Flexible Solar Cells

Abstract

The present invention provides a flexible solar cell that has excellent flame retardancy in the planar direction while suppressing deterioration in power generation performance. [Solution] A flexible solar cell having a power generation section, a blocking layer in contact with at least one entire surface of the power generation section, and a sealing material that seals the entire laminate consisting of the power generation section and the blocking layer, wherein the power generation section has an electrode, a photoelectric conversion layer, and a counter electrode, the photoelectric conversion layer contains an organic-inorganic perovskite compound, the sealing material has a flame-retardant portion that contains a flame-retardant material and a non-flame-retardant portion that does not contain the flame-retardant material, the flame-retardant portion is disposed on the side of the blocking layer that is not in contact with the power generation section, and the power generation section is in contact with the non-flame-retardant portion and not in contact with the flame-retardant portion,

Description

Technical Field

[0001] The present invention relates to a flexible solar cell.

Background Art

[0002] Conventionally, as a solar cell, a laminate in which an N-type semiconductor layer and a P-type semiconductor layer are arranged between opposing electrodes has been actively developed, and inorganic semiconductors such as silicon are mainly used as the N-type and P-type semiconductors. However, such an inorganic solar cell has problems in that it is costly to manufacture, difficult to increase in size, and limited in its range of use. Therefore, in recent years, perovskite solar cells using an organic-inorganic perovskite compound having a perovskite structure using lead, tin, etc. as a central metal in a photoelectric conversion layer have attracted attention (for example, Patent Document 1, Non-Patent Document 1). Perovskite solar cells can be expected to have high photoelectric conversion efficiency and can be manufactured by a printing method, so that the manufacturing cost can be significantly reduced.

[0003] On the other hand, in recent years, flexible solar cells using a heat-resistant polymer material such as polyimide or polyester or a metal foil as a base material have come to be noticed. Flexible solar cells have advantages such as ease of transportation and construction due to thinning and weight reduction, and resistance to impact. For example, they are manufactured by laminating a plurality of layers such as a photoelectric conversion layer having a function of generating an electric current when irradiated with light in a thin film form on a flexible base material. Further, a sealing sheet is laminated and sealed on the upper and lower surfaces of the flexible solar cell as necessary. For example, Patent Document 2 describes a substrate for a semiconductor device including a sheet-like aluminum substrate, and an organic thin film solar cell including this substrate for a semiconductor device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Document

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In such flexible solar cells, a lot of organic materials are used to impart transparency and flexibility. Since organic materials are more flammable than inorganic materials, flexible solar cells require more fire protection measures than conventional solar cells. However, although some conventional solar cells have been proposed to have flame retardancy in the thickness direction of the solar cell, the flame retardancy in the planar direction (the plane direction perpendicular to the thickness direction) has not been sufficiently studied. Especially in recent years, due to the progress of manufacturing technology, the area per unit of flexible solar cells has been increasing. Therefore, if the flame retardancy in the planar direction is low, not only will a large number of solar cells burn out, but the risk of fire spreading to other areas will also increase. Thus, the flame retardancy in the planar direction has become more important.

[0007] To address this problem, as a method for enhancing the flame retardancy of flexible solar cells, a method of adding a flame retardant material to the encapsulant that protects the power generation part of the flexible solar cell has been proposed. Hydrocarbon-based resins are preferably used as the encapsulant from the perspective of low moisture permeability, but they have the property of being highly flammable. Therefore, by adding a flame retardant material to the highly flammable encapsulant, the flame retardancy can be improved in each stage, and the flame retardancy in the planar direction can also be enhanced. However, among the flexible solar cells with a flame retardant material added to the encapsulant, there are some whose power generation performance deteriorates.

[0008] An object of the present invention is to provide a flexible solar cell that is excellent in flame retardancy in the planar direction while suppressing a decrease in power generation performance.

Means for Solving the Problems

[0009] The present invention includes the following disclosures 1 to 4. Hereinafter, the present invention will be described in detail. [Disclosure 1] A flexible solar cell having a power generation part, a block layer in contact with at least one entire surface of the power generation part, and a sealing material for sealing the entire laminate composed of the power generation part and the block layer, wherein the power generation part has an electrode, a photoelectric conversion layer, and a counter electrode, the photoelectric conversion layer contains an organic-inorganic perovskite compound, the sealing material has a flame-retardant part containing a flame-retardant material and a non-flame-retardant part not containing the flame-retardant material, the flame-retardant part is disposed on the surface side of the block layer not in contact with the power generation part, the power generation part is in contact with the non-flame-retardant part and not in contact with the flame-retardant part A flexible solar cell characterized by the above. [Disclosure 2] The flexible solar cell according to Disclosure 1, wherein the flame-retardant material contains a chlorine atom. [Disclosure 3] The flexible solar cell according to Disclosure 1 or 2, wherein the material constituting the block layer contains polyethylene terephthalate, polyethylene, polypropylene, polyethylene naphthalate, polymethyl methacrylate, polystyrene, or polycarbonate. [Disclosure 4] The flexible solar cell according to any one of Disclosures 1 to 3, wherein the interface of the laminate is in contact with only the non-flame-retardant part.

