Method for manufacturing solar cell, and solar cell

Abstract

Provided is a method for manufacturing a solar cell, the solar cell having high-performance designability. This method for manufacturing a solar cell includes: a step for forming, on a transparent electrode layer (106) on the light-receiving surface side of a solar cell (10), grid electrodes (107) containing silver; and a step for forming an oxide insulating film (108) on the surfaces of the transparent electrode layer (106) and the grid electrodes (107) by using a sputtering method while supplying a gas containing oxygen. In the step for forming the oxide insulating film (108), a silver oxide film (109) is formed between the grid electrodes (107) and the oxide insulating film (108), and the oxide insulating film (108) contains at least one chemical compound from among MgO and Al2O3.

Description

Solar cell manufacturing method and solar cell

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

[0002] Solar cells include silicon solar cells, which are manufactured using materials such as monocrystalline or polycrystalline silicon. While these solar cells are highly durable, they are expensive to manufacture and thick, making them suitable for use in large-scale power generation facilities. Thin-film solar cells are also available, which are solar cells formed by forming a thin, film-like light-absorbing layer on a substrate such as glass or metal. Thin-film solar cells are inexpensive to manufacture and are very thin, making them suitable for flexible use in electronic devices. Due to these characteristics, various studies have been conducted in recent years to improve the conversion efficiency and design of thin-film solar cells in order to further their applications.

[0003] Therefore, methods have been devised for blackening the color of electrodes of various electronic devices that require design by oxidizing their surfaces. For example, Patent Document 1 aims to provide a method for blackening mesh-like silver wiring formed on a substrate such as a glass substrate used in touch panels, etc., and proposes that a high-purity, uniform silver oxide film can be formed on the surface of the silver wiring by performing a first plasma treatment at high power and a second plasma treatment at low power on the surface of the silver wiring, thereby blackening the silver wiring.

[0004] Japanese Patent Application Laid-Open No. 2017-073001

[0005] In the solar cell field, there is also a demand for improved design of silver electrodes. However, in the method described in Patent Document 1, high-power and low-power plasma treatments are performed, followed by heating in air, which causes the oxidation reaction of silver to proceed, increasing the proportion of silver oxide in the silver electrode, reducing the conductivity of the electrode, and also causing moisture and oxygen in the air to diffuse into the solar cell, reducing its performance.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a solar cell that achieves both high performance and designability, and a solar cell.

[0007] A method for manufacturing a solar cell according to one embodiment of the present invention includes the steps of: forming a grid electrode containing silver on a transparent electrode layer on the light-receiving surface side of a solar cell; and forming an oxide insulating film on the surfaces of the transparent electrode layer and the grid electrode by a sputtering method while supplying a gas containing oxygen; and in the step of forming the oxide insulating film, a silver oxide film is formed between the grid electrode and the oxide insulating film.

[0008] In the manufacture of solar cells, a process for forming an oxide insulating film by sputtering while supplying a gas containing oxygen is included. A silver oxide film is formed between the grid electrode and the oxide insulating film, and the dark-colored silver oxide film improves the design of the solar cell, resulting in a solar cell that combines high performance with design.

[0009] A solar cell according to one embodiment of the present invention includes a transparent electrode layer disposed on a light-receiving surface side, a grid electrode containing silver disposed on the transparent electrode layer, an oxide insulating film covering the transparent electrode layer and the grid electrode, and a silver oxide film located between the grid electrode and the oxide insulating film.

[0010] In solar cells, the dark silver oxide film located between the grid electrode and the oxide insulating film improves the design of the solar cell, resulting in a solar cell that combines high performance with a stylish design.

[0011] According to the present invention, it is possible to provide a solar cell that combines high performance with designability, and a method for manufacturing the same.

[0012] 1 is a schematic cross-sectional view of a solar cell according to one embodiment of the present invention;

[0013] 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.

[0014] 1. Step of Forming an Oxide Insulating Film The manufacturing method for a solar cell according to this embodiment (hereinafter also referred to as "the manufacturing method") includes the steps of: forming a grid electrode containing silver on a transparent electrode layer on the light-receiving surface side of the solar cell; and forming an oxide insulating film on surfaces of the transparent electrode layer and the grid electrode by a sputtering method while supplying a gas containing oxygen, and in the step of forming the oxide insulating film, a silver oxide film is formed between the grid electrode and the oxide insulating film.

[0015] In recent years, there has been a demand for lightweight, flexible solar cell modules as power sources for mobile devices such as electric vehicles and electric aircraft, as well as for sensors and digital signage. For these applications, solar cells are more likely to be seen by users than conventional solar cells permanently installed outdoors, and therefore require improved design. While the power-generating side of a solar cell is typically dark blue or black, a silver-containing grid electrode is typically formed on the light-receiving side. Because the color and pattern of the grid electrode are conspicuous, it has been necessary to change the color to improve the design.

