JP6289175B2 - Photoelectric conversion element and photoelectric conversion module - Google Patents

Description

  The present invention relates to a photoelectric conversion element and a photoelectric conversion module including the photoelectric conversion element.

  Conventionally, a silicon crystal solar cell is well known as a method for directly converting light energy into electric energy, and has already been used as an independent power source or a general power source in the field of weak power consumption. However, since a large amount of energy is required to produce amorphous silicon as well as silicon single crystals, it is necessary to continue power generation for a long period of nearly ten years in order to recover the energy spent to make batteries. .

  Under such circumstances, a dye-sensitized solar cell using a dye has been widely attracted attention. This dye-sensitized solar cell includes, for example, a semiconductor porous electrode carrying a sensitizing dye formed in a transparent conductive layer on a transparent substrate, a counter electrode, and a carrier transport layer sandwiched between the electrodes. It is mainly configured and is expected as a next-generation solar cell because of its simplicity of production method and low material cost.

  For example, Patent Document 1 proposes a wet solar cell that applies photoinduced electron transfer in a metal complex as a new type of solar cell. The wet solar cell described in Patent Document 1 is manufactured according to the following method. Electrodes are formed on the surfaces of the two glass substrates, the two glass substrates are arranged so that the formed electrodes are inside, and the porous semiconductor layer and the electrolyte are sandwiched between the two glass substrates. . The porous semiconductor layer is a semiconductor layer having an absorption spectrum in the visible light region by adsorbing a photosensitizing dye to a metal oxide such as titanium oxide. Such a wet solar cell is also called a dye-sensitized solar cell.

  In such a solar cell, when the photoelectrode is irradiated with visible light, the sensitizing dye on the semiconductor surface absorbs light, thereby exciting the electrons in the dye molecule and injecting the excited electrons into the photoelectrode. The Therefore, electrons are generated on this electrode side, and the electrons move to the counter electrode through the electric circuit. The electrons that have moved to the counter electrode are carried by holes or ions in the carrier transport layer and return to the photoelectrode. Such a process is repeated to extract electric energy, thereby realizing high energy conversion efficiency.

  For the purpose of obtaining high photoelectric conversion efficiency, for example, in Patent Document 2, a semiconductor layer composed of a plurality of layers having different average particle diameters is formed, and a distal layer disposed at a position farther from the substrate However, a dye-sensitized solar cell using a photoelectrode that covers at least a part of the side surface of the proximal layer disposed closer to the substrate has been proposed.

Japanese Patent Laid-Open No. 1-220380 JP 2006-49082 A

  However, the present inventors have found that high durability cannot be obtained by the conventional techniques as described above.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a photoelectric conversion element having high durability and a photoelectric conversion module including the photoelectric conversion element.

  The present invention is a photoelectric conversion element having, on a support substrate, at least a conductive layer, a porous semiconductor layer, a catalyst layer, a counter electrode conductive layer, and a carrier transport material filled in these voids, wherein the porous semiconductor layer is It is composed of a plurality of layers made of semiconductor fine particles to which a sensitizing dye is adsorbed, and the plurality of layers are at least a proximal layer located closest to the light receiving surface and a distal layer located farthest from the light receiving surface. The average particle size of the semiconductor fine particles constituting each of the plurality of layers is different from each other, and the average particle size of the semiconductor fine particles constituting the distal layer is the average particle size of the semiconductor fine particles constituting the proximal layer The distal layer covers all of the proximal layer, and the end of the distal layer is the end of the proximal layer when the porous semiconductor layer is projected horizontally relative to the support substrate. Protruding width d formed outside A photoelectric conversion element is 0.5mm or more.

  The average particle size of the semiconductor fine particles constituting the distal layer is not less than 100 nm and not more than 500 nm, and the minimum value of the particle size of the semiconductor fine particles constituting the distal layer constitutes another layer in the porous semiconductor layer It is preferable that it is larger than the maximum value of the particle diameter of the semiconductor fine particles.

The thickness of the distal layer is preferably 10 μm or more and 40 μm or less.
The intermediate layer further includes an intermediate layer between the proximal layer and the distal layer, and the intermediate layer has a horizontal projection area with respect to the support substrate equal to that of the proximal layer, and semiconductor fine particles having a particle diameter of 50 nm or more. It is preferable to contain 10% by weight or more and 50% by weight or less and that the thickness is 5 μm or more and 10 μm or less.

The porous semiconductor layer is preferably made of titanium oxide.
The thickness of the proximal layer is preferably 0.5 μm or more and 2 μm or less.

  Moreover, the present invention is a photoelectric conversion module in which two or more photoelectric conversion elements are connected in series, and at least one of the photoelectric conversion elements is the above-described photoelectric conversion element, and among the adjacent photoelectric conversion elements In the photoelectric conversion module, the counter electrode conductive layer of one photoelectric conversion element and the conductive layer of the other photoelectric conversion element are electrically connected.

  The present invention provides a photoelectric conversion element that has the above-described configuration, reduces a decrease in photoelectric conversion efficiency due to thermal stress, and has improved durability, and a photoelectric conversion module including the photoelectric conversion element. it can.

It is sectional drawing which shows one example of a structure of the photoelectric conversion element of this invention. It is sectional drawing which shows another example of a structure of the photoelectric conversion element of this invention. It is sectional drawing which shows one example of a structure of the photoelectric conversion module of this invention.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

  In the following embodiments, an example of the present invention is shown, and various embodiments can be implemented within the scope of the present invention.

[Configuration of photoelectric conversion element]
FIG. 1 is a cross-sectional view showing one example of the configuration of the photoelectric conversion element of the present invention. In the photoelectric conversion element shown in FIG. 1, a porous semiconductor layer 3 and a counter electrode 12 are sequentially provided on a conductive substrate 11, and a carrier transport material is filled between the porous semiconductor layer 3 and the counter electrode 12. Thus, the carrier transport layer 8 is formed. The conductive substrate 11 includes a support substrate 1 and a conductive layer 2 formed thereon. The porous semiconductor layer 3 is composed of a plurality of layers made of semiconductor fine particles to which a sensitizing dye is adsorbed. The plurality of layers are a proximal layer 3a located closest to the light receiving surface and a side farthest from the light receiving surface. And a distal layer 3b. The distal layer 3b covers all of the proximal layer 3a, and when the porous semiconductor layer 3 is projected horizontally with respect to the support substrate 1, the end of the distal layer 3b is more than the end of the proximal layer 3a. The protrusion width formed on the outside is represented by d. In the counter electrode 12, the counter electrode conductive layer 5 and the catalyst layer 4 are formed in order on the cover body 6, and the catalyst layer 4 faces the porous semiconductor layer 3. Further, the porous semiconductor layer 3 and the carrier transport layer 8 are sealed by a sealing portion 7.

