JP2005285473A - Photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent photoelectric conversion device that decreases an internal resistance to increase conversion efficiency by performing an electron transfer rapidly in a photosensitive layer, as well as enabling cost reduction. <P>SOLUTION: A photoelectric conversion device includes a support substrate 1 serving as only one side electrode, a photosensitive layer 2 formed on the support substrate 1 and containing a semiconductor onto which a sensitizing pigment is adsorbed, a transparent electroconductive layer 5 arranged opposite to the support substrate 1, a photosensitive layer 2 containing the semiconductor, and a charge transfer layer 4 charged between transparent electroconductive layer 5 and the support substrate 1. A gauze-shaped structural elements 7 are arranged nearly parallel to the support substrate 1, and the photosensitive layer 2 is charged underneath the gauze-shaped structural elements 7 and covers the top of the gauze-shaped structural elements 7. Since the gauze-shaped structural elements 7 made up of metals within the the photosensitive layer 2 are present, the internal resistance of the the photosensitive layer 2 can be reduced. Consequently, charge transfers within the photosensitive layer 2 becomes favorable, and thus optical current of the photoelectric conversion device can be increased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion device that can be expected to have high photoelectric conversion efficiency, is excellent in weather resistance and durability, and can be reduced in cost.

Since dye-sensitized solar cells do not require high-temperature treatment or vacuum equipment, it is considered advantageous for reducing the cost of solar cells, and research and development have been promoted rapidly in recent years.
In this method for producing a dye-sensitized solar cell, for example, a photosensitive layer containing titanium oxide fine particles having a particle size of several tens of nanometers is applied on a conductive glass substrate and sintered to obtain a porous titanium oxide layer. A single molecule of organic dye is adsorbed on the particle surface of the titanium oxide layer. The pole thus formed is referred to as a “light working electrode”. On top of this, a transparent conductive glass counter electrode sputtered with platinum is placed so as not to contact the titanium oxide layer. An electrolyte solution containing an iodine / iodide redox pair is filled between both glass substrates, and this electrolyte solution is sealed to fabricate a solar cell.

By making the titanium oxide layer porous, the surface area of the light working electrode can be increased by 1000 times or more, and light absorption by the adsorbing dye can be efficiently performed. Photoelectric conversion efficiency of about 10% at the research level and around 7% at the reproduction level is known. For this reason, further improvement in photoelectric conversion efficiency is required for market introduction.
Japanese Unexamined Patent Publication No. 2000-285975 JP 2001-283944 JP JP 2001-283945 A

The conventionally known dye-sensitized solar cell has a form in which a porous oxide semiconductor layer is formed on a support substrate and a sensitizing dye is adsorbed on the surface. It is common. However, since the porous oxide semiconductor layer is usually made of a semiconductor material such as titanium oxide, its conductivity is insufficient.
For this reason, even if electrons are rapidly injected from the excited dye into the oxide semiconductor layer, the oxide semiconductor layer prevents the movement of electrons and acts as an internal resistance until reaching the substrate electrode.

Further, when the electrode area is increased, the sheet resistance is increased and it becomes difficult to extract a large current.
An object of the present invention is to provide an excellent photoelectric conversion device capable of reducing the internal resistance and increasing the conversion efficiency by rapidly moving the electrons in the photosensitive layer and reducing the cost.

  The photoelectric conversion device of the present invention includes a support substrate that serves as one electrode, a photosensitive layer that is formed on the support substrate and includes a semiconductor to which a sensitizing dye is adsorbed, and a transparent conductive material that is disposed to face the support substrate. A charge transfer layer filled between the layer, the photosensitive layer, and the transparent conductive layer, wherein the metal mesh structure is disposed substantially parallel to the support substrate, and the photosensitive layer is the gold layer. The upper surface of the network structure is covered.

According to the structure of the present invention, since the metal mesh structure made of metal exists in the photosensitive layer, the internal resistance of the photosensitive layer can be reduced. Therefore, the movement of charges in the photosensitive layer is improved, and the photocurrent of the photoelectric conversion device can be increased.
Further, since the resistivity of the metal itself is small, the sheet resistance of the photosensitive layer covering the metal mesh structure can be reduced. For this reason, even when the area is increased, the internal resistance of the photoelectric conversion device does not increase and the photocurrent does not decrease.

In addition, since there is a metal mesh structure made of metal in the photosensitive layer, incident light is reflected by the metal. The energy of incident light can be used effectively. For this reason, it leads to the increase in photoelectric conversion efficiency.
Furthermore, since many appropriate openings are formed in the wire mesh structure, the light transmitted from the upper part can be transmitted and the light can be applied to the photosensitive layer disposed at the lower part of the wire mesh structure. The energy of incident light can be used effectively.