[0016] One method for changing the color of a silver-containing grid electrode is to darken it by oxidizing the silver, thereby improving its design. However, when conventional methods are used to oxidize electrodes used for external connection, the oxidation reaction can proceed excessively under high temperatures or high power, leading to problems such as reduced conductivity and performance. Therefore, the present inventors discovered that by forming a silver-containing grid electrode on a transparent electrode layer on the light-receiving side, and then forming an oxide insulating film by a sputtering method while supplying an oxygen-containing gas to the surface of the transparent electrode layer on which the grid electrode is formed, it is possible to achieve both high performance and design in a solar cell, even when used for a long period of time.

[0017] The reasons for the superiority of this method are thought to be as follows: When forming the oxide insulating film by sputtering while supplying an oxygen-containing gas, a silver oxide film is formed between the silver-containing grid electrode and the oxide insulating film without heating. Therefore, the silver oxide film can be formed and the grid electrode can be darkened while suppressing excessive oxidation reactions. Furthermore, the oxide insulating film is formed on the light-receiving surface side of the formed silver oxide film. This oxide insulating film can suppress the reflection of sunlight on the surface of the transparent electrode layer, improving the conversion efficiency of the solar cell and also suppressing moisture penetration from the outside, contributing to a longer lifespan of the solar cell. The synergistic effects of the formation of these films are thought to enable the resulting solar cell to achieve both high performance and design. However, the reasons are not limited to those mentioned above.

[0018] In this specification, "high performance solar cell" means that the solar cell has excellent cell characteristics related to the power generation performance of the solar cell in at least one parameter. "Designability of the solar cell" means that the aesthetic appearance of the solar cell has been improved, increasing its commercial value. "Darkening of the grid electrode" means that the color of the surface of the grid electrode has shifted to a lower brightness range.

[0019] An example of the cross-sectional structure of a solar cell obtained by the manufacturing method of this embodiment is shown in Figure 1. As shown in Figure 1, the solar cell 10 includes, for example, a substrate 101, a back electrode layer 102 provided on the substrate 101, a hole transport layer 103 provided on the back electrode layer 102, a light absorption layer 104 provided on the hole transport layer 103, an electron transport layer 105 provided on the light absorption layer 104, and a transparent electrode layer 106 provided on the electron transport layer 105. The solar cell obtained by the manufacturing method of this embodiment also includes a grid electrode 107 containing silver provided on the transparent electrode layer 106, and an oxide insulating film 108 covering the entire surface of the solar cell 10 except for the bottom surface, including the transparent electrode layer 106 and the grid electrode 107, and a silver oxide film 109 between the grid electrode 107 and the oxide insulating film 108. In this specification, the laminate obtained by forming from the substrate 101 to the transparent electrode layer 106 is also referred to as the "power generation section." In this embodiment, the solar cell includes the power generation section and is equipped with a grid electrode 107, an oxide insulating film 108, and a silver oxide film 109.

[0020] First, the step of forming an oxide insulating film will be described in detail below.

[0021] This manufacturing method includes a step of forming an oxide insulating film 108. In this step, the oxide insulating film 108 is formed on the surfaces of the transparent electrode layer 106 and the grid electrode 107 by sputtering while supplying an oxygen-containing gas, and at the same time, a silver oxide film 109 is also formed between the grid electrode 107 and the oxide insulating film 108. The formation of such oxide insulating film 108 and silver oxide film 109 provides the solar cell 10 with excellent performance and design. The formed silver oxide film 109 may cover the entire surface of the grid electrode 107, or may be formed only in a partial region between the grid electrode 107 and the oxide insulating film 108.

[0022] The step of forming the oxide insulating film is preferably performed in an atmosphere of 100°C or less, 80°C or less, 50°C or less, or room temperature. By performing the step of forming the oxide insulating film within the above temperature range, manufacturing costs can be reduced, and excessive formation of the silver oxide film 109 can be suppressed, which tends to improve design. The lower limit of the temperature is not particularly limited and is, for example, 0°C or more or 10°C or more. From the same viewpoint, the surface temperature of the substrate to be sputtered during sputtering is preferably 100°C or less, 80°C or less, 50°C or less, or room temperature. The lower limit of the temperature is not particularly limited and is, for example, 0°C or more or 10°C or more. Note that in this specification, the substrate to be sputtered refers to a substrate on a stage during sputtering, on which a compound derived from the sputtering target is deposited.

[0023] The target used for sputtering is not particularly limited as long as it can form the oxide insulating film 108. For example, Al ２ O ３ , MgO, SiO ２ , Y ２ O ３ Among these, from the viewpoint of more effectively and reliably exhibiting the effects of the present invention, Al ２ O ３ , MgO, and SiO ２ It is preferable that the compound is at least one of Al ２ O ３ and MgO, and Al ２ O ３ Or, more preferably, it is MgO.