  FIG. 2 is a cross-sectional view showing another example of the configuration of the photoelectric conversion element of the present invention. In the photoelectric conversion element shown in FIG. 2, the porous semiconductor layer 3 and the counter electrode 12 are sequentially provided on the conductive substrate 11, and a carrier transport material is filled between the porous semiconductor layer 3 and the counter electrode 12. Thus, the carrier transport layer 8 is formed. The conductive substrate 11 includes a support substrate 1 and a conductive layer 2 formed thereon. The porous semiconductor layer 3 is composed of a plurality of layers made of semiconductor fine particles to which a sensitizing dye is adsorbed. The plurality of layers are a proximal layer 3a located closest to the light receiving surface and a side farthest from the light receiving surface. And a middle layer 3c located between the proximal layer 3a and the distal layer 3b. The intermediate layer 3c has a horizontal projected area with respect to the support substrate 1 equal to the proximal layer 3a, the distal layer 3b covers all of the proximal layer 3a and the intermediate layer 3c, and the porous semiconductor layer 3 is attached to the support substrate 1. On the other hand, when projected horizontally, the distance between the end of the distal layer 3b and the ends of the proximal layer 3a and the intermediate layer 3c is the protruding width d. In the counter electrode 12, the counter electrode conductive layer 5 and the catalyst layer 4 are formed in order on the cover body 6, and the catalyst layer 4 faces the porous semiconductor layer 3. Further, the porous semiconductor layer 3 and the carrier transport layer 8 are sealed by a sealing portion 7.

<Support substrate>
The support substrate 1 constitutes at least a part of the light receiving surface of the photoelectric conversion element shown in FIGS. 1 and 2. Therefore, it is preferable that the part used as the light-receiving surface of a photoelectric conversion element among the support substrates 1 consists of a material which has a light transmittance. The light-transmitting material may be any material that substantially transmits at least light having a wavelength effective for the sensitizing dye described later, and is necessarily transparent to light in all wavelength regions. There is no need.

  The support substrate 1 may be, for example, a glass substrate made of soda lime float glass, fused silica glass, crystal quartz glass, or the like, or may be a heat resistant resin substrate such as a flexible film. Examples of the flexible film include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PA), polyether imide (PEI), phenoxy resin or A film made of polytetrafluoroethylene (PTFE) or the like can be used.

  When forming another layer on the support substrate with heating, for example, when forming a conductive layer on the support substrate with heating at about 250 ° C., a film made of polytetrafluoroethylene is used as the support substrate. It is preferable. Since the film made of polytetrafluoroethylene has a heat resistance of 250 ° C. or higher, thermal damage to the support substrate can be suppressed even if the support substrate is heated to about 250 ° C.

  The thickness of the support substrate 1 is not particularly limited as long as it can give an appropriate strength to the photoelectric conversion element, but is preferably 0.5 mm or more and 10 mm or less. If the thickness of the support substrate 1 is 0.5 mm or more, the support substrate 1 tends to exhibit a function as a support substrate. If the thickness of the support substrate 1 is 10 mm or less, a decrease in the amount of light transmitted through the support substrate 1 is prevented, so that a decrease in photoelectric conversion efficiency of the photoelectric conversion element tends to be prevented.

  The support substrate 1 can be used when the completed photoelectric conversion element is attached to another structure. In other words, the peripheral portion of the support substrate made of a glass substrate or the like can be easily attached to another support substrate using a metal processed component and a screw.

<Conductive layer>
The conductive layer 2 constitutes at least a part of the light receiving surface of the photoelectric conversion element shown in FIGS. 1 and 2. Therefore, it is preferable that the part used as the light-receiving surface of a photoelectric conversion element among the conductive layers 2 consists of a material which has a light transmittance and electroconductivity. However, like the support substrate, the conductive layer may be a material that substantially transmits light having a wavelength having effective sensitivity to at least a sensitizing dye described later, and is not necessarily transparent to light in all wavelength regions. It is not necessary to have sex.

As the conductive layer 2, for example, a film made of indium tin composite oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), or the like can be used.

  The thickness of the conductive layer 2 is not particularly limited, but is preferably 0.1 μm or more and 5 μm or less. When the thickness of the conductive layer is 0.1 μm or more, the resistance of the conductive layer is reduced, so that the amount of current that can be extracted outside the photoelectric conversion element increases. Therefore, the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved. If the thickness of the conductive layer is 5 μm or less, a decrease in the amount of light transmitted through the conductive layer is prevented, so that the photoelectric conversion efficiency of the photoelectric conversion element tends to be maintained.

  The surface resistivity (sheet resistance) of the conductive layer 2 is not particularly limited, but is preferably 40 Ω / sq or less. If the surface resistivity of the conductive layer is 40 Ω / sq or less, the amount of current that can be taken out of the photoelectric conversion element increases, and thus the photoelectric conversion efficiency of the photoelectric conversion element tends to be improved.

  The conductive layer 2 may be provided with a metal wire. When a metal wire is provided in the conductive layer, the resistance of the conductive layer tends to be low. As the metal wire, for example, a metal wire containing at least one metal selected from platinum, gold, silver, copper, aluminum, nickel, and titanium can be used. Note that the thickness of the metal wire is preferably 0.1 mm or more and 4 mm or less, for example, from the viewpoint of avoiding a decrease in the amount of incident light due to the metal wire provided in the conductive layer.

<Porous semiconductor layer>
The porous semiconductor layer 3 is composed of a plurality of layers made of semiconductor fine particles to which a sensitizing dye is adsorbed.

