Method for manufacturing solar cell, and solar cell

Abstract

To provide a method for manufacturing a solar cell, the solar cell having high-performance designability.SOLUTION: The method for manufacturing the solar cell includes: forming, on a transparent electrode layer on the light-receiving surface side of a solar cell, grid electrodes containing silver; and forming an oxide insulating film on the surfaces of the transparent electrode layer and the grid electrodes by using a sputtering method while supplying a gas containing oxygen. In the step of forming the oxide insulating film, a silver oxide film is formed between the grid electrodes and the oxide insulating film.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] As solar cells, there are silicon solar cells manufactured using materials such as single-crystalline and polycrystalline silicon. While they have excellent durability, they have high manufacturing costs and are thick, so they are used in large-scale power generation facilities. There are also thin-film solar cells in which a thin film-like light absorption layer is formed on a substrate such as glass or metal to form a solar cell. Thin-film solar cells have low manufacturing costs and are very thin, so they can also be used in electronic devices and the like in a flexible manner. Due to such characteristics, in recent years, various studies have been conducted on conversion efficiency, designability, etc. for the application of thin-film solar cells.

[0003] Therefore, a method has been devised in which the surface of an electrode of various electronic devices that require designability is oxidized to blacken the color. For example, in Patent Document 1, for the purpose of providing a method for blackening a mesh-shaped silver wiring formed on a base material such as a glass substrate used in a touch panel or the like, a step of performing a first plasma treatment on the surface of the silver wiring at a high output and a step of performing a second plasma treatment at a low output are performed, and it is proposed that a high-purity and uniform silver oxide film can be formed on the surface of the silver wiring to blacken the silver wiring.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the field of solar cells, there is also a demand for improving the designability of silver electrodes. However, in the method as described in Patent Document 1, since high-output and low-output plasma treatments are respectively performed and then heating is further performed in the air, the oxidation reaction of silver proceeds, the proportion of silver oxide in the silver electrode increases, and the conductivity of the electrode decreases. Or, there is a problem that moisture and oxygen in the air diffuse into the solar cell and the performance deteriorates.

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

Means for Solving the Problems

[0007] A method for manufacturing a solar cell according to an embodiment of the present invention includes a step of forming a grid electrode containing silver on a transparent electrode layer on the light-receiving surface side of the solar cell, and a step of 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. 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 a solar cell, by including a step of forming an oxide insulating film by a sputtering method while supplying a gas containing oxygen and forming a silver oxide film between the grid electrode and the oxide insulating film, the designability of the solar cell is improved by the dark-colored silver oxide film, and a solar cell that achieves both high performance and designability can be obtained.

[0009] A solar cell according to an embodiment of the present invention includes 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.

[0010] In a solar cell, the designability of the solar cell is improved by a dark-colored silver oxide film positioned between the grid electrode and the oxide insulating film, and the solar cell achieves both high performance and designability.

Advantages of the Invention

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

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments 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 thereto, and various modifications are possible without departing from the gist thereof. In the drawings, the same reference numerals are assigned to the same elements, and redundant descriptions are omitted. Also, the 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 in the drawings are not limited to the illustrated ratios.

[0014] 1. Step of forming an oxide insulating film The method for manufacturing a solar cell according to the present embodiment (hereinafter also referred to as "the present manufacturing method") includes a step of forming a grid electrode containing silver on a transparent electrode layer on the light-receiving surface side of the solar cell, and a step of forming an oxide insulating film by a sputtering method while supplying a gas containing oxygen to the surfaces of the transparent electrode layer and the grid electrode. 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, lightweight flexible solar cell modules have been demanded as power sources for moving objects such as electric vehicles and electric aircraft, as well as power sources for sensors and digital signage. In such applications, compared with conventional solar cells installed outdoors permanently, there are more opportunities to catch the user's eye, so further designability is required. By the way, while the power generation part side of the solar cell is dark blue or black, generally, a grid electrode containing silver is often formed and used on the light receiving surface side, and the color and formation pattern of the grid electrode are conspicuous. Therefore, it has been necessary to change the color to improve the designability.