[0010] The flexible solar cell of the present invention has a power generation part, and the power generation part has an electrode, a photoelectric conversion layer, and a counter electrode. The power generation part is a part that converts sunlight into electric power, and is composed of an electrode, a counter electrode, a photoelectric conversion layer, an electron transport layer, a hole transport layer, etc., and has at least an electrode, a photoelectric conversion layer, and a counter electrode. In this specification, the term "layer" not only refers to a layer with a distinct boundary, but also a layer with a concentration gradient where the contained elements change gradually. The elemental analysis of the layer can be carried out, for example, by performing FE-TEM / EDS line analysis measurement on the cross-section of the solar cell to confirm the elemental distribution of specific elements. Also, in this specification, the term "layer" not only refers to a flat thin film layer, but also a layer that can form a complex intertwined structure together with other layers. Further, in this specification, "upper" refers to the direction on the light incident surface side in the thickness direction of the flexible solar cell, and "lower" refers to the opposite direction of the upper, that is, the direction on the installation surface side.

[0011] The materials of the above electrode and counter electrode are not particularly limited. For example, FTO (fluorine-doped tin oxide), ITO (tin-doped indium oxide), AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al 2 O 3 mixture, Al / LiF mixture, etc. can be mentioned. Also, gold, silver, titanium, molybdenum, tantalum, tungsten, carbon, nickel, chromium, etc. can be mentioned. These materials may be used alone or in combination of two or more.

[0012] The thickness of the above electrode and counter electrode is not particularly limited, but the preferable lower limit is 10 nm and the preferable upper limit is 1000 nm. If the above thickness is 10 nm or more, the resistance can be suppressed while exerting the function as an electrode. If the above thickness is 1000 nm or less, the light transmittance can be further improved. The more preferable lower limit of the thickness of the above electrode and counter electrode is 50 nm, and the more preferable upper limit is 500 nm.

[0013] The above photoelectric conversion layer contains an organic-inorganic perovskite compound. The above-mentioned organic-inorganic perovskite compound is represented by the general formula AMX (where A is an organic base compound and / or an alkali metal, M is a lead or tin atom, and X is a halogen atom). The solar cell containing the above-mentioned organic-inorganic perovskite compound is also called an organic-inorganic hybrid solar cell. By using the above-mentioned organic-inorganic perovskite compound in the above-mentioned photoelectric conversion layer, the photoelectric conversion efficiency of the flexible solar cell can be improved.

[0014] The above-mentioned A is an organic base compound and / or an alkali metal. Specific examples of the above-mentioned organic base compound include, for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, formamidine, acetamidine, guanidine, imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, carbazole and their ions (for example, methylammonium (CH 3 NH 3 ) etc.) and phenethylammonium etc. Among them, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, formamidine, acetamidine and their ions and phenethylammonium are preferred, and methylamine, ethylamine, propylamine, formamidine and their ions are more preferred. Examples of the above-mentioned alkali metal include lithium, sodium, potassium, rubidium, cesium and the like.

[0015] The above-mentioned M is a metal atom and is a lead or tin atom. These metal atoms may be used alone or in combination of two or more.

[0016] X above is a halogen atom, and examples of the halogen atom include chlorine, bromine, iodine, sulfur, selenium, etc. These halogen atoms may be used alone or in combination of two or more. By containing halogen in the structure, the above-mentioned organic-inorganic perovskite compound becomes soluble in an organic solvent, enabling its application to an inexpensive printing method or the like. Among them, since the energy band gap of the above-mentioned organic-inorganic perovskite compound becomes narrow, X is preferably iodine.

[0017] The above-mentioned organic-inorganic perovskite compound preferably has a cubic crystal structure in which a metal atom M is at the body center, an organic base compound or an alkali metal A is at each vertex, and a halogen atom X is at the face center. Although the details are not clear, having the above structure enables the orientation of the octahedrons in the crystal lattice to easily change. Therefore, it is presumed that the mobility of electrons in the above-mentioned organic-inorganic perovskite compound increases, improving the photoelectric conversion efficiency of the solar cell.

[0018] The above-mentioned organic-inorganic perovskite compound is preferably a crystalline semiconductor. A crystalline semiconductor means a semiconductor in which the X-ray scattering intensity distribution is measured and scattering peaks can be detected. Since the above-mentioned organic-inorganic perovskite compound is a crystalline semiconductor, the mobility of electrons in the above-mentioned organic-inorganic perovskite compound increases, improving the photoelectric conversion efficiency of the flexible solar cell.

