Solar cell, multi-junction solar cell, solar cell module and solar power generation system

Abstract

The problem to be solved by the present invention is to provide a solar cell, a multi-junction solar cell, a solar cell module and a solar power generation system with excellent conversion efficiency. The solar cell of the embodiment comprises: a p-electrode (2); an n-electrode (5); a p-type light absorbing layer (3) mainly composed of cuprous oxide; and an n-type layer (4) having a first n-type layer (4A) and a second n-type layer (4B) or having a first n-region (4a) and a second n-region (4b), wherein the first n-type layer (4A) and the first n-region (4a) are composed of Ga x1 M1 x2 M2 x3 M3 x4 O x5 The compound represented by is a main component, M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, M3 is one or more selected from the group consisting of Sn, Si and Ge, x1 and x5 are values ​​greater than 0, x2, x3 and x4 are values ​​greater than 0, when the sum of x1, x2, x3 and x4 is set to 2, x5 is greater than 3.0 and less than 3.8, and the second n-type layer (4B) and the second n region (4b) are Ga y1 M1 y2 M2 y3 M3 y4 O y5 The compound represented is mainly composed of y1 and y5, which are values ​​greater than 0, y2, y3 and y4, which are values ​​greater than 0, and y5, which is greater than 3.0 and less than 3.8 when the sum of y1, y2, y3 and y4 is 2. (x2+x3) is greater than (y2+y3).

Description

Technical Field

[0001] The invention relates to a solar cell, a multi-junction solar cell, a solar cell module and a solar power generation system. Background Art

[0002] One of the new solar cells is a solar cell that uses cuprous oxide (Cu2O) in the light absorption layer. Cu2O is a wide bandgap semiconductor. Cu2O is a safe and inexpensive material composed of copper and oxygen, which are abundant on the earth, and is expected to realize high-efficiency and low-cost solar cells.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-46196 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The problem to be solved by the present invention is to provide a solar cell, a multi-junction solar cell, a solar cell module and a solar power generation system having excellent conversion efficiency.

[0008] Means for solving problems

[0009] The solar cell of the embodiment comprises: a p-electrode; an n-electrode; a p-type light absorbing layer, which is located between the p-electrode and the n-electrode and is mainly composed of cuprous oxide; and an n-type layer, which has a first n-type layer and a second n-type layer, or has a first n region and a second n region, wherein the first n-type layer is located between the p-type light absorbing layer and the n-electrode and is mainly composed of Ga x1 M1 x2 M2 x3 M3 x4 O x5 The layer is mainly composed of the compound represented by, M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, M3 is one or more selected from the group consisting of Sn, Si and Ge, x1 and x5 are values ​​greater than 0, x2, x3 and x4 are values ​​greater than 0, and when the sum of x1, x2, x3 and x4 is set to 2, x5 is greater than 3.0 and less than 3.8; the second n-type layer is located between the first n-type layer and the n-electrode and is composed of Ga y1 M1 y2 M2 y3 M3 y4 O y5The compound represented by is the main layer, y1 and y5 are values ​​greater than 0, y2, y3 and y4 are values ​​greater than 0, and when the sum of y1, y2, y3 and y4 is set to 2, y5 is greater than 3.0 and less than 3.8; the first n region is located between the p-type light absorbing layer and the n-electrode, and is Ga x1 M1 x2 M2 x3 M3 x4 O x5 The compound represented by is used as the main body, M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, M3 is one or more selected from the group consisting of Sn, Si and Ge, x1 and x5 are values ​​greater than 0, x2, x3 and x4 are values ​​greater than 0, and when the sum of x1, x2, x3 and x4 is set to 2, x5 is greater than 3.0 and less than 3.8; the second n region is located between the first n region and the n electrode, and Ga y1 M1 y2 M2 y3 M3 y4 O y5 The compound represented is mainly composed of y1 and y5, which are values ​​greater than 0, y2, y3 and y4, which are values ​​greater than 0, and y5, which is greater than 3.0 and less than 3.8 when the sum of y1, y2, y3 and y4 is 2. (x2+x3) is greater than (y2+y3). BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view of a solar cell according to an embodiment.

[0011] Figure 2 It is a diagram for explaining analysis points of the solar cell according to the embodiment.

[0012] Figure 3 is a cross-sectional view of a solar cell according to an embodiment.

[0013] Figure 4 is a cross-sectional view of a solar cell according to an embodiment.

[0014] Figure 5 is a cross-sectional view of a solar cell according to an embodiment.

[0015] Figure 6 It is a cross-sectional view of a multi-junction solar cell according to an embodiment.

[0016] Figure 7 It is a perspective view of a solar cell module according to the embodiment.

[0017] Figure 8 It is a cross-sectional view of a solar cell module according to an embodiment.

[0018] Fig. 9 It is a configuration diagram of a solar power generation system according to an embodiment.

[0019] Fig.10 It is a schematic diagram of a vehicle according to an embodiment.

[0020] Fig.11 This is a table about the n-type layer of the example.

[0021] Fig.12 This is a table about the n-type layer of the example.

[0022] Fig.13 It is a graph showing the pattern of composition change in the examples.

[0023] Fig.14 It is a graph showing the pattern of composition change in the examples.

[0024] Fig.15 This is a table about the embodiments. DETAILED DESCRIPTION

[0025] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specified, values ​​are expressed at 25° C. and 1 atmosphere (atmosphere).

[0026] (First embodiment)

[0027] The first embodiment relates to a solar cell. Figure 1 2 is a cross-sectional view of a solar cell 100 according to the first embodiment. Figure 1 As shown in , the solar cell 100 of the present embodiment has a substrate 1, a p-electrode 2 as a first electrode, a p-type light absorbing layer 3, an n-type layer 4, and an n-electrode 5 as a second electrode. In the first embodiment, the n-type layer 4 includes a first n-type layer 4A and a second n-type layer 4B. An intermediate layer not shown may be included between the n-type layer 4 and the n-electrode 5. Sunlight may be incident from either the n-electrode 5 side or the p-electrode 2 side, but is more preferably incident from the n-electrode 5 side. Since the solar cell 100 of the embodiment is a transmission-type solar cell, it is preferably used for the top unit (light incident side) of a multi-junction solar cell. Figure 1 In the embodiment, the substrate 1 is disposed on the side of the p-electrode 2 opposite to the p-type light absorbing layer 3, but the substrate 1 may be disposed on the side of the n-electrode 5 opposite to the n-type layer 4. Figure 1 The embodiment shown in FIG. 1 is described, but the embodiment in which the substrate 1 is provided on the n-electrode 5 side is the same except that the position of the substrate 1 is different. In the solar cell 100 of the embodiment, light is incident from the n-electrode 5 side toward the p-electrode 2 side.

[0028] The substrate 1 is a transparent substrate. For the substrate 1, an organic substrate such as polyacrylate, polyimide, polycarbonate, polyethylene terephthalate (PET), polypropylene (PP), fluorine resin (polytetrafluoroethylene (PTFE), perfluoroethylene propylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxyalkane (PFA), etc.), polyarylate, polysulfone, polyethersulfone or polyetherimide, or an inorganic substrate such as soda-lime glass, white plate glass, chemically strengthened glass or quartz, which transmits light, can be used. For the substrate 1, the above-mentioned substrates can also be stacked.

[0029] The p-electrode 2 is provided on the substrate 1 and disposed between the substrate 1 and the p-type light absorbing layer 3. The p-electrode 2 is a light-transmitting conductive layer provided on the side of the p-type light absorbing layer 3. The thickness of the p-electrode 2 is typically 100 nm to 2,000 nm. Figure 1In the embodiment, the p-electrode 2 is in direct contact with the light absorbing layer 3. The p-electrode 2 preferably includes one or more oxide transparent conductive films. The oxide transparent conductive film may be indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), gallium-doped zinc oxide (GZO), doped tin oxide, titanium-doped indium oxide (ITiO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), hydrogen-doped indium oxide (IOH), etc., without particular limitation. The oxide transparent conductive film may also be a laminated film having a multilayer film. As dopants in films such as tin oxide, there is no particular limitation as long as it is one or more selected from the group consisting of In, Si, Ge, Ti, Cu, Sb, Nb, Ta, W, Mo, F and Cl. The p-electrode 2 preferably includes a tin oxide film doped with one or more elements selected from the group consisting of In, Si, Ge, Ti, Cu, Sb, Nb, Ta, W, Mo, F and Cl. In the doped tin oxide film, one or more elements selected from the group consisting of In, Si, Ge, Ti, Cu, Sb, Nb, Ta, W, Mo, F and Cl preferably contain 10 atomic % or less relative to the tin contained in the tin oxide film. As the p-electrode 2, a laminated film obtained by laminating an oxide transparent conductive film and a metal film can be used. The metal film preferably has a thickness of less than 10 nm, and the metal (including alloy) contained in the metal film is Mo, Au, Cu, Ag, Al, Ta or W, etc., without particular limitation. In addition, the p-electrode 2 preferably includes a dot-shaped, linear or mesh-shaped electrode (selected from one or more of the group consisting of metal, alloy, graphene, conductive nitride and conductive oxide) between the oxide transparent conductive film and the substrate 1, or between the oxide transparent conductive film and the p-type light absorbing layer 3. The dot-shaped, linear or mesh-shaped metal preferably has an opening ratio of 50% or more relative to the transparent conductive film. The dot-shaped, linear or mesh-shaped metal is Mo, Au, Cu, Ag, Al, Ta or W, etc., without particular limitation. When a metal film is used in the p-electrode 2, it is preferably set to a film thickness of about 5 nm or less from the viewpoint of transmittance. When a linear or mesh-shaped metal film is used, since transmittance is ensured by the opening portion, the film thickness of the metal film is not limited thereto.