[0016] As a method of changing the color of the grid electrode containing silver, it is conceivable to darken it by oxidizing silver to improve the designability. However, when an oxidation reaction is performed on the electrode used for connection to the outside by a conventional method, there is a problem that the oxidation reaction proceeds excessively due to the process being carried out under high temperature or high output, leading to a decrease in conductivity and performance. Therefore, the inventors of the present application have found that, after forming a grid electrode containing silver on the transparent electrode layer on the light receiving surface side, while supplying a gas containing oxygen to the surface of the transparent electrode layer on which the grid electrode is formed, an oxide insulating film is formed by a sputtering method, so that even when used for a long time, high performance and designability of the solar cell can be achieved simultaneously.

[0017] Regarding the reasons why this method is excellent, the following can be considered. When forming an oxide insulating film while supplying a gas containing oxygen by a sputtering method, a silver oxide film is formed between the grid electrode containing silver and the oxide insulating film without heating. Therefore, it is possible to form a silver oxide film while suppressing an excessive oxidation reaction and darken the grid electrode. Further, an oxide insulating film is formed on the light-receiving surface side of the formed silver oxide film, and since the oxide insulating film can suppress the reflection of sunlight on the surface of the transparent electrode layer, the conversion efficiency of the solar cell is improved, and it also plays a role in suppressing the intrusion of moisture from the outside, contributing to the long life of the solar cell. As a result of the synergistic action of the effects of forming these films, it is considered that the high performance and designability of the obtained solar cell can be achieved at the same time. However, the reasons are not limited to the above.

[0018] In addition, in this specification, "the solar cell is high-performance" means that the cell characteristics related to the power generation performance of the solar cell are excellent in at least one parameter. Also, "the solar cell has designability" means that the aesthetic appearance of the solar cell is improved and the commercial value is enhanced. Further, "darkening of the grid electrode" means that the color of the surface of the grid electrode shifts to a system with a lower brightness.

[0019] FIG. 1 shows an example of the cross-sectional structure of a solar cell obtained by the manufacturing method of the present embodiment. As shown in FIG. 1, for example, the solar cell 10 includes 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. Further, the solar cell obtained by the manufacturing method of the present embodiment includes a grid electrode 107 containing silver provided on the transparent electrode layer 106, and an oxide insulating film 108 that entirely covers the surfaces of the solar cell 10 other than the bottom surface including the transparent electrode layer 106 and the grid electrode 107, and an silver oxide film 109 is provided 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 a "power generation part". In the present embodiment, the solar cell includes the power generation part and includes the grid electrode 107, the oxide insulating film 108, and the silver oxide film 109.

[0020] Hereinafter, the process of forming the oxide insulating film will be described in detail first.

[0021] This manufacturing method includes a step of forming the oxide insulating film 108. In this step, the oxide insulating film 108 is formed by a sputtering method while supplying a gas containing oxygen to the surfaces of the transparent electrode layer 106 and the grid electrode 107. At this time, the silver oxide film 109 is also formed between the grid electrode 107 and the oxide insulating film 108. By forming such an oxide insulating film 108 and silver oxide film 109, the solar cell 10 becomes excellent in high performance and design. Note that the formed silver oxide film 109 may entirely cover the surface of the grid electrode 107, or may be formed 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 carried out in an atmosphere at 100°C or lower, 80°C or lower, 50°C or lower, or at room temperature. By carrying out the step of forming the oxide insulating film within the above temperature range, the cost in manufacturing can be suppressed, excessive formation of the silver oxide film 109 can be suppressed, and the design property tends to be improved. The lower limit of the above temperature is not particularly limited, and is, for example, 0°C or higher, 10°C or higher. Also, from the same viewpoint, when performing sputtering, the surface temperature of the substrate to be sputtered is preferably 100°C or lower, 80°C or lower, 50°C or lower, or at room temperature. The lower limit of the above temperature is not particularly limited, and is, for example, 0°C or higher, 10°C or higher. In this specification, the substrate to be sputtered is a substrate on the stage when performing sputtering, and is a substrate on which a compound derived from the sputtering target is laminated.

[0023] The target used for sputtering is not particularly limited as long as it can form the oxide insulating film 108, and examples include single substances or mixtures of Al2O3, MgO, SiO2, Y2O3, and single substances or mixtures of Al, Mg, and Si. Among these, from the viewpoint of more effectively and surely achieving the effects of the present invention, it is preferably at least one of Al2O3, MgO, and SiO2, more preferably at least one of Al2O3 and MgO, and even more preferably Al2O3 or MgO.

