JP4379865B2 - Photoelectrode, method for producing the same, and solar cell using the same - Google Patents

Description

  The present invention relates to a photoelectrode, a method for producing the same, and a solar cell using the photoelectrode, and more particularly to a photoelectrode suitably used for a dye-sensitized solar cell, a method for producing the photoelectrode, and a solar cell using the photoelectrode. Is.

  Dye-sensitized solar cells composed of photoelectrodes, etc., with Ru dye (ruthenium bipyridine complex) adsorbed on the surface of porous titanium dioxide have been attracting worldwide attention since Gretzell et al. Collecting. In general, titanium dioxide can be used efficiently only mainly in the ultraviolet light of sunlight, but this dye-sensitized solar cell can absorb light in the visible light region. This dye-sensitized solar cell not only has a high theoretical limit value of photoelectric conversion efficiency compared to conventional silicon solar cells, but also does not require much energy for production like silicon solar cells, and is an inexpensive material There exists an advantage that it can manufacture using (for example, refer nonpatent literature 1).

  However, the actual photoelectric conversion efficiency of the dye-sensitized solar cell that has been developed so far is still considerably lower than the theoretical limit value, and it is necessary to increase the photoelectric conversion efficiency for practical use. . There have been many studies aimed at increasing the photoelectric conversion efficiency of dye-sensitized solar cells, such as the development of high-performance sensitizing dyes, the search for composite oxide semiconductor electrodes, and the improvement of electrolytes. However, it does not lead to a significant improvement in photoelectric conversion efficiency.

  In addition, as another attempt to improve the photoelectric conversion efficiency of a solar cell, a method for improving a metal oxide semiconductor has also been reported. For example, since the band gap of normal anatase type or rutile type titanium dioxide is 3.2 eV or 3.0 eV, respectively, only ultraviolet light in sunlight can be used. In order to use the wavelength in the visible light region, a method such as doping with metal ions such as vanadium (V) or chromium (Cr) is used (for example, see Patent Document 1). By such a method, the solar cell having an electrode using titanium dioxide having a small band gap has improved photoelectric conversion efficiency as compared with that using ordinary titanium dioxide. However, the photoelectric conversion efficiency is very low in comparison with the dye-sensitized solar cell.

Furthermore, there is a method using improved porous titanium dioxide in a dye-sensitized solar cell in order to improve photoelectric conversion efficiency. For example, a dye-sensitized solar cell using a titanium dioxide electrode doped with fluorine (F) has been proposed (see, for example, Patent Document 2). This fluorine-doped titanium dioxide electrode has a titanium dioxide porous membrane manufactured using a paste made of titanium dioxide, a fluorine atom donating compound, water, or N, N-dimethylformamide. And it is reported that the photoelectric conversion efficiency of the solar cell using this electrode improves to 5.29% at the maximum.
International Publication No. WO01 / 048833 Pamphlet (published July 5, 2001) JP 2002-25637 A (published January 25, 2002) O'Regan, B., Graetzel, M. "A low-cost, high-efficiency solor cell based on dye-sensitized colloidal TiO2 films" Nature, 353, 1991, p 737-740.

  However, in the conventional solar cell, the photoelectric conversion efficiency is not yet sufficient, and further improvement of the photoelectric conversion efficiency is necessary for practical use.

  For example, in the dye-sensitized solar cell using a fluorine-doped titanium dioxide electrode reported in Patent Document 2, the photoelectric conversion efficiency is improved to 5.29%, but the band gap is controlled. Is not enough.

  The present invention has been made in view of the above problems, and its purpose is to provide a photoelectrode for improving the photoelectric conversion efficiency of a dye-sensitized solar cell, a method for producing the same, and a solar cell using the photoelectrode. It is to provide.

  As a result of intensive investigations to solve the above problems, the present inventor has replaced at least two metal oxide semiconductors that are usually used with at least two kinds selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. It has been found that by forming a photoelectrode using a novel metal oxide semiconductor doped with an element, the photoelectric conversion efficiency of a solar cell manufactured using this photoelectrode is dramatically improved. It came to complete.

  That is, in order to solve the above problems, the photoelectrode according to the present invention is a metal formed on at least one surface of a transparent conductive substrate having conductivity and the surface of the transparent conductive substrate having conductivity. A photoelectrode including a metal oxide semiconductor layer containing oxide semiconductor particles, wherein the metal oxide semiconductor of the metal oxide semiconductor layer is selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur It is characterized by being doped with at least two kinds of elements.

  The metal oxide semiconductor is preferably doped with nitrogen and at least one element selected from the group consisting of carbon, hydrogen, and sulfur. The metal oxide semiconductor is preferably doped with nitrogen at a concentration of 700 wtppm or more and 10,000 wtppm or less. It is preferable that nitrogen doped in the metal oxide semiconductor is desorbed as nitrogen molecules when the temperature rises, and the nitrogen molecule desorption peak temperature is 700 ° C. or higher. It is preferable that a sensitizing dye is adsorbed on the metal oxide semiconductor layer. The metal oxide semiconductor is preferably titanium dioxide.

  Moreover, the solar cell concerning this invention is characterized by including the said photoelectrode, a counter electrode, and the electric charge transfer layer which contacts this photoelectrode and a counter electrode.

  The method for producing a photoelectrode according to the present invention includes forming a semiconductor film using metal oxide semiconductor particles doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. The coating agent for forming a semiconductor film is prepared, and the coating agent for forming a semiconductor film is applied or printed on the conductive surface of a transparent conductive substrate having at least one surface of the conductive film to form a semiconductor film. It is characterized by heating as described above.

  As described above, the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. Therefore, the band gap is controlled. Therefore, the electron injection, electron, and charge transport characteristics of the dye-sensitized solar cell using the photoelectrode are improved, and the photoelectric conversion efficiency of the solar cell can be improved.

  As described above, the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is doped with nitrogen and at least one element selected from the group consisting of carbon, hydrogen, and sulfur. Therefore, the stability is good and the deterioration of the photoelectrode can be reduced.

  Since the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is doped with nitrogen at a concentration of 700 wtppm or more and 10000 wtppm or less as described above, the band gap is better controlled. . Therefore, there is an effect that the photoelectric conversion efficiency of the dye-sensitized solar cell using the photoelectrode can be further improved.

  Nitrogen doped in the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is desorbed as nitrogen molecules by the temperature rise, and the nitrogen molecule desorption peak temperature is 700 ° C. or higher. Therefore, the thermal stability of the crystal structure of the metal oxide semiconductor is good. Therefore, there is an effect that the thermal stability of the photoelectrode can be improved and deterioration can be reduced.