[0030] The p-type light absorbing layer 3 is a p-type semiconductor layer. The p-type light absorbing layer 3 may also be in direct contact with the p-electrode 2, and other layers may also be present as long as the contact with the p-electrode 2 can be ensured. The p-type light absorbing layer 3 is arranged between the electrode 2 and the first n-type layer 4A. The p-type light absorbing layer 3 forms a pn junction with the first n-type layer 4A. The p-type light absorbing layer 3 is a semiconductor layer of a metal oxide with Cu as a main component. The metal oxide with Cu as a main component is a composite oxide of cuprous oxide or / and cuprous oxide. Preferably, more than 90wt% of the p-type light absorbing layer 3 is a composite oxide of cuprous oxide or / and cuprous oxide. More preferably, more than 95wt% of the p-type light absorbing layer 3 is a composite oxide of cuprous oxide or / and cuprous oxide. Even more preferably, more than 98wt% of the p-type light absorbing layer 3 is a composite oxide of cuprous oxide or / and cuprous oxide. The p-type light absorbing layer 3 preferably contains substantially no Cu or / and CuO as a heterophase. If the p-type light absorbing layer 3 contains fewer heterophases and has good crystallinity, the light transmittance of the p-type light absorbing layer 3 becomes higher, so it is preferred. For the oxide of the metal with Cu as the main component, Cu is 60.0 atom% or more and 67.0 atom% or less, and O (oxygen) is 32.5 atom% or more and 34.0 atom% or less. The composite oxide of cuprous oxide contains metals other than Cu. The metal contained in the composite oxide of cuprous oxide is, in addition to Cu, one or more metals selected from the group consisting of Sn, Sb, Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg and Ca. If, in addition to Cu, one or more metals selected from the group consisting of Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg and Ca are contained, the band gap of the p-type light absorbing layer 3 can be adjusted. The band gap of the p-type light absorbing layer 3 is preferably 2.0 eV or more and 2.2 eV or less. If the band gap is within the above range, in a multi-junction solar cell in which a solar cell using Si in the light absorbing layer is used for the bottom unit and the solar cell of the embodiment is used for the top unit, sunlight can be efficiently used in both the top unit and the bottom unit. The p-type light absorbing layer 3 may further contain Sn or Sb. The Sn or Sb in the p-type light absorbing layer 3 may be Sn or Sb added to the light absorbing layer 3 or may be Sn or Sb derived from the p-electrode 2. The p-type light absorbing layer 3 is Cu a M b O cThe layer of oxide represented by. M is one or more metals selected from the group consisting of Sn, Sb, Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg and Ca. a, b and c preferably satisfy 1.80≤a≤2.01, 0.00≤b≤0.20 and 0.98≤c≤1.02. The composition ratio of the p-type light absorbing layer 3 is the overall composition ratio of the p-type light absorbing layer 3. In addition, the compound composition ratio of the p-type light absorbing layer 3 is preferably satisfied in the p-type light absorbing layer 3 as a whole. It should be noted that if the concentration of Sn and Sb in the p-type light absorbing layer 3 is high, the defects increase and the carrier recombination increases. Therefore, the total volume concentration of Sb and Sn in the p-type light absorbing layer 3 is preferably 1.5x10 19 atoms / cm 3 Next, the compositions of the p-type light absorbing layer 3 and the first n-type layer 4A were determined by SIMS (Secondary Ion Mass Spectrometry). The average value of the values ​​determined in the same manner as for the p-electrode 2 can be used as the composition of each layer.

[0031] The thickness of the p-type light absorbing layer 3 is determined by cross-sectional observation using an electron microscope or a step analyzer, and is preferably 1,000 nm or more and 10,000 nm or less.

[0032] The p-type light absorbing layer 3 is preferably formed by, for example, sputtering.

[0033] The n-type layer 4 includes a first n-type layer 4A and a second n-type layer 4B.

[0034] The first n-type layer 4A is an n-type semiconductor layer. The first n-type layer 4A is arranged between the p-type light absorbing layer 3 and the second n-electrode 4B. The second n-type layer 4B is arranged between the first n-type layer 4A and the n-electrode 5. The first n-type layer 4A is in direct contact with the surface of the p-type light absorbing layer 3 opposite to the surface in contact with the p-electrode 2. Preferably, the first n-type layer 4A is an oxide semiconductor layer containing Ga and containing a compound based on Ga. In addition to the oxide based on Ga, the first n-type layer 4A can also be mixed with other oxides, the oxide based on Ga can also be doped with other elements, and the Ga-based oxide doped with other elements and other oxides can also be mixed.

[0035] Preferably, the first n-type layer 4A is Ga x1 M1 x2 M2 x3 M3 x4 O x5A layer having the compound represented as the main body (more than 50wt%), and M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, and M3 is one or more selected from the group consisting of Sn, Si and Ge. x1, x2 and x5 are values ​​greater than 0. x3 and x4 are values ​​greater than 0. When the sum of x1, x2, x3 and x4 is set to 2, x5 is preferably greater than 3.0 and less than 3.8. The form of other oxides mixed in the Ga-based oxide, the form of other elements doped in the Ga-based oxide, and the form of Ga-based oxide doped with other elements mixed with other oxides are all Ga-based. x1 M1 x2 M2 x3 M3 x4 O x5 express.

[0036] Preferably, 90 wt% or more of the first n-type layer 4A is Ga x1 M1 x2 M2 x3 M3 x4 O x5 More preferably, 95 wt% or more of the first n-type layer 4A is Ga x1 M1 x2 M2 x3 M3 x4 O x5 More preferably, 98 wt % or more of the first n-type layer 4A is Ga x1 M1 x2 M2 x3 M3 x4 O x5 More preferably, the first n-type layer 4A is composed of Ga x1 M1 x2 M2 x3 M3 x4 O x5 The compound composition represented.

[0037] It should be noted that the composition of the compound of the first n-type layer 4A is the average composition of the first n-type layer 4A as a whole unless there are any special additional conditions. When the thickness of the first n-type layer 4A is set to d, the composition of the first n-type layer 4A is the average of the compositions at depths of 0.2d, 0.5d, and 0.8d from the surface of the first n-type layer 4A on the side of the p-type light absorbing layer 3. Except for the case where there is a condition where the elemental composition ratio of the compound of the first n-type layer 4A is inclined, at each depth, the first n-type layer 4A preferably satisfies the preferred compositions described above and below. It should be noted that when the first n-type layer 4A is very thin (for example, less than 5 nm), the composition at a depth of 0.5d from the surface of the first n-type layer 4A on the side of the p-type light absorbing layer 3 can be regarded as the overall composition of the first n-type layer 4A. It should be noted that for analysis, for example, by secondary ion mass spectroscopy (SIMS), the composition of the first n-type layer 4A at each distance from the surface of the n-type layer is measured. Figure 2 The value is obtained by analyzing analysis points that are equally spaced and distributed as closely as possible as shown in the analysis points of . Figure 2 This is a schematic diagram of the solar cell 100 as viewed from the light incident side. D1 is the length of the first n-type layer 4A in the width direction, and D2 is the length of the first n-type layer 4A in the depth direction.

[0038] The first n-type layer 4A is preferably such that the difference between the conduction band minimum (CBM, which may also be referred to as the conduction band bottom) of the p-type light absorbing layer 3 and the conduction band minimum of the first n-type layer 4A becomes small. The conduction band minimum of Ga2O3 is very low compared to the p-type light absorbing layer 3. In order to reduce the difference in the conduction band minimum, the element M1 is included in the compound of the first n-type layer 4A. The difference between the conduction band minimum of the p-type light absorbing layer 3 and the conduction band minimum of the first n-type layer 4A ([conduction band minimum of the p-type light absorbing layer 3] - [conduction band minimum of the first n-type layer 4A]) is preferably 0.0 eV or more and 0.4 eV or less.

[0039] The first n-type layer 4A of the embodiment mainly adjusts the conduction band minimum by the elements of Ga and M1. By increasing the element ratio of M1, the conduction band minimum of the first n-type layer 4A increases, and the difference in the conduction band minimum of the p-type light absorbing layer 3 can be reduced. Therefore, (x1+x2) / (x1+x2+x3+x4) is preferably greater than 0.50 and less than 1.00. From this viewpoint, in the first n-type layer 4A, (x1+x2) / (x1+x2+x3+x4) is preferably greater than 0.80 and less than 1.00, and more preferably greater than 0.90 and less than 1.00. As the element of M1, Al or Al and B are preferably Al. By using an oxide based on the elements of Ga and M1 in the first n-type layer 4A, the conversion efficiency is improved, so it is preferred that x2 is greater than x3 and greater than x4. From this viewpoint, x2 is preferably greater than 2 times of x3 and greater than 2 times of x4.

[0040] x2 / (x1+x2) is preferably 0.00 or more and 0.50 or less. When x2 / (x1+x2) is greater than 0.50, a spike is generated in which the conduction band of the pn junction interface becomes discontinuous, and the FF becomes low, so it is difficult to obtain a solar cell with high conversion efficiency. x2 / (x1+x2) is more preferably 0.10 or more and 0.40 or less, and more preferably 0.10 or more and 0.35 or less.

[0041] The compound of the first n-type layer 4A may include one or more selected from the group consisting of In, Ti, Zn, Hf and Zr represented by M2. x3 / (x1+x2+x3+x4) is preferably greater than 0.00 and less than 0.50. In addition, the element of M2 can adjust the conduction band minimum of the first n-type layer 4A. If there are too many elements of M2, the difference between the conduction band minimums of the first n-type layer 4A and the p-type light absorbing layer 3 sometimes becomes larger. Therefore, x3 / (x1+x2+x3+x4) is more preferably greater than 0.00 and less than 0.10, and more preferably greater than 0.00 and less than 0.05.

[0042] The compound of the first n-type layer 4A may include one or more selected from the group consisting of Sn, Si and Ge represented by M3. If the element M4 is included in the first n-type layer 4A, the carrier concentration of the first n-type layer 4A can be increased. x4 / (x1+x2+x3+x4) is preferably greater than or equal to 0.00 and less than or equal to 0.15, and more preferably greater than or equal to 0.00 and less than or equal to 0.10. x4 is preferably less than (x2+x3).

