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

Abstract

The purpose of the present disclosure is to provide a solar battery module, a solar battery cell, and a method for manufacturing a solar battery module, all of which are for suppressing an increase in electric resistance. The present disclosure relates to a solar battery module comprising: a first solar battery cell that has at least a conductive corrosion prevention layer, a first conductive substrate, a first power generation element layer, and a first electrode in the stated order; and a second solar battery cell that has at least a second conductive substrate, a second power generation element layer, and a second electrode in the stated order. The conductive corrosion prevention layer of the first solar battery cell and the second electrode of the second solar battery cell are joined via at least a conductive adhesive member.

Description

Solar cell module, solar cell cell, and method of manufacturing solar cell module

[0001] The present invention relates to a solar cell module, a solar cell, and a method for manufacturing a solar cell module.

[0002] To improve the voltage characteristics of a solar cell module, solar cells are electrically connected in series. In this case, methods for joining solar cells include soldering the back electrode of one solar cell to a metal ribbon, and the metal ribbon wire to the front electrode of the other solar cell. However, soldered joints have the problem of being vulnerable to mechanical vibration and thermal shock. Furthermore, in thin-film solar cells, the soldered joints tend to be thicker, resulting in unevenness on the surface of the thin-film solar cell.

[0003] Patent Document 1 discloses a method of bonding a solar cell and a bus bar using a conductive adhesive member.

[0004] Patent No. 3751539

[0005] If a solar cell module is fabricated by joining the back electrode of one solar cell to the front electrode of the other solar cell using a conductive adhesive material without using a metal ribbon wire, as in the method of Patent Document 1, problems associated with joining by soldering do not occur. Furthermore, the number of materials required for joining solar cells can be reduced, and the required process can be simplified, leading to cost reductions.

[0006] It is known that the performance of solar cells can be improved by heat treatment in an atmosphere such as a sulfur atmosphere. In the above-mentioned bonding method using a conductive adhesive member, the back electrode of one of the solar cells is exposed. Therefore, when this solar cell is heat treated in an atmosphere such as a sulfur atmosphere, the back electrode is denatured and its performance as an electrode deteriorates. As a result, it has been found that the electrical resistance increases in the bonding region between the solar cells, and the electrical resistance of the solar cell module increases.

[0007] An object of the present invention is to provide a solar cell module, a solar cell, and a method for manufacturing a solar cell module that suppress an increase in electrical resistance.

[0008] A solar cell module according to one embodiment of the present invention comprises a first solar cell having at least a conductive corrosion prevention layer, a first conductive substrate, a first power generation element layer, and a first electrode, in this order, and a second solar cell having at least a second conductive substrate, a second power generation element layer, and a second electrode, in this order, wherein the conductive corrosion prevention layer of the first solar cell and the second electrode of the second solar cell are joined together via at least a conductive adhesive member.

[0009] The inventors have discovered that in a solar cell module, the conductive corrosion prevention layer of the first solar cell and the second electrode of the second solar cell are joined via at least a conductive adhesive member, thereby preventing the electrical resistance in the joining region between the solar cells from becoming high in the solar cell module.

[0010] A solar cell according to one embodiment of the present invention comprises at least a conductive corrosion prevention layer, a conductive substrate, a power generation element layer, and an electrode, in this order.

[0011] The inventors have discovered that by providing a solar cell with at least a conductive corrosion prevention layer, a conductive substrate, a power generation element layer, and an electrode in this order, the electrical resistance of the solar cell can be prevented from increasing.

[0012] A method for manufacturing a solar cell according to one embodiment of the present invention includes: a laminate preparation step of preparing a laminate including at least a conductive corrosion prevention layer, a conductive substrate, and a precursor of a light absorbing layer, in this order; a heat treatment step of heat treating the laminate in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere; a power generation element layer formation step of forming a power generation element layer having the light absorbing layer formed by the heat treatment step; and an electrode formation step of forming an electrode on the power generation element layer.

[0013] The inventors have found that a method for manufacturing a solar cell can prevent the electrical resistance of the solar cell manufactured by the above manufacturing method from increasing by including a laminate preparation step of preparing a laminate having at least a conductive corrosion prevention layer, a conductive substrate, and a precursor of a light absorbing layer, in this order.

[0014] According to the present invention, it is possible to provide a solar cell module that prevents an increase in electrical resistance in the junction regions between solar cells, a solar cell that can prevent an increase in electrical resistance, and a method for manufacturing a solar cell.

[0015] 1 is a schematic cross-sectional view of a solar cell module according to one embodiment of the present invention.

[0016] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0017] 1 is a schematic cross-sectional view of a solar cell module according to one embodiment of the present invention. Solar cell module 1 of this embodiment includes a first solar cell 100A having at least a conductive corrosion prevention layer 107A, a first conductive substrate 101A, a first power generation element layer 109A, and a first electrode 110A, in this order, and a second solar cell 100B having at least a second conductive substrate 101B, a second power generation element layer 109B, and a second electrode 110B, in this order, and conductive corrosion prevention layer 107A of first solar cell 100A and second electrode 110B of second solar cell 100B are bonded together via at least a conductive adhesive member 200.

[0018] In this embodiment, when there is no need to distinguish between the first solar cell 100A and the second solar cell 100B, they are simply referred to as solar cell 100. Furthermore, when there is no need to distinguish between the first solar cell 100A and the second solar cell 100B, the reference numerals for each layer may not include the letter A or B. For example, when there is no need to distinguish between the first conductive substrate 101A and the second conductive substrate 101B, they are simply referred to as conductive substrate 101.

[0019] The solar cell module 1 has a plurality of solar cells 100. For example, as shown in FIG. 1 , the solar cell module 1 may have two solar cells 100 or three or more solar cells 100. Each solar cell 100 has at least a conductive substrate 101, a power generation element layer 109, and an electrode 110, in this order. Furthermore, of the plurality of solar cells 100 in the solar cell module 1, one or more solar cells 100 have at least a conductive corrosion prevention layer 107, a conductive substrate 101, a power generation element layer 109, and an electrode 110, in this order. In the solar cell module 1, the conductive corrosion prevention layer 107 of one solar cell 100 and the electrode 110 of another solar cell 100 are bonded together via at least a conductive adhesive member. In FIG. 1 , the solar cells 100 are bonded together by disposing a conductive adhesive member 200 on one grid of the grid electrode 106. However, the solar cells 100 may also be bonded together by disposing a conductive adhesive member 200 on a region of the grid electrode 106 that includes multiple grids. Furthermore, when the electrode 110 does not include the grid electrode 106 and only includes the electrode layer 105, a conductive adhesive member 200 may be placed on the electrode layer 105 to bond the solar battery cells 100 together.

[0020] The solar cell module 1 generates power by receiving light from the electrode 110 side. Therefore, from the viewpoint of power generation efficiency, it is preferable that the bonding area between the solar cell 100 be as small as possible within a range that ensures bonding strength.

[0021] The solar cell module 1 can be formed into a thin-film solar cell module or a thin-film flexible solar cell module by forming the solar cell 100 to be sufficiently thin.

[0022] Generally, in solar cells constituting a solar cell module, a precursor of a light absorbing layer is formed on a conductive substrate, followed by heat treatment in an atmosphere of selenium gas, sulfur gas, or the like to form a light absorbing layer. When fabricating the solar cell 100 constituting the solar cell module 1 of this embodiment, even if such heat treatment is performed, an increase in the electrical resistance of the conductive substrate 101 can be suppressed. As a result, an increase in the electrical resistance at the bonding regions between the solar cells 100 in the solar cell module 1 can be suppressed. The reason for this is not particularly limited, but is presumed to be as follows. For the first solar cell 100A, in the heat treatment of the stack including at least the conductive corrosion prevention layer 107A, the first conductive substrate 101A, and the precursor of the first light absorbing layer 103A in this order, the first conductive substrate 101A and the conductive corrosion prevention layer 107A on the second surface 1012A side of the first conductive substrate 101A are also subjected to the heat treatment together with the precursor of the first light absorbing layer 103A. Here, in the region of the second surface 1012A of the first conductive substrate 101A where the conductive corrosion prevention layer 107A is present, the second surface 1012A is not denatured, and an increase in the electrical resistance of the first conductive substrate 101A in this region is suppressed. Furthermore, the electrical resistance of the conductive corrosion prevention layer 107A is not likely to increase even when subjected to heat treatment. In the solar cell module 1, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B are bonded via at least the conductive adhesive member 200. In other words, because the region of the first solar cell 100A where the electrical resistance is not high is bonded to the second electrode 110B of the second solar cell 100B, it is believed that an increase in electrical resistance in the bonding region between the solar cells 100 in the solar cell module 1 can be suppressed.