Further, since the photosensitive layer covers the upper surface of the wire mesh structure, even if the substrate or the counter electrode is distorted or warped, the wire mesh structure and the counter electrode are contacted to cause a short circuit. Can be prevented.
It is preferable that the wire mesh structure is not electrically connected to a support substrate serving as the one electrode. If the support substrate serving as the one electrode is electrically connected to the wire mesh structure, the photoelectric conversion action of the photosensitive layer between the support substrate and the wire mesh structure cannot be used.

In addition, the photoelectric conversion device of the present invention includes a wire mesh structure that serves as one electrode, a photosensitive layer that is formed on the wire mesh structure and includes a semiconductor to which a sensitizing dye is adsorbed, and the wire mesh structure. It is characterized by comprising a transparent conductive layer disposed oppositely, the photosensitive layer, and a charge transfer layer filled between the transparent conductive layer.
With this structure, since the photosensitive layer is formed on the metal mesh structure made of metal, the internal resistance can be reduced. Therefore, the movement of charges is improved, and the photoelectric conversion device photocurrent can be increased.

Further, since the resistivity of the metal itself is small, the sheet resistance can be reduced. For this reason, even when the area is increased, the internal resistance of the photoelectric conversion device does not increase and the photocurrent does not decrease.
Further, incident light is reflected by a metal mesh structure made of metal, and the energy of incident light can be used effectively. For this reason, it leads to the increase in photoelectric conversion efficiency.
Furthermore, since the photosensitive layer covers the upper surface of the wire mesh structure, the wire mesh structure and the counter electrode come into contact with each other and cause a short circuit when the substrate or the counter electrode is distorted or warped. Can be prevented.

The wire mesh structure can be installed on a support substrate. Thus, even when an external force is applied, the stress can be absorbed by the insulating support substrate, so that the strength of the photoelectric conversion device can be increased and the structure of the photoelectric conversion device can be stabilized.
The metal mesh structure is, for example, a combination of metal wires having a substantially circular cross section, preferably having a metal line length of 1 mm or less and a distance between lines of 1.5 times or more of the line length. . With the structure of the wire mesh structure, the internal resistance can be sufficiently reduced, and light shielding can be suppressed as much as possible. If the meridian exceeds 1 mm, the internal resistance is reduced, but incident light is shielded and sufficient photoelectric conversion efficiency cannot be obtained. Also, even if the line spacing distance is less than 1.5 times the line length, the incident light is blocked and sufficient photoelectric conversion efficiency cannot be obtained.

  The metal mesh structure may be a metal plate in which a large number of holes are formed. The aperture ratio of the holes is 10 to 90%. This is because if less than 10%, incident light is shielded and sufficient conversion efficiency cannot be obtained, and if it exceeds 90%, sufficient strength cannot be maintained.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking a dye-sensitized solar cell as an example of the photoelectric conversion device of the present invention.
FIG. 1 is a cross-sectional view showing the structure of a dye-sensitized solar cell.
This dye-sensitized solar cell has a support substrate 1 serving as one electrode and a photosensitive layer 2 formed on the support substrate 1 and containing a semiconductor to which a sensitizing dye 3 is adsorbed. Further, a translucent substrate 6 having a transparent conductive layer 5 formed on the lower surface is disposed opposite to the support substrate 1, and the charge transfer layer 4 is filled between the support substrate 1 and the transparent conductive layer 5. Has been.

Further, a wire mesh structure 7 is disposed substantially parallel to the support substrate 1 and between the photosensitive layers 2. That is, the photosensitive layer 2 covers the upper part of the wire mesh structure 7 and fills the space between the wire mesh structure 7 and the space between the wire mesh structure 7 and the support substrate 1. Yes.
As the wire mesh structure 7, what is called a “wire mesh” is used. The metal material is preferably composed of at least one selected from aluminum, nickel, platinum, chromium, gold, silver, copper, iron, titanium, tantalum, ruthenium, iron, zinc, molybdenum, Alternatively, it is composed of an alloy containing at least one selected from these, or a metal or alloy containing at least one selected from these is plated on the surface of a conductive network support such as iron. It is composed by doing. More preferably, the wire mesh structure 7 is mainly composed of one or more kinds of metals selected from aluminum, copper, titanium, nickel, iron, zinc, and molybdenum. The metal material is particularly preferably a material that reflects the entire wavelength range of visible light.