[0024] The gas supplied during sputtering is oxygen (O ２ ), and further includes, for example, Ar, He, H ２ From the viewpoint of more effectively and reliably achieving the effects of the present invention, the gas contains at least one of oxygen (O ２ ) and Ar.

[0025] The oxygen content in the gas is preferably 5% by volume or more and 70% by volume or less, 10% by volume or more and 60% by volume or less, or 10% by volume or more and 50% by volume or less, relative to 100% by volume of the gas. Furthermore, the oxygen content is preferably 12% by volume or more and 70% by volume or less, 12% by volume or more and 60% by volume or less, or 12% by volume or more and 50% by volume or less. By keeping the oxygen content within the above ranges, the effects of the present invention tend to be more effectively and reliably achieved.

[0026] When sputtering is performed, the pressure of the oxygen-containing gas is preferably 0.1 Pa or more and 10 Pa or less, 0.1 Pa or more and 5 Pa or less, or 0.1 Pa or more and 2 Pa or less. By keeping the gas pressure within the above range, the effects of the present invention tend to be more effectively and reliably achieved.

[0027] The applied power during sputtering is preferably 1 W / cm ２ More than 15W / cm ２ less than 3 W / cm ２ More than 10W / cm ２ When the applied power is within the above range, the effects of the present invention tend to be more effective and reliable.

[0028] The steps of forming the substrate 101, the back electrode layer 102, the hole transport layer 103, the light absorption layer 104, the electron transport layer 105, the transparent electrode layer 106, and the grid electrode 107 will be described below in order.

[0029] 2. Solar Cell Manufacturing Method 2.1. Back Electrode Layer Forming Step In the step of forming the power generating portion of the solar cell, first, for example, the back electrode layer 102 is formed on the substrate 101. Methods for forming the back electrode layer 102 include dry processes and wet processes, with the dry process being preferred. The dry process is not particularly limited, and an example is a method for forming the back electrode layer 102, which is a metal conductive layer, by a sputtering method. The film formation conditions for the sputtering method are not particularly limited, and for example, applied power: 1.0 to 3.0 W / cm ２The film formation atmosphere may be an argon atmosphere, and the film formation pressure may be 0.5 to 3.0 Pa. In the back electrode layer forming step, for example, the substrate 101 may be the substrate to be sputtered.

[0030] 2.2. Hole Transport Layer Formation Step Next, for example, the hole transport layer 103 is formed on the back electrode layer 102. Methods for forming the hole transport layer 103 include a dry process and a wet process, but a dry process is preferred. The dry process is not particularly limited, and an example is a method for forming the hole transport layer 103, which is a p-type semiconductor containing an organic compound or an inorganic compound, by a sputtering method. The film formation conditions for the sputtering method are not particularly limited, and an example is an applied power of 0.5 to 3.0 W / cm. ２ The film formation atmosphere may be an argon atmosphere or a mixed atmosphere of argon and oxygen, and the film formation pressure may be 0.5 to 3.0 Pa. When forming the light absorbing layer 104, a compound may be formed between the back electrode layer 102 and the light absorbing layer 104 by forming a compound of an element of the back electrode layer 102 and an element contained in the light absorbing layer 104.

[0031] 2.3. Light-Absorbing Layer Forming Step Next, the light-absorbing layer 104 is formed on the hole-transporting layer 103. For example, methods for forming the light-absorbing layer 104 include a dry process and a wet process, with the dry process being preferred. The dry process is not particularly limited, but an example is a method for forming the light-absorbing layer 104 containing a chalcopyrite compound or a kesterite compound by a sputtering method. The film-forming conditions for the sputtering method are not particularly limited, but for example, applied power: 0.5 to 3.0 W / cm ２ The deposition atmosphere may be an argon atmosphere, and the deposition pressure may be 0.5 to 3.0 Pa. The temperature of the atmosphere and the temperature of the substrate to be sputtered may not be controlled during sputtering. After sputtering, annealing may be performed at 350° C. or higher and 650° C. or lower in a nitrogen or selenium and sulfur atmosphere.

[0032] 2.4. Electron Transport Layer Formation Step Next, the electron transport layer 105 is formed on the light absorbing layer 104. For example, the electron transport layer 105 may be formed on the sputtered substrate including the light absorbing layer 104 by depositing an n-type oxide semiconductor by sputtering while supplying a gas containing an oxygen source and a hydrogen source, or the n-type oxide semiconductor may be deposited by sputtering while supplying a gas not containing a hydrogen source. The deposition conditions for the sputtering method are not particularly limited, and examples thereof include applied power of 0.5 to 3.0 W / cm. ２ The film formation atmosphere may be an argon atmosphere which may contain oxygen, and the film formation pressure may be 0.5 to 3.0 Pa. It is also preferable to heat the substrate to be sputtered during sputtering.