[0023] The region on second surface 1012 of conductive substrate 101 where conductive corrosion-preventing layer 107 is present is the region on second surface 101b where conductive corrosion-preventing layer 107 is present in a direction perpendicular to second surface 1012. For example, if conductive corrosion-preventing layer 107 is provided on second surface 1012 of conductive substrate 101, the region on second surface 1012 that comes into contact with conductive corrosion-preventing layer 107 is the region on second surface 1012 of conductive substrate 101 where conductive corrosion-preventing layer 107 is present.

[0024] In addition, because the conductive corrosion-preventing layer 107 is conductive, the surface of the second solar cell 100B on which the second electrode 110B is present can be directly joined to the back surface of the first solar cell 100A on which the conductive corrosion-preventing layer 107A is present, thereby electrically connecting multiple solar cells 100 in series. That is, in the solar cell module 1 of this embodiment, the solar cells 100 can be easily electrically connected in series without the need for soldering conductors such as wires. Furthermore, the solar cell module 1 of this embodiment is less susceptible to cracks in the bonding regions between the solar cells 100 than solar cell modules fabricated by soldering, and therefore the solar cell module 1 of this embodiment is less likely to collapse structurally even when subjected to mechanical vibration or thermal shock.

[0025] Each component that can be included in the solar cell module 1 will be described in detail below.

[0026] In this embodiment, when a compound is expressed by its name, it includes not only the pure compound itself, but also the compound to which trace amounts of elements, etc. have been added, as long as the properties of the compound are not lost.

[0027] Also, in this embodiment, because elements in each layer of the solar cell module can exist in different oxidation states, all oxidation states are referred to by the name of the element unless otherwise clearly stated. For example, "elemental hydrogen" refers to hydrogen atoms, hydrogen ions, hydride ions, hydrogen in compounds, and hydrogen in elemental form.

[0028] 1.1. Solar Cell The solar cell module 1 of this embodiment is composed of a plurality of solar cells 100. Each solar cell 100 has at least a conductive substrate 101, a power generation element layer 109, and an electrode 110, in this order. Of the plurality of solar cells 100 in the solar cell module 1, one or more solar cells 100 have at least a conductive corrosion prevention layer 107, a conductive substrate 101, a power generation element layer 109, and an electrode 110, in this order. Intermediate layers may be provided between the layers as needed, from the standpoint of interlayer adhesion, bonding, conductivity, and the like.

[0029] The solar cell 100 may have, for example, a conductive substrate 101, a power generation element layer 109 provided on a first surface 1011 of the conductive substrate 101, an electrode 110 provided on the power generation element layer 109, and a conductive corrosion prevention layer 107 provided on a second surface 1012 of the conductive substrate 101.

[0030] The solar cell 100 may have, for example, a conductive substrate 101, a power generation element layer 109 provided on a first surface 1011 of the conductive substrate 101, an electrode 110 provided on the power generation element layer 109, a conductive corrosion prevention layer 107 provided on a second surface 1012 of the conductive substrate 101, and a contact resistance reducing layer 108 provided on the surface of the conductive corrosion prevention layer 107 opposite the conductive substrate 101.

[0031] The solar cell 100 may have, for example, a conductive substrate 101, a hole transport layer 102 provided on a first surface 1011 of the conductive substrate 101, a light absorbing layer 103 provided on the hole transport layer 102, an electron transport layer 104 provided on the light absorbing layer 103, an electrode 110 provided on the electron transport layer 104, a conductive corrosion prevention layer 107 provided on a second surface 1012 of the conductive substrate 101, and a contact resistance reducing layer 108 provided on the surface of the conductive corrosion prevention layer 107 opposite the conductive substrate 101.

[0032] 1.1.1. Conductive Substrate The solar cell 100 has a conductive substrate 101. The conductive substrate 101 is provided, for example, to extract current due to holes generated in the light absorption layer 103 described below. The conductive substrate 101 is not particularly limited as long as it is conductive. For example, a metal conductive layer made of a metal such as Ti or Al; a conductive inorganic compound conductive layer made of a conductive inorganic compound other than a metal; or a conductive organic compound conductive layer made of a conductive organic compound can be used. Among these, a metal conductive layer made of Ti is preferred from the viewpoints of suppressing impurity diffusion and suppressing mismatch in linear expansion coefficient. In the conductive substrate 101, one of the above-mentioned materials may be used alone, or two or more may be used in combination.

[0033] The thickness of the conductive substrate 101 is not particularly limited, but is, for example, 30 μm to 100 μm, or 30 μm to 60 μm. When the thickness of the conductive substrate 101 is within the above range, the solar cell tends to be lighter and more flexible while allowing sufficient current to be extracted without loss.

[0034] 1.1.2. Power Generation Element Layer The solar cell 100 has a power generation element layer 109. The power generation element layer 109 absorbs light to generate holes and electrons, thereby generating a current. The thickness of the power generation element layer 109 is not particularly limited, but is, for example, 1 μm to 4 μm.

[0035] 1.1.2.1. Hole Transport Layer The power generating element layer 109 may have a hole transport layer 102. The hole transport layer 102 can, for example, efficiently extract holes generated in the light absorbing layer 103 (described below) from the light absorbing layer 103 and suppress recombination of electrons and holes generated simultaneously with the holes in the light absorbing layer 103 (described below). The hole transport layer 102 is preferably a p-type semiconductor. The substance contained in the p-type semiconductor is not particularly limited, but examples thereof include inorganic compounds such as nickel oxide, molybdenum oxide, copper gallium oxide, copper aluminum oxide, molybdenum selenide, and molybdenum sulfide selenide. One type of p-type semiconductor may be used alone, or two or more types may be used in combination.

[0036] The hole transport layer 102 preferably consists essentially of the aforementioned p-type semiconductor, and is preferably the aforementioned p-type semiconductor. The content of the aforementioned p-type semiconductor in the hole transport layer 102 is preferably 80% by mass to 100% by mass, 90% by mass to 100% by mass, 95% by mass to 100% by mass, or 99% by mass to 100% by mass, based on the total amount of the hole transport layer 102.

[0037] The thickness of the hole transport layer 102 is preferably 10 nm to 100 nm, 15 nm to 80 nm, or 20 nm to 60 nm. When the thickness of the hole transport layer 102 is within the above range, holes generated in the light absorbing layer 103 described below can be efficiently extracted from the light absorbing layer 103, and recombination of electrons and holes generated simultaneously with the holes in the light absorbing layer 103 described below can be suppressed, which tends to enable a lighter and more flexible solar cell.

[0038] 1.1.2.2. Light-Absorbing Layer The power generating element layer 109 may have a light-absorbing layer 103. The light-absorbing layer 103 absorbs light such as near-infrared light, visible light, and ultraviolet light to generate electrons and holes. Examples of light such as near-infrared light, visible light, and ultraviolet light include sunlight. The light-absorbing layer 103 preferably contains a perovskite compound, a chalcopyrite compound, or a kesterite compound. One type of perovskite compound may be used alone, or two or more types may be used in combination. One type of chalcopyrite compound may be used alone, or two or more types may be used in combination. Furthermore, one type of kesterite compound may be used alone, or two or more types may be used in combination.

[0039] The perovskite compound may be a compound represented by the general formula AMX ３ and those represented by the general formula A ２ MX ４ Here, M represents a divalent cation, A represents a monovalent cation, and X represents a monovalent anion.

[0040] The monovalent cation A is not particularly limited, and examples thereof include cations of Group 1 elements of the periodic table and organic cations. Among these, cesium ions, rubidium ions, optionally substituted ammonium ions (including amidinium ions), optionally substituted phosphonium ions, and optionally substituted amidinium ions are preferred. Examples of optionally substituted ammonium ions include primary ammonium ions and secondary ammonium ions. Specific examples of optionally substituted ammonium ions include alkylammonium ions, arylammonium ions, amidinium ions, and guanidium ions. In particular, monoalkylammonium ions are preferred to avoid steric hindrance, and alkylammonium ions substituted with one or more fluorine atoms are preferred to improve stability. Furthermore, a combination of two or more cations can also be used as the cation A. Examples of the monovalent cation A include a methylammonium ion, a methylammonium monofluoride ion, a methylammonium difluoride ion, a methylammonium trifluoride ion, an ethylammonium ion, an isopropylammonium ion, an n-propylammonium ion, an isobutylammonium ion, an n-butylammonium ion, a t-butylammonium ion, a dimethylammonium ion, a diethylammonium ion, a phenylammonium ion, a benzylammonium ion, a phenethylammonium ion, a guanidium ion, a formamidinium ion, an acetamidinium ion, and an imidazolium ion.

[0041] The divalent cation M is not particularly limited, and examples thereof include divalent metal cations and semimetal cations. Specific examples include cations of elements in Group 14 of the periodic table, and more specific examples include lead cations (Pb ２＋ ), tin cations (Sn ２＋ ), and germanium cation (Ge ２＋ In addition, a combination of two or more types of cations can be used as the cation M.