  Since the sensitizing dye is adsorbed to the metal oxide semiconductor layer included in the photoelectrode according to the present invention, light in the visible light region can be used. Therefore, there is an effect that the photoelectric conversion efficiency of the dye-sensitized solar cell using the photoelectrode can be further improved.

  Since the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is titanium dioxide as described above, the band gap is controlled better. Therefore, there is an effect that the photoelectric conversion efficiency of the dye-sensitized solar cell using the photoelectrode can be further improved.

  As described above, the solar cell according to the present invention includes the photoelectrode, the counter electrode, and the charge transfer layer in contact with the photoelectrode and the counter electrode. Therefore, the band of the metal oxide semiconductor included in the photoelectrode. The gap is controlled. Therefore, the electron injection, electron and charge transport characteristics of the solar cell according to the present invention are improved, and the photoelectric conversion efficiency of the solar cell can be improved.

  A photoelectrode according to the present invention, a method for producing the same, and a solar cell using the photoelectrode will be described below. In addition, although the photoelectrode concerning this invention is used suitably especially for a dye-sensitized solar cell, of course, it is not limited to this, It is used suitably for various solar cells.

(1) A metal oxide semiconductor doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. The photoelectrode according to the present invention has at least one surface having conductivity. A photoelectrode comprising a conductive substrate and a metal oxide semiconductor layer containing metal oxide semiconductor particles formed on a conductive surface of the transparent conductive substrate, the metal oxide The metal oxide semiconductor of the semiconductor layer is doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. Hereinafter, the metal oxide semiconductor and the method of doping the element will be described in this order.

<Metal oxide semiconductor doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur>
The metal oxide semiconductor is doped with at least two elements selected from the group consisting of at least carbon, hydrogen, nitrogen, and sulfur.

  In a dye-sensitized solar cell, light incident on a metal oxide semiconductor layer, which is a photosensitive layer and adsorbs a sensitizing dye, excites the sensitizing dye. The excited sensitizing dye injects high-energy excited electrons into the conduction band of the metal oxide semiconductor, and the conductor electrons further reach the transparent conductive substrate by diffusion. The electron-injected sensitizing dye molecule becomes an oxidant deficient in electrons, and this is reduced by donating electrons from the charge transfer layer in contact with the dye. When used in a dye-sensitized solar cell, the crystal structure of the metal oxide semiconductor affects the open-circuit voltage value, electron injection efficiency, and electron transport characteristics. The electron injection efficiency of the excited electrons into the metal oxide semiconductor depends on the bonding mode (ester-like bond, chelate bond, etc.) between the semiconductor and the dye, the strength of the interaction, and the conduction band of the metal oxide semiconductor. It is governed by the geometrical arrangement of the dye with the LUMO. Therefore, the metal oxide semiconductor doped with the above elements has a controlled band gap and smooth electron injection into the metal oxide semiconductor. In addition, the electron transport property in the metal oxide semiconductor is improved, and recombination of excited electrons can be suppressed. Therefore, the electron and charge transport characteristics of the solar cell using the metal oxide semiconductor are improved, and the photoelectric conversion efficiency can be improved.

In addition, the surface of the metal oxide semiconductor becomes more porous (specific surface area 67 m ² / g, undoped 55 m ² / g), and the amount of dye supported increases by 22% compared to the undoped one.

  A metal oxide semiconductor doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur is a state in which the doped element enters the crystal lattice or in the crystal. The structure is such that oxygen atoms are substituted for oxygen atoms. When the metal oxide semiconductor has such a structure, the band gap is controlled, and the electron and charge transport characteristics of the electrode can be improved.

For example, taking titanium dioxide as an example, titanium dioxide having the above structure is TiO _2-x N _x N _y A in chemical formula. Here, N _x is nitrogen contained in the position of oxygen in the titanium dioxide crystal, N _y is nitrogen contained in the lattice of the titanium dioxide crystal, A is carbon, sulfur, or hydrogen doped in titanium dioxide Means. In a state where doped nitrogen enters between crystal lattices, it is preferable that nitrogen atoms are bonded to Ti atoms of titanium dioxide in a Ti—N—O bonding state. In addition, in a state where the doped nitrogen is in the form of substitution of oxygen atoms at the oxygen position in the TiO ₂ crystal, the nitrogen atoms are bonded to Ti atoms of titanium dioxide in a Ti—N—Ti bonding state. It is preferable.

  In addition, among the above bonded states, a state in which the doped element is contained in a form in which oxygen atoms are substituted for oxygen atoms in the crystal is more preferable. Thereby, when it uses for a photoelectrode, stability of a titanium dioxide crystal structure can be improved more, and deterioration can be decreased more.

2 and 3 show the analysis results of the bonding state of doped nitrogen in the titanium dioxide particles. These are the results of XPS (X-ray photoelectron spectroscopy) analysis of particles after sputter etching using argon ions. FIG. 2 shows the analysis results for titanium dioxide particles doped with 3000 wtppm nitrogen and 150 wtppm carbon, and FIG. 3 shows the analysis results for titanium dioxide particles doped only with 525 wtppm nitrogen. 2 and 3, the peak with the lowest binding energy represents the concentration of nitrogen in the Ti—N—Ti bonding state. The peak at the center represents the concentration of nitrogen in the Ti—N—O bond state. The peak with the highest binding energy represents the concentration of nitrogen adsorbed on the surface of the titanium dioxide fine particles in the form of NH _x , and does not have a strong bond with Ti. . As is clear from the comparison between FIG. 2 and FIG. 3, in the titanium dioxide fine particles doped with nitrogen and carbon, many Ti—N—Ti bonding states in which oxygen atoms of titanium dioxide are replaced with nitrogen are detected. Further, the Ti—N—O bond state, which is in the state of entering the Ti—O gap, is also detected more than the titanium dioxide fine particles doped only with nitrogen.

  Since titanium dioxide fine particles doped with two or more kinds of elements have the above-mentioned bonding state, the bond between titanium dioxide Ti atoms and doped nitrogen atoms is strong. If so, the stability of the titanium dioxide crystal structure can be further improved and the deterioration can be reduced.

  Nitrogen doped in the metal oxide semiconductor is desorbed as nitrogen molecules when the temperature rises, and the nitrogen molecule desorption peak temperature is preferably 700 ° C. or higher.

  As a result, the thermal stability of the crystal structure of the metal oxide semiconductor can be improved and the deterioration can be reduced. Therefore, it is possible to solve the problem that nitrogen is desorbed during the sintering of the electrode at a commonly used temperature.

  For the same reason, it is preferable that the hydrogen doped in the metal oxide semiconductor is desorbed as a hydrogen molecule when the temperature is raised, and the hydrogen molecule desorption peak temperature is 700 ° C. or higher.