[0043] One or more selected from the group consisting of Ga, M1 elements, M2 elements and M3 elements may also change the composition ratio in the first n-type layer 4A along the film thickness direction of the first n-type layer 4A. The M3 element is preferably less on the p-type light absorbing layer 3 side and more on the second n-type layer 4B side. The M1 element is preferably more on the p-type light absorbing layer 3 side and less on the second n-type layer 4B side. The change in composition is preferably inclined, stepped, or a combination of inclined and stepped changes. In addition, the change in composition is overall or partial in the stacking direction of each layer of the solar cell 100. By changing the composition distribution of these elements, the carrier concentration, conduction band minimum and refractive index can be adjusted from the p-type light absorbing layer 3 side toward the n-electrode 5 side, which can help improve the conversion efficiency.

[0044] When the thickness of the first n-type layer 4A is set to d 4A In the case of , from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side to 0.25d 4A The area d from the position A0-0.25 The element ratio of M1 in is preferably 1.10 times x2 (1.10 times x2 (average value of the first n-type layer 4A) (the same applies below)) or more and 2.50 times x2 (2.5 times x2 (average value of the first n-type layer 4A) (the same applies below)) or less. The distance from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.25d 4A The position of the second n-type layer 4B is 0.50d 4A The area d from the position A0.25-0.50 The element ratio of M1 in x2 is preferably 0.75 times or more and 1.50 times or less. The distance from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.50d 4A The position of the second n-type layer 4B is 0.75d 4A The area d from the position A0.50-0.75 The element ratio of M1 in x2 is preferably 0.30 times or more and 1.50 times or less. The distance from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.75d 4A The position toward the second n-type layer 4B is 1.00d 4A The area d from the position A0.75-1 The element ratio of M1 in x2 is preferably 0.10 times or more and 0.90 times or less. In addition, when the composition changes, if the continuity of the connection of the conduction band minimum is considered, the composition change of the elements contained in the n-type layer 4 is preferably unidirectional. Specifically, region d A0-0.25 The element ratio of M1 in the region d is preferably A0.25-0.50 The element ratio of M1 in area d is aboveA0.25-0.50 The element ratio of M1 in the region d is preferably A0.50-0.75 The element ratio of M1 in area d is above A0.50-0.75 The element ratio of M1 in the region d is preferably A0.75-1 From this point of view, region d A0.75-1 The element ratio of M1 in the region d is preferably A0-0.25 When the composition of M1 changes, as described above, region d A0-0.25 x2 / (x1+x2) and area d in A0.25-0.50 Also, x2 / (x1+x2) in φ is more preferably 0.10 to 0.40, and more preferably 0.10 to 0.35.

[0045] If the composition of Ga changes greatly, the composition of elements other than Ga will change greatly, and the continuity of the connection of the conduction band minimum will deteriorate. Therefore, when the composition of Ga changes, its change rate is preferably smaller than the change rate of the composition of the elements of M1. When the thickness of the first n-type layer 4A is set to d 4A In the case of , from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side to 0.25d 4A The area d from the position A0-0.25 The Ga ratio in is preferably greater than 0.75 times x1 (0.75 times x1 (average value of the first n-type layer 4A) (the same applies below)) and less than 0.98 times (0.98 times x1 (average value of the first n-type layer 4A) (the same applies below)). The Ga ratio from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.25d 4A The position of the second n-type layer 4B is 0.50d 4A The area d from the position A0.25-0.50 The Ga element ratio in is preferably 0.80 times or more and 1.10 times or less of x1. The distance from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.50d 4A The position of the second n-type layer 4B is 0.75d 4A The area d from the position A0.50-0.75 The Ga element ratio in is preferably 0.90 times or more and 1.20 times or less of x1. The distance from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side toward the second n-type layer 4B side is 0.75d 4A The position toward the second n-type layer 4B is 1.00d 4A The area d from the position A0.75-1The Ga element ratio in the n-type layer 4 is preferably 1.02 times or more and 1.25 times or less of x1. In addition, when the composition changes, if the continuity of the connection of the conduction band minimum is considered, the composition change of the elements contained in the n-type layer 4 is preferably unidirectional. Specifically, in the region d A0-0.25 The Ga element ratio in the region d is preferably A0.25-0.50 The element ratio of Ga in region d is less than A0.25-0.50 The Ga element ratio in the region d is preferably A0.50-0.75 The element ratio of Ga in region d is less than A0.50-0.75 The Ga element ratio in the region d is preferably A0.75-1 The element ratio of Ga in is less than .

[0046] The first n-type layer 4A is preferably formed by, for example, sputtering or ALD (Atomic Layer Deposition).

[0047] The second n-type layer 4B is located between the first n-type layer 4A and the n-electrode 5. The surface of the second n-type layer 4B on the side of the first n-type layer 4A is in direct contact with the first n-type layer 4A. Preferably, the second n-type layer 4B is an oxide semiconductor layer containing Ga and contains a compound based on Ga. The interface between the first n-type layer 4A and the second n-type layer 4B may be clear or unclear. The second n-type layer 4B may be a mixture of other oxides in an oxide based on Ga, may be doped with other elements in an oxide based on Ga, or may be a mixture of Ga-based oxides doped with other elements with other oxides. An intermediate layer not shown in the figure may be provided between the second n-type layer 4B and the n-electrode 5.

[0048] Preferably, the second n-type layer 4B is Ga y1 M1 y2 M2 y3 M3 y4 O y5 The layer has the compound represented as the main body (more than 50wt%), M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, and M3 is one or more selected from the group consisting of Sn, Si and Ge. y1 and y5 are values ​​greater than 0. y2, y3 and y4 are values ​​greater than 0. When the sum of y1, y2, y3 and y4 is set to 2, y5 is preferably greater than 3.0 and less than 3.8. The form of other oxides mixed in the Ga-based oxide, the form of other elements doped in the Ga-based oxide, and the form of Ga-based oxide doped with other elements mixed with other oxides are all Ga-based. y1 M1 y2 M2 y3M3 y4 O y5 express.

[0049] From the viewpoint of improving the continuity of the connection from the p-type light absorbing layer 3 to the conduction band minimum of the second n-type layer 4B, (x2+x3) is preferably greater than (y2+y3). From this viewpoint, (y2+y3) is preferably 0.8 times or less of (x2+x3), more preferably 0.5 times or less of (x2+x3), and even more preferably 0.3 times or less of (x2+x3).

[0050] Preferably, 90 wt% or more of the second n-type layer 4B is Ga y1 M1 y2 M2 y3 M3 y4 O y5 More preferably, 95 wt% or more of the second n-type layer 4B is Ga y1 M1 y2 M2 y3 M3 y4 O y5 More preferably, 98 wt % or more of the second n-type layer 4B is Ga y1 M1 y2 M2 y3 M3 y4 O y5 More preferably, the second n-type layer 4B is composed of Ga y1 M1 y2 M2 y3 M3 y4 O y5 The compound composition represented.

[0051] The second n-type layer 4B mainly adjusts the conduction band minimum by the elements of Ga and M1. By making the element ratio of M1 of the second n-type layer 4B less than that of the first n-type layer 4A and increasing the ratio of Ga (y1 is greater than x1, y2 is less than x2), the conduction band minimum of the second n-type layer 4A is lower than that of the first n-type layer 4A. Moreover, the continuity of the connection of the conduction band minimum between the first n-type layer 4A and the n-electrode 5 is improved. In the second n-type layer 4B, (y1+y2) / (y1+y2+y3+y4) is preferably greater than 0.65 and less than 1.00. From this viewpoint, in the second n-type layer 4B, (y1+y2) / (y1+y2+y3+y4) is preferably greater than 0.80 and less than 1.00, and more preferably greater than 0.90 and less than 1.00.

[0052] The second n-type layer 4B is a layer having a conduction band minimum value lower than that of the first n-type layer 4A, and the conduction band minimum value of the second n-type layer 4B is located between the first n-type layer 4A and the n-electrode 5. By using the second n-type layer 4B, the conduction band minimum values ​​are continuously connected from the p-type light absorbing layer 3 to the n-electrode 5, and FF and Voc are improved, which contributes to the improvement of conversion efficiency. In the case where y2 is a value greater than 0, it is preferred that the second n-type layer 4B also has an element of M1 common to the first n-type layer 4A. That is, if Al is contained in the first n-type layer 4A, it is preferred that Al is contained rather than not being contained in the second n-type layer 4B. Moreover, since y1 is greater than x1 and y2 is less than x2, the lower end of the conductor of the second n-type layer 4B becomes lower than the conduction band minimum value of the first n-type layer 4A, and the continuity of the connection of the conduction band minimum value is improved. From this viewpoint, y2 / (y1+y2) is preferably 0.00 or more and 0.30 or less, and more preferably 0.00 or more and 0.20 or less. In addition, if x2 and y2 are close values, the continuity of the connection of the conduction band minimum brought about by the provision of the second n-type layer 4B is less improved. Therefore, y2 is preferably 90% or less of x2, y2 is more preferably 80% or less of x2, and y2 is more preferably 70% or less of x2.

[0053] The numerical value of y3 is preferably the preferred numerical value of x3 and x4 in the first embodiment. Therefore, y3 / (y1+y2+y3+y4) is more preferably 0.00 to 0.10, and more preferably 0.00 to 0.05.

[0054] y4 / (y1+y2+y3+y4) is preferably greater than or equal to 0.00 and less than or equal to 0.15. If the element M3 is included, the carrier concentration of the second n-type layer 4B is preferably increased, and the carrier concentration of the second n-type layer 4B is preferably higher than that of the first n-type layer 4A, and (y4 is greater than x4). Therefore, y4 / (y1+y2+y3+y4) is more preferably greater than or equal to 0.01 and less than or equal to 0.15, and further preferably greater than or equal to 0.05 and less than or equal to 0.15.