[0033] 2.5. Transparent Electrode Layer Formation Step Next, the transparent electrode layer 106 is formed on the electron transport layer 105. Methods for forming the transparent electrode layer 106 include dry processes and wet processes, with the dry process being preferred. The dry process is not particularly limited, and an example is a method for forming the transparent electrode layer 106 by a sputtering method. The film formation conditions for the sputtering method are not particularly limited, and an example is an applied power of 0.5 to 3.0 W / cm. ２ The film formation atmosphere may be an argon atmosphere or a mixed atmosphere of argon, oxygen, and hydrogen. The film formation pressure may be 0.5 to 3.0 Pa.

[0034] 2.6 Grid Electrode Formation Step This manufacturing method includes a step of forming the grid electrode 107. In this step, the grid electrode 107 containing silver is formed on the transparent electrode layer 106 on the light-receiving surface side of the solar cell. The method for forming the grid electrode 107 is not particularly limited, and examples thereof include a dry process and a wet process. Specific examples include sputtering, vapor deposition, a method of printing a paste-like conductive material on the transparent electrode layer, and a method of crimping a wire.

[0035] 2.7. Oxide insulating film forming step Next, the oxide insulating film 108 is formed on the transparent electrode layer 106 and the grid electrode 107, and at this time, the silver oxide film 109 is also formed. The formation of the oxide insulating film 108 is as described above in "1. Step of forming an oxide insulating film."

[0036] 2.8. Encapsulating Step The present manufacturing method may include a step of covering the laminate including the power generation section with a sealing material. For example, as shown in FIG. 2, the solar cells stacked as described above are further covered with a sealing material 201 to obtain a solar cell 20. Including a sealing step tends to suppress performance degradation of the solar cell due to external impact, moisture, and the like.

[0037] 3. Solar Cell The solar cell 10 of this embodiment includes a transparent electrode layer 106 disposed on the light-receiving surface side, a grid electrode 107 containing silver disposed on the transparent electrode layer 106, an oxide insulating film 108 covering the transparent electrode layer 106 and the grid electrode 107, and a silver oxide film 109 positioned between the grid electrode 107 and the oxide insulating film 108. By configuring the solar cell 10 in this manner, it is possible to achieve high performance and a stylish design. Below, as an example of the basic configuration of the power generation section, the components from the substrate 101 to the transparent electrode layer 106 will be described, and then the grid electrode 107, the oxide insulating film 108, the silver oxide film 109, and the like of this embodiment will be described in detail.

[0038] 3.1. Substrate The substrate 101 is not particularly limited, and examples thereof include glass substrates such as soda lime glass and low-alkali glass, metal substrates such as stainless steel foil, aluminum foil, and titanium foil, and resin substrates such as polyimide resin films and epoxy resin films. The thickness of the substrate 101 is not particularly limited, and is, for example, 10 μm to 500 μm, 20 μm to 250 μm, or 30 μm to 100 μm. A thickness of the substrate 101 within the above range is preferable in that it allows for lighter and more flexible solar cells.

[0039] 3.2. Back Electrode Layer The back electrode layer 102 is generally provided to extract current due to holes generated in the light absorption layer 104 described below. The back electrode layer 102 is not particularly limited as long as it is conductive, and examples thereof include a metal conductive layer made of a metal such as Mo, Cr, or Ti; a conductive inorganic compound conductive layer made of a conductive inorganic compound other than a metal; and a conductive organic compound conductive layer made of a conductive organic compound. The thickness of the back electrode layer 102 is not particularly limited and is, for example, 200 nm to 800 nm, or 300 nm to 700 nm. A thickness of the back electrode layer 102 within the above range is preferable in that it allows sufficient current to be extracted without loss while enabling the solar cell to be lightweight and flexible.

[0040] 3.3 Hole Transport Layer The hole transport layer 103 has a function of, for example, efficiently extracting holes generated in the light absorption layer 104 (described later) from the light absorption layer 104 and preventing recombination of electrons and holes generated simultaneously with the electron-hole generation in the light absorption layer 104 (described later). The hole transport layer 103 is preferably a p-type semiconductor. The substance contained in the p-type semiconductor is not particularly limited, and examples thereof include organic compounds such as polythiophene derivatives such as poly(3,4-ethylene-dioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly(3-hexylthiophene) (P3HT), and poly(3-octylthiophene) (P3OT); fluorene derivatives such as 2,2'-7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeO-TAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives; diphenylamine derivatives; polysilane derivatives; and polyaniline derivatives; as well as inorganic compounds such as nickel oxide, molybdenum oxide, gallium copper oxide, aluminum copper oxide, molybdenum selenide, and molybdenum sulfide selenide. The p-type semiconductor in the hole transport layer 103 may be used alone or in combination of two or more types. In the solar cell, the formation of the hole transport layer 103 may be omitted.