  Further, for the same reason, it is preferable that the carbon doped in the metal oxide semiconductor is desorbed as carbon dioxide molecules by raising the temperature, and the carbon dioxide molecule desorption peak temperature is 700 ° C. or higher.

Furthermore, for the same reason, the sulfur doped in the metal oxide semiconductor is desorbed as sulfur dioxide (SO ₂ ) molecules when the temperature is raised, and the sulfur dioxide molecule desorption peak temperature is 700 ° C. or higher. preferable.

  In addition, for example, in titanium dioxide doped only with nitrogen, it has been reported that the peak of Ti—N bond by XPS analysis disappears by heat treatment in air. This suggests the possibility of the problem of nitrogen desorption during electrode sintering. This is presumably because the Ti—N bond is unstable on the surface of the titanium dioxide particles in contact with air. As shown in Example 2 described below, doping two or more elements improves the thermal stability of the titanium dioxide crystal structure and allows nitrogen to be desorbed during sintering of the electrode at commonly used temperatures. It becomes possible to eliminate the problem of separation.

  The metal oxide semiconductor is more preferably doped with nitrogen and at least one element selected from the group consisting of carbon, hydrogen, and sulfur. In other words, the metal oxide semiconductor is preferably doped with nitrogen as an essential dopant, and with at least one element selected from the group consisting of carbon, hydrogen, and sulfur. Accordingly, since more nitrogen is doped and firmly bonded to the metal oxide semiconductor, the stability of the crystal structure of the metal oxide semiconductor is further improved. Therefore, the deterioration of the photoelectrode can be further reduced.

  The metal oxide semiconductor is more preferably doped with at least nitrogen and carbon among these.

  The metal oxide semiconductor is preferably doped with nitrogen at a concentration of 700 wtppm or more and 10000 wtppm or less, more preferably doped with a concentration of 1500 wtppm or more and 5000 wtppm or less, and a concentration of 2000 wtppm or more and 5000 wtppm or less. It is more preferable that it is doped, and it is particularly preferable that it is doped at a concentration of 2500 wtppm or more and 5000 wtppm or less. By not being below the lower limit of this range, good control of the band gap is possible, so that the photoelectric conversion efficiency of the solar cell using the photoelectrode of the present invention can be improved. On the other hand, when the concentration of nitrogen exceeds 10,000 wtppm, it takes time and labor for production, and is not practical. Here, for example, nitrogen is doped at a concentration of 700 wtppm means that the mass of doped nitrogen is 700 / 1,000,000 of the total mass of the metal oxide semiconductor including all doped elements. Indicates that there is.

  Further, as the concentration of each element other than nitrogen, the concentration of carbon or sulfur is preferably 50 wtppm or more and 1500 wtppm or less, and more preferably 100 wtppm or more and 1500 wtppm or less. The hydrogen concentration is preferably 1 wtppm or more and 50 wtppm or less. Thereby, stability of the crystal structure of the metal oxide semiconductor can be further improved, and deterioration can be reduced.

  When the concentration of each element other than nitrogen is expressed as a ratio to the concentration of nitrogen, the concentration of carbon or sulfur is preferably 1/30 or more and 1/3 or less of the nitrogen concentration. The hydrogen concentration is preferably 1/300 or more and 1/30 or less of the nitrogen concentration.

The metal oxide semiconductor is not particularly limited as long as it is a metal oxide semiconductor conventionally used in dye-sensitized solar cells. Specific examples include titanium dioxide (TiO ₂ ), tin dioxide (SnO ₂ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), tungsten oxide (WO ₃ ), and the like. Among these, the metal oxide semiconductor is more preferably titanium dioxide. The metal oxide semiconductor may be the above compound alone or a combination of two or more of the above compounds.

  In general, titanium dioxide has three types of transformation: rutile type (tetragonal system), anatase type (tetragonal system), and brookite type (orthorhombic system). Thus, it has a structure in which the ridges of the distorted octahedron are shared. In the case of using titanium dioxide, it is preferable to use a rutile type or anatase type, or a mixture thereof, and it is more preferable to use an anatase type as a raw material. The titanium dioxide after doping two or more of the above elements is also preferably a rutile type, anatase type, or a mixture thereof, and more preferably an anatase type.

  Further, the metal oxide semiconductor may be doped with another anion in addition to at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. Here, the other anions are not particularly limited. For example, selenium (Se), phosphorus (P), arsenic (As), silicon (Si), boron (B), fluorine (F) , Chlorine (Cl), bromine (Br), and the like.

<Method of doping a metal oxide semiconductor with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur>
The method of doping the metal oxide semiconductor with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur is not particularly limited, and a conventionally known method used in normal doping is used. It can be used by doping two or more elements simultaneously or sequentially. Specific examples of methods used in normal doping include a thermal diffusion method, a laser doping method, a plasma doping method, and an ion implantation method.

  In the thermal diffusion method, for example, each element can be doped by heat-treating a metal oxide semiconductor in a gas atmosphere containing the element.

As a specific example, as a method of doping nitrogen, a method of heat-treating metal oxide semiconductor particles in a reducing gas atmosphere containing a nitrogen-containing gas can be given. According to this manufacturing method, a metal oxide semiconductor doped with nitrogen can be easily and uniformly manufactured. Examples of the nitrogen-containing gas include N ₂ , NH ₃ , NO, NO _{2 and the} like. Further, in order to atmosphere reducing gas may be a mixed gas of the nitrogen gas and H ₂ gas.

Further, as a method of doping nitrogen and carbon, for example, cyan (HCN), cyanic acid or isocyanic acid (HOCN), lower amine (RNH ₂ , R ₂ NH, R ₃ N), etc., or these and NH ₃ The method of heat-processing the particle | grains of a metal oxide semiconductor in the gas stream containing this can be mentioned.

Further, as a method of doping nitrogen, carbon and hydrogen, a method of heat-treating metal oxide semiconductor particles in a gas atmosphere containing nitrogen, carbon and hydrogen or in an NH ₃ gas and carbon-containing gas atmosphere may be mentioned. Can do. Examples of the carbon-containing gas include hydrocarbon gas containing hydrogen, such as methane, ethane, propane, and butane, carbon monoxide, carbon dioxide, and the like, but it is more preferable to use hydrocarbon gas. . Here, for example, when a mixed gas of NH ₃ gas and hydrocarbon gas is used, it is preferable that the hydrocarbon gas has a smaller volume than the NH ₃ gas, and the hydrocarbon gas is 2 to 70 volumes with respect to the NH ₃ gas. %, More preferably 5 to 50% by volume.