[0024] The gas supplied when performing sputtering contains oxygen (O2), and further contains, for example, at least one of Ar, He, and H2. From the viewpoint of more effectively and surely achieving the effects of the present invention, it is preferable that the gas contains oxygen (O2) and Ar.

[0025] The oxygen content in the gas is preferably 5 volume% or more and 70 volume% or less, 10 volume% or more and 60 volume% or less, 10 volume% or more and 50 volume% or less with respect to 100 volume% of the gas. By setting the oxygen content within the above range, the effects of the present invention tend to be more effectively and surely achieved.

[0026] When performing sputtering, the pressure of the gas containing oxygen 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 setting the gas pressure within the above range, the effects according to the present invention tend to be more effectively and surely exhibited.

[0027] The applied power during sputtering is preferably 1 W / cm 2 or more and 15 W / cm 2 or less, and 3 W / cm 2 or more and 10 W / cm 2 or less. When the applied power is within the above range, the effects according to the present invention tend to be more effectively and surely exhibited.

[0028] Hereinafter, 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 in order.

[0029] 2. Method for manufacturing a solar cell 2.1. Back electrode layer formation step As a step of forming the power generation part of the solar cell, first, for example, the back electrode layer 102 is formed on the substrate 101. Examples of the method for forming the back electrode layer 102 include a dry process and a wet process, and the dry process is preferred. The dry process is not particularly limited, and for example, a method of forming the back electrode layer 102, which is a metal conductive layer, by a sputtering method can be mentioned. The film formation conditions of the sputtering method are not particularly limited, and for example, the applied power: 1.0 to 3.0 W / cm 2 , the film formation atmosphere: argon atmosphere, and the film formation pressure: 0.5 to 3.0 Pa may be used. In the back electrode layer formation step, for example, the substrate 101 may be used as the substrate to be sputtered.

[0030] 2.2. Hole transport layer formation step Next, for example, a hole transport layer 103 is formed on the back electrode layer 102. As methods for forming the hole transport layer 103, dry processes and wet processes can be mentioned, but dry processes are preferred. The dry process is not particularly limited, and for example, a method of forming the hole transport layer 103, which is a p-type semiconductor containing an organic compound or an inorganic compound, by a sputtering method can be mentioned. The film formation conditions of the sputtering method are not particularly limited, and for example, the applied power: 0.5 to 3.0 W / cm 2 , the film formation atmosphere: an argon atmosphere or a mixed atmosphere of argon and oxygen, and the film formation pressure: 0.5 to 3.0 Pa may be used. Also, when forming the light absorption layer 104, a hole transport layer 103 may be formed between the back electrode layer 102 and the light absorption layer 104 by forming a compound of the elements of the back electrode layer 102 and the elements contained in the light absorption layer 104.

[0031] 2.3. Light Absorption Layer Formation Step Next, a light absorption layer 104 is formed on the hole transport layer 103. For example, as methods for forming the light absorption layer 104, dry processes and wet processes can be mentioned, but dry processes are preferred. The dry process is not particularly limited, and for example, a method of forming the light absorption layer 104 containing a chalcopyrite compound or a kesterite compound by a sputtering method can be mentioned. The film formation conditions of the sputtering method are not particularly limited, and for example, the applied power: 0.5 to 3.0 W / cm 2 , the film formation atmosphere: an argon atmosphere, and the film formation pressure: 0.5 to 3.0 Pa may be used. Also, during sputtering, the temperature of the atmosphere and the temperature of the substrate to be sputtered do not have to be controlled. Also, 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, an electron transport layer 105 is formed on the light absorption layer 104. For example, an n-type oxide semiconductor may be formed by sputtering while supplying a gas containing an oxygen source and a hydrogen source, so as to form the electron transport layer 105 on the sputtered substrate including the light absorption layer 104. Alternatively, an n-type oxide semiconductor may be formed by sputtering while supplying a gas not containing a hydrogen source. The film formation conditions of the sputtering method are not particularly limited. For example, the applied power: 0.5 to 3.0 W / cm 2 2, the film formation atmosphere: an argon atmosphere that may contain oxygen, and the film formation pressure: 0.5 to 3.0 Pa may be used. Further, it is preferable to heat the sputtered substrate during sputtering.

