Solar cell, solar cell module, and method for manufacturing solar cell

Abstract

To provide a solar cell, a solar cell module, and a method of manufacturing a solar cell that can improve power generation performance.SOLUTION: A solar cell includes a glass substrate, a conductive oxide layer provided on one main surface of the glass substrate, a power generating layer provided on the conductive oxide layer and including oxide semiconductor particles and electrolyte particles, a solid or gel electrolyte layer provided on the power generation layer, and a counter electrode layer provided on the electrolyte layer, and a laminated body projecting toward the counter electrode layer, and a sealing portion formed from a side surface of the glass substrate to a side surface of the counter electrode layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, demand for communication devices that utilize IoT has been growing. For example, services that sense temperature and humidity, transmit data wirelessly, and store big data in the cloud are stimulating new industries. Because so-called IoT devices require power to operate, they often use primary batteries such as button batteries, but the frequency of battery replacement is becoming an issue.

[0003] Energy harvesting power sources that combine solar cells and secondary batteries have recently been increasingly proposed as a means to reduce the frequency of battery replacement. Crystalline silicon solar cells are the most widely used solar cell. Crystalline silicon solar cells are primarily used for high-power solar power generation, such as rooftop solar panels for home use and large-scale solar power plants. Crystalline silicon solar cells are often used outdoors due to their high photoelectric conversion efficiency when exposed to sunlight. Therefore, while crystalline silicon solar cells are sometimes used for outdoor IoT devices, amorphous silicon solar cells and organic solar cells, which have high power generation capacity when exposed to indoor light, are increasingly being used for indoor IoT devices. In particular, organic solar cells, which generate twice the power per unit area compared to conventional amorphous silicon solar cells, have recently been developed, accelerating their market development.

[0004] Among organic solar cells, in the manufacturing process of dye-sensitized solar cells, measures have been taken to reduce warping of the glass substrate on which the power generation layer is formed, from the viewpoint of sealing stability of the electrolyte solution. For example, it has been reported that warping of the glass substrate is prevented by applying a semiconductor particle paste to a glass substrate on which a transparent conductive layer has been formed, and then performing an acid treatment or a water vapor treatment (see, for example, Patent Document 1).

[0005] Furthermore, when an attempt is made to thin the glass substrate in order to make the solar cell thinner, variations in power generation performance are likely to occur, and it is known that this variation is caused by warpage deformation of the glass substrate with a transparent conductive layer. In order to provide a glass substrate with a transparent conductive layer that is less likely to cause variations in power generation performance and has excellent sealing properties with a sealing material, there have been reported documents that limit the warpage to a certain range (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-35591 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-44426 Summary of the Invention [Problem to be solved by the invention]

[0007] In the method for treating the semiconductor layer of a solar cell described in Patent Document 1, water vapor or acid treatment is performed while preventing warping of the glass substrate, thereby reducing binder residue in the semiconductor layer and enabling the glass substrate to be heated at a lower temperature. However, the effectiveness of water vapor treatment is limited, and the mechanism by which binder residue is completely decomposed is currently unknown. Acid treatment is known to be highly effective and to decompose binder residue more rapidly than water vapor treatment, but on the other hand, acid corrodes transparent conductive layers such as ITO and FTO, which increases the resistance of the transparent electrode substrate in the first place.

[0008] Patent Document 2 states that variations in power generation are caused by warpage of the conductive film-attached glass substrate. Therefore, it explains that the purpose is to limit the warpage of the conductive film-attached glass substrate to a certain range. The amount of warpage W of the transparent conductive layer-attached glass substrate is specified, and the amount of warpage W of the glass substrate after heat treatment at 500°C for 30 minutes is set to 0.5 μm / cm. 2 Below, especially 0.3 μm / cm 2 It is preferable that the thermal expansion coefficient of the glass be less than or equal to the specified value. In order for the glass substrate to meet this value, the thermal expansion coefficient of the glass is specified and controlled, but this method limits the types of glass that can be used in solar cells. Furthermore, the glass composition is likely to have to be custom-made, which raises concerns about significantly higher costs. Furthermore, in the case of dye-sensitized solar cells, the higher the heat treatment temperature, the less binder residue there is in the power generation layer, and the more advanced the necking of the semiconductor particles, which tends to improve power generation performance. Therefore, if the heat treatment temperature is set below 550°C to reduce the amount of warpage, the problem arises that the improvement in power generation performance is suppressed.

[0009] The present invention has been made in view of the above-mentioned problems, and has an object to provide a solar cell, a solar cell module, and a method for manufacturing a solar cell that can improve power generation performance. [Means for solving the problem]

[0010] The solar cell according to the present invention comprises a glass substrate, a conductive oxide layer provided on one main surface of the glass substrate, a power generation layer provided on the conductive oxide layer and including oxide semiconductor particles and electrolyte particles, a solid or gel electrolyte layer provided on the power generation layer, and a counter electrode layer provided on the electrolyte layer, the stack having a convex shape facing the counter electrode layer, and a sealing portion formed from a side surface of the glass substrate to a side surface of the counter electrode layer.

[0011] In the solar cell, the density of the oxide semiconductor particles may be dense on the glass substrate side and sparse in the stacking direction.

