Therefore, the inventors of the present invention have created a technology capable of improving the power generation efficiency of a solar cell element with respect to a solar cell element and a solar cell module.

[0039] In this regard, various embodiments are described below with reference to the accompanying drawings. In the accompanying drawings, parts having the same or substantially the same structure and function are marked with the same reference numerals. Therefore, repeated descriptions are omitted in the following description. The accompanying drawings are schematically shown. Figure 1 , Figure 3 , Figure 5 , Figure 7 , Fig.10 , Fig.11 , Fig.14 , Fig.16 as well as Fig.18 , the right-handed XYZ coordinate system is marked. In the XYZ coordinate system, the normal direction of the first element surface F1 of the solar cell element 10, 40 is the +Z direction. A direction along the first element surface F1 is the +X direction. The direction along the first element surface F1, that is, the direction orthogonal to the +X direction and the +Z direction, is the +Y direction.

[0040] <1. First embodiment>

[0041] <1-1. Solar cell element 10>

[0042] Reference Figures 1 to 8 A solar cell element 10 according to the first embodiment will be described. Figure 1 As shown, the solar cell element 10 has a surface (also referred to as a first element surface) F1 on which the main incident light is incident and a surface (also referred to as a second element surface) F2 located on the opposite side of the first element surface F1. In the first embodiment, the first element surface F1 faces the +Z direction. The second element surface F2 faces the -Z direction. For example, the +Z direction is set to the direction toward the sun at the zenith.

[0043] like Figure 1 As shown in the figure, the solar cell element 10 includes a first electrode portion 106, a first carrier transport portion 105, a photoelectric conversion portion 104, a second carrier transport portion 103, a second electrode portion 102, and a substrate portion 101. In the first embodiment, the second electrode portion 102, the second carrier transport portion 103, the photoelectric conversion portion 104, the first carrier transport portion 105, and the first electrode portion 106 are stacked in the order described above and arranged on the substrate portion 101. Therefore, the first carrier transport portion 105 is located between the first electrode portion 106 and the photoelectric conversion portion 104.

[0044] It should be noted that, although not shown in the figure, an anti-reflection film may be arranged on the surface of the solar cell element 10. The anti-reflection film may be, for example, an insulating film composed of silicon nitride or the like. In addition, although not shown in the figure, a passivation film may be arranged between the solar cell element 10 and the anti-reflection film. The passivation film may be, for example, a thin film composed of an oxide such as aluminum oxide or a nitride or the like.

[0045] <1-1-1. Substrate part 101>

[0046] The substrate portion 101 is, for example, an insulating substrate having light transmittance. The substrate portion 101 is, for example, light transmittance to a specific wavelength region. The specific wavelength region includes, for example, a wavelength region of light that the photoelectric conversion portion 104 can absorb and perform photoelectric conversion. Specifically, the specific wavelength region may include, for example, a wavelength region of visible light of about 400 nanometers (nm) to 700 nm and a wavelength region of infrared light of about 700 nm to 1200 nm. Thus, for example, light irradiated to the first element surface F1 can pass through the substrate portion 101 in a manner toward the photoelectric conversion portion 104. Here, for example, if the specific wavelength region includes a wavelength of light with a high irradiation intensity constituting sunlight, the power generation efficiency of the solar cell element 10 can be improved. The material of the substrate portion 101 is, for example, glass, acrylic acid, or polycarbonate. As the shape of the substrate portion 101, for example, a flat plate, a sheet, or a film is used. The thickness of the substrate portion 101 is, for example, about 0.01 millimeters (mm) to 5 mm.

[0047] <1-1-2. Second Electrode Section 102 >

[0048] The second electrode portion 102 is located on the substrate portion 101. The second electrode portion 102 is located on the second element plane F2 side of the substrate portion 101. In other words, the second electrode portion 102 is located on the −Z direction side of the substrate portion 101.

[0049] The second electrode unit 102 can collect carriers generated by photoelectric conversion when light is irradiated to the photoelectric conversion unit 104 described later. The second electrode unit 102 can, for example, function as an electrode (also referred to as a negative electrode) that collects electrons as carriers. The second electrode unit 102 can be formed on the substrate unit 101 by a vacuum process such as sputtering.

[0050] As a material for the second electrode portion 102, a transparent conductive oxide (Transparent Conductive Oxide: TCO) having light transmittance to light in a specific wavelength range is applied. TCO, for example, is not particularly limited, but may include indium tin oxide (Indium Tin Oxide: ITO), aluminum-doped zinc oxide (Al-doped Zinc Oxide: AZO), boron-doped zinc oxide (Boron-doped Zinc Oxide: BZO), gallium-doped zinc oxide (Gallium-doped Zinc Oxide: GZO), fluorine-doped tin oxide (Fluorine-doped Tin Oxide: FTO), antimony-doped Tin Oxide (Antimony-doped Tin Oxide: ATO), titanium-doped Indium Oxide (TiO), indium zinc oxide (Indium Zinc Oxide: IZO), indium gallium zinc oxide (Indium Gallium Zinc Oxide: GZO), and the like. Oxides such as SnO2:IGZO), tantalum-doped tin oxide (SnO2:Ta), niobium-doped tin oxide (SnO2:Nb), tungsten-doped tin oxide (SnO2:W), molybdenum-doped tin oxide (SnO2:Mo), fluorine-doped tin oxide (SnO2:F) or hydrogen-doped indium oxide (Hydrogen-doped Indium Oxide:IOH). The second electrode portion 102 can be composed of a film of a transparent conductive oxide. The film of the transparent conductive oxide can be a stacked film having a plurality of films. For example, the plurality of films can be films of the above-mentioned oxides, respectively. In addition, in addition to the films of the above-mentioned oxides, the plurality of films can also be films of oxides such as tin oxide containing a dopant. As the dopant, one or more elements selected from the group consisting of indium (In), silicon (Si), germanium (Ge), titanium (Ti), copper (Cu), antimony (Sb), niobium (Nb), fluorine (F), tantalum (Ta), tungsten (W), molybdenum (Mo), bromine (Br), iodine (I) and chlorine (Cl) can be used.

[0051] <1-1-3. Second Carrier Transporting Section 103 >

[0052] The second carrier transporting portion 103 is located on the second electrode portion 102. The second carrier transporting portion 103 is located on the second element plane F2 side of the second electrode portion 102. In other words, the second carrier transporting portion 103 is located on the -Z direction side of the second electrode portion 102.

[0053] The second carrier transporting section 103 may be made of, for example, an inorganic semiconductor (also referred to as an inorganic semiconductor) having a higher resistance than the second electrode section 102 . This makes it difficult for the second electrode section 102 to come into electrical contact with the photoelectric conversion section 104 .

[0054] In the first embodiment, the material of the inorganic semiconductor may be, for example, a semiconductor having an n-type conductivity (also referred to as an n-type semiconductor). In this case, the second carrier transport unit 103 may function as, for example, a so-called hole blocking layer and an electron transport layer (ETL). The electron transport layer may, for example, collect and output electrons.

[0055] As the material of the second carrier transport part 103, a metal oxide that is translucent to light in a specific wavelength region is applied. Examples of metal oxides include titanium dioxide (TiO2), tin dioxide (SnO2), zinc oxide (ZnO) or indium oxide (In2O3). The metal oxide may, for example, be added with an n-type dopant. For example, if the metal oxide is ZnO, the n-type dopant may be aluminum (Al) or boron (B). The thickness of the second electrode part 102 may, for example, be about 10 nm to 50 nm. For example, the second carrier transport part 103 may be formed on the second electrode part 102 by applying a raw material solution on the second electrode part 102 and hydrolyzing the raw material to generate a metal oxide, wherein the raw material solution is prepared by dissolving a raw material such as a metal chloride or a metal isopropoxide in a polar solution. Here, the metal chloride may, for example, include titanium chloride, tin chloride, zinc chloride or indium chloride. The metal isopropoxide includes, for example, titanium isopropoxide, tin isopropoxide, zinc isopropoxide, or indium isopropoxide.

[0056] <1-1-4. Photoelectric conversion unit 104>

[0057] The photoelectric conversion region 104 is located on the second carrier transporting region 103. The photoelectric conversion region 104 is located on the second element plane F2 side of the second carrier transporting region 103. In other words, the photoelectric conversion region 104 is located on the −Z direction side of the second carrier transporting region 103.

[0058] The photoelectric conversion unit 104 can absorb light that has passed through the substrate unit 101, the second electrode unit 102, and the second carrier transport unit 103. In the first embodiment, the photoelectric conversion unit 104 uses, for example, an intrinsic semiconductor (also referred to as an i-type semiconductor). The i-type semiconductor can use, for example, a semiconductor having a perovskite structure (also referred to as a perovskite semiconductor).

[0059] Perovskite semiconductors may include, for example, halide-based organic-inorganic perovskite semiconductors. Halide-based organic-inorganic perovskite semiconductors are semiconductors having a perovskite structure with a composition of ABX3. Here, A in the above-mentioned ABX3, for example, uses one or more ions of methylammonium (CH3NH3), formamidine (CH(NH2)2), cesium (Cs), rubidium (Rb) and potassium (K). In addition, B in the above-mentioned ABX3, for example, uses one or more ions of lead (Pb) and tin (Sn). In addition, X in the above-mentioned ABX3, for example, uses one or more ions of iodine (I), bromine (Br) and chlorine (Cl). Specifically, a semiconductor having a perovskite structure with a composition of ABX3 may be composed of organic perovskites such as CH3NH3PbI3 or (CH(NH2)2, Cs)Pb(I, Br)3. For example, after applying the first raw material solution on the second carrier transport portion 103, the applied first raw material solution is dried, so that an organic perovskite can be formed. Here, the organic perovskite may be a crystalline thin film. The first raw material solution may be generated, for example, by dissolving alkylamine halide and lead halide as raw materials in a solvent. The thickness of the photoelectric conversion unit 104 may be, for example, about 100 nm to 2000 nm. Hereinafter, the energy level of VBM in the photoelectric conversion unit 104 (VBM energy level) is referred to as the third energy level EL3.

[0060] <1-1-5. First Carrier Transporting Section 105 >

[0061] The first carrier transporting region 105 is located on the photoelectric conversion region 104. The first carrier transporting region 105 is located on the second element plane F2 side of the photoelectric conversion region 104. In other words, the first carrier transporting region 105 is located on the -Z direction side of the photoelectric conversion region 104.

