Solar cell

Abstract

A solar cell (100) according to an embodiment of the present invention has a glass layer (102) and a resin layer (101). The thickness of the glass layer (102) is 250 µm or less. The resin layer (101) forms the outermost layer on the light-entering surface side, is disposed on the upper side of the glass layer (102), and has an oxygen index of 22% or more. A substance that has a zeta potential having a symbol different from those of the zeta potentials of the glass layer (102) and the resin layer (101) is disposed between the glass layer (102) and the resin layer (102).

Description

solar cells

[0001] Embodiments of the present invention relate to solar cells.

[0002] In recent years, expectations for solar cells, which enable solar power generation, have been rising in order to protect the environment and prevent global warming.

[0003] Conventional solar cells used relatively thick materials such as glass plates a few millimeters thick as substrates or protective films. As a result, the solar cells themselves were heavy, and the load-bearing capacity limitations restricted the locations and equipment in which they could be installed.

[0004] Therefore, in recent years, thin-film solar cells, which are relatively lightweight, have attracted attention. Research is being conducted on thin-film solar cells, including silicon solar cells using Si thin films, CIGS solar cells using copper-indium-gallium-selenium (CIGS) thin films, CIS solar cells using copper-indium-sulfur (CIS) thin films, and perovskite solar cells using lead or tin-halogen-monovalent cation thin films. All of these thin-film solar cells are attracting attention as solar cells that can be expected to have high conversion efficiency.

[0005] Furthermore, because the thin-film solar cells described above can be formed on resin films or metal thin films, they are also called flexible thin-film solar cells. Flexible thin-film solar cells are lightweight and highly flexible, so they have fewer restrictions on installation locations than conventional solar cells, and can be freely installed, for example, on the roofs of large facilities or on curved surfaces.

[0006] Incidentally, when installing thin-film solar cells outdoors, such as on roofs, the fire resistance of the thin-film solar cells is important. Therefore, to improve fire resistance, it is being considered to laminate a thin-film glass layer with a thickness of several hundred microns or less on the light-receiving surface side of the thin-film solar cell. On the other hand, since the thin-film glass itself is easily damaged, it is being considered to laminate a resin layer on top of the thin-film glass as a protective layer to prevent damage.

[0007] However, depending on the material of the resin layer, it could reduce the fire resistance of the thin-film solar cell. Also, if the resin layer peeled off from the thin-film glass, the thin-film glass would be exposed, and its function as a protective layer for the thin-film glass could be impaired.

[0008] Japanese Patent Application Publication No. 2009-94019

[0009] The problem that this invention aims to solve is to provide a solar cell that has excellent fire resistance as well as excellent resistance to peeling of the resin layer.

[0010] The solar cell of this embodiment has a glass layer and a resin layer. The thickness of the glass layer is 250 μm or less. The resin layer is laminated on the glass layer and has an oxygen index of 22% or more. A material having a zeta potential with a sign different from that of the glass layer and the resin layer is placed between the glass layer and the resin layer.

[0011] A schematic cross-sectional view showing a solar cell of the first embodiment. A schematic cross-sectional view showing a photoelectric conversion layer provided in the solar cell of the first embodiment. A schematic cross-sectional view showing a solar cell of Example 1. A schematic cross-sectional view showing a solar cell of Example 4.

[0012] The solar cell of the embodiment will be described below with reference to the drawings.

[0013] As shown in Figure 1, the solar cell 100 of this embodiment has a light incident surface 100A. Light such as sunlight is incident on the solar cell 100 from the light incident surface 100A side. The solar cell 100 of this embodiment is constructed by stacking a resin layer 101, a glass layer 102, and a photoelectric conversion layer 103 in order from the light incident surface 100A side. Between the glass layer 102 and the resin layer 101, a material having a zeta potential with a sign different from the zeta potentials of the glass layer 102 and the resin layer 101 is placed. Preferably, the zeta potentials of the glass layer 102 and the resin layer 101 have a negative sign, and the zeta potential of the material has a positive sign. Note that the material is not shown in Figure 1.