  There are many types of wire mesh structures 7, but a very general crimp wire mesh (a wire mesh structure in which strands are processed into a uniform waveform and vertical and horizontal lines are alternately knitted at a predetermined pitch at right angles. Body), in particular, a crimp wire mesh having a circular cross section. When the cross section of the metal wire is circular, once incident light repeats multiple reflections at various angles, it is difficult for light to escape to the outside, and light can be used effectively.

FIG. 2 shows a plan view of a typical crimp wire mesh.
Crimp wire meshes include weaves such as arched crimps, flat top crimps, semi-inter crimps, woven crimps, and rock crimps. In addition, plain woven wire mesh, twill woven wire mesh, semi-woven twill woven wire mesh, rectangular woven wire mesh wire, spiral woven wire mesh and the like are also used.
Furthermore, a wire mesh structure woven with plain woven, twill woven, twill woven, double twisted woven, reverse flat woven, reverse twill woven, double twill woven, cocoon woven, double twill woven, etc. The body 7 can also be used. However, these are not preferable because the number of openings is small, and in particular, when a metal wire is densely woven like a flat woven, light incident perpendicularly is reflected to the outside as it is. If it is used, it is better to use it in the interior other than both ends, rather than arranging it at both ends when using a laminated structure. Also, a wire mesh structure 7 such as expanded metal can be used.

In addition to the metal mesh structure 7 woven with metal wires, a single metal plate in which a large number of holes are formed may be employed.
FIG. 3 shows a plan view of such a single perforated metal plate. The aperture ratio of the holes is 10 to 90%, and the thickness of the metal plate is 0.01 to 2 mm.
By using the wire mesh structure 7 as described above, the in-plane sheet resistance value can be extremely reduced, and a large current can be taken out even if the area is large.

  The light irradiated to the dye-sensitized solar cell enters the photosensitive layer 2 and repeats complex reflection, absorption, and transmission. For example, a part of the light irradiated to the dye-sensitized solar cell is absorbed by the dye film, but most of it is transmitted and passes through the porous photosensitive layer 2. Then, the light that has passed through the porous photosensitive layer 2 is reflected by the surface of the metal mesh structure 7 and reaches the dye film again, where a part of the reached light is absorbed and a part is transmitted. , Some are reflected. The reflected light is reflected on the surface of the wire mesh structure 7. By repeating such complex multiple reflection, effective light absorption is performed a plurality of times by the dye film, and efficient power generation can be realized.

Moreover, as shown in FIG. 4, the light which permeate | transmitted can be utilized more effectively by laminating | stacking multiple (2 pieces in FIG. 4) the metal-mesh structure 7a, 7b.
In the conventional semiconductor electrode, the specific surface area is increased by increasing the thickness of the photosensitive layer. However, in this case, the resistance value increases rapidly and a large current cannot be extracted.
On the other hand, in the present invention, the resistance value of the metal mesh structure itself is very small, so even if the thickness of the photosensitive layer is increased by laminating the metal mesh structure in this way, the internal resistance value is increased. A large current can be taken out without causing

  In the case of using a plurality of layers of metal mesh structures, the mesh shift angle θ between adjacent metal mesh electrodes is 45 degrees or less, in particular, an angle within a range of 5 to 45 degrees. It is preferable to arrange them so that they are displaced. In particular, it is preferable to sequentially stack the meshes so that the mesh shift angle θ is shifted in the same rotational direction at an angle in the range of 5 to 45 degrees. It is desirable that the angle θ per shift layer is constant.

The support substrate 1 includes a single metal substrate and a conductive film formed on an insulating substrate.
Examples of the single metal substrate include thin metal substrates such as titanium, stainless steel, aluminum, silver, and copper. Further, a conductive resin sheet impregnated with fine particles or fine wires of carbon or metal may be employed.

In the case where a conductive film is formed on an insulating substrate, the insulating substrate may be a resin sheet such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyimide, polycarbonate, soda glass, borosilicate glass, or ceramic. Inorganic sheets and organic-inorganic hybrid sheets are preferred. As a conductive film formed thereon, a metal thin film such as titanium, stainless steel, aluminum, silver, or copper, a transparent conductive film such as ITO, SnO ₂ : F, ZnO: Al, Ti / ITO / TiTi / Ag / Ti, or the like The laminated conductive film is preferable.