[0062] In the first embodiment, the first carrier transporting section 105 may be, for example, a semiconductor having a p-type conductivity (also referred to as a p-type semiconductor). In this case, the first carrier transporting section 105 may function as, for example, a so-called electron blocking layer and a hole transport layer (HTL). The HTL may, for example, collect holes and output them.

[0063] As a material for the first carrier transporting section 105, for example, [2,2',7,7'-Tetrakis-(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene] (2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene: spiro-OMeTAD) as a soluble diamine derivative can be applied. For example, after applying the second raw material liquid on the perovskite semiconductor layer as the photoelectric conversion section 104, the applied second raw material liquid is dried to form the first carrier transporting section 105. The thickness of the carrier transporting layer can be, for example, about 50 nm to 200 nm.

[0064] As other materials for the first carrier transport portion 105, for example, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]: PTAA), poly(3-hexylthiophene-2,5-diyl) (Poly(3-hexylthiophene-2,5-diyl): P3HT) or poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS) can be used.

[0065] The first carrier transporting section 105 has: a surface (also referred to as a first surface) CF1 in contact with the photoelectric conversion section 104; and a surface (also referred to as a second surface) CF2 in contact with the first electrode section 106. Hereinafter, the energy level of the highest occupied molecular orbital (HOMO energy level) in the region Ab1 along the first surface CF1 (also referred to as a first interface region) in the first carrier transporting section 105 is referred to as a first energy level EL1. In addition, the energy level of the highest occupied molecular orbital (HOMO energy level) in the region Ab2 along the second surface CF2 (also referred to as a second interface region) in the first carrier transporting section 105 is referred to as a second energy level EL2.

[0066] Here, the first interface region Ab1 may be a region of the first carrier transport portion 105 where the first surface CF1 is formed along the first surface CF1. The first interface region Ab1 may have a prescribed thickness along the first direction from the first surface CF1 toward the second surface CF2, i.e., the -Z direction. The prescribed thickness may be determined, for example, based on the spatial resolution of a device for measuring the HOMO energy level. In addition, in the case where the device for measuring the HOMO energy level performs prescribed etching on the surface of a sample as a measurement object and measures the HOMO energy level in the depth direction of the sample as a measurement object, the prescribed thickness may be determined based on an etching rate error or a time resolution of the etching operation, etc. The prescribed thickness may be, for example, 5nm, 3nm, 1nm, 0.5nm, 0.3nm, or 0.1nm, etc.

[0067] The second interface region Ab2 may be a region in the first carrier transport portion 105 where the second surface CF2 is formed along the second surface CF2. The second interface region Ab2 may have a prescribed thickness along a second direction opposite to the first direction, i.e., the +Z direction. The prescribed thickness may be determined, for example, based on the spatial resolution of a device for measuring the HOMO energy level. In addition, in the case where the device for measuring the HOMO energy level performs prescribed etching on the surface of a sample as a measurement object and measures the HOMO energy level in the depth direction of the sample as a measurement object, the prescribed thickness may be determined based on an etching rate error or a time resolution of an etching operation, etc. The prescribed thickness may be, for example, 5 nm, 3 nm, 1 nm, 0.5 nm, 0.3 nm, or 0.1 nm, etc.

[0068] <1-1-6. First Electrode Section 106 >

[0069] The first electrode portion 106 is located on the first carrier transporting portion 105. The first electrode portion 106 is located on the second element plane F2 side of the first carrier transporting portion 105. In other words, the first electrode portion 106 is located on the −Z direction side of the first carrier transporting portion 105.

[0070] The first electrode portion 106 can collect carriers generated by photoelectric conversion according to the irradiation of light to the photoelectric conversion portion 104. Here, the material of the first electrode portion 106 is, for example, a metal with excellent conductivity such as gold (Au) or TCO. TCO includes, for example, ITO, FTO or ZnO. The first electrode portion 106 is, for example, a layered electrode (also referred to as a first electrode layer). The thickness of the first electrode portion 106 is, for example, about 10nm to 1000nm. The first electrode portion 106 can be formed on the first carrier transport portion 105 by a vacuum process such as sputtering. Here, for example, when TCO is applied to the material of the first electrode portion 106, the first electrode portion 106 is translucent to light in a specific wavelength region. At this time, for example, light irradiated to the second element surface F2 can pass through the first electrode portion 106 and reach the photoelectric conversion portion 104. As a result, for the solar cell element 10, not only the first element surface F1 but also two surfaces including the second element surface F2 can serve as light receiving surfaces. Hereinafter, the Fermi level in the first electrode portion 106 is referred to as a fourth energy level EL4.

[0071] The first electrode portion 106 and the second electrode portion 102 may be electrically connected to wirings 20 such as wires, for example. Specifically, for example, the first wiring 20a may be electrically connected to the first electrode portion 106, and the second wiring 20b may be connected to the second electrode portion 102. Each wiring 20 may be bonded to the first electrode portion 106 and the second electrode portion 102, for example, by soldering or the like. In the solar cell element 10, for example, the output obtained by photoelectric conversion can be extracted using the first wiring 20a and the second wiring 20b.

[0072] <1-2. Structure of energy band of first carrier transporting region 105 >

[0073] The first carrier transporting section 105 of the solar cell element 10 of the first embodiment may have, for example, Figure 2 The band structure is as shown in Figure 2 In the figure, the horizontal axis represents the position in the -Z direction, and the vertical axis represents the energy level. Figure 2 , from left to right, the energy level of the bandgap B103 in the second carrier transporting part 103, the energy level of the bandgap B104 in the photoelectric conversion part 104, the energy level of the bandgap B105 in the first carrier transporting part 105, and the Fermi level in the first electrode 106 are shown in the order of the description.

[0074] In the first carrier transport unit 105, the HOMO energy level in the first interface region Ab1 along the first surface CF1, i.e., the first energy level EL1, is different from the HOMO energy level in the second interface region Ab2 along the second surface CF2, i.e., the second energy level EL2. The first surface CF1 is the surface in contact with the photoelectric conversion unit 104, and the second surface CF2 is the surface in contact with the first electrode unit 106.

[0075] Here, it is assumed that the HOMO level in the first carrier transporting section 105 is substantially constant in the thickness direction. In this case, in order to increase the photoelectromotive force, assuming that the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not bonded, if the HOMO level of the material of the first carrier transporting section 105 is made close to the VBM level of the material of the photoelectric conversion section 104, the difference between the HOMO level of the material of the first carrier transporting section 105 and the Fermi level of the material of the first electrode section 106 will increase. As a result, in the state of the solar cell element 10, the energy barrier between the first carrier transporting section 105 and the first electrode section 106 will increase. In addition, in order to reduce the energy barrier between the first carrier transporting section 105 and the first electrode section 106 of the solar cell element 10, assuming that the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not bonded, if the HOMO energy level of the material of the first carrier transporting section 105 is brought close to the Fermi energy level in the first electrode section 106, the difference between the HOMO energy level of the material of the first carrier transporting section 105 and the Fermi energy level of the material of the second carrier transporting section 103 will be reduced. In other words, the difference between the Fermi energy level of the material of the first carrier transporting section 105 and the Fermi energy level of the material of the second carrier transporting section 103 will be reduced. As a result, the photoelectromotive force of the solar cell element 10 can be reduced.

[0076] In contrast, as described above, it is assumed that the first energy level EL1 is different from the second energy level EL2. In this case, for example, the second energy level EL2 can be changed without changing the first energy level EL1. In addition, for example, the first energy level EL1 can be changed without changing the second energy level EL2. In other words, for example, in a state where the second energy level EL2 is close to the Fermi level in the first electrode portion 106, that is, the fourth energy level EL4, the first energy level EL1 can be close to the VBM level of the photoelectric conversion portion 104, that is, the third energy level EL3. In addition, for example, in a state where the first energy level EL1 is close to the VBM level of the photoelectric conversion portion 104, that is, the third energy level EL3, the second energy level EL2 can be close to the Fermi level in the first electrode portion 106, that is, the fourth energy level EL4. Thus, the photoelectromotive force can be increased without increasing the energy barrier between the first carrier transport portion 105 and the first electrode portion 106. From another perspective, the energy barrier between the first carrier transport portion 105 and the first electrode portion 106 can be reduced without reducing the photoelectromotive force.

[0077] The HOMO level in the first carrier transport section 105 can be measured, for example, using ultraviolet photoelectron spectroscopy (UPS). When using UPS, the HOMO level can be estimated based on the position where the spectrum of the detected photoelectrons stands up. Thus, the HOMO level can be determined. The VBM level in the photoelectric conversion section 104 can also be measured, for example, using UPS in the same way as the HOMO level. In this case, the VBM level can be estimated based on the position where the spectrum of the detected photoelectrons stands up. Thus, the VBM level can be determined. The HOMO level and VBM level of each section can be measured, for example, by other measurement methods such as X-ray photoelectron spectroscopy (X-ray Photoelectron Spectroscopy: XPS). In addition, for example, by etching the surface of the sample using a gas cluster ion beam (GCIB) and measuring using UPS or XPS, the distribution of the HOMO level in the depth direction of the sample can be measured. In addition, the Fermi level in the first electrode section 106 can be measured, for example, using UPS. When UPS is used, the Fermi level can be estimated from the position where the detected photoelectron spectrum stands. Thus, the Fermi level can be determined. The Fermi level in the first electrode portion 106 can be measured by other measurement methods such as X-ray photoelectron spectroscopy (XPS).

[0078] In the present invention, two energy levels are different means that the absolute value of the difference between the two energy levels is greater than a specified value. On the other hand, the absolute value of the difference between the two energy levels can also be considered to be equal if it is less than a specified value. In addition, the absolute value of the difference between the two energy levels can also be considered to be approximately the same if it is less than a specified value. It can be said that the two energy levels are approximately the same and the two energy levels are substantially the same. The specified value can be determined, for example, based on the measurement error of a measuring device that measures the energy level, such as UPS or XPS. In this case, as a specified value, for example, 0.1eV (electron Volt) can be used. In other words, the two energy levels are approximately the same, for example, can be the same as the absolute value of the difference between the two energy levels being less than 0.1eV as a specified value.