The semiconductor fine particles constituting the porous semiconductor layer 3 can be any of those generally used for photoelectric conversion materials, such as titanium oxide, zinc oxide, tin oxide, niobium oxide, zirconium oxide. , Cerium oxide, tungsten oxide, silicon oxide, aluminum oxide, nickel oxide, barium titanate, strontium titanate, cadmium sulfide, CuAlO ₂ , SrCu ₂ O _{2, and the} like. From the viewpoint of stability and safety, titanium oxide is preferred. Examples of such titanium oxides include various narrowly defined titanium oxides such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide, and hydrous titanium oxide. By using titanium oxide as the material for the porous semiconductor layer, a photoelectric conversion element having high heat resistance and high photoelectric conversion efficiency can be obtained.

  Each layer forming the porous semiconductor layer 3 is not particularly limited, but is preferably in the form of a porous film. Thereby, since the light-receiving area of a porous semiconductor layer increases, it exists in the tendency for the photoelectric conversion efficiency of a photoelectric conversion element to improve. In addition, thinning of the photoelectric conversion element tends to be promoted.

  The porosity of the porous semiconductor layer 3 (ratio of the volume of voids formed in the porous semiconductor layer to the total volume of the porous semiconductor layer) is preferably 20% or more, and is 40% or more and 80% or less. More preferably. When the porosity of the porous semiconductor layer is 20% or more, the carrier transport material tends to diffuse sufficiently inside the porous semiconductor layer. Note that the porosity of the porous semiconductor layer is obtained by calculation from the thickness of the porous semiconductor layer, the mass of the porous semiconductor layer, and the density of the semiconductor material.

  The plurality of layers constituting the porous semiconductor layer 3 include at least a proximal layer 3a located on the side closest to the light receiving surface and a distal layer 3b located on the side farthest from the light receiving surface. The average particle diameters of the semiconductor fine particles constituting each of the plurality of layers are different from each other, and the average particle diameter of the semiconductor fine particles constituting the distal layer is larger than the average particle diameter of the semiconductor fine particles constituting the proximal layer. The distal layer covers all of the proximal layer, and when the porous semiconductor layer is projected horizontally with respect to the support substrate, the protruding width d at which the end of the distal layer is formed outside the end of the proximal layer Is 0.5 mm or more. Thereby, heat resistance is improved, and further, a decrease in photoelectric conversion efficiency due to thermal stress is reduced, and durability of the photoelectric conversion element is improved. This is because when the distal layer becomes a block layer, a leak source generated when a thermal load is applied may adhere to the proximal layer having a small average particle diameter of the contained semiconductor particles, that is, a large specific surface area. This is thought to be due to the reduction.

The semiconductor fine particles forming the proximal layer 3a preferably have a large specific surface area from the viewpoint of light absorption ability, and more preferably 10 m ² / g or more and 200 m ² / g or less. In addition, the specific surface area of a porous semiconductor layer is calculated | required based on the BET method (JISZ8830: 2001) etc. which are gas adsorption methods, for example.

  The average particle diameter of the semiconductor fine particles constituting the proximal layer 3a is preferably 15 nm or more and 25 nm or less. When the average particle size of the semiconductor fine particles constituting the proximal layer is smaller than 15 nm, the porosity in the proximal layer is lowered, so that the diffusion of ions in the carrier transport layer tends to be inhibited. Since the specific surface area decreases, the light absorption ability tends to decrease. The particle size of the semiconductor fine particles is measured using a scanning electron microscope (SEM). Based on a plurality of image samples, the particle size of each particle is measured together with the minimum particle size and the maximum particle size of the semiconductor fine particles. The average particle diameter is obtained.

  The thickness of the proximal layer 3a is preferably 0.5 μm or more and 2 μm or less. Thus, the small thickness of the proximal layer composed of semiconductor fine particles with a large specific surface area can reduce the amount of leakage sources attached to the proximal layer when heat stress is applied. is there.

  The average particle diameter of the semiconductor fine particles constituting the distal layer 3b is not less than 100 nm and not more than 500 nm, and the minimum value of the particle diameter of the semiconductor fine particles constituting the distal layer is the other layer in the porous semiconductor layer 3 It is larger than the maximum value of the particle size of the semiconductor fine particles constituting. Thereby, the heat resistance of a photoelectric conversion element can further be improved.

  The thickness of the distal layer 3b is preferably 10 μm or more and 40 μm or less, and more preferably 12 μm or more and 20 μm or less. If it is 10 μm or more, it tends to block adsorption to the proximal layer and intermediate layer of the leak source that occurs when a heat load is applied, and if it is 40 μm or less, it inhibits the movement of ions in the carrier transport layer. There is a tendency not to.

  Further, the proximal layer and the distal layer may be adjacent to each other or may not be adjacent to each other. As shown in FIG. 2, when three layers are formed on the conductive substrate 11, the layer closest to the conductive substrate is the proximal layer 3a, the layer farthest from the substrate is the distal layer 3b, A layer positioned between the layer and the distal layer is referred to as an intermediate layer 3c. The intermediate layer may be a single layer or a multilayer.

  The intermediate layer 3c is composed of semiconductor fine particles having an average particle size of 15 nm or more and 25 nm or less and semiconductor fine particles having a particle size of 50 nm or more, and contains 10% by weight or more and 50% by weight or less of semiconductor fine particles having a particle size of 50 nm or more. The content is preferably 30% by weight or more and 50% by weight or less.

  The thickness of the intermediate layer 3c is preferably 5 μm or more and 10 μm or less. When the intermediate layer contains semiconductor fine particles having a particle diameter of 50 nm or more and 10 wt% or more and 50 wt% or less and has a thickness of 5 μm or more and 10 μm or less, it can absorb more light and increase durability. A highly efficient photoelectric conversion element can be obtained.

  In addition, the total thickness of the porous semiconductor layer is preferably 45 μm or less from the viewpoint of light transmittance and photoelectric conversion efficiency.