  The method for laminating the conductive film is arbitrary, and for example, a vacuum deposition method, an ion plating method, a sputtering method, an electrolytic deposition method, or the like can be adopted. It may be formed by a plating method or a printing method. It can also be formed by transferring a metal foil onto an insulating resin substrate. The thickness of the conductive film 1a to be formed is in the range of 0.01 μm to 2 mm, preferably 3 μm to 2 mm, and more preferably 50 μm to 0.5 mm.

Note that if the support substrate 1 has light reflectivity, the transmitted light can be reflected and reused. Therefore, it is preferable to use a conductive material having high light reflectivity.
For the photosensitive layer 2 including a semiconductor formed on the support substrate 1, a porous one-conductive transporter is used. By making this one-conductivity-type transporter a porous body, the pn junction area is increased, the surface area for supporting the dye is increased, and the photoelectric conversion efficiency can be increased.

As the material for the one conductivity type transporter, a metal oxide semiconductor is usually used. This metal oxide semiconductor is preferably formed by aggregating a plurality of granular bodies or linear bodies (needle-like bodies, tube-like bodies, columnar bodies, etc.).
Titanium oxide (TiO ₂ ) is optimal as the material and composition of the metal oxide semiconductor. Other materials and compositions include titanium (Ti), zinc (Zn), tin (Sn), niobium (Nb), indium (In), yttrium (Y), lanthanum (La), zirconium (Zr), tantalum (Ta ), Hafnium (Hf), strontium (Sr), barium (Ba), calcium (Ca), cadmium (Cd), antimony (Sb), iron (Fe), tungsten (W) and vanadium (V) Of these, a metal oxide semiconductor containing at least one of them as a main component is preferable.

Specific examples include tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, titanium oxide, and strontium titanate.
In addition, these metal oxide semiconductors contain one or more of non-metallic elements such as nitrogen (N), carbon (C), fluorine (F), sulfur (S), chlorine (Cl), and phosphorus (P). You may let them.

Any of these metal oxide semiconductors has an electronic energy band gap in the range of 2 eV to 5 eV, which is larger than the energy of visible light. In particular, an n-type semiconductor in which the electronic energy level of the conduction band of the metal oxide semiconductor is lower than the electronic energy level of the conduction band of the dye is preferable.
The metal oxide semiconductor is preferably a porous body having a porosity of 20% to 80%, more preferably 40% to 60%. The reason for this is that a porous material with this degree of porosity can increase the surface area of the light working electrode to more than 1000 times that of a zero-porosity material, thus improving the efficiency of light absorption, power generation, and electron conduction. This is because it can be done well.

  The shape of the porous body is preferably a shape having a large surface area and a small electrical resistance. Usually, it should be composed of fine particles or fine lines. The average particle diameter or average line diameter is preferably 5 nm to 500 nm, and more preferably 10 nm to 200 nm. Here, if the lower limit value 5 nm in the average wire diameter of 5 nm to 500 nm is less than this, it becomes difficult to make the material finer, and if the upper limit value 500 nm is exceeded, the pn junction area is reduced and the photocurrent is significantly reduced. It is.

In addition, when the semiconductor becomes ultrafine particles, the band gap is no longer a value inherent to the material and depends on the size. Even with a material with a very small intrinsic band gap (1 eV or less), the band gap can be reduced by nano-sizing. Since it can be increased, the absorption wavelength can be selected, and the sensitivity can be easily increased. Examples of the ultrafine particle semiconductor include CdS, CdSe, PbS, PbSe, CdTe, Bi ₂ S ₃ , InP, and Si.

As the sensitizing dye 3 to be adsorbed on the photosensitive layer 2 containing the semiconductor, it is effective to use a dye having a characteristic that the photocurrent efficiency (IPC) with respect to incident light extends to the long wavelength side. It is.
A bis-type squarylium cyanine dye can be given as a dye having such sensitivity extending to the longer wavelength side. This bis-type squarylium cyanine dye has an IPCE peak wavelength near 800 nm. In addition, azurenium salt compounds having a high IPCE at a wavelength of 700 nm or more, squalinic acid derivatives, triallylpyrazoline, hydrazone derivatives, biphenyldiamine derivatives, tri-p-tolylamine (TPTA), trisazo pigments, τ-type metal-free phthalocyanine, titanyl It is also effective to use dyes such as phthalocyanine, squarylium cyanine, black dye, coumarin, β-diketonate, Re complex, Os complex, Ni complex, Pd complex, and Pt complex.