[0079] In the first carrier transporting section 105, the HOMO energy level of the first carrier transporting section 105 can be changed by changing the concentration of the dopant. In other words, in the first carrier transporting section 105, the HOMO energy level of the first carrier transporting section 105 can be changed by changing the carrier density. From another point of view, the carrier density of the first carrier transporting section 105 can also be changed by changing the concentration of the dopant in the first carrier transporting section 105. The concentration of the dopant in the first carrier transporting section 105 can be changed, for example, in such a manner that the concentration of the dopant decreases from the first surface CF1 to the second surface CF2. More specifically, the concentration of the dopant in the first carrier transporting section 105 can be changed, for example, in such a manner that the concentration of the dopant decreases from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2. In other words, like Figure 1 In this way, when the solar cell element 10 is observed in an X-Z cross section, the concentration of the dopant in the first carrier transporting section 105 can be changed, for example, in such a way that the concentration of the dopant decreases along the -Z direction. The concentration of the dopant can be expressed, for example, by the number of atoms of the dopant per unit volume or the number of moles (mol) of the dopant per unit volume. The change in the concentration of the dopant in the first carrier transporting section 105 can be achieved, for example, by diffusing the dopant from the first surface CF1 to the second surface CF2 in the layer of the semiconductor material constituting the first carrier transporting section 105. The change in the concentration of the dopant in the first carrier transporting section 105 can be controlled, for example, by selecting the material of the dopant, or by the conditions under which the dopant is diffused in the layer of the semiconductor material when the first carrier transporting section 105 is formed. In other words, for example, the change in the concentration of the dopant in the first carrier transporting section 105 can be controlled by the conditions under which the first carrier transporting section 105 is formed.

[0080] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, the first energy level EL1 is smaller than the second energy level EL2. Generally, the third energy level EL3 of the photoelectric conversion section 104 is smaller than the fourth energy level EL4 of the first electrode section 106. Therefore, by making the first energy level EL1 of the first carrier transport section 105 smaller than the second energy level EL2, the difference between the first energy level EL1 and the third energy level EL3 can be reduced, and the difference between the second energy level EL2 and the fourth energy level EL4 can be reduced. In other words, by making the first energy level EL1 of the first carrier transport section 105 smaller than the second energy level EL2, the difference between the first energy level EL1 and the third energy level EL3 can be reduced while reducing the difference between the second energy level EL2 and the fourth energy level EL4. As a result, the photoelectromotive force in the solar cell element 10 can be increased, and the energy barrier between the first carrier transport section 105 and the first electrode section 106 can be reduced. From another perspective, the energy barrier between the first carrier transporting section 105 and the first electrode section 106 can be reduced, and the photovoltaic power in the solar cell element 10 can be increased. As a result, the power generation efficiency in the solar cell element 10 can be improved.

[0081] In the first carrier transporting section 105 of the solar cell element 10 of the first embodiment, for example, the HOMO energy level in the first carrier transporting section 105 may increase along the first direction from the first surface CF1 toward the second surface CF2. In other words, in the first carrier transporting section 105, for example, the HOMO energy level may increase along the first direction from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2. Here, the HOMO energy level of the first carrier transporting section 105 may increase continuously or discretely. For example, in the case where the distribution of the HOMO energy level of the first carrier transporting section 105 along the first direction is shown in a graph, the HOMO energy level in the first carrier transporting section 105 may increase monotonically along the first direction. In this case, the rate of change of the HOMO energy level in the first direction may be constant or non-constant. The rate of change of the HOMO energy level in the first direction may be a value obtained by dividing the amount of change of the HOMO energy level relative to the amount of change of the position in the first direction by the amount of change of the position in the first direction. In addition, for example, when the distribution of the HOMO energy level of the first carrier transporting portion 105 along the first direction is shown in a graph, the HOMO energy level in the first carrier transporting portion 105 may increase in a step-like manner along the first direction. If the HOMO energy level in the first carrier transporting portion 105 increases along the first direction, the shape of the graph representing the distribution of the HOMO energy level in the first direction of the first carrier transporting portion 105 will not be a shape that is concave in the direction where the energy level becomes higher on the way from the first surface CF1 to the second surface CF2. If there is a portion that is concave in the direction where the energy level becomes higher in the shape of the graph representing the distribution of the HOMO energy level in the first direction of the first carrier transporting portion 105, the movement of carriers is suppressed at the concave portion, and the power generation efficiency of the solar cell element 10 may be reduced. In contrast, the HOMO energy level in the first carrier transporting portion 105 increases along the first direction, so that holes as carriers are easy to move in the first carrier transporting portion 105. As a result, the decrease in the power generation efficiency in the solar cell element 10 can be reduced.

[0082] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, for example, the first energy level EL1 may be substantially the same as the third energy level EL3. That is, the absolute value of the difference between the first energy level EL1 and the third energy level EL3 may be less than a specified value. As described above, the specified value may be determined based on the measurement error of a measuring device such as UPS or XPS that measures the energy level. In this case, for example, 0.1 eV may be used as the specified value. If the first energy level EL1 is substantially the same as the third energy level EL3, the energy barrier between the first carrier transport section 105 and the photoelectric conversion section 104 can be reduced.

[0083] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, for example, the first energy level EL1 may be larger than the third energy level EL3 and may be substantially the same as the third energy level EL3. In this case, the first energy level EL1 is larger than the third energy level EL3. Therefore, holes, which are carriers, are easily moved from the photoelectric conversion section 104 to the first carrier transport section 105. This is because electrons with negative charges have the property of moving to the side with a smaller energy level, whereas holes with positive charges opposite to negative charges have the property of moving to the side with a larger energy level.

[0084] In the first carrier transport unit 105 of the solar cell element 10 of the first embodiment, for example, the second energy level EL2 may be substantially the same as the fourth energy level EL4. That is, the absolute value of the difference between the second energy level EL2 and the fourth energy level EL4 may be less than a specified value. As described above, the specified value may be determined based on the measurement error of a measuring device such as UPS or XPS that measures the energy level. In this case, for example, 0.1 eV may be used as the specified value. If the second energy level EL2 is substantially the same as the fourth energy level EL4, the energy barrier between the first carrier transport unit 105 and the first electrode unit 106 can be reduced.

[0085] In the first carrier transporting section 105 of the solar cell element 10 of the first embodiment, for example, the second energy level EL2 may be smaller than the fourth energy level EL4 and may be substantially the same as the fourth energy level EL4. In this case, the fourth energy level EL4 is larger than the second energy level EL2. Therefore, holes, which are carriers, are easily moved from the first carrier transporting section 105 to the first electrode section 106. This is because electrons with negative charges have the property of moving to the side with a smaller energy level, whereas holes with positive charges opposite to negative charges have the property of moving to the side with a larger energy level.

[0086] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, for example, Figure 3 As shown, the first carrier transporting portion 105 may include a first region 1051 arranged along the first surface CF1. The first region 1051 has a first predetermined thickness from the first surface CF1 along the -Z direction as the first direction. The first region 1051 is a region where the first surface CF1 is formed. The first region 1051 is in contact with the photoelectric conversion portion 104 on the first surface CF1. In this case, the first carrier transporting portion 105 of the solar cell element 10 of the first embodiment may have, for example, Figure 4 The band structure shown. Figure 4 The energy band diagram is Figure 2The energy band diagram is based on the energy band diagram of and the energy level of the band gap B1051 of the first region 1051, the energy level of the band gap B1053 of the third region 1053 described later, and the energy level of the band gap B1052 of the second region 1052 described later are shown from left to right in the order of the description to replace the energy level of the band gap B105 of the first carrier transporting part 105. Here, the HOMO energy level in the first region 1051 can be substantially the same as the third energy level EL3. In other words, it can be said that in the first carrier transporting part 105, corresponding to the first specified thickness along the first direction from the first surface CF1, the HOMO energy level is substantially the same as the third energy level EL3. In other words, it can also be said that the HOMO energy level in the first region 1051 is substantially the same as the third energy level EL3 along the -Z direction as the first direction. Here, for example, since the first carrier transporting portion 105 has the first region 1051 , even if the HOMO energy level in the first carrier transporting portion 105 increases along the −Z direction which is the first direction, the decrease in the photoelectromotive force of the solar cell element 10 can be reduced compared to the case where there is no first region 1051 .

[0087] As described above, the photoelectromotive force of the solar cell element 10 is determined in proportion to the difference between the Fermi level of the material of the first carrier transporting section 105 and the Fermi level of the material of the second carrier transporting section 103. Here, assuming that the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not in contact, the Fermi level of the material of the first carrier transporting section 105, which contributes to the determination of the photoelectromotive force, can be approximated to the average value of the Fermi level in the region of the first carrier transporting section 105 that contacts the photoelectric conversion section 104 (also referred to as the first contact region), for example. The thickness of the first contact region along the -Z direction as the first direction can be, for example, 1 nm or more and less than 100 nm. Therefore, for example, in the first contact region, when the HOMO level in the first carrier transporting section 105 increases along the -Z direction as the first direction, the Fermi level in the first carrier transporting section 105 can also increase along the -Z direction as the first direction, similarly to the HOMO level. Thus, the average value of the Fermi level in the region (first contact region) in the first carrier transporting section 105 that is in contact with the photoelectric conversion section 104 can be increased. As a result, assuming that the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not in contact, the difference between the Fermi level in the first carrier transporting section 105 and the Fermi level in the second carrier transporting section 103 that contributes to determining the photoelectromotive force becomes smaller. Therefore, the photoelectromotive force of the solar cell element 10 becomes smaller.

[0088] In contrast, for example, if the first carrier transporting section 105 has the first region 1051, the average value of the Fermi level in the region (first contact region) in the first carrier transporting section 105 that contacts the photoelectric conversion section 104 can be substantially the same as the third energy level EL3. Thus, even if the HOMO level in the first carrier transporting section 105 increases along the -Z direction, which is the first direction, if the first carrier transporting section 105 has the first region 1051, the difference between the Fermi level in the first carrier transporting section 105 and the Fermi level in the second carrier transporting section 103, which contributes to determining the photoelectromotive force, can be reduced, assuming that the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not bonded. Therefore, the decrease in the photoelectromotive force of the solar cell element 10 can be reduced.

