JP2007070136A - Titania nano-rod, its manufacture method, and dye sensitizing solar battery using this titania nano-rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide titania in an anatase phase giving a porous titania layer with higher electron transport efficiency than ever before, its manufacture method and a solar battery using this titania. <P>SOLUTION: This manufacture method comprises a step to obtain titania sol by reacting an organotitanium compound with an aqueous solution containing a block copolymer having a hydrophilic block and a hydrophobic block and an organic amine or ammonia, and a step to produce a nano-rod of titania by hydrothermally reacting the titania sol. Thereby, a highly crystalline titania nano-rod having X-ray diffraction intensity ratio (004)/(200) at (004) plane to (200) plane in Miller index expression of 0.85-1.0 is obtained. This titania nano-rod exhibits high electron transport efficiency, thereby, a dye sensitizing solar battery with high photoelectric conversion ratio can be manufactured by using this. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a highly crystalline titania nanorod, a method for producing the same, and a dye-sensitized solar cell with high power generation (photoelectric conversion) efficiency using the same.

A dye-sensitized solar cell using porous titania (TiO ₂ ) as an electrode has low cost and little environmental impact, and is more efficient than a solar cell using silicon. Has also attracted interest and has been widely researched and developed.

As shown in the schematic diagram of FIG. 1, a conventional dye-sensitized solar cell includes a transparent electrode 101, a porous layer of titania 104 having a sensitizing dye 103 adsorbed on the surface, a counter electrode 102, a transparent electrode 101, The liquid electrolyte 105 sealed between the counter electrodes 102 is a basic component. The sensitizing dye 103 functions to absorb light and inject electrons into the conduction band of the titania 104. It is known that the titania 104 functions as a semiconductor that transports injected electrons to the transparent electrode 101, and anatase titania is suitable. In addition, an aqueous solution containing an I ⁻ / I ₃ ^— redox pair is used for the liquid electrolyte 105.

When the dye-sensitized solar cell is irradiated with sunlight, electrons in the sensitizing dye 103 are excited. The excited electrons are injected from the titania 104 to the transparent electrode 101 and move to the counter electrode 102 via the external load 106. In the counter electrode 102, I ₃ ⁻ is given an electron and reduced to 3I ⁻ . When this 3I ⁻ diffuses in the liquid electrolyte 105 and reaches the sensitizing dye 103, electrons are given, and it is oxidized and returns to I ₃ ⁻ . By repeating this cycle, power generation is performed.

Various studies for increasing the photoelectric conversion efficiency have been made with the aim of putting the dye-sensitized solar cell to practical use. As can be seen from the description of the configuration of the dye-sensitized solar cell, the sensitizing dye and porous titania are the main elements for achieving high photoelectric conversion efficiency. For this reason, conventionally changing the particle size and morphology of titania (Patent Document 1), optimizing the manufacturing method and structure of the porous titania layer (Non-Patent Document 1), and developing a new sensitizer (Non-Patent Document 1) Reference 2), suppression of charge recombination (Non-Patent Document 3), improvement of free energy difference at each interface such as the interface between titania and a sensitizing dye (Non-Patent Document 4) have been studied.
JP 2003-34531 A (paragraphs 0054-0058) M.M. Gomez et al., Sol. Energy Mater. Sol. Cells, 64, p385- (2000) S. S. Ferrere et al. Am. Chem. Soc. 120, p843-, (1998) S. Y. S. Y. Huang et al. Phys. Chem. , B101, p2576-, (1997) S. Y. S. Y. Huang et al. Phys. Chem., B101, p8141-, (1997)

By the way, the currently known porous titania membrane electrode is formed by dispersing spherical nanoparticles in a colloidal shape and using a doctor blade. The use of fine titania nanoparticles is advantageous in increasing the surface area, but the number of contact points between the titania nanoparticles increases, resulting in an increase in the electrical resistance of the porous titania layer and a decrease in electron transport efficiency. There is a problem that conversion efficiency is impaired.