As other examples of the dye, in addition to the metal complex dye, the organic dye, and the organic pigment, an inorganic dye, an inorganic pigment, an inorganic semiconductor, and the like may be used. In addition, the shape of the dye only needs to be at least one of molecules, ultrathin films, fine particles, ultrafine particles, and quantum dots.
As the translucent substrate 6, white plate glass having a small iron component has the highest transmittance and the best mechanical strength. In addition, a light-transmitting inorganic substrate such as blue plate glass, borosilicate glass, soda glass, ceramic, and sapphire, or a light-transmitting organic resin substrate such as polycarbonate may be used.

Further, the translucent substrate 6 may be flat on both sides, but it is better that the surface having an unevenness of the order of the wavelength of incident light has a light confinement effect.
The thickness of the translucent substrate 6 is preferably 0.05 mm to 6 mm depending on the material, the substrate size, and the use, and is preferably 3 mm to 4 mm from the viewpoint of strength and weight if it is used for roofing of glass and metric size.

The transparent conductive layer 5 is preferably a tin-doped indium oxide film (ITO film) produced by a low temperature growth sputtering method or a low temperature spray pyrolysis method. In addition, an impurity-doped zinc oxide film (ZnO film) produced by a solution growth method, a fluorine-doped tin dioxide film (SnO ₂ : F film) formed by a thermal CVD method, an impurity-doped indium oxide film (In ₂ O) ₃ membranes) can be used. As other film forming methods, there are a vacuum deposition method, an ion plating method, a dip coating method, a sol-gel method, and the like. If surface irregularities in the order of the wavelength of incident light are formed by the growth of these films, there is still a light confinement effect.

As the charge transfer layer 4, a hole transporter such as a gel electrolyte (p-type semiconductor, liquid electrolyte, solid electrolyte, electrolytic salt, etc.) is preferably used.
The charge transfer layer 4 is formed so as to fill the porous body of the photosensitive layer 2 containing the semiconductor. In this sense, it is also called “reverse porous body”. The electrolytic solution shows the best carrier mobility, but because of problems such as liquid leakage, gelled or solidified ones are preferred.

Examples of the material for the charge transfer layer 4 include transparent conductive oxides, electrolyte solutions, electrolytes such as gel electrolytes and solid electrolytes, organic hole transport agents, and ultrathin metal films.
As the transparent conductive oxide, a compound semiconductor containing monovalent copper, GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _3, etc. are preferable. Among them, a compound containing monovalent copper A semiconductor is good. As the compound semiconductor containing monovalent copper, CuI, CuInSe ₂ , Cu ₂ O, CuSCN, CuS, CuInS ₂ , CuAlSe ₂ and the like are preferable, and among these, CuI and CuSCN are preferable, and CuI is most preferable because it is easy to manufacture.

As the electrolyte solution, a quaternary ammonium salt or a Li salt is used. As the composition of the electrolyte solution, for example, a solution prepared by mixing tetrapropylammonium iodide, lithium iodide, iodine, or the like with ethylene carbonate, acetonitrile, methoxypropionitrile, or the like can be used.
The gel electrolyte is roughly classified into a chemical gel and a physical gel. A chemical gel is a gel formed by chemical bonding by a cross-linking reaction or the like, and a physical gel is gelled near room temperature due to physical interaction. As the gel electrolyte, acetonitrile, ethylene carbonate, propylene carbonate, or a mixture thereof was polymerized by mixing a host polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, polyacrylamide or the like. A gel electrolyte is preferred. When using a gel electrolyte or solid electrolyte, a low-viscosity precursor is included in the oxide semiconductor layer, and a two-dimensional or three-dimensional crosslinking reaction is caused by means such as heating, ultraviolet irradiation, or electron beam irradiation. Can be gelled or solidified.

  The solid electrolyte is preferably a solid electrolyte having a polymer chain such as polyethylene oxide, polyethylene oxide, or polyethylene having a salt such as sulfonimidazolium salt, tetracyanoquinodimethane salt, or dicyanoquinodiimine salt. As the molten salt of iodide, iodides such as imidazolium salt, quaternary ammonium salt, isoxazolidinium salt, isothiazolidinium salt, pyrazolidium salt, pyrrolidinium salt, pyridinium salt can be used.

  Examples of the molten salt of iodide include 1,1-dimethylimidazolium iodide, 1, methyl-3-ethylimidazolium iodide, 1-methyl-3-pentylimidazolium iodide, 1-methyl- 3-isopentylimidazolium iodide, 1-methyl-3-hexylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1,2-dimethyl-3-propylimidazole iodide, 1-ethyl- Examples thereof include 3-isopropylimidazolium iodide and pyrrolidinium iodide.