[0089] The first prescribed thickness may be, for example, greater than 10 nm. Thus, if the first prescribed thickness is not too small, the average value of the Fermi level in the region (first contact region) in contact with the photoelectric conversion region 104 in the first carrier transporting portion 105 may be substantially the same as the third energy level EL3. In addition, the first prescribed thickness may be, for example, less than 100 nm. Thus, if the first prescribed thickness is not too large, in the case where the first carrier transporting portion 105 has the second region 1052 described later, the thickness of the second region 1052 will not be too small, and the increase in the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106 can be reduced.

[0090] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, for example, Figure 3 As shown, the first carrier transport portion 105 may include a second region 1052 arranged along the second surface CF2. The second region 1052 has a second predetermined thickness from the second surface CF2 along a second direction opposite to the first direction, that is, the +Z direction. The second region 1052 is a region where the second surface CF2 is formed. The second region 1052 is in contact with the first electrode portion 106 on the second surface CF2. In this case, for example, Figure 4As shown, the HOMO energy level in the second region 1052 can be substantially the same as the fourth energy level EL4. In other words, it can be said that in the first carrier transporting portion 105, corresponding to the second specified thickness along the second direction from the second surface CF2, the HOMO energy level is substantially the same as the fourth energy level EL4. In other words, it can also be said that the HOMO energy level in the second region 1052 is substantially the same as the fourth energy level EL4 along the +Z direction as the second direction. Here, for example, since the first carrier transporting portion 105 has the second region 1052, even if the HOMO energy level in the first carrier transporting portion 105 increases along the -Z direction as the first direction, the size of the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106 can be reduced compared to the case where there is no second region 1052.

[0091] As described above, the magnitude of the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106 is determined based on the difference between the HOMO energy level of the material of the first carrier transporting portion 105 and the Fermi energy level of the material of the first electrode portion 106, assuming that the second carrier transporting portion 103, the photoelectric conversion portion 104, the first carrier transporting portion 105, and the first electrode portion 106 are not bonded. Here, the HOMO energy level of the material of the first carrier transporting portion 105, which helps determine the magnitude of the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106, assuming that the second carrier transporting portion 103, the photoelectric conversion portion 104, the first carrier transporting portion 105, and the first electrode portion 106 are not bonded, can be approximated to, for example, the average value of the HOMO energy level in the region of the first carrier transporting portion 105 that contacts the first electrode portion 106 (also referred to as the second contact region). The thickness of the second contact region along the +Z direction, which is the second direction, can be, for example, greater than 1 nm and less than 100 nm. Therefore, for example, in the second contact region, when the HOMO level in the first carrier transporting portion 105 increases along the -Z direction as the first direction, the average value of the HOMO level of the first carrier transporting portion 105 decreases. As a result, the difference between the HOMO level in the region (second contact region) of the first carrier transporting portion 105 that contacts the first electrode portion 106 and the Fermi level in the first electrode portion 106, assuming that the second carrier transporting portion 103, the photoelectric conversion portion 104, the first carrier transporting portion 105, and the first electrode portion 106 are not bonded, increases. Therefore, in accordance with the increase in the difference between the HOMO level in the region (second contact region) of the first carrier transporting portion 105 that contacts the first electrode portion 106 and the Fermi level in the first electrode portion 106, the size of the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106 increases.

[0092] In contrast, for example, if the first carrier transporting section 105 has the above-mentioned second region 1052, the average value of the HOMO level in the region (second contact region) in the first carrier transporting section 105 that contacts the first electrode section 106 can be substantially the same as the fourth energy level EL4. Thus, even if the HOMO level in the first carrier transporting section 105 increases along the -Z direction, which is the first direction, if the first carrier transporting section 105 has the second region 1052, the difference between the HOMO level in the first carrier transporting section 105 and the Fermi level in the first electrode section 106, which contributes to determining the size of the energy barrier between the first carrier transporting section 105 and the first electrode section 106, can be reduced in the case where the second carrier transporting section 103, the photoelectric conversion section 104, the first carrier transporting section 105, and the first electrode section 106 are not bonded. Therefore, in the solar cell element 10 , the size of the energy barrier between the first carrier transporting portion 105 and the first electrode portion 106 can be reduced.

[0093] The second prescribed thickness may be, for example, greater than 10 nm. Thus, if the second prescribed thickness is not too small, the average value of the HOMO energy level in the region (second contact region) in contact with the first electrode portion 106 in the first carrier transport portion 105 may be substantially the same as the fourth energy level EL4. In addition, the second prescribed thickness may be, for example, less than 100 nm. Thus, if the second prescribed thickness is not too large, in the case where the first carrier transport portion 105 has the above-mentioned first region 1051, the thickness of the first region 1051 will not be too small, and the decrease in the photoelectromotive force of the solar cell element 10 can be reduced.

[0094] In the first carrier transport section 105 of the solar cell element 10 of the first embodiment, for example, Figure 3 As shown, the first carrier transport portion 105 may include a third region 1053 located between the first region 1051 and the second region 1052. In this case, for example, Figure 4As shown, the HOMO energy level in the third region 1053 may increase along the -Z direction as the first direction. The HOMO energy level in the first carrier transporting portion 105 may increase continuously or discretely. For example, in the case where the distribution of the HOMO energy level of the first carrier transporting portion 105 along the first direction is shown in a graph, the HOMO energy level in the first carrier transporting portion 105 may increase monotonically along the first direction. In addition, for example, in the case where the distribution of the HOMO energy level in the first direction of the first carrier transporting portion 105 is shown in a graph, the HOMO energy level in the first carrier transporting portion 105 may increase in a step-like manner along the first direction. If the HOMO energy level in the first carrier transporting portion 105 increases along the first direction, the shape of the graph representing the distribution of the HOMO energy level in the first direction of the first carrier transporting portion 105 will not be a shape that is concave in the direction where the energy level becomes higher on the way from the first region 1051 side to the second region 1052 side. If there is a portion that is concave in the direction where the energy level becomes higher in the shape of the graph representing the distribution of the HOMO energy level of the first carrier transporting section 105 in the first direction, the movement of carriers is suppressed at the concave portion, and the conversion efficiency of the solar cell element 10 may be reduced. In contrast, the HOMO energy level in the third region 1053 of the first carrier transporting section 105 increases in the first direction, so that holes, which are carriers, are easy to move in the first carrier transporting section 105. As a result, the decrease in the conversion efficiency of the solar cell element 10 can be reduced.

[0095] Furthermore, in the first carrier transporting section 105 of the solar cell element 10 of the first embodiment, for example, Figure 5 As shown in FIG. 1 , the first carrier transporting portion 105 may not include the second region 1052 located between the third region 1053 and the first electrode portion 106. In other words, for example, the first carrier transporting portion 105 may include the third region 1053 located between the first region 1051 and the first electrode portion 106. In this case, the first carrier transporting portion 105 of the solar cell element 10 of the first embodiment may have, for example, Figure 6 The band structure shown. Figure 6 The energy band diagram is Figure 4 The energy band diagram is based on the energy band diagram and the energy band diagram of the energy level of the band gap B1052 of the second region 1052 is deleted.

[0096] In addition, in the first carrier transporting section 105 of the solar cell element 10 of the first embodiment, for example, Figure 7As shown in FIG. 1 , the first carrier transporting portion 105 may not include the first region 1051 located between the photoelectric conversion portion 104 and the third region 1053. In other words, for example, the first carrier transporting portion 105 may include the third region 1053 located between the second region 1052 and the photoelectric conversion portion 104. In this case, the first carrier transporting portion 105 of the solar cell element 10 of the first embodiment may have, for example, Figure 8 The band structure shown. Figure 8 The energy band diagram is Figure 4 The energy band diagram is based on the energy band diagram and the energy band diagram of the energy level of the band gap B1051 of the first region 1051 is deleted.

[0097] In the description so far, the HOMO energy level in the first carrier transporting portion 105 is used for description, but the invention is not limited thereto. For example, the HOMO energy level in the first carrier transporting portion 105 is relatively small, or in other words, the carrier density in the first carrier transporting portion 105 is relatively large. In addition, the HOMO energy level in the first carrier transporting portion 105 is relatively large, or in other words, the carrier density in the first carrier transporting portion 105 is relatively small.

[0098] For example, the first energy level EL1 in the first carrier transporting portion 105 is different from the second energy level EL2, or in other words, the carrier density in the first interface region Ab1 along the first surface CF1 in the first carrier transporting portion 105 is different from the carrier density in the second interface region Ab2 along the second surface CF2. In addition, for example, the first energy level EL1 in the first carrier transporting portion 105 is smaller than the second energy level EL2, or in other words, the carrier density in the first interface region Ab1 along the first surface CF1 in the first carrier transporting portion 105 is greater than the carrier density in the second interface region Ab2 along the second surface CF2. In addition, the HOMO energy level of the first carrier transporting portion 105 increases along the first direction, or in other words, the carrier density of the first carrier transporting portion 105 decreases along the first direction. In addition, the HOMO energy level of the first carrier transporting portion 105 increases along the first direction from the first interface region Ab1 to the second interface region Ab2. In other words, the carrier density of the first carrier transporting portion 105 decreases along the first direction from the first interface region Ab1 to the second interface region Ab2.

[0099] <1-3. Method for manufacturing solar cell element 10>

[0100] For example, Fig. 9 As shown, by performing the processing from step S1 to step S5 in the order described, it is possible to manufacture Figure 1The solar cell element 10 of the first embodiment exemplified in, etc. Here, for example, step S3 corresponds to the first step of the present invention, step S4 corresponds to the second step of the present invention, and step S5 corresponds to the third step of the present invention.

[0101] In step S1, the second electrode portion 102 is formed on the substrate portion 101. Here, for example, the material of the second electrode portion 102 is deposited on the substrate portion 101 by a vacuum process such as sputtering, so that the second electrode portion 102 can be formed on the substrate portion 101. The material of the second electrode portion 102 is, for example, TCO such as ITO, FTO or ZnO. In the case where the first electrode portion 106 is translucent to light in a specific wavelength range, the material of the second electrode portion 102 can be, for example, a metal with excellent conductivity such as Au.