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

[0034] 2.6. Grid Electrode Formation Step This manufacturing method includes a step of forming a grid electrode 107. In this step, a 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. For example, a dry process and a wet process may be used. Specifically, for example, a sputtering method, a vapor deposition method, a method of printing a paste-like conductive material on the transparent electrode layer, and a method of crimping a wire may be used.

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

[0036] 2.8. Sealing process This manufacturing method may include a step of covering the laminate including the power generation part with a sealing material. For example, as shown in FIG. 2, the solar cell laminated above is further covered with a sealing material 201 to obtain a solar cell 20. When the sealing process is included, it tends to suppress a decrease in the performance of the solar cell due to external impact, moisture, etc.

[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 located between the grid electrode 107 and the oxide insulating film 108. By configuring the solar cell 10 in such a manner, it becomes high-performance and has designability. Hereinafter, as an example of the basic configuration of the power generation part, from the substrate 101 to the transparent electrode layer 106 will be described, and further, the grid electrode 107, the oxide insulating film 108, the silver oxide film 109, etc. of this embodiment will be described in detail.

[0038] 3.1. Substrate The substrate 101 is not particularly limited, and for example, a glass substrate such as blue plate glass or low-alkali glass, a metal substrate such as stainless steel foil, aluminum foil, or titanium foil, or a resin substrate such as a polyimide resin film or an epoxy resin film can be used. The thickness of the substrate 101 is not particularly limited, and for example, it is 10 μm or more and 500 μm or less, 20 μm or more and 250 μm or less, or 30 μm or more and 100 μm or less. When the thickness of the substrate 101 is within the above range, it is preferable in terms of weight reduction and flexibility of the solar cell.

[0039] 3.2. Back electrode layer The back electrode layer 102 is generally provided to extract the current caused by the holes generated in the light absorption layer 104 described later. The back electrode layer 102 is not particularly limited as long as it has conductivity. For example, 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 metal; a conductive organic compound conductive layer made of a conductive organic compound can be used. The thickness of the back electrode layer 102 is not particularly limited. For example, it is 200 nm or more and 800 nm or less, or 300 nm or more and 700 nm or less. When the thickness of the back electrode layer 102 is within the above range, it is preferable in that the current can be sufficiently extracted without loss, and the solar cell can be made lighter and more flexible.

[0040] 3.3. Hole Transport Layer The hole transport layer 103 has a function of, for example, efficiently extracting the holes generated in the light absorption layer 104 described later from the light absorption layer 104 and preventing the recombination of electrons and holes that occur simultaneously with the success in the light absorption layer 104 described later. The hole transport layer 103 is preferably a p-type semiconductor. The substances contained in the p-type semiconductor are not particularly limited. For example, polythiophene derivatives such as poly(3,4-ethylenedioxythiophene):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; organic compounds such as polyaniline derivatives, and inorganic compounds such as nickel oxide, molybdenum oxide, gallium copper oxide, aluminum copper oxide, molybdenum selenide, and molybdenum selenide sulfide. The p-type semiconductor in the hole transport layer 103 may be used alone or in combination of two or more. In a solar cell, the formation of the hole transport layer 103 may be omitted.

[0041] 3.4. Light Absorption Layer The light absorption layer 104 has a 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 the compound constituting the light absorption layer 104 include those containing a perovskite compound, a chalcopyrite compound, or a kesterite compound. Each compound may be used alone, or two or more perovskites, chalcopyrites, or kesterites may be used in combination.

[0042] Examples of the chalcopyrite compound preferably include group I-III-VI2 chalcopyrite compounds. The group I-III-VI2 chalcopyrite compounds are not particularly limited, and examples include CuAlS2, CuAlSe2, CuAlTe2, CuGaS2, CuGaSe2, CuGaTe2, CuInS2, CuInSe2, CuInTe2, AgAlS2, AgAlSe2, AgAlTe2, AgGaS2, AgGaSe2, AgGaTe2, AgInS2, AgInSe2, AgInTe2, and combinations thereof. "Combinations thereof" are not particularly limited, and for example, when CuGaS2 and CuInSe2 are combined, Cu(In x Ga 1-x )(Se y S 1-y )2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) can be mentioned. Among these chalcopyrite compounds, CuGaS2, CuGaSe2, CuInS2, CuInSe2, Cu(In x Ga 1-x )(Se y S 1-y )2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) are preferred, and Cu(In x Ga 1-x )(Se y S 1-y )2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) are more preferred. In this embodiment, when referring to a CIS compound, it is a chalcopyrite compound containing Cu, In, and Se; when referring to a CIGS compound, it is a chalcopyrite compound containing Cu, In, Ga, and Se; and when referring to a CIGSS compound, it is a chalcopyrite compound containing Cu, In, Ga, Se, and S.