[0019] Also, the crystallinity can be evaluated as an index of crystallization. The crystallinity can be obtained by separating the scattering peak derived from the crystalline part and the halo derived from the amorphous part detected by measuring the X-ray scattering intensity distribution by fitting, obtaining the intensity integration of each, and calculating the ratio of the crystalline part in the whole. The preferable lower limit of the crystallinity of the above-mentioned organic-inorganic perovskite compound is 30%. When the crystallinity is 30% or more, the mobility of electrons in the above-mentioned organic-inorganic perovskite compound increases, and the photoelectric conversion efficiency of the solar cell improves. The more preferable lower limit of the crystallinity is 50%, and the further preferable lower limit is 70%. In addition, as a method for increasing the crystallinity of the above-mentioned organic-inorganic perovskite compound, for example, thermal annealing, irradiation with intense light such as a laser, plasma irradiation, etc. can be mentioned.

[0020] The above-mentioned photoelectric conversion layer may further contain an organic semiconductor or an inorganic semiconductor in addition to the above-mentioned organic-inorganic perovskite compound as long as the effects of the present invention are not impaired. Here, the organic semiconductor or inorganic semiconductor mentioned may serve as a hole transport layer or an electron transport layer. Examples of the above-mentioned organic semiconductor include compounds having a thiophene skeleton such as poly(3-alkylthiophene). In addition, for example, conductive polymers having a polyparaphenylene vinylene skeleton, a polyvinyl carbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, etc. are also mentioned. Further, for example, compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, etc., and carbon-containing materials such as carbon nanotubes, graphene, fullerenes which may be surface-modified are also mentioned.

[0021] Examples of the above-mentioned inorganic semiconductor include titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, CuSCN, Cu 2 O, CuI, MoO 3 、V 2 O 5 、WO 3 、MoS 2 、MoSe 2 、Cu 2 S, etc. can be mentioned.

[0022] When the above photoelectric conversion layer contains the above organic-inorganic perovskite compound and the above organic semiconductor or the above inorganic semiconductor, it may be a laminate in which a thin-film organic semiconductor or inorganic semiconductor part and a thin-film organic-inorganic perovskite compound part are laminated, or it may be a composite film in which an organic semiconductor or inorganic semiconductor part and an organic-inorganic perovskite compound part are compounded. A laminate is preferable in terms of simplicity of the manufacturing method, and a composite film is preferable in terms of the ability to improve the charge separation efficiency in the above organic semiconductor or the above inorganic semiconductor.

[0023] The thickness of the above photoelectric conversion layer preferably has a lower limit of 5 nm and an upper limit of 5000 nm. If the above thickness is 5 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency becomes high. If the above thickness is 5000 nm or less, the generation of regions where charge separation cannot occur can be suppressed, leading to an improvement in photoelectric conversion efficiency. A more preferable lower limit of the above thickness is 10 nm, and a more preferable upper limit is 1000 nm. A still more preferable lower limit is 20 nm, and a still more preferable upper limit is 500 nm.

[0024] When the above photoelectric conversion layer is a composite film in which an organic semiconductor or inorganic semiconductor part and an organic-inorganic perovskite compound part are compounded, the preferable lower limit of the thickness of the above composite film is 30 nm, and the preferable upper limit is 3000 nm. If the above thickness is 30 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency becomes high. If the above thickness is 3000 nm or less, charges easily reach the electrode, resulting in a high photoelectric conversion efficiency. A more preferable lower limit of the above thickness is 40 nm, and a more preferable upper limit is 2000 nm. A still more preferable lower limit is 50 nm, and a still more preferable upper limit is 1000 nm.

[0025] The method for forming the above photoelectric conversion layer is not particularly limited, and examples include a vacuum evaporation method, a sputtering method, a chemical vapor deposition method (CVD), an electrochemical deposition method, a printing method, etc. Among them, by adopting the printing method, a solar cell capable of exhibiting high photoelectric conversion efficiency can be easily formed over a large area. Examples of the printing method include a spin coating method, a casting method, etc., and examples of the method using the printing method include a roll-to-roll method, etc.

[0026] The above power generation unit may have an electron transport layer between the electrode or counter electrode that contacts the cathode and the above photoelectric conversion layer. The material of the above electron transport layer is not particularly limited, and examples include N-type conductive polymers, N-type low molecular weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, surfactants, etc. Specifically, for example, cyano group-containing polyphenylene vinylene, boron-containing polymers, bathocuproine, bathophenanthrene, aluminum hydroxyquinolinate, oxadiazole compounds, benzimidazole compounds, naphthalene tetracarboxylic acid compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluorine group-containing phthalocyanine, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, etc. can be mentioned.

[0027] The above electron transport layer may consist only of a thin film-like electron transport layer, but preferably includes a porous electron transport layer. In particular, when the photoelectric conversion layer is a composite film in which an organic semiconductor or inorganic semiconductor site and an organic-inorganic perovskite compound site are combined, a more complex composite film (a more complex and intertwined structure) can be obtained, and the photoelectric conversion efficiency is increased. Therefore, it is preferable that the composite film is formed on the porous electron transport layer.