  When the porous semiconductor layer is composed of three or more layers and includes an intermediate layer, the horizontal projected area of the proximal layer and the intermediate layer with respect to the support substrate is equal, and the end of the distal layer is the proximal layer and the intermediate layer. The protrusion width d formed on the outer side of the end portion of each is 0.5 mm or more. Thereby, the durability of the photoelectric conversion element can be further improved. This is because when the distal layer becomes a block layer, a leak source generated when a thermal load is applied adheres to the proximal layer and the intermediate layer in which the average particle size of the contained semiconductor particles is small, that is, the specific surface area is large. This is considered to be due to the reduction.

<Sensitizing dye>
A sensitizing dye is preferably adsorbed on the porous semiconductor layer 3. As the sensitizing dye, those having absorption in various visible light regions and / or infrared light regions can be used. Examples of organic dyes include azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, and perylene dyes. Examples thereof include dyes, indigo dyes, and naphthalocyanine dyes. In the case of a metal complex dye, Cu, Ni, Fe, Co, V, Sn, Si, Ti, Ge, Cr, Zn, Ru, Mg, Al, Pb, Mn, In, Mo, Y, Zr, Nb, Sb, La, W, Pt, Ta, Ir, Pd, Os, Ga, Tb, Eu, Rb, Bi, Se, As, Sc, Ag, Cd, Hf, Re, Au, Ac, Tc, Te, A metal such as Rh is used, and a phthalocyanine dye or a ruthenium metal complex dye is preferably used.

  In order for the sensitizing dye to be firmly adsorbed to the porous semiconductor layer 3, the carboxylic acid group, carboxylic acid anhydride group, alkoxy group, hydroxyl group, hydroxyalkyl group, sulfonic acid group, ester group, mercapto group are included in the molecule. In addition, those having an interlock group such as a phosphonyl group are preferred, and those having a carboxylic acid group or a carboxylic anhydride group are more preferred.

  Before adsorbing the sensitizing dye on the surface of the porous semiconductor layer 3, a treatment for activating the surface of the porous semiconductor layer may be performed as necessary. In the step of adsorbing the sensitizing dye to the porous semiconductor layer, the porous semiconductor layer is immersed in a liquid containing the sensitizing dye, and the sensitizing dye is adsorbed on the surface of the porous semiconductor layer.

The liquid is not particularly limited as long as it can dissolve the sensitizing dye to be used. Specifically, an organic solvent such as alcohol, toluene, acetonitrile, THF, chloroform, dimethylformamide, or the like can be used. Usually, it is preferable to use a purified solvent. The concentration of the sensitizing dye in the solvent can be adjusted according to the dye used, the type of solvent, the conditions for the dye adsorption step, and the like. The concentration of the sensitizing dye is preferably 1 × 10 ⁻⁵ mol / L or more.

  In the step of immersing the porous semiconductor layer in the liquid containing the sensitizing dye, the temperature, pressure, and immersion time can be changed as necessary. Immersion may be performed once or multiple times. Moreover, you may dry suitably after the process of immersion. The dye adsorbed on the semiconductor by the above-described method functions as a photosensitizer that sends electrons to the semiconductor by light energy. Generally, a sensitizing dye is fixed to a semiconductor via an interlock group. The interlock group provides an electrical bond that facilitates the transfer of electrons between the excited state dye and the conduction band of the semiconductor.

<Catalyst layer>
As a material constituting the catalyst layer 4, for example, it is preferable to use at least one of platinum and carbon. As the platinum, it is preferable to use a material in which a film is formed on a support substrate coated with a conductive layer by a method such as sputtering, thermal decomposition of chloroplatinic acid, or electrodeposition. As the carbon, for example, at least one of carbon black, graphite, glass carbon, amorphous carbon, hard carbon, soft carbon, carbon whisker, carbon nanotube, and fullerene is preferably used.

  The thickness of the catalyst layer 4 is not particularly limited, but when platinum is used, it is preferably 1 nm or more and 300 nm or less, and when carbon is used, it is preferably 1 nm or more and 50 μm or less.

<Counter electrode conductive layer>
The counter electrode conductive layer 5 collects electrons and also functions as an electrode for electrically connecting adjacent photoelectric conversion elements when manufacturing photoelectric conversion modules by connecting the photoelectric conversion elements in series. Moreover, when light injects from the counter electrode 12 side, the counter electrode conductive layer 5 needs to have translucency.

Examples of materials constituting the counter electrode conductive layer 5 include N-type or P-type elemental semiconductors such as silicon and germanium; compound semiconductors such as GaAs, InP, ZnSe, and CsS; gold, platinum, silver, copper, and aluminum. Metals such as: high melting point metals such as titanium, tantalum, and tungsten; transparent conductive materials such as ITO, SnO ₂ , CuI, and ZnO.

  The thickness of the counter electrode conductive layer 5 is preferably 0.1 μm or more and 5 μm or less. If the thickness of the counter electrode conductive layer 5 is less than 0.1 μm, the resistance of the counter electrode conductive layer 5 tends to increase, and if it exceeds 5 μm, the movement of the carrier transport material tends to be hindered.

<Cover body>
The cover body 6 prevents the carrier transport material from volatilizing and prevents water and the like from entering the photoelectric conversion element.

  The material which comprises the cover body 6 will not be specifically limited if it is a material which can generally be used for a photoelectric conversion element, and can exhibit the effect of this invention. Examples of such materials include soda lime glass, lead glass, borosilicate glass, fused silica glass, and crystal quartz glass. Among these, it is preferable to use soda lime float glass as a material constituting the cover body 6.

<Carrier transport layer>
Any material can be used as the carrier transport layer 8 as long as it can transport electrons, holes, and ions. As a suitable material for the carrier transport material, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, a molten salt gel electrolyte, or the like can be used.

  The liquid electrolyte is preferably a liquid containing redox species, and is not particularly limited as long as it can be used in a battery or a solar battery. Examples of the liquid electrolyte include those comprising a redox species and a solvent capable of dissolving the redox species, those comprising a redox species and a molten salt capable of dissolving the redox species, or the redox species and the above solvent. And the above-mentioned molten salt.