Examples of the organic hole transporting agent include triphenyldiamine (TPD1, TPD2, TPD3) and OMeTAD.
Next, another structure of the dye-sensitized solar cell of the present invention will be described.
FIG. 5 is a cross-sectional view showing another structure of the dye-sensitized solar cell.
This dye-sensitized solar cell includes a wire mesh structure 7 serving as one electrode and a photosensitive layer 2 formed on the wire mesh structure 7 and including a semiconductor to which the sensitizing dye 3 is adsorbed. A transparent substrate 6 having a transparent conductive layer 5 formed on the lower surface is disposed opposite to the wire mesh structure 7, and the charge transfer layer 4 is filled between the support substrate 1 and the transparent conductive layer 5. Has been.

The difference from the structure of the dye-sensitized solar cell in FIG. 1 is that there is no support substrate, and the wire mesh structure 7 also serves as one electrode of the support substrate.
The photosensitive layer 2 covers the upper part of the wire mesh structure 7 and fills the gaps of the wire mesh structure 7. In addition, the photosensitive layer 2 slightly protrudes below the wire mesh structure 7. The amount of protrusion of the photosensitive layer 2 to the lower part of the wire mesh structure 7 is arbitrary.

The configurations and compositions of the metal mesh structure 7, the photosensitive layer 2, the sensitizing dye 3, and the like are the same as those described above with reference to FIGS.
In the dye-sensitized solar cell using the wire mesh structure 7 as a lower electrode, the light irradiated to the dye-sensitized solar cell is multiple-reflected on the surface of the wire mesh structure 7 and is reflected multiple times by the dye film. As in the above-described dye-sensitized solar cell, effective light absorption is performed and efficient power generation is realized.

  Furthermore, since the support substrate can be omitted, the material cost of the support substrate can be saved, and a lightweight and flexible dye-sensitized solar cell structure can be realized. Since the photosensitive layer 2 covers the upper surface of the wire mesh structure 7, the wire mesh structure 7 when the wire mesh structure 7, the translucent substrate 6 or the counter electrode 5 is distorted or warped. It can prevent that the body 7 and the counter electrode 5 contact, and cause a short circuit.

  In the dye-sensitized solar cell of FIG. 5 as well, as described with reference to FIGS. 1 and 4, the thickness of the photosensitive layer is increased by laminating the wire mesh structure 7 inside the photosensitive layer 2. be able to. By laminating the metal mesh structure 7 and increasing the thickness of the photosensitive layer, the substantial surface area of the photosensitive layer can be increased without increasing the internal resistance value, and the conversion efficiency can be increased.

FIG. 6 is a cross-sectional view showing still another structure of the dye-sensitized solar cell.
This dye-sensitized solar cell is obtained by embedding a wire mesh structure 7 serving as one electrode in an insulating support substrate 1b.
As the material for the insulating support substrate 1b, a resin sheet such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyimide or polycarbonate, an inorganic sheet such as soda glass, borosilicate glass or ceramic, or an organic-inorganic hybrid sheet should be used. Can do.

This dye-sensitized solar cell can be manufactured by heating the insulating support substrate 1b to the softening point and partially embedding the dye-sensitized solar cell shown in FIG. 5 in the insulating support substrate 1b. it can.
By using the insulating support substrate 1b, the strength of the dye-sensitized solar cell can be increased and the durability can be improved.

Next, the manufacturing method of the above dye-sensitized solar cell is demonstrated.
First, a dispersion of semiconductor fine particles is prepared. In addition to the sol / gel method described above, this method can be used by grinding in a mortar, dispersing by pulverizing using a mill, or precipitating as fine particles in a solvent when synthesizing a semiconductor. Methods and the like.
Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like). At the time of dispersion, a polymer such as polyethylene glycol, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid as necessary. By changing the molecular weight of polyethylene glycol, a film that does not easily peel off can be formed, and the viscosity of the dispersion can be adjusted. Therefore, it is preferable to add polyethylene glycol.

Next, the wire mesh structure 7 is placed on the support substrate 1, and the semiconductor fine particles are disposed thereon. For this, the dispersion or colloidal solution of the semiconductor fine particles may be applied on the support substrate 1, and there is a method of printing the semiconductor fine particles on the support substrate 1 in addition to this method.
Note that the semiconductor fine particles may be formed in advance on the support substrate 1 by coating or printing, and the metal net-like structure 7 may be placed thereon, and the semiconductor fine particles may be stacked thereon. .