[0102] In step S2, a second carrier transport portion 103 is formed on the second electrode portion 102. The material of the second carrier transport portion 103 is, for example, a metal oxide such as TiO2, SnO2, ZnO or In2O3. Here, for example, a raw material solution can be applied to the second electrode portion 102 to hydrolyze the raw material and generate a metal oxide, thereby forming the second carrier transport portion 103 on the second electrode portion 102, wherein the raw material solution is prepared by dissolving a raw material such as a metal chloride or a metal isopropoxide in a polar solution. Metal chlorides include, for example, titanium chloride, tin chloride, zinc chloride or indium chloride. Metal isopropoxides include, for example, titanium isopropoxide, tin isopropoxide, zinc isopropoxide or indium isopropoxide. Specifically, for example, a titanium tetrachloride aqueous solution is applied to the second electrode portion 102 by spin coating and dried. Then, for example, titanium tetrachloride is hydrolyzed by heating at about 150° C. on a hot plate, so that the second carrier transport portion 103 of TiO2 can be formed on the second electrode portion 102. Here, for example, an n-type dopant can also be added to the metal oxide. For example, if the metal oxide is ZnO, an element such as Al or B can be used as the n-type dopant. In this case, an n-type dopant can also be added to the raw material solution.

[0103] In addition, here, for example, the material of the second carrier transporting portion 103 may be an organic material. The organic material may be, for example, PCBM ([6,6]-Phenyl-C 61-Butyric Acid Methyl Ester, [6,6]-phenyl-C71-butyric acid isomethyl ester) and other fullerene derivatives. In this case, for example, a raw material solution prepared by dissolving the fullerene derivative in a chlorobenzene solvent can be used. Here, 1 milliliter (1mL) of the raw material solution can contain, for example, 5 milligrams (mg) to 20 mg of fullerene derivatives. In other words, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of the fullerene derivative is about 5 milligrams (mg / mL) to 20 mg / mL can be used. In addition, the second carrier transport portion 103 of PCBM can be formed on the second electrode portion 102 by drying and annealing the raw material solution applied on the second electrode portion 102. In addition, for the organic material used in the material of the second carrier transport portion 103, for example, the functional group can be changed to change the solubility and physical properties in the organic solvent. In this case, a dopant such as an n-type can also be added to the organic material.

[0104] In step S3, the photoelectric conversion unit 104 is formed on the second carrier transport unit 103. In other words, in step S3, the photoelectric conversion unit 104 is formed. Here, for example, a raw material solution is applied on the second carrier transport unit 103, and the applied raw material solution is annealed to form the photoelectric conversion unit 104. For example, the raw material solution can be generated by dissolving alkylamine halide and lead halide, which are raw materials of the photoelectric conversion unit 104, in a solvent, or dissolving alkylamine halide and tin halide, which are raw materials of the photoelectric conversion unit 104, in a solvent. In this case, the photoelectric conversion unit 104 can be composed of a thin film of a halide perovskite semiconductor having crystallinity.

[0105] In step S4, the first carrier transporting portion 105 is formed on the photoelectric conversion portion 104. Here, for example, by performing the processes of step S4a, step S4b, and step S4c in the order described, the first carrier transporting portion 105 can be formed on the photoelectric conversion portion 104. Here, for example, step S4a corresponds to the second A step of the present invention, step S4b corresponds to the second B step of the present invention, and step S4c corresponds to the second C step of the present invention.

[0106] In step S4a, a first layer is formed on the photoelectric conversion part 104. In step S4b, a second layer is formed on the first layer. In step S4c, the first layer and the second layer are heated to diffuse the dopant contained in the first layer into the second layer, thereby generating the first carrier transport part 105 from the first layer and the second layer. Here, the first layer has a higher concentration of dopant than the second layer. The second layer has a lower concentration of dopant than the first layer, or may not contain dopant. The second layer contains a material of a semiconductor constituting the first carrier transport part 105. Here, the dopant may be a p-type dopant for making the semiconductor a p-type semiconductor. The first layer may be a layer of a material or element contained as a dopant in the first carrier transport part 105. The first layer may contain a semiconductor material for a semiconductor constituting the first carrier transport part 105, or may not contain a semiconductor material for a semiconductor constituting the first carrier transport part 105. The second layer is a layer containing a semiconductor material of a semiconductor used to constitute the first carrier transporting portion 105 , and may or may not contain a material or element that serves as a dopant in the first carrier transporting portion 105 .

[0107] For example, in the case where the first layer does not include a semiconductor material for forming the semiconductor of the first carrier transporting section 105, in step S4a, a dopant layer is formed as the first layer on the photoelectric conversion section 104. The dopant layer may be a layer of a material or element that does not include a semiconductor material for forming the semiconductor of the first carrier transporting section 105 but is included in the first carrier transporting section 105 as a dopant. Here, for example, a raw material solution is applied to the photoelectric conversion section 104, and the raw material solution is dried or annealed, etc., so that the dopant layer can be formed on the photoelectric conversion section 104. For example, a raw material solution generated by dissolving lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or 4-tert-Butylpyridine (TBP) in a chlorobenzene solution can be used. Here, LiTFSI and TBP are materials that serve as dopants in the first carrier transporting section 105.

[0108] For example, in the case where the first layer includes a semiconductor material for forming a semiconductor of the first carrier transporting section 105, in step S4a, a highly doped layer is formed as the first layer on the photoelectric conversion section 104. The highly doped layer may be a layer including a semiconductor material for forming a semiconductor of the first carrier transporting section 105 and a material or element that serves as a dopant in the first carrier transporting section 105. Here, for example, a raw material solution is applied to the photoelectric conversion section 104, and the raw material solution is dried and annealed, so that a highly doped layer can be formed on the photoelectric conversion section 104. The semiconductor material for forming the semiconductor of the first carrier transporting section 105 may be, for example, an organic semiconductor material such as spiro-OMeTAD, P3HT, PTAA, or poly-TPD (4-butyl-N,N-diphenylamine homopolymer). Here, for example, the raw material solution can be prepared by dissolving spiro-OMeTAD and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in chlorobenzene, or dissolving spiro-OMeTAD and the material used as a dopant in the first carrier transporting section 105, namely TBP, in chlorobenzene. Here, for example, 1 mL of the raw material solution can contain about 10 mg to 85 mg of spiro-OMeTAD. In other words, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of spiro-OMeTAD is about 10 mg / mL to 85 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving P3HT and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in dichlorobenzene, or dissolving P3HT and the material used as a dopant in the first carrier transporting section 105, namely TBP, in dichlorobenzene. Here, for example, 1 mL of the raw material solution can also contain about 5 mg to 20 mg of P3HT. In other words, for example, a raw material solution in which the solvent is dichlorobenzene and the concentration of P3HT is about 5 mg / mL to 20 mg / mL can be used. In addition, for example, PTAA and the material used as a dopant in the first carrier transport section 105, i.e., LiTFSI, can be dissolved in toluene, or PTAA and the material used as a dopant in the first carrier transport section 105, i.e., TBP, can be dissolved in toluene to prepare the raw material solution. Here, for example, 1 mL of the raw material solution can contain about 5 mg to 20 mg of PTAA. In other words, for example, a raw material solution in which the solvent is toluene and the concentration of PTAA is 5 mg / mL to 20 mg / mL can be used. In addition, for example, poly-TPD and the material used as a dopant in the first carrier transport section 105, i.e., LiTFSI, can be dissolved in chlorobenzene, or poly-TPD and the material used as a dopant in the first carrier transport section 105, i.e., TBP, can be dissolved in chlorobenzene to prepare the raw material solution. Here, for example, 1 mL of the raw material solution can contain about 5 mg to 20 mg of poly-TPD.In other words, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of poly-TPD is 5 mg / mL to 20 mg / mL can be used.

[0109] For example, in the case where the second layer includes a material or element that serves as a dopant in the first carrier transporting section 105, in step S4b, a low-doped layer is formed as the second layer on the first layer. The low-doped layer may be a layer including a semiconductor material for a semiconductor constituting the first carrier transporting section 105 and a material or element that serves as a dopant in the first carrier transporting section 105. For example, if the first layer is a highly doped layer, the low-doped layer as the second layer may be a layer in which the concentration of the material or element that serves as a dopant in the first carrier transporting section 105 is reduced based on the highly doped layer. Here, for example, a raw material solution is applied to the first layer, and the raw material solution is dried, so that a low-doped layer can be formed on the first layer. The semiconductor material for the semiconductor constituting the first carrier transporting section 105 may be, for example, an organic semiconductor material such as spiro-OMeTAD, P3HT, PTAA or poly-TPD. Here, for example, the raw material solution can be prepared by dissolving spiro-OMeTAD and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in chlorobenzene, or dissolving spiro-OMeTAD and the material used as a dopant in the first carrier transporting section 105, namely TBP, in chlorobenzene. Here, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of spiro-OMeTAD is about 10 mg / mL to 85 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving P3HT and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in dichlorobenzene, or dissolving P3HT and the material used as a dopant in the first carrier transporting section 105, namely TBP, in dichlorobenzene. Here, for example, a raw material solution in which the solvent is dichlorobenzene and the concentration of P3HT is about 5 mg / mL to 20 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving PTAA and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in toluene, or dissolving PTAA and the material used as a dopant in the first carrier transporting section 105, namely TBP, in toluene. Here, for example, a raw material solution in which the solvent is toluene and the concentration of PTAA is 5 mg / mL to 20 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving poly-TPD and the material used as a dopant in the first carrier transporting section 105, namely LiTFSI, in chlorobenzene, or dissolving poly-TPD and the material used as a dopant in the first carrier transporting section 105, namely TBP, in chlorobenzene. Here, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of poly-TPD is 5 mg / mL to 20 mg / mL can be used.