  In view of the above problems, an object of the present invention is to provide a highly crystalline titania nanorod having a higher electron transport efficiency than the conventional one, a method for producing the same, and a solar cell using the titania nanorod.

  The present inventors examined the structure of titania nanorods that can obtain high electron transport efficiency and that can increase the photoelectric conversion rate of the dye-sensitized solar cell, focusing on the crystallinity of titania nanorods. As a result, it was found that titania nanorods synthesized under specific conditions have higher crystallinity than those conventionally known, and dye-sensitized solar cells using the same show high photoelectric conversion efficiency, leading to the present invention. .

  The anatase phase titania nanorod according to the present invention has an X-ray diffraction intensity ratio (004) / (200) between the (004) plane and the (200) plane in the Miller index display of 0.85 to 1.0, which is higher than conventional. It is characterized by high crystallinity, and exhibits high electron transport efficiency based on this high crystallinity.

  The method for producing a titania nanorod of anatase phase according to the present invention includes a step of obtaining a titania sol by reacting a block copolymer having a hydrophilic / hydrophobic block, an aqueous solution containing an organic amine or ammonia with a titanium organic compound, and a titania sol. And hydrothermal reaction to produce titania nanorods.

  By conducting a hydrothermal reaction of titania sol in the presence of a block copolymer having a hydrophilic / hydrophobic block, it is possible to produce titania nanorods having higher crystallinity and uniform shape than conventional ones. This is a minute isolated reaction field formed by a block copolymer having a hydrophilic / hydrophobic block in an aqueous solution, and the shape of the titania nanorod finally obtained as a result of growing into a titania nanorod by hydrothermal synthesis. Are considered to be controlled to the same.

  The dye-sensitized solar cell according to the present invention is characterized by using the anatase phase highly crystalline titania nanorod as an oxide semiconductor layer. In the dye-sensitized solar cell having such a configuration, the highly crystalline titania nanorod has high electron transport efficiency, and the contact point between the titania nanorods is smaller than that in the case of using nanoparticles, and the internal resistance of the battery is reduced. By reducing, high photoelectric conversion efficiency is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the highly crystalline titania nanorod of the anatase phase whose electron transport efficiency is higher than before, its manufacturing method, and the solar cell of the high photoelectric conversion efficiency using this titania nanorod are provided.

  Hereinafter, the production method and structure of the highly crystalline titania nanorod of anatase phase according to the present invention and the dye-sensitized solar cell using the titania nanorod will be described with reference to the drawings as appropriate.

<Manufacture of titania nanorods>
The titania nanorod of anatase phase according to the present invention comprises a block copolymer having a hydrophilic / hydrophobic block and an aqueous solution containing an organic amine or ammonia to obtain a titania sol by reacting with a titanium organic compound. It can produce | generate by making it heat-react. Further, a cationic surfactant can be further added to the aqueous solution containing the block copolymer and the organic amine or ammonia.

Titanium alkoxide and titanium acetate can be used as the starting titanium organic compound for producing the titania gel. Titanium alkoxide is represented by the general formula Ti (OH) (OR) ₃ or Ti (OR) ₄ (where R is a linear or branched alkyl group). As an example, titanium tetramethoxide, titanium tetraethoxide, titanium tetra (N-propoxide), titanium tetraisopropoxide, titanium tetra (n-butoxide), titanium tetraisobutoxide, titanium tetra (2-ethylhexoxide), titanium tetramethoxyethoxide, titanium methyltripropoxide It is done. Moreover, titanium (2-methacryloxy) ethyl acetoacetate triisopropoxide, titanium diisopropoxide diacetyl acetate, etc. can be mentioned as an example of titanium acetate.

Titanium tetraalkoxide can be suitably used for the titanium organic compound because it is easily available, and considering reactivity, titanium tetraalkoxide having an alkyl group having 1 to 6 carbon atoms, more preferably 3 to 4 carbon atoms. Can be suitably used.

