Method for manufacturing solar cells and solar cells

Abstract

To provide a method for manufacturing a high-productivity solar cell to realize high performance of the solar cell.SOLUTION: A method for manufacturing a solar cell comprises: a precursor formation step for forming a precursor having an InGaSe layer, a CuSe layer and an InSe layer; and a crystallization step for heating the precursor to obtain a crystallized light absorption layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a solar cell and to a solar cell. [Background technology]

[0002] While silicon solar cells, manufactured using materials such as monocrystalline or polycrystalline silicon, offer excellent durability, their high manufacturing cost and thickness make them suitable for large-scale power generation facilities. Thin-film solar cells, on the other hand, are constructed 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, due to their extreme thinness, can be used in a variety of flexible applications. Because of these characteristics, various studies have recently been conducted on conversion efficiency, durability, and other aspects of thin-film solar cells for future applications.

[0003] For example, Patent Document 1 describes a method in which metallic components such as Cu, In, and Ga are layered by sputtering, and then a light-absorbing layer is formed while heating in an atmosphere of H2Se or H2S, thereby reducing manufacturing costs. Furthermore, Patent Document 2 describes that, in addition to the above method, internal defects in the thin film can be reduced by forming a light-absorbing layer while heating the substrate above its crystallization temperature. However, since high-temperature heating and sputtering are performed simultaneously, there are concerns that the cost of the equipment will increase.

[0004] In Patent Document 3, a method was attempted in which Cu, In, Ga, and Se, either as individual elements or alloys, were simultaneously sputtered and then annealed to crystallize them, but the power generation performance was insufficient. Therefore, Patent Document 4 describes that power generation performance can be improved by stacking CuSe (a group I selenium) and InGaSe (a group III selenium) and crystallizing them in an atmosphere of Se vapor or H2Se gas. [Prior art documents] [Patent Documents]

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the methods described in Patent Document 1 and Patent Document 2, when reacting while heating in an atmosphere of H₂Se or H₂S, there is a concern that the volume expansion of the light absorption layer is large, many defects appear in the film, and the surface roughness also increases. Furthermore, according to the methods described in Patent Document 3 and Patent Document, although the defects and surface roughness in the film can be suppressed to some extent, since it is necessary to anneal in an atmosphere of Se vapor or H₂Se gas, equipment considering the environment and safety is required, the cost increases, and the crystal grains are small and the power generation performance is not yet sufficient.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a solar cell and a solar cell that achieve both high performance and high productivity.

Means for Solving the Problems

[0008] A method for manufacturing a solar cell according to an embodiment of the present invention includes a precursor formation step of forming a precursor having an InGaSe layer, a CuSe layer, and an InSe layer, and a crystallization step of obtaining a light absorption layer crystallized by heating the precursor.

[0009] In the manufacture of a solar cell, since the precursor has an InGaSe layer, a CuSe layer, and an InSe layer, the productivity of the solar cell is improved, and the obtained solar cell has high performance.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a solar cell that achieves both high performance and high productivity, and a method for manufacturing the same.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic cross-sectional view of a precursor of a light absorption layer according to an embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view of a precursor of a light absorption layer according to an embodiment of the present invention. [Figure 3] It is a schematic cross-sectional view of a precursor of a light absorption layer according to an embodiment of the present invention. [Figure 4] It is a schematic cross-sectional view of a solar cell according to an embodiment of the present invention. [Figure 5] It is a diagram showing an X-ray diffraction pattern of each layer included in a light absorption layer according to an embodiment of the present invention. [Figure 6] It is a diagram showing a change in an X-ray diffraction pattern according to the formation temperature of an InSe layer according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0012] 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 to this, 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 explanations 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.

[0013] 1. Light Absorption Layer Formation Step The method for manufacturing a solar cell according to the present embodiment includes a precursor formation step of forming a precursor having an InGaSe layer, a CuSe layer, and an InSe layer in the light absorption layer formation step, and a crystallization step of obtaining a light absorption layer crystallized by heating the precursor.

[0014] Conventionally, a manufacturing method for CIGS-type chalcopyrite solar cells containing Cu, In, Ga, and Se involved separately stacking Group I CuSe and Group III InGaSe, and then annealing them in a Se vapor or H2Se gas atmosphere to crystallize them, thereby improving power generation performance. However, solar cells obtained by this method had the problem of having small crystal grains in the light-absorbing layer and insufficient crystal quality, resulting in unsatisfactory power generation performance. Furthermore, because this method requires annealing in a Se vapor or H2Se gas atmosphere during manufacturing, it necessitates equipment that takes environmental and safety considerations into account, raising concerns about enormous costs.

[0015] Therefore, the inventors of the present invention have found that by separately stacking an InGaSe layer, a CuSe layer, and an InSe layer as precursors for the chalcopyrite light absorption layer, and then heating the precursors to crystallize them, the crystal grain size of the light absorption layer can be increased, improving the crystal quality and resulting in a high-performance solar cell. Furthermore, since the heating process in an atmosphere containing Se is not necessarily required, it is possible to manufacture solar cells with high productivity. While the reasons for the superiority of the above method are not entirely clear, it is thought that by forming the InGaSe layer, CuSe layer, and InSe layer separately before crystallization, good seed crystals are preferentially formed at the interface between the CuSe layer and the InSe layer, resulting in increased grain size and improved crystal quality. Furthermore, it is presumed that the resulting optimal elemental profile of the Se elements within the film during crystallization, which eased crystal strain, also contributed synergistically. However, the factors are not limited to those mentioned above.

[0016] In this specification, "high-performance solar cell" means that the solar cell's battery characteristics related to its power generation performance are superior in at least one parameter. Furthermore, in this specification, "high-productivity solar cell" means that the solar cell has low production costs and a highly reliable manufacturing method. The manufacturing method of the solar cell of this embodiment will be described in detail below.

[0017] 1.1. Precursor formation process The precursor formation step of this embodiment is a step of forming a precursor having an InGaSe layer, a CuSe layer, and an InSe layer. By forming a precursor having each of the above layers, the number of crystal grains in the resulting light-absorbing layer increases, improving the crystal quality and thus improving the power generation performance.