[0028] The thickness of the above electron transport layer preferably has a lower limit of 1 nm and an upper limit of 2000 nm. If the above thickness is 1 nm or more, holes can be sufficiently blocked. If the above thickness is 2000 nm or less, it is difficult to cause resistance during electron transport, and the photoelectric conversion efficiency is increased. A more preferable lower limit of the thickness of the above electron transport layer is 3 nm, and a more preferable upper limit is 1000 nm. A further preferable lower limit is 5 nm, and a further preferable upper limit is 500 nm.

[0029] The above power generation unit may have a hole transport layer between the electrode or counter electrode that contacts the anode and the above photoelectric conversion layer. The material of the hole transport layer is not particularly limited, and the hole transport layer may be made of an organic material. Examples of the material of the hole transport layer include, for example, P-type conductive polymers, P-type low molecular weight organic semiconductors, P-type metal oxides, P-type metal sulfides, surfactants, etc. Specifically, for example, compounds having a thiophene skeleton such as poly(3-alkylthiophene) can be mentioned. Further, for example, conductive polymers having a triphenylamine skeleton, a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, etc. can also be mentioned. Furthermore, for example, compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, etc., molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide, etc., fluorine group-containing phosphonic acid, carbonyl group-containing phosphonic acid, copper compounds such as CuSCN, CuI, etc. can be mentioned.

[0030] The flexible solar cell of the present invention has a blocking layer that contacts at least one entire surface of the power generation unit. The present inventors examined the reason for the decrease in power generation performance in a flexible solar cell in which a flame retardant material was added to the encapsulant. As a result, it was found that in a flexible solar cell using an organic-inorganic perovskite compound in the photoelectric conversion layer, the reason was that the flame retardant material came into contact with the power generation unit. The flame retardant material often has a highly reactive molecular structure containing halogen-based atoms, etc., and the power generation unit was deteriorated by the reaction of the flame retardant material with the electrode or the photoelectric conversion layer of the power generation unit. In the present invention, a blocking layer that contacts at least one entire surface of the power generation unit and covers the power generation unit is provided, and further, an encapsulant containing a flame retardant material described later is laminated on the blocking layer, so that while enhancing the flame retardancy, it is possible to suppress the decrease in power generation performance due to the flame retardant material.

[0031] The above-mentioned block layer is not particularly limited as long as it can physically prevent contact between the power generation part and the sealing material containing a flame retardant material described later. The base material for forming the above-mentioned power generation part may be used as the block layer, or another block layer may be prepared. Further, the above-mentioned block layer may be arranged so as to contact the upper surface of the power generation part, may be arranged so as to contact the lower surface, or may be arranged so as to contact both the upper surface and the lower surface. Furthermore, the above-mentioned block layer may cover the side surface in addition to the upper surface or the lower surface of the power generation part. In the present specification, the base material for forming the above-mentioned power generation part is included in the block layer and not included in the power generation part.

[0032] The material constituting the above-mentioned block layer has flexibility, and when it is arranged on the upper surface side of the power generation part, it is not particularly limited as long as it further has transparency. Specifically, for example, those having a resin film made of a heat-resistant polymer such as polyimide or polyester, a metal foil, a thin plate glass, etc. may be mentioned. Among them, from the viewpoints of flexibility and transparency, it is preferable that the above-mentioned block layer contains polyethylene terephthalate, polyethylene, polypropylene, polyethylene naphthalate, polymethyl methacrylate, polystyrene or polycarbonate.

[0033] It is preferable that the above-mentioned block layer has a thickness of 30 μm or more and 200 μm or less. When the thickness of the block layer is within the above range, the sealing material containing a flame retardant material described later is less likely to wrap around the side surface of the block layer and reach the power generation part, and the flexibility can be further enhanced. From the viewpoint of making it difficult for the sealing material containing a flame retardant material to reach the power generation part, the thickness of the above-mentioned block layer is more preferably 50 μm or more, and even more preferably 70 μm or more. From the viewpoint of further enhancing the flexibility, the thickness of the above-mentioned block layer is more preferably 150 μm or less, and even more preferably 100 μm or less.

[0034] The flexible solar cell of the present invention has a sealing material that seals the entire laminate composed of the above-mentioned power generation part and the above-mentioned block layer. By encapsulating and sealing a laminate composed of a power generation part and a block layer with a sealing material, it is possible to suppress the deterioration of the power generation part due to components in the atmosphere. Examples of the sealing material that is the main component of the above sealing material include thermosetting resins, thermoplastic resins, or inorganic materials. Examples of the above thermosetting resin or thermoplastic resin include epoxy resin, acrylic resin, silicone resin, phenol resin, melamine resin, urea resin, etc. Also, butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyvinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene, etc. are mentioned. Among them, polyisobutylene is preferable because of its excellent sealing performance.