[0041] 3.4. Light-Absorbing Layer The light-absorbing layer 104 has the function of absorbing light such as near-infrared light, visible light, and ultraviolet light to generate electrons and holes. Examples of such light include sunlight. Examples of compounds that constitute the light-absorbing layer 104 include compounds containing perovskite compounds, chalcopyrite compounds, and kesterite compounds. Each compound may be used alone, or two or more types of perovskite, chalcopyrite, or kesterite may be used in combination.

[0042] 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 , AgAlTe ２ , 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.

[0043] 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 , Cu ２ 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 ２MnGeS 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(S ｙ 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.

[0044] Examples of perovskite compounds include organic-inorganic perovskite compounds, particularly halide-based organic-inorganic perovskite compounds. 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 NH ３ 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.

[0045] The contents of the chalcopyrite compound, kesterite compound, and perovskite compound in the light-absorbing layer 104 are not particularly limited as long as the light-absorbing layer 104 has the function of absorbing light such as visible light and ultraviolet light to generate electrons and holes. More specifically, although not particularly limited, the contents of the compounds are, relative to the total mass of the light-absorbing layer 104, 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.

[0046] The band gap of the light absorbing layer 104 is preferably 2.0 eV or less, 1.8 eV or less, 1.5 eV or less, 1.2 eV or less, or 1.1 eV or less, based on the minimum value in the depth direction. The lower limit of the band gap may be, for example, 0.5 eV or 0.8 eV or more. When the band gap of the light absorbing layer 104 satisfies the above range, the solar cell exhibits high performance.

[0047] The thickness of each light absorbing layer 104 is preferably 0.5 μm to 5 μm, 0.8 μm to 4 μm, or 1 μm to 3 μm. By setting the thickness of each light absorbing layer 104 within the above ranges, productivity of the solar cell tends to be further improved and it becomes easier to make the solar cell lighter and more flexible.

[0048] 3.5. Electron Transport Layer The electron transport layer 105 has a function of, for example, efficiently extracting electrons generated in the light absorption layer 104 from the light absorption layer 104 and preventing recombination of electrons and holes generated simultaneously in the light absorption layer 104. The electron transport layer 105 is preferably an n-type semiconductor. The material contained in the n-type semiconductor is not particularly limited, and may be, for example, C ６０ Examples of n-type semiconductors include organic compounds such as phenanthroline derivatives such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), phenylpyridine derivatives such as 4,6-bis(3,5-di-4-pyridinylphenyl)-2-methylpyrimidine (B4PymPm) and tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB), n-type oxide semiconductors consisting essentially of zinc oxide, tin oxide, titanium oxide, zinc sulfide oxide, magnesium zinc oxide, zinc tin oxide, or zinc titanium oxide, and n-type semiconductors containing cadmium sulfide, indium sulfide, or indium sulfide doped with oxygen or an alkali metal element. The n-type semiconductors in the electron transport layer 105 may be used singly or in combination of two or more. The thickness of the electron transport layer 105 is, for example, 50 nm to 200 nm, 60 nm to 150 nm, or 75 nm to 135 nm. The thickness of the electron transport layer 105 within the above range is preferable in that the solar cell can be made lighter and more flexible while retaining the above functions.

[0049] 3.6. Transparent Electrode Layer The transparent electrode layer 106 is provided, for example, to extract current due to electrons generated in the light absorbing layer 104. In solar cells, the light absorbing layer 104 typically absorbs light that passes through the transparent electrode layer 106. To increase the amount of light absorbed by the light absorbing layer 104, this layer is made into a transparent electrode layer. Known materials can be used for the transparent electrode, such as 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). The thickness of the transparent electrode layer 106 is not particularly limited and is, for example, 100 nm to 1500 nm, or 200 nm to 1000 nm. Setting the thickness of the transparent electrode layer 106 within the above range is preferable because it allows sufficient current to be extracted without loss while also enabling the solar cell to be lightweight and flexible.

[0050] 3.7 Grid Electrode The grid electrode 107 is provided, for example, to extract electricity from the transparent electrode layer 106. The solar cell 10 uses a material containing silver (Ag) as the grid electrode 107. Materials other than silver (Ag) that may be contained therein are not particularly limited as long as they are conductive, and examples that can be used include metals such as Mo, Cr, Cu, Ni, Al, and Ti; conductive inorganic compounds other than metals; and conductive organic compounds.

[0051] The silver content in the grid electrode 107 is preferably 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, relative to 100% by mass of the grid electrode. By keeping the silver content within the above range, the effects of the present invention tend to be more effectively and reliably achieved.

