Thin-film solar cells and methods for manufacturing thin-film solar cells

Abstract

We provide thin-film solar cells with a high degree of design flexibility. [Solution] The thin-film solar cell 1 is a thin-film solar cell in which a first electrode layer 21, a photoelectric conversion layer 30, and a second electrode layer 22 are sequentially stacked on a transparent substrate 10, and comprises a plurality of cylindrical insulating tubes 40 extending in the stacking direction, and a plurality of columnar conductive columns 21A located inside each of the plurality of insulating tubes 40 and extending in the stacking direction. The plurality of insulating tubes 40 and the plurality of conductive columns 21A are arranged in an island-like manner in the photoelectric conversion layer 30 and the second electrode layer 22, one end of the plurality of conductive columns 21A is connected to the first electrode layer 21, and the other end of the plurality of conductive columns 21A is exposed to the second electrode layer 22 side, and in a plan view on the second electrode layer 22 side, the second electrode layer 22 and the plurality of conductive columns 21A form a sea-island structure, and each of the plurality of conductive columns 21A is insulated from the photoelectric conversion layer 30 and the second electrode layer 22 by each of the plurality of insulating tubes 40.

Description

TECHNICAL FIELD

[0001] The present invention relates to a thin-film solar cell and a method for manufacturing the thin-film solar cell. BACKGROUND ART

[0002] As solar cells, crystalline silicon solar cells using a crystalline silicon substrate in the photoelectric conversion section, and thin-film solar cells using an inorganic thin film such as an amorphous silicon thin film in the photoelectric conversion section are known. Further, as a thin-film solar cell, a perovskite thin-film solar cell using a perovskite thin film, which is an organic thin film (specifically, an organic / inorganic hybrid thin film), in the photoelectric conversion section is known. Patent Document 1 discloses such a thin-film solar cell.

[0003] The thin-film solar cell has, in order from the transparent substrate side, a first electrode layer, a first carrier transport layer, a photoelectric conversion layer, a second carrier transport layer, and a second electrode layer. Further, Patent Document 1 discloses that the thin-film solar cell has an integrated structure in which a plurality of sub-cells, which are divided in the integration direction on the transparent substrate and extend in a direction intersecting the integration direction, are connected in series in the integration direction. With such an integrated structure, it is possible to realize a solar cell with relatively low current loss at a desired voltage even when the area is increased. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2014-135358 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] In thin-film solar cells with this type of integrated structure, multiple divided subcells are connected in series, and current is drawn from both ends in the integration direction. In this case, to reduce current loss in the DC connection, the size of the multiple subcells (area: i.e., width in the direction intersecting the integration direction and length in the integration direction) is made the same. Due to these constraints, the multiple subcells inevitably become rectangular in shape, and the thin-film solar cell becomes rectangular in shape.

[0006] The present invention aims to provide a thin-film solar cell with a high degree of freedom in shape and a method for manufacturing a thin-film solar cell. [Means for solving the problem]

[0007] The thin-film solar cell according to the present invention is a thin-film solar cell in which a first electrode layer, a photoelectric conversion layer, and a second electrode layer are sequentially laminated on a transparent substrate, and comprises a plurality of cylindrical insulating cylinders extending in the lamination direction, and a plurality of columnar conductive columns located inside each of the plurality of insulating cylinders and extending in the lamination direction. The plurality of insulating cylinders and the plurality of conductive columns are arranged in an island-like manner in the photoelectric conversion layer and the second electrode layer, one end of the plurality of conductive columns is connected to the first electrode layer, and the other end of the plurality of conductive columns is exposed to the second electrode layer side, and in a plan view on the second electrode layer side, the second electrode layer and the plurality of conductive columns form a sea-island structure, and each of the plurality of conductive columns is insulated from the photoelectric conversion layer and the second electrode layer by each of the plurality of insulating cylinders.