  Here, as the gas containing the element, one kind of gas may be used, or two or more kinds of gases may be mixed and used. Further, an inert gas such as argon may be mixed.

  The temperature for the heat treatment in the gas atmosphere containing the above elements is preferably 500 ° C. or higher and 620 ° C. or lower, and more preferably 530 ° C. or higher and 590 ° C. or lower. Thereby, a metal oxide semiconductor with a well-controlled band gap can be obtained.

  Further, in the ion implantation method that is widely used at present, the above elements are doped by a method of implanting accelerated ions from a nitrogen anion, carbon anion, or sulfur anion source into a metal oxide semiconductor target using an ion implantation apparatus. can do.

Further, for example, as a method of doping nitrogen and carbon into titanium dioxide, a solution containing cyan, cyanic acid or isocyanic acid, a lower amine, an azo compound, a diazo compound or the like, or a solution containing these and NH ₃ is used. Among them, a method of hydrolyzing a solution-like titanium halide such as titanium tetrachloride (TiCl ₄ ) can be mentioned. Here, the said compound containing each element may use one type of compound, and may mix and use two or more types of compounds.

Further, as a method for doping with sulfur, specifically, for example, a heat treatment method in a hydrogen sulfide (H ₂ S) atmosphere can be given. The heat treatment temperature at this time is preferably 400 ° C. or higher and 700 ° C. or lower, and more preferably 500 ° C. or higher and 600 ° C. or lower. When the temperature is higher than the lower limit of this range, the heat treatment time can be shortened. On the other hand, when the temperature is lower than the upper limit of this range, growth due to sintering of the metal oxide semiconductor fine particles can be prevented.

The average particle diameter of the metal oxide semiconductor raw material particles used is preferably 1 μm or less, and more preferably 50 nm or less. The specific surface area of the raw material particles is preferably 100 m ² / g or more. Thereby, the said element can be doped in large quantities per unit volume, and also the surface area of the metal oxide semiconductor particle obtained can be enlarged.

  Further, the doping of the metal oxide semiconductor with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur may be performed at the metal oxide semiconductor particle stage. You may carry out after forming a semiconductor layer on a transparent electrode. Of these, the dope is more preferably performed at the particle stage. This makes it possible to avoid the complexity of the manufacturing process.

(2) Photoelectrode A photoelectrode according to the present invention comprises a transparent conductive substrate having at least one surface of conductivity, and a metal oxide semiconductor formed on the surface of the transparent conductive substrate having conductivity. And a metal oxide semiconductor layer containing particles. As described above, the metal oxide semiconductor of the metal oxide semiconductor layer is doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. Hereinafter, the photoelectrode according to the present invention will be described in the order of a transparent conductive substrate, a metal oxide semiconductor layer, and a sensitizing dye.

<Transparent conductive substrate>
The transparent conductive substrate may be any substrate as long as at least one surface of the transparent substrate made of a light-transmitting material has conductivity. Therefore, a conductive layer may be formed on the surface of at least one surface, or at least one surface itself may have conductivity. Among these, it is more preferable that the transparent conductive substrate has a conductive layer formed on the surface of at least one surface of the transparent substrate.

When the conductive layer or at least one surface itself has conductivity, the conductive portion is made of a conductive material and is formed so as not to impair the transparency of the transparent substrate. Examples of such conductive substances include metals, carbon, and conductive metal oxides. Examples of the conductive metal oxide include indium tin oxide (ITO), tin dioxide (SnO ₂ ), and fluorine-doped tin dioxide.

  The transparent substrate is not particularly limited as long as it is made of a light-transmitting material and can support the metal oxide semiconductor layer. Specific examples include glass, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and polyethersulfone. Further, the transparent substrate may be a plate or a film.

  Examples of the transparent conductive substrate include various combinations of the conductive material and the transparent substrate. Among them, a conductive glass substrate in which fluorine-doped tin dioxide or ITO is formed as a conductive layer. It is particularly preferred.

<Metal oxide semiconductor layer>
The metal oxide semiconductor layer is formed by forming a semiconductor film containing metal oxide semiconductor particles on the transparent conductive substrate. The thickness of the semiconductor film is preferably 0.1 μm to 100 μm, and more preferably 5 μm to 25 μm. If it is thicker than this range, the electron diffusion distance increases, and loss due to charge recombination increases. On the other hand, when it becomes thinner than this range, the amount of the sensitizing dye described later becomes small.

  The average particle size of the metal oxide semiconductor particles contained in the semiconductor film is preferably 20 nm to 100 nm, and more preferably 30 nm to 70 nm. Thereby, since a specific surface area becomes large, when using for a dye-sensitized solar cell, the adsorption amount of a pigment | dye increases and the photoelectric conversion efficiency of a solar cell can be improved.

  Further, the shape of the metal oxide semiconductor particles is not particularly limited, and for example, spherical or oblong particles can be suitably used. For example, when using oblong particles, the major axis is preferably 20 nm to 80 nm, and more preferably 30 nm to 50 nm. The ratio of the minor axis to the major axis is preferably 1: 2 to 1: 4.

Further, the semiconductor film preferably has a specific surface area of ^{60m 2} / ^g~500m 2 / g. By improving the porosity in this way, the amount of sensitizing dye carried increases and the mobility of the charge transfer layer also increases, so that the photoelectric conversion efficiency of the solar cell using the semiconductor film can be improved. it can. Further, by increasing the area for adsorbing the sensitizing dye, the adsorption amount of the sensitizing dye can be preferably increased by 10% to 50%, and the photoelectric conversion efficiency of the solar cell can be improved. The pore distribution of the semiconductor film according to the present invention is preferably 1 nm or more and 100 nm or less. Here, the pore distribution refers to the distribution of the pore volume with respect to the pore radius.

<Sensitizing dye>
More preferably, a sensitizing dye is adsorbed to the metal oxide semiconductor layer of the photoelectrode according to the present invention. A sensitizing dye refers to a dye having absorption in the visible light region and / or the infrared light region. By adsorbing a sensitizing dye to a metal oxide semiconductor that does not absorb light in the region, light absorption to the region can be sensitized.

  As the sensitizing dye, for example, a metal complex dye or an organic dye can be used. Specific examples of the metal complex dye include metal complexes such as phthalocyanine and porphyrin; chlorophyll or a derivative thereof; hemin; a ruthenium complex containing a bipyridine structure or the like as a ligand; a complex such as osmium, iron, or zinc. Can be mentioned. Specific examples of organic dyes include phenylxanthene dyes, coumarins, eosin-Y, metal-free phthalocyanines, cyanine dyes, merocyanine dyes, xanthene dyes, triphenylmethane dyes, and the like.