[0043] As the kesterite compound, preferably, a kesterite compound of the I2-II-IV-VI4 group is mentioned. Although not particularly limited as the I2-II-IV-VI4 group kesterite compound, for example, Cu2ZnSnS4, Cu2ZnSnSe4, Cu2ZnGeS4, Cu2ZnGeSe4, Cu2MnSnS4, Cu2MnSnSe4, Cu2MnGeS4, Cu2MnGeSe4, Ag2ZnSnS4, Ag2ZnSnSe4, Ag2ZnGeS4, Ag2ZnGeSe4, Ag2MnSnS4, Ag2MnSnSe4, Ag2MnGeS4, Ag2MnGeSe4, and combinations thereof are mentioned. "Combinations thereof" is not particularly limited, but for example, (Cu x Ag 1-x )2ZnSn(S y Se 1-y )4 (0≤x≤1) is mentioned. Cu2ZnSn(S x Se 1-x )4 (0≤x≤1, 0≤y≤1) is mentioned. Among these kesterite compounds, Cu2ZnSnS4, Cu2ZnSnSe4, Ag2ZnSnS4, Ag2ZnSnSe4, (Cu x Ag 1-x )2ZnSn(S y Se 1-y )4 (0≤x≤1, 0≤y≤1) are preferable, and (Cu x Ag 1-x )2ZnSn(S y Se 1-y )4 (0≤x≤1, 0≤y≤1) is more preferable. In addition, in this embodiment, when referring to a CZTS compound, it is a kesterite compound containing Cu, Zn, Sn, and S, when referring to an ACZTS compound, it is a kesterite compound containing Ag, Cu, Zn, Sn, and S, and when referring to an ACZTSS compound, it is 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. Specific examples include CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3SnI3, CH3NH3SnBr3, CH3NH3SnCl3, CH3NH3PbI (3-x) Cl x 、CH3NH3PbI (3-x) Br x 、CH3NH3PbBr (3-x) Cl x 、CH3NH3Pb (1-y) Sn y I3、CH3NH3Pb (1-y) Sn y Br3、CH3NH3Pb (1-y) Sn y Cl3、CH3NH3Pb (1-y) Sn y I (3-x) Cl x 、CH3NH3Pb (1-y) Sn y I (3-x) Br x 、and CH3NH3Pb (1-y) Sn y Br (3-x) Cl x 、and those in which CFH2NH3, CF2HNH3, CF3NH3, or NH2CH=NH2 is used instead of CH3NH3 in the above compounds. In the above formula, x represents any value from 0 to 3, and y represents any value from 0 to 1.

[0045] The contents of the chalcopyrite compound, the kesterite compound, and the perovskite compound in the light absorption layer 104 are not particularly limited as long as the light absorption layer 104 has a function of absorbing light such as visible light and ultraviolet light to generate electrons and holes. More specifically, although not particularly limited, the content of the above compound is 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less with respect to the total mass of the light absorption layer 104.

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

[0047] The thickness per layer of the light absorption layer 104 is preferably 0.5 μm or more and 5 μm or less, 0.8 μm or more and 4 μm or less, 1 μm or more and 3 μm or less. By setting the thickness per layer of the light absorption layer 104 within the above range, the productivity of the solar cell is further improved, and there is a tendency for weight reduction and flexibility to be facilitated.