[0008] A method for manufacturing a thin-film solar cell according to the present invention includes: a first electrode layer formation step of forming a first electrode layer on a transparent substrate; an insulator cylinder arrangement step of arranging a plurality of cylindrical insulator cylinders extending in the stacking direction in an island-like configuration on the first electrode layer; a conductor column arrangement step of arranging a plurality of columnar conductive columns extending in the stacking direction inside each of the plurality of insulator cylinders; a photoelectric conversion layer formation step of forming a photoelectric conversion layer on the first electrode layer; and a second electrode layer formation step of forming a second electrode layer on the photoelectric conversion layer. In the conductor column arrangement step, one end of the plurality of conductive columns is connected to the first electrode layer. In the photoelectric conversion layer formation step, the photoelectric conversion layer and the plurality of conductive columns form an island-sea structure, and each of the plurality of conductive columns is insulated from the photoelectric conversion layer by each of the plurality of insulator cylinders. In the second electrode layer formation step, the other end of each of the plurality of conductive columns is exposed to the second electrode layer, the second electrode layer and the plurality of conductive columns form a sea-island structure, and each of the plurality of conductive columns is insulated from the second electrode layer by each of the plurality of insulating cylinders. [Effects of the Invention]

[0009] According to the present invention, the degree of freedom in shape can be increased in thin-film solar cells. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic plan view showing the solar cell according to this embodiment from the back side. [Figure 2] Figure 1 is a cross-sectional view of a solar cell, specifically a schematic cross-sectional view along the line II-II. [Figure 3A] This figure shows the first electrode layer formation step in the method for manufacturing a solar cell according to this embodiment. [Figure 3B] This figure shows the insulator cylinder arrangement step in the solar cell manufacturing method according to this embodiment. [Figure 3C] This figure shows the conductive column arrangement process in the manufacturing method of a solar cell according to this embodiment. [Figure 3D] This figure shows the photoelectric conversion layer formation process in the method for manufacturing a solar cell according to this embodiment. [Figure 3E] This figure shows the second electrode layer formation step in the method for manufacturing a solar cell according to this embodiment. [Modes for carrying out the invention]

[0011] An example of an embodiment of the present invention will be described below with reference to the attached drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals. Also, for convenience, hatching and component reference numerals may be omitted, in which case refer to other drawings.

[0012] (Solar cells) Figure 1 is a schematic plan view of the solar cell according to this embodiment, shown from the back side, and Figure 2 is a schematic cross-sectional view of the solar cell shown in Figure 1, taken along the line II-II. In the following, a thin-film solar cell equipped with a perovskite thin-film photoelectric conversion layer is given as an example of solar cell 1. However, this embodiment is not limited to this and can be applied to various thin-film solar cells equipped with various photoelectric conversion layers such as inorganic semiconductor thin films, organic semiconductor thin films, or organic-inorganic hybrid semiconductor thin films, for example amorphous silicon-based or perovskite-based.

[0013] The solar cell 1 comprises a substrate 10, a first electrode layer 21, a photoelectric conversion layer 30, a second electrode layer 22, and a plurality of conductive columns 21A and an insulating cylinder 40. The photoelectric conversion layer 30 includes a first carrier transport layer 31, a second carrier transport layer 32, and a photoelectric conversion layer 33.

[0014] The solar cell 1 may have its light-receiving surface on the substrate 10 side, i.e., the first electrode layer 21 side, or it may have its light-receiving surface on the side opposite to the substrate 10, i.e., the second electrode layer 22 side. Alternatively, both sides, i.e., the side opposite to the substrate 10, i.e., the side opposite to the substrate 10, may function as light-receiving surfaces, such as the side with the first electrode layer 21 and the side with the second electrode layer 22.

[0015] The substrate 10 may be a transparent substrate having insulating properties and light transmittance, or may be a transparent film further having flexibility. The transparent substrate is not particularly limited, and examples thereof include substrates made of materials such as glass or resin. The transparent film is not particularly limited, and examples thereof include resin films made of materials such as polyimide, polyethylene naphthalate, and polyethylene terephthalate.