The sensitizing dye preferably has a bonding group for the surface of the metal oxide semiconductor in the molecule. Examples of the linking group include a carboxyl group; a sulfonic acid group; a cyano group; a —P (O) (OH) ₂ group; a —OP (O) (OH) ₂ group. Among them, it is preferable to have a carboxyl group, -P (O) (OH) ₂ group, or -OP (O) (OH) ₂ group.

  As a method of adsorbing the sensitizing dye to the semiconductor film, a conventionally known method can be used. Specifically, for example, a method of immersing the semiconductor layer in a sensitizing dye solution, gaseous sensitization, or the like. Examples thereof include a method of flowing a dye on the semiconductor layer. The solvent for dissolving the sensitizing dye is not particularly limited as long as it can dissolve the sensitizing dye. Specific examples include water, alcohol, toluene, dimethylformamide and the like. The semiconductor layer on which the sensitizing dye is adsorbed may be washed, dried and heated as necessary.

  The sensitizing dye is preferably adsorbed on the surface and / or layer of the metal oxide semiconductor layer.

(3) Method for producing photoelectrode The photoelectrode according to the present invention uses metal oxide semiconductor particles doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. A semiconductor film-forming coating agent is prepared, and the semiconductor film-forming coating agent is applied or printed on a conductive surface of a transparent conductive substrate having at least one surface conductive to form a semiconductor film. It is manufactured by heating to 100 ° C. or higher.

<Coating agent for semiconductor film formation>
The said coating agent for semiconductor film formation used in the manufacturing method of the photoelectrode concerning this invention is produced by disperse | distributing the said metal oxide semiconductor particle | grains uniformly to a dispersion medium.

  The method for preparing the coating agent for forming a semiconductor film is not particularly limited as long as the metal oxide semiconductor particles are uniformly dispersed. Specifically, for example, a sol- Examples thereof include a gel method, a method of grinding with a mortar, a method of dispersing while pulverizing using a mill, and a method of precipitating as fine particles in a solvent when a metal oxide semiconductor is synthesized.

  The mass ratio of the metal oxide semiconductor to the dispersion medium is not particularly limited, but the dispersion medium is 0.1 to 2000 parts by mass with respect to 100 parts by mass of the metal oxide semiconductor. It is preferable to use it, it is more preferable to use it in the ratio of 100-400 mass parts, and it is still more preferable to use it in the ratio of 200-400 mass parts. If it is smaller than this range, the coating solution for forming a semiconductor film becomes too viscous and difficult to handle. On the other hand, if it is larger than this range, the amount of metal oxide semiconductor is small, film formation is difficult, and sufficient photoelectric conversion efficiency cannot be obtained when used in solar cells.

  The average particle diameter of the primary particles of the metal oxide semiconductor before being dispersed in the dispersion medium is preferably 4 nm or more and 200 nm or less, and more preferably 10 nm or more and 50 nm or less. The average particle diameter of the secondary particles of the metal oxide semiconductor dispersed in the dispersion medium is preferably 10 nm or more and 100 μm or less, and more preferably 10 nm or more and 700 nm or less. Here, the secondary particles refer to aggregated primary particles.

  Further, the shape of the metal oxide semiconductor particles is not particularly limited, and for example, spherical or oblong particles can be suitably used. For example, when using oblong particles, the major axis of the primary particles is preferably 10 nm to 60 nm, and more preferably 30 nm to 40 nm. The ratio of the minor axis to the major axis is preferably 1: 2 to 1: 4.

  The dispersion medium is not particularly limited as long as it contains water or a conventionally known organic solvent used for a semiconductor film-forming coating agent. Examples of the organic solvent include methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like. Moreover, water or the said organic solvent may be used independently, and may be used in combination of 2 or more type. In the present specification, the “dispersion medium” refers to all components other than the metal oxide semiconductor in the coating for forming a semiconductor film. Therefore, the dispersion aid described later is also included in the “dispersion medium” in the present specification.

  As described above, the dispersion medium may be a conventionally known medium containing water or the above organic solvent, but from alkylene glycol, polyalkylene glycol, alkyl ether of alkylene glycol, and alkyl ether of polyalkylene glycol. A non-aqueous dispersion medium containing at least one compound selected from the group consisting of

  By using the non-aqueous dispersion medium, it is easy to adjust the viscosity when forming the metal oxide semiconductor film, and it becomes difficult to form a film by sagging or flowing, and the photoelectric conversion efficiency due to cracks. It is possible to prevent the lowering and peeling of the semiconductor film from occurring. In a water-based semiconductor film-forming coating agent that has been mainly used conventionally, polyethylene glycol having an average molecular weight of 20000 is often added as a thickener, but it is difficult to adjust the addition amount to obtain a preferable viscosity. Moreover, when the average molecular weight of polyethylene glycol is 200 to 4000, the increase in viscosity due to the addition of polyethylene glycol is not observed, and the expected thickening effect cannot be obtained. In contrast, in the non-aqueous dispersion medium, the viscosity can be easily adjusted by integrating the thickener and the dispersion medium.

  Further, by using the non-aqueous dispersion medium, the dispersion medium is less likely to evaporate than the conventional aqueous dispersion medium, so that the problem that the dispersion medium evaporates during storage or during coating or printing can be overcome. it can. That is, for example, titanium dioxide paste using an aqueous dispersion medium obtained by kneading a metal oxide semiconductor powder, a thickener, a surfactant, etc. in an aqueous solution has poor storage stability and film-forming properties, and sinters. There are drawbacks such as cracks and the film being easily peeled off. This is due to evaporation of the dispersion medium during storage and during application or printing. In particular, when the dispersion medium evaporates during application or printing, the appropriate viscosity of the applied or printed semiconductor forming coating agent cannot be maintained. Thereby, a crack arises at the time of sintering, a semiconductor film peels off, and film forming property worsens. By using the non-aqueous dispersion medium, such a problem is solved, and the storage stability and film forming property of the coating agent for forming a semiconductor film are improved.

  In addition, since an appropriate viscosity can be maintained, the semiconductor film-forming coating agent using the non-aqueous dispersion medium can be suitably used for screen printing. Screen printing is a coating method suitable for industrialization and practical application because of its high mass productivity and excellent adaptability to fine patterns and irregular patterns.

  Furthermore, by using such a non-aqueous dispersion medium, the dispersion medium that does not volatilize during heating or sintering is volatilized, so that a semiconductor film with improved porosity can be obtained. Thereby, since the irradiation area of the sunlight per unit mass of the metal oxide semiconductor is also increased, the photoelectric conversion efficiency of the solar cell using the semiconductor film can be improved.