[0048] 3.5. Electron transport layer The electron transport layer 105 has, for example, a function of efficiently extracting electrons generated in the light absorption layer 104 from the light absorption layer 104 and preventing recombination of holes generated simultaneously with the electrons in the light absorption layer 104. The electron transport layer 105 is preferably an n-type semiconductor. The substance contained in the n-type semiconductor is not particularly limited, and for example, C 60, phenanthroline derivatives such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), organic compounds such as 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), and n-type oxide semiconductors substantially composed of zinc oxide, tin oxide, titanium oxide, zinc oxide sulfide, magnesium zinc oxide, tin zinc oxide, or titanium zinc oxide, and n-type semiconductors containing cadmium sulfide, indium sulfide, or indium sulfide added with oxygen element or alkali metal element. The n-type semiconductor in the electron transport layer 105 may be used alone or in combination of two or more. The thickness of the electron transport layer 105 is, for example, 50 nm or more and 200 nm or less, 60 nm or more and 150 nm or less, 75 nm or more and 135 nm or less. When the thickness of the electron transport layer 105 is within the above range, it is preferable in that the above functions can be achieved while the solar cell can be made lighter and more flexible.

[0049] 3.6. Transparent Electrode Layer The transparent electrode layer 106 is provided, for example, to extract the current generated by the electrons in the light absorption layer 104. In a solar cell, typically, the light absorption layer 104 absorbs the light that has passed through the transparent electrode layer 106. Therefore, in order to increase the amount of light absorbed by the light absorption layer 104, this layer is made into a transparent electrode layer. As the material of the transparent electrode, known materials can be used, for example, indium tin oxide (ITO), indium oxide containing hydrogen (IOH), fluorine-containing tin oxide (FTO), boron-containing zinc oxide (ZnO:B), aluminum-containing zinc oxide (ZnO:Al), etc. The thickness of the transparent electrode layer 106 is not particularly limited, for example, 100 nm or more and 1500 nm or less, 200 nm or more and 1000 nm or less. When the thickness of the transparent electrode layer 106 is within the above range, it is preferable in that the current can be sufficiently extracted without loss while the solar cell can be made lighter and more 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. The materials that can be contained other than silver (Ag) are not particularly limited as long as they have conductivity, and for example, metals such as Mo, Cr, Cu, Ni, Al, or Ti; conductive inorganic compounds other than metals; and conductive organic compounds can be used.

[0051] The silver content in the grid electrode 107 is preferably 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less with respect to 100% by mass of the grid electrode. By setting the silver content within the above range, the effects according to the present invention tend to be more effectively and surely exhibited.

[0052] The width of the grid electrode 107 is preferably 10 μm or more and 100 μm or less, 20 μm or more and 80 μm or less, 30 μm or more and 60 μm or less. By setting the width of the grid electrode 107 within the above range, the effects according to the present invention tend to be more effectively and surely exhibited. Note that the "width" of the grid electrode 107 means the value of the width of one grid electrode at the contact surface between the transparent electrode layer 106 and the grid electrode 107. Also, the thickness of the grid electrode 107 is preferably 1 μm or more and 100 μm or less, 3 μm or more and 80 μm or less, 5 μm or more and 50 μm or less. By setting the thickness of the grid electrode 107 within the above range, the effects according to the present invention tend to be more effectively and surely exhibited.

[0053] 3.8. Oxide insulating film In the solar cell 10 of this embodiment, the oxide insulating film 108 may cover the transparent electrode layer 106 and the grid electrode 107, and may further cover the side surface of the power generation part. 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 the compound constituting such an oxide insulating film 108 include Al2O3, MgO, SiO2, and Y2O3. Among these, it is preferable to adopt at least one of Al2O3, MgO, and SiO2 as the oxide insulating film 108. From the viewpoint of antireflection, it is preferable to adopt at least one of Al2O3 and MgO, and it is more preferable to adopt Al2O3 from the viewpoints of antireflection and weather resistance. By using the oxide insulating film 108 as the above-described material, the solar cell 10 tends to be more highly efficient.

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

[0055] The thickness of the oxide insulating film 108 is preferably 10 nm or more and 300 nm or less, 20 nm or more and 150 nm or less, 30 nm or more and 100 nm or less, and 50 nm or more and 90 nm. By setting the thickness of the oxide insulating film 108 within the above range, the oxide insulating film can function as a moisture barrier film, the intrusion of moisture into the solar cell is suppressed, and the life of the solar cell can be extended.

[0056] 3.9. Silver Oxide Film The silver oxide film 109 is mainly formed as a result of the oxidation of silver contained in the grid electrode 107, and is located between the grid electrode 107 and the oxide insulating film 108.