As the redox species, for example, at least one selected from the group consisting of I− / I ³⁻ , Br ²⁻ / Br ³⁻ , Fe ²⁺ / Fe ^3+, and quinone / hydroquinone can be used. Specifically, as the redox species, a combination of metal iodide and iodine (I ₂ ), a combination of a salt composed of iodide ions and iodine (I ₂ ), or a metal bromide and bromine (Br ₂ ). It is preferable to use a combination thereof. Photoelectric conversion elements using these redox species exhibit better IV curves than, for example, photoelectric conversion elements using cobalt complexes or ferrocene as the redox species.

As the metal iodide, for example, at least one of lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), and calcium iodide (CaI ₂ ) can be used.

  As the salt composed of iodide ions, for example, at least one of an ammonium salt and an imidazolium salt can be used. As the ammonium salt, for example, at least one of tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), tetrabutylammonium iodide (TBAI), and tetrahexylammonium iodide (THAI) is used. Can do. Examples of the imidazolium salt include dimethylpropylimidazole iodide (DMPII), methylpropylimidazole iodide (MPII), ethylmethylimidazole iodide (EMII), ethylimidazole iodide (EII), and hexylmethylimidazole iodide (HMII). ) Can be used.

  As the metal bromide, for example, at least one of lithium bromide (LiBr), sodium bromide (NaBr), potassium bromide (KBr), and calcium bromide (CaBr2) can be used.

  As the redox species, a combination of several types such as a combination of a metal iodide and iodide ion salt and iodine can be used.

  Examples of the solvent capable of dissolving the redox species include carbonate compounds such as propylene carbonate, nitrile compounds such as acetonitrile, alcohols such as ethanol, water, aprotic polar substances, and the like. As the solvent capable of dissolving the redox species, these may be used alone or in admixture of two or more. Among these, it is preferable to use a carbonate compound or a nitrile compound.

  The solid electrolyte is preferably a conductive material that can transport electrons, holes, or ions, and can preferably be used as an electrolyte of a photoelectric conversion element and has no fluidity. Specifically, as the solid electrolyte, a hole transport material such as polycarbazole, an electron transport material such as tetranitrofluororenone, a conductive polymer such as polyroll, a polymer electrolyte obtained by solidifying a liquid electrolyte with a polymer compound, A p-type semiconductor such as copper iodide or copper thiocyanate, or an electrolyte obtained by solidifying a liquid electrolyte containing a molten salt with fine particles can be used.

  The gel electrolyte is preferably composed of an electrolyte and a gelling agent. The mixing ratio of the electrolyte and the gelling agent is preferably adjusted as appropriate. As the electrolyte, for example, the liquid electrolyte or the solid electrolyte can be used.

  Examples of gelling agents include polymers such as crosslinked polyacrylic resin derivatives, crosslinked polyacrylonitrile derivatives, polyalkylene oxide derivatives, silicone resins, or polymers having a nitrogen-containing heterocyclic quaternary compound salt structure in the side chain. A gelling agent or the like can be used.

  The molten salt gel electrolyte is preferably composed of the gel electrolyte and a room temperature molten salt. As the room temperature molten salt, for example, quaternary ammonium salts of nitrogen-containing heterocyclic compounds such as pyridinium salts or imidazolium salts can be used.

  The carrier transport layer 8 may contain the following additives as required. As the additive, a nitrogen-containing aromatic compound such as t-butylpyridine (TBP) or an ionic organic compound such as guanidine thiocyanate may be used. As the additive, both of the aromatic compound containing nitrogen and an ionic organic compound such as guanidine thiocyanate can be used.

  The concentration of the redox species in the carrier transport material is preferably selected as appropriate depending on the type of solvent and electrolyte that can dissolve the redox species, but it is preferably 0.01 mol / L or more and 1.5 mol / L or less. Preferably, it is 0.1 mol / L or more and 0.7 mol / L or less. If the concentration of the redox species in the carrier transport material is within the above range, the redox species in the carrier transport layer 8 tend to be efficiently transported.

<Sealing part>
The sealing part 7 prevents volatilization of the carrier transport material and prevents water and the like from entering the photoelectric conversion element. In addition, the sealing portion 7 absorbs stress (impact) that acts on the support substrate 1 and absorbs bending that acts on the support substrate 1 when the photoelectric conversion element is used for a long period of time.

  For example, the sealing portion 7 may be a single layer including at least one of a silicone resin, an epoxy resin, a polyisobutylene resin, a hot melt resin, and a glass frit. It may be a laminated body constructed.

  In the case where a hardly volatile solvent such as a nitrile solvent or a carbonate solvent is used as a solvent for the carrier transport material, the sealing portion 7 is made of a silicone resin, a hot melt resin (for example, an ionomer resin), or a polyisobutylene resin. And at least one of glass frit. Thereby, it exists in the tendency for the corrosion of the sealing part 7 with respect to carrier transport material to be suppressed.

[Production Method of Photoelectric Conversion Element]
<Formation of conductive substrate>
First, a conductive substrate 11 in which the conductive layer 2 is formed on the support substrate 1 is prepared. For example, a commercially available conductive substrate may be prepared, or the conductive layer 2 may be formed on the support substrate 1 by a method such as sputtering or thermal CVD.

<Formation of porous semiconductor layer>
The porous semiconductor layer 3 is formed on the conductive substrate 11. The porous semiconductor layer can be formed, for example, by a method of applying a suspension containing semiconductor fine particles on a conductive substrate, and drying and / or firing. Hereinafter, this method will be described in detail.

  First, a proximal layer is formed on a conductive substrate. Specifically, first, the semiconductor fine particles used for forming the proximal layer are suspended in an appropriate solvent. Examples of such a solvent include glyme solvents such as ethylene glycol monoethyl ether, alcohols such as isopropyl alcohol, alcohol-based mixed solvents such as isopropyl alcohol / toluene, and water. Application of the semiconductor fine particle suspension for forming the proximal layer to the conductive substrate includes known methods such as a doctor blade method, a squeegee method, a spin coating method, and a screen printing method. Thereafter, the coating solution is dried and baked. The temperature, time, atmosphere, etc. necessary for drying and firing can be appropriately adjusted according to the type of conductive substrate and semiconductor fine particles used, for example, 50 ° C. or higher in the air or in an inert gas atmosphere. It can be performed at a temperature of 800 ° C. or lower for 10 seconds to 12 hours. Drying and firing may be performed only once at a single temperature, or may be performed twice or more by changing the temperature.