[0018] Figure 1 shows a schematic cross-sectional view of one example of a precursor for the light-absorbing layer. As shown in Figure 1, the precursor of this embodiment has at least one InGaSe layer, one CuSe layer, and one InSe layer.

[0019] In the precursor formation process, it is preferable to make the InGaSe layer or InSe layer amorphous, and it is even more preferable to make both the InGaSe layer and the InSe layer amorphous. By making the InGaSe layer or InSe layer amorphous, the generation of unintended seed crystals other than at the interface with the CuSe layer is suppressed, which increases the number of crystal grains in the resulting light-absorbing layer and improves the crystal quality, which tends to further improve power generation performance. In this specification, "amorphous" is determined by the absence of peaks in the 2θ-θ pattern obtained from X-ray diffraction measurements that exceed twice the noise width above and below the baseline.

[0020] The method for forming each layer is not particularly limited, but from the viewpoint of mass production and reliability, it is preferable to form them by sputtering and / or vapor deposition, and sputtering alone may also be used. When forming the precursor, the surface temperature of the substrate to be sputtered is preferably 300°C or lower, 250°C or lower, 200°C or lower, and room temperature (RT). By setting the temperature of the substrate to be sputtered within the above range, the InGaSe layer and InSe layer tend to become amorphous layers, and the resulting solar cell tends to be more high-performance and have higher productivity. In this specification, the substrate to be sputtered is the substrate on the stage when sputtering is performed, on which compounds derived from the sputtering target are laminated.

[0021] The target used for sputtering is not particularly limited, and when forming each layer, for example, in the case of an InGaSe layer, elements or mixtures of In, In4Se3, InSe, In2Se3, GaSe, Ga2Se3, and Se may be used; in the case of a CuSe layer, elements or mixtures of Cu, Cu2Se, CuSe2, and Se may be used; and in the case of an InSe layer, elements or mixtures of In, In4Se3, InSe, In2Se3, and Se may be used. Among these, in the case of an InGaSe layer, a mixture of In2Se3 and Ga2Se3 with a Ga2Se3 proportion of 30% to 60% is preferred, in the case of a CuSe layer, elemental CuSe2 is preferred, and in the case of an InSe layer, elemental In2Se3 is preferred. Examples of gases supplied during sputtering include inert gases such as Ar or He, as well as H2, H2Se, H2S, etc. Among these, Ar is preferred as the inert gas, and H2 is preferred as the other gas, from the viewpoint of more reliably achieving the effects of the present invention.

[0022] In the precursor formation process, it is preferable to form the InSe layer on the light-receiving surface side of the InGaSe layer. Forming the InSe layer on the light-receiving surface side of the InGaSe layer tends to further improve the power generation performance of the resulting solar cell.

[0023] In the precursor formation process, it is preferable to form the InSe layer on the light-receiving side. Forming the InSe layer on the light-receiving side tends to further improve the power generation performance of the resulting solar cell. From a similar viewpoint, it is preferable to form the InSe layer on the light-receiving side and the CuSe layer as the second layer, also on the light-receiving side.

[0024] Figure 2 shows a schematic cross-sectional view of another example of a precursor for the light-absorbing layer. As shown in Figure 2, the precursor of this embodiment has an InGaSe layer, a CuSe layer, and an InSe layer, and it is preferable that the InSe layer is formed on the light-receiving surface side of the InGaSe layer. Also, as shown in Figure 2, the precursor of this embodiment has an InGaSe layer, a CuSe layer, and an InSe layer, and it is preferable that the InSe layer is formed on the light-receiving surface side.

[0025] In the precursor formation process, preferably, two or more InGaSe layers and three or more CuSe layers are formed, or five or more CuSe layers are formed, respectively. By forming two or more InGaSe layers and CuSe layers, the power generation performance of the resulting solar cell tends to improve further.

[0026] Figure 3 shows a schematic cross-sectional view of another example of a precursor for the light-absorbing layer. As shown in Figure 3, the precursor of this embodiment has an InGaSe layer, a CuSe layer, and an InSe layer, and it is preferable to form two or more layers each of the InGaSe layer and the CuSe layer. Also, as shown in Figure 3, the precursor of this embodiment has an InGaSe layer, a CuSe layer, and an InSe layer, and it is preferable to form the InSe layer on the side closest to the light-receiving surface.

[0027] In the entire precursor formed, the ratio of the amount of Ga element to the total amount of In element (Ga / (In+Ga)) is preferably between 0.10 and 0.50, between 0.15 and 0.40, and between 0.20 and 0.40. By keeping the amount of (Ga / (In+Ga)) in the entire precursor within the above range, the power generation performance of the resulting solar cell tends to improve further. Furthermore, in the entire precursor formed, the ratio of the amount of Cu element to the total amount of In and Ga elements (Cu / (In+Ga)) is preferably between 0.50 and 1.0, between 0.75 and 0.95, and between 0.80 and 0.90. By keeping the amount of (Cu / (In+Ga)) in the entire precursor within the above range, the power generation performance of the resulting solar cell tends to improve further. Furthermore, in the entire precursor formed, the ratio of the amount of Se element to the total amount of Cu, In, and Ga elements (Se / (Cu+In+Ga)) is preferably 0.5 or more, 0.8 or more, and 1.0 or more. By setting the molar ratio of (Se / (Cu+In+Ga)) within the above range, the amount of Se element in the precursor becomes sufficient, and the power generation performance and productivity of the resulting solar cell tend to improve further. Also, the upper limit of the molar ratio of (Se / (Cu+In+Ga)) is not particularly limited and may be, for example, 10.0 or less, 7.5 or less, 5.0 or less, or 3.0 or less.

[0028] In the InGaSe layer, the ratio of the amount of Ga to the total amount of In and Ga (Ga / (In+Ga)) is preferably between 0.1 and 0.8, between 0.2 and 0.7, and between 0.3 and 0.6. By keeping the (Ga / (In+Ga)) ratio in the InGaSe layer within the above range, the power generation performance of the resulting solar cell tends to improve further.

[0029] The ratio of the total amount of substance Y (Y / X) of In and Ga elements in the InGaSe layer to the amount of substance X of In element in the InSe layer is preferably between 0.5 and 2.5, and between 1.0 and 1.5. By keeping the amount of substance ratio (Y / X) within the above range, the power generation performance of the resulting solar cell tends to improve further.