[0014] The resin layer 101 may constitute the outermost layer on the light incident surface 100A side of the solar cell 100. The resin layer 101 is laminated on top of the glass layer 102 and has an oxygen index of 22% or higher. The resin layer 101 is provided to prevent damage to the glass layer 102 and to improve the fire resistance of the solar cell 100.

[0015] The oxygen index is the oxygen index specified in JIS K 7201-1:2007. The higher the oxygen index of the resin layer 101, the less likely it is to burn continuously in the atmosphere, thereby improving the fire resistance of the solar cell 100. Since the oxygen concentration in the atmosphere is 21%, a resin layer 101 with an oxygen index of 22% or higher will be less likely to burn continuously in the atmosphere. When evaluating the oxygen index of the resin layer 101 according to JIS K 7201-1:2007, the shape of the test specimen shall be V(2), the ignition method of the test specimen shall be procedure B, and the initial oxygen concentration at the start of the test shall be 21%.

[0016] The resin layer 101 is preferably composed of a resin having flame retardant or slow-burning properties. Specifically, it may contain at least one or more resins selected from silicone resin, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), fluororesin, polyimide, or polycarbonate (PC).

[0017] Furthermore, the resin layer 101 may be a single layer made of one of the following: silicone resin, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), fluororesin, polyimide, or polycarbonate (PC), or it may be a laminate containing one or more of these resins.

[0018] Of the resins listed above, silicone resin is particularly preferred due to its excellent environmental resistance and flexibility. Silicone resin includes silicone rubber. Polycarbonate resin, on the other hand, offers superior fire resistance.

[0019] When using silicone rubber for the resin layer 101, it is preferable to use silicone rubber with a hardness in the range of 10° to 70°. If the hardness is less than 10°, it is too soft and prone to deformation, and if the hardness exceeds 70°, the flexibility decreases. The hardness of the silicone rubber shall be the durometer hardness measured in accordance with JIS K 6253-3:2012.

[0020] When the resin layer 101 is constructed as a laminate, it is preferable to make the uppermost layer of the resin layer 101 on the light incident surface 100A side a fluororesin in order to improve the weather resistance of the solar cell 100. As the fluororesin, either polyvinylidene fluoride (PVDF) or ethylene-tetrafluoroethylene copolymer (ETFE) can be used.

[0021] Furthermore, when the resin layer 101 is constructed as a laminate, a viscous substance (for example, silicone gel) may be interposed between the resins. This improves the adhesion between the resins. The silicone gel may also contain a UV shielding material, thereby making the silicone gel a UV shielding layer as well.

[0022] The thickness of the resin layer 101 is preferably in the range of 50 to 1000 μm. If the thickness of the resin layer 101 is 50 μm or more, damage to the glass layer 102 can be prevented. Also, if the thickness of the resin layer 101 is 1000 μm or less, the flexibility of the solar cell 100 can be ensured.

[0023] The glass layer 102 is provided to protect the photoelectric conversion layer 103 while ensuring the flexibility of the solar cell 100. The glass layer 102 also serves as the substrate for the second electrode 204 that constitutes the photoelectric conversion layer 103. Therefore, the glass layer 102 requires a certain thickness to ensure strength. Specifically, the thickness of the glass layer 102 is 250 μm or less. If the glass layer thickness exceeds 250 μm, the flexibility of the solar cell 100 decreases, and the weight of the solar cell 100 itself increases. The thickness of the glass layer 102 is preferably in the range of 50 μm to 200 μm. A thickness of 50 μm or more makes the glass layer 102 less prone to cracking and easier to handle. Furthermore, if the thickness of the glass layer 102 is 200 μm or less, the flexibility of the solar cell 100 is further improved. As for the material of the glass layer 102, alkali-free glass is preferred because it is less susceptible to ion contamination.