[0110] For example, in the case where the second layer does not contain a material or element that is a dopant in the first carrier transporting section 105, in step S4b, an undoped layer is formed as the second layer on the first layer. The undoped layer may be a layer that contains a semiconductor material for forming the semiconductor of the first carrier transporting section 105 and does not contain a material or element that is a dopant in the first carrier transporting section 105. For example, if the first layer is a highly doped layer, the undoped layer as the second layer may be a layer that is based on the highly doped layer and from which a material or element that is a dopant in the first carrier transporting section 105 is removed. Here, for example, a raw material solution is applied to the first layer and dried, so that an undoped layer can be formed on the first layer. The semiconductor material for forming the semiconductor of the first carrier transporting section 105 can be, for example, an organic semiconductor material such as spiro-OMeTAD, P3HT, PTAA or poly-TPD. Here, for example, the raw material solution can be prepared by dissolving spiro-OMeTAD in chlorobenzene. Here, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of spiro-OMeTAD is about 10 mg / mL to 85 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving P3HT in dichlorobenzene. Here, for example, a raw material solution in which the solvent is dichlorobenzene and the concentration of P3HT is about 5 mg / mL to 20 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving PTAA in toluene. Here, for example, a raw material solution in which the solvent is toluene and the concentration of PTAA is 5 mg / mL to 20 mg / mL can be used. In addition, for example, the raw material solution can also be prepared by dissolving poly-TPD in chlorobenzene. Here, for example, a raw material solution in which the solvent is chlorobenzene and the concentration of poly-TPD is 5 mg / mL to 20 mg / mL can be used.

[0111] In step S4c, the first layer and the second layer are heated so that the dopant contained in the first layer diffuses into the second layer. Thus, the first carrier transport portion 105 is generated by the first layer and the second layer. Here, the heating of the first layer and the second layer may be annealing of the first layer and the second layer. The temperature and time of heating the first layer and the second layer may be appropriately set, for example, according to the material of the semiconductor in the first layer and the second layer and the material of the dopant. Here, for example, if the first layer is a dopant layer that does not contain a semiconductor material of a semiconductor used to constitute the first carrier transport portion 105, the semiconductor material of the semiconductor used to constitute the first carrier transport portion 105 can also diffuse from the second layer to the first layer.

[0112] In step S5, the first electrode portion 106 is formed on the first carrier transport portion 105. Here, for example, the material of the first electrode portion 106 is deposited on the first carrier transport portion 105 by a vacuum process such as sputtering, so that the first electrode portion 106 can be formed. The material of the first electrode portion 106 is, for example, a metal with excellent conductivity such as Au or a TCO such as ITO, FTO or ZnO. In addition, for example, after applying a metal paste as a coating liquid by screen printing, the applied metal paste is dried and the metal paste is solidified, thereby forming the first electrode portion 106.

[0113] Here, for step S4, for example, a dopant layer or a highly doped layer is used as the first layer, and a low doped layer or an undoped layer is used as the second layer, and the thicknesses of the first layer and the second layer, as well as the temperature and time conditions for heating the first layer and the second layer can be appropriately set. Thus, for example, a first carrier transporting portion 105 can be formed in which the concentration of the dopant decreases from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2 along the -Z direction as the first direction. In other words, for example, a first carrier transporting portion 105 can be formed in which the HOMO energy level increases from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2 along the -Z direction as the first direction. In this case, for example, the first carrier transporting portion 105 can have the following characteristics: Figure 2 The energy band structure as shown. In other words, in the first carrier transporting section 105, for example, the HOMO energy level in the first interface region Ab1, i.e., the first energy level EL1, can be smaller than the HOMO energy level in the second interface region Ab2, i.e., the second energy level EL2. Further, in the first carrier transporting section 105, for example, the HOMO energy level can increase from the first interface region Ab1 to the second interface region Ab2 along the -Z direction as the first direction. Here, for example, by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the dopant layer as the first layer, or appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the highly doped layer as the first layer, the HOMO energy level in the first interface region Ab1, i.e., the first energy level EL1, can be made substantially the same as the VBM energy level of the photoelectric conversion section 104, i.e., the third energy level EL3. In addition, for example, by appropriately setting the material of the semiconductor in the first carrier transport section 105 and the concentration of the dopant in the low-doped layer serving as the second layer, or by appropriately setting the material of the semiconductor in the first carrier transport section 105 and the concentration of the dopant in the undoped layer serving as the second layer, the HOMO energy level in the second interface region Ab2, i.e., the second energy level EL2, can be made substantially the same as the Fermi level in the first electrode section 106, i.e., the fourth energy level EL4.

[0114] Here, for step S4, for example, a highly doped layer is used as the first layer, and a low doped layer or an undoped layer is used as the second layer, and the thickness of each of the first layer and the second layer and the temperature and time conditions for heating the first layer and the second layer can be appropriately set. Figure 3 and Figure 5 As shown, the first carrier transporting section 105 including the first region 1051 can be formed. Here, for example, by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the highly doped layer as the first layer, the HOMO level in the first region 1051 can be made substantially the same as the VBM level in the photoelectric conversion section 104, that is, the third energy level EL3. Furthermore, for example, by appropriately setting the temperature and time conditions for heating the first layer and the second layer, Figure 3 The first carrier transport portion 105 including the first region 1051, the second region 1052 and the third region 1053 is formed as shown in FIG. Figure 5 As shown in FIG. 1 , a first carrier transporting portion 105 including a first region 1051 and a third region 1053 is formed. Figure 3 As shown in FIG. 1 , in the case of forming the first carrier transporting portion 105 including the first region 1051, the second region 1052, and the third region 1053, for example, the first carrier transporting portion 105 may have a Figure 4 In this case, for example, by appropriately setting the material of the semiconductor in the first carrier transporting portion 105 and the concentration of the dopant in the low-doped layer as the second layer, or appropriately setting the material of the semiconductor in the first carrier transporting portion 105 and the concentration of the dopant in the undoped layer as the second layer, the HOMO energy level in the second region 1052 can be made substantially the same as the Fermi level in the first electrode portion 106, that is, the fourth energy level EL4. Figure 5 As shown in FIG. 1 , in the case of forming the first carrier transporting portion 105 including the first region 1051 and the third region 1053, for example, the first carrier transporting portion 105 may have the following Figure 6 In this case, for example, by appropriately setting the material of the semiconductor in the first carrier transporting portion 105 and the concentration of the dopant in the low-doped layer as the second layer, or appropriately setting the material of the semiconductor in the first carrier transporting portion 105 and the concentration of the dopant in the undoped layer as the second layer, the HOMO level in the second interface region Ab2, i.e., the second energy level EL2, and the Fermi level in the first electrode portion 106, i.e., the fourth energy level EL4, can be made substantially the same.

[0115] Here, for step S4, for example, a dopant layer or a highly doped layer is used as the first layer, and a low-doped layer or an undoped layer is used as the second layer, and the thickness of each of the first layer and the second layer and the temperature and time conditions for heating the first layer and the second layer can be appropriately set. Figure 7 As shown, the first carrier transporting section 105 including the second region 1052 can be formed. Here, for example, by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the low-doped layer as the second layer, or by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the undoped layer as the second layer, the HOMO level in the second region 1052 can be made substantially the same as the Fermi level in the first electrode section 106, that is, the fourth energy level EL4. In addition, for example, by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the dopant layer as the first layer, or by appropriately setting the material of the semiconductor in the first carrier transporting section 105 and the concentration of the dopant in the high-doped layer as the first layer, the HOMO level in the first interface region Ab1, that is, the first energy level EL1, can be made substantially the same as the VBM level of the photoelectric conversion section 104, that is, the third energy level EL3.

[0116] <1-4. Solar cell module 1>

[0117] like Fig.10 As shown, for example, the solar cell module 1 includes: a plurality of solar cell elements 10; and a collector 30. In the solar cell module 1 of the first embodiment, the plurality of solar cell elements 10 share one substrate 101. In other words, in the solar cell module 1 of the first embodiment, a plurality of second electrode portions 102 are formed on one substrate 101.

[0118] The power collecting section 30 functions as an extraction electrode. The power collecting section 30 may be, for example, aluminum or copper wiring. The power collecting section 30 is connected to, for example, a terminal for extracting electricity generated by the solar cell element 10 .

[0119] <2. Other embodiments>

[0120] The present invention is not limited to the above-described first embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

[0121] <2-1. Second embodiment>

[0122] The second embodiment will be described below. The differences from the first embodiment will be mainly described below.

[0123] Fig.11It is a diagram schematically showing a first example of the cross-sectional structure of the solar cell element 40 according to the second embodiment. Fig.12 1 is an energy band diagram showing a first example of the energy level relationship among the first electrode portion 106 , the first carrier transport portion 105 , the photoelectric conversion portion 104 , and the second carrier transport portion 103 of the solar cell element 40 according to the second embodiment.

[0124] like Fig.11 As shown, the solar cell element 40 of the second embodiment is Figure 3 Based on an example of the solar cell element 10 of the first embodiment shown above, the first carrier transporting section 105 includes a fourth region 1054 instead of the third region 1053. The fourth region 1054 is located between the first region 1051 and the second region 1052. In this case, the first carrier transporting section 105 of the solar cell element 40 of the second embodiment may have, for example, Fig.12 The band structure shown. Fig.12 The energy band diagram is Figure 4 The energy band diagram is based on the energy band diagram of and shows the energy level of the forbidden band B1054 of the fourth region 1054 instead of the energy level of the forbidden band B1053 of the third region 1053. The HOMO energy level in the fourth region 1054 is substantially the same as the fifth energy level EL5, which is an energy level between the first energy level EL1 and the second energy level EL2. In other words, it can be said that for the fourth region 1054 of the first carrier transporting section 105, the HOMO energy level is substantially the same as the fifth energy level EL5 corresponding to the fourth prescribed thickness from the first region 1051 to the second region 1052. In other words, it can also be said that the HOMO energy level in the fourth region 1054 is substantially the same as the fifth energy level EL5 along the -Z direction which is the first direction. In this case, the HOMO energy level in the first carrier transporting section 105 increases discretely from the first surface CF1 to the second surface CF2. In other words, the HOMO energy level in the first carrier transporting portion 105 increases discretely from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2. More specifically, the HOMO energy level in the first carrier transporting portion 105 increases in a step-like manner from the first surface CF1 to the second surface CF2. In other words, the HOMO energy level in the first carrier transporting portion 105 increases in a step-like manner from the first interface region Ab1 along the first surface CF1 to the second interface region Ab2 along the second surface CF2. It should be noted that the difference between the first energy level EL1 and the fifth energy level EL5 and the difference between the second energy level EL2 and the fifth energy level EL5 may be the same or different.