[0012] In the solar cell, when the length of the long side of the glass substrate is L cm and the maximum depth of the recess formed by the warp is D μm, the amount of warp of the glass substrate is W=D / L 2 is 4.16 μm / cm 2 Above, 17.63μm / cm 2 It may be the following:

[0013] In the solar cell, the sealing portion may be in contact with a side surface of the conductive oxide layer, a side surface of the power generation layer, a side surface of the electrolyte layer, and a side surface of the counter electrode layer.

[0014] In the solar cell, the thickness from the glass substrate to the counter electrode layer may be 2 mm or less.

[0015] In the solar cell, the counter electrode layer may include a metal foil disposed along the main surface of the glass substrate.

[0016] In the solar cell, the sealing portion may be made of resin.

[0017] In the solar cell, a dye may be supported on the surface of the oxide semiconductor particles in the power generation layer.

[0018] The solar cell module of the present invention comprises first and second solar cells arranged adjacent to each other, each solar cell comprising: a glass substrate having a warp convexly curved toward one main surface of the glass substrate; a conductive oxide layer provided on the one main surface of the glass substrate; a power generation layer provided on the conductive oxide layer and including oxide semiconductor particles and electrolyte particles; a solid or gel-like electrolyte layer provided on the power generation layer; and a counter electrode layer provided on the electrolyte layer; and a sealant formed between the first solar cell and the second solar cell, the sealant extending from a side surface of the conductive oxide layer in the first solar cell to a side surface of the counter electrode layer and extending from a side surface of the conductive oxide layer in the second solar cell to a side surface of the counter electrode layer, sealing the side surface of the electrolyte layer in the first solar cell and the side surface of the electrolyte layer in the second solar cell.

[0019] A method for manufacturing a solar cell according to the present invention includes preparing a glass substrate having a conductive oxide layer on one main surface thereof, arranging oxide semiconductor particles on the conductive oxide layer and firing the resulting layer to form a power generation layer of the oxide semiconductor particles, warping the glass substrate so as to be convex toward the one main surface thereof, and immersing electrolyte particles in the power generation layer to impregnate the power generation layer with the electrolyte particles and forming a solid or gel electrolyte layer on the power generation layer, forming a counter electrode layer on the electrolyte layer, and forming a sealant from a side surface of the conductive oxide layer to a side surface of the counter electrode layer to seal the side surface of the electrolyte layer.

[0020] In the method for manufacturing a solar cell, the temperature during the firing may be 550°C or higher and 650°C or lower.

[0021] In the method for manufacturing a solar cell, after firing the power generation layer and before forming the counter electrode layer, the power generation layer may be immersed in a dye, thereby allowing the power generation layer to contain the dye. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a solar cell, a solar cell module, and a method for manufacturing a solar cell that can improve power generation performance. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view illustrating a stack structure of a dye-sensitized solar cell according to an embodiment. [Figure 2] 1(a) to 1(c) are diagrams illustrating immersion in a power generation layer. [Figure 3] 1(a) to 1(c) are diagrams illustrating examples of length L and maximum warpage D. [Figure 4] FIG. 1(a) is a plan view of the solar cell module, and FIG. 1(b) is a side view of the solar cell module. [Figure 5] FIG. 1 is a flow diagram illustrating a method for manufacturing a dye-sensitized solar cell. [Figure 6] 10(a) and 10(b) are diagrams illustrating immersion in a power generation layer. DETAILED DESCRIPTION OF THE INVENTION

[0024] (Embodiment) 1 illustrates an example of the layered structure of a dye-sensitized solar cell 100 according to an embodiment. The dye-sensitized solar cell 100 has a rectangular shape in a plan view, and has a structure in which a light-transmitting electrode layer 20, a back electron transfer prevention layer 30, a power generation layer 40, an electrolyte layer 50, and a counter electrode layer 60 are layered in this order on one main surface of a glass substrate 10. A structure in which the power generation layer 40 is formed on the light-transmitting electrode layer 20 and the back electron transfer prevention layer 30 is not required may also be used. The thickness of the glass substrate used here is preferably 0.1 mm to 3 mm.

[0025] The light-transmitting electrode layer 20 is a conductive oxide layer having light transparency. The thickness of this light-transmitting electrode layer 20 is, for example, about 0.1 μm to 0.5 μm, and it is an ITO (Indium Tin Oxide) layer. Instead of the ITO layer, an FTO (Fluorine-doped Tin Oxide) layer, a zinc oxide layer, a laminated film of an indium-tin composite oxide layer and a silver layer, an antimony-doped tin oxide layer, or the like may be used as the light-transmitting electrode layer 20.

[0026] The reverse electron transfer prevention layer 30 is, for example, a layer of oxide semiconductor particles. The reverse electron transfer prevention layer 30 has a thickness of, for example, about 1 nm to 50 nm.

[0027] The power generation layer 40 is a layer of oxide semiconductor particles formed in layers. A sensitizing dye is supported on groups on the surface of the oxide semiconductor particles. The oxide semiconductor particles are, for example, titanium oxide particles. The oxide semiconductor particles may also be particles of an oxide of any of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, Cr, and Nb. Alternatively, particles of a perovskite-type oxide such as SrTiO3 or CaTiO3 may also be used.