[0055] The sum of the thickness of the first n-type layer 4A and the thickness of the second n-type layer 4B is typically greater than 3nm and less than 100nm. If the sum of the thickness of the first n-type layer 4A and the thickness of the second n-type layer 4B is less than 3nm, leakage current is generated when the effective area (coverage) of the first n-type layer 4A and the second n-type layer 4B is poor, and sometimes the characteristics are reduced. The effective area is not limited to the above-mentioned film thickness. If the sum of the thickness of the first n-type layer 4A and the thickness of the second n-type layer 4B exceeds 50nm, sometimes the characteristics are reduced due to the excessive high resistance of the n-type layer after the first n-type layer 4A and the second n-type layer 4B are combined, or the short-circuit current is reduced due to the reduction in transmittance. Therefore, the sum of the thickness of the first n-type layer 4A and the thickness of the second n-type layer 4B is more preferably greater than 3nm and less than 30nm, and more preferably greater than 5nm and less than 30nm.

[0056] One or more elements selected from the group consisting of Ga, M1 elements, M2 elements and M3 elements may also change the composition ratio in the second n-type layer 4B along the film thickness direction of the second n-type layer 4B. The M3 element is preferably less on the p-type light absorbing layer 3 side and more on the second n-type layer 4B side. The M1 element is preferably more on the p-type light absorbing layer 3 side and less on the second n-type layer 4B side. The change in composition is preferably inclined, stepped, or a combination of inclined and stepped changes. In addition, the change in composition is overall or partial in the stacking direction of each layer of the solar cell 100. By changing the composition distribution of these elements, the carrier concentration, conduction band minimum and refractive index can be adjusted from the p-type light absorbing layer 3 side toward the n-electrode 5 side, which can help improve the conversion efficiency.

[0057] When the thickness of the second n-type layer 4B is set to d 4B In the case of 4B The area d from the position B0-0.25 The element ratio of M1 in y2 is preferably 1.10 times (1.10 times (the average value of y2 in the second n-type layer 4B) (the same applies below)) or more and 4.00 times (4.00 times (the average value of y2 in the second n-type layer 4B) (the same applies below)) or less. The distance from the surface of the second n-type layer 4B on the first n-type layer 4A side to the n-electrode 5 side is 0.25d 4B The position toward the n-electrode 5 side is 0.50d 4B The area d from the position B0.25-0.50 The element ratio of M1 in y2 is preferably 0.00 times or more and 1.50 times or less. The distance from the surface of the second n-type layer 4B on the first n-type layer 4A side toward the n-electrode 5 side is 0.50d 4B The position toward the n-electrode 5 side is 0.75d 4BThe area d from the position B0.50-0.75 The element ratio of M1 in y2 is preferably 0.00 times or more and 1.25 times or less. The distance from the surface of the second n-type layer 4B on the first n-type layer 4A side toward the n-electrode 5 side is 0.75d 4B The position toward the n-electrode 5 side is 1.00d 4B The area d from the position B0.75-1 The element ratio of M1 in y2 is preferably 0.00 times or more and 0.90 times or less. In addition, when the composition changes, if the continuity of the connection of the conduction band minimum is considered, the composition change of the elements contained in the n-type layer 4 is preferably unidirectional. Specifically, region d B0-0.25 The element ratio of M1 in the region d is preferably B0.25-0.50 The element ratio of M1 in area d is above B0.25-0.50 The element ratio of M1 in the region d is preferably B0.50-0.75 The element ratio of M1 in area d is above B0.50-0.75 The element ratio of M1 in the region d is preferably B0.75-1 From this point of view, region d B0.75-1 The element ratio of M1 in the region d is preferably B0-0.25 The element ratio of M1 is less than half.

[0058] When the thickness of the second n-type layer 4B is set to d 4B In the case of 4B The area d from the position B0-0.25 The element ratio of M3 in y4 is preferably greater than 0.00 times (0.00 times (the same below) of y4 (the average value of the second n-type layer 4B)) and less than 0.75 times (0.75 times (the same below) of y4 (the average value of the second n-type layer 4B)). The distance from the surface of the second n-type layer 4B on the first n-type layer 4A side to the n-electrode 5 side is 0.25d 4B The position toward the n-electrode 5 side is 0.50d 4B The area d from the position B0.25-0.50 The element ratio of M3 in y4 is preferably 0.30 times or more and 1.50 times or less. The distance from the surface of the second n-type layer 4B on the first n-type layer side toward the n-electrode 5 side is 0.50d 4B The position toward the n-electrode 5 side is 0.75d 4B The area d from the position B0.50-0.75 The element ratio of M3 in y4 is preferably 0.75 times or more and 2.00 times or less. The distance from the surface of the second n-type layer 4B on the first n-type layer side toward the n-electrode 5 side is 0.75d 4BThe position toward the n-electrode 5 side is 1.00d 4B The area d from the position B0.75-1 The element ratio of M3 in y4 is preferably 1.10 times or more and 3.00 times or less. In addition, when the composition changes, if the continuity of the connection of the conduction band minimum is considered, the composition change of the elements contained in the n-type layer 4 is preferably unidirectional. Specifically, region d B0-0.25 The element ratio of M3 in the region d is preferably B0.25-0.50 The element ratio of M3 in area d is below B0.25-0.50 The element ratio of M3 in the region d is preferably B0.50-0.75 The element ratio of M3 in area d is below B0.50-0.75 The element ratio of M3 in the region d is preferably B0.75-1 In addition, from this point of view, the area d B0-0.25 The element ratio of M3 in the region d is preferably B0.75-1 The element ratio of M3 in is less than half.

[0059] The n-electrode 5 is an electrode on the side of the first n-type layer 4A that is translucent to visible light. The first n-type layer 4A is clamped by the n-electrode 5 and the p-type light absorbing layer 3. An intermediate layer not shown in the figure may be provided between the first n-type layer 4A and the n-electrode 5. The intermediate layer may include a mesh or wire-shaped electrode. For the n-electrode 5, it is preferred to use an oxide transparent conductive film. As the oxide transparent conductive film used in the n-electrode 5, it is preferred to select one or more transparent conductive films from the group consisting of indium tin oxide, aluminum-doped zinc oxide, boron-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, titanium-doped indium oxide, indium gallium zinc oxide and hydrogen-doped indium oxide. For the n-electrode 5, graphene may also be used. Graphene is preferably stacked with silver nanowires.

[0060] The thickness of the n-electrode 5 is determined by cross-sectional observation using an electron microscope or a step analyzer, and is not particularly limited, but is typically 1 nm to 2 μm.

[0061] The n-electrode 5 is preferably formed by, for example, sputtering.

[0062] (Second embodiment)

[0063] The second embodiment relates to a solar cell. Figure 3 2 shows a schematic cross-sectional view of a solar cell 101 according to the second embodiment. The solar cell 101 according to the second embodiment differs from the solar cell 100 according to the first embodiment in that the n-type layer 4 has a first region 4a and a second region 4b. The common descriptions of the first and second embodiments are omitted.

[0064] The first region 4a is located on the p-type light absorbing layer 3 side of the first n-type layer 4A. In addition, the second region 4b is located on the n-electrode 5 side of the first n-type layer 4A. In the first n-type layer 4A of the third embodiment, the composition on the p-type light absorbing layer 3 side and the n-electrode 5 side are significantly different, but the interface between the first region 4a and the second region 4b has not been confirmed. The area from the surface of the p-type light absorbing layer 3 side of the first n-type layer 4A toward the n-electrode 5 side to half the thickness of the first n-type layer 4A is defined as the first region 4a. In addition, the area from the surface of the n-electrode 5 side of the first n-type layer 4A toward the p-type light absorbing layer 3 side to half the thickness of the first n-type layer 4A is defined as the second region 4b. It should be noted that, in the same manner as in the first embodiment, the analysis is performed at each distance from the surface of the n-type layer. Figure 2 Analysis points distributed at equal intervals and as close as possible to each other as shown in the analysis points of can be obtained by, for example, SIMS analysis.

[0065] The composition ratio of the elements corresponds to the relationship between the first region 4a and the second region 4b of the second embodiment and the relationship between the first n-type layer 4A and the second n-type layer 4B of the first embodiment. Therefore, the inclined composition change described in the first embodiment is also the same in the solar cell 101 of the second embodiment.

[0066] The solar cell 101 of the second embodiment is also excellent in the continuity of connection of the conduction band minimum values, similarly to the solar cell 100 of the first embodiment, and Jsc, Voc, and FF are improved, thereby contributing to the improvement of conversion efficiency.

[0067] (Third embodiment)

[0068] The third embodiment relates to a solar cell. Figure 4 2 shows a schematic cross-sectional view of a solar cell 102 of the third embodiment. The solar cell 102 of the third embodiment has an n-type layer 4 formed by stacking three layers, namely, a first n-type layer 4A, a second n-type layer 4B, and a third n-type layer 4C, which is different from the solar cell 101 of the second embodiment. The common descriptions of the first to third embodiments are omitted.

[0069] The third n-type layer 4C is located between the second n-type layer 4B and the n-electrode 5. The surface of the third n-type layer 4C on the second n-type layer 4B side is in direct contact with the second n-type layer 4B. Preferably, the third n-type layer 4C is an oxide semiconductor layer containing Ga and / or Zn, and contains a compound based on Ga and / or Zn. The interface between the second n-type layer 4B and the third n-type layer 4C may be clear or unclear. The third n-type layer 4B may be a mixture of other oxides in an oxide based on Ga, may be doped with other elements in an oxide based on Ga and / or Zn, and may be a mixture of Ga and / or Zn-based oxides doped with other elements and other oxides. An intermediate layer not shown in the figure may be provided between the third n-type layer 4C and the n-electrode 5.

[0070] Preferably, the third n-type layer 4C is Ga z1 Zn z2 Sn z3 M4 z4 O z5 A layer having the compound represented as the main body (more than 50wt%), and M4 is one or more selected from the group consisting of Hf, Zr, In, Ti, Al, B, Mg, Si and Ge. z1, z2 and z4 are values ​​greater than 0. z3 is a value greater than 0. When the sum of z1, z2, z3 and z4 is set to 2, z5 is preferably greater than 2.2 and less than 3.6. The form of an oxide based on Ga or / and Zn mixed with other oxides, the form of an oxide based on Ga or / and Zn doped with other elements, and the form of an oxide based on Ga or / and Zn doped with other elements mixed with other oxides are all Ga z1 Zn z2 Sn z3 M4 z4 O z5 express.