[0125] For example, Fig.13As shown, similarly to the first embodiment, the processing of the above steps S1 to S3 is performed in the order of the description, and then the processing of step S4A is performed. Further, the processing of the above step S5 is performed similarly to the first embodiment, so that the manufacturing Fig.11 The solar cell element 40 of the second embodiment is exemplified in FIG. In step S4A, the processes of step S41, step S42, and step S43 are performed in the order described.

[0126] In step S41, a first region 1051 of a first carrier transporting portion 105 is formed on the photoelectric conversion portion 104. Here, for example, a second A raw material solution is applied on the photoelectric conversion portion 104, and the applied second A raw material solution is dried and annealed, so that the first region 1051 can be formed on the photoelectric conversion portion 104. The material of the second A raw material solution can be, for example, a material in which a dopant is added to a material of an organic semiconductor such as spiro-OMeTAD, P3HT, PTAA or poly-TPD. Here, the concentration of the dopant in the second A raw material solution is greater than the concentration of the dopant in each of the second B raw material solution and the second C raw material solution described later. As a dopant, for example, LiTFSI or TBP can be used.

[0127] In step S42, the fourth region 1054 of the first carrier transporting portion 105 is formed on the first region 1051 of the first carrier transporting portion 105. Here, for example, the second B raw material liquid is applied to the first region 1051, and the applied second B raw material liquid is dried and annealed, so that the fourth region 1054 can be formed on the first region 1051. The material of the second B raw material liquid can be, for example, a material in which a dopant is added to a material of an organic semiconductor such as spiro-OMeTAD, P3HT, PTAA or poly-TPD. Here, the concentration of the dopant in the second B raw material liquid is greater than the concentration of the dopant in the second C raw material liquid described later. As the dopant, for example, LiTFSI or TBP can be used.

[0128] In step S43, the second region 1052 of the first carrier transporting portion 105 is formed on the fourth region 1054 of the first carrier transporting portion 105. Here, for example, the second C raw material liquid is applied to the fourth region 1054, and the applied second C raw material liquid is dried and annealed, so that the second region 1052 can be formed on the fourth region 1054. The material of the second C raw material liquid can be, for example, a material in which a dopant is added to an organic semiconductor material such as spiro-OMeTAD, P3HT, PTAA or poly-TPD. As the dopant, LiTFSI or TBP can be used.

[0129] By adopting the first carrier transporting portion 105 having such a structure, the thickness of the first region 1051 and the second region 1052 can be controlled without controlling the conditions for diffusing the dopant. Thus, even when the thickness of the first carrier transporting portion 105 is large, the thickness of the first region 1051 and the second region 1052 can be easily controlled.

[0130] It should be noted that, in the above description of the second embodiment, the first carrier transporting portion 105 is composed of three regions, namely the first region 1051, the fourth region 1054, and the second region 1052, but the first carrier transporting portion 105 is not limited to this structure. For example, the first carrier transporting portion 105 may have a plurality of regions between the first region 1051 and the second region 1052, and the plurality of regions have different HOMO energy levels between the first energy level EL1 and the second energy level EL2.

[0131] In addition, for example, Fig.14 As shown, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may include a first interface layer 1055 located between the first region 1051 and the fourth region 1054. In this case, for example, even if the material of the first region 1051 is different from the material of the fourth region 1054, the presence of the first interface layer 1055 can reduce the degradation of one or more of the materials of the first region 1051 and the fourth region 1054 due to the contact between the materials of the first region 1051 and the fourth region 1054. In this case, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may have, for example, Fig.15 The band structure shown. Fig.15 The energy band diagram is Fig.12 The energy band diagram is based on the energy band diagram of the first region 1051 and the energy level of the band gap B1051 of the fourth region 1054 is added with the energy level of the band gap B1055 of the first interface layer 1055 between the energy level of the band gap B1051 of the first region 1051 and the energy level of the band gap B1054 of the fourth region 1054. Fig.15As shown, the HOMO energy level in the first interface layer 1055 can be above the HOMO energy level in the first region 1051 and below the HOMO energy level in the fourth region 1054. In other words, the HOMO energy level in the first interface layer 1055 can be above the first energy level EL1 which is substantially the same as the HOMO energy level in the first region 1051 and below the fifth energy level EL5 which is substantially the same as the HOMO energy level in the fourth region 1054. The material of the first interface layer 1055 can be, for example, a material which is translucent to light in a specific wavelength region. The material of the first interface layer 1055 can be, for example, a transparent conductive oxide (TCO) or a material used in a buffer layer of a tandem solar cell. For example, a raw material solution containing the material of the first interface layer 1055 is applied to the first region 1051, and the applied raw material solution is dried and annealed, thereby forming the first interface layer 1055. In addition, the first interface layer 1055 can be formed, for example, by a vacuum process such as sputtering.

[0132] In addition, for example, Fig.16 As shown, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may include a second interface layer 1056 located between the second region 1052 and the fourth region 1054. In this case, for example, even if the material of the second region 1052 is different from the material of the fourth region 1054, the presence of the second interface layer 1056 can reduce the degradation of one or more of the materials of the second region 1052 and the fourth region 1054 caused by the contact between the materials of the second region 1052 and the materials of the fourth region 1054. In this case, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may have, for example, Fig.17 The band structure shown. Fig.17 The energy band diagram is Fig.12 The energy band diagram is based on the energy band diagram of the second region 1052 and the energy level of the band gap B1052 of the fourth region 1054 is added with the energy level of the band gap B1056 of the second interface layer 1056 between the energy level of the band gap B1052 of the second region 1052 and the energy level of the band gap B1054 of the fourth region 1054. Fig.17As shown, the HOMO energy level in the second interface layer 1056 can be above the HOMO energy level in the fourth region 1054 and below the HOMO energy level in the second region 1052. In other words, the HOMO energy level in the second interface layer 1056 can be above the fifth energy level EL5 which is substantially the same as the HOMO energy level in the fourth region 1054 and below the second energy level EL2 which is substantially the same as the HOMO energy level in the second region 1052. The material of the second interface layer 1056 can use, for example, a material which is translucent to light in a specific wavelength region. The material of the second interface layer 1056 can, for example, be a transparent conductive oxide (TCO) or a material used in a buffer layer of a tandem solar cell. For example, a raw material solution containing the material of the second interface layer 1056 is applied to the fourth region 1054, and the applied raw material solution is dried and annealed, thereby forming the second interface layer 1056. In addition, the second interface layer 1056 can be formed, for example, by a vacuum process such as sputtering.

[0133] In addition, for example, Fig.18 As shown, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may include the first interface layer 1055 and the second interface layer 1056. The first interface layer 1055 is located between the first region 1051 and the fourth region 1054. The second interface layer 1056 is located between the second region 1052 and the fourth region 1054. In this case, the first carrier transporting portion 105 of the solar cell element 40 in the second embodiment may have, for example, Fig.19 The band structure shown. Fig.19 The energy band diagram is Fig.12 The energy band diagram is based on the energy band diagram of and the energy level of the band gap B1055 of the first interface layer 1055 is added between the energy level of the band gap B1051 of the first region 1051 and the energy level of the band gap B1054 of the fourth region 1054, and the energy level of the band gap B1056 of the second interface layer 1056 is added between the energy level of the band gap B1052 of the second region 1052 and the energy level of the band gap B1054 of the fourth region 1054. For example, Fig.19 As shown, the HOMO energy level in the first interface layer 1055 may be higher than the HOMO energy level in the first region 1051 and lower than the HOMO energy level in the fourth region 1054. In other words, the HOMO energy level in the first interface layer 1055 may be higher than the first energy level EL1 which is substantially the same as the HOMO energy level in the first region 1051 and lower than the fifth energy level EL5 which is substantially the same as the HOMO energy level in the fourth region 1054. In addition, for example, Fig.19As shown, the HOMO energy level in the second interface layer 1056 may be above the HOMO energy level in the fourth region 1054 and below the HOMO energy level in the second region 1052. In other words, the HOMO energy level in the second interface layer 1056 may be above the fifth energy level EL5 which is substantially the same as the HOMO energy level in the fourth region 1054 and below the second energy level EL2 which is substantially the same as the HOMO energy level in the second region 1052.

[0134] <2-2. Other embodiments>

[0135] In the first embodiment and the second embodiment, the third energy level EL3 is the VBM energy level in the photoelectric conversion unit 104, but the present invention is not limited thereto. For example, when the i-type semiconductor used in the photoelectric conversion unit 104 is an organic semiconductor, the third energy level EL3 may also be the energy level of the highest occupied molecular orbital (HOMO energy level) in the photoelectric conversion unit 104.

[0136] Although the present invention has been described based on various drawings and various embodiments, those skilled in the art can make various deformations and modifications based on the present invention. Therefore, these deformations and modifications are included in the scope of the present invention. For example, the functions included in each functional unit and each step can be reconfigured in a logically non-contradictory manner, and multiple functional units and steps can be combined into one, or divided. In addition, the present invention is not limited to the faithful implementation of the above-mentioned embodiments. Some features of each embodiment can be appropriately combined, and a part of each embodiment can also be omitted.

[0137] <2-3. Summary of the present invention>

[0138] The present invention includes the following contents.

[0139] In one embodiment, (1) a solar cell element comprises: a first electrode portion; a photoelectric conversion portion; and a first carrier transport portion, the first carrier transport portion being located between the first electrode portion and the photoelectric conversion portion. The energy level of the highest occupied molecular orbital of a first surface of the first carrier transport portion, i.e., a first energy level, is lower than the energy level of the highest occupied molecular orbital of a second surface, i.e., a second energy level, wherein the first surface is a surface in contact with the photoelectric conversion portion, and the second surface is a surface in contact with the first electrode portion.

[0140] (2) In the solar cell element of (1) above, an energy level of the highest occupied molecular orbital of the first carrier transporting section increases from the first surface to the second surface along a first direction from the first surface to the second surface.

[0141] (3) In the solar cell element according to any one of (1) to (2) above, the first energy level is substantially the same as the third energy level, and the third energy level is the energy level of the valence band top of the photoelectric conversion portion.

[0142] (4) In the solar cell element according to any one of (1) to (3) above, the second energy level is substantially the same as a fourth energy level, and the fourth energy level is the Fermi level of the first electrode portion.