  The block copolymer having a hydrophobic block and a hydrophilic block includes a binary block copolymer comprising a hydrophobic block and a hydrophilic block, or a ternary block copolymer comprising a hydrophilic-hydrophobic-hydrophilic block. Use a substance that can form a micelle-like reaction field in which an aqueous hydrophobic block is surrounded by a hydrophilic block in an aqueous solution and provides an isolated reaction field in which titania nanorods cannot be connected to each other. be able to. A copolymer having an oxygen atom capable of coordinating with a hydroxyl group of titania sol in the main chain or side chain of the hydrophobic block can be used.

  As an example of such a binary or ternary block copolymer, the hydrophobic block is polyoxypropylene, the hydrophilic block is polyoxyethylene, or the hydrophobic block is polymethyl methacrylate, poly (methacrylic acid 2- A block copolymer in which the water-soluble block is any of polyvinyl alcohol, polyacrylamide, polydimethylacrylamide, polyallylamine, or polyacrylic acid, which is any of (hydroxyethyl), polylactic acid, polylactone, or polylactam. Can do.

(Polyoxyethylene (PEO)) _x- (Polyoxypropylene (PPO)) _y- (Polyoxyethylene (PEO)) A ternary block copolymer having a structure of _z is preferably used because of its availability. be able to. In the above formula, x and z are 20 or more, preferably 100 or more, and y is 10 or more, preferably 50 or more.

  The concentration of such a binary or ternary block copolymer in the solution is 5 wt% or more and 40 wt% or less, preferably 5 wt% or more and 20 wt% or less. When the concentration of the binary or ternary block copolymer is 5 wt% or less, the reaction field in the hydrophobic atmosphere formed by the block copolymer having a parent / hydrophobic block cannot be stably formed. It is thought that it cannot be controlled. On the other hand, when the concentration of the binary or ternary block copolymer is 40 wt% or more, the reaction field in the hydrophobic atmosphere formed by the block copolymer having a parent / hydrophobic block is precisely constructed based on the phase separation. Therefore, the shape of the titania nanorod cannot be controlled.

  The production mechanism of titania nanorods is important to form a reaction field in a hydrophobic atmosphere formed by a block copolymer having a hydrophilic / hydrophobic block, and a periodic block constructed by a conventionally known block copolymer is constructed. This is different from the manufacturing method in which the structure is used as a mold and the shape of the mold is a titania shape.

  An organic amine forms a complex with an organic titanium compound to produce a titania nanorod precursor, and a water-soluble aliphatic amine or aliphatic diamine can be used. As such an organic amine, an aliphatic amine having an amine at the terminal or both terminals of a linear alkyl group having 1 to 5 carbon atoms, or an aliphatic diamine is preferably used. For example, ethylenediamine, propanediamine, tetramethylenediamine, Pentamethylenediamine diamine and the like can be suitably used.

  The cationic surfactant is preferably a halogenated quaternary ammonium salt containing a long chain alkyl group, and specifically, a halogenated 4 having a long chain alkyl group having 10 to 20 carbon atoms and three methyl groups. Secondary ammonium salts such as cetyltrimethylammonium bromide can be used. The cationic surfactant makes it possible to stabilize titanium ions in an aqueous solution and obtain highly crystalline titania nanorods.

  A titania sol is obtained by preparing an aqueous solution containing the cationic surfactant and / or organic amine described above and a block copolymer, and then adding and stirring a titanium organic compound such as titanium alkoxide. Can do. Thereafter, the titania sol can be hydrothermally reacted to obtain a target titania nanorod.

  The temperature of the hydrothermal reaction is in the range from the boiling point of water to the critical temperature (373K to 647K), and can be appropriately selected according to the reagent used in the reaction, such as the type of titanium alkoxide. Further, since the hydrothermal reaction is carried out at the saturated water vapor pressure of water at the hydrothermal reaction temperature, it is preferably carried out using a known pressure vessel such as an autoclave or a pressure glass vessel. What is necessary is just to select reaction time suitably according to the kind etc. of titanium alkoxide used for reaction, and it can carry out normally in the range of 10 minutes-several tens hours.