[0042] The monovalent anion X is not particularly limited, and examples thereof include a halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, titanate ion, zirconate ion, 2,4-pentanedionate ion, and silicofluoride ion. X may be one type of anion or a combination of two or more types of anions. It is preferable to use a halide ion or a combination of a halide ion and another anion as X. Examples of halide ions X include chloride ions, bromide ions, and iodide ions.

[0043] The perovskite compound includes organic-inorganic perovskite compounds, particularly halide-based organic-inorganic perovskite compounds. Specific examples of perovskite compounds include CH ３ NH ３ PbI ３ , C.H. ３ NH ３ PbBr ３ , C.H. ３ NH ３ PbCl ３ , C.H. ３ NH ３ SnI ３ , C.H. ３ NH ３ SnBr ３ , C.H. ３ NH ３ SnCl ３ , C.H. ３ NH ３ PbI (3-x) Cl x , C.H. ３ NH ３ PbI (3-x) Br x , C.H. ３ NH ３ PbBr (3-x) Cl x , C.H. ３ NH ３ Pb (1-y) Sn y I ３ , C.H. ３ NH３ Pb (1-y) Sn y Br ３ , C.H. ３ NH ３ Pb (1-y) Sn y Cl ３ , C.H. ３ NH ３ Pb (1-y) Sn y I (3-x) Cl x , C.H. ３ NH ３ Pb (1-y) Sn y I (3-x) Br x , and C.H. ３ NH ３ Pb (1-y) Sn y Br (3-x) Cl x , and CH in the above compounds ３ NH ３ Instead of CFH ２ NH ３ , C.F. ２ HNH ３ , C.F. ３ NH ３ , or NH ２ CH=NH ２ In the above formula, x is an arbitrary value of 0 or more and 3 or less, and y is an arbitrary value of 0 or more and 1 or less.

[0044] The chalcopyrite compound is preferably I-III-VI ２ Group I-III-VI chalcopyrite compounds are also included. ２ The group chalcopyrite compound is not particularly limited, but for example, CuAlS ２ , CuAlSe ２ , CuAlTe ２ , CuGaS ２ , CuGaSe ２ , CuGaTe ２ , CuInS ２ , CuInSe ２ , CuInTe ２ , AgAlS ２ , AgAlSe ２ , AgAlTe２ , AgGaS ２ , AgGaSe ２ , AgGaTe ２ , AgInS ２ , AgInSe ２ , AgInTe ２ The "combination of these" is not particularly limited, but examples thereof include CuGaS ２ and CuInSe ２ When combined with Cu(In ｘ Ga １－ｘ ) (Se ｙ S １－ｙ ) ２ (0≦x≦1, 0≦y≦1). Among these chalcopyrite compounds, CuGaS ２ , CuGaSe ２ , CuInS ２ , CuInSe ２ , Cu(In ｘ Ga １－ｘ ) (Se ｙ S １－ｙ ) ２ (0≦x≦1, 0≦y≦1) is preferred, and Cu(In ｘ Ga １－ｘ ) (Se ｙ S １－ｙ ) ２ (0≦x≦1, 0≦y≦1) is more preferable. In the present embodiment, the term "CIS compound" refers to a chalcopyrite compound containing Cu, In, and Se, the term "CIGS compound" refers to a chalcopyrite compound containing Cu, In, Ga, and Se, and the term "CIGSS compound" refers to a chalcopyrite compound containing Cu, In, Ga, Se, and S.

[0045] The kesterite compound is preferably I ２ -II-IV-VI ４ Group I kesterite compounds are exemplified. ２ -II-IV-VI ４ The group kesterite compound is not particularly limited, but for example, Cu ２ ZnSnS ４ , Cu ２ ZnSnSe ４ , Cu２ ZnGeS ４ , Cu ２ ZnGeSe ４ , Cu ２ MnSnS ４ , Cu ２ MnSnSe ４ , Cu ２ MnGeS ４ , Cu ２ MnGeSe ４ , Ag ２ ZnSnS ４ , Ag ２ ZnSnSe ４ , Ag ２ ZnGeS ４ , Ag ２ ZnGeSe ４ , Ag ２ MnSnS ４ , Ag ２ MnSnSe ４ , Ag ２ MnGeS ４ , Ag ２ MnGeSe ４ and combinations thereof. The "combinations thereof" are not particularly limited, but include, for example, Cu ２ ZnSnS ４ and Ag ２ ZnSnSe ４ When combined with ｘ Ag １－ｘ ) ２ ZnSn(S ｙ Se １－ｙ ) ４ (0≦x≦1). ２ ZnSn(S ｘ Se １－ｘ ) ４ (0≦x≦1, 0≦y≦1). Among these kesterite compounds, Cu ２ ZnSnS ４ , Cu ２ ZnSnSe ４ , Ag ２ ZnSnS ４ , Ag ２ ZnSnSe ４ , (Cu ｘ Ag １－ｘ ) ２ ZnSn(Sｙ Se １－ｙ ) ４ (0≦x≦1, 0≦y≦1) is preferred, and (Cu ｘ Ag １－ｘ ) ２ ZnSn(S ｙ Se １－ｙ ) ４ (0≦x≦1, 0≦y≦1) is more preferable. In this embodiment, the term CZTS compound refers to a kesterite compound containing Cu, Zn, Sn, and S, the term ACZTS compound refers to a kesterite compound containing Ag, Cu, Zn, Sn, and S, and the term ACZTSS compound refers to a kesterite compound containing Ag, Cu, Zn, Sn, S, and Se.

[0046] The contents of the perovskite compound, the chalcopyrite compound, and the kesterite compound in the light absorbing layer 103 are not particularly limited as long as the light absorbing layer 103 can absorb light such as visible light and ultraviolet light to generate electrons and holes. More specifically, although not particularly limited, the contents of the perovskite compound, the chalcopyrite compound, and the kesterite compound are, relative to the total mass of the light absorbing layer 103, 50% by mass to 100% by mass, 60% by mass to 100% by mass, 70% by mass to 100% by mass, 80% by mass to 100% by mass, or 90% by mass to 100% by mass.

[0047] In addition to the above materials, the light absorbing layer 103 may contain additives such as a binder and a surfactant. The content of the additives is not particularly limited, but is, for example, 0.1% by mass or more and 10% by mass or less with respect to the total mass of the light absorbing layer 103. The light absorbing layer 103 does not necessarily need to contain the additives.

[0048] The thickness of the light absorbing layer 103 is preferably 0.5 μm to 10.0 μm, 0.5 μm to 7.5 μm, 0.5 μm to 5.0 μm, or 0.5 μm to 3.0 μm. When the thickness of the light absorbing layer 103 is within the above range, it is possible to absorb light such as visible light and ultraviolet light to generate electrons and holes, while also making it possible to make the solar cell lighter and more flexible.

[0049] The solar cell 100 of this embodiment may have two light absorbing layers 103. In this case, the substance contained in the first light absorbing layer 103 and the substance contained in the second light absorbing layer 103 may be different or the same, but it is preferable that they are different. When the solar cell 100 has two light absorbing layers 103, the wavelength range of light that can be absorbed by the light absorbing layer 103 tends to be expanded, and as a result, the performance of the solar cell tends to be improved. Furthermore, the solar cell 100 of this embodiment may have three or more light absorbing layers 103.

[0050] The precursor of the light absorbing layer 103 formed on the first surface 1011 side of the conductive substrate 101 is heat-treated in an atmosphere such as a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, or an iodine atmosphere, thereby forming the light absorbing layer 103. In particular, when the light absorbing layer 103 contains a perovskite compound, a chalcopyrite compound, or a kesterite compound, the precursor of the light absorbing layer 103 is preferably heat-treated in the above-mentioned atmosphere after being formed on the first surface 1011 side of the conductive substrate 101 or on the first surface 1011. Even if such heat treatment is performed when producing the solar cell 100 that constitutes the solar cell module 1 of this embodiment, an increase in the electrical resistance of the conductive substrate 101 can be suppressed, and as a result, an increase in the electrical resistance at the junction regions between the solar cell 100 in the solar cell module 1 can be suppressed.

[0051] The precursor of the light absorbing layer 103 is not particularly limited, but the following substances can be mentioned: When the light absorbing layer 103 contains a perovskite compound, PbI ２ When the light absorbing layer 103 contains a chalcopyrite compound, examples of the layer include a laminate of CuGa, In, etc. When the light absorbing layer 103 contains a kesterite compound, examples of the layer include a laminate of Zn, Sn, Cu, etc.