[0052] The width of the grid electrode 107 is preferably 10 μm to 100 μm, 20 μm to 80 μm, or 30 μm to 60 μm. By setting the width of the grid electrode 107 within the above range, the effects of the present invention tend to be more effective and reliable. The "width" of the grid electrode 107 refers to the width of one grid electrode at the contact surface between the transparent electrode layer 106 and the grid electrode 107. The thickness of the grid electrode 107 is preferably 1 μm to 100 μm, 3 μm to 80 μm, or 5 μm to 50 μm. By setting the thickness of the grid electrode 107 within the above range, the effects of the present invention tend to be more effective and reliable.

[0053] 3.8. Oxide insulating film In the solar cell 10 of this embodiment, the oxide insulating film 108 covers the transparent electrode layer 106 and the grid electrode 107, and may also cover the side surface of the power generation section. The oxide insulating film 108 is not particularly limited as long as it is an oxide and a transparent material having insulating properties. Examples of compounds that constitute such an oxide insulating film 108 include Al, ２ O ３ , MgO, SiO ２ , Y ２ O ３ Among these, Al is preferred as the oxide insulating film 108. ２ O ３ , MgO, and SiO ２ From the viewpoint of anti-reflection, it is preferable to use at least one of Al ２ O ３ and MgO are preferably used. From the viewpoint of anti-reflection and weather resistance, Al ２ O ３ By using the above-mentioned materials for the oxide insulating film 108, the solar cell 10 tends to have higher performance.

[0054] The refractive index of the oxide insulating film 108 is preferably 1.5 to 2.0, or 1.6 to 1.8. By setting the refractive index of the oxide insulating film 108 within the above range, the oxide insulating film 108 functions as an anti-reflection film for the transparent electrode layer 106, reducing surface reflection of sunlight and improving the performance of the solar cell.

[0055] The thickness of the oxide insulating film 108 is preferably 10 nm to 300 nm, 20 nm to 150 nm, 30 nm to 100 nm, or 50 nm to 90 nm. When the thickness of the oxide insulating film 108 is within the above range, the oxide insulating film can function as a moisture barrier film, thereby suppressing moisture penetration into the solar cell and extending the lifetime of the solar cell.

[0056] 3.9. Silver Oxide Film The silver oxide film 109 is formed mainly as a result of oxidation of silver contained in the grid electrode 107, and is located between the grid electrode 107 and the oxide insulating film .

[0057] The silver oxide film 109 gives the solar cell 10 an excellent design. When the silver oxide film 109 is formed, the grid electrode 107 basically exhibits a dark or black color, and when only a small amount of the silver oxide film 109 is formed, the grid electrode 107 exhibits a color that is an intermediate stage of blackening, such as gray or light black. From the viewpoint of more effectively and reliably achieving the effect of improving the design, the grid electrode 107 and the solar cell 10 having the silver oxide film 109 preferably exhibit a dark or black color.

[0058] The ratio of the thickness of the silver oxide film 109 to the width of the grid electrode 107 is preferably 0.0006 to 0.02, 0.0008 to 0.015, or 0.001 to 0.01. By including the silver oxide film 109 at such a ratio, the grid electrode can be darkened while suppressing a decrease in the electrical resistance of the grid electrode. From the same viewpoint, the thickness of the silver oxide film 109 is preferably 30 to 1000 nm, 40 to 750 nm, or 50 to 500 nm.

[0059] 3.10. Modifications Solar cell 10 shown in FIG. 1 is an example for explaining the solar cell of the present invention, and is not intended to limit the present invention to only this embodiment. The solar cell of the present invention can be modified in various ways without departing from the gist of the invention.

[0060] For example, as shown in FIG. 2 , the solar cells stacked as described above may be further covered with a sealing material 201 to form a solar cell 20. Including a sealing process tends to suppress performance degradation of the solar cells due to external impacts, moisture, and the like. Examples of sealing materials that can be used include light-transmitting materials such as ethylene vinyl acetate (EVA), ethylene / vinyl acetate / triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), urethane, and acrylic. Ethylene vinyl acetate (EVA) is preferred from the viewpoint of more effectively and reliably achieving the effects of the present invention. Furthermore, for the purpose of improving the durability of the solar cell module, the light-receiving surface side of the solar cell 20 sealed with the sealing material 201 may be attached to a front sheet and the substrate side to a back sheet.

[0061] The solar cell 10 may have other layers between the layers, on the grid electrode 107, or under the substrate 101, as needed. Specifically, the hole transport layer 103 may have two or more hole transport layers each containing a different material. Alternatively, instead of the grid electrode 107, another hole transport layer may be provided on the transparent electrode layer 106, with an additional light absorbing layer thereon. Alternatively, the electron transport layer 105 may have two or more electron transport layers 105 each containing a different material.