[0071] Preferably, 90 wt% or more of the third n-type layer 4C is Ga z1 Zn z2 Sn z3 M4 z4 O z5 More preferably, 95 wt% or more of the third n-type layer 4C is Ga z1 Zn z2 Sn z3 M4 z4 O z5 More preferably, 98 wt% or more of the third n-type layer 4C is Ga z1 Zn z2 Sn z3 M4 z4 Oz5 More preferably, the third n-type layer 4C is composed of Ga z1 Zn z2 Sn z3 M4 z4 O z5 The compound composition represented.

[0072] The third n-type layer 4C is mainly adjusted by Ga, Zn and Sn in such a way that the difference between the conduction band minimum value and the second n-type layer 4B and the n-electrode 5 becomes small. Since the conductor bottom end of ZnO and SnO2 is lower than the conduction band minimum value of Ga2O3, the third n-type layer 4C can reduce the difference between the conduction band minimum value and the n-electrode 5 compared with Ga2O3. By increasing the element ratio of Zn to Sn compared with the element ratio of Zn to Sn in the first n-type layer 4A and the second n-type layer 4B, the conduction band minimum value of the third n-type layer 4C is reduced compared with the first n-type layer 4A. In addition, the continuity of the connection of the conduction band minimum value between the first n-type layer 4A and the n-electrode 5 is improved. In the third n-type layer 4C, (z1+z2) / (z1+z2+z3+z4) is preferably greater than 0.60 and less than 0.98. From this viewpoint, in the third n-type layer 4C, (z1+z2) / (z1+z2+z3+z4) is preferably 0.65 to 0.95, and more preferably 0.70 to 0.90.

[0073] The third n-type layer 4C is located closest to the n-electrode 5 in the n-type layer, and preferably the third n-type layer 4C is in direct contact with the n-electrode 5. When the first n-type layer 4A and the second n-type layer 4B contain Zn or Sn, their composition ratio is preferably lower than the concentration of each of Zn and Sn in the third n-type layer 4C.

[0074] In addition, the third n-type layer 4C preferably contains Sn. If Sn is contained in the third n-type layer 4C, the continuity of the connection of the conduction band minimum is preferably improved, and the carrier concentration is increased. Therefore, z3 / (z1+z2+z3+z4) is preferably 0.10 or more and 0.50 or less, and more preferably 0.15 or more and 0.30 or less.

[0075] The element of M4 may be included in the third n-type layer 4C or may not be included. In the case where the element of M4 is included, its composition ratio is preferably low. Therefore, z4 / (z1+z2+z3+z4) is preferably greater than 0.00 and less than 0.05. The element of M4 is preferably common to the element included in the second n-type layer 4B or the n-electrode 5.

[0076] In the third n-type layer 4C, the elements of Ga, Zn, Sn, and M4 may also change in an inclined, step-like, or a combination of an inclined change and a step-like from the p-type light absorbing layer 3 side toward the n-electrode 5. For example, it is preferred that Sn is more on the n-electrode 5 side, and Ga and Zn are more on the second n-type layer 4B side.

[0077] The sum of the thickness of the first n-type layer 4A, the thickness of the second n-type layer 4B, and the thickness of the third n-type layer 4C is typically greater than 3 nm and less than 100 nm. If the sum of the thickness of the first n-type layer 4A, the thickness of the second n-type layer 4B, and the thickness of the third n-type layer 4C is less than 3 nm, leakage current is generated when the effective area of ​​the first n-type layer 4A, the second n-type layer 4B, and the third n-type layer 4C is poor, and sometimes the characteristics are reduced. The effective area is not limited to the above-mentioned film thickness. If the sum of the thickness of the first n-type layer 4A, the thickness of the second n-type layer 4B, and the thickness of the third n-type layer 4C exceeds 50 nm, sometimes the characteristics are reduced due to excessive high resistance of the n-type layer from the first n-type layer 4A to the third n-type layer 4C, or the short-circuit current is reduced due to reduced transmittance. Therefore, the sum of the thickness of the first n-type layer 4A, the thickness of the second n-type layer 4B, and the thickness of the third n-type layer 4C is more preferably 3 nm to 30 nm, and even more preferably 5 nm to 30 nm.

[0078] By using the third n-type layer 4C, the continuity of the connection between the conduction band minimum of the n-type layer 4 and the n-electrode 5 is further improved. In addition, the solar cell 102 of the third embodiment also contributes to the improvement of conversion efficiency by improving Jsc, Voc and FF.

[0079] (Fourth embodiment)

[0080] The fourth embodiment relates to a solar cell. Figure 5 , a schematic cross-sectional view of a solar cell 103 of the fourth embodiment is shown. The n-type layer 4 of the solar cell 103 of the fourth embodiment has a first region 4a, a second region 4b, and a third region 4c, which is different from the solar cell 102 of the third embodiment. The common descriptions of the first to third embodiments and the fourth embodiment are omitted. The third region 4c of the fourth embodiment is equivalent to the third n-type layer 4C of the third embodiment.

[0081] The third region 4c is located on the n-electrode 5 side of the n-type layer 4. In addition, the second region 4b is located between the third region 4c and the first region 4a. In the first n-type layer 4A of the fifth embodiment, the composition is clearly different on the p-type light absorbing layer 3 side and the n-electrode 5 side, but the interface between the first region 4a and the second region 4b and the interface between the second region 4b and the third region 4c are not confirmed. When the thickness of the first n-type layer 4A is set to d, the first region 4a is set from the surface of the first n-type layer 4A on the p-type light absorbing layer 3 side to the n-electrode 5 side to 0.33d. In addition, the third region 4c is set from the surface of the first n-type layer 4A on the n-electrode 5 side to the p-type light absorbing layer 3 side to 0.33d. The second region 4b is set between the first region 4a and the third region 4c.

[0082] The composition of the compound in the first region 4a is the average composition of the entire first region 4a unless any special conditions are added. When the thickness of the first n-type layer 4A is set to d, the composition of the first region 4a is the average value of the compositions at depths of 0.10d, 0.20d, and 0.30d from the surface of the first n-type layer 4A on the side of the p-type light absorbing layer 3. When the thickness of the first n-type layer 4A is very thin (less than 10nm), the composition at a depth of 0.20d from the surface of the first n-type layer 4A is regarded as the average composition of the entire first region 4a. When the thickness of the first n-type layer 4A is set to d, the composition of the second region 4b is the average value of the compositions at depths of 0.40d, 0.50d, and 0.60d from the surface of the first n-type layer 4A on the side of the p-type light absorbing layer 3. When the thickness of the first n-type layer 4A is very thin (less than 10 nm), the composition at a depth of 0.50 d from the surface of the first n-type layer 4A is regarded as the average composition of the entire second region 4b. When the thickness of the first n-type layer 4A is set to d, the composition of the third region 4c is the average value of the compositions at depths of 0.70 d, 0.80 d, and 0.90 d from the surface of the first n-type layer 4A on the side of the p-type light absorbing layer 3. When the thickness of the first n-type layer 4A is very thin (less than 10 nm), the composition at a depth of 0.80 d from the surface of the first n-type layer 4A is regarded as the average composition of the entire third region 4c.

[0083] The compositions of the first region 4a, the second region 4b, and the third region 4c correspond to the first n-type layer 4A, the second n-type layer 4B, and the third n-type layer 4C of the third embodiment, respectively. For the solar cell 103 of the fourth embodiment, the inclined composition changes described in the first to third embodiments are also included in the solar cells 100, 101, and 102 of the first to third embodiments.

[0084] The solar cell 103 of the fourth embodiment is also excellent in the continuity of connection of the conduction band minimum values, similarly to the solar cell 102 of the third embodiment, and Jsc, Voc, and FF are improved, thereby contributing to the improvement of conversion efficiency.

[0085] (Fifth embodiment)

[0086] The fifth embodiment relates to a multi-junction solar cell. Figure 6 Schematic cross-sectional view of a multi-junction solar cell according to a fifth embodiment is shown in FIG. Figure 6 The multi-junction solar cell 200 has the solar cell (first solar cell) 100 of the first embodiment and the second solar cell 201 on the light incident side. The band gap of the light absorption layer of the second solar cell 201 is smaller than the band gap of the p-type light absorption layer 3 of the solar cell 100 of the first embodiment. It should be noted that the multi-junction solar cell of the embodiment also includes a solar cell obtained by connecting more than three solar cells. It should be noted that in the fifth embodiment, the solar cells 101-103 of the second to fourth embodiments can also be used instead of the solar cell 100 of the first embodiment.

[0087] Since the band gap of the p-type light absorbing layer 3 of the first solar cell 100 of the first embodiment is about 2.0 eV-2.2 eV, the band gap of the light absorbing layer of the second solar cell 200 is preferably 1.0 eV or more and 1.6 eV or less. As the light absorbing layer of the second solar cell, it is preferably one selected from the group consisting of one or more compound semiconductor layers selected from the group consisting of CIGS system, CuZnSnSSe system and CdTe system with a high In content ratio, crystalline silicon and a perovskite compound.

[0088] (Sixth Implementation Method)

[0089] The sixth embodiment relates to a solar cell module. Figure 7 2 is a perspective view of a solar cell module 300 according to a fifth embodiment. Figure 7 The solar cell module 300 is a solar cell module obtained by stacking a first solar cell module 301 and a second solar cell module 302. The first solar cell module 301 is a light incident side, and the solar cell 100 of the first embodiment is used. For the second solar cell module 302, it is preferable to use the second solar cell 201. For the first solar cell module 301, the solar cells 101-103 of the second to fourth embodiments can also be used.