[0028] The sensitizing dye may be, for example, CYC-B11(K). Other examples of the metal complex dye include transition metal complexes such as ruthenium-cis-diaqua-bipyridyl complex, ruthenium-tris complex, ruthenium-bis complex, osmium-tris complex, and osmium-bis complex. Examples of the metal complex dye include zinc-tetra(4-carboxyphenyl)porphyrin and iron-hexacyanide complex. Examples of the organic dye include 9-phenylxanthene dyes, coumarin dyes, acridine dyes, triphenylmethane dyes, tetraphenylmethane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes, merocyanine dyes, xanthene dyes, and carbazole compound dyes.

[0029] The electrolyte layer 50 is composed of an electrolyte and a solid or gel-like polymer. The electrolyte layer 50 is a solid or gel-like layer. For example, 1,3-dimethylimidazolium iodide (DMII) can be used as the electrolyte. In addition to DMII, iodine salts such as pyridinium salts, imidazolium salts, and triazolium salts, which are solid at around room temperature or molten at room temperature, can also be used as the ionic liquid. Examples of such room-temperature molten salts include quaternary ammonium iodide compounds such as 1-methyl-3-propylimidazolium iodide, 1-butyl-3-methylimidazolium iodide (BMII), and 1-ethyl-pyridinium iodide. Alternatively, organic semiconductor materials such as molten salts containing redox pairs, oxadiazole compounds, and pyrazoline compounds can also be used. Metal halide materials such as copper iodide and copper bromide can also be used. The polymer used in the solid or gel electrolyte is not particularly limited as long as it can form a gel together with the electrolyte solution, and examples thereof include polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyester, polyamide, polycarbonate, polyimide, polyurethane, polyurea, polymethyl methacrylate, polyvinyl acetate, polyvinyl chloride, polyvinylidene fluoride, and ethyl cellulose. Preferred polymers include polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylonitrile, and polyvinylidene fluoride. Clay examples include silicon dioxide particles, zirconium oxide particles, titanium oxide particles, and montmorillonite mineral particles. The polymer content in the gel electrolyte is 1% by mass or more and 50% by mass or less. A content of 1% by mass or more allows for good retention of the electrolyte solution and prevention of leakage. A content of 50% by mass or less allows for good ionic conductivity. The weight-average molecular weight of the polymer is preferably 2,000 to 10,000,000. When the molecular weight is 2000 or more, the electrolyte gels and is no longer liquid, making it easy to form a sealing layer, which will be described later.When the molecular weight is 10 million or less, it is possible to maintain good ionic conductivity.The solid electrolyte contained in the electrolyte layer 50 is also contained in the power generation layer 40 .

[0030] 1, the electrolyte layer 50 is laminated below the power generation layer 40, but the power generation layer 40 is made up of layers of oxide semiconductor particles, with the electrolyte layer 50 permeating into the gaps between the layers. In reality, the electrolyte layer 50 may be completely permeated and not present in a layered form, or may only remain in a thin layer after permeation. The total thickness of the power generation layer 40 and the electrolyte layer 50 is, for example, approximately 5 μm to 100 μm.

[0031] The counter electrode layer 60 includes, for example, a catalyst layer 61 and a metal foil 62, which are provided in this order from the electrolyte layer 50 side. The metal foil 62 is, for example, a titanium foil and has a thickness of 50 μm to 200 μm. The catalyst layer 61 is, for example, a platinum layer and has a thickness of 0.01 μm to 1 μm. The catalyst layer 61 can be made of metals with catalytic function, such as palladium, rhodium, and indium, in addition to platinum. The catalyst layer may also be made of graphite. The catalyst layer 61 may also be made of platinum-supported carbon, indium-tin composite oxide, antimony-doped tin oxide, or fluorine-doped tin oxide. Other materials include organic semiconductors such as poly(3,4-ethylenedioxythiophene) (PEDOT) and polythiophene. The counter electrode layer 60 has a thickness of, for example, approximately 50 μm to 200 μm.

[0032] A resin sealant 70 (sealing portion) is provided on the side surface of the dye-sensitized solar cell 100 to prevent the power generation layer 40 and the electrolyte layer 50 from being exposed to the atmosphere. The sealant 70 is provided from the side surface of the glass substrate 10, across the side surface of the light-transmitting electrode layer 20, and onto the side surface of the counter electrode layer 60. Because the sealant 70 is made of resin, it has substrate conformability during formation and impact resistance after curing. The sealant 70 is in contact with at least a portion of the side surface of the light-transmitting electrode layer 20, at least a portion of the side surface of the back electron transfer prevention layer 30, at least a portion of the side surface of the power generation layer 40, at least a portion of the side surface of the electrolyte layer 50, and at least a portion of the side surface of the counter electrode layer 60. The sealant 70 may extend to a portion of the surface of the glass substrate 10 opposite the light-transmitting electrode layer 20. The sealant 70 may also extend to a portion of the surface of the counter electrode layer 60 opposite the electrolyte layer 50.