[0057] With the silver oxide film 109, the solar cell 10 has excellent design. When the silver oxide film 109 is formed, the grid electrode 107 basically shows a dark color system or a black color system. When the amount of the formed silver oxide film 109 is small, it shows colors in the intermediate stage of blackening such as gray and light black. From the viewpoint of making the effect of improving the design more effective and reliable, the grid electrode 107 and the solar cell 10 having the silver oxide film 109 preferably show a dark color system or a black color system.

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

[0059] 3.10. Modification The 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 only to its embodiments. The solar cell of the present invention can be variously modified without departing from the gist thereof.

[0060] For example, as shown in FIG. 2, the solar cell laminated above may be further covered with a sealing material 201 to obtain a solar cell 20. When including a sealing step, it tends to suppress a decrease in the performance of the solar cell due to external impact, moisture, etc. As the sealing material, for example, those having light transparency such as ethylene vinyl acetate (EVA), ethylene / vinyl acetate / triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), urethane, and acrylic are used. From the viewpoint of making the effect according to the present invention more effective and reliable, ethylene vinyl acetate (EVA) is preferable. Further, 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 may be attached to a back sheet.

[0061] The solar cell 10 may have other layers between the respective layers, on the grid electrode 107, or under the substrate 101 as necessary. Specifically, the hole transport layer 103 may have two or more hole transport layers containing different materials respectively. Further, instead of the grid electrode 107, another hole transport layer may be provided on the transparent electrode layer 106, and an additional light absorption layer may be provided thereon. The electron transport layer 105 may have two or more electron transport layers 105 containing different materials respectively.

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

[0063] When there are a plurality of any of the layers 101 to 106, the plurality of layers may be the same as each other or different. For example, when a plurality of light absorption layers 104 are provided, each light absorption layer may contain compounds having different absorption spectra, and the electron transport layer and the hole transport layer in contact with each light absorption layer may be selected according to the properties of the light absorption layer in contact therewith. However, such a power generation unit has the oxide insulating film 108 and the silver oxide film 109 on the light receiving surface side thereof.

[0064] Similar to conventional solar cells, the solar cell of this embodiment can be used in a normal temperature environment 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 and walls of buildings or mobile means, as an independent power supply device for street lights and 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, as the conversion efficiency of the solar cell of this embodiment, preferably, it has 14% or more, has 15% or more, and has 16% or more. Having a conversion efficiency within 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. For example, it is 1 μm or more and 40.0 μm or less, 2 μm or more and 30 μm or less, and 3 μm or more and 20 μm or less. The solar cell of the present invention can constitute a thin-film solar cell by forming each layer sufficiently thin.

[0067] 4. Method for Darkening Electrodes The formation process of the oxide insulating film of this embodiment can be applied for the purpose of darkening and protecting electrodes containing silver for various devices other than the solar cell 10. In particular, it is also useful when aiming for low-power and low-temperature processing. For example, it can be applied to electrode wirings of emitting devices such as display devices.

Examples

[0068] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0069] <Method for Manufacturing Solar Cell> A solar cell having one electron transport layer as shown in FIG. 1 was manufactured. A titanium foil with a thickness of 50 μm was used as the substrate. On this substrate, a back electrode layer containing metal molybdenum was formed to a thickness of 600 nm using a sputtering method. Next, on the back electrode layer, a light absorption layer containing a CIGSS compound was formed to a thickness of 2 μm using a sputtering method. Also, when forming the light absorption layer, a 50-nm MoSe layer, which is a hole transport layer, was formed together between the light absorption layer and the above back electrode layer. Further, the obtained light absorption layer was annealed and surface-treated at 500 °C or higher and 600 °C or lower for 3 minutes or more and 30 minutes or less in a sulfur atmosphere.

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

[0071] In the following Examples and Comparative Examples, solar cells were fabricated and evaluated with the same configuration as described above except for the step of forming the following oxide insulating film.