[0090] Figure 8 A cross-sectional view of the solar cell module 300 is shown in FIG. Figure 8, the structure of the first solar cell module 301 is shown in detail, and the structure of the second solar cell module 302 is not shown. In the second solar cell module 301, the structure of the solar cell module is appropriately selected according to the light absorption layer of the solar cell used, etc. Figure 8 The solar cell module includes a plurality of submodules 303 surrounded by dotted lines, wherein the submodules 303 are formed by arranging a plurality of solar cells 100 (solar cell units) in a horizontal direction and electrically connected in series via wiring 304. The plurality of submodules 303 are electrically connected in parallel or in series. Adjacent submodules 303 are electrically connected via bus bars 305.

[0091] For the adjacent solar cells 100, the n-electrode 5 on the upper side and the p-electrode 2 on the lower side are connected by wiring 304. The solar cell 100 of the sixth embodiment also has a substrate 1, a p-electrode 2, a p-type light absorbing layer 3, an n-type layer 4, and an n-electrode 5, similarly to the solar cell 100 of the first embodiment. Both ends of the solar cell 100 in the submodule 303 are connected to a bus bar 305, and the bus bar 305 electrically connects the plurality of submodules 303 in parallel or in series, preferably in a manner to adjust the output voltage with the second solar cell module 302. It should be noted that the connection form of the solar cell 100 shown in the sixth embodiment is an example, and a solar cell module can also be constructed by other connection forms.

[0092] (Seventh Implementation Method)

[0093] The seventh embodiment relates to a solar power generation system. The solar cell module of the sixth embodiment can be used as a generator for generating electricity in the solar power generation system of the seventh embodiment. The solar power generation system of the embodiment is a system for generating electricity using a solar cell module, specifically, having a solar cell module for generating electricity, a mechanism for converting the generated electricity into electric power, and a storage mechanism for storing the generated electricity or a load for consuming the generated electricity. Fig. 9 2 is a diagram showing a configuration of a solar power generation system 400 according to an embodiment. Fig. 9 The solar power generation system includes a solar cell module 401 (300), a converter 402, a battery 403, and a load 404. Either the battery 403 or the load 404 may be omitted. The load 404 may also be set to a configuration that can also utilize the electric energy stored in the battery 403. The converter 402 is a device including a circuit or element for performing power conversion such as voltage transformation or direct current to alternating current conversion, such as a DC-DC converter, a DC-AC converter, an AC-AC converter, etc. The configuration of the converter 402 may be a preferred configuration according to the generated voltage, the configuration of the battery 403, or the configuration of the load 404.

[0094] The solar cell unit included in the submodule 301 included in the solar cell module 300 generates electricity after receiving light, and the electric energy is converted by the converter 402 and stored in the storage battery 403 or consumed by the load 404. In the solar cell module 401, it is preferable to provide a sunlight tracking drive device for always directing the solar cell module 401 toward the sun, or to provide a concentrator for concentrating sunlight, or to add a device for improving the power generation efficiency.

[0095] The solar power generation system 400 is preferably used in real estate such as houses, commercial facilities, or factories, or in movables such as vehicles, aircraft, or electronic equipment. By using the solar cell having excellent conversion efficiency of the embodiment in a solar cell module, an increase in the amount of power generated can be expected.

[0096] A vehicle is shown as an example of utilization of the solar power generation system 400 . Fig.10 A schematic diagram of the structure of a vehicle 500 is shown in FIG. Fig.10 The vehicle 500 includes a vehicle body 501, a solar cell module 502, a power conversion device 503, a battery 504, a motor 505, and a tire (wheel) 506. The electricity generated by the solar cell module 501 disposed on the upper part of the vehicle body 501 is converted by the power conversion device 503, and the battery 504 is charged, or the electricity is consumed by a load such as the motor 505. The vehicle 500 can be driven by rotating the tire (wheel) 506 using the electricity supplied by the solar cell module 502 or the battery 504 through the motor 505. The solar cell module 502 may not be a multi-junction type, but may be composed of only the first solar cell module including the solar cell 100 of the first embodiment. When the solar cell module 502 having transmittance is used, it is preferable to use the solar cell module 502 as a window for power generation on the side of the vehicle body 501 in addition to the upper part of the vehicle body 501.

[0097] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[0098] (Example 1)

[0099] On the glass substrate, ITO (In: Sn = 90: 10, film thickness 20nm) and ATO (Sn: Sb = 98: 2, film thickness 150μm) were deposited on the upper surface of the side in contact with the glass as the p-electrode on the back side. A Cu2O light absorption layer was formed by sputtering at 500°C in an oxygen and argon atmosphere. Then, a 10nm-thick GaN with no composition tilt was deposited as the first n-type layer by ALD. 1.70 Al 0.30 O 3.00As the second n-type layer, 10 nm of Ga with no composition tilt is deposited 1.90 Al 0.10 O 3.00 , as the n-electrode on the surface side, an AZO transparent conductive film is deposited. Then, as an anti-reflection film, a MgF2 film is formed, thereby obtaining a solar cell. For the obtained solar cell, the short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), conversion efficiency and light transmittance are evaluated. It should be noted that the oxygen composition ratio of the n-type layer is obtained by the type and composition ratio of the metal of the metal oxide.

[0100] Evaluation of the light transmittance of solar cells: The light transmittance of solar cells is the average transmittance at a wavelength of 700-1200 nm measured by a spectrophotometer.

[0101] (Examples 2-26, Comparative Examples)

[0102] exist Fig.11 The table of embodiments shows the conditions of the n-type layer of the embodiments and comparative examples. Except for the conditions of the n-type layer (the first n-type layer (the first region), the second n-type layer (the second region), the conditions of the n-type layer are the same as those of Example 1. In the embodiment, when two or three layers of n-type layers are formed, the thickness of each n-type layer (each region) is set to 6 nm. Examples 25 and 26 do not have an interface between the first n-type layer and the second n-type layer, and the n-type layer includes the first region and the second region. There is an interface between the second region and the third n-type layer of Example 26.

[0103] In Examples 17 to 26, the composition of the n-type layer was changed in the film thickness direction (the stacking direction of the p-type light absorbing layer and the n-type layer). Fig.12 The table of embodiments shows the composition changes of each embodiment. Fig.12 The table shows the elements whose composition changes and the pattern of their composition changes. Fig.13 and Fig.14 The graph showing the pattern of composition change is shown in FIG. Fig.13 and Fig.14 The horizontal axis represents the depth of the n-type layer from the p-type light absorbing layer side to the n-electrode side, and the vertical axis represents the composition ratio. When the composition changes, the composition of the element with the highest composition ratio in each layer or region changes. For example, if Al increases by 0.1, Ga decreases by 0.1.

[0104] In Example 17, the composition of Al in the first n-type layer changes in a composition change mode of A, the composition of Al in the second n-type layer changes in a composition change mode of A, and the composition of Sn changes in a composition change mode of J. The composition is obliquely changed so that the surface of the first n-type layer on the p-type light absorbing layer side becomes Ga:Al=1.40:0.50, and the surface of the first n-type layer on the second n-type layer side becomes Ga:Al=1.60:0.20. In addition, the composition is changed so that the surface of the second n-type layer on the first n-type layer side becomes Ga:Al:Sn=1.80:0.20:0.00, Sn is included from near the middle of the thickness of the second n-type layer, and the surface on the n-electrode side becomes Ga:Al:Sn=1.90:0.00:0.10.

[0105] In Example 18, the composition of Al in the first n-type layer changes in the composition change mode of B, and the composition of Al in the second n-type layer changes in the composition change mode of B. The composition is changed stepwise so that the surface of the first n-type layer on the p-type light absorbing layer side becomes Ga:Al=1.60:0.40, and the surface of the first n-type layer on the second n-type layer side becomes Ga:Al=1.80:0.20. The composition of Al in the first n-type layer becomes 0.40 (d0), 0.33 (d1) from the surface on the p-type light absorbing layer side, and 0.60 (d2) from the surface on the p-type light absorbing layer side. 0.25 )、0.27(d 0.50 )、0.20(d 0.75 The target ratio was adjusted so that Ga:Al:Sn=1.75:0.20:0.05 was obtained on the surface of the second n-type layer on the first n-type layer side, and Ga:Al:Sn=1.95:0.00:0.05 was obtained on the surface of the n-electrode side. The Al composition of the second n-type layer was 0.20 (d0), 0.13 (d1) and 0.20 (d2) from the surface of the first n-type layer side. 0.25 )、0.07(d 0.50 )、0.00(d 0.75 ), 0.00(d1) to adjust the target ratio.

[0106] In Example 19, the composition of Al in the first n-type layer was changed in the composition change mode of C, and the composition of Al in the second n-type layer was changed in the composition change mode of C. The composition was changed so that the surface of the first n-type layer on the p-type light absorption layer side became Ga:Al=1.60:0.40, and the surface of the first n-type layer on the second n-type layer side became Ga:Al=1.70:0.30. In addition, the composition was changed so that the surface of the second n-type layer on the first n-type layer side became Ga:Al:Sn=1.80:0.15:0.05, and the surface on the n-electrode side became Ga:Al:Sn=1.90:0.05:0.05.

[0107] In Example 20, the composition of Al in the first n-type layer was changed in a composition change mode of D, and the composition of Al in the second n-type layer was changed in a composition change mode of D. The composition was changed so that the surface of the first n-type layer on the p-type light absorbing layer side was Ga:Al=1.50:0.50, the middle of the first n-type layer in the thickness direction was Ga:Al=1.70:0.30, and the surface of the first n-type layer on the second n-type layer side was Ga:Al=1.65:0.35. In addition, the composition was changed so that the surface of the second n-type layer on the first n-type layer side was Ga:Al:Sn=1.75:0.20:0.05, the middle of the second n-type layer in the thickness direction was Ga:Al:Sn=1.90:0.05:0.05, and the surface on the n-electrode side was Ga:Al:Sn=1.85:0.10:0.05.

[0108] In Example 21, the composition of Al in the first n-type layer was changed in the composition change mode of F, and the composition of Al in the second n-type layer was changed in the composition change mode of F. The composition was changed so that the surface of the first n-type layer on the p-type light absorbing layer side became Ga:Al=1.60:0.40, and from the middle of the first n-type layer in the thickness direction to the surface of the second n-type layer side became Ga:Al=1.80:0.20. In addition, the composition was changed so that the surface of the second n-type layer on the first n-type layer side became Ga:Al:Sn=1.80:0.15:0.05, and from the middle of the second n-type layer in the thickness direction to the surface of the n-electrode side became Ga:Al:Sn=1.87:0.08:0.05.