[0033] In such a dye-sensitized solar cell 100, when light is incident on the sensitizing dye in the power generation layer 40 from the glass substrate 10, the sensitizing dye in the power generation layer 40 becomes excited, and electrons move from the sensitizing dye to the oxide semiconductor particles in the power generation layer 40. In the power generation layer 40 and the electrolyte layer 50, the electrolyte dissociates into ions, and a current flows between the counter electrode layer 60 and the light-transmitting electrode layer 20. For example, if the electrolyte is DMII, DMII is converted into DMI. + and iodide ions (I - ) and dissociates into iodide ion (I - ) and iodine molecules (I2) combine to form triiodide ions (I3 - ) is also produced. - ) is an example of a halide ion, and triiodide ion (I3 - ) is an example of a trihalide ion. Triiodide ion (I3 - ) accepts electrons from the counter electrode layer 60 and converts into iodide ions (I - ) and the iodide ion (I - ) transfers electrons to the sensitizing dye. The potential difference between the light-transmitting electrode layer 20 and the counter electrode layer 60 is such that the iodide ions (I - ) and triiodide ion (I3 -) and the Fermi level of the oxide semiconductor particles. Through the above-mentioned actions, the dye-sensitized solar cell 100 generates electricity in response to incident light.

[0034] In such a dye-sensitized solar cell 100, a light-transmitting electrode layer 20 and a reverse electron transfer prevention layer 30 are formed on a glass substrate 10, and a power generation layer 40 is baked on the reverse electron transfer prevention layer 30. After this, the power generation layer 40 is impregnated with a sensitizing dye, and then the power generation layer 40 is impregnated with a solid electrolyte, thereby forming an electrolyte layer 50 in which the power generation layer 40 contains the sensitizing dye and solid electrolyte. In this way, the dye-sensitized solar cell 100 can be obtained. The step of impregnating the power generation layer 40 with the sensitizing dye and solid electrolyte is an important step in order to obtain a sufficient amount of power generation.

[0035] As the firing temperature of the power generation layer 40 increases, necking between the oxide semiconductor particles that form the skeleton of the power generation layer 40 progresses. This necking refers to the growth of junctions between adjacent particles. Therefore, the space between the particles narrows due to necking. In other words, the porosity of the power generation layer 40 decreases. When the porosity of the power generation layer 40 decreases, the electronic conductivity between the oxide semiconductor particles improves, but it becomes difficult for the sensitizing dye to adsorb or the solid electrolyte to penetrate deep into the power generation layer 40. If the sensitizing dye or solid electrolyte is not present deep in the power generation layer 40, a problem occurs in which the amount of power generation decreases.

[0036] In the dye-sensitized solar cell 100 according to this embodiment, the electrolyte layer 50 is solid or gel-like, not liquid like an electrolyte solution, so there is no risk of liquid leakage. Furthermore, with regard to the sealant 70 in FIG. 1 , the sealant is provided from the side surface of the glass substrate 10 to the side surface of the counter electrode layer 60, or from the side surface of the counter electrode to the periphery of the underside surface of the counter electrode. However, because the electrolyte layer 50 is not liquid, no liquid leakage occurs from gaps in the adhesive surface. Therefore, the sealing stability is improved compared to cells that use an electrolyte solution.

[0037] We also focused on the warpage of the glass substrate 10. As illustrated in FIG. 1, the glass substrate 10 is prepared with the counter electrode layer 60 pre-formed. The subsequent sintering of the power generation layer 40 and subsequent layers results in warping that convexly curves toward the counter electrode layer. This warping is presumably due to the high-temperature processing performed when laminating the power generation layer 40 and other layers on the glass substrate 10. After sintering and cooling, the entire glass substrate 10 curves toward the counter electrode layer 60 due to the difference in the thermal expansion coefficients of the two materials and the shrinkage rates at which they return to their original shape after sintering. Because the thickness of the glass substrate 10 is significantly greater than the thickness of the layers laminated on the glass substrate, the film formation after sintering of the power generation layer 40 also curves and curves in a way that follows the warpage of the glass substrate 10, resulting in a convex curve. This results in the entire solar cell being warped.

[0038] Here, we focus on the distribution of the oxide semiconductor particles 41. For example, if oxide semiconductor particles 41 are stacked side by side on a flat glass substrate 10, the particles will be arranged in a regular layer if their shape is assumed to be a virtual circle. If the glass substrate 10 subsequently warps due to heat treatment, gaps will appear closer to the surface. That is, if the oxide semiconductor particles 41 are aligned before warping and then the power generation layer 40 warps due to the warping of the substrate, as shown in FIG. 2( a), the oxide semiconductor particles 41 will be dense on the glass substrate 10 (ITO) side, and the spacing between the oxide semiconductor particles 41 will increase and become sparser from the glass substrate 10 (ITO) toward the stacking direction (upward in the figure). Therefore, as shown in FIG. 2( b), when the power generation layer 40 is immersed in the sensitizing dye 42, the spacing between the particles on the surface of the power generation layer 40 is increased, allowing the sensitizing dye 42 to penetrate deep into the power generation layer 40. Furthermore, the increased spacing increases the gaps between the particles, resulting in a greater amount of sensitizing dye 42 adsorbed to the power generation layer 40. 2(c), when the electrolyte particles 43 are immersed in the power generation layer 40, the electrolyte particles 43 can also penetrate deep into the power generation layer 40, increasing the amount of electrolyte particles 43 packed into the power generation layer 40. Therefore, the amount of power generated in the power generation layer 40 increases.