[0143] (5) In the solar cell element of any one of (1) to (4) above, the first carrier transporting section has a first region having a first predetermined thickness along the first direction from the first surface, and an energy level of the highest occupied molecular orbital of the first carrier transporting section in the first region is substantially the same as the third energy level.

[0144] (6) In the solar cell element of any one of (1) to (5) above, the first carrier transporting section further includes a second region having a second predetermined thickness from the second surface in a direction opposite to the first direction. The energy level of the highest occupied molecular orbital of the first carrier transporting section in the second region is substantially the same as the fourth energy level.

[0145] (7) In the solar cell element of any one of (1) to (6) above, the first carrier transport section further includes a third region between the first region and the first electrode section, wherein the energy level of the highest occupied molecular orbital of the first carrier transport section in the third region increases along the first direction.

[0146] (8) In the solar cell element of any one of (1) to (7) above, the first carrier transport section further includes a fourth region between the first region and the second region. The energy level of the highest occupied molecular orbital of the first carrier transport section in the fourth region is substantially the same as a fifth energy level, and the fifth energy level is an energy level that is higher than the first energy level and lower than the second energy level.

[0147] (9) In the solar cell element of any one of (1) to (8) above, the first carrier transport portion has: a first interface layer located between the first region and the fourth region; and a second interface layer located between the second region and the fourth region.

[0148] In one embodiment, (10) a solar cell module comprises: a first electrode portion; a photoelectric conversion portion; and a first carrier transport portion, the first carrier transport portion being located between the first electrode portion and the photoelectric conversion portion. The energy level of the highest occupied molecular orbital of a first surface of the first carrier transport portion, i.e., a first energy level, is lower than the energy level of the highest occupied molecular orbital of a second surface, i.e., a second energy level, wherein the first surface is a surface in contact with the photoelectric conversion portion, and the second surface is a surface in contact with the first electrode portion.

[0149] (11) In the solar cell module of (10) above, the energy level of the highest occupied molecular orbital of the first carrier transporting section increases from the first surface to the second surface along a first direction from the first surface to the second surface.

[0150] (12) In the solar cell module of any one of (10) to (11) above, the first energy level is substantially the same as a third energy level, and the third energy level is an energy level of the valence band top of the photoelectric conversion unit.

[0151] (13) In the solar cell module of any one of (10) to (12) above, the second energy level is substantially the same as a fourth energy level, and the fourth energy level is the Fermi level of the first electrode portion.

[0152] (14) In the solar cell module of any one of (10) to (13) above, the first carrier transporting portion has a first region having a first predetermined thickness along the first direction from the first surface, and an energy level of the highest occupied molecular orbital of the first carrier transporting portion in the first region is substantially the same as the third energy level.

[0153] (15) In the solar cell module of any one of (10) to (14) above, the first carrier transporting portion further includes a second region having a second predetermined thickness from the second surface in a direction opposite to the first direction. The energy level of the highest occupied molecular orbital of the first carrier transporting portion in the second region is substantially the same as the fourth energy level.

[0154] (16) In the solar cell module of any one of (10) to (15) above, the first carrier transport section further includes a third region between the first region and the first electrode section, wherein the energy level of the highest occupied molecular orbital of the first carrier transport section in the third region increases along the first direction.

[0155] (17) In the solar cell module of any one of (10) to (16) above, the first carrier transport section further includes a fourth region between the first region and the second region. The energy level of the highest occupied molecular orbital of the first carrier transport section in the fourth region is substantially the same as a fifth energy level, and the fifth energy level is an energy level that is higher than the first energy level and lower than the second energy level.

[0156] (18) In the solar cell module of any one of (10) to (17) above, the first carrier transport portion has: a first interface layer located between the first region and the fourth region; and a second interface layer located between the second region and the fourth region.

[0157] In one embodiment, in a method for manufacturing a solar cell element (11), there are: a first step of forming a photoelectric conversion portion; a second step of forming a dopant layer on the photoelectric conversion portion; a third step of forming a first carrier transport portion on the dopant layer; and a fourth step of forming a first electrode portion on the first carrier transport portion.

[0158] Description of Reference Numerals

[0159] 1: Solar cell module

[0160] 10: Solar cell components

[0161] 101: Substrate part

[0162] 102: Second electrode part

[0163] 103: Second carrier transport unit

[0164] 104: Photoelectric conversion unit

[0165] 105: First carrier transport unit

[0166] 1051: First Area

[0167] 1052: Second Area

[0168] 1053: Third Area

[0169] 1054: The Fourth Area

[0170] 1055: First interface layer

[0171] 1056: Second interface layer

[0172] 106: First electrode part

[0173] F1: First component surface

[0174] F2: Second component surface

[0175] CF1: First Side

[0176] CF2: Side 2

[0177] EL1: First Energy Level

[0178] EL2: Second energy level

[0179] EL3: The third energy level

[0180] EL4: fourth energy level

[0181] EL5: Fifth Energy Level

[0182] 20: Wire

[0183] 30: Current collection

[0184] 40: Solar cell components

Claims

1. A solar cell element, wherein: The solar cell element has: a first electrode portion; Photoelectric conversion unit; as well as a first carrier transporting portion, the first carrier transporting portion being located between the first electrode portion and the photoelectric conversion portion, The first carrier transport portion has a first surface that is in contact with the photoelectric conversion portion and a second surface that is in contact with the first electrode portion. In the first carrier transporting region, a first energy level of a highest occupied molecular orbital in a first interface region along the first face is lower than a second energy level of a highest occupied molecular orbital in a second interface region along the second face.

2. The solar cell element according to claim 1, wherein The energy level of the highest occupied molecular orbital of the first carrier transporting section increases from the first interface region to the second interface region along a first direction from the first face to the second face.

3. The solar cell element according to claim 1 or 2, wherein: The first energy level is substantially the same as a third energy level, and the third energy level is an energy level at the top of a valence band in the photoelectric conversion unit.

4. The solar cell element according to claim 3, wherein The first carrier transport portion includes a first region arranged along the first surface, The first region has a first predetermined thickness from the first surface along a first direction from the first surface to the second surface, The energy level of the highest occupied molecular orbital in the first region is substantially the same as the third energy level.

5. The solar cell element according to claim 4, wherein The first carrier transport portion includes a third region located between the first region and the first electrode portion, The energy level of the highest occupied molecular orbital in the third region increases along the first direction.

6. The solar cell element according to any one of claims 1 to 3, wherein The second energy level is substantially the same as a fourth energy level, and the fourth energy level is a Fermi level in the first electrode portion.

7. The solar cell element according to claim 6, wherein The first carrier transport portion includes a second region arranged along the second surface, The second region has a second predetermined thickness along a second direction from the second surface, the second direction being opposite to a first direction from the first surface to the second surface, The energy level of the highest occupied molecular orbital in the second region is substantially the same as the fourth energy level.

8. The solar cell element according to claim 7, wherein The first carrier transport section includes a third region between the second region and the photoelectric conversion section, The energy level of the highest occupied molecular orbital in the third region increases along the first direction.

9. The solar cell element according to claim 4, wherein The second energy level is substantially the same as a fourth energy level, and the fourth energy level is a Fermi level in the first electrode portion.

10. The solar cell element according to claim 9, wherein The first carrier transport portion includes a second region arranged along the second surface, The second region has a second predetermined thickness from the second surface along a second direction opposite to the first direction, The energy level of the highest occupied molecular orbital in the second region is substantially the same as the fourth energy level.

11. The solar cell element according to claim 10, wherein The first carrier transport portion includes a third region located between the first region and the second region, The energy level of the highest occupied molecular orbital in the third region increases along the first direction.

12. The solar cell element according to claim 10, wherein The first carrier transport portion further includes a fourth region located between the first region and the second region. The energy level of the highest occupied molecular orbital in the fourth region is substantially the same as the fifth energy level, and the fifth energy level is an energy level between the first energy level and the second energy level.

13. The solar cell element according to claim 12, wherein The first carrier transport portion includes a first interface layer located between the first region and the fourth region, The energy level of the highest occupied molecular orbital in the first interface layer is greater than or equal to the energy level of the highest occupied molecular orbital in the first region and less than or equal to the energy level of the highest occupied molecular orbital in the fourth region.

14. The solar cell element according to claim 12 or 13, wherein The first carrier transport portion includes a second interface layer located between the second region and the fourth region, The energy level of the highest occupied molecular orbital in the second interface layer is greater than or equal to the energy level of the highest occupied molecular orbital in the fourth region and less than or equal to the energy level of the highest occupied molecular orbital in the second region.

15. A solar cell element, wherein: The solar cell element has: a first electrode portion; Photoelectric conversion unit; as well as a first carrier transporting portion, the first carrier transporting portion being located between the first electrode portion and the photoelectric conversion portion, The first carrier transport portion has a first surface that is in contact with the photoelectric conversion portion and a second surface that is in contact with the first electrode portion. In the first carrier transporting portion, a carrier density in a first interface region along the first surface is greater than a carrier density in a second interface region along the second surface.

16. A solar cell module, wherein: The solar cell module comprises: a first electrode portion; Photoelectric conversion unit; as well as a first carrier transporting portion, the first carrier transporting portion being located between the first electrode portion and the photoelectric conversion portion, The first carrier transport portion has a first surface that is in contact with the photoelectric conversion portion and a second surface that is in contact with the first electrode portion. In the first carrier transporting region, a first energy level of a highest occupied molecular orbital in a first interface region along the first face is lower than a second energy level of a highest occupied molecular orbital in a second interface region along the second face.

17. A method for manufacturing a solar cell element, wherein: The method for manufacturing the solar cell element comprises: The first step is to form a photoelectric conversion unit; The second step is to form a first carrier transport portion on the photoelectric conversion portion; and The third step is to form a first electrode portion on the first carrier transport portion. The second step includes: a second A step of forming a first layer on the photoelectric conversion unit; a second B step of forming a second layer on the first layer; and a second C step of heating the first layer and the second layer to diffuse the dopant contained in the first layer into the second layer, thereby generating the first carrier transport unit from the first layer and the second layer. the first layer has a higher concentration of dopant than the second layer, The second layer has a lower dopant concentration than the first layer, or the second layer does not contain a dopant, and the second layer includes a semiconductor material constituting the first carrier transporting portion.

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