[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, an Al2O3 layer was formed as an oxide insulating film by changing the oxygen concentration from 0% to 80% with respect to 100% by volume of the gas introducing the oxygen concentration in each example by sputtering method (Table 1). In the example of forming the MgO layer, the oxygen concentration was set to 0% and 10% respectively with respect to 100% by volume of the gas introducing the oxygen concentration (Table 2). Sputtering was performed under the following conditions except that the oxygen concentration was changed during the formation of the Al2O3 layer and the MgO layer. <Film formation conditions of sputtering> · Applied power: 5 - 9 W / cm 2 · Film formation atmosphere (gas): Oxygen (O2), Argon (Ar) · Pressure during film formation: 0.1 Pa or more and 0.5 Pa or less · Substrate temperature: Room temperature · Target type: Al2O3 single body when forming the Al2O3 layer, MgO single body when forming the MgO layer

[0073] 1.2. Evaluation: Rate of change of conversion efficiency Using the solar cell formed up to the silver grid electrode above and the solar cells of each example in which the oxide insulating film was formed, an I-V curve was measured under standard test conditions (light with a spectral spectrum of AM1.5 was irradiated with an irradiance of 1 kW / m 2Measured under the test conditions where the incident light enters and the temperature of the solar cell is 25°C. The conversion efficiency of each solar cell was calculated by the following formula. Note that the conversion efficiency (%) is the value obtained by dividing the output at the optimum operating point in the I-V curve (maximum output: Pmax) by the light energy E received by the solar cell. The change rate (%) of the conversion efficiency of each example of the solar cell with respect to the conversion efficiency of the solar cell without the oxide insulating film formed was calculated and shown in Table 1 and Table 2. Conversion efficiency (%) = (Pmax / E) × 100

[0074]

Table 1

[0075]

Table 2

[0076] 2. Refractive index of the oxide insulating film A numerical simulation was conducted assuming a case where an Al2O3 layer or an SiO2 layer was formed as an oxide insulating film on the obtained solar cell laminate, and then the entire solar cell was sealed with a sealing material, and the relationship between the conversion efficiency and the film thickness of the oxide insulating film was examined. The simulation was carried out using the "Characteristics Simulation Software for Thin-Film Solar Cells (e-ARC)" publicly available from the National Institute of Advanced Industrial Science and Technology. The conditions are shown below. For the conversion efficiency of each example obtained by simulation, the change rate with respect to the conversion efficiency in the case of sealing with a sealing material without forming an oxide insulating film (Comparative Example 3 and Comparative Example 4) was calculated (Table 3 and Table 4). <Simulation conditions> · Spectral spectrum: AM1.5 · Irradiance: 1 kW / m 2 · Solar cell temperature: 25°C · Sealing material: Refractive index 1.5, thickness 0.2 mm

[0077] ;

Table 3

Table 4

[0078] <Supplementary Note> Embodiments of the present disclosure include the following aspects. [1] A step of forming a grid electrode containing silver on a transparent electrode layer on the light-receiving surface side of a solar cell; A step of forming an oxide insulating film by a sputtering method while supplying a gas containing oxygen to the 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. A method for manufacturing a solar cell. [2] 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 oxygen. The method for manufacturing a solar cell according to [1]. [3] The step of forming the oxide insulating film is performed at a temperature of 80°C or lower. The method for manufacturing a solar cell according to [1] or [2]. [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 located between the grid electrode and the oxide insulating film. A solar cell. [5] 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. The solar cell according to [4]. [6] The refractive index of the oxide insulating film is 1.5 or more and 2.0 or less. The solar cell according to [4] or [5]. [7] The oxide insulating film contains at least one of MgO and Al2O3. The solar cell according to any one of [4] to [6]. [8] The thickness of the oxide insulating film is 50 nm or more and 90 nm or less. The solar cell according to any one of [4] to [7]. [9] Further including a sealing material. The solar cell according to any one of [4] to [8].

Description of symbols

[0079] 10, 20... solar cells, 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 the light-receiving surface side of a solar cell; A step of forming an oxide insulating film by a sputtering method while supplying a gas containing oxygen to the surfaces of the transparent electrode layer and the grid electrode; and the method for manufacturing a solar cell is provided. In the step of forming the oxide insulating film, a silver oxide film is formed between the grid electrode and the oxide insulating film. A method for manufacturing a solar cell.

2. 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 oxygen. The method for manufacturing a solar cell according to Claim 1.

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

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 located between the grid electrode and the oxide insulating film. A solar cell.

5. 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. The solar cell according to Claim 4.

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

7. The oxide insulating film contains at least one of MgO and Al 2 O 3 and the like The solar cell according to Claim 4.

8. The thickness of the oxide insulating film is 50 nm or more and 90 nm or less. The solar cell according to Claim 4.

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