[0039] Here, the amount of warpage W of the glass substrate 10 will be explained. The glass substrate 10 has a substantially square shape in plan view, as exemplified in FIG. 3(a). Alternatively, the glass substrate 10 has a substantially rectangular shape in plan view, as exemplified in FIG. 3(b). In this manner, the glass substrate 10 has a substantially rectangular shape in plan view. In this substantially rectangular shape, the length of the long side of the rectangle is L (cm). The maximum depth of the recess formed by the warpage is the maximum warpage depth D (μm). The amount of warpage W is calculated by the ratio D / L 2 (μm / cm 2 In other words, regardless of whether the glass substrate 10 is square or rectangular, the amount of warpage W is defined assuming that the shape of the glass substrate 10 is substantially square in plan view. 2 is an area, so the amount of warpage W indicates how much the glass substrate 10 has deformed per area.

[0040] From the viewpoint of allowing a sufficient amount of the sensitizing dye 42 and the electrolyte particles 43 to penetrate into the power generation layer 40, it is preferable that the warpage W of the glass substrate 10 is large. For example, the warpage W of the glass substrate 10 is 1.38 μm / cm 2 More than 20.18μm / cm 2 The range is preferably 3.45 μm / cm 2 More than 19.62μm / cm 2 More preferably, the range is 4.16 μm / cm 2 More than 17.63μm / cm 2 It is more preferable that the warpage W of the glass substrate 10 is within the range of 1.38 μm / cm. 2 Above, 3.45μm / cm 2 Above, 4.16μm / cm 2 Even with the above, peeling of the sealing material 70 can be suppressed.

[0041] On the other hand, if the warpage amount W of the glass substrate 10 is too large, when an external force is applied from the counter electrode layer 60 side or when the ambient temperature fluctuates, peeling of the sealing material 70 may occur due to the thickness of the glass substrate. Therefore, the warpage amount W of the glass substrate 10 is set to 1.38 μm / cm 2 More than 20.18μm / cm 2 The range is preferably 3.45 μm / cm 2 More than 19.62μm / cm 2 More preferably, the range is 4.16 μm / cm 2 More than 17.63μm / cm 2 The following ranges are more preferred:

[0042] In the dye-sensitized solar cell 100 according to this embodiment, the glass substrate 10, which is prone to warping, is actively used, so there is no need to use an expensive glass substrate that does not warp due to heat treatment. Therefore, for example, general soda glass can be used, which allows for reduction in material costs.

[0043] It is preferable to use a solid electrolyte containing a polymer for the electrolyte layer 50. While liquid electrolytes have fluidity, a solid electrolyte containing a polymer can, in principle, also serve as a structural material. Because there is no risk of electrolyte leakage, the instability of sealing caused by warping of the glass substrate 10 is improved, improving reliability.

[0044] Furthermore, if the catalyst layer 61 and metal foil 62 of the counter electrode layer 60 are warped to follow the warp of the glass substrate 10, a parabolic effect is obtained. This parabolic effect allows light reflected by the metal foil 62 to be concentrated at the center of the glass substrate 10, thereby improving power generation performance. The metal foil 62 of the counter electrode layer 60 curves to follow the warp of the glass substrate 10. Alternatively, the parabolic structure contributes to an increase in the amount of power generation.

[0045] Unlike the structure of this embodiment, in solar cells that use an electrolyte, the glass substrate is required to have a certain rigidity (stability) and a certain thickness to prevent leakage of the electrolyte. For example, a thickness of more than 2 mm is required. In this embodiment, the thickness from the glass substrate 10 to the counter electrode layer 60 refers to the total thickness of the glass substrate 10, the light-transmitting electrode layer 20, the back electron transfer prevention layer 30, the power generation layer 40, and the counter electrode layer 60. However, if the dye-sensitized solar cell 100 is fabricated without the back electron transfer prevention layer 30, for example, the total thickness refers to the glass substrate 10, the light-transmitting electrode layer 20, the power generation layer 40, and the counter electrode layer 60. In contrast, in the dye-sensitized solar cell 100 of this embodiment, leakage of the electrolyte does not need to be considered, and the thickness from the glass substrate 10 to the counter electrode layer 60 can be 2 mm or less.

[0046] Fig. 4(a) is a plan view of a solar cell module 200 in which a plurality of dye-sensitized solar cells 100 are arranged adjacent to one another in a matrix. Fig. 4(b) is a side view of the solar cell module 200. Although not shown, the plurality of dye-sensitized solar cells 100 are mounted by soldering to wiring on a printed circuit board, and, for example, the dye-sensitized solar cells 100 can be electrically connected in series to obtain an electrical output. In the solar cell module 200, the electrical output of the plurality of dye-sensitized solar cells 100 can be obtained, thereby increasing the amount of power generation.

[0047] As shown in Figure 4(b), warped dye-sensitized solar cells 100 are arranged side by side. Here, the encapsulant 70 maintains overall flatness. On the other hand, if the size of Figure 4(a), in this case a 4 x 2-sheet area, were to be realized with a single glass substrate, the solar cell would warp significantly, resulting in a thick solar cell. On the other hand, using 4 x 2 sheets allows for a flat overall structure when the encapsulant is attached, thereby suppressing warping of a single solar cell made up of multiple sheets. Furthermore, adjacent dye-sensitized solar cells 100 can share the encapsulant 70. Sharing the encapsulant 70 means, for example, that the encapsulants 70 of adjacent dye-sensitized solar cells 100 are integrated and encapsulated with the same resin. If encapsulants were applied to each solar cell and then assembled, twice the amount of encapsulant between adjacent solar cells would be required. However, because there is no electrolyte leakage, cells without encapsulant can be arranged side by side, and resin can then be filled between the cells after arranging them. Therefore, the overall size of the solar cell can be made smaller for the same amount of power generation, reducing manufacturing costs.