[0024] Next, the substance placed between the glass layer 102 and the resin layer 101 will be described. This substance is used to modify the surface of the glass layer 102. In the following description, this substance may be referred to as the surface modifying substance. The surface modifying substance has a zeta potential with a different sign than the zeta potentials of the glass layer 102 and the resin layer 101.

[0025] Generally, glass surfaces are hydrophilic, and the glass layer 102 in this embodiment has a negative zeta potential. This is because the glass surface contains silicon oxide, which has a negative zeta potential. On the other hand, many resin surfaces are hydrophobic, and the resin layer 101 in this embodiment has a negative zeta potential. For example, the silicone resin and fluororesin that make up the resin layer 101 are typical hydrophobic resins. Therefore, when the resin layer 101 is laminated onto the glass layer 102, electrostatic repulsion occurs at the interface between the glass layer 102 and the resin layer 101, making delamination more likely.

[0026] Furthermore, the zeta potential of the glass layer 102 has a negative sign, while the zeta potential of the resin layer 101 also has a negative sign, similar to the glass layer 102. Thus, because the glass layer 102 and the resin layer 101 have zeta potentials of the same sign, they are more prone to delamination.

[0027] Therefore, in this embodiment, a surface-modifying material having a zeta potential with a different sign from the zeta potentials of the glass layer 102 and the resin layer 101 is placed between the glass layer 102 and the resin layer 101.

[0028] Specifically, a surface-modifying material having a positive zeta potential is placed between the glass layer 102 and the resin layer 101.

[0029] Since the zeta potential of the glass layer 102 is negative, it has a high bonding force with surface-modifying materials that have a positive zeta potential. Similarly, since the zeta potential of the resin layer 101 is negative, it has a high bonding force with surface-modifying materials that have a positive zeta potential. As a result, the glass layer 102 and the resin layer 101 become strongly bonded via the surface-modifying materials. In this way, the glass layer 102 and the resin layer 101 are bonded by electrostatic force, and the bonding force is maintained even in high-temperature environments.

[0030] In this way, the surface of the glass layer 102 is modified by the surface modifying material, the bonding strength between the glass layer 102 and the resin layer 101 is increased, and delamination between the glass layer 102 and the resin layer 101 is prevented.

[0031] In this embodiment, zeta potential refers to the zeta potential in water with a pH of 7. The specification "water with a pH of 7" is based on the assumption of use in normal atmospheric conditions, such as when the device is wet with condensation or rainwater.

[0032] Forming the surface modifying material in layers is more preferable in terms of preventing delamination between the glass layer 102 and the resin layer 101. In this case, for example, it is preferable to have a thickness of at least a monolayer. There is no particular upper limit, but for example, it should be 10 nm or less. Furthermore, the surface modifying material does not necessarily have to be formed in layers; it may be present between the glass layer 102 and the resin layer 101 in an amount sufficient to prevent delamination between the two.

[0033] Examples of the surface modifying substance include, for example, aluminum oxide, titanium oxide, zirconium oxide, silicon nitride, graphene compound, or 3-aminopropyltriethoxysilane. In this embodiment, any one of these may be used. All of these substances exhibit a positive zeta potential in water at pH 7.

[0034] As a method for modifying the surface of the glass layer 102, the surface of the glass layer 102 may be modified with a surface modifier that is a nitrogen compound having a positive zeta potential at one end and a functional group that easily binds to silicon oxide at the other end.

[0035] The graphene compound has a basic skeleton in which carbon atoms are planar-bonded, and is preferably a chemically modified basic skeleton. One preferred graphene compound is a graphene compound having a polyalkyleneimine, particularly a polyethyleneimine chain, as shown in the following formula.

[0036]

[0037] The graphene compound having the above-described graphene compound structure is excellent in water dispersibility. Therefore, when forming a film of the graphene compound on the surface of the glass layer 102 by coating, the coating becomes easy, and the zeta potential of the surface of the glass layer 102 can be made a positive value.