  Examples of the alkylene glycol include ethylene glycol and propylene glycol. Examples of the polyalkylene glycol include diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, and polypropylene glycol. Examples of the alkyl ether include monomethyl ether, monoethyl ether, monopropyl ether, and the like. Among these, it is more preferable to use polyethylene glycol.

  Further, when the total dispersion medium is 100% by mass, the ratio of at least one compound selected from the group of the above compounds is preferably 10% by mass or more, and more preferably 30% by mass or more. More preferably, it is more preferably 40% by mass or more. Thereby, adjustment of the viscosity of the coating agent for forming a semiconductor film is facilitated. Therefore, the dispersion medium containing at least one compound selected from the group of the above compounds may contain components other than the above compounds. Here, said other component means all components other than the said compound in the dispersion medium containing the at least 1 sort (s) of compound chosen from the group of the said compound, and contains a solvent and the dispersion aid mentioned later. The solvent is preferably a non-aqueous solvent, and specific examples include ethanol, propanol, and ethyl acetate. Moreover, this solvent may be used independently and may be used in combination of 2 or more type. Moreover, what remove | eliminated the said solvent by heating etc. is good also as a coating agent for semiconductor film formation.

  As the polymer such as the polyalkylene glycol and the alkyl ether of the polyalkylene glycol, various polymers can be used from a low molecular weight polymer to a high molecular weight polymer depending on the desired viscosity. Specifically, for example, the average molecular weight of the polyalkylene glycol is preferably 106 to 400000, and more preferably 200 to 20000. Further, polymers having different average molecular weights may be used in combination. Further, a powdery polymer having a high molecular weight and a liquid polymer may be used in combination. The powdered polymer can be used after being dissolved in an appropriate organic solvent.

The dispersion medium may further contain a chelating agent, a particle aggregation inhibitor, a stabilizer, a thickener, zirconium oxide (ZrO ₂ ), an acid, a surfactant, and the like as a dispersion aid.
<Method for forming semiconductor film>
A method for forming a semiconductor film on a substrate using the semiconductor film-forming coating agent is not particularly limited, and a conventionally known method can be used. Specifically, for example, a coating method for coating the substrate film forming coating agent on a substrate, a printing method for printing, a sol-gel method, and the like can be given. Among these, it is preferable to use a coating method or a printing method. This is advantageous in terms of mass production of photoelectrodes and substrate flexibility.

  Examples of coating methods include roll method, dipping method, air knife method, blade method, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, knife coater method, doctor blade method, shower And various coating methods.

  As the printing method, for example, various printing methods such as a relief printing method, an offset printing method, a gravure printing method, an intaglio printing method, a rubber plate printing method, a screen printing method and the like can be used. Among the above printing methods, it is preferable to use a screen printing method particularly suitable for mass production.

  The metal oxide semiconductor film formed on the transparent conductive substrate by the above method may be any film that can maintain the shape of the metal oxide semiconductor film with respect to the charge transfer layer. Therefore, the metal oxide semiconductor film formed on the transparent conductive substrate may be dried and used as it is, or may be heated. Moreover, it is more preferable to sinter among heating. Here, the term “sintering” means that the metal oxide semiconductor film is heat-treated at a temperature equal to or lower than the melting point, thereby causing bonding between the metal oxide semiconductor particles. By sintering, bonding between the metal oxide semiconductor particles and between the transparent conductive substrate and the metal oxide semiconductor particles occurs, so that it is possible to enhance the adhesion and increase the film strength. . Further, the porosity of the metal oxide semiconductor film can be improved by volatilizing the nonvolatile component of the dispersion medium.

  The heating or sintering temperature is preferably 100 to 700 ° C, more preferably 180 to 550 ° C, and further preferably 450 to 500 ° C. The heating or sintering time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 1 hour.

(4) Solar cell The solar cell according to the present invention includes the photoelectrode, a counter electrode, and a charge transfer layer in contact with the photoelectrode and the counter electrode. Excited electrons generated by irradiating the photoelectrode with light are injected into the metal oxide semiconductor layer, move in the photoelectrode, and move to the counter electrode through an external circuit. The electrons that have moved to the counter electrode are carried by the mediator or the like of the charge transfer layer and return to the photoelectrode. In this way, light energy is converted into electrical energy.

<Counter electrode>
The counter electrode is not particularly limited as long as it is used as an electrode. Specifically, for example, a layer obtained by depositing or sputtering a layer of carbon, platinum or the like on a conductive substrate having a conductive layer formed on the substrate, or after applying chloroplatinic acid and then thermally decomposing it into a platinum layer. A conductive glass substrate on which platinum is sputtered is more preferable.

<Charge transfer layer>
Furthermore, as the charge transfer layer, for example, an electrolyte such as an electrolytic solution containing an oxidizing species and a reducing species, an electrolyte solution containing an oxidizing species and a reducing species gelled with a polymer matrix, a conductive polymer, p And a hole transport layer made of a type semiconductor.

  Further, the oxidizing species and reducing species are not particularly limited, but it is more preferable to use lithium iodide or potassium iodide and iodine.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to this.

  In addition, the measurement evaluation method in each Example and a comparative example is as follows.

1) Fourier transform infrared absorption spectrum (FT-IR) measurement The FT-IR measurement uses Bruker IFS113V type and Hitachi 260-50 type Fourier transform infrared spectrophotometer, and the resolution is 4 cm- ¹ . It was measured. The measurement sample was mixed with KBr in a mortar to form a powder and then pelletized with a tablet molding machine.

2) XPS analysis The XPS analysis uses AXIS-Ultra from Kratos, excitation X-ray source: monochrome A1-Kα ray (1486.6 eV), photoelectron detection angle 90 ° (from sample surface), detection depth: <10 nm , Charge neutralization gun: It was performed under the conditions of use (irradiation with low-speed electrons).

3) Temperature-programmed desorption (TPD) measurement TPD measurement uses a temperature-programmed desorption gas analyzer (TPD, Model Thermo Plus TPD Type V), and a powder sample is placed in a Pt cell (diameter 6 mm, high 2.5 mm), measurement temperature range: 40 to 900 ° C., heating rate: 10 ° C./min, measurement mode TIC (scan): m / e = 1 to 100, measurement start vacuum: ≦ 2. The ^measurement was performed under the condition of 0 × 10 ⁻⁶ Pa.

4) Specific surface area and pore distribution The specific surface area of the titanium dioxide semiconductor film was measured by the BET method (gas adsorption method) using a fully automatic gas adsorption measuring apparatus (Autosoap-1, manufactured by Yuasa Ionics). The specific surface area was calculated by the BET single point method and the multipoint method, and the pore distribution was calculated by the BJH method.