[0048] Next, a description will be given of a method for manufacturing the dye-sensitized solar cell 100. Fig. 5 is a flow diagram illustrating an example of the method for manufacturing the dye-sensitized solar cell 100.

[0049] (Preparation of glass substrate and formation of light-transmitting electrode layer) First, a glass substrate 10 having opposing first and second main surfaces is prepared. Of these surfaces, the first main surface is the incident surface through which light is incident. The glass substrate 10 is a glass substrate having a roughly rectangular shape (square in this case) in plan view, with each side having a length of approximately 5 mm to 40 mm, and in this embodiment, for example, each side is 15 mm. The thickness of the glass substrate 10 is approximately 0.1 mm to 3 mm, and in this embodiment, it is 1.1 mm. A light-transmitting electrode layer 20 is formed on the glass substrate 10. Note that a light-transmitting electrode layer 20 is previously laminated on the surface opposite the incident surface, i.e., the surface on which lamination will be performed.

[0050] (Step of forming reverse electron transfer prevention layer) As mentioned above, warping occurs due to subsequent high-temperature treatment. In this process, an alkoxide containing the metal that constitutes the target oxide (e.g., titanium alkoxide) is prepared in an alcohol solution. The alcohol solution containing the oxide is applied to the portion of the light-transmitting electrode layer 20 other than the extraction electrode portion, and then the alcohol solution is heated and dried to form the back electron transfer prevention layer 30. The extraction electrode portion is a right-angled triangle with a length of 3 mm and a width of 3 mm at one corner. The drying temperature in this process is in the range of 450°C to 650°C.

[0051] (Formation process of power generation layer and electrolyte layer) Next, a paste containing oxide semiconductor particles with particle sizes of approximately 5 nm to 50 nm (e.g., 40 nm) is applied onto the back electron transfer prevention layer 30 by screen printing, and then heated and baked to remove organic components, forming the power generation layer 40. The heating temperature is approximately 450°C to 650°C, and the drying time is 10 to 120 minutes. The heating temperature is preferably 550°C to 650°C, more preferably 580°C to 640°C, and even more preferably 600°C to 630°C. While the paste is not particularly limited, for example, PST-30NRD, a titanium oxide paste manufactured by JGC Catalysts and Chemicals, is used. Alternatively, oxide semiconductor particles of any of Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, Cr, and Nb may be used.

[0052] After baking, the glass substrate 10, which was relatively flat as shown in FIG. 6(a), becomes warped as shown in FIG. 6(b). The glass substrate 10 is then immersed in an organic solution containing a sensitizing dye 42, causing the sensitizing dye 42 to be adsorbed onto the surfaces of the oxide semiconductor particles 41 that constitute the power generation layer 40. An organic solution is prepared by adding the sensitizing dye 42 to an organic solvent in which acetonitrile and t-butanol are mixed in a 1:1 volume ratio. The concentration of the sensitizing dye in the organic solution is 0.1 mM to 1 mM, for example, 0.2 mM. The organic solution is then kept at a temperature of 0°C to 80°C (for example, 50°C), and the glass substrate 10 is left standing in the organic solution for 1 hour to 12 hours, causing the sensitizing dye 42 to be adsorbed onto the oxide semiconductor particles 41.

[0053] Next, iodine, an electrolyte, acetonitrile, and polyethylene oxide with a molecular weight of 1,000,000 are mixed uniformly to form a solid electrolyte precursor. Then, 0.1 μL to 50 μL of this solid electrolyte precursor is dropped onto the power generation layer 40, impregnating the power generation layer 40 with the solid electrolyte precursor. The power generation layer 40 is then heated to 50°C to 150°C and maintained at this temperature for 1 to 60 minutes, thereby volatilizing the excess acetonitrile contained in the solid electrolyte precursor, and the solid electrolyte precursor on the power generation layer 40 becomes the electrolyte layer 50. The power generation layer 40 is then returned to room temperature.

[0054] (Process for forming counter electrode layer) Next, the counter electrode layer 60 is placed above the electrolyte layer 50. The counter electrode layer 60 is brought into close contact with the electrolyte layer 50 while removing any air bubbles from between the electrolyte layer 50 and the counter electrode layer 60. Note that by performing this step in a reduced pressure atmosphere or in a vacuum, air bubbles are less likely to remain between the electrolyte layer 50 and the counter electrode layer 60.

[0055] (Sealant forming process) Next, a sealant 70 is formed from the side surface of the glass substrate 10 on which the light-transmitting electrode layer 20 is formed to the periphery of the side surface or surface of the counter electrode layer 60 to seal the side surface of the electrolyte layer 50 .