[0016] The first electrode layer 21 is formed on the substrate 10, and functions as an anode or a cathode. The first electrode layer 21 is composed of a transparent conductive film (Transparent Conductive Oxides: TCO) having conductivity and light transmittance. The material of the first electrode layer 21 is not particularly limited, and transparent conductive metal oxides, for example, indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof and the like are used. Among these, indium-based composite oxides containing indium oxide as a main component are preferable. From the viewpoint of high conductivity and transparency, indium oxide is particularly preferable. Furthermore, in order to ensure reliability or higher conductivity, it is preferable to add a dopant to the indium oxide. Examples of the dopant include Sn, W, Zn, Ti, Ce, Zr, Mo, Al, Ga, Ge, As, Si, or S and the like. For example, ITO (Indium Tin Oxide) in which tin is added to indium oxide is widely known.

[0017] Note that when the substrate 10 side, that is, the first electrode layer 21 side is the light-receiving surface, the first electrode layer 21 may include a grid-shaped or slit-shaped metal electrode layer. Alternatively, when the side opposite to the substrate 10, that is, the second electrode layer 22 side is the light-receiving surface, the first electrode layer 21 may include, for example, a planar metal electrode layer on the substrate 10 side. The material of the metal electrode layer is not particularly limited, and examples thereof include Ag, Au, and Cu.

[0018] The first carrier transport layer 31 is formed on the first electrode layer 21, and functions as a Hole Transfer Layer (HTL) or an Electron Transport Layer (ETL). The first carrier transport layer 31 is made of a light-transmissive semiconductor material.

[0019] When the first carrier transport layer 31 is a Hole Transfer Layer (HTL), the first carrier transport layer 31 transports holes (first carriers) among the carriers generated by photoelectric conversion in the photoelectric conversion layer 33 to the first electrode layer 21. The material of the first carrier transport layer 31 serving as the Hole Transfer Layer (HTL) is not particularly limited, and examples thereof include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and poly(3,4-ethylenedioxythiophene) (PEDOT), fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), carbazole derivatives such as polyvinylcarbazole, triphenylamine derivatives, diphenylamine derivatives, polysilane derivatives, polyaniline derivatives, and the like.

[0020] On the other hand, when the first carrier transport layer 31 is an Electron Transport Layer (ETL), the first carrier transport layer 31 transports electrons (first carriers) among the carriers generated by photoelectric conversion in the photoelectric conversion layer 33 to the first electrode layer 21. The material of the first carrier transport layer 31 serving as the Electron Transport Layer (ETL) is not particularly limited, and examples thereof include metal oxides such as titanium oxide, zinc oxide, niobium oxide, zirconium oxide, and aluminum oxide.

[0021] The photoelectric conversion layer 33 is formed on the first carrier transport layer 31. Examples of the photoelectric conversion layer 33 include an inorganic semiconductor thin film or an organic semiconductor thin film (specifically, an organic-inorganic hybrid semiconductor thin film). Examples of the inorganic semiconductor thin film include an amorphous silicon thin film and the like. Examples of the organic-inorganic hybrid semiconductor thin film include a perovskite thin film containing a photosensitive material having a perovskite crystal structure.

[0022] For example, a perovskite thin film contains a perovskite compound. The perovskite compound is not particularly limited, but for example, a compound represented by ABX3 can be used, which contains an organic atomic group A comprising at least one of monovalent organic ammonium ions and amidinium-based ions, a metal atom B that generates a divalent metal ion, and a halogen atom X comprising at least one of iodide ions I, bromide ions Br, chloride ions Cl, and fluoride ions F. Furthermore, substituting some or all of the organic atomic group A with an alkali metal Am has also been considered, and such perovskite compounds are not excluded from the present invention.

[0023] Methods for fabricating perovskite thin films include wet processes such as printing, coating, or solution methods, and dry processes such as vapor deposition.

[0024] The second carrier transport layer 32 is formed on the photoelectric conversion layer 33 and functions as an electron transport layer (ETL) or hole transport layer (HTL). The second carrier transport layer 32 is made of a light-transmitting semiconductor material.