[0052] 1.1.2.3. Electron Transport Layer The power generating element layer 109 may have an electron transport layer 104. The electron transport layer 104 can efficiently extract electrons generated in the light absorbing layer 103 from the light absorbing layer 103 and suppress recombination of holes and electrons generated simultaneously with the electrons in the light absorbing layer 103. The electron transport layer 104 is preferably an n-type semiconductor. Substances contained in n-type semiconductors are not particularly limited, but examples include zinc oxide, tin oxide, titanium oxide, zinc sulfide oxide (zinc oxide doped with sulfur), magnesium zinc oxide (zinc oxide doped with magnesium), zinc tin oxide (zinc oxide doped with tin), and titanium zinc oxide (zinc oxide doped with titanium). One type of n-type oxide semiconductor may be used alone, or two or more types may be used in combination.

[0053] The electron transport layer 104, which is an n-type oxide semiconductor, is preferably composed essentially of zinc oxide, tin oxide, titanium oxide, zinc oxide sulfide, magnesium zinc oxide, zinc tin oxide, or titanium zinc oxide, and is preferably zinc oxide, tin oxide, titanium oxide, zinc oxide sulfide, magnesium zinc oxide, zinc tin oxide, or titanium zinc oxide. The content of zinc oxide, tin oxide, titanium oxide, zinc oxide sulfide, magnesium zinc oxide, zinc tin oxide, or titanium zinc oxide in the electron transport layer 104, which is an n-type oxide semiconductor, is preferably 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less, based on the total amount of the electron transport layer 104.

[0054] The thickness of the electron transport layer 104 is preferably 50 nm to 200 nm, 55 nm to 175 nm, 60 nm to 150 nm, or 65 nm to 125 nm. When the thickness of the electron transport layer 104 is within the above range, electrons generated in the light absorbing layer 103 can be efficiently extracted from the light absorbing layer 103, and recombination of holes and electrons generated simultaneously with the electrons in the light absorbing layer 103 can be suppressed, which tends to enable a lighter and more flexible solar cell.

[0055] 1.1.3 Electrode The solar cell 100 has an electrode 110. The electrode 110 is provided to extract a current caused by electrons generated in the light absorption layer 103, for example.

[0056] 1.1.3.1. Electrode Layer The electrode 110 may have an electrode layer 105. In the solar cell 100, the light absorbing layer 103 absorbs light that has passed through the electrode layer 105. Therefore, in order to increase the amount of light absorbed by the light absorbing layer 103, the electrode layer 105 is preferably a transparent electrode layer. A transparent electrode is an electrode made of a material that has both high electrical conductivity and high visible light transmittance. There are no particular limitations on the high electrical conductivity, but for example, a material having a specific resistance of 5.0×10 ―３ The term "high visible light transmittance" refers to a resistance of Ωcm or less. High visible light transmittance is not particularly limited, but for example, refers to an average transmittance of 80% or more in the wavelength region of 400 nm or more and 1300 nm or less. Known materials can be used as the transparent electrode material, and examples thereof include indium tin oxide (ITO), hydrogen-containing indium oxide (IOH), fluorine-containing tin oxide (FTO), boron-containing zinc oxide (ZnO:B), and aluminum-containing zinc oxide (ZnO:Al).

[0057] When the electrode layer 105 is a transparent electrode, the content of the above material is not particularly limited as long as the electrode layer 105 functions as a transparent electrode. More specifically, although not particularly limited, the content of the above material is, relative to the total mass of the electrode layer 105, 50% by mass to 100% by mass, 60% by mass to 100% by mass, 70% by mass to 100% by mass, 80% by mass to 100% by mass, 90% by mass to 100% by mass, or 95% by mass to 100% by mass.

[0058] The thickness of the electrode layer 105 is not particularly limited, but is, for example, 100 nm to 1500 nm, or 200 nm to 1000 nm. When the thickness of the electrode layer 105 is within the above range, it tends to be possible to sufficiently extract current without loss, while making the solar cell lighter and more flexible.

[0059] 1.1.3.2 Grid Electrode The electrode 110 may have a grid electrode 106. The material of the grid electrode 106 is not particularly limited as long as it is conductive, and examples thereof include metals such as Mo, Cr, Ag, Cu, Ni, Al, and Ti; conductive inorganic compounds other than metals; and conductive organic compounds. The grid electrode 106 may be made of one material alone or two or more materials in combination.

[0060] The content of the above-mentioned material in the grid electrode 106 is not particularly limited as long as the grid electrode 106 functions as an electrode. More specifically, although not particularly limited, the content of the above-mentioned material relative to the total mass of the grid electrode 106 is 50% by mass to 100% by mass, 60% by mass to 100% by mass, 70% by mass to 100% by mass, 80% by mass to 100% by mass, or 90% by mass to 100% by mass.

[0061] The thickness of the grid electrode 106 is not particularly limited, but is, for example, 5 μm to 50 μm. When the thickness of the grid electrode 106 is within this range, it tends to be possible to extract sufficient current without loss, while making the solar cell lighter and more flexible.

[0062] The electrode 110 may include only the electrode layer 105, may include only the grid electrode 106, or may include the electrode layer 105 and the grid electrode 106. The electrode 110 preferably includes the electrode layer 105 and the grid electrode 106.

[0063] 1.1.4. Conductive Corrosion Prevention Layer At least one of the solar cells 100 constituting the solar cell module 1 has a conductive corrosion prevention layer 107. The conductive corrosion prevention layer 107 is provided on or near the second surface 1012 of the conductive substrate 101. When a laminate including at least the conductive corrosion prevention layer 107, the conductive substrate 101, and a precursor of the light absorbing layer 103, in this order, is heat-treated, the conductive substrate 101 and the conductive corrosion prevention layer 107 provided on the second surface 1012 of the conductive substrate 101 are also subjected to the heat treatment, along with the precursor of the light absorbing layer 103. Here, an increase in the electrical resistance of the conductive substrate 101 is suppressed in the region of the second surface 1012 where the conductive corrosion prevention layer 107 is present. Furthermore, the conductive corrosion prevention layer 107 is less likely to increase in electrical resistance even when subjected to heat treatment.

[0064] The conductive corrosion prevention layer 107 may be provided on the surface of the conductive substrate 101 facing the second surface 1012, or on at least a portion of the second surface 1012, or may be provided on the entire surface of the conductive substrate 101 facing the second surface 1012, or on the entire surface of the second surface 1012.

[0065] The conductive corrosion-preventing layer 107 is subjected to heat treatment together with the precursor of the light absorbing layer 103. The heat treatment of the precursor of the light absorbing layer 103 is performed in a corrosive gas atmosphere such as a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, or an iodine atmosphere at a high temperature (e.g., 500°C). The conductive corrosion-preventing layer 107 subjected to heat treatment in such an environment is at least partially denatured on the surface facing the conductive adhesive member 200 (described later). For example, the conductive corrosion-preventing layer 107 subjected to heat treatment at a high temperature (e.g., 500°C) in a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, or an iodine atmosphere is at least partially sulfurized, selenized, chlorided, brominated, or iodized on the surface facing the conductive adhesive member 200 (described later). Even if at least a portion of the conductive corrosion-preventing layer 107 is denatured on the surface facing the conductive adhesive member 200 (described later), the electrical resistance of the conductive corrosion-preventing layer 107 tends to be less likely to increase. Therefore, in the solar cell module 1, the electrical resistance in the joint regions between the solar cells 100 tends to be low.

[0066] In the solar cell module 1, the conductive corrosion prevention layer 107 of one solar cell 100 may be joined to the electrode 110 of another solar cell 100 via a conductive adhesive member.

[0067] The conductive corrosion prevention layer 107 preferably contains metallic molybdenum or a molybdenum alloy. The molybdenum alloy preferably contains one or more elements selected from the group consisting of nickel, niobium, chromium, tungsten, silicon, and carbon. Among these, a molybdenum alloy containing nickel is preferred, and a nickel-molybdenum alloy is more preferred. The metallic molybdenum or molybdenum alloy may be used alone or in combination of two or more.

[0068] The content of nickel element relative to the content of molybdenum element in the nickel-molybdenum alloy is preferably 10 mass% or more and 100 mass% or less, 15 mass% or more and 85 mass% or less, 20 mass% or more and 70 mass% or less, or 25 mass% or more and 55 mass% or less.

[0069] As a method for adjusting the content of nickel element relative to the content of molybdenum element in the nickel-molybdenum alloy, there is a method of adjusting the amounts of metallic molybdenum and metallic nickel used when preparing the alloy.

[0070] The conductive corrosion prevention layer 107 preferably consists essentially of metallic molybdenum or a molybdenum alloy, and is preferably metallic molybdenum or a molybdenum alloy. The content of metallic molybdenum or a molybdenum alloy in the conductive corrosion prevention layer 107 is preferably 80% by mass to 100% by mass, 90% by mass to 100% by mass, 95% by mass to 100% by mass, or 99% by mass to 100% by mass, based on the total amount of the hole transport layer 102.