[0038] In the graphene compound structure of the above-described graphene compound, a polyethyleneimine chain is exemplified as the polyalkyleneimine chain. The number of repeating units n of the polyethyleneimine chain is not particularly limited, but n = 2 to 8 is preferable, and polyethyleneimine with n = 2 is particularly preferable. Also, not only linear polyalkyleneimine but also polyalkyleneimine having a branched chain or a cyclic structure can be used.

[0039] Also, a part of the carbon constituting the basic skeleton of the graphene compound may be substituted with nitrogen. By substituting a part of the carbon atoms constituting the basic skeleton of the graphene compound with nitrogen atoms, the ion adsorption property can be enhanced.

[0040] The zeta potential in this embodiment is measured by the electrophoresis light scattering method (ELS) using a "Zetasizer Nano ZS" (manufactured by Malvern). Specifically, it is measured using a flat plate zeta potential measurement cell with polystyrene latex as tracer particles.

[0041] When measuring the zeta potential of the resin layer 101, the glass layer 102, and the surface modifying substance, the pH can be adjusted by adding dilute hydrochloric acid and dilute potassium hydroxide aqueous solution to pure water.

[0042] Similarly, when the surface modifying substance is in powder form, the zeta potential of the measurement object can be measured by the electrophoresis light scattering method (ELS) using a "Zetasizer Nano ZS" (manufactured by Malvern). The cell used at this time is a capillary cell.

[0043] When the material to be measured is in powder form, the pH when measuring the zeta potential can be adjusted, for example, by adding dilute hydrochloric acid and dilute potassium hydroxide aqueous solution to pure water in which a photocatalyst material (or cocatalyst material) is dispersed.

[0044] As shown in FIG. 2, the photoelectric conversion layer 103 is composed of a substrate 201, a first electrode 202, a light absorption layer 203, and a second electrode 204 laminated in order from the side opposite to the light incident surface 100A. Note that an intermediate layer (for example, a hole transport layer and an electron injection layer, etc.) not shown in the figure may be included between the first electrode 202 and the light absorption layer 203, and between the light absorption layer 203 and the second electrode 204. Also, a protective layer or another substrate not shown in the figure may be provided between the first electrode 202 and the substrate 201, and between the second electrode 204 and the glass layer 102.

[0045] Hereinafter, the substrate 201, the first electrode 202, the light absorption layer 203, and the second electrode 204 constituting the photoelectric conversion layer 103 will be described.

[0046] The substrate 201 is not particularly limited, but in order to ensure the flexibility of the solar cell 100, it is preferably made of a resin sheet made of a resin such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polycarbonate (PC), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyimide, or acrylic, or of aluminum foil or stainless steel foil. The thickness of the substrate 201 is, for example, 50 μm to 200 μm.

[0047] The first electrode 202 may be a metal film or a transparent conductive film. The metal film is not particularly limited, but may be, for example, a film of Al, Ag, stainless steel, Mo, Ti, Au, or W. Furthermore, by making the thickness of the metal film 4 nm to 20 nm, the metal film can be used as a transparent electrode film.

[0048] Transparent conductive films include, for example, indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), titanium-doped indium oxide (ITiO), and indium gallium zinc oxide (IndiumGalliumZincO). Oxide (IGZO), hydrogen-doped indium oxide (In2O3), etc., can be used. The transparent conductive film may be a multilayer film. When the transparent conductive film is a multilayer film, in addition to the above oxides, a film such as tin oxide may be included in the multilayer film.

[0049] Furthermore, a first electrode 202 can also be made by laminating a transparent conductive film and a metal film.

[0050] Further, the first electrode 202 is not limited to the above, and may be formed of, for example, a carbon-containing film (such as carbon nanotubes, graphene, graphite, etc.). These carbon-containing films have high stability and high resistance to humidity and halogens. However, since the resistance is higher than that of a metal film, it is preferable to add a metal auxiliary electrode.