[0062] Although not shown, the solar cell 10 may have two or three sets of a hole transport layer 103, a light absorbing layer 104 provided on the hole transport layer 103, an electron transport layer 105 provided on the light absorbing layer, and a transparent electrode layer 106 provided on the electron transport layer 105, stacked on the back electrode layer 102. A grid electrode may be provided on the uppermost transparent electrode layer of such a stack.

[0063] When a plurality of layers 101 to 106 are present, the plurality of layers may be the same or different. For example, when a plurality of light-absorbing layers 104 are provided, each light-absorbing layer may contain a compound with a different absorption spectrum, and the electron transport layer and hole transport layer in contact with each light-absorbing layer may be selected according to the properties of the light-absorbing layer in contact with the layer. However, such a power-generating section has the oxide insulating film 108 and silver oxide film 109 of the present invention on the light-receiving surface side.

[0064] Like conventional solar cells, the solar cell of this embodiment can be used in normal temperature environments where the temperature of the solar cell is about 45 to 85° C. For example, it can be suitably used as a power generation device attached to the windows or walls of buildings or vehicles, as an independent power source device for street lights or sensors, as a mobile energy device, and as a power generation device in space or the stratosphere.

[0065] The solar cell of this embodiment has a high conversion efficiency. More specifically, the conversion efficiency of the solar cell of this embodiment is preferably 14% or more, 15% or more, or 16% or more. A conversion efficiency in the above range indicates that a high-performance solar cell has been obtained.

[0066] The thickness of the solar cell 10 excluding the substrate 101 is not particularly limited and is, for example, 1 μm to 40.0 μm, 2 μm to 30 μm, or 3 μm to 20 μm. The solar cell of the present invention can be a thin-film solar cell by forming each layer to be sufficiently thin.

[0067] 4. Electrode Darkening Method The oxide insulating film forming process of this embodiment can be applied to various devices other than the solar cell 10 for the purpose of darkening and protecting electrodes containing silver, and is particularly useful for processing at low power and low temperature. For example, it can be applied to electrode wiring of a light-emitting device such as a display device.

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0069] <Method of Fabricating Solar Cell> A solar cell having a single electron transport layer, as shown in Figure 1, was fabricated. A 50 μm-thick titanium foil was used as the substrate. A 600 nm-thick back electrode layer containing metallic molybdenum was formed on this substrate by sputtering. Next, a 2 μm-thick light-absorbing layer containing a CIGSS compound was formed on the back electrode layer by sputtering. When forming the light-absorbing layer, a 50 nm-thick MoSe layer, which served as a hole transport layer, was also formed between the light-absorbing layer and the back electrode layer. Furthermore, the resulting light-absorbing layer was surface-treated by annealing it in a sulfur atmosphere at 500°C to 600°C for 3 to 30 minutes.

[0070] Next, an n-type electron transport layer containing titanium zinc oxide doped with hydrogen and sulfur was formed on the light absorption layer by a sputtering method to a thickness of 70 nm to 120 nm. A transparent electrode layer of hydrogen-containing indium oxide was formed on the n-type electron transport layer to a thickness of 300 nm, and a silver grid electrode having a width of 50 μm was formed on the surface of the transparent electrode layer.

[0071] In the following examples and comparative examples, solar cells were fabricated and evaluated in the same manner as described above, except for the step of forming the oxide insulating film described below.

[0072] 1. Formation of Silver Oxide Film and Oxide Insulating Film 1.1. Step of Forming Oxide Insulating Film On the light-receiving surface side of the laminate obtained above, Al was deposited as an oxide insulating film by sputtering, with the oxygen concentration being changed from 0% to 80% with respect to 100% by volume of the gas to be introduced in each example. ２ O ３ In the example where an MgO layer was formed, the oxygen concentration was set to 0% and 10% relative to 100% by volume of the gas to be introduced (Table 2). ２ O ３ Sputtering was performed under the following conditions, except that the oxygen concentration was changed when forming the AlN layer and the MgO layer. <Sputtering film formation conditions> Applied power: 5 to 9 W / cm 2 Film formation atmosphere (gas): oxygen (O ２ ), argon (Ar) Pressure during film formation: 0.1 Pa or more and 0.5 Pa or less Substrate temperature: room temperature Target species: Al ２O ３ When forming the layer, Al ２ O ３ MgO alone when forming the MgO layer

[0073] 1.2. Evaluation: Rate of change in conversion efficiency Using the solar cell with the silver grid electrode formed as described above and the solar cell of each example with the oxide insulating film formed, the IV curve was measured under standard test conditions (light with a spectral spectrum of AM1.5 and an irradiance of 1 kW / m ２ The measurements were taken under test conditions where light was incident at 1000kJ / cm2 and the solar cell temperature was 25°C. The conversion efficiency of each solar cell was calculated using the following formula. The conversion efficiency (%) is the value obtained by dividing the output at the optimum operating point in the IV curve (maximum output: Pmax) by the light energy E received by the solar cell. The rate of change (%) in the conversion efficiency of the solar cell of each example relative to the conversion efficiency of a solar cell without an oxide insulating film was calculated and is shown in Tables 1 and 2. Conversion efficiency (%) = (Pmax / E) x 100