[0071] The thickness of the conductive corrosion prevention layer 107 is preferably 50 nm to 350 nm, 75 nm to 325 nm, 100 nm to 300 nm, 125 nm to 275 nm, or 150 nm to 250 nm.

[0072] As described above, in the production of the solar cell 100 of this embodiment, the conductive corrosion-preventing layer 107 is subjected to heat treatment together with the precursor of the light absorbing layer 103 and the conductive substrate 101. Therefore, in order to prevent warping of the solar cell 100 after the heat treatment, it is preferable that the difference in the linear expansion coefficient between the conductive substrate 101 and the conductive corrosion-preventing layer 107 at high temperatures is small. From this perspective, the difference in the linear expansion coefficient between the conductive substrate 101 and the conductive corrosion-preventing layer 107 at 500°C is preferably 5.0×10 －６ / °C or less, and 0 / °C or more and 5.0 x 10 －６ / °C or less, and 0 / °C or more 4.5 x 10 －６ / °C or less, and 0 / °C or more and 4.0 x 10 －６ / °C or less, and 0 / °C or more 3.5 x 10 －６ / °C or less, and 0 / °C or more 3.0 x 10 －６ / °C or less, and 0 / °C or more 2.5 x 10 －６ / °C or less.

[0073] In order to prevent warpage in the solar cell 100, it is preferable that the difference in the linear expansion coefficient between the conductive substrate 101 and the conductive corrosion-preventing layer 107 at each temperature is small. From this viewpoint, the difference in the linear expansion coefficient between the conductive substrate 101 and the conductive corrosion-preventing layer 107 at 200°C is preferably 4.0×10 －６ / °C or less, and 0 / °C or more and 4.0 x 10 －６ / °C or less, and 0 / °C or more 3.5 x 10 －６ / °C or less, and 0 / °C or more 3.0 x 10 －６ / °C or less, and 0 / °C or more 2.5 x 10 －６ / °C or less, and 0 / °C or more 2.0 x 10 －６ / °C or less.

[0074] The difference in the linear expansion coefficient between the conductive substrate 101 and the conductive corrosion prevention layer 107 at 20° C. is preferably 3.5×10 －６ / °C or less, and 0 / °C or more 3.5 x 10 －６ / °C or less, and 0 / °C or more 3.0 x 10 －６ / °C or less, and 0 / °C or more 2.5 x 10 －６ / °C or less, and 0 / °C or more 2.0 x 10 －６ / °C or less, and 0 / °C or more and 1.5 x 10 －６ / °C or less.

[0075] The linear expansion coefficients of the conductive substrate 101 and the conductive corrosion prevention layer 107 are not particularly limited, but can be adjusted, for example, by changing the materials that make up the conductive substrate 101 and the conductive corrosion prevention layer 107.

[0076] The linear expansion coefficient can be measured in accordance with JIS Z2285:2003, except that the temperature is 20°C, 200°C, or 500°C.

[0077] 1.1.5. Contact Resistance Reduction Layer The solar cell 100 may have a contact resistance reduction layer 108. In the solar cell module 1, when the first solar cell 100A has a contact resistance reduction layer 108A, the contact resistance reduction layer 108A is provided between the conductive corrosion prevention layer 107A and the conductive adhesive member 200 described below. The contact resistance reduction layer 108 tends to be able to further suppress an increase in electrical resistance in the bonding regions between the solar cell 100 in the solar cell module 1.

[0078] The reason why the provision of the contact resistance reducing layer 108 can prevent the electrical resistance in the bonding region between the solar cell 100 from increasing is not particularly limited, but is thought to be, for example, as follows: In addition to the fact that the contact resistance reducing layer 108 has low electrical resistance, the contact resistance reducing layer 108 tends to be bonded to both the conductive corrosion prevention layer 107 and the conductive adhesive member 200 with low contact resistance.

[0079] Alternatively, the solar cell 100 may have a contact resistance reducing layer 108 on the side of the conductive corrosion prevention layer 107 opposite to the conductive substrate 101 .

[0080] Contact resistance reducing layer 108 is preferably provided on at least a partially modified surface of conductive corrosion prevention layer 107 facing conductive adhesive member 200. Contact resistance reducing layer 108 may be provided on the entire surface of conductive corrosion prevention layer 107 on the side opposite conductive substrate 101, or may be provided on a partial region of the surface on the side opposite conductive substrate 101.

[0081] The material of the contact resistance reduction layer 108 is not particularly limited as long as it is conductive, and may be, for example, a metal containing Ag, Sn, Cr, Cu, or Ni. The contact resistance reduction layer 108 preferably contains one or more metals selected from the group consisting of metallic silver, metallic tin, a silver alloy, and a tin alloy. Specific examples of silver alloys and tin alloys include tin-zinc alloys, tin-silver alloys, tin-silver-copper alloys, and tin-bismuth alloys. The grid electrode 106 may be made of one material alone or two or more materials in combination.

[0082] The content of the above material in the contact resistance reducing layer 108 relative to the total mass of the grid electrode 106 is not particularly limited, but is, for example, 50% by mass to 100% by mass, 60% by mass to 100% by mass, 70% by mass to 100% by mass, 80% by mass to 100% by mass, or 90% by mass to 100% by mass.

[0083] The thickness of the contact resistance reducing layer 108 is preferably 25 nm or more and 125 nm or less, and more preferably 50 nm or more and 100 nm or less.

[0084] In the solar cell module 1, the contact resistance reducing layer 108 of one solar cell 100 may be joined to the electrode 110 of another solar cell 100 via a conductive adhesive member.

[0085] 1.2 Conductive Adhesive Member The solar cell module 1 has a conductive adhesive member 200. The conductive adhesive member 200 is provided to join the solar cell cells 100 together and to establish electrical continuity between the solar cell cells 100.

[0086] Examples of the conductive adhesive member 200 include a conductive paste and a conductive sheet, but a conductive sheet is preferred from the viewpoint of more easily and firmly bonding the solar cell 100 together. The conductive sheet preferably includes a conductive mesh fabric having a metal coating. Specifically, the conductive sheet preferably has a conductive mesh fabric having a metal coating and a non-conductive adhesive material present in the opening areas of the mesh. Examples of such a conductive sheet include the conductive double-sided tape MST50 (product name) or MST30 (product name) manufactured by Seiren Co., Ltd.

[0087] When a conductive mesh fabric having a metal coating is used as the conductive adhesive member 200, the electrical resistance in the bonding regions between the solar cell 100 tends to be further reduced.

[0088] The thickness of the conductive adhesive member 200 is not particularly limited, but is, for example, 10 μm to 100 μm, 15 μm to 75 μm, or 20 μm to 50 μm.

[0089] 2. Manufacturing Method of Solar Cell The manufacturing method of the solar cell 100 of this embodiment includes: a laminate preparation step of preparing a laminate including at least the conductive corrosion prevention layer 107, the conductive substrate 101, and a precursor of the light absorbing layer 103, in this order; a heat treatment step of heat treating the laminate in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere; a power generating element layer formation step of forming a power generating element layer 109 having the light absorbing layer 103 formed by the heat treatment step; and an electrode formation step of forming an electrode 110 on the power generating element layer 109.

[0090] In the solar cell 100 manufactured by the manufacturing method of this embodiment, a laminate having at least the conductive corrosion prevention layer 107, the conductive substrate 101, and the precursor of the light absorbing layer 103, in this order, is heat-treated in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere.Therefore, in the region of the second surface 1012 of the conductive substrate 101 where the conductive corrosion prevention layer 107 is present, the second surface 1012 is not modified, and the electrical resistance of the conductive substrate 101 does not become high in that region.

[0091] Each step that may be included in the method for manufacturing the solar cell 100 of this embodiment will be described in detail below.

[0092] 2.1 Laminate Preparation Step In the laminate preparation step, a laminate is prepared that includes, in this order, at least the conductive corrosion prevention layer 107, the conductive substrate 101, and a precursor of the light absorbing layer 103. A sputtering method, for example, can be used to prepare such a laminate.

[0093] Specifically, a precursor of the light absorbing layer 103 may be deposited on the first surface 1011 of the conductive substrate 101 using a sputtering method, and a conductive corrosion prevention layer 107 may be deposited on the second surface 1012 of the conductive substrate 101 using a sputtering method.

[0094] The sputtering may be performed in an argon atmosphere using the material of each layer as a sputtering target. For example, when forming conductive corrosion prevention layer 107 on second surface 1012 by sputtering, metal molybdenum or a molybdenum alloy may be used as the sputtering target and sputtering may be performed in an argon atmosphere.

[0095] In the heat treatment step, the laminate prepared in the laminate preparation step is heat-treated in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere. By heat-treating the laminate in this manner, the light absorbing layer 103 is formed on the first surface 1011 side of the conductive substrate 101.