[0051] The first electrode 202 is formed by a vacuum evaporation method, a sputtering method, an ion plating method, a plating method, a coating method, or the like. The thickness of the first electrode 202 may be appropriately determined according to the material used, but is preferably, for example, 50 nm to 250 nm. When the first electrode 202 is a carbon-containing film, it is preferably 10 μm to 50 μm.

[0052] The light absorption layer 203 is not particularly limited as long as it is electrified by the incident light, but is preferably composed of a material having a perovskite structure (perovskite compound). Preferably, it may be composed of a perovskite compound having a halogen element.

[0053] The perovskite structure consists of, for example, ions A, ions B, and ions X, and can be represented as ABX ３ There may be a perovskite structure when ions B are smaller than ions A. The perovskite structure has, for example, a cubic unit cell. Ions A are arranged at each vertex of the cube, and ions B are arranged at the body center. Ions X are arranged at each face center of the cube around the body-center ion B.

[0054] AX ６ The orientation of the octahedron is likely to be distorted by the interaction with ions A. Due to the decrease in symmetry, a Mott transition occurs, and the valence electrons localized on ions A can spread as a band. Ions A are preferably CH ３ NH ３ ＋ Ions B are preferably either Pb ２＋ or Sn ２＋ Ions X are preferably Cl － Br － and I －It is preferable that at least one of the following be present. Each of the materials constituting ion A, ion B, and ion X may be a single material or a mixture of materials.

[0055] The thickness of the light-absorbing layer 203 is, for example, 200 nm to 800 nm.

[0056] When forming the light-absorbing layer 203, it is preferable to employ a coating method in which the material is dissolved in a solvent and applied onto the electrode (or intermediate layer). This coating method allows for the easy formation of a large-area light-absorbing layer 203. Examples of solvents that can be used include unsaturated hydrocarbon solvents, halogenated aromatic hydrocarbon solvents, halogenated saturated hydrocarbon solvents, and ethers. Examples of unsaturated hydrocarbon solvents include toluene, xylene, tetralin, decalin, mesitylene, n-butylbenzene, sec-butylbenzene, and tert-butylbenzene. Examples of halogenated aromatic hydrocarbon solvents include chlorobenzene, dichlorobenzene, and trichlorobenzene. Examples of halogenated saturated hydrocarbon solvents include carbon tetrachloride, chloroform, dichloromethane, dichloroethane, chlorobutane, bromobutane, chloropentane, chlorohexane, bromohexane, and chlorocyclohexane. Examples of ethers include tetrahydrofuran and tetrahydropyran. It is more preferable to use halogenated aromatic solvents. Furthermore, DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), 2-propanol, and γ-butyrolactone can also be used. These solvents can be used individually or in combination. The solvent is not particularly restricted as long as it can dissolve the material without damaging it.

[0057] Methods for applying solutions include slit die coating, spin coating, dip coating, casting, bar coating, roll coating, wire bar coating, spray coating, screen printing, gravure printing, flexographic printing, offset printing, gravure-offset printing, dispenser coating, nozzle coating, capillary coating, inkjet coating, and meniscus coating. These coating methods can be used individually or in combination.

[0058] The second electrode 204 in this embodiment can be made of the same material as the first electrode 202. In particular, it is preferable that the second electrode 204 contains a transparent conductive material. The second electrode 204 can be formed by vacuum deposition, sputtering, ion plating, plating, coating, etc., similar to the first electrode 202. The second electrode 204 can be formed by these methods on the side of the glass layer 102 opposite to the light incident surface 100A.

[0059] The thickness of the second electrode 204 is, for example, 200 nm to 800 nm.