When the support substrate 1 is not used, the semiconductor fine particles are directly attached to the wire mesh structure 7 by coating or printing.
As a method for forming and adhering semiconductor fine particles, there are a roller method and a dip method as application systems, and an air knife method and a blade method as metering systems. In addition, as the application and metering can be applied to the same part, the wire bar method disclosed in Japanese Patent Publication No. 58-4589, the slide hopper method disclosed in US Pat. Nos. 2681294, 2761419, 2761791, etc. And the extrusion method and the curtain method. A spin method and a spray method are also preferable.

As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
The viscosity of the dispersion of semiconductor fine particles greatly depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as surfactants and binders. For a high viscosity liquid (for example, 0.01 to 500 Poise), an extrusion method, a casting method, a screen printing method, or the like is preferable. For low-viscosity liquids (for example, 0.1 Poise or less), the slide hopper method, wire bar method, or spin method is preferable, and a uniform film can be formed thereby. If there is a certain amount of coating, coating by the extrusion method is possible even in the case of a low viscosity liquid. As described above, a wet film forming method may be appropriately selected according to the viscosity of the coating liquid, the coating amount, the support substrate 1, the coating speed, and the like.

In the case of the present invention, semiconductor fine particles are filled between the metal mesh structures 7 and the semiconductor fine particles are also raised on the upper part of the metal mesh structures 7, so that the viscosity of the dispersion of the semiconductor fine particles is preferably high. Therefore, the coating method is preferably an extrusion method or a casting method.
The semiconductor fine particle layer is not limited to a single layer, but a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a multi-layer coating of a coating layer containing different types of semiconductor fine particles (or different binders and additives) You can also Multi-layer coating is also effective when the film thickness is insufficient with a single coating. For multilayer coating, an extrusion method or a slide hopper method is suitable. In the case of applying multiple layers, the multiple layers may be applied at the same time, or may be successively applied several times to several dozen times. Further, screen printing can be preferably used as long as it is sequentially overcoated.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer 2) increases, the amount of the supported dye increases per unit projected area, so that the light capture rate increases, but the diffusion distance of the generated electrons increases, resulting in an increase in charge. Loss due to recombination also increases. Therefore, the preferable thickness of the semiconductor fine particle layer attached to the wire mesh structure 7 or the support substrate is 0.1 to 100 μm. When used in a solar cell, the thickness of the semiconductor fine particle layer is preferably 0.5 to 30 μm, more preferably 1 to 25 μm. The coating amount of the semiconductor fine particles per 11 m ² of the support substrate is preferably 0.5 to 400 g, more preferably 1 to 100 g.

After coating, the semiconductor fine particle layer is baked in the atmosphere at 300 ° C. to 600 ° C., preferably 400 ° C. to 500 ° C., for 10 minutes to 60 minutes, preferably 20 minutes to 40 minutes. Thus, a porous metal oxide semiconductor is produced. This technique is simple and effective when it can be formed in advance on a heat-resistant conductive sheet.
Next, the dye is adsorbed to the porous photosensitive layer 2 containing a semiconductor. Examples of the adsorption method include a method in which a substrate on which a photosensitive layer 2 containing a semiconductor is formed is immersed in a solution in which a dye is dissolved. When the substrate on which the photosensitive layer 2 containing a porous semiconductor is formed is immersed in a solution in which a dye is dissolved, the temperature of the solution and the atmosphere is not particularly limited, and examples include room temperature under atmospheric pressure. . The immersion time can be appropriately adjusted depending on the pigment, the type of solvent, the concentration of the solution, and the like. Thus, the dye can be adsorbed on the photosensitive layer 2 containing the porous semiconductor.

Examples of the solvent used for dissolving the dye include a mixture of one or more alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether, nitrogen compounds such as acetonitrile, and the like.
Further, the dye concentration in the solution is preferably about 5 × 10 ⁻⁵ to 2 × 10 ⁻³ mol / l.
Next, the translucent substrate 6 on which the transparent conductive layer 5 is formed is disposed on the support substrate 1 so that the transparent conductive layer 5 is on the bottom. At this time, the transparent conductive layer 5 is prevented from contacting the photosensitive layer 2 containing a semiconductor. In this state, the charge transfer layer 4 is injected between the transparent conductive layer 5 and the photosensitive layer 2 containing a semiconductor, and the space between the support substrate 1 and the translucent substrate 6 is sealed. The transparent conductive layer 5 may be provided with a collector electrode to reduce the electrical resistance.

In this way, a dye-sensitized solar cell can be produced.
With the configuration of the present invention, since the wire mesh structure 7 is present in the photosensitive layer 2, the internal resistance of the photosensitive layer 2 can be reduced. Therefore, the movement of charges in the photosensitive layer 2 becomes good, the photocurrent of the photoelectric conversion device can be increased, and the photoelectric conversion efficiency can be improved.