5) Adsorption amount of sensitizing dye The electrode on which the sensitizing dye was adsorbed was immersed in an alkaline solution of ethanol for 2 hours to decolorize the sensitizing dye. The ultraviolet-visible spectrum of the alkaline solution of ethanol was measured using an ultraviolet-visible spectrophotometer (U-3310, manufactured by Hitachi, Ltd.). Next, the adsorption amount was converted from the absorption intensity based on the calibration curve of the sensitizing dye.

6) Current / voltage characteristics Using a potentiostat (Potentiostat / Galvanostat 2090, manufactured by Toho Giken), the photocurrent density Jsc (mA · cm ⁻² ) and the open-circuit voltage Voc (mV) of the solar cell were measured, and from the curve The fill factor FF and the photoelectric conversion efficiency (%) were determined.

[Example 1]
Nitrogen (3000 wtppm) was obtained by heat-treating commercially available anatase-type titanium dioxide particles (Ishihara Sangyo, average particle size 7 nm, specific surface area 315 m ² / g) in a gas atmosphere containing nitrogen and carbon. And carbon (150 wtppm) -doped anatase-type titanium dioxide particles (primary spherical particles having an average minor axis of about 10 nm and an average major axis of about 30 nm) were synthesized.

For the titanium dioxide particles doped with nitrogen and carbon, a Fourier transform infrared absorption spectrum by the KBr method was measured. The measured spectrum diagrams are shown in FIGS. As shown in FIGS. 4 and 5, it was confirmed that an absorption peak at a wavenumber of 580 cm ^-1 and 340 cm ^-1. The absorption peak is based on doped carbon and nitrogen.

Further, XPS analysis was performed on the titanium dioxide particles doped with nitrogen and carbon. The obtained measurement results are shown in FIG. In FIG. 2, the peak with the lowest binding energy represents the concentration of nitrogen in the Ti—N—Ti bond state. The peak at the center represents the concentration of nitrogen in the Ti—N—O bond state. The peak with the highest binding energy represents the concentration of nitrogen adsorbed on the surface of the titanium dioxide fine particles in the form of NH _x , and does not have a strong bond with Ti. . As is clear from FIG. 2, in the titanium dioxide fine particles doped with nitrogen and carbon, many Ti—N—Ti bonding states in which oxygen atoms of titanium dioxide are replaced with nitrogen are detected. A Ti—N—O bond state, which is in the gap, is also detected.

Next, with respect to the titanium dioxide particles doped with nitrogen and carbon, spectra of various desorbed gases by a temperature programmed desorption (TPD) were measured. 6 to 9 show spectra of various desorption gases obtained by the temperature programmed desorption method. What is indicated by a solid line is that of the titanium dioxide particles doped with nitrogen and carbon. What is indicated by a broken line is that of titanium dioxide particles doped only with nitrogen. FIG. 6 shows the desorbed gas, N ₂ in FIG. 6, H ₂ in FIG. 7, CO ₂ in FIG. 8, and m / e = 68 in FIG. As shown in FIG. 6 to FIG. 9, the desorption peak is observed at 700 ° C. or higher for all of the components where N ₂ , H ₂ , CO ₂ and m / e = 68.

Thus, the desorption peak observed in the high temperature region of 700 ° C. or higher is the release of nitrogen, hydrogen, and carbon that form part of the structure of titanium dioxide particles doped with two or more elements. This is presumed to be due to this. Thus, in the titanium dioxide fine particles doped with two or more elements used in the photovoltaic cell of the present invention, the doped nitrogen, hydrogen, and carbon have a stronger bonding state with titanium dioxide. ing. In addition, although peaks are observed even in a low temperature region of less than 700 ° C., these are the ones in which gases caused by NH ₃ , H ₂ O, etc. adsorbed on the surface of the titanium dioxide fine particles are released, It is not due to nitrogen, hydrogen, or carbon contributing to a general lattice structure. FIG. 9 shows the spectrum of the component with m / e = 68 as described above, but the specific substance name is still unknown. However, as is apparent from FIG. 9, the desorption peak temperature of this substance is about 370 ° C. in the case of titanium dioxide fine particles doped only with nitrogen, whereas that of titanium dioxide doped with nitrogen and carbon. The particles show 700 ° C. or higher. Therefore, the fact that this component of m / e = 68 is firmly bonded to titanium dioxide is considered to be a factor that shows excellent thermal stability of titanium dioxide doped with two or more elements. .

  To 3 g of anatase-type titanium dioxide powder doped with nitrogen and carbon, ethylene glycol (5.01 g) with an average molecular weight of 600, ethanol (7.5 mL), and zirconium dioxide (30 g) are added and shaken for 4 hours with a paint shaker. Then, ethanol was removed by heating to prepare a paste as a coating agent for forming a titanium dioxide film.

Next, by using this paste, a semiconductor film having a film thickness of 12 μm and an area of 0.2 cm ² is formed on the conductive layer of the glass substrate on which SnO ₂ doped with fluorine is formed as a conductive layer by a screen printing method. Was heated gradually to 450 ° C. in an electric furnace and sintered at this temperature for 30 minutes. The obtained semiconductor film had a pore distribution of 10 to 80 nm (diameter), a specific surface area of 110 m ² / g, and a semiconductor film with improved porosity was obtained.

Subsequently, a ruthenium bipyridine complex (N719, manufactured by Solaronix) was dissolved in methanol so as to be 3 × 10 ⁻⁴ mol / L. The obtained semiconductor film was immersed in this solution and allowed to stand at room temperature for 12 hours. Thereafter, the semiconductor film adsorbed with the ruthenium bipyridine complex was washed with methanol and dried to produce the photoelectrode of the present invention. The adsorption amount of the ruthenium bipyridine complex was 7.8 × 10 ⁻⁸ mol / cm ² , an increase of 25% compared to the case of using titanium dioxide before improvement.

  A platinum film was formed by sputtering on a glass substrate on which another conductive film was provided to produce a counter electrode. An electrolyte solution composed of methoxyacetonitrile containing 0.1 mol / L LiI and 0.1 mol / L iodine was injected between the photoelectrode and the counter electrode to manufacture a solar cell A.

The manufactured solar cell A is irradiated with simulated sunlight having an intensity of 100 mW / cm ² (wavelength distribution AM1.5) using a xenon lamp (ATAGO BUSSAN Co., Ltd., XC-300), and the current density-voltage characteristics. Was measured and battery performance was evaluated. The results are shown in FIG.