[0060] According to at least one embodiment described above, the solar cell 100 of this embodiment comprises a glass layer 102 with a thickness of 250 μm or less, a resin layer 101 with an oxygen index of 22% or more, and a surface modifying material disposed between the glass layer 102 and the resin layer 101 and having a zeta potential with a sign different from that of the glass layer 102 and the resin layer 101, thus making it possible to make a solar cell with excellent fire resistance. Furthermore, the presence of the surface modifying material increases the bonding force between the glass layer 102 and the resin layer 101, making them less prone to peeling, thus maintaining the protective function of the resin layer 101 on the glass layer 102, and at the same time maintaining fire resistance. In addition, since the solar cell 100 itself has excellent flexibility, it can be used as a flexible thin-film solar cell.

[0061] The embodiment will be described in more detail below with reference to examples, but the conditions in the examples are merely examples adopted to confirm the feasibility and effectiveness of this embodiment, and this embodiment is not limited to these example conditions. This embodiment can adopt various conditions without departing from the spirit of this embodiment and insofar as it achieves the objective of this embodiment.

[0062] (Example 1) A solar cell 300 as shown in Figure 3 is prepared. The preparation procedure is described below. First, a transparent electrode 302 (second electrode) made of indium tin oxide (ITO) with a thickness of 200 nm is prepared by sputtering on the side opposite to the light incident surface 300A of a 100 μm thick polycarbonate film (substrate 301) with a hard coat layer. Furthermore, a toluene solution of C60-PCBM is applied to the transparent electrode 302 with a bar coater and dried to laminate an electron injection layer 303 with a thickness of 30 nm.

[0063] Next, a solution of lead iodide and methylammonium iodide dissolved in a solvent is applied to the electron injection layer 303, and then dried to laminate a 600 nm thick light absorption layer 304. Then, a solution of 2,2',7,7'-Tetrakis[N,N-di(4-methylphenyl)amino]-9,9'-spirobifluorene (hereinafter referred to as Spiro-OMeTAD) is applied to the light absorption layer 304, and then dried to laminate a hole transport layer 305.

[0064] Next, a counter electrode (first electrode) 306 made of molybdenum (Mo) with a thickness of 50 nm is laminated onto the hole transport layer 305 by sputtering.

[0065] Next, a silicone gel 307 is applied to the surface of the substrate 301 on the light incident surface 300A side to a thickness of 10 μm, and then a glass layer 308 made of alkali-free glass with a thickness of 100 μm is attached.

[0066] Next, a graphene compound 309 (surface modifier) ​​having the above-described graphene compound structure is applied to a thickness of approximately 2 nm. A 300 μm thick, 60° hardness silicone rubber sheet 310 (resin layer) is then bonded to it. Furthermore, a 10 μm thick silicone gel 311 containing a UV absorber is applied to the silicone rubber sheet 310. The silicone gel 311 also acts as a UV blocking layer. A 50 μm thick PVDF film 312 (resin layer) is then bonded to it.

[0067] A silicone gel sealant 313 is applied to the surface of the first electrode (counter electrode made of Mo) 306 opposite to the light incident surface 300A to a thickness of 300 μm, and then a 100 μm thick aluminum foil 314 is attached. In this way, a solar cell 300 is created. The periphery of the solar cell 300 is sealed with a silicone gel sealant 313 and aluminum foil 314 (not shown).

[0068] The resulting solar cell 300 exhibits an energy conversion efficiency of approximately 12% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the decrease in energy conversion efficiency is only 5%. In addition, the resulting solar cell 300 exhibits flame retardancy of V-0 and 5VB or higher according to the UL94 combustion standard.

[0069] (Example 2) A solar cell was fabricated in the same manner as in Example 1, except that instead of coating a graphene compound, an alumina nanofiber sol (manufactured by Kawaken Fine Chemicals Co., Ltd.) was applied to form a 100 nm thick aluminum oxide layer (surface modifier).