[0056] According to the manufacturing method of this embodiment, the spacing between the oxide semiconductor particles 41 increases from the stacking surface (the surface opposite to the incident surface) of the glass substrate 10 toward the counter electrode layer in the power generation layer 40, and the density also gradually decreases toward the counter electrode layer 60, allowing the sensitizing dye 42 to penetrate deep into the power generation layer 40. This allows the electrolyte particles 43 to penetrate deep into the power generation layer 40, increasing the amount of electrolyte particles 43 packed in the power generation layer 40. This increases the amount of power generated in the power generation layer 40. [Example]

[0057] (Examples 1 to 9 and Comparative Example 1) ITO was previously formed on a 15mm x 15mm x 1.1mm glass sheet. An alcohol solution prepared from titanium alkoxide was applied to the ITO surface and heated at 550°C to form a reverse electron transfer prevention layer. A 1cm thick titanium oxide paste (PST-30NRD) manufactured by JGC Catalysts and Chemicals was applied to the FTO surface with the reverse electron transfer prevention layer by screen printing. 2 The titanium oxide paste was printed over an area of ​​1000mJ. The applied titanium oxide paste was heated for approximately 30 minutes to eliminate the organic components contained in the titanium oxide paste. The power-generating layer thus obtained was immersed in a dye solution (dye: CYC-B11(K) at a concentration of 0.2mM) dissolved in an organic solvent consisting of a 1:1 volumetric mixture of acetonitrile and t-butanol, and left to stand at 50°C for 4 hours to allow dye adsorption, resulting in the negative electrode.

[0058] The heating temperature when forming the power generation layer was 630°C in Example 1, 450°C in Comparative Example 1, 550°C in Example 2, 580°C in Example 3, 600°C in Example 4, 620°C in Example 5, 630°C in Example 6, 640°C in Example 7, 650°C in Example 8, and 670°C in Example 9.

[0059] For the positive electrode, a 15mm x 15mm x 0.1mm titanium foil substrate was prepared separately, with a 3mm x 3mm right-angled triangle cut off at one corner. Platinum was sputtered onto the surface of this titanium foil to create the positive electrode. The negative electrode, which had a power generation layer formed by immersing a solid electrolyte, was then returned to room temperature and placed opposite the platinum side of the positive electrode. The positive and negative electrodes were then heated and pressed together under reduced pressure or in a vacuum. While still pressed together, a sealant resin was applied to the sides using a dispenser, and the sides were sealed by irradiating the sealant with UV light, creating a small dye-sensitized solar cell.

[0060] In Example 1, the thickness of the glass substrate used was 3 mm. The thickness of the obtained dye-sensitized solar cell was 4 mm. In Examples 2 to 9 and Comparative Example 1, the thickness of the glass substrate used was 1 mm. The thickness of the obtained dye-sensitized solar cell was 2 mm.

[0061] The warpage W of the glass substrate was measured using a film thickness meter (DEKTAC) for each of the dye-sensitized solar cells of Examples 1 to 9 and Comparative Example 1. In Example 1, the warpage W was 4.21 μm / cm 2 In Comparative Example 1, the amount of warpage W was 0 μm / cm 2 In Example 2, the amount of warpage W was 1.38 μm / cm 2 In Example 3, the amount of warpage W was 3.45 μm / cm 2 In Example 4, the amount of warpage W was 4.16 μm / cm 2 In Example 5, the amount of warpage W was 10.24 μm / cm 2 In Example 6, the amount of warpage W was 17.63 μm / cm 2 In Example 7, the amount of warpage W was 19.62 μm / cm 2 In Example 8, the amount of warpage W was 20.18 μm / cm 2 In Example 9, the amount of warpage W was 22.43 μm / cm 2 It was.

[0062] An IV meter was used for each of the dye-sensitized solar cells of Examples 1 to 9 and the Comparative Example. Standard white light of 200 Lux produced by an LED light was irradiated at room temperature, and the initial power generation was measured. Power generation of 5 μW or more was evaluated as very good (◯), power generation of 4.7 μW or more but less than 5 μW was evaluated as fair (△), and power generation of less than 4.7 μW was evaluated as poor (×). The results are shown in Table 1. [Table 1]

[0063] In Examples 1 to 9, the amount of power generation was judged to be good ("△") or very good ("◯"). This is thought to be because the warping of the glass substrate allowed the solid electrolyte to be impregnated to a sufficient depth in the power generation layer. Another factor is thought to be the ability to impregnate the sensitizing agent to a sufficient depth in the power generation layer. In Comparative Example 1, the amount of power generation was judged to be poor ("×"). This is thought to be because the glass substrate was not warped.

[0064] Furthermore, since Example 2 obtained a result judging that the amount of power generation was somewhat good, it is understood that the heating temperature when forming the power generation layer is preferably 550°C or higher. Since the amounts of power generation in Examples 3 to 9 were greater than in Example 2, it is understood that the heating temperature when forming the power generation layer is more preferably 580°C or higher. Since the amounts of power generation in Examples 4 to 9 were greater than in Examples 2 and 3, it is understood that the heating temperature when forming the power generation layer is even more preferably 600°C or higher.

[0065] Next, the sealing property was evaluated. For each of the dye-sensitized solar cells of Examples 1 to 9 and Comparative Example 1, the adhesive portion of the sealing material of the dye-sensitized solar cell was visually checked, and if there were no unadhered portions, it was judged as "no peeling", and if there were partial unadhered portions, it was judged as "peeling". The results are shown in Table 1. As shown in Table 1, Examples 1 to 7 were judged as "no peeling", and Examples 8 and 9 were judged as "peeling". Therefore, the amount of warpage W was 17.63 μm / cm 2It was found that the sealing property was good if the thickness was less than this.