[0109] In Example 22, the composition of Al in the first n-type layer changes in the composition change mode of A, and the composition of Al in the second n-type layer changes in the composition change mode of A. The composition changes obliquely in such a way that the surface of the first n-type layer on the p-type light absorption layer side becomes Ga:Al=1.45:0.55, and the surface of the first n-type layer on the second n-type layer side becomes Ga:Al=1.55:0.45. In addition, the composition changes in such a way that the surface of the second n-type layer on the first n-type layer side becomes Ga:Al:Sn=1.80:0.15:0.05, and the surface on the n-electrode side becomes Ga:Al:Sn=1.90:0.05:0.05.

[0110] In Example 23, in the first n-type layer, Al changes in composition in the composition change mode of A, Hf changes in the composition change mode of C, Sn changes in the composition change mode of I, and in the second n-type layer, Al changes in composition in the composition change mode of A, and Sn changes in composition in the composition change mode of G. The composition is changed so that the surface of the first n-type layer on the p-type light absorption layer side becomes Ga:Al:Hf:Sn=1.548:0.40:0.05:0.002, and the surface of the first n-type layer on the second n-type layer side becomes Ga:Al:Hf:Sn=1.755:0.20:0.03:0.015. In addition, the composition is changed so that the surface of the second n-type layer on the first n-type layer side becomes Ga:Al:Sn=1.83:0.15:0.02, and the surface on the n-electrode side becomes Ga:Al:Sn=1.87:0.05:0.08.

[0111] In Example 24, in the first n-type layer, Al changes in composition in a composition change mode of A, Hf changes in composition in a composition change mode of E, Sn changes in composition in a composition change mode of J, and in the second n-type layer, Al changes in composition in a composition change mode of A, and Sn changes in composition in a composition change mode of H. Furthermore, Sn in the third n-type layer changes in composition in a composition change mode of H. The composition is changed so that the surface of the first n-type layer on the p-type light absorbing layer side becomes Ga:Al:Hf:Sn=1.52:0.40:0.08:0.00, the vicinity of the center in the thickness direction of the first n-type layer becomes Ga:Al:Hf:Sn=1.70:0.30:0.00:0.00, and the surface of the first n-type layer on the second n-type layer side becomes Ga:Al:Hf:Sn=1.78:0.20:0.00:0.02. Furthermore, the composition was changed so that the surface of the second n-type layer on the first n-type layer side became Ga:Al:Sn=1.83:0.15:0.02, and the surface of the third n-type layer side became Ga:Al:Sn=1.87:0.05:0.08. Furthermore, the composition was changed in a stepwise manner so that the surface of the third n-type layer on the first n-type layer side became Zn:Sn=1.85:0.15, and the surface of the n-electrode side became Zn:Sn=1.55:0.45.

[0112] In Example 25 and Example 26, the composition of Al in the first region and the second region was changed in the composition change pattern of A. The composition was changed so that the surface of the n-type layer on the p-type light absorbing layer side became Ga:Al=1.40:0.60, the position at a depth of 3nm from the surface of the n-type layer on the p-type light absorbing layer side on the n-electrode side became Ga:Al=1.60:0.40, the position at a depth of 6nm from the surface of the n-type layer on the p-type light absorbing layer side on the n-electrode side (the boundary between the first region and the second region) became Ga:Al=1.80:0.20, the position at a depth of 9nm from the surface of the n-type layer on the p-type light absorbing layer side on the n-electrode side became Ga:Al=1.90:0.10, and the position at a depth of 12nm from the surface of the n-type layer on the p-type light absorbing layer side on the n-electrode side (the interface between the second region and the n-electrode or the third n-type layer) became Ga:Al=2.00:0.00.

[0113] A solar simulator simulating an AM1.5G light source is used, and the Si unit that serves as a reference under this light source is used to adjust the light intensity in a manner to obtain 1 sun. The measurement is performed under atmospheric pressure, and the temperature in the measurement room is set to 25°C. The voltage is scanned, and the current density (the value obtained by dividing the current by the unit area) is measured. When the horizontal axis is set to voltage and the vertical axis is set to current density, the point intersecting with the horizontal axis becomes the open circuit voltage Voc, and the point intersecting with the vertical axis becomes the short circuit current density Jsc. On the measurement curve, the voltage is multiplied by the current density. If the points that will become the maximum are set as Vmpp and Jmpp (maximum power point), respectively, then FF = (Vmpp*Jmpp) / (Voc*Jsc), and the conversion efficiency Eff. is calculated by Eff. = Voc*Jsc*FF.

[0114] exist Fig.15 The table about the examples summarizes the short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), conversion efficiency and light transmittance of the examples and comparative examples.

[0115] Regarding light transmittance, the case where the transmittance of light in the wavelength band above 700nm and below 1200nm is 75% or more is evaluated as A, the case where the transmittance of light in the wavelength band above 700nm and below 1200nm is 70% or more and less than 75% is evaluated as B, and the case where the transmittance of light in the wavelength band above 700nm and below 1200nm is less than 70% is evaluated as C.

[0116] Regarding Jsc, the case where the conversion efficiency was 1.1 times or more relative to Comparative Example 1 was evaluated as A, the case where Jsc was 1.0 times or more and less than 1.1 times relative to Comparative Example 1 was evaluated as B, and the case where Jsc was less than 1.0 times relative to Comparative Example 1 was evaluated as C.

[0117] Regarding Voc, the case where the conversion efficiency was 1.3 times or more relative to Comparative Example 1 was evaluated as A, the case where the Voc was 1.1 times or more and less than 1.3 times relative to Comparative Example 1 was evaluated as B, and the case where the Voc was less than 1.1 times relative to Comparative Example 1 was evaluated as C.

[0118] Regarding FF, the case where the conversion efficiency was 1.1 times or more relative to Comparative Example 1 was evaluated as A, the case where the FF was 1.0 times or more and less than 1.1 times relative to Comparative Example 1 was evaluated as B, and the case where the FF was less than 1.0 times relative to Comparative Example 1 was evaluated as C.

[0119] Regarding the conversion efficiency, the case where the conversion efficiency was 1.5 times or more relative to that of Comparative Example 1 was evaluated as A, the case where the conversion efficiency was 1.1 times or more and less than 1.5 times relative to that of Comparative Example 1 was evaluated as B, and the case where the conversion efficiency was less than 1.1 times relative to that of Comparative Example 1 was evaluated as C.

[0120] As Fig.15 As can be seen from the table, in order to smoothly connect the conduction band of the p-type light absorbing layer with the n-electrode in terms of energy, a multilayer structure or a tilted structure with intentionally controlled composition is applied to the n-type layer, and Jsc, Voc, and FF are improved respectively, and the efficiency is greatly improved compared with the comparative example. From the above results, it can be understood that controlling and optimizing the energy structure of the conduction band in the thickness direction of the n-layer is an important technology for improving the characteristics of Cu2O solar cells.

[0121] Some elements in the specification are indicated by element symbols only.

[0122] The above embodiments of the present invention have been described, but the present invention is not limited to the above embodiments as they are, and the constituent elements can be deformed and concretized in the implementation stage without departing from the scope of the main purpose. In addition, various inventions can be formed by suitable combinations of multiple constituent elements disclosed in the above embodiments. For example, constituent elements in different embodiments can also be appropriately combined as in the modified examples.

[0123] Explanation of symbols

[0124] 100, 101: Solar cell (first solar cell), 1: Substrate, 2: P-electrode (first P-electrode 2a, second P-electrode 2b), 3: P-type light absorbing layer, 4: N-type layer, 5: N-electrode

[0125] 200: Multi-junction solar cell, 201: Second solar cell,

[0126] 300: Solar cell module, 6: Substrate, 301: First solar cell module, 302: Second solar cell module, 303: Submodule, 304: Bus bar,

[0127] 400: Solar power generation system, 401: Solar cell module, 402: Converter, 403: Battery, 404: Load

[0128] 500: vehicle, 501: vehicle body, 502: solar cell module, 503: power conversion device, 504: battery, 505: motor, 506: tire (wheel).

Claims

1. A solar cell, comprising: p electrode; n electrode; A p-type light absorbing layer, which is located between the p-electrode and the n-electrode and mainly contains cuprous oxide; and The n-type layer includes a first n-type layer and a second n-type layer, or includes a first n region and a second n region, wherein the first n-type layer is located between the p-type light absorbing layer and the n-electrode and is Ga x1 M1 x2 M2 x3 M3 x4 O x5 The layer is mainly composed of the compound represented by, wherein M1 is Al and / or B, M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, M3 is one or more selected from the group consisting of Sn, Si and Ge, x1 and x5 are values ​​greater than 0, x2, x3 and x4 are values ​​greater than 0, and when the sum of x1, x2, x3 and x4 is set to 2, x5 is greater than 3.0 and less than 3.8; the second n-type layer is located between the first n-type layer and the n-electrode and is composed of Ga y1 M1 y2 M2 y3 M3 y4 O y5 The compound represented by is used as the main layer, y1 and y5 are values ​​greater than 0, y2, y3 and y4 are values ​​greater than 0, and when the sum of y1, y2, y3 and y4 is set to 2, y5 is greater than 3.0 and less than 3.8; the first n region is located between the p-type light absorbing layer and the n-electrode, and Ga x1 M1 x2 M2 x3 M3 x4 O x5 The compound represented by is used as the main body, the M1 is Al and / or B, the M2 is one or more selected from the group consisting of In, Ti, Zn, Hf and Zr, the M3 is one or more selected from the group consisting of Sn, Si and Ge, the x1 and x5 are values ​​greater than 0, the x2, x3 and x4 are values ​​greater than 0, and when the sum of the x1, x2, x3 and x4 is set to 2, the x5 is greater than 3.0 and less than 3.8; the second n region is located between the first n region and the n electrode, and Ga y1 M1 y2 M2 y3 M3 y4 O y5 The compound represented by is mainly composed of: y1 and y5 are values ​​greater than 0; y2, y3 and y4 are values ​​greater than 0; and when the sum of y1, y2, y3 and y4 is set to 2, y5 is greater than or equal to 3.0 and less than or equal to 3.8; (x2+x3) is greater than (y2+y3).