  Next, an intermediate layer is formed by a method similar to the method for forming the proximal layer. The horizontal projected area of the intermediate layer with respect to the support substrate is equal to the horizontal projected area of the proximal layer.

  Subsequently, a distal layer covering all of the proximal and intermediate layers is formed. Specifically, first, a kapton tape or a mending tape is applied to the outside of the periphery of the proximal layer and the intermediate layer formed in the above-mentioned process at a distance from the proximal layer and the intermediate layer. Create the outer frame. Next, semiconductor fine particle suspensions having different average particle diameters are dropped on the gap between the tape and the proximal layer and the intermediate layer, and the entire proximal layer and intermediate layer, and the suspension is applied by the doctor blade method. When the screen printing method is used, a screen mask larger than the screen mask already used for forming the proximal layer and the intermediate layer may be prepared and applied. Then, drying and baking are performed similarly to formation of a proximal layer. When the distal layer formed by the above process is projected horizontally with respect to the support substrate, the protrusion width d formed at the end portion outside the end portions of the proximal layer and the intermediate layer is 0.5 mm or more. It is preferable.

<Adsorption of sensitizing dye>
A porous semiconductor layer is immersed in a liquid containing a sensitizing dye, and the sensitizing dye is adsorbed on the surface of the porous semiconductor layer. Before the sensitizing dye is adsorbed on the surface of the porous semiconductor layer, a treatment for activating the surface of the porous semiconductor layer may be performed as necessary. In the step of immersing the porous semiconductor layer in the liquid containing the sensitizing dye, the temperature, pressure, and immersion time can be changed as necessary. Immersion may be performed once or multiple times. Moreover, you may dry suitably after the process of immersion.

<Formation of counter electrode>
The counter electrode 12 is manufactured. For example, the counter electrode conductive layer 5 is preferably formed on the cover body 6 by a method such as sputtering or thermal CVD. When the catalyst layer 4 made of platinum is formed, the catalyst layer 4 may be formed on the counter electrode conductive layer 5 by a PVD method such as vapor deposition or sputtering, or thermal decomposition or electrodeposition of chloroplatinic acid. Thus, the catalyst layer 4 may be formed on the counter electrode conductive layer 5. When the catalyst layer 4 made of a carbon material such as carbon black, ketjen black, carbon nanotube, or fullerene is formed, the carbon dispersed in an arbitrary solvent and paste-like is formed on the counter electrode conductive layer 5 by a screen printing method or the like. It is preferable to apply to.

<Filling of carrier transport material>
Fill with carrier transport material. For example, the sealing portion 7 is disposed so as to surround the periphery of the porous semiconductor layer formed on the conductive substrate 11. The conductive substrate 11 and the counter electrode 12 are arranged so that the porous semiconductor layer formed on the conductive substrate 11 and the catalyst layer 4 of the counter electrode 12 face each other, and the conductive substrate 11 and the counter electrode 12 are connected to the sealing portion 7. To fix. Thereafter, a carrier transport material is injected into a region surrounded by the sealing portion 7 from a hole formed in advance in the conductive substrate 11 or the counter electrode 12, and then the hole is closed. Thereby, a photoelectric conversion element is manufactured.

[Photoelectric conversion module]
FIG. 3 is a cross-sectional view showing an example of the configuration of the photoelectric conversion module of the present invention. In the photoelectric conversion module shown in FIG. 3, two or more photoelectric conversion elements of this embodiment are connected in series. Among the adjacent photoelectric conversion elements, the counter conductive layer 5 of one photoelectric conversion element and the conductive layer 2 of the other photoelectric conversion element are electrically connected. Thus, since the photoelectric conversion module shown in FIG. 3 includes the photoelectric conversion element of this embodiment, a photoelectric conversion module having high durability can be provided.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In the following, unless otherwise specified, the thickness of each layer was measured using a step gauge (manufactured by Tokyo Seimitsu Co., Ltd., model number: E-VS-S28A).

<Example 1>
First, a conductive substrate 11 (a glass plate with SnO ₂ film manufactured by Nippon Sheet Glass Co., Ltd.) having a width of 30 mm, a length of 30 mm, and a thickness of 1 mm was prepared. In the conductive substrate 11, a conductive layer 2 made of tin oxide (FTO) doped with fluorine is formed on a support substrate 1 made of glass.

  Next, a commercially available titanium oxide paste having an average particle diameter of 20 nm (using a screen printing machine having a pattern of width 5 mm × length 5 mm and a screen printing machine (manufactured by Neurong Seimitsu Kogyo Co., Ltd., model number: LS-150)) (Solaronix, trade name: T / SP) was applied on the conductive layer 2 and leveled at room temperature for 1 hour. The obtained coating film was dried in an oven set at 80 ° C. for 20 minutes, and then baked in air for 60 minutes using a baking furnace (model number: KDF P-100, manufactured by Denken Co., Ltd.) set at 500 ° C. Thereby, the proximal layer 3a of the porous semiconductor layer having a thickness of about 2 μm was obtained.

  Furthermore, using a screen plate having a pattern of width 6 mm × length 6 mm and a screen printing machine, a commercially available titanium oxide paste having an average particle diameter of 400 nm (product name: PST-400C, manufactured by JGC Catalysts & Chemicals) is porous. The porous semiconductor layer distal layer 3b having a thickness of about 10 μm and a protruding width d of 0.5 mm was formed by applying the semiconductor layer on the proximal layer and repeating the same operation as the proximal layer. .

  Next, the conductive substrate 11 on which the porous semiconductor layer was formed was immersed in a liquid containing a sensitizing dye prepared in advance at room temperature for 24 hours. Thereafter, it was washed with ethanol and dried at about 60 ° C. for about 5 minutes. Thereby, the sensitizing dye was adsorbed on the porous semiconductor layer.

Next, another glass plate with SnO ₂ film manufactured by Nippon Sheet Glass Co., Ltd. was prepared separately from the conductive substrate 11. A platinum film (catalyst layer 4) having a thickness of about 7 nm was formed on the SnO ₂ film by sputtering. Thereby, the counter electrode 12 was formed.