[0066] Subsequently, the deterioration during the cycle test was evaluated. For each of the dye-sensitized solar cells of Examples 1 to 8, the number of element failures among 20 samples after the temperature (80°C) cycle test was investigated. In Examples 1 to 6, the number of element failures was zero. In contrast, in Examples 7 to 9, some element failures occurred. Therefore, the amount of warpage W was 17.63 μm / cm 2 It was found that the cycle characteristics were also good if the temperature was below this range.

[0067] Furthermore, since the number of element failures after the cycle test was lower in Examples 1 to 8 than in Example 9, it is clear that the heating temperature when forming the power generation layer is preferably 650°C or lower. Furthermore, since the number of element failures after the cycle test was lower and the number of peeled-off elements was lower in Examples 1 to 7 than in Examples 8 and 9, it is clear that the heating temperature when forming the power generation layer is more preferably 640°C or lower. Furthermore, since the number of element failures after the cycle test was lower in Examples 1 to 6 than in Examples 7 to 9, it is clear that the heating temperature when forming the power generation layer is even more preferably 630°C or lower.

[0068] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. For example, although the above focuses on the dye-sensitized solar cell 100, each embodiment can also be applied to other organic solar cells. [Explanation of symbols]

[0069] 10 Glass substrate 20 Light-transparent electrode layer 30 Reverse electron transfer prevention layer 40 Power Generation Layer 41 Oxide semiconductor particles 42 Sensitizing dyes 43 Electrolyte particles 50 electrolyte layer 60 Counter electrode layer 70 Encapsulating material 100 Dye-sensitized solar cells

Claims

1. a laminate including a glass substrate, a conductive oxide layer provided on one main surface of the glass substrate, a power generation layer provided on the conductive oxide layer and including oxide semiconductor particles and electrolyte particles, a solid or gel electrolyte layer provided on the power generation layer, and a counter electrode layer provided on the electrolyte layer, the laminate being convex toward the counter electrode layer; a sealing portion formed from a side surface of the glass substrate to a side surface of the counter electrode layer, In the power generation layer, the density of the oxide semiconductor particles is dense on the glass substrate side and sparse in the stacking direction.

2. In the main surface of the glass substrate that is approximately rectangular in plan view, when the length of the long side is L cm and the maximum depth of the recess formed by the warp is D μm, the amount of warp of the glass substrate is W=D / L ２ is 4.16 μm / cm ２ Above, 17.63μm / cm ２ The solar cell according to claim 1 , wherein:

3. 3. The solar cell according to claim 1, wherein the sealing portion is in contact with a side surface of the conductive oxide layer, a side surface of the power generation layer, a side surface of the electrolyte layer, and a side surface of the counter electrode layer.

4. The solar cell according to claim 1 , wherein a thickness from the glass substrate to the counter electrode layer is 2 mm or less.

5. The solar cell according to claim 1 , wherein the counter electrode layer comprises a metal foil disposed along the main surface of the glass substrate.

6. The solar cell according to claim 1 , wherein the sealing portion is made of a resin.

7. The solar cell according to claim 1 , wherein a dye is supported on the surfaces of the oxide semiconductor particles of the power generation layer.

8. a first solar cell and a second solar cell arranged adjacent to each other, the first solar cell and the second solar cell comprising: a glass substrate having a warp convexly curved toward one main surface of the glass substrate; a conductive oxide layer provided on the one main surface of the glass substrate; a power generation layer provided on the conductive oxide layer and including oxide semiconductor particles and electrolyte particles; a solid or gel electrolyte layer provided on the power generation layer; and a counter electrode layer provided on the electrolyte layer; In the power generation layer, the density of the oxide semiconductor particles is dense on the glass substrate side and sparse in the stacking direction, a sealing material formed between the first solar cell and the second solar cell, from a side surface of the conductive oxide layer in the first solar cell to a side surface of the counter electrode layer, and from a side surface of the conductive oxide layer in the second solar cell to a side surface of the counter electrode layer, sealing the side surface of the electrolyte layer in the first solar cell and the side surface of the electrolyte layer in the second solar cell.

9. A glass substrate having a conductive oxide layer formed on one main surface thereof is prepared; oxide semiconductor particles are disposed on the conductive oxide layer and fired to form a power generation layer of the oxide semiconductor particles, and the glass substrate is warped so as to be convex toward the one main surface side, so that the density of the oxide semiconductor particles in the power generation layer is dense on the glass substrate side and sparse in the stacking direction; immersing electrolyte particles in the power generation layer to cause the power generation layer to contain the electrolyte particles and to form a solid or gel electrolyte layer on the power generation layer; forming a counter electrode layer on the electrolyte layer; a sealing material formed from the side surface of the glass substrate to the side surface of the counter electrode layer, thereby sealing the side surface of the electrolyte layer;

10. The method for manufacturing a solar cell according to claim 9 , wherein the temperature during the firing is 550° C. or higher and 650° C. or lower.

11. 11. The method for manufacturing a solar cell according to claim 9, wherein the dye is impregnated into the power generation layer by immersing the power generation layer in the dye after firing the power generation layer and before forming the counter electrode layer.

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