[0096] The laminate also includes a conductive corrosion-preventing layer 107 on the second surface 1012 side of the conductive substrate 101. Therefore, when the laminate is subjected to the heat treatment described above, an increase in the electrical resistance of the conductive substrate 101 can be suppressed in the region of the second surface 1012 where the conductive corrosion-preventing layer 107 is present. Furthermore, the electrical resistance of the conductive corrosion-preventing layer 107 is unlikely to increase even when subjected to the heat treatment. As a result, an increase in the electrical resistance of the solar cell 100 fabricated using the laminate can be suppressed.

[0097] The atmosphere in which the heat treatment step is performed is one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere. Specifically, the atmosphere may include one selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere, or may be a mixed atmosphere including two or more selected from the group consisting of the above. Furthermore, after the heat treatment step is performed in one atmosphere, a further heat treatment step may be performed in a different atmosphere. Specifically, after the heat treatment step is performed in a selenium atmosphere, a heat treatment step may be performed in a sulfur atmosphere.

[0098] When the light absorbing layer 103 is a chalcopyrite compound or a kesterite compound, it is preferable that the heat treatment step is performed in one or more of a sulfur atmosphere and a selenium atmosphere, and it is more preferable that the heat treatment step is performed in a selenium atmosphere and then in a sulfur atmosphere.

[0099] When the light absorbing layer 103 is made of a perovskite compound, the heat treatment step is preferably carried out in one or more atmospheres selected from the group consisting of a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere.

[0100] In this embodiment, the sulfur atmosphere refers to an atmosphere containing a gas containing sulfur element. That is, an atmosphere containing a gas containing sulfur element and other gases not containing sulfur element is included in the sulfur atmosphere. The same applies to a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere.

[0101] In the heat treatment step, in the case of a sulfur atmosphere or a selenium atmosphere, the heat treatment temperature is preferably 300° C. or higher and 700° C. or lower, 350° C. or higher and 650° C. or lower, 400° C. or higher and 600° C. or lower, or 500° C. or higher and 600° C. or lower. In the case of a chlorine atmosphere, a bromine atmosphere, or an iodine atmosphere, the heat treatment temperature is preferably 60° C. or higher and 230° C. or lower, 70° C. or higher and 200° C. or lower, or 80° C. or higher and 170° C. or lower.

[0102] In the heat treatment step, the heat treatment time is preferably 1 minute or more and 30 minutes or less, 3 minutes or more and 15 minutes or less, or 5 minutes or more and 15 minutes or less.

[0103] 2.3. Power Generation Element Layer Forming Step In the power generation element layer forming step, the power generation element layer 109 is formed on the first surface 1011 of the conductive substrate 101. If the power generation element layer 109 consists only of the light absorbing layer 103, a heat treatment step is performed to form the light absorbing layer 103, thereby completing the power generation element layer forming step. If the power generation element layer 109 has the light absorbing layer 103 and other layers, in the power generation element layer forming step, for example, layers constituting the power generation element layer 109 other than the light absorbing layer 103 are formed on the light absorbing layer 103 formed by the heat treatment step. More specifically, for example, in the power generation element layer forming step, the electron transport layer 104 is formed on the light absorbing layer 103 formed by the heat treatment step.

[0104] In the power generation element layer forming step, the layers may be formed by, for example, sputtering. Sputtering may be performed in an argon atmosphere using the material of each layer as a sputtering target. For example, when forming the electron transport layer 104 on the light absorption layer 103 by sputtering, zinc oxide and titanium oxide may be used as sputtering targets and sputtering may be performed in an argon atmosphere to form an electron transport layer that is an n-type oxide semiconductor containing zinc titanium oxide.

[0105] 2.4 Electrode Forming Step In the electrode forming step, the electrode 110 is formed on the power generating element layer 109. Specifically, the electrode 110 is formed on the side of the power generating element layer 109 opposite the conductive substrate 101 or on the surface opposite the conductive substrate 101. Examples of a method for forming the electrode 110 include sputtering.

[0106] Specifically, the electrode layer 105 may be laminated on the power generating element layer 109 by sputtering, and the grid electrode 106 may be provided by sputtering on the electrode layer 105. The sputtering may be performed in an argon atmosphere using the materials of each component as sputtering targets.

[0107] Alternatively, a method in which the sputtering method is combined with another method may be used. Specifically, the electrode layer 105 may be laminated on the power generation element layer 109 by sputtering, and the grid electrode 106 may be provided on the electrode layer 105 by vapor deposition, a method of printing a paste-like conductive material, or a method of crimping a conductive wire.

[0108] 2.5. Contact Resistance Reduction Layer Forming Step The method for manufacturing a solar cell according to this embodiment may include a contact resistance reduction layer forming step. The contact resistance reduction layer forming step is performed after the heat treatment step. In the contact resistance reduction layer forming step, the contact resistance reduction layer 108 is formed on the conductive corrosion prevention layer 107. Methods for forming the contact resistance reduction layer 108 include, for example, sputtering, plating, vapor deposition, and ultrasonic soldering. In the sputtering method, the materials of each component may be used as sputtering targets in an argon atmosphere.

[0109] The contact resistance reducing layer 108 may be provided on the entire surface of the conductive corrosion prevention layer 107 opposite the conductive substrate 101, or may be provided on a partial area of ​​the surface opposite the conductive substrate 101.

[0110] 3. Manufacturing Method of Solar Cell Module The manufacturing method of solar cell module 1 of this embodiment includes a bonding step of obtaining first solar cell 100A and second solar cell 100B, and bonding conductive corrosion prevention layer 107A of first solar cell 100A to second electrode 110B of second solar cell 100B via at least conductive adhesive member 200.

[0111] In the solar cell module 1 manufactured by the manufacturing method of this embodiment, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B are joined via at least the conductive adhesive member 200. This makes it possible to prevent the electrical resistance in the joining region between the solar cells 100 in the solar cell module 1 from becoming high.

[0112] Hereinafter, each step that may be included in the method for manufacturing the solar cell module 1 of this embodiment will be described in detail.

[0113] 3.1 Bonding Step In the bonding step, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B are bonded together via at least the conductive adhesive member 200. In the bonding step, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B may be bonded together via only the conductive adhesive member 200, or may be bonded together via the contact resistance reducing layer 108A and the conductive adhesive member 200. That is, in the bonding step, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B may be bonded together via the conductive adhesive member 200, or the contact resistance reducing layer 108A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B may be bonded together via the conductive adhesive member 200.

[0114] When the contact resistance reducing layer 108A is provided on a partial area or the entire surface of the conductive corrosion prevention layer 107A on the side opposite the first conductive substrate 101A, the conductive corrosion prevention layer 107A of the first solar cell 100A and the second electrode 110B of the second solar cell 100B are joined via the contact resistance reducing layer 108A and the conductive adhesive member 200.

[0115] By joining the first solar cell 100A and the second solar cell 100B using the joining step of this embodiment, it tends to be possible to achieve simpler and stronger joining between the solar cells 100.

[0116] 3.1.1 Thermocompression Bonding Step The bonding step preferably includes a thermocompression bonding step in which the first solar cell 100A, the second solar cell 100B, and the conductive adhesive member 200 are heated to 125°C or higher and pressurized to 0.1 MPa or higher for 3 minutes or longer. By including the thermocompression bonding step in the bonding step, the first solar cell 100A and the second solar cell 100B tend to be bonded more firmly via the conductive adhesive member 200.

[0117] The time for carrying out the thermocompression bonding step is preferably 3 minutes or more, 3 minutes to 60 minutes, 10 minutes to 50 minutes, or 15 minutes to 40 minutes.

[0118] The heating temperature in the thermocompression bonding step is preferably 125°C or higher, 125°C or higher and 200°C or lower, 130°C or higher and 180°C or lower, or 135°C or higher and 160°C or lower.

[0119] The pressure applied in the thermocompression bonding step is preferably 0.1 MPa or more, 0.1 MPa to 1.5 MPa or less, or 0.1 MPa to 1.0 MPa or less. Alternatively, the pressure applied in the thermocompression bonding step is preferably 0.3 MPa to 1.5 MPa or less, or 0.5 MPa to 1.0 MPa or less.

[0120] 4. Method of Using Solar Cells In the solar cell module 1 of this embodiment, the solar cell cells 100 are easily and firmly connected to each other. Furthermore, by forming the solar cell 100 to be sufficiently thin, the solar cell module 1 can be formed thin, and the solar cell module 1 has flexibility. Therefore, the solar cell module 1 can be suitably used in various environments from the viewpoint of mechanical vibration and thermal shock, such as electric vehicles, electric aircraft, and artificial satellites. Furthermore, because the solar cell module 1 has low-resistance series connections between the solar cell cells 100, it can provide sufficient power generation even when used in the various environments described above.