[0025] When the second carrier transport layer 32 is an electron transport layer (ETL), the second carrier transport layer 32 transports electrons (second carriers) from the carriers generated by photoelectric conversion in the photoelectric conversion layer 33 to the second electrode layer 22. The material of the second carrier transport layer 32 as an electron transport layer (ETL) is not particularly limited, but examples include metal oxides such as titanium oxide, zinc oxide, niobium oxide, zirconium oxide, and aluminum oxide.

[0026] On the other hand, if the second carrier transport layer 32 is a hole transport layer (HTL), the second carrier transport layer 32 transports holes (second carriers) from the carriers generated by photoelectric conversion in the photoelectric conversion layer 33 to the second electrode layer 22. The material of the second carrier transport layer 32 as a hole transport layer (HTL) is not particularly limited, but examples include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and poly(3,4-ethylenedioxythiophene) (PEDOT), fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), carbazole derivatives such as polyvinylcarbazole, triphenylamine derivatives, diphenylamine derivatives, polysilane derivatives, and polyaniline derivatives.

[0027] The second electrode layer 22 is formed on the second carrier transport layer 32 and functions as a cathode or anode. When the substrate 10 side, i.e., the first electrode layer 21 side, is the light-receiving surface, the second electrode layer 22 may include, for example, a planar metal electrode layer on the substrate 10 side. Alternatively, when the side opposite to the substrate 10, i.e., the second electrode layer 22 side, is the light-receiving surface, the second electrode layer 22 may include a transparent conductive oxide (TCO) that is conductive and light-transmitting, and may also include a grid-like or slit-like metal electrode layer.

[0028] The material for the transparent conductive film TCO is not particularly limited, but transparent conductive metal oxides such as indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof can be used. Among these, indium-based composite oxides mainly composed of indium oxide are preferred. Indium oxide is particularly preferred from the viewpoint of high conductivity and transparency. Furthermore, it is preferable to add a dopant to the indium oxide to ensure reliability or higher conductivity. Examples of dopants include Sn, W, Zn, Ti, Ce, Zr, Mo, Al, Ga, Ge, As, Si, or S. For example, ITO (Indium Tin Oxide), in which tin is added to indium oxide, is widely known. The material for the metal electrode layer is not particularly limited, but examples include Ag, Au, and Cu.

[0029] With this configuration, the solar cell 1 generates a current corresponding to the light incident from the substrate 10 side, i.e., the first electrode layer 21 side, or the side opposite to the substrate 10, i.e., the second electrode layer 22 side, and outputs it to the first electrode layer 21 and the second electrode layer 22.

[0030] The insulating cylinder 40 is cylindrical in shape and extends in the lamination direction. The material of the insulating cylinder 40 is not particularly limited, but resin is one example.

[0031] The conductive column 21A is located inside the insulating cylinder 40 and has a columnar shape extending in the stacking direction. One end of the conductive column 21A is connected to the first electrode layer 21, and the other end of the conductive column 21A is exposed to the second electrode layer 22. The material of the conductive column 21A is not particularly limited, but examples include metals such as Ag, Au, and Cu. For example, the conductive column 21A is formed from a conductive paste containing metal particles and resin.

[0032] The insulating cylinder 40 and the conductive column 21A are arranged in an island-like configuration in the photoelectric conversion layer 30 and the second electrode layer 22. In a plan view from the second electrode layer 22 side, the second electrode layer 22 and the conductive column 21A form a sea-island structure. The conductive column 21A is insulated from the photoelectric conversion layer 30 and the second electrode layer 22 by the insulating cylinder 40.