A glass plate with a transparent conductive film such as SnO ₂ having a thickness of 0.4 mm (size: 1 cm × 2 cm) was used as the support substrate. Porous titanium dioxide was formed by screen printing on a wire mesh structure 7 made of titanium having a wire diameter of 0.8 mm and a line spacing distance of 2.2 mm. In the manufacturing method of titanium dioxide as an electron transporter, first, acetylacetone was added to TiO ₂ anatase powder, and then kneaded with deionized water to prepare a titanium oxide paste stabilized with a surfactant. The prepared paste was applied at a constant speed onto the surface on which the translucent conductive film was formed by the doctor blade method, and baked at 450 ° C. for 30 minutes in the air.

N719 dye is used as the dye, acetonitrile and t-butanol (1: 1 by volume) are used as the solvent used to dissolve the dye, and the support substrate on which the metal oxide semiconductor layer is formed is dissolved in the dye. The dye was supported on the metal oxide semiconductor by dipping in the solution.
Next, platinum was coated on a PET film with an ITO film by a sputtering apparatus. The transparent conductive sheet and the dye-supported titanium dioxide-attached titanium sheet were faced to each other, and the following electrolytic solution was added between the transparent conductive sheet and lightly bonded to evaluate the characteristics.

Here, as the hole transporter, a gel electrolyte or a solid electrolyte is preferable, but in this example, iodine (I ₂ ), lithium iodide (LiI) and acetonitrile solutions as liquid electrolytes were prepared and used. In this way, a dye-sensitized solar cell was produced.
The stacked photoelectric conversion device thus obtained was measured at 100 mW / cm ² under AM 1.5, and as a result, the photoelectric conversion efficiency was improved by 10% or more compared to the conventional stacked solar cell not subject to the present invention. did.

  As described above, in this example, the stacked photoelectric conversion device of the present invention can be easily and easily manufactured, and high photoelectric conversion efficiency can be realized.

It is sectional drawing which shows the structure of the dye-sensitized solar cell of this invention which has arrange | positioned the metal mesh structure 7 on the support substrate. 3 is a plan view of a wire mesh structure 7. FIG. 3 is a plan view of a wire mesh structure 7. FIG. It is sectional drawing which shows the structure of the dye-sensitized solar cell of this invention which has arrange | positioned the metal net-like structure body 7 on a support substrate doubly. 3 is a cross-sectional view showing the structure of a dye-sensitized solar cell in which a photosensitive layer is directly attached to a wire mesh structure 7. FIG. It is sectional drawing which shows the structure of the dye-sensitized solar cell which embedded the metal-mesh structure 7 in the insulating support substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 1b Insulating substrate 2 Photosensitive layer 3 Sensitizing dye 4 Charge transfer layer 5 Transparent conductive layer 6 Translucent substrate 7, 7a, 7b Wire mesh structure

Claims (7)

On the other hand, a support substrate to be an electrode,
A photosensitive layer comprising a semiconductor formed on the support substrate and adsorbed with a sensitizing dye;
A transparent conductive layer disposed facing the support substrate;
A charge transfer layer filled between the photosensitive layer and the transparent conductive layer;
A photoelectric conversion device, wherein a metal mesh structure is disposed substantially parallel to the support substrate, and the photosensitive layer covers an upper surface of the metal mesh structure.   The photoelectric conversion device according to claim 1, wherein the wire mesh structure is electrically disconnected from the support substrate. On the other hand, a wire mesh structure as an electrode,
A photosensitive layer comprising a semiconductor formed on the wire mesh structure and adsorbed with a sensitizing dye;
A transparent conductive layer disposed opposite to the wire mesh structure;
A photoelectric conversion device comprising: the photosensitive layer; and a charge transfer layer filled between the transparent conductive layer.   The photoelectric conversion device according to claim 3, wherein the wire mesh structure is installed on a support substrate.   The photoelectric conversion device according to any one of claims 1 to 4, wherein the wire mesh structure is a metal plate in which a large number of holes are formed.   6. The wire mesh structure according to any one of claims 1 to 5, wherein the metal mesh structure is mainly composed of one or more kinds of metals selected from aluminum, copper, titanium, nickel, iron, zinc, and molybdenum. The photoelectric conversion device described in 1.   The semiconductor is mainly composed of one or more oxides selected from tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, titanium oxide, and strontium titanate. The photoelectric conversion device according to any one of claims 1 to 6.

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