[0121] The solar cell module 1 of this embodiment can also be used as an independent power source device for street lights, sensors, digital signage, etc. The solar cell module 1 of this embodiment can also be used as a mobile energy device.

[0122] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples. Furthermore, unless otherwise specified, experiments in the examples and comparative examples were carried out at room temperature (25°C) and 1 atmosphere.

[0123] [Example 1] In Example 1, a 50 μm thick titanium foil was used as the conductive substrate. CuGa and In, precursors of a light absorbing layer made of a CIGSS compound, were laminated to a thickness of 2 μm on this conductive substrate using a sputtering method. A conductive corrosion prevention layer made of metal molybdenum was formed to a thickness of 200 nm using a sputtering method on the surface of the conductive substrate opposite the precursor of the light absorbing layer. In this manner, a laminate was prepared. The precursor of the light absorbing layer used in each example and comparative example was the same as in Example 1.

[0124] The laminate containing the precursor was subjected to heat treatment at 500° C. for 5 minutes in a selenium atmosphere, and then to heat treatment at 550° C. for 15 minutes in a sulfur atmosphere to form a light absorbing layer with a thickness of 2 μm.

[0125] An electron transport layer, which was an n-type oxide semiconductor containing titanium zinc oxide, was formed to a thickness of 80 nm on the light absorption layer of the heat-treated laminate using a sputtering method. A transparent electrode layer containing hydrogen-containing indium oxide (IOH) was formed to a thickness of 300 nm on this electron transport layer using a sputtering method. A grid electrode made of metallic silver was formed to a thickness of 5 μm on the electrode layer using a vapor deposition method. In this manner, two solar cells were produced.

[0126] The conductive corrosion prevention layer of one solar cell was joined to the grid electrode of the other solar cell with a conductive adhesive member (double-sided conductive tape manufactured by Seiren Co., Ltd., product name: MST50), and then both solar cells and the conductive adhesive member were heated to 150°C and thermocompression-bonded for 30 minutes while applying a pressure of 0.1 MPa. In this way, the solar cell module of Example 1 was obtained.

[0127] Example 2 A laminate was obtained in the same manner as in Example 1 and subjected to heat treatment in the same manner as in Example 1. An electron transport layer and an electrode were formed on the heat-treated laminate in the same manner as in Example 1. Then, a contact resistance-reducing layer made of metallic silver was formed to a thickness of 100 nm on the surface of the conductive corrosion prevention layer opposite the conductive substrate using a sputtering method. In this manner, two solar cells were produced. The contact resistance-reducing layer of one solar cell and the grid electrode of the other solar cell were bonded with a conductive adhesive member (double-sided conductive tape manufactured by Seiren Co., Ltd., product name: MST50), and then both solar cells and the conductive adhesive member were heated to 150°C and thermocompressed for 30 minutes while applying a pressure of 0.1 MPa. In this manner, a solar cell module of Example 2 was obtained.

[0128] Example 3 A solar cell module of Example 3 was obtained in the same manner as in Example 1, except that a conductive corrosion-preventing layer made of a molybdenum-nickel alloy (in which the mass percentage of molybdenum: the mass percentage of nickel in the alloy = 70:30) was provided by sputtering instead of the conductive corrosion-preventing layer made of metallic molybdenum in Example 1. Note that when a molybdenum-nickel alloy was used in each of the Examples and Comparative Examples, a molybdenum-nickel alloy in which the mass percentage of molybdenum: the mass percentage of nickel in the alloy was 70:30 was used.

[0129] Example 4 A solar cell module of Example 4 was obtained in the same manner as in Example 2, except that a conductive corrosion-preventing layer made of a molybdenum-nickel alloy was provided by sputtering instead of the conductive corrosion-preventing layer made of metallic molybdenum.

[0130] In Comparative Example 1, a titanium foil having a thickness of 50 μm was used as the conductive substrate. A precursor of the light absorbing layer made of a CIGSS compound was deposited on the conductive substrate by sputtering to a thickness of 2 μm. In this manner, a laminate was prepared.

[0131] The laminate containing the precursor was subjected to heat treatment at 500° C. for 5 minutes in a selenium atmosphere, and then to heat treatment at 550° C. for 15 minutes in a sulfur atmosphere to form a light absorbing layer with a thickness of 2 μm.

[0132] An electron transport layer, which was an n-type oxide semiconductor containing titanium zinc oxide, was formed to a thickness of 80 nm on the light absorption layer of the heat-treated laminate using a sputtering method. A transparent electrode layer containing hydrogen-containing indium oxide (IOH) was formed to a thickness of 300 nm on this electron transport layer using a sputtering method. A grid electrode made of metallic silver was formed to a thickness of 5 μm on the electrode layer using a vapor deposition method. In this manner, two solar cells were produced.

[0133] The conductive substrate of one solar cell and the grid electrode of the other solar cell were joined with a conductive adhesive member (double-sided conductive tape manufactured by Seiren Co., Ltd., product name: MST50), and then both solar cells and the conductive adhesive member were heated to 150°C and thermocompression-bonded for 30 minutes while applying a pressure of 0.1 MPa. In this way, the solar cell module of Comparative Example 1 was obtained.

[0134] Comparative Example 2 A laminate was obtained in the same manner as in Comparative Example 1 and subjected to heat treatment in the same manner as in Comparative Example 1. An electron transport layer and an electrode layer were formed on the heat-treated laminate in the same manner as in Comparative Example 1. Then, a contact resistance-reducing layer made of metallic silver was formed to a thickness of 200 nm on the surface of the conductive substrate opposite the light absorption layer using a sputtering method. In this manner, two solar cells were produced. The contact resistance-reducing layer of one solar cell and the grid electrode of the other solar cell were bonded with a conductive adhesive member (double-sided conductive tape manufactured by Seiren Co., Ltd., product name: MST50). Then, both solar cells and the conductive adhesive member were heated to 150°C and thermocompressed for 30 minutes while applying a pressure of 0.1 MPa. In this manner, a solar cell module of Comparative Example 2 was obtained.

[0135] Example 5 A solar cell module of Example 5 was obtained in the same manner as in Example 2, except that the contact resistance reducing layer was formed to a thickness of 200 nm by vacuum deposition instead of by sputtering.

[0136] Example 6 A solar cell module of Example 6 was obtained in the same manner as Example 2, except that instead of forming a contact resistance reducing layer made of metallic silver by sputtering in Example 2, a contact resistance reducing layer made of a tin-zinc alloy was formed to a thickness of 5 μm by ultrasonic soldering.

[0137] Example 7 Two solar cells were fabricated in the same manner as in Example 4, except that instead of forming a contact resistance-reducing layer made of metallic silver by sputtering, a contact resistance-reducing layer made of a tin-zinc alloy was formed to a thickness of 5 μm by ultrasonic soldering.

[0138] The contact resistance reducing layer of one solar cell was joined to the grid electrode of the other solar cell with a conductive adhesive member (double-sided conductive tape manufactured by Seiren Co., Ltd., product name: MST50), and then both solar cells and the conductive adhesive member were heated to 75°C and thermocompressed for 0.5 minutes while applying a pressure of 0.1 MPa. In this way, the solar cell module of Example 7 was obtained.

[0139] [Examples 8 to 21] In Examples 8 to 21, the solar cell modules of Examples 8 to 21 were obtained in the same manner as in Example 7, except that the temperature, time, and pressure conditions for the thermocompression bonding step were changed as shown in Table 3.

[0140] [Evaluation] (Joint Resistance Ratio to Soldering) First, a control solar cell module was fabricated as follows. A 50 μm thick titanium foil was used as the conductive substrate. A precursor of the light absorbing layer made of a CIGSS compound was deposited on this conductive substrate by sputtering to a thickness of 2 μm. In this way, a laminate was prepared.

[0141] The laminate containing the precursor was subjected to heat treatment at 500° C. for 5 minutes in a selenium atmosphere, and then to heat treatment at 550° C. for 15 minutes in a sulfur atmosphere to form a light absorbing layer with a thickness of 2 μm.

[0142] An electron transport layer, which was an n-type oxide semiconductor containing titanium zinc oxide, was formed to a thickness of 80 nm on the light absorption layer of the heat-treated laminate using a sputtering method. A transparent electrode layer containing hydrogen-containing indium oxide (IOH) was formed to a thickness of 300 nm on this electron transport layer using a sputtering method. A grid electrode made of metallic silver was formed to a thickness of 5 μm on the electrode layer using a vapor deposition method. In this manner, two solar cells were produced.

[0143] The conductive substrate of one solar cell was ultrasonically soldered to the grid electrode of the other solar cell. In this way, a control solar cell module was obtained. In the solar cells constituting the control solar cell module, the exposed surface of the conductive substrate was modified by heat treatment. However, because the conductive substrate of one solar cell was joined to the grid electrode of the other solar cell by ultrasonic soldering, the effect of this modification on the joint resistance in the joint region between the solar cells was negligible or nonexistent.