The thus obtained highly crystalline titania nanorod has a standard anatase with an X-ray diffraction intensity ratio (004) / (200) of (004) plane and (200) plane in the Miller index display of 1.0. It shows a value much higher than 0.57 of phase titania. Details will be described later.
When the obtained anatase phase titania nanorod is fired for use in a dye-sensitized solar cell, the transition to the rutile phase can be prevented if it is carried out at 700 ° C. or lower, preferably 600 ° C. or lower.

<Manufacture of dye-sensitized solar cells>
Next, a dye-sensitized solar cell using a highly crystalline titania nanorod will be described with reference to FIG.
The dye-sensitized solar cell 1 according to this embodiment includes a transparent electrode 2, a porous layer that is stacked on the transparent electrode 2, and includes an oxide semiconductor 3 that has a sensitizing dye 6 adsorbed on the surface thereof. The electrode 4 is configured to include a counter electrode 4 provided to face the transparent electrode 2 and an electrolyte solution 5 impregnated between the transparent electrode 2 and the counter electrode 4, and further regulates the distance between the transparent electrode 2 and the counter electrode 4. And a spacer 11 for forming a space to be impregnated with the electrolytic solution 5.

  And the closed circuit is formed by connecting the transparent electrode 2 and the counter electrode 4 to the external load 12, and it functions as a battery. In the present embodiment, as illustrated in FIG. 2, a case where a space filled with the electrolytic solution 5 is provided between the porous layer containing the oxide semiconductor 3 and the counter electrode 4 will be described as an example. . In the following description, a porous layer containing the oxide semiconductor 3 is referred to as an oxide semiconductor layer 7.

  The transparent electrode 2 transmits ultraviolet light or visible light incident light U, and is injected with electrons from the oxide semiconductor layer 7. The transparent electrode 2 has a film thickness on one surface of a transparent substrate 22 made of glass or plastic. Is formed by coating by a known method such as sputtering, ion plating, or screen printing.

  The conductive light transmission film 23 may be any material as long as it has electrical conductivity, transmits incident light U (ultraviolet light or visible light), and has excellent adhesion to the transparent base material 22, for example, ITO (indium-tin oxide). ), IZO (indium-zinc oxide), ZnO (zinc oxide), or the like. ITO is suitable because it is easily available and can be easily formed into a film.

The oxide semiconductor layer 7 according to this embodiment is formed by laminating a porous layer made of the oxide semiconductor 3 on the transparent electrode 2 as schematically shown in the partially enlarged view of FIG. The dye 6 is adsorbed. The oxide semiconductor 3 uses the highly crystalline titania nanorod of the anatase phase according to the present embodiment. Besides, for example, tin oxide (SnO ₂ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ). Indium oxide (In ₂ O ₃ ), Zirconium oxide (ZrO ₂ ), Lanthanum oxide (La ₂ O ₃ ), Tantalum oxide (Ta ₂ O ₅ ), Strontium titanate (SrTiO ₃ ), Barium titanate (BaTiO ₃ ) Other oxide semiconductors 3 can also be used in combination.

  In order to increase the photoelectric conversion efficiency of the dye-sensitized solar cell, it is preferable to use a mesoscopic oxide semiconductor layer 7 that exhibits a quantum size effect. That is, the porous oxide semiconductor layer 7 may be formed using nanorods having a diameter of 5 to 30 nm and a length of 50 to 300 nm, preferably a diameter of 10 to 20 nm and a length of 100 to 200 nm. preferable. In particular, when a highly crystalline titania nanorod having an anatase phase is applied to the oxide semiconductor layer 7, a long and continuous conduction band is formed in the titania crystal, resulting in high electron transport efficiency. As a result, high photoelectric conversion efficiency is obtained. Therefore, it is excellent as a material for forming the oxide semiconductor layer 7.