[0033] (Method of manufacturing solar cells) Next, the method for manufacturing a solar cell according to this embodiment will be described with reference to Figures 3A to 3E. Figure 3A is a diagram showing the first electrode layer formation process in the method for manufacturing a solar cell according to this embodiment, Figure 3B is a diagram showing the insulator cylinder arrangement process in the method for manufacturing a solar cell according to this embodiment, and Figure 3C is a diagram showing the conductor column arrangement process in the method for manufacturing a solar cell according to this embodiment. Figure 3D is a diagram showing the photoelectric conversion layer formation process in the method for manufacturing a solar cell according to this embodiment, and Figure 3E is a diagram showing the second electrode layer formation process in the method for manufacturing a solar cell according to this embodiment. The photoelectric conversion layer formation process includes a first carrier transport layer formation process, a photoelectric conversion layer formation process, and a second carrier transport layer formation process.

[0034] First, as shown in Figure 3A, a transparent conductive film is formed on the substrate 10 as the first electrode layer 21 (first electrode layer formation step). Known techniques such as CVD (chemical vapor deposition) or PVD (physical vapor deposition) are used as methods for forming the transparent conductive film.

[0035] Next, as shown in Figure 3B, a plurality of cylindrical insulating tubes 40 extending in the stacking direction are arranged in an island-like manner on the first electrode layer 21 (insulating tube arrangement step). The method for forming the insulating tubes 40 is not particularly limited, but for example, a printing method is used to form the plurality of insulating tubes 40 in an island-like manner.

[0036] Next, as shown in Figure 3C, a plurality of columnar conductive columns 21A extending in the stacking direction are placed inside each of the plurality of insulating cylinders 40 (conductive column placement step). The method for forming the conductive columns 21A is not particularly limited, but for example, conductive paste is injected into each of the insulating cylinders 40 to form the plurality of conductive columns 21A. In this way, one end of the conductive column 21A is connected to the first electrode layer 21.

[0037] Next, as shown in Figure 3D, a first carrier transport layer 31 is formed on the first electrode layer 21 (first carrier transport layer formation step). The method for forming the first carrier transport layer 31 is not particularly limited, but examples include dry processes such as CVD or PVD, or wet processes such as coating or printing.

[0038] Next, a photoelectric conversion layer 33 is formed on the first carrier transport layer 31 (photoelectric conversion layer formation step). The method for forming the photoelectric conversion layer 33 is not particularly limited, but examples include wet processes such as printing, coating, or solution methods, or dry processes such as vapor deposition.

[0039] Next, a second carrier transport layer 32 is formed on the photoelectric conversion layer 33 (second carrier transport layer formation step). The method for forming the second carrier transport layer 32 is not particularly limited, but examples include dry processes such as CVD, PVD, or vapor deposition, or wet processes such as coating or printing. In this way, the photoelectric conversion layer 30 and the plurality of conductive columns 21A form a sea-island structure, and the conductive columns 21A are insulated from the photoelectric conversion layer 30 by the insulating cylinder 40.

[0040] Next, as shown in Figure 3E, a second electrode layer 22 is formed on the second carrier transport layer 32. The method for forming the second electrode layer 22 is not particularly limited, but examples include dry processes such as CVD, PVD, or vapor deposition, or wet processes such as printing or coating. In this way, the other ends of the multiple conductive columns 21A are exposed to the second electrode layer 22 side, forming a sea-island structure between the second electrode layer 22 and the multiple conductive columns 21A, and each conductive column 21A is insulated from the second electrode layer 22 by an insulating cylinder 40.

[0041] Based on the above, the thin-film solar cell 1 of this embodiment, as shown in Figures 1 and 2, is obtained.

[0042] As described above, the thin-film solar cell 1 of this embodiment comprises a plurality of cylindrical insulating cylinders 40 and a plurality of columnar conductive columns 21A located inside each of the plurality of insulating cylinders 40. Multiple insulating cylinders 40 and multiple conductive columns 21A are arranged in an island-like manner in the photoelectric conversion layer 30 and the second electrode layer 22. One end of each of the multiple conductive columns 21A is connected to the first electrode layer 21, and the other end of each of the multiple conductive columns 21A is exposed to the second electrode layer 22. In a plan view of the second electrode layer 22, the second electrode layer 22 and the multiple conductive columns 21A form a sea-island structure. Each of the multiple conductive columns 21A is insulated from the photoelectric conversion layer 30 and the second electrode layer 22 by each of the multiple insulating cylinders 40.