[0035] The above sealing material has a flame-retardant part containing a flame-retardant material and a non-flame-retardant part not containing the flame-retardant material. The above flame-retardant part is arranged on the surface side that does not contact the power generation part of the above block layer, the above power generation part contacts the non-flame-retardant part, and does not contact the flame-retardant part. In the case of a flexible solar cell using an organic-inorganic perovskite compound in the photoelectric conversion layer, when a flame-retardant material is added to the sealing material, the power generation performance may decrease due to the contact between the flame-retardant material and the power generation part. In the present invention, the sealing material is divided into two parts, a flame-retardant part containing a flame-retardant material and a non-flame-retardant part not containing a flame-retardant material. By making the power generation part contact only the non-flame-retardant part and laminating the flame-retardant part on the block layer side, the contact between the flame-retardant material and the power generation part can be suppressed, and the decrease in power generation performance can be suppressed. On the other hand, since the flame-retardant part is laminated on the block layer side, the flame retardancy, especially the flame retardancy in the plane direction, can also be enhanced. The above sealing material only needs to contact the power generation part with the non-flame-retardant part, and the flame-retardant part is arranged on the surface side that does not contact the power generation part of the block layer. However, in order to further suppress the decrease in power generation performance, it is preferable that the interface of the above laminate (the laminate of the power generation part and the block layer) only contacts the non-flame-retardant part, that is, the block layer also does not contact the flame-retardant part. In addition, in this specification, the flame retardancy in the planar direction means the property that it is difficult for the flame to spread in the planar direction when the flexible solar cell is brought into contact with a flame and then separated.

[0036] The above flame retardant material has flame retardancy and is not particularly limited as long as it has transparency when the block layer is laminated on the upper surface side of the power generation part. Specific examples of the above flame retardant material include halogen-based flame retardants. Examples of the halogen-based flame retardants include chlorinated paraffin, chlorinated fatty acid esters, and the like. Among them, from the viewpoints of flame retardant performance and transparency, it is preferable that the above flame retardant material contains chlorine atoms.

[0037] When the above flame retardant material is a halogen-based flame retardant, it is preferable that the content ratio (composition ratio) of halogen atoms in the above halogen-based flame retardant is 30% or more and 60% or less. When the content ratio of halogen atoms in the halogen-based flame retardant is within the above range, sufficient flame retardancy can be imparted even when added to the encapsulant. The content ratio of halogen atoms in the above halogen-based flame retardant is more preferably 40% or more, and more preferably 50% or less. The content ratio of the above halogen atoms can be measured by elemental analysis.

[0038] It is preferable that the light transmittance of the above flame retardant part at wavelengths of 500 nm to 1000 nm is 85% or more and 100% or less. When the light transmittance of the flame retardant part is within the above range, the decrease in power generation performance due to the presence of the flame retardant material can be further suppressed. The light transmittance of the above flame retardant material at wavelengths of 500 nm to 1000 nm is more preferably 90% or more, and even more preferably 95% or more.

[0039] It is preferable that the content of the above flame retardant material in the above flame retardant part is 1% by weight or more and 50% by weight or less. When the content of the flame-retardant material is within the above range, the flame retardancy can be further improved and the decrease in transparency can be further suppressed. The content of the flame-retardant material in the above encapsulant is more preferably 5% by weight or more, still more preferably 10% by weight or more, more preferably 30% by weight or less, and still more preferably 20% by weight or less.

[0040] The thickness of the flame-retardant part in the above encapsulant is preferably 20 μm or more and 180 μm or less. By setting the thickness of the flame-retardant part within the above range, the flame retardancy in the planar direction and the protection performance of the power generation part can be further enhanced, and the flexibility can be further enhanced. The thickness of the flame-retardant part in the above encapsulant is more preferably 50 μm or more, still more preferably 70 μm or more, more preferably 150 μm or less, and still more preferably 100 μm or less. When there are a plurality of the flame-retardant parts, the thickness of the flame-retardant part refers to the thickness of each flame-retardant part.

[0041] For the non-flame-retardant part in contact with the power generation part, the ratio of the thickness of the non-flame-retardant part to the thickness of the power generation part (thickness of non-flame-retardant part: thickness of power generation part) is preferably 1:2 or more and 6:1 or less (hereinafter also referred to as the thickness ratio between the power generation part and the non-flame-retardant part). When the thickness of the non-flame-retardant part in contact with the power generation part is in the above ratio to the thickness of the power generation part, it becomes difficult for the flame-retardant material in the flame-retardant part to reach the power generation part, and the decrease in power generation performance can be further suppressed. The thickness ratio between the power generation part and the non-flame-retardant part is more preferably 1:1 or more and more preferably 4:1 or less.