[0074]

[0075]

[0076] 2. Refractive index of oxide insulating film The laminate of the solar cell obtained above is added with Al as an oxide insulating film. ２ O ３ layer or SiO ２ Numerical simulations were performed assuming that after the layer was formed, the entire solar cell was further sealed with a sealing material to investigate the relationship between conversion efficiency and the film thickness of the oxide insulating film. The simulations were performed using "Thin-film solar cell characteristic simulation software (e-ARC)" published by the National Institute of Advanced Industrial Science and Technology. The conditions are shown below. The conversion efficiency of each example obtained by simulation was calculated as a rate of change relative to the conversion efficiency when sealing was performed with a sealing material without forming an oxide insulating film (Comparative Example 3 and Comparative Example 4) (Tables 3 and 4). <Simulation conditions> Spectral spectrum: AM1.5 Irradiance: 1 kW / m ２ Solar cell temperature: 25°C Sealant: refractive index 1.5, thickness 0.2 mm

[0077]

[0078] <Notes> The embodiments of the present disclosure include the following: [1] A method for manufacturing a solar cell, comprising: forming a grid electrode containing silver on a transparent electrode layer on a light-receiving surface side of the solar cell; and forming an oxide insulating film on the surface of the transparent electrode layer and the grid electrode by a sputtering method while supplying a gas containing oxygen, wherein in the oxide insulating film forming step, a silver oxide film is formed between the grid electrode and the oxide insulating film, and the oxide insulating film contains MgO and Al ２ O ３ [2] The method for manufacturing a solar cell according to [1], wherein the oxygen content is 10% by volume or more and 60% by volume or less relative to 100% by volume of the oxygen-containing gas. [3] The method for manufacturing a solar cell according to [1] or [2], wherein the step of forming the oxide insulating film is carried out at a temperature of 80° C. or less. [4] The method for manufacturing a solar cell according to [1] or [2], wherein the solar cell comprises: a transparent electrode layer disposed on a light-receiving surface side; a grid electrode containing silver disposed on the transparent electrode layer; an oxide insulating film covering the transparent electrode layer and the grid electrode; and a silver oxide film located between the grid electrode and the oxide insulating film, wherein the oxide insulating film contains MgO and Al ２ O ３ [5] The solar cell according to [4], wherein the ratio of the thickness of the silver oxide film to the width of the grid electrode is 0.001 or more and 0.01 or less. [6] The solar cell according to [4] or [5], wherein the refractive index of the oxide insulating film is 1.5 or more and 2.0 or less. [7] The solar cell according to any one of [4] to [6], wherein the thickness of the oxide insulating film is 50 nm or more and 90 nm or less. [8] The solar cell according to any one of [4] to [7], further comprising an encapsulant.

[0079] 10, 20... solar cell, 101... substrate, 102... back electrode layer, 103... hole transport layer, 104... light absorption layer, 105... electron transport layer, 106... transparent electrode layer, 107... grid electrode, 108... oxide insulating film, 109... silver oxide film, 201... sealing material

Claims

1. A step of forming a grid electrode containing silver on a transparent electrode layer on a light-receiving surface side of a solar cell, and a step of forming an oxide insulating film by a sputtering method while supplying a gas containing oxygen to surfaces of the transparent electrode layer and the grid electrode, and in the step of forming the oxide insulating film, a silver oxide film is formed between the grid electrode and the oxide insulating film, and the oxide insulating film contains at least one of MgO and Al ２ O ３ A method for manufacturing a solar cell.

2. The manufacturing method of the solar cell according to claim 1, wherein the oxygen content is 10% by volume or more and 60% by volume or less with respect to 100% by volume of the gas containing the oxygen.

3. The manufacturing method of the solar cell according to claim 1, wherein the step of forming the oxide insulating film is performed at a temperature of 80°C or lower.

4. A transparent electrode layer disposed on the light-receiving surface side, a grid electrode containing silver disposed on the transparent electrode layer, an oxide insulating film covering the transparent electrode layer and the grid electrode, and a silver oxide film positioned between the grid electrode and the oxide insulating film, wherein the oxide insulating film contains at least one of MgO and Al ２ O ３ and is a solar cell.

5. The solar cell according to claim 4, wherein the ratio of the thickness of the silver oxide film to the width of the grid electrode is 0.001 or more and 0.01 or less.

6. The solar cell according to claim 4, wherein the refractive index of the oxide insulating film is 1.5 or more and 2.0 or less.

7. The solar cell according to claim 4, wherein the thickness of the oxide insulating film is 50 nm or more and 90 nm or less.

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