[0030] In the InGaSe layer and the InSe layer, the ratio of the amount of Se element to the total amount of In and Ga elements (Se / (In+Ga)) is preferably 0.8 or more and 2.0 or less, and 1.0 or more and 1.75 or less. When the CuSe layer is formed on the outermost surface of the precursor, the (Se / (In+Ga)) value in the InGaSe layer and the InSe layer is preferably 1.0 or more and 2.0 or less, and 1.25 or more and 1.75 or less. If the CuSe layer is not formed on the outermost surface of the precursor, the (Se / (In+Ga)) value in the InGaSe layer and the InSe layer is preferably 1.0 or more and 2.0 or less, and 1.0 or more and 1.5 or less. When the (Se / (In+Ga)) value in the InGaSe layer and the InSe layer is kept within the above range, the power generation performance of the resulting solar cell tends to improve further. In this specification, the outermost layer of the precursor refers to the layer closest to the light-receiving surface.

[0031] The (Se / Cu) molar ratio within the CuSe layer is preferably 0.5 to 4.0, and 0.5 to 3.0. When a CuSe layer is formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is preferably 1.5 or more and 5.0 or less, and 2.0 or more and 3.0 or less. If the CuSe layer is not formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is preferably 0.3 or more and 2.5 or more, and 0.5 or more and 2.0 or more. In a CuSe layer, the power generation performance of the resulting solar cell tends to improve further by keeping the ratio of the amount of Se element to the amount of Cu element (Se / Cu) within the above range.

[0032] The method for determining the elemental content within each layer of the precursor is not particularly limited, and for example, inductively coupled plasma (ICP) emission spectroscopy, energy dispersive X-ray spectroscopy (EDX or EDS), secondary ion mass spectrometry (SIMS), etc., can be used.

[0033] Methods for adjusting the elemental content in each layer during the precursor formation process include, for example, adjusting the elemental content of the raw material (target) used during sputtering or deposition, and controlling the deposition pressure or applied power.

[0034] The thickness of the precursor to be formed can be adjusted as needed, depending on the configuration and purpose of the solar cell. The overall thickness of the precursor should ideally be between 700 nm and 3200 nm, or between 1500 nm and 2700 nm. The thickness of the InGaSe layer to be formed is preferably 300 nm to 1300 nm and 600 nm to 1200 nm per layer. The thickness of the CuSe layer to be formed is preferably 100 nm to 700 nm and 300 nm to 600 nm per layer. The thickness of the InSe layer to be formed is preferably 300 nm to 1200 nm and 600 nm to 1100 nm per layer. By setting the thickness of each layer in the precursor formation process as described above, the power generation performance of the resulting solar cell can be improved even more reliably.

[0035] 1.2.Crystallization process The crystallization step in this embodiment is a step of obtaining a light-absorbing layer by heating the formed precursor to crystallize it. The heating may be performed only once, or it may be performed in two or more stages.

[0036] The heating temperature in the crystallization process is preferably between 300°C and 600°C, and between 400°C and 600°C. By setting the heating temperature within the above range, the number of crystal grains in the light-absorbing layer increases, improving the crystal quality, which tends to further improve the power generation performance of the resulting solar cell.

[0037] The crystallization process may be carried out in an inert atmosphere or an atmosphere containing Se element, and is preferably carried out in an inert atmosphere. By performing crystallization in an inert atmosphere, the power generation performance of the solar cell can be improved even more reliably. Examples of inert gases include nitrogen (N2) and argon (Ar), with nitrogen being preferred.

[0038] 1.3. Surface treatment process The solar cell manufacturing method of this embodiment preferably further includes a surface treatment step after the crystallization step, in which the surface of the light-absorbing layer is treated in a sulfur atmosphere at 350°C to 600°C. By performing the surface treatment step, the band gap on the light-receiving side of the light-absorbing layer can be controlled, which tends to result in a higher-performance solar cell.

[0039] The ambient temperature during surface treatment may be between 400°C and 600°C, or between 500°C and 600°C. Performing the surface treatment process within the above temperature range tends to result in higher performance solar cells.

[0040] The time required for the surface treatment process may be, for example, between 1 minute and 60 minutes, or between 3 minutes and 30 minutes. By keeping the time required for the surface treatment process within these ranges, solar cells tend to become even more high-performance.

[0041] 2. Solar cells The solar cell of this embodiment includes a light-absorbing layer 104 manufactured by the method described above, and has a configuration described later. The solar cell including the light-absorbing layer 104 manufactured by the method described above has excellent conversion efficiency and high performance, and also has excellent productivity because the manufacturing process can be simplified.

[0042] Figure 4 shows an example of the cross-sectional structure of the solar cell according to this embodiment. As shown in Figure 4, for example, the solar cell 10 includes a substrate 107, a first electrode layer 106 provided on the substrate 107, a hole transport layer 105 provided on the first electrode layer 106, a light absorption layer 104 provided on the hole transport layer 105, an electron transport layer 103 provided on the light absorption layer 104, a second electrode layer 102 provided on the electron transport layer 103, and a grid electrode 101 provided on the second electrode layer 102. The solar cell 10 generates electricity by receiving light from the second electrode layer 102 side.

[0043] The following describes each layer that makes up the solar cell 10.

[0044] 2.1. Circuit board The substrate 107 is not particularly limited, and for example, glass substrates such as blue glass or low-alkali glass, metal substrates such as stainless steel foil, aluminum foil, or titanium foil, or resin substrates such as polyimide resin film or epoxy resin film can be used. The thickness of the substrate 107 is not particularly limited, and for example, it can be 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. A thickness of the substrate 107 within the above range is preferable in that it allows for weight reduction and flexibility of the solar cell.

[0045] 2.2.First electrode layer The first electrode layer 106 is generally provided to extract the current generated by holes in the light absorption layer 104, which will be described later. The first electrode layer 106 is not particularly limited as long as it is conductive, and 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 a metal; or a conductive organic compound conductive layer made of a conductive organic compound can be used. The thickness of the first electrode layer 106 is not particularly limited, and for example, it is 200 nm to 800 nm, or 300 nm to 700 nm. A thickness of the first electrode layer 106 within the above range is preferable because it allows for sufficient current extraction without loss while enabling the solar cell to be made lighter and more flexible.