[0042] In the flexible solar cell of the present invention, the average distance from the above power generation part to the interface between the above flame-retardant part and the above non-flame-retardant part is preferably 10 μm or more and 100 μm or less (hereinafter also referred to as the interface distance). When the average distance from the power generation part to the interface between the flame-retardant part and the non-flame-retardant part is within the above range, it becomes difficult for the flame-retardant material in the flame-retardant part to reach the power generation part, and the decrease in power generation performance can be further suppressed. It is more preferable that the above interface distance is 30 μm or more, still more preferable that it is 50 μm or more, more preferable that it is 80 μm or less, and still more preferable that it is 60 μm or less. Note that the above interface distance refers to the average distance from the electrode on the side closer to the interface of the power generation part to the interface. Further, the above interface distance is the interface distance when the power generation part and the flame-retardant part are not in contact, and when the power generation part and the flame-retardant part are in contact (when the interface exists on the side surface of the power generation part), the interface distance does not exist.

[0043] From the viewpoint of the balance between the protection performance and flexibility of the power generation part, the thickness of the entire above-mentioned encapsulant is preferably 100 μm or more, more preferably 200 μm or more, preferably 1000 μm or less, and more preferably 700 μm or less. Note that the thickness of the above-mentioned encapsulant in the region where the power generation part and the block layer are arranged refers to the thickness obtained by adding the thicknesses of the power generation part and the block layer.

[0044] The flexible solar cell of the present invention may have a front sheet at the uppermost part. By forming patterns such as irregularities and arcs on the surface of the front sheet, the front sheet has the role of suppressing light reflection and enhancing the drainage performance of the surface of the flexible solar cell. For example, when a front sheet having a convex arc with a vertex at the center of the flexible solar cell is provided, a drainage gradient from the center to the end of the solar cell can be provided, and when a front sheet having a concave arc with the lowest part at the center of the flexible solar cell is provided, a water collecting part from the end to the center of the solar cell can be provided. By providing such a drainage gradient and water collecting part, the deposition of dirt and the like can be concentrated at specific locations. Also, the design can be improved by randomly forming irregularities on the front sheet.

[0045] The material of the front sheet is not particularly limited as long as it has transparency. Examples thereof include fluorine-containing resins, vinyl chloride-based resins, polyethylene-based resins, polycarbonate-based resins, and the like. Specifically, polycarbonate, polyvinyl chloride, tetrafluoroethylene resin, polyvinylidene fluoride, polychlorotrifluoroethylene, and the like can be mentioned. Among them, fluorine-containing resins are preferred because of their excellent weather resistance.

[0046] The thickness of the front sheet is not particularly limited, but from the viewpoint of the balance between light transmittance and the functionality of the front sheet, it is preferably 25 μm or more, more preferably 50 μm or more, preferably 1000 μm or less, and more preferably 300 μm or less.

[0047] The flexible solar cell of the present invention may have a back sheet at the lowermost part. The back sheet has a role of preventing the intrusion of substances that cannot be completely prevented from intruding only by a sealing layer such as moisture, and enhancing the weather resistance of the flexible solar cell. Examples of the material of the back sheet include polyethylene terephthalate and the like.

[0048] The thickness of the back sheet is not particularly limited, but from the viewpoint of the balance between flexibility and the functionality of the back sheet, it is preferably 50 μm or more, more preferably 100 μm or more, preferably 1000 μm or less, and more preferably 500 μm or less.

[0049] Here, schematic diagrams showing an example of the structure of the flexible solar cell of the present invention are shown in FIGS. 1 to 4. As shown in FIG. 1, the flexible solar cell of the present invention includes a power generation unit 1 having an electrode 13, a photoelectric conversion layer 12, and a counter electrode 11, and the entire laminate including a block layer 2 that contacts at least one entire surface of the power generation unit 1 is sealed by a sealing material 3, and a front sheet 4 and a back sheet 5 are disposed above and below the sealing material. The sealing material 3 is composed of a flame-retardant portion 31 containing a flame-retardant material and a non-flame-retardant portion 32 not containing a flame-retardant material. The power generation unit 1 contacts only the non-flame-retardant portion 32 and does not contact the flame-retardant portion 31. Further, the flame-retardant portion 31 is laminated on the block layer 2 side of the laminate, and the block layer 2 is arranged such that the flame-retardant portion 31 does not directly contact the power generation unit 1. By arranging the sealing material 3 in such a manner, it becomes difficult for the flame-retardant material to contact the power generation unit 1, so that it is possible to enhance the flame retardancy in the planar direction while suppressing the deterioration of the power generation unit 1.

[0050] In the flexible solar cell shown in FIG. 2, the block layer 2 is disposed on the surface of the power generation unit 1 on the electrode 13 side. Further, since the block layer 2 is disposed below the power generation unit 1, the flame-retardant portion 31 is also disposed below. In the flexible solar cell shown in FIG. 3, the block layer 2 is disposed on both surfaces of the power generation unit 1. By adopting such an arrangement, the deterioration of the power generation unit 1 can be further suppressed. The flexible solar cell of FIG. 4 has a structure in which the block layer 2 covers the surface of the power generation unit 1 on the electrode 13 side and the side surface of the power generation unit 1. By covering the side surface of the power generation unit 1 with the block layer 2, it becomes more difficult for the flame-retardant portion 31 that has crept around to the side surface of the block layer 2 to reach the power generation unit 1, and the deterioration of the power generation unit 1 can be suppressed.