[0070] The resulting solar cells exhibit an energy conversion efficiency of approximately 13% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the energy conversion efficiency of the resulting solar cells decreases by only 5%. In addition, the resulting solar cells exhibit flame retardancy of V-0 and 5VB standards or higher according to the UL94 combustion standard.

[0071] (Example 3) A solar cell is prepared in the same manner as in Example 1, except that instead of coating a graphene compound, an ethanol solution of 3-aminopropyltriethoxysilane is coated and heated at 60°C to form a monolayer of 3-aminopropyl groups (surface modified material).

[0072] The resulting solar cells exhibit an energy conversion efficiency of approximately 14% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the efficiency reduction rate is only 3%. In addition, the resulting solar cells exhibit flame retardancy of V-0 and 5VB or higher according to the UL94 combustion standard.

[0073] (Example 4) A solar cell 400 as shown in Figure 4 is prepared. The preparation procedure is described below. First, a transparent electrode 402 (second electrode) made of indium tin oxide (ITO) with a thickness of 200 nm is prepared by sputtering on the side of a glass film (glass layer 401) made of alkali-free glass with a thickness of 200 μm that is opposite to the light incident surface 400A. Furthermore, a toluene solution of C60-PCBM is applied to the transparent electrode 402 with a bar coater and dried to laminate an electron injection layer 403 with a thickness of 40 nm.

[0074] Next, a solution of lead iodide and methylammonium iodide dissolved in a solvent is applied to the electron injection layer 403, and then dried to laminate a 700 nm thick light absorption layer 404. Then, a solution of 2,2',7,7'-Tetrakis[N,N-di(4-methylphenyl)amino]-9,9'-spirobifluorene (hereinafter referred to as Spiro-OMeTAD) is applied to the light absorption layer 404, and then dried to laminate a hole transport layer 405.

[0075] Next, a counter electrode (first electrode) 406 made of molybdenum (Mo) with a thickness of 50 nm is laminated onto the hole transport layer 405 by sputtering.

[0076] Next, a graphene compound 407 (surface modifier) ​​having the above-described graphene compound structure is applied to the light incident surface 400A side of the glass film (glass layer 401) to a thickness of approximately 2 nm. A silicone rubber sheet 408 (resin layer) with a thickness of 300 μm and a hardness of 60° is then bonded on top of it. Furthermore, a silicone gel 409 containing a UV absorber is applied to the silicone rubber sheet 408 to a thickness of 100 μm, and a 50 μm thick ETFE film 410 (resin layer) is bonded on top of it.

[0077] A silicone gel sealant 411 is applied to the side of the first electrode 406 (a counter electrode made of Mo) opposite to the light incident surface 400A to a thickness of 300 μm, and then a 100 μm thick aluminum foil 412 is attached. In this way, a solar cell 400 is created. The periphery of the solar cell 400 is sealed with a silicone gel sealant 411 and aluminum foil 412 (not shown).

[0078] The resulting solar cell 400 exhibits an energy conversion efficiency of approximately 13% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the decrease in energy conversion efficiency is only 3%. In addition, the resulting solar cell 400 exhibits flame retardancy of V-0 and 5VB or higher according to the UL94 combustion standard.

[0079] (Example 5) A solar cell was fabricated in the same manner as in Example 4, except that instead of coating a graphene compound, an ethanol solution of 3-aminopropyltriethoxysilane was coated and heated at 60°C to form a monolayer of aminopropyl groups (surface modified material).

[0080] The resulting solar cells exhibit an energy conversion efficiency of approximately 14% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the decrease in energy conversion efficiency is only 2%. In addition, the resulting solar cells exhibit flame retardancy of V-0 and 5VB or higher according to the UL94 combustion standard.

[0081] (Example 6) A solar cell is prepared in the same manner as in Example 1, except that a glass layer made of alkali-free glass with a thickness of 50 μm is used instead of a glass layer 308 made of alkali-free glass with a thickness of 100 μm.