[0046] 2.3. Hole Transport Layer The hole transport layer 105 has the function of efficiently extracting holes generated in the light absorption layer 104 (described later) and preventing the recombination of electrons and holes generated simultaneously in the light absorption layer 104. The hole transport layer 105 is preferably a p-type semiconductor. The substances included in the p-type semiconductor are not particularly limited and include, for example, 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; polyaniline derivatives, and other organic compounds, as well as inorganic compounds such as nickel oxide, molybdenum oxide, copper gallium oxide, copper aluminum oxide, molybdenum selenide, and molybdenum selenide sulfide. The p-type semiconductor in the hole transport layer 105 may be used alone or in combination of two or more types. Furthermore, the formation of the hole transport layer 105 may be omitted in the solar cell.

[0047] 2.4. Light-absorbing layer 2.4.1. Light-absorbing layer of this embodiment 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, and sunlight is an example of such light. The light-absorbing layer 104 in the solar cell of this embodiment contains CIGS-type chalcopyrite obtained by the precursor formation step and crystallization step described above. If the surface treatment step described above is additionally performed on the obtained light-absorbing layer 104, it will contain even more sulfur components, and can therefore be called a light-absorbing layer 104 containing CIGSS-type (containing Cu, In, Ga, Se, S) chalcopyrite.

[0048] The band gap of the light-absorbing layer 104 in this embodiment is preferably 2.0 eV or less, 1.8 eV or less, 1.5 eV or less, 1.2 eV or less, and 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 becomes high-performance.

[0049] For measuring the band gap, known methods can be used. Specifically, for example, it can be measured by spectral transmittance measurement or spectral quantum efficiency measurement.

[0050] In the light-absorbing layer 104 of this embodiment, the band gap in the section from the light-receiving surface to a depth of 200 nm is preferably 1.1 eV or more and 1.4 eV or less, the band gap in the section from 200 nm to 400 nm is preferably 0.9 eV or more and 1.2 eV or less, and beyond 400 nm is preferably 1.2 eV or more and 1.7 eV or less. By keeping the band gap within the above range, it tends to be possible to prevent the recombination of electrons and holes generated by light absorption.

[0051] The thickness of each layer of the light-absorbing layer 104 in this embodiment 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 layer of the light-absorbing layer 104 within the above range, the productivity of the solar cell is further improved, and it tends to become easier to reduce weight and make it more flexible.

[0052] The ratio of the light-absorbing layer 104 in this embodiment is not particularly limited, and is, for example, 50% to 100% by mass, 60% to 100% by mass, 70% to 100% by mass, 80% to 100% by mass, or 90% to 100% by mass, relative to the total mass of the light-absorbing layer 104.

[0053] 2.4.2. Additional light-absorbing layer The solar cell may have an additional light absorption layer different from the light absorption layer 104. Such an additional light absorption layer may, for example, further have a hole transport layer on the second electrode layer 102 of a solar cell already having a light absorption layer, and a mode having an additional light absorption layer is conceivable. When not having a further hole transport layer, it may have an additional light absorption layer on the second electrode layer 102. Examples of the compound serving as the additional light absorption layer include those containing a perovskite compound, a chalcopyrite compound, or a kesterite compound. Each compound may be used alone, or two or more kinds of perovskite, chalcopyrite, or kesterite may be used in combination.

[0054] Examples of the perovskite compound include organic-inorganic perovskite compounds, particularly halide-based organic-inorganic perovskite compounds. Specific examples include CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3SnI3, CH3NH3SnBr3, CH3NH3SnCl3, CH3NH3PbI y , x , x , y , x , (3-x) , (1-y) , (3-x) , (3-x) , (1-y) 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​​​​​​​​​Furthermore, examples include compounds in which CFH2NH3, CF2HNH3, CF3NH3, or NH2CH=NH2 are used instead of CH3NH3 in the above compounds. In the above formula, x represents any value between 0 and 3, and y represents any value between 0 and 1.

[0055] Examples of chalcopyrite compounds that differ from the CIGS-type chalcopyrite compounds obtained by the production method of the present invention include CuAlS2, CuAlSe2, CuAlTe2, CuGaS2, CuGaSe2, CuGaTe2, CuInS2, CuInSe2, CuInTe2, AgAlS2, AgAlSe2, AgAlTe2, AgGaS2, AgGaSe2, AgGaTe2, AgInS2, AgInSe2, AgInTe2, and combinations thereof. "These combinations" are not particularly limited and include, for example, Cu(In) when CuGaS2 and CuInSe2 are combined. x Ga 1-x )(Se y S 1-y )2(0≦x≦1, 0≦y≦1) is one example.

[0056] Examples of kestellite compounds include I2-II-IV-VI4 kestellite compounds, more specifically Cu2ZnSnS4, Cu2ZnSnSe4, Cu2ZnGeS4, Cu2ZnGeSe4, Cu2MnSnS4, Cu2MnSnSe4, Cu2MnGeS4, Cu2MnGeSe4, Ag2ZnSnS4, Ag2ZnSnSe4, Ag2ZnGeS4, Ag2ZnGeSe4, Ag2MnSnS4, Ag2MnSnSe4, Ag2MnGeS4, Ag2MnGeSe4, and combinations thereof. "These combinations" are not particularly limited, for example, when Cu2ZnSnS4 and Ag2ZnSnSe4 are combined (Cu x Ag 1-x )2ZnSn(S y Se 1-y )4 (0≦x≦1) is one example.

[0057] 2.5.Electron transport layer The electron transport layer 103 has the function of efficiently extracting electrons generated in the light absorption layer 104 from the light absorption layer 104 and preventing recombination of electrons with holes generated simultaneously in the light absorption layer 104. The electron transport layer 103 is preferably an n-type semiconductor. The material included in the n-type semiconductor is not particularly limited; for example, C 60 Examples include 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), n-type oxide semiconductors substantially composed of zinc oxide, tin oxide, titanium oxide, zinc sulfide, zinc magnesium oxide, zinc tin oxide, or zinc titanium oxide, and n-type semiconductors containing cadmium sulfide, indium sulfide, or indium sulfide doped with oxygen or alkali metal elements. The n-type semiconductor in the electron transport layer 103 may be used alone or in combination of two or more types. The thickness of the electron transport layer 103 is, for example, 50 nm to 200 nm, 60 nm to 150 nm, or 75 nm to 135 nm. A thickness within the above range of the electron transport layer 103 is preferable because it allows for weight reduction and flexibility of the solar cell while maintaining the above-mentioned functions.