[0051] The manufacturing method of the flexible solar cell of the present invention is not particularly limited, but since it is easy to manufacture on a large area, as shown in FIG. 5, a method of laminating by sandwiching a laminate of the power generation unit 1 and the block layer 2 between a flame-retardant portion 31 and a sheet having a front sheet 4 as necessary (sheet A), and a non-flame-retardant portion 32 and a sheet having a back sheet 5 as necessary (sheet B) is preferable.

[0052] When the flexible solar cell has the structure as shown in FIG. 1, Sheet A can be obtained by performing a step of laminating a sealing material (flame-retardant portion) on the front sheet. In addition, when the flexible solar cell has an adhesive layer that adheres the sealing material and the front sheet, the adhesive layer is laminated on the front sheet before laminating the flame-retardant portion. When the block layer also has a structure that does not contact the flame-retardant portion, a non-flame-retardant portion is laminated after laminating the flame-retardant portion.

[0053] The above laminate can be obtained by sequentially laminating each layer such as an electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and a counter electrode on the block layer. It can also be obtained by laminating each layer on the electrode instead of the base material. In that case, a step of adhering the obtained power generation part to the block layer is performed. As for the lamination method of each layer, a conventional method can be used without particular limitation.

[0054] When the flexible solar cell has the structure as shown in FIG. 1, Sheet B can be obtained by laminating a non-flame-retardant portion on the back sheet. In addition, when there is no back sheet, it can be obtained by forming a layer composed only of a sealing material (non-flame-retardant portion) by coating or the like. Furthermore, when the flexible solar cell has the structure as shown in FIG. 3, it can be obtained by laminating a flame-retardant portion on the back sheet and laminating a non-flame-retardant portion on the flame-retardant portion.

[0055] Examples of the method of laminating the above Sheet A, the above power generation part, and the above Sheet B include, for example, the roll-to-roll method. By using the roll-to-roll method, a large-area flexible solar cell can be continuously manufactured.

Advantages of the Invention

[0056] According to the present invention, it is possible to provide a flexible solar cell that is excellent in flame retardancy in the planar direction while suppressing a decrease in power generation performance.

Brief Description of the Drawings

[0057]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0058] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples only.

[0059] (Example 1) <Manufacturing of Flexible Solar Cell> A polyethylene terephthalate (PET) film with a thickness of 100 μm was prepared as the block layer. An ITO film with a thickness of 200 nm was formed as the counter electrode on the block layer by sputtering. A thin-film electron transport layer with a thickness of 20 nm was formed on the formed counter electrode by sputtering. Further, a titanium oxide paste containing titanium oxide was applied on the thin-film electron transport layer by spin coating, and then dried to form a porous electron transport layer with a thickness of 100 nm. Next, lead iodide as a metal halide compound was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) to prepare a 1M solution, and a film was formed on the porous electron transport layer by spin coating. Further, methylammonium iodide as an amine compound was dissolved in 2-propanol to prepare an 8 wt% solution. This solution was applied on the above lead iodide by spin coating, and annealed at 150 °C for 10 minutes to obtain CH 3 NH 3 PbI 3A photoelectric conversion layer containing [substance] was formed. Subsequently, a chlorobenzene solution containing 2% by weight of Spiro-OMETAD (manufactured by Merck) was applied onto the photoelectric conversion layer by spin coating and then dried to form a hole transport layer with a thickness of 80 nm. Thereafter, an Al film with a thickness of 100 nm was formed as an electrode on the photoelectric conversion layer by sputtering, and a laminate in which a power generation unit composed of a counter electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an electrode was formed on the blocking layer was obtained.

[0060] Subsequently, PET with a thickness of 50 μm was prepared as a front sheet. Next, a sealing material for a flame-retardant site was prepared by adding 10% by weight of Empala 40 (chlorinated paraffin, chlorine content 40 - 42%, manufactured by Ajinomoto Fine-Techno Co., Inc.), which is a flame-retardant material, to polyisobutylene, the main component, and sheet A was obtained by applying it onto the front sheet to a thickness of 100 μm. On the other hand, a back sheet with a thickness of 360 μm and containing aluminum (manufactured by Toyo Aluminum Co., Ltd., FAPL) was prepared as a back sheet, and sheet B was obtained by applying a sealing material for a non-flame-retardant site composed only of polyisobutylene to a thickness of 70 μm. Thereafter, the laminate was laminated with sheet A and sheet B such that the sealing material (flame-retardant site) of sheet A faced the blocking layer and the sealing material (non-flame-retardant site) of sheet B faced the power generation unit, thereby obtaining a flexible solar cell with a flame-retardant site laminated only on the blocking layer side. The cross-section of the obtained flexible solar cell was observed using an electron microscope, and the distance (interface distance) between the interface of the power generation unit and the blocking layer and the interface of the flame-retardant site and the non-flame-retardant site was measured.