[0144] For the control solar cell module, the junction resistance in the junction region between the solar cells was determined. Furthermore, for each example and comparative example, the junction resistance in the junction region between the solar cells was determined. The junction resistance of the solar cell module of each example and comparative example was then divided by the junction resistance of the control solar cell module to determine the junction resistance ratio for each example and comparative example.

[0145] Tables 1 to 3 show the evaluation results of each example and comparative example.

[0146]

[0147]

[0148]

[0149] The linear expansion coefficients of layers composed of titanium metal, molybdenum metal, nickel metal, niobium metal, chromium metal, tungsten metal, carbon, silicon, and a nickel-molybdenum alloy were measured at 20°C, 200°C, and 500°C. The results are shown in Table 4. In Table 4, the alloy designated Mo90Ni10 represents a molybdenum-nickel alloy in which the ratio of the molybdenum content to the nickel content (mass % of molybdenum:mass % of nickel in the alloy) is 90:10. Mo80Ni20, Mo70Ni30, Mo60Ni40, and Mo50Ni50 represent molybdenum-nickel alloys in which the ratios are 80:20, 70:30, 60:40, and 50:50, respectively.

[0150] The linear expansion coefficient of each layer was measured in accordance with JIS Z2285:2003, except that the temperature was 20°C, 200°C, or 500°C.

[0151]

[0152] Solar cell modules were fabricated using a conductive substrate made of titanium metal and a conductive corrosion-preventing layer made of molybdenum metal or a molybdenum-nickel alloy listed in Table 4, with the exception of the method being the same as in Example 1. The results showed that the smaller the difference in the linear expansion coefficient between the conductive substrate and the conductive corrosion-preventing layer at 20°C, 200°C, and 500°C, the more reduced the warpage of the solar cell, and as a result, the more reduced the warpage of the solar cell module.

[0153] <Supplementary Notes> Embodiments of the present disclosure include the following: [1] A solar cell module comprising: a first solar cell having at least a conductive corrosion prevention layer, a first conductive substrate, a first power generation element layer, and a first electrode, in this order; and a second solar cell having at least a second conductive substrate, a second power generation element layer, and a second electrode, in this order, wherein the conductive corrosion prevention layer of the first solar cell and the second electrode of the second solar cell are joined via at least a conductive adhesive member. [2] The solar cell module according to [1], wherein the first solar cell further has a contact resistance reducing layer between the conductive corrosion prevention layer and the conductive adhesive member. [3] The solar cell module according to [2], wherein the contact resistance reducing layer contains one or more selected from the group consisting of metallic silver, metallic tin, a silver alloy, and a tin alloy. [4] The difference in linear expansion coefficient between the first conductive substrate and the conductive corrosion prevention layer at 500°C is 5.0 × 10 －６ / °C or less. [5] The solar cell module according to any one of [1] to [4], wherein at least a portion of the conductive corrosion prevention layer is sulfided, selenized, chlorinated, brominated, or iodized on the surface facing the conductive adhesive member. [6] The solar cell module according to any one of [1] to [5], wherein the conductive corrosion prevention layer contains metallic molybdenum or a molybdenum alloy. [7] The solar cell module according to [6], wherein the conductive corrosion prevention layer contains a molybdenum alloy, and the molybdenum alloy contains one or more elements selected from the group consisting of nickel, niobium, chromium, tungsten, silicon, and carbon. [8] The solar cell module according to any one of [1] to [7], wherein the conductive adhesive member comprises a conductive mesh fabric having a metal coating. [9] A solar cell comprising at least a conductive corrosion prevention layer, a conductive substrate, a power generation element layer, and an electrode, in this order.

[10] The solar cell according to [9], further comprising a contact resistance reducing layer on the side of the conductive corrosion prevention layer opposite the conductive substrate.

[11] A method for manufacturing a solar cell, comprising: a laminate preparation step of preparing a laminate comprising at least a conductive corrosion prevention layer, a conductive substrate, and a precursor of a light absorbing layer, in this order; a heat treatment step of heat treating the laminate in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere; a power generation element layer formation step of forming a power generation element layer having the light absorbing layer formed by the heat treatment step; and an electrode formation step of forming an electrode on the power generation element layer.

[12] The manufacturing method according to

[11] , further comprising, after the heat treatment step, a contact resistance reducing layer formation step of forming a contact resistance reducing layer on the conductive corrosion prevention layer.

[13] A method for manufacturing a solar cell module, further comprising: obtaining a first solar cell and a second solar cell by the manufacturing method according to

[11] , and joining the conductive corrosion prevention layer of the first solar cell to the electrode of the second solar cell via at least a conductive adhesive member.

[14] The manufacturing method according to

[13] , wherein the joining step includes a thermocompression step of heating the first solar cell, the second solar cell, and the conductive adhesive member to 125°C or higher and applying a pressure of 0.1 MPa or higher for 3 minutes or longer.

[0154] INDUSTRIAL APPLICABILITY The solar cell module of the present invention can prevent an increase in electrical resistance in the junction regions between solar cell cells, and therefore has industrial applicability as a solar cell that can be used in a variety of environments.

[0155] DESCRIPTION OF SYMBOLS 1...Solar cell module, 100...Solar cell, 101...Conductive substrate, 1011...First surface, 1012...Second surface, 102...Hole transport layer, 103...Light absorption layer, 104...Electron transport layer, 105...Electrode layer, 106...Grid electrode, 107...Conductive corrosion prevention layer, 108...Contact resistance reducing layer, 109...Power generation element layer, 110...Electrode, 200...Conductive adhesive member

Claims

1. A first solar cell comprising at least, in this order, a conductive corrosion prevention layer, a first conductive substrate, a first power generation element layer, and a first electrode; a second solar cell comprising at least, in this order, a second conductive substrate, a second power generation element layer, and a second electrode; and the conductive corrosion prevention layer of the first solar cell and the second electrode of the second solar cell are joined at least via a conductive adhesive member. A solar cell module.

2. The solar cell module according to claim 1, wherein the first solar cell further has a contact resistance reduction layer between the conductive corrosion prevention layer and the conductive adhesive member.

3. The solar cell module according to claim 2, wherein the contact resistance reduction layer contains one or more selected from the group consisting of metallic silver, metallic tin, silver alloy, and tin alloy.

4. The difference in the linear expansion coefficients of the first conductive substrate and the conductive corrosion prevention layer at 500 °C is 5.0 × 10 －６ / °C or less. The solar cell module according to claim 1.

5. The solar cell module according to claim 1, wherein at least a part of the conductive corrosion prevention layer is sulfided, selenized, chlorinated, brominated, or iodized on the surface on the side of the conductive adhesive member.

6. The solar cell module according to claim 1, wherein the conductive corrosion prevention layer contains metal molybdenum or a molybdenum alloy.

7. The solar cell module according to claim 6, wherein the conductive corrosion prevention layer contains a molybdenum alloy, and the molybdenum alloy contains one or more selected from the group consisting of nickel element, niobium element, chromium element, tungsten element, silicon element, and carbon element.

8. The solar cell module according to claim 1, wherein the conductive adhesive member includes a conductive mesh fabric having a metal film.

9. A solar cell comprising at least, in this order, a conductive corrosion prevention layer, a conductive substrate, a power generation element layer, and an electrode.

10. The solar cell according to claim 9, further comprising a contact resistance reduction layer on the side of the conductive corrosion prevention layer opposite to the conductive substrate.

11. A laminate preparation step of preparing a laminate including at least a conductive corrosion prevention layer, a conductive substrate, and a precursor of a light absorption layer in this order; a heat treatment step of heat-treating the laminate in one or more atmospheres selected from the group consisting of a sulfur atmosphere, a selenium atmosphere, a chlorine atmosphere, a bromine atmosphere, and an iodine atmosphere; a power generation element layer formation step of forming a power generation element layer having the light absorption layer formed by the heat treatment step; and an electrode formation step of forming an electrode on the power generation element layer. A method for manufacturing a solar cell.

12. The manufacturing method according to claim 11, further including a contact resistance reduction layer formation step of forming a contact resistance reduction layer on the conductive corrosion prevention layer after the heat treatment step.

13. A method for manufacturing a solar cell module, including obtaining a first solar cell and a second solar cell by the manufacturing method according to claim 11, and a bonding step of bonding the conductive corrosion prevention layer of the first solar cell and the electrode of the second solar cell through at least a conductive bonding member.

14. The manufacturing method according to claim 13, wherein the bonding step includes a thermocompression bonding step of heating the first solar cell, the second solar cell, and the conductive bonding member at 125° C. or higher for 3 minutes or more and applying pressure of 0.1 MPa or higher.

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