[0058] 2.6.Second electrode layer The second electrode layer 102 is provided, for example, to extract the current generated by electrons in the light absorption layer 104. In a solar cell, typically, the light absorption layer 104 absorbs the light that passes through the second electrode layer 102. Therefore, it is preferable to make the second electrode layer 102 a transparent electrode layer in order to increase the amount of light absorbed by the light absorption layer 104. Known materials can be used as the material for the transparent electrode, for example, indium tin oxide (ITO), hydrogen-containing indium oxide (IOH), fluorine-containing tin oxide (FTO), boron-containing zinc oxide (ZnO:B), aluminum-containing zinc oxide (ZnO:Al), etc. The thickness of the second electrode layer 102 is not particularly limited, and for example, it is 100 nm to 1500 nm, or 200 nm to 1000 nm. Setting the thickness of the second electrode layer 102 within the above range is preferable because it allows for sufficient current extraction without loss while enabling the solar cell to be made lighter and more flexible.

[0059] 2.7. Grid electrodes The grid electrode 101 is provided, for example, to extract electricity from the second electrode layer 102. The material of the grid electrode 101 is not particularly limited as long as it is conductive, and for example, metals such as Mo, Cr, Ag, Cu, Ni, Al, or Ti; conductive inorganic compounds other than metals; and conductive organic compounds can be used. The thickness of the grid electrode 101 is not particularly limited, and for example, it is 5 μm or more and 50 μm or less. Setting the thickness of the grid electrode 101 within the above range is preferable in that it allows for weight reduction and flexibility of the solar cell.

[0060] 2.8. Example of changes The solar cell 10 shown in Figure 4 is an example for illustrating the solar cell of the present invention, and is not intended to limit the present invention to its embodiments only. The solar cell of the present invention can be modified in various ways without departing from its essence.

[0061] For example, the solar cell 10 may have other layers between each layer, above the grid electrode 101, or below the substrate 107 as needed. Specifically, the hole transport layer 105 may have two or more hole transport layers, each containing a different material, and the grid electrode 101 may have a contamination prevention layer to prevent external contamination. Alternatively, the second electrode layer 102 may have another hole transport layer instead of the grid electrode 101, with an additional light absorption layer on top of it, and the electron transport layer 103 may have two or more electron transport layers 103, each containing a different material. However, at least one of the light absorption layers is the light absorption layer 104 obtained by the manufacturing method of this embodiment.

[0062] The solar cell 10, although not shown in the figures, may consist of a hole transport layer 105, a light absorption layer 104 provided on the hole transport layer 105, an electron transport layer 103 provided on the light absorption layer, and a second electrode layer 102 provided on the electron transport layer 103, with two sets of these sets stacked on the first electrode layer 106, or three sets of these sets stacked. Furthermore, a grid electrode may be provided on the uppermost second electrode layer.

[0063] If there are multiple layers 101 to 107, these layers may be the same or different. For example, if there are multiple light-absorbing layers 104, 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 they are in contact with. However, at least one of the light-absorbing layers is a light-absorbing layer 104 obtained by the manufacturing method described above.

[0064] The solar cell of this embodiment can be used in a normal temperature environment where the solar cell temperature is approximately 45 to 85°C, similar to conventional solar cells. For example, it can be suitably used as a power generation device attached to the windows and walls of buildings and vehicles, as an independent power supply device for streetlights 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 high conversion efficiency. More specifically, the conversion efficiency of the solar cell of this embodiment preferably has 14% or more, 15% or more, and 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 excluding the substrate 107 is not particularly limited, and may be, for example, 1.0 μm to 10.0 μm, 1.1 μm to 8.0 μm, or 1.2 μm to 6.0 μm. The solar cell of the present invention can be constructed as a thin-film solar cell by forming each layer sufficiently thin.

[0067] 3. Manufacturing method of solar cells Next, the manufacturing method of the solar cell of this embodiment, shown in Figure 4, will be described.

[0068] 3.1. First electrode layer formation process First, for example, a first electrode layer 106 is formed on the substrate 107. Methods for forming the first electrode layer 106 include a dry process and a wet process, but a dry process is preferred. The dry process is not particularly limited; for example, a method of forming the first electrode layer 106, which is a metallic conductive layer, by sputtering is used. The film deposition conditions for the sputtering method are not particularly limited; for example, applied power: 1.0~3.0 W / cm². 2 The deposition atmosphere may be an argon atmosphere, and the deposition pressure may be 0.5 to 3.0 Pa. In the first electrode layer formation step, for example, substrate 107 may be used as the substrate to be sputtered. In this specification, the substrate to be sputtered is a substrate on the stage used when sputtering is performed, on which compounds derived from the sputtering target are laminated.

[0069] 3.2. Hole Transport Layer Formation Process Next, for example, a hole transport layer 105 is formed on the first electrode layer 106. Methods for forming the hole transport layer 105 include a dry process and a wet process, but a dry process is preferred. The dry process is not particularly limited, and for example, a method of forming the hole transport layer 105, which is a p-type semiconductor containing an organic or inorganic compound, by sputtering is used. The film deposition conditions for the sputtering method are not particularly limited, and for example, applied power: 0.5~3.0 W / cm². 2 The deposition atmosphere may be an argon atmosphere or a mixed atmosphere of argon and oxygen, and the deposition pressure may be 0.5 to 3.0 Pa. In addition, when forming the light absorption layer 104, a compound may be formed between the elements of the first electrode layer 106 and the elements contained in the light absorption layer 104, and a hole transport layer 105 may be formed between the first electrode layer 106 and the light absorption layer 104.

[0070] 3.3. Light-absorbing layer formation process Next, a light-absorbing layer 104 is formed on the hole transport layer 105. The method for forming the light-absorbing layer 104 is as described in "1. Light-absorbing layer formation process".