[0043] As a result, as shown in Figure 2, two electrodes 21A and 22 are arranged on one side, and carrier extraction is possible at multiple points A and B, thus increasing the degree of freedom in the shape of the thin-film solar cell 1. For example, the thin-film solar cell 1 is not limited to a rectangular shape, but can be made into various shapes such as a circular shape.

[0044] Furthermore, since the process of forming an integrated structure is unnecessary, the manufacturing process can be simplified.

[0045] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. For example, the embodiments described above described a thin-film solar cell comprising a photoelectric conversion layer composed of a perovskite thin film. However, this embodiment is not limited thereto and is applicable to various thin-film solar cells comprising various photoelectric conversion layers composed of inorganic semiconductor thin films, organic semiconductor thin films, or organic-inorganic hybrid semiconductor thin films, such as amorphous silicon-based or perovskite-based. [Explanation of Symbols]

[0046] 1 Solar cells (thin film solar cells) 10 Base material (transparent substrate) 21 1st electrode layer 21A conductor pillar 22 Second electrode layer 30 Photoelectric conversion layer 31. First Carrier Transport Layer 32. Second Carrier Transport Layer 33 Photoelectric conversion layer 40 Insulator tube

Claims

1. A thin-film solar cell in which a first electrode layer, a photoelectric conversion layer, and a second electrode layer are sequentially laminated on a transparent substrate, Multiple cylindrical insulating tubes extending in the stacking direction, A plurality of columnar conductive columns are located inside each of the plurality of insulating cylinders and extend in the stacking direction, Equipped with, The plurality of insulating cylinders and the plurality of conductive columns are arranged in an island-like manner in the photoelectric conversion layer and the second electrode layer. One end of each of the plurality of conductive columns is connected to the first electrode layer, and the other end of each of the plurality of conductive columns is exposed to the second electrode layer. In a plan view of the second electrode layer, the second electrode layer and the plurality of conductive columns form a sea-island structure. Each of the plurality of conductive columns is insulated from the photoelectric conversion layer and the second electrode layer by each of the plurality of insulating cylinders. Thin film solar cell.

2. A first electrode layer formation step in which a first electrode layer is formed on a transparent substrate, An insulating cylinder arrangement step is to arrange a plurality of cylindrical insulating cylinders extending in the stacking direction in an island-like manner on the first electrode layer, A conductive column arrangement step involves arranging a plurality of columnar conductive columns extending in the stacking direction inside each of the plurality of insulating cylinders, A photoelectric conversion layer formation step, in which a photoelectric conversion layer is formed on the first electrode layer, A second electrode layer formation step is performed to form a second electrode layer on the aforementioned photoelectric conversion layer, Includes, In the conductive column arrangement step, one end of the plurality of conductive columns is connected to the first electrode layer. In the photoelectric conversion layer formation step, The photoelectric conversion layer and the plurality of conductive columns form a sea-island structure. Each of the plurality of conductive columns is insulated from the photoelectric conversion layer by each of the plurality of insulating cylinders. In the aforementioned second electrode layer formation step, The other end of each of the plurality of conductive columns is exposed to the second electrode layer side. The second electrode layer and the plurality of conductive columns form a sea-island structure. Each of the plurality of conductive columns is insulated from the second electrode layer by each of the plurality of insulating cylinders. A method for manufacturing thin-film solar cells.

3. The method for manufacturing a thin-film solar cell according to claim 2, wherein in the insulating cylinder arrangement step, the plurality of insulating cylinders are formed in an island shape using a printing method.

4. The method for manufacturing a thin-film solar cell according to claim 2 or 3, wherein in the conductive column arrangement step, conductive paste is injected into each of the plurality of insulating cylinders to form the plurality of conductive columns.

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