[Comparative Example 1]
Polyethylene glycol (5.01 g) having an average molecular weight of 600, ethanol (7.5 mL), zirconium dioxide (30 g) is added to 3 g of commercially available anatase-type titanium dioxide powder (P25, Nippon Aerosil, average particle size of about 25 nm), After shaking and dispersing for 4 hours with a paint shaker, ethanol was removed by heating to prepare a paste as a coating agent for forming a semiconductor film. Next, using this paste, a solar cell B was produced in the same manner as in Example 1.

  The manufactured solar battery B was evaluated for battery performance in the same manner as in Example 1. The results are shown in FIG.

[Comparative Example 2]
A solar cell C was produced in the same manner as in Example 1 using a commercially available anatase-type titanium dioxide paste (Solarnix, Ti-Nanoxide D).

  The produced solar cell C was evaluated for battery performance in the same manner as in Example 1. The results are shown in FIG.

図１は、光電流密度−電圧曲線を示すグラフであり、縦軸は光電流密度（ｍＡ／ｃｍ^２）、横軸は電圧（ｍＶ）を示す。また、表１には、製造された太陽電池の開放電圧Ｖｏｃ（ｍＶ）、光電流密度Ｊｓｃ（ｍＡ・ｃｍ^−２）、フィルファクターＦＦ、光電変換効率（％）を示す。

FIG. 1 is a graph showing a photocurrent density-voltage curve, in which the vertical axis represents photocurrent density (mA / cm ² ) and the horizontal axis represents voltage (mV). Table 1 shows the open circuit voltage Voc (mV), photocurrent density Jsc (mA · cm ⁻² ), fill factor FF, and photoelectric conversion efficiency (%) of the manufactured solar cell.

  From FIG. 1 and Table 1, in solar cell A manufactured using a paste in which titanium dioxide doped with nitrogen and carbon is dispersed using polyethylene glycol as a dispersion medium, compared with solar cell B and solar cell C, It can be seen that the photocurrent density and photoelectric conversion efficiency are dramatically improved. Compared with the case where a commercially available anatase type titanium paste is used, the photoelectric conversion efficiency is improved by 35%.

  As described above, the metal oxide semiconductor of the metal oxide semiconductor layer included in the photoelectrode according to the present invention is doped with at least two elements selected from the group consisting of carbon, hydrogen, nitrogen, and sulfur. Therefore, the band gap is controlled. Therefore, the electron injection, electron, and charge transport characteristics of the dye-sensitized solar cell using the photoelectrode are improved, and the photoelectric conversion efficiency of the solar cell can be improved.

  In order to improve the photoelectric conversion efficiency even a little, dye-sensitized solar cells have been developed every day by various researches on electrodes, dyes, etc. In addition to these techniques, the photoelectrode according to the present invention is used. If used, further significant improvement in photoelectric conversion efficiency can be expected.

  Therefore, the road to practical use of dye-sensitized solar cells is opened. Utilizing the characteristics of the dye-sensitized solar cell, there are various industrial uses as follows. For example, various applications such as a small battery for indoor use, a battery for outdoor power generation, a transparent battery for window glass and walls, a battery for toys, and a battery for remote power supply are conceivable. Furthermore, the solar cell can be finished in a film form, multicolored using various natural pigments, and new style solar cells can be produced. For this reason, dye-sensitized solar cells are extremely promising as next generation solar power generators instead of expensive energy consuming silicon solar cells.

It is a graph which shows the photocurrent density-voltage curve of the solar cell manufactured in the Example and the comparative example. It is a graph which shows the XPS analysis result about the combined state of doped nitrogen about the titanium dioxide particle doped with nitrogen and carbon. It is a graph which shows the XPS analysis result about the combined state of doped nitrogen about the titanium dioxide particle doped only with nitrogen. It is a figure which shows the infrared absorption spectrum about the titanium dioxide particle by which nitrogen and carbon were doped. It is a figure which shows the infrared absorption spectrum about the titanium dioxide particle by which nitrogen and carbon were doped. Nitrogen and carbon is a diagram showing the spectrum of N ₂ by Atsushi Nobori spectroscopy of the doped titanium dioxide particles (TPD). Nitrogen and carbon is a diagram showing the spectrum of H ₂ by Atsushi Nobori spectroscopy of the doped titanium dioxide particles (TPD). Nitrogen and carbon is a diagram showing the spectrum of the CO ₂ by Atsushi Nobori spectroscopy of the doped titanium dioxide particles (TPD). It is a figure which shows the spectrum of the component which is ratio m / e = 68 of the mass number m and the charge number e of an ion by the temperature programmed desorption method (TPD) of the titanium dioxide particle doped with nitrogen and carbon.

Claims (7)

A transparent conductive substrate having at least one surface conductive;
A photoelectrode including a metal oxide semiconductor layer containing metal oxide semiconductor particles formed on the conductive surface of the transparent conductive substrate,
The metal oxide semiconductor is titanium dioxide,
The metal oxide semiconductor is doped with carbon and nitrogen ,
Nitrogen is doped at a concentration of 700 wtppm or more and 10000 wtppm or less,
A photoelectrode, wherein carbon is doped at a concentration of 50 wtppm or more and 1500 wtppm or less . Nitrogen is doped into the metal oxide semiconductor is eliminated as a nitrogen molecule by heating, photoelectrode according to claim 1, the nitrogen molecule desorption peak temperature, characterized in der Rukoto than 700 ° C.. The photoelectrode according to claim 1 or 2, wherein a sensitizing dye is adsorbed on the metal oxide semiconductor layer . A solar cell comprising the photoelectrode according to any one of claims 1 to 3 , a counter electrode, and a charge transfer layer in contact with the photoelectrode and the counter electrode . Prepare a coating agent for forming a semiconductor film using metal oxide semiconductor particles,
A semiconductor film-forming coating agent is applied or printed on a conductive surface of a transparent conductive substrate having at least one surface of a conductive material to form a semiconductor film and heated to 100 ° C. or higher. In the manufacturing method,
Titanium dioxide doped with carbon and nitrogen as a metal oxide semiconductor, nitrogen is doped at a concentration of 700 wtppm or more and 10,000 wtppm or less, and carbon is doped at a concentration of 50 wtppm or more and 1500 wtppm or less A method for producing a photoelectrode, characterized by using titanium dioxide . 6. The photoelectrode manufacturing method according to claim 5 , wherein nitrogen doped in the metal oxide semiconductor is desorbed as nitrogen molecules when the temperature rises, and the nitrogen molecule desorption peak temperature is 700 ° C. or higher. Way . Furthermore, a sensitizing dye is made to adsorb | suck to the obtained said semiconductor film, The manufacturing method of the photoelectrode of Claim 5 or 6 characterized by the above-mentioned .

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