[0071] 3.4.Electron transport layer formation process Next, an electron transport layer 103 is formed on the light absorption layer 104. For example, the electron transport layer 103 may be formed on the substrate to be sputtered, including the light absorption layer 104, by depositing an n-type oxide semiconductor film by sputtering while supplying a gas containing an oxygen source and a hydrogen source, or the n-type oxide semiconductor film may be deposited by sputtering while supplying a gas that does not contain a hydrogen source. The film deposition conditions for the sputtering method are not particularly limited, for example, applied power: 0.5~3.0W / cm 2 The deposition atmosphere may be an argon atmosphere that may contain oxygen, and the deposition pressure may be 0.5 to 3.0 Pa. Furthermore, it is preferable to heat the substrate to be sputtered during sputtering.

[0072] 3.5. Second electrode layer formation process Next, a second electrode layer 102 is formed on the electron transport layer 103. Methods for forming the second electrode layer 102 include a dry process and a wet process, but a dry process is preferred. The dry process is not particularly limited; for example, a method of forming the transparent electrode layer, the second electrode layer 102, by sputtering is used. The film deposition conditions for the sputtering method are not particularly limited; for example, applied power: 0.5~3.0 W / cm². 2 The deposition atmosphere may be an argon atmosphere or a mixed atmosphere of argon, oxygen, and hydrogen, and the deposition pressure may be 0.5 to 3.0 Pa.

[0073] 3.6. Grid electrode formation process Next, a grid electrode 101 is formed on the second electrode layer 102. Methods for forming the grid electrode 101 include dry processes and wet processes. Specifically, examples include sputtering, vapor deposition, printing a paste-like conductive material onto the second electrode layer 102, or crimping conductive wires.

[0074] Furthermore, an additional light absorption layer formation step may be provided after forming the light absorption layer 104 but before forming the grid electrode. As such an additional light absorption layer formation step, for example, a hole transport layer may be formed on the second electrode layer 102 before forming the additional light absorption layer. If there is no hole transport layer, the additional light absorption layer may be formed on the second electrode layer. Methods for forming the additional light absorption layer include dry processes and wet processes, but the dry process is preferred. The dry process is not particularly limited, and for example, a method of forming an additional light absorption layer containing a perovskite compound, chalcopyrite compound, or kestelite compound by sputtering is included. The film deposition conditions for the sputtering method are not particularly limited, and for example, applied power: 0.5~3.0 W / cm² 2The deposition atmosphere may be an argon atmosphere, and the deposition pressure may be 0.2 to 3.0 Pa. Alternatively, the process may include annealing in a nitrogen or iodine atmosphere at 80°C to 200°C after sputtering. Or, the process may include annealing in a nitrogen or selenium and sulfur atmosphere at 350°C to 650°C after sputtering.

[0075] <Note> Embodiments of this disclosure include the following aspects: [1] A precursor formation step for forming a precursor having an InGaSe layer, a CuSe layer, and an InSe layer, The process includes a crystallization step of obtaining a light-absorbing layer by heating the precursor, A method for manufacturing solar cells. [2] In the precursor formation step, the InGaSe layer and the InSe layer are amorphous. [1] The method for manufacturing a solar cell as described above. [3] In the precursor formation step, each layer is formed at a temperature of 200°C or lower by sputtering and / or vapor deposition. A method for manufacturing a solar cell as described in [1] or [2]. [4] In the precursor formation step, the InSe layer is formed on the light-receiving surface side of the InGaSe layer. A method for manufacturing a solar cell as described in any one of [1] to [3]. [5] In the precursor formation step, the InSe layer is formed closest to the light-receiving surface. A method for manufacturing a solar cell as described in any one of [1] to [4]. [6] In the precursor formation step, two or more layers of the InGaSe layer and the CuSe layer are formed. A method for manufacturing a solar cell as described in any one of [1] to [5]. [7] In the InGaSe layer, the ratio of the amount of Ga to the total amount of In and Ga (Ga / (In+Ga)) is between 0.3 and 0.6. A method for manufacturing a solar cell as described in any one of [1] to [6]. [8] The ratio of the total amount of substance Y (Y / X) of In and Ga elements in the InGaSe layer to the amount of substance X of In element in the InSe layer is 1.0 or more and 1.5 or less. A method for manufacturing a solar cell as described in any one of [1] to [7]. [9] In the aforementioned precursor, The ratio of the amount of Ga to the total amount of In and Ga (Ga / (In+Ga)) is between 0.15 and 0.40. The ratio of the amount of Cu to the total amount of In and Ga (Cu / (In+Ga)) is between 0.75 and 0.95. The ratio of the amount of Se element to the total amount of Cu, In, and Ga elements (Se / (Cu+In+Ga)) is 1.0 or greater. A method for manufacturing a solar cell as described in any one of [1] to [8].

[10] In the InGaSe layer and the InSe layer, the ratio of the amount of Se element to the total amount of In and Ga elements (Se / (In+Ga)) is 1.25 or more and 1.75 or less. A method for manufacturing a solar cell as described in any one of [1] to [9].

[11] When the CuSe layer is formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is 2.0 or more and 3.0 or less. A method for manufacturing a solar cell as described in any one of [1] to

[10] .

[12] If the CuSe layer is not formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is 0.5 or more and 2.0 or less. A method for manufacturing a solar cell as described in any one of [1] to

[11] .

[13] In the crystallization step, heating is performed under an inert atmosphere at a temperature of 300°C to 600°C. A method for manufacturing a solar cell as described in any one of [1] to

[12] .

[14] The process further comprises a surface treatment step in which the surface of the light-absorbing layer is treated in a sulfur atmosphere at a temperature of 350°C to 600°C after the crystallization step. A method for manufacturing a solar cell as described in any one of [1] to

[13] .