[0082] The resulting solar cells exhibit an energy conversion efficiency of approximately 13% for 1 SUN of sunlight. Furthermore, even after 100 bending tests with a 20 mm diameter glass rod, the decrease in energy conversion efficiency is only 3%. In addition, the resulting solar cells exhibit flame retardancy of V-0 and 5VB or higher according to the UL94 combustion standard.

[0083] (Comparative Example 1) A solar cell was prepared in the same manner as in Example 1, except that the graphene compound was not applied.

[0084] The resulting solar cells exhibit an energy conversion efficiency of approximately 13% for 1 SUN of sunlight, but the bonding strength between the glass layer and the resin layer is weak. As a result, combustion material falls out at the 5V standard of the UL94 combustion standard.

[0085] (Comparative Example 2) A solar cell was prepared in the same manner as in Example 1, except that a water vapor barrier film was formed on a 125 μm thick sheet of polyethylene terephthalate (PET) instead of the 100 μm thick alkali-free glass layer 308.

[0086] The resulting solar cells exhibit an energy conversion efficiency of approximately 12% for 1 SUN of sunlight, but the polyethylene terephthalate sheets have an oxygen index of less than 21, resulting in insufficient fire resistance. Consequently, combustion material falls are observed in the 5V standard of the UL94 combustion standard.

[0087] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0088] 100, 300, 400... Solar cell, 100A, 300A, 400A... Light incident surface, 101, 310, 312, 408, 410... Resin layer, 102, 308, 401... Glass layer, 103... Photoelectric conversion layer, 201, 301... Substrate, 202, 306, 406... First electrode, 203, 304, 404... Light absorption layer, 204, 302, 402... Second electrode, 303, 403... Electron injection layer, 305, 405... Hole transport layer, 307, 311, 409... Silicone gel, 309, 407... Graphene compound layer, 310, 408... Silicone rubber sheet (resin layer), 313, 411... Encapsulating material, 314, 412... Aluminum foil.

Claims

1. A solar cell comprising a glass layer with a thickness of 250 μm or less, and a resin layer laminated on the glass layer and having an oxygen index of 22% or more, wherein a material having a zeta potential with a sign different from the zeta potentials of the glass layer and the resin layer is disposed between the glass layer and the resin layer.

2. The solar cell according to claim 1, wherein the resin layer comprises at least one or more resins selected from silicone resin, polyvinyl chloride, polyvinylidene chloride, fluororesin, polyimide, or polycarbonate.

3. The solar cell according to claim 1, wherein the resin layer is a single layer of at least one resin selected from silicone resin, polyvinyl chloride, polyvinylidene chloride, fluororesin, polyimide, or polycarbonate.

4. The solar cell according to claim 1, wherein the resin layer is a laminate comprising at least one or more of the following: silicone resin, polyvinyl chloride, polyvinylidene chloride, fluororesin, polyimide, or polycarbonate.

5. The solar cell according to any one of claims 2 to 4, wherein the silicone resin used is a silicone rubber having a hardness in the range of 10° to 70°.

6. The solar cell according to claim 1, wherein the zeta potential of the glass layer and the resin layer is negative in sign, and the zeta potential of the material is positive in sign.

7. The solar cell according to claim 1, wherein the substance comprises any of aluminum oxide, titanium oxide, zirconium oxide, silicon nitride, a graphene compound, or 3-aminopropyltriethoxysilane.

8. The solar cell according to any one of claims 1 to 4, wherein a transparent electrode layer is laminated on the side of the glass layer opposite to the side of the resin layer.

9. The solar cell according to any one of claims 1 to 4, wherein a photoelectric conversion layer is provided on the side of the glass layer opposite to the resin layer, the photoelectric conversion layer having a layer containing a perovskite compound having a halogen element.

10. The solar cell according to any one of claims 1 to 4, wherein the thickness of the glass layer is in the range of 50 μm to 200 μm.

11. A solar cell according to any one of claims 1 to 4, having a UV shielding layer.

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