  Next, the conductive substrate 11 and the counter electrode 12 are formed using a heat-sealing film (DuPont, trade name: Binnel (registered trademark)) cut into a shape surrounding the periphery of the porous semiconductor layer on which the dye is adsorbed. And pasted together. The conductive substrate 11 and the counter electrode 12 were pressure-bonded by heating in an oven set at about 130 ° C. for 10 minutes.

  Next, a carrier transport material was injected from a hole formed in advance in the counter electrode 12, and then the hole was sealed using a heat-sealing film (trade name: Binnel (registered trademark) manufactured by DuPont). Thus, the carrier transport material was filled between the porous semiconductor layer 3 on which the dye was adsorbed and the catalyst layer 4, and the photoelectric conversion element of Example 1 was manufactured.

The carrier transport material was prepared as shown below. Methylpropylimidazole iodide (Shikoku Kasei Kogyo Co., Ltd., redox species) is dissolved in methoxypropionitrile as a solvent so that the concentration becomes 0.8 mol / L, so that the concentration becomes 0.15 mol / L. I ₂ (manufactured by Kishida Chemical Co., redox species) was dissolved. Further, methylpropylimidazole iodide was dissolved in the solvent so that the concentration became 0.5 mol / L, and guanidine thiocyanate (additive) was dissolved so that the concentration became 0.1 mol / L.

<Example 2>
The distal layer is formed by using a screen plate having a pattern of width 7 mm × length 7 mm and a screen printing machine, and the projecting width d is 1.0 mm. 2 photoelectric conversion elements were produced.

<Example 3>
The distal layer is formed using a screen plate having a pattern of width 8 mm × length 8 mm and a screen printing machine, and the example is the same as in Example 1 except that the protrusion width d is 1.5 mm. 3 photoelectric conversion elements were produced.

<Example 4>
A photoelectric conversion element of Example 4 was manufactured in the same manner as Example 1 except that a paste having an average particle diameter of 110 nm was prepared to form a distal layer.

<Example 5>
A photoelectric conversion element of Example 5 was produced in the same manner as Example 1 except that a paste having an average particle diameter of 250 nm was prepared to form a distal layer.

<Example 6>
A photoelectric conversion element of Example 6 was produced in the same manner as Example 1 except that the distal layer was formed to have a thickness of 24 μm.

<Example 7>
A photoelectric conversion element of Example 7 was produced in the same manner as in Example 1 except that the distal layer was formed to have a thickness of 42 μm.

<Example 8>
A photoelectric conversion element of Example 8 was produced in the same manner as Example 1 except that an intermediate layer was formed between the proximal layer and the distal layer. Specifically, using a screen plate having a pattern of width 5 mm × length 5 mm and a screen printing machine, a commercially available titanium oxide paste having an average particle diameter of 20 nm (trade name: T / SP, manufactured by Solaronix) After forming a proximal layer in the same manner as in Example 1, a titanium oxide paste composed of titanium oxide particles having an average particle diameter of 20 nm and titanium oxide particles having a particle diameter of 50 nm was applied onto the proximal layer, and Leveling was performed for 1 hour. Here, in the titanium oxide particles contained in the used titanium oxide paste, the proportion of titanium oxide particles having a particle diameter of 50 nm was 10% by weight. The obtained coating film was dried in an oven set at 80 ° C. for 20 minutes, and then baked in air using a baking furnace set at 500 ° C. for 60 minutes. Thereby, an intermediate layer of a porous semiconductor layer having a thickness of about 5 μm was obtained.

<Example 9>
A photoelectric conversion element of Example 9 was produced in the same manner as in Example 8, except that the intermediate layer was formed to have a thickness of 7 μm.

<Example 10>
A photoelectric conversion element of Example 10 was produced in the same manner as Example 8, except that the intermediate layer was formed to have a thickness of 10 μm.

<Example 11>
[Production of photoelectric conversion module]
First, a conductive substrate 11 (manufactured by Nippon Sheet Glass Co., Ltd., trade name: glass with SnO ₂ film: length 60 mm × width 37 mm) having a conductive layer 2 formed on the surface is prepared, and the SnO ₂ film on the surface of the conductive substrate 11 is prepared. The conductive layer 2 was cut by forming a scribe line 13 parallel to the vertical direction by laser scribing. A total of three scribe lines 13 were formed on the glass substrate as the support substrate 1. The formed scribe line 13 has a width of 30 μm.

  Next, the proximal layer of the porous semiconductor layer was formed according to Example 1. Three proximal layers were formed on a glass substrate with a thickness of 2 μm, a width of 4 mm, and a length of 40 mm. Furthermore, a commercially available titanium oxide paste (manufactured by JGC Catalysts & Chemicals, trade name: PST-400C) having an average particle size of 400 nm is made porous using a screen plate having a pattern of width 5 mm × length 50 mm and a screen printing machine. The distal layer of the porous semiconductor layer having a thickness of about 10 μm and a protruding width d of 0.5 mm was formed by applying the same to the proximal layer of the semiconductor layer and repeating the same operation as the proximal layer.

  A paste containing zirconia particles having an average particle size of 50 nm is applied onto the porous semiconductor layer 3 using a screen printer, and then baked at 500 ° C. for 60 minutes, from the surface of the porous semiconductor layer to a flat portion. A porous insulating layer 9 having a distance (thickness) of 7 μm was formed.

  Next, using a mask on which a predetermined pattern is formed and a vapor deposition apparatus (model number: ei-5, manufactured by ULVAC, Inc.), a platinum film is formed on the porous insulating layer 9 at a vapor deposition rate of 4 Å / s. Layer 4 was obtained. The size, shape, and position in the width direction of the catalyst layer were the same as the porous semiconductor layer.

  Further, a 400 nm thick titanium film was formed on the catalyst layer 4 at a deposition rate of 5 Å / s using a mask having a predetermined pattern and a vapor deposition apparatus (model number: ei-5, manufactured by ULVAC). The counter electrode conductive layer 5 was obtained.

  The obtained laminate was immersed in the dye adsorption solution used in Example 1 at room temperature for 70 hours to adsorb the dye to the porous semiconductor layer.