[15] Manufactured by any one of the methods described in [1] to

[14] , In the aforementioned light-absorbing layer, the band gap in the section from the light-receiving surface to a depth of 200 nm is 1.1 eV or more and 1.4 eV or less. The band gap in the depth direction from 200 nm to 400 nm from the light-receiving surface is between 0.9 eV and 1.2 eV. The band gap in the depth direction from 400 nm onwards from the light-receiving surface is between 1.2 eV and 1.7 eV. Solar cell. [Examples]

[0076] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0077] <Method for manufacturing solar cells> A solar cell with a single electron transport layer, as shown in Figure 4, was fabricated. A 50 μm thick titanium foil was used as the substrate. A 600 nm thick first electrode layer containing metallic molybdenum was formed on this substrate using the sputtering method. On top of this, the light absorption layer of this embodiment was formed under the conditions described later. Here, when the crystal of the light absorption layer was formed, a 50 nm MoSe layer, which is a hole transport layer, was formed between the light absorption layer and the first electrode layer. Furthermore, the obtained light absorption layer was surface-treated by annealing in a sulfur atmosphere at a temperature of 500°C to 600°C for 3 to 30 minutes.

[0078] Next, an n-type electron transport layer containing titanium zinc oxide doped with hydrogen and sulfur elements was formed on the light absorption layer by sputtering to a thickness of 70 nm to 120 nm. A second 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 with a width of 50 μm was formed on its surface to finally obtain a solar cell.

[0079] In the following examples and comparative examples, solar cells were fabricated and evaluated using the same configuration as described above, except for the light-absorbing layer.

[0080] 1. Introduction of the InSe layer 1.1 Formation of the light-absorbing layer (Example 1) Example 1 employs the precursor structure shown in Figure 1. In Example 1, an InGaSe layer, a CuSe layer, and an InSe layer were formed by sputtering. In Example 1, the InGaSe layer, CuSe layer, and InSe layer were formed sequentially until they reached 900 nm, 800 nm, and 400 nm, respectively, to produce a precursor. This precursor was crystallized by heating it in a nitrogen atmosphere at 400°C to 600°C. After the crystallization step, a surface treatment was performed on the surface of the light-absorbing layer in a sulfur atmosphere at 500°C to 600°C to obtain a light-absorbing layer. <Conditions for film deposition by sputtering> ·Applied power: 0.5~3.0W / cm 2 • Deposition atmosphere: Argon • Pressure during film formation: 0.2 Pa to 3.0 Pa • Substrate temperature: Room temperature • Target species: The InGaSe layer is a mixture of In2Se3 and Ga2Se3, with Ga2Se3 being between 30% and 60%; the CuSe layer is pure CuSe2; and the InSe layer is pure In2Se3.

[0081] (Comparative Example 1) Comparative Example 1 was prepared by sputtering in the same manner as described in the non-patent document (Zhu, XL, & Wang, LK (2014), 13.6%-efficient Cu(In,Ga)Se2solar cell with absorber fabricated by RF sputtering of (In,Ga)2Se3 and CuSe targets, Solar Energy Materials and Solar Cells, 124, 21-25.), to form an InGaSe layer and a CuSe layer at 1700 nm and 400 nm, respectively, to create a precursor. This precursor was crystallized by heating it in a nitrogen atmosphere at 400°C to 600°C, and then, after the crystallization step, the surface of the light-absorbing layer was treated in a sulfur atmosphere at 500°C to 600°C to obtain the light-absorbing layer of Comparative Example 1.

[0082] 1.2. Evaluation The photoluminescence intensity (PL intensity) and band gap [eV] of the obtained light-absorbing layer were measured using a near-infrared fluorescence lifetime estimation system manufactured by Hamamatsu Photonics. The incident light wavelength used was 532 nm. The obtained results are shown in Table 1. Generally, a higher PL intensity suggests higher crystal quality, and the light-absorbing layer of Example 1 is suggested to have dramatically improved crystal quality. [Table 1]

[0083] 2. Embodiments of the Precursor 2.1 Formation of the light-absorbing layer (Examples 2 and 3) Examples 2 and 3 employ the precursor structures shown in Figures 2 and 3, respectively. In Examples 2 and 3, the same sputtering conditions as in Example 1 were used, but the layering order was changed. In Example 2, the CuSe layer was formed on the substrate side of the InSe layer, as in Example 1, with thicknesses of 900 nm, 400 nm, and 800 nm for the InGaSe, CuSe, and InSe layers, respectively. In Example 3, the InGaSe and CuSe layers were repeatedly formed, followed by the formation of an InSe layer. The thicknesses of the InGaSe, CuSe, and InSe layers were 450 nm, 200 nm, and 800 nm, respectively, with layers of the same compound stacked at the same thickness. The precursors of each example were crystallized by heating them in a nitrogen atmosphere at 400°C to 600°C, and then, after the crystallization process, the surface of the light-absorbing layer was treated in a sulfur atmosphere at 500°C to 600°C to obtain the light-absorbing layer.

[0084] 2.2. Evaluation of Battery Characteristics (Conversion efficiency) As described above, solar cells were fabricated, and the IV curve was obtained under standard test conditions (spectral spectrum AM1.5 light at an irradiance of 1 kW / m²). 2 Measurements were taken under test conditions where light was incident and the solar cell temperature was 25°C. The conversion efficiency and curve factor of each solar cell were calculated using the following formulas. The conversion efficiency is the value obtained by dividing the output at the optimal operating point in the IV curve (maximum output: Pmax) by the light energy E received by the solar cell, and the curve factor is the value obtained by dividing the above maximum output Pmax by the product of the open-circuit voltage (Voc) and the short-circuit current (Isc). The values ​​obtained from the measurements are shown in Table 2. Conversion efficiency (%) = (Pmax / E) × 100 Fill factor (%)=Pmax / (Voc×Isc) [Table 2]

[0085] 3. Amount of Group III elements in the InGaSe layer and InSe layer 3.1 Formation of the light-absorbing layer (Formation of light-absorbing layers with different amounts of Group III elements) In forming the light-absorbing layer in the same manner as in Example 1 above, the ratios of In and Ga elements in the InGaSe layer were defined as shown in Table 3 in order to examine the content of In and Ga elements in the InGaSe layer. Each row in Table 3 defines the ratio of Ga element to the total amount of In and Ga elements in the InGaSe layer. Each column defines the ratio of the total amount of In and Ga elements Y (Y / X) in the InGaSe layer to the amount of In element X in the InSe layer. As a result, the Ga / (In+Ga) value for the entire light-absorbing layer is as shown in Table 3. Of the conditions shown, the light-absorbing layers corresponding to the conditions numbered (1) to (6) were fabricated. [Table 3]