[0061] (Examples 2 - 5) A flexible solar cell was obtained in the same manner as in Example 1 except that the following flame-retardant materials were used. Empala K-50: Chlorinated paraffin, chlorine content 50 - 52%, manufactured by Ajinomoto Fine-Techno Co., Inc. Empala A-1: Chlorinated fatty acid ester, chlorine content 35 - 36.5%, manufactured by Ajinomoto Fine-Techno Co., Inc. Empala A-3: Chlorinated fatty acid ester, chlorine content 31 - 33%, manufactured by Ajinomoto Fine-Techno Co., Inc. Empala M-3: Chlorinated fatty acid ester, chlorine content 32 - 34%, manufactured by Ajinomoto Fine-Techno Co., Inc.

[0062] (Comparative Examples 1 - 5) The flame-retardant materials used were as shown in Table 1, and a flexible solar cell in which the laminate was sealed only at the flame-retardant site was produced in the same manner as in Example 1, except that the sealing material applied to the backsheet was the same as the sealing material for the flame-retardant site.

[0063] (Comparative Example 6) A flexible solar cell in which the laminate was sealed only at the non-flame-retardant site was obtained in the same manner as in Example 1, except that the sealing material applied to the front sheet was a sealing material for the non-flame-retardant site (polyisobutylene).

[0064] <Evaluation> The following evaluations were performed on the flexible solar cells obtained in the examples and comparative examples. The results are shown in Table 1.

[0065] (1) Evaluation of flame retardancy Evaluation samples were obtained by preparing the same sealing materials for the flame-retardant sites as in each example and comparative example and applying the sealing materials for the flame-retardant sites to an aluminum thin plate with a thickness of 0.3 mm so that the thickness was 100 μm. The obtained evaluation samples were fixed vertically, and after applying a flame from the lower end for 10 seconds and then separating it, the combustion of the sealing material for the flame-retardant site was confirmed. The flame retardancy was evaluated as "〇" when the flame was extinguished or the spread distance was 15 cm or less, and "×" when the spread distance exceeded 15 cm.

[0066] (2) Evaluation of initial conversion efficiency Immediately after the production of the flexible solar cell, a power supply (Model 236, manufactured by KEITHLEY) was connected between the electrodes of the flexible solar cell, and the photoelectric conversion efficiency was measured using a solar simulation (manufactured by Yamashita Electric Co., Ltd.) with an intensity of 100 mW / cm 2 The initial conversion efficiency was evaluated as "〇" when the photoelectric conversion efficiency was 0.80 or more based on the photoelectric conversion efficiency of Comparative Example 6 as the reference (1), and "×" when it was less than 0.80.

[0067] (3) Evaluation of durability The obtained flexible solar cell was subjected to a damp heat test at a temperature of 85°C and a humidity of 85% for 500 hours to conduct a durability test. For the flexible solar cell after the durability test, the photoelectric conversion efficiency was measured in the same manner as the evaluation of the initial conversion efficiency, and the retention rate from the initial conversion efficiency was calculated. When the retention rate was 85% or more, it was evaluated as "○", and when it was less than 85%, it was evaluated as "×" for durability.

[0068]

Table 1

Industrial applicability

[0069] According to the present invention, it is possible to provide a flexible solar cell that is excellent in flame retardancy in the planar direction while suppressing a decrease in power generation performance.

Explanation of symbols

[0070] 1 Power generation unit 11 Counter electrode 12 Photoelectric conversion layer 13 Electrode 2 Block layer 3 Sealing material 31 Flame-retardant part 32 Non-flame-retardant part 4 Front sheet 5 Back sheet

Claims

1. A flexible solar cell comprising: a power generation section; a blocking layer in contact with at least one entire surface of the power generation section; and a sealing material that seals an entire laminate including the power generation section and the blocking layer, the power generating unit has an electrode, a photoelectric conversion layer, and a counter electrode, the photoelectric conversion layer contains an organic-inorganic perovskite compound, the sealing material has a flame-retardant portion containing a flame-retardant material and a non-flame-retardant portion not containing the flame-retardant material, The flame retardant material contains a halogen-based flame retardant, the flame-retardant portion is disposed on a surface of the block layer that is not in contact with the power generation section, the power generation unit is in contact with the non-flame retardant portion and is not in contact with the flame retardant portion, The blocking layer is in contact with the flame-retardant portion, The blocking layer is in contact with the light incident surface of the power generating unit. A flexible solar cell.

2. The flexible solar cell according to claim 1 , wherein the flame-retardant material contains chlorine atoms.

3. 3. The flexible solar cell according to claim 1, wherein the material constituting the blocking layer contains polyethylene terephthalate, polyethylene, polypropylene, polyethylene naphthalate, polymethyl methacrylate, polystyrene or polycarbonate.

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