  Further, by making the oxide semiconductor layer 7 porous, injected electrons can be guided to the transparent electrode 2. Such an oxide semiconductor layer 7 is formed into a slurry by dispersing titania in water or an organic solvent, and a thin film is formed on the transparent electrode 2 by a known method such as a spin coating method, a cast coating method or a doctor blade method. Then, it can be formed by firing or drying by the above-described method.

In the sensitizing dye 6, the absorption wavelength region extends to a long wavelength side so as to cover the visible light region, and the energy when photoexcited is about 0.2 eV or more higher than the level of the conduction band of the oxide semiconductor layer 7, Further, it is preferable to use a dye that can quickly receive electrons from I ⁻ in the electrolytic solution 5 before the electrons injected into the oxide semiconductor layer 7 recombine with the sensitizing dye 6.

As such a sensitizing dye 6, a metal complex such as ruthenium complex, phthalocyanine, cyanine, merocyanine, porphyrin, chlorophyll, pyrene, methylene blue, thionine, xanthene, coumarin, rhodamine, or an organic dye and derivatives thereof can be used. . In the case of titania in the anatase phase, a ruthenium complex represented by the formula (1) can be preferably used. In Formula (1), —COOH may be substituted with —COOC ₂ H ₅ .
Formula (1)

The electrolytic solution 5 may repeat a cycle in which electrons are injected to the sensitizing dye 6 in which holes are generated by injecting electrons into the oxide semiconductor layer 7 to be oxidized, and are received and reduced by the counter electrode 4. Any solution containing a possible redox pair may be used, and a redox couple of I ⁻ / I ₃ ⁻ can be used. Specific examples include combinations of metal iodides such as lithium iodide (LiI), sodium iodide (NaI), potassium iodide (KI), and calcium iodide (CaI ₂ ) with iodine. The solvent may be water or an organic solvent.

  The counter electrode 4 is formed by coating one surface of the fixed plate 42 with a conductive film 41 made of platinum or the like. A transparent electrode 2 is provided opposite to the counter electrode 4, and a spacer 11 is formed between the counter electrode 4 and the transparent electrode 2 to regulate a space between the counter electrode 4 and the transparent electrode 2 and impregnate the electrolyte 5. Is inserted. The material of the fixing plate 42 and the spacer 11 may be any material that is chemically stable with respect to the electrolytic solution 5, for example, a thermoplastic resin such as polyester or polyolefin, a thermosetting resin such as silicone or polyimide, or glass. Etc. can be used.

When the electrolytic solution 5 is impregnated in the space formed by the counter electrode 4, the transparent electrode 2, and the spacer 11, the space can be reduced by using a capillary phenomenon or using a vacuum pump. At this time, the oxide semiconductor layer 7 composed of the oxide semiconductor 3 is also immersed in the electrolytic solution 5, the sensitizing dye 6 adsorbed on the surface of the oxide semiconductor 3, and the I dissolved in the electrolytic solution 5. ^The redox couple such as ⁻ / I ₃ ^— can be brought into contact. Thereby, electrons are injected from the sensitizing dye 6 excited by sunlight into the oxide semiconductor 3, and the sensitizing dye 6 and the oxide semiconductor 3 ( A closed circuit that returns to the redox couple through the oxide semiconductor layer 7), the transparent electrode 2, the external load 12, and the counter electrode 4 is formed, and functions as the dye-sensitized solar cell 1.

  In this embodiment, since the highly crystalline titania nanorod of anatase phase is used for the oxide semiconductor 3, the electron transport efficiency of the oxide semiconductor layer 7 composed of the oxide semiconductor 3 in this closed circuit is increased. A high photoelectric conversion efficiency is achieved.

By the way, in order to efficiently perform photoelectric conversion in the above-mentioned closed circuit, for example, when using a redox couple of I ⁻ / I ₃ ⁻ , electrons once transferred from I ⁻ to the sensitizing dye 6 are converted into I ₃ ⁻ and It must be prevented from recombining and not contributing to photoelectric conversion. For this purpose, I ₃ ⁻ generated by releasing electrons from I ⁻ can reach the counter electrode 4 without being prevented from diffusing in the pores of the oxide semiconductor layer 7 and receive electrons. It is necessary to.