[0086] 3.2. Evaluation of Battery Characteristics (Relative ratio of conversion efficiency) Solar cells were fabricated using light-absorbing layers that met the above conditions (1) to (7), and their conversion efficiency was measured. The conversion efficiency was measured using the same method as described in 2.2. The conversion efficiency of the solar cells obtained under conditions (3) and (5) was the highest, and these were used as a baseline to determine the ratio of the conversion efficiencies measured under each condition. The results are shown in Table 4. [Table 4]

[0087] 4. Amount of Se in each layer 4.1 Formation of the light-absorbing layer To investigate the effect of the amount of Se element contained in the Group I CuSe layer and the Group III InGaSe and InSe layers, the molar ratio of Se element to Cu element in the CuSe layer (Se / Cu) was set as shown in Tables 5 and 6. Furthermore, the molar ratio of Se element to the total amount of Group III elements (In+Ga) in the InGaSe and InSe layers (Se / (In+Ga)) was set as shown in Tables 5 and 6. For each set molar ratio of S element, seven different light-absorbing layers with different compositions were fabricated by laminating the layers in the same manner as in Example 1 (Table 5) and by laminating the layers in the same manner as in Example 2 (Table 6) ((7)~(20)).

[0088] 4.2. Evaluation of Battery Characteristics (Conversion efficiency) Solar cells were fabricated using the light-absorbing layers (7) to (20), and the results of measuring the conversion efficiency are shown in Tables 5 and 6. [Table 5] [Table 6]

[0089] 5. Evaluation of the crystallinity of each layer In the same manner as the formation method for each layer in the precursor formation process of Example 1 described above, an InGaSe layer, a CuSe layer, and an InSe layer were formed on a Ti metal substrate, and X-ray diffraction measurements were performed. The measurements were performed using a Malvern Panalytical X-ray diffractometer and 2θ-θ measurements using Cu-Kα rays. The obtained diffraction measurement results are shown in Figure 5. In the CuSe layer, growth of the (111) and (220) planes was observed around 27° and 45°. However, no significant peaks indicating crystallinity were observed in the InGaSe and InSe layers.

[0090] 6. InSe layer formation temperature An InSe layer was formed on a Ti metal substrate using the same formation method as in the precursor formation step of Example 1 described above, except that the surface temperature of the substrate was changed. Film deposition was performed four times, with the substrate surface temperature set to room temperature (RT), 200°C, 250°C, and 300°C. X-ray diffraction measurements were performed using the X-ray diffractometer and measurement conditions described above. The results of the diffraction measurements are shown in Figure 6. From the results shown in Figure 6, it was found that the higher the surface temperature of the substrate, the higher the crystallinity of the formed InSe layer. Furthermore, similar tests were conducted on the InGaSe layer, and the results showed that crystallization was more likely to occur when an even higher surface temperature was set compared to the InSe layer. [Explanation of symbols]

[0091] 10...solar cell, 101...grid electrode, 102...second electrode layer, 103...electron transport layer, 104...light absorption layer, 105...hole transport layer, 106...first electrode layer, 107...substrate.

Claims

1. A precursor formation step comprising forming a precursor having an InGaSe layer, a CuSe layer, and an InSe layer, The process includes a crystallization step of obtaining a light-absorbing layer by heating the precursor, In the precursor formation step, the InGaSe layer and the InSe layer are amorphous. A method for manufacturing solar cells.

2. In the precursor formation step, the InSe layer is formed on the light-receiving surface side of the InGaSe layer. A method for manufacturing a solar cell according to claim 1.

3. In the precursor formation step, the InSe layer is formed on the side closest to the light-receiving surface. A method for manufacturing a solar cell according to claim 1.

4. In the precursor formation step, two or more layers of the InGaSe layer and the CuSe layer are formed. A method for manufacturing a solar cell according to claim 1.

5. In the InGaSe layer, the ratio of the amount of Ga element to the total amount of In and Ga elements (Ga / (In+Ga)) is 0.3 or more and 0.6 or less. A method for manufacturing a solar cell according to claim 1.

6. The ratio of the total amount of substance Y (Y / X) of In and Ga elements in the InGaSe layer to the amount of substance X of In elements in the InSe layer is 1.0 or more and 1.5 or less. A method for manufacturing a solar cell according to claim 1.

7. In the aforementioned precursor, The ratio of the amount of Ga element to the total amount of In element and Ga element (Ga / (In+Ga)) is 0.15 or more and 0.40 or less. The ratio of the amount of Cu to the total amount of In and Ga (Cu / (In+Ga)) is 0.75 or greater and 0.95 or less. The ratio of the amount of Se element to the total amount of Cu, In, and Ga elements (Se / (Cu+In+Ga)) is 1.0 or greater. A method for manufacturing a solar cell according to claim 1.

8. In the InGaSe layer and the InSe layer, the ratio of the amount of Se element to the total amount of In and Ga elements (Se / (In+Ga)) is 1.25 or more and 1.75 or less. A method for manufacturing a solar cell according to claim 1.

9. When the CuSe layer is formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is 2.0 or more and 3.0 or less. A method for manufacturing a solar cell according to claim 1.

10. If the CuSe layer is not formed on the outermost surface of the precursor, the ratio of the amount of Se element to the amount of Cu element (Se / Cu) in the CuSe layer is 0.5 or more and 2.0 or less. A method for manufacturing a solar cell according to claim 1.

11. In the crystallization step, heating is performed under an inert atmosphere at a temperature of 300°C to 600°C. A method for manufacturing a solar cell according to claim 1.

12. The process further comprises a surface treatment step in which the surface of the light-absorbing layer is treated in a sulfur atmosphere at a temperature of 350°C to 600°C after the crystallization step. A method for manufacturing a solar cell according to claim 1.

13. Manufactured by the method described in any one of claims 1 to 12, In the aforementioned light-absorbing layer, the band gap in the section from the light-receiving surface to a depth of 200 nm is 1.1 eV or more and 1.4 eV or less. The band gap in the section from 200 nm to 400 nm in the depth direction from the light-receiving surface side is 0.9 eV or more and 1.2 eV or less. The band gap in the section from 400 nm in the depth direction from the light-receiving surface is 1.2 eV to 1.7 eV. Solar cell.

Images