2. The solar cell according to claim 1, wherein: (x1+x2) / (x1+x2+x3+x4) is greater than or equal to 0.50 and less than or equal to 1.00, x2 / (x1+x2) is greater than or equal to 0.00 and less than or equal to 0.50, x3 / (x1+x2+x3+x4) is greater than or equal to 0.00 and less than or equal to 0.50, x4 / (x1+x2+x3+x4) is greater than or equal to 0.00 and less than or equal to 0.

15.

3. The solar cell according to claim 1 or 2, wherein: (x1+x2) / (x1+x2+x3+x4) is greater than or equal to 0.80 and less than or equal to 1.00, x2 / (x1+x2) is greater than or equal to 0.00 and less than or equal to 0.40, x3 / (x1+x2+x3+x4) is greater than or equal to 0.00 and less than or equal to 0.10, x4 / (x1+x2+x3+x4) is greater than or equal to 0.00 and less than or equal to 0.

10.

4. The solar cell according to any one of claims 1 to 3, wherein (y1+y2) / (y1+y2+y3+y4) is 0.65 or more and 1.00 or less, y2 / (y1+y2) is greater than or equal to 0.00 and less than or equal to 0.30, The y2 is less than 90% of x2, y3 / (y1+y2+y3+y4) is greater than or equal to 0.00 and less than or equal to 0.10, y4 / (y1+y2+y3+y4) is greater than or equal to 0.00 and less than or equal to 0.

15.

5. The solar cell according to any one of claims 1 to 4, wherein (y1+y2) / (y1+y2+y3+y4+y5) is 0.80 or more and 1.00 or less, y2 / (y1+y2) is greater than or equal to 0.00 and less than or equal to 0.20, The y2 is less than 80% of x2, y3 / (y1+y2+y3+y4) is greater than or equal to 0.00 and less than or equal to 0.05, y4 / (y1+y2+y3+y4) is greater than or equal to 0.01 and less than or equal to 0.

15.

6. The solar cell according to any one of claims 1 to 5, wherein The n-type layer further has a third n-type layer or further has a third region, wherein the third n-type layer is located between the second n-type layer and the n-electrode and is Ga z1 Zn z2 Sn z3 M4 z4 O z5 The layer is mainly composed of the compound represented by, M4 is one or more selected from the group consisting of Hf, Zr, In, Ti, Al, B, Mg, Si and Ge, z1, z2 and z4 are values ​​greater than 0, z3 is a value greater than 0, and when the sum of z1, z2, z3 and z4 is set to 2, z5 is greater than 2.2 and less than 3.6; the third region is located between the second n region and the n electrode and is Ga z1 Zn z2 Sn z3 M4 z4 O z5 The layer has the compound represented as the main body, M4 is one or more selected from the group consisting of Hf, Zr, In, Ti, Al, B, Mg, Si and Ge, z1, z2 and z4 are values ​​greater than 0, z3 is a value greater than 0, and when the sum of z1, z2, z3 and z4 is set to 2, z5 is greater than 2.2 and less than 3.

6.

7. The solar cell according to any one of claims 1 to 6, wherein (z1+z2) / (z1+z2+z3+z4) is 0.60 or more and 0.98 or less, z3 / (z1+z2+z3+z4) is 0.10 or more and 0.50 or less, z4 / (z1+z2+z3+z4) is greater than or equal to 0.00 and less than or equal to 0.

05.

8. The solar cell according to any one of claims 1 to 7, wherein (z1+z2) / (z1+z2+z3+z4) is 0.65 or more and 0.95 or less, z3 / (z1+z2+z3+z4) is greater than or equal to 0.15 and less than or equal to 0.

30.

9. The solar cell according to any one of claims 1 to 8, wherein When the thickness of the first n-type layer is set to d 4A In the case of From the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side to 0.25 d 4A The area d from the position A0-0.25 The element ratio of M1 in the formula is 1.10 to 2.50 times that of x2, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.25 d 4A The position toward the second n-type layer side is 0.50d 4A The area d from the position A0.25-0.50 The element ratio of M1 in the formula is greater than or equal to 0.75 times and less than or equal to 1.50 times that of x2, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.50 d. 4A The position toward the second n-type layer side is 0.75d 4A The area d from the position A0.50-0.75 The element ratio of M1 in the formula is 0.30 to 1.50 times that of x2, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.75d 4A The position to the side toward the second n-type layer is 1.00d 4A The area d from the position A0.75-1 The element ratio of M1 is greater than or equal to 0.10 times and less than or equal to 0.90 times that of x2.

10. The solar cell according to claim 9, wherein: The area d A0-0.25 The element ratio of the M1 in the region d A0.25-0.50 The element ratio of the M1 is above, The area d A0.25-0.50 The element ratio of the M1 in the region d A0.50-0.75 The element ratio of the M1 is above, The area d A0.50-0.75 The element ratio of the M1 in the region d A0.75-1 The element ratio of the M1 is above, The area d A0.75-1.0 The element ratio of the M1 in the region d A0-0.25 The element ratio of M1 is less than half.

11. The solar cell according to any one of claims 1 to 10, wherein When the thickness of the first n-type layer is set to d 4A In the case of From the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side to 0.25 d 4A The area d from the position A0-0.25 The Ga ratio in is 0.75 times or more and 0.98 times or less of x1, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.25 d 4A The position toward the second n-type layer side is 0.50d 4A The area d from the position A0.25-0.50 The element ratio of Ga in is 0.80 times or more and 1.10 times or less of x1, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.50 d. 4A The position toward the second n-type layer side is 0.75d 4A The area d from the position A0.50-0.75 The element ratio of Ga in is 0.90 times or more and 1.20 times or less of x1, The distance from the surface of the first n-type layer on the p-type light absorbing layer side toward the second n-type layer side is 0.75d 4A The position to the side toward the second n-type layer is 1.00d 4A The area d from the position A0.75-1 The element ratio of Ga in is greater than 1.02 times and less than 1.25 times that of x1.

12. The solar cell according to any one of claims 9 to 11, wherein The area d A0-0.25 The element ratio of Ga in the region d A0.25-0.50 The Ga element ratio in is below, The area d A0.25-0.50 The element ratio of Ga in the region d A0.50-0.75 The Ga element ratio in is below, The area d A0.50-0.75 The element ratio of Ga in the region d A0.75-1 The element ratio of Ga in is less than .

13. The solar cell according to any one of claims 1 to 12, wherein When the thickness of the second n-type layer is set to d 4B In the case of From the surface of the second n-type layer on the first n-type layer side toward the n-electrode side to 0.25d 4B The area d from the position B0-0.25 The element ratio of M1 in y2 is 1.10 times or more and 4.00 times or less, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.25 d 4B The position to the n-electrode side is 0.50d 4B The area d from the position B0.25-0.50 The element ratio of M1 in y2 is 0.00 times or more and 1.50 times or less, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.50 d 4B The position to the n-electrode side is 0.75d 4B The area d from the position B0.50-0.75 The element ratio of M1 in y2 is greater than or equal to 0.00 times and less than or equal to 1.25 times, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.75 d 4B The position to the n-electrode side is 1.00d 4B The area d from the position B0.75-1 The element ratio of M1 in y2 is greater than or equal to 0.00 times and less than or equal to 0.90 times that of y2.

14. The solar cell according to claim 13, wherein: The area d B0-0.25 The element ratio of the M1 in the region d B0.25-0.50 The element ratio of the M1 is above, The area d B0.25-0.50 The element ratio of the M1 in the region d B0.50-0.75 The element ratio of the M1 is above, The area d B0.50-0.75 The element ratio of the M1 in the region d B0.75-1 The element ratio of the M1 is above, The area d B0.75-1.00 The element ratio of the M1 in the region d B0-0.25 The element ratio of M1 is less than half.

15. The solar cell according to any one of claims 1 to 14, wherein When the thickness of the second n-type layer is set to d 4B In the case of From the surface of the second n-type layer on the first n-type layer side toward the n-electrode side to 0.25d 4B The area d from the position B0-0.25 The element ratio of M3 in y4 is 0.00 times or more and 0.75 times or less, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.25 d 4B The position to the n-electrode side is 0.50d 4B The area d from the position B0.25-0.50 The element ratio of M3 in y4 is 0.30 times or more and 1.50 times or less, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.50 d 4B The position to the n-electrode side is 0.75d 4B The area d from the position B0.50-0.75 The element ratio of M3 in y4 is 0.75 times or more and 2.00 times or less, The distance from the surface of the second n-type layer on the first n-type layer side toward the n-electrode side is 0.75 d 4B The position to the n-electrode side is 1.00d 4B The area d from the position B0.75-1 The element ratio of M3 is greater than or equal to 1.10 times and less than or equal to 3.00 times that of y4.

16. The solar cell according to claim 15, wherein: The area d B0-0.25 The element ratio of the M3 in the region d B0.25-0.50 The element ratio of the M3 is as follows, The area d B0.25-0.50 The element ratio of the M3 in the region d B0.50-0.75 The element ratio of the M3 is as follows, The area d B0.50-0.75 The element ratio of the M3 in the region d B0.75-1 The element ratio of the M3 is as follows, The area d B0-0.25 The element ratio of the M3 in the region d B0.75-1.00 The element ratio of M3 is less than half.

17. A multi-junction solar cell having: The solar cell according to any one of claims 1 to 16, and A solar cell having a light absorbing layer having a smaller band gap than the p-type light absorbing layer of the solar cell according to any one of claims 1 to 16.

18. A solar cell module using the solar cell according to any one of claims 1 to 16.

19. A solar power generation system, which performs solar power generation using the solar cell module according to claim 18.

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