  Next, an ultraviolet curable resin (3035B manufactured by ThreeBond Co., Ltd.) was applied between the laminates and around the cell using a dispenser (ULTRASAVER manufactured by EFD Co.), and a glass substrate having a length of 60 mm × width of 30 mm was bonded as a cover body The sealing portion 7 was formed by curing the photosensitive resin by irradiating ultraviolet rays using an ultraviolet lamp (NOVACURE manufactured by EFD).

  Thereafter, the same carrier transport material as in Example 1 is injected from a carrier transport material injection hole provided in advance on the glass substrate constituting the cover body 6, and further an ultraviolet curable resin is applied, and ultraviolet rays are applied in the same manner as the sealing material. A photoelectric conversion module in which a hole is sealed by irradiation and a counter electrode conductive layer of one photoelectric conversion element and a conductive layer of the other photoelectric conversion element are electrically connected in series among adjacent photoelectric conversion elements Was made.

  An Ag paste (manufactured by Fujikura Kasei Co., Ltd., trade name: Dotite) was applied to the obtained photoelectric conversion module as the collecting electrode portion 14.

<Comparative Example 1>
A comparative example was made in the same manner as in Example 1 except that when forming the distal layer, a screen plate having a pattern of width 5 mm × length 5 mm and a screen printing machine were used, and the protruding width d was set to 0 mm. 1 photoelectric conversion element was manufactured.

<Comparative example 2>
A photoelectric conversion element of Comparative Example 2 was produced in the same manner as in Example 1 except that the distal layer was formed using a paste having an average particle diameter of 20 nm.

<Comparative Example 3>
A photoelectric conversion element of Comparative Example 3 was produced in the same manner as in Example 1 except that the distal layer was formed to have a thickness of 6 μm.

<Durability test>
In accordance with the method described in JIS C8938, the photoelectric conversion elements and the photoelectric conversion modules obtained in Examples 1 to 11 and Comparative Examples 1 to 3 were allowed to stand at a temperature of 85 ° C. for 1000 hours. Heat stress was applied. And the photoelectric conversion efficiency immediately after manufacture of a photoelectric conversion element and a photoelectric conversion module, and the photoelectric conversion efficiency after giving a thermal stress were measured.

The photoelectric conversion efficiency was measured according to the following method. For the photoelectric conversion elements obtained in Examples 1 to 10 and Comparative Examples 1 to 3, an Ag paste (manufactured by Fujikura Kasei Co., Ltd., trade name: Dotite) was applied as a collecting electrode part by a known method. Next, a black mask having an opening area of 0.22 cm ² was placed on the light receiving surfaces of the photoelectric conversion elements of Examples 1 to 10 and Comparative Examples 1 to 3. In addition, a black mask having an opening area of 13 cm ² was placed on the light receiving surface of the photoelectric conversion module of Example 11. Each photoelectric conversion element was irradiated with light having an intensity of 1 kW / m ² (AM1.5 solar simulator) to measure the photoelectric conversion efficiency.

  Table 1 shows the results obtained in Examples 1 to 11 and Comparative Examples 1 to 3, where the ratio of the photoelectric conversion efficiency after the heat stress test is performed with respect to the photoelectric conversion efficiency before the heat stress test is performed as the retention rate.

  As is clear from Table 1, the photoelectric conversion efficiency retention rates of Examples 1 to 11 are higher than the photoelectric conversion efficiency retention rates of Comparative Examples 1 to 3, confirming the effects of the present invention. This is because leakage sources generated when a thermal load is applied are reduced by the present invention from being adsorbed to the proximal layer and the intermediate layer in which the average particle size of the contained semiconductor particles is small, that is, the specific surface area is large. It is believed that there is.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Support substrate, 2 Conductive layer, 3 Porous semiconductor layer, 4 Catalyst layer, 5 Counter electrode conductive layer, 6 Cover body, 7 Sealing part, 8 Carrier transport layer, 9 Porous insulating layer, 11 Conductive substrate, 12 Counter electrode , 13 Scribe line, 14 Current collecting electrode part, d Projection width.

Claims (3)

A photoelectric conversion element having, on a support substrate, at least a conductive layer, a porous semiconductor layer, a catalyst layer, a counter electrode conductive layer, and a carrier transport material filled in these voids,
The porous semiconductor layer is composed of a plurality of layers composed of semiconductor fine particles to which a sensitizing dye is adsorbed,
The plurality of layers include at least a proximal layer located on the side closest to the light receiving surface and a distal layer located on the side farthest from the light receiving surface;
The average particle size of the semiconductor fine particles constituting each of the plurality of layers is different from each other,
The average particle size of the semiconductor fine particles constituting the distal layer is larger than the average particle size of the semiconductor fine particles constituting the proximal layer,
The distal layer covers all of the proximal layer, and when the porous semiconductor layer is projected horizontally with respect to the support substrate, the end of the distal layer is outside the end of the proximal layer. projecting width d that is formed Ri der least 0.5 mm,
The average particle size of the semiconductor fine particles constituting the distal layer is 100 nm or more and 500 nm or less,
The minimum value of the particle size of the semiconductor fine particles constituting the distal layer is larger than the maximum value of the particle size of the semiconductor fine particles constituting the other layer in the porous semiconductor layer,
The thickness of the said distal layer is 10 micrometers or more and 40 micrometers or less, The photoelectric conversion element characterized by the above-mentioned . Further comprising an intermediate layer between the proximal layer and the distal layer;
The intermediate layer has a horizontal projected area with respect to the support substrate equal to that of the proximal layer, includes 10% to 50% by weight of semiconductor fine particles having a particle size of 50 nm or more, and has a thickness of 5 μm to 10 μm. The photoelectric conversion element according to claim 1, wherein: A photoelectric conversion module in which two or more photoelectric conversion elements are connected in series,
At least one of the photoelectric conversion elements is the photoelectric conversion element according to claim 1 or 2 , wherein a counter electrode conductive layer of one photoelectric conversion element and a conductive layer of the other photoelectric conversion element are adjacent to each other. A photoelectric conversion module that is electrically connected.

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