  Therefore, as a modification of the present embodiment, as schematically shown in FIG. 4, a layer of oxide semiconductor nanoparticles having a particle diameter of 1 to 5 nm (first porous layer 31) and a diameter of 5 on the transparent electrode 2. A layer (second porous layer 32) containing anatase-phase highly crystalline titania nanorods of ~ 30 nm, preferably 10-20 nm in diameter, oxide semiconductor particles having a particle diameter of more than 30 nm or nanorods of a diameter of more than 30 nm It can be set as the oxide semiconductor layer 7 laminated | stacked in order of (3rd porous layer 33). Here, it is preferable that the layer thickness of the first porous layer 31 is 0.5 to 5 μm, and the sum of the layer thicknesses of the second porous layer 32 and the third porous layer 33 is 3 to 50 μm. In addition, the thickness of the oxide semiconductor layer 7 is preferably 8 μm or more.

In FIG. 4, since the particle diameter of the nanoparticles constituting the first porous layer 31 is as extremely fine as 1 to 5 nm, a large specific surface area can be obtained even though the layer thickness is thin. That is, a large amount of the sensitizing dye 6 can be adsorbed on the first porous layer 31. Thereby, the absorptance of the incident light U in the 1st porous layer 31 becomes high, and the photoelectric conversion efficiency of the dye-sensitized solar cell 1 can be improved.
Further, in consideration of the small particle size of the nanoparticles constituting the first porous layer 31, the layer thickness is relatively reduced to 0.5 to 5 μm, so that the electrolysis in the first porous layer 31 is performed. It is effectively prevented that electrons are lost due to recombination due to the diffusion failure of the redox couple in the liquid 5.

  The incident light U that has not been absorbed by the first porous layer 31 reaches the second porous layer 32 and is absorbed by the sensitizing dye 6 adsorbed on the surface thereof. Can be high. Furthermore, since the second porous layer 32 contains highly crystalline titania nanorods having a diameter of 5 to 30 nm, the movement of electrons injected from the sensitizing dye is fast. In addition, since it cannot be as densely packed as in the case of nanoparticles having a particle size of 1 to 5 nm, there is a space necessary for the redox couple to diffuse into the porous oxide semiconductor layer 7. Since it is ensured and the diffusion of the redox couple is not hindered, the electrons once injected from the sensitizing dye 6 into the oxide semiconductor 7 are not lost by recombination with the redox couple.

  As described above, in the second porous layer 32, in addition to the effect of increasing the utilization efficiency of the incident light U and the effect of preventing recombination of electrons, the highly crystalline titania nanorods in the anatase phase exhibit high electron transport efficiency. Thus, high photoelectric conversion efficiency can be obtained.

  On the 2nd porous layer 32, the 3rd porous layer 33 comprised by the oxide semiconductor particle which a particle size exceeds 30 nm further, or the nanorod whose diameter exceeds 30 nm can be provided. The third porous layer 33 also has the effect of preventing recombination of electrons, like the second porous layer 32, but mainly increases the light utilization efficiency by reflecting and scattering the incident light U. Has an effect.

  By providing the first porous layer 31 to the third porous layer 33 in this way, it becomes possible to increase the utilization efficiency of the incident light U while ensuring the diffusion of the redox couple in the oxide semiconductor layer 7. The layer thickness of the oxide semiconductor layer 7 as a whole can be reduced. As a result, the distance between the transparent electrode 2 and the counter electrode 4 can be reduced, and the internal resistance of the dye-sensitized solar cell 1 is reduced, so that high photoelectric conversion efficiency can be obtained.

Here, the lower limit of the layer thickness of the first porous layer 31 is 0.5 μm because it is the minimum thickness that can be formed by one coating when the oxide semiconductor layer 7 is formed by stacking. . The upper limit of the thickness of the first porous layer 31 is 5 μm because of the redox couples I ₃ ⁻ and 3I ⁻ that move through the electrolytic solution 5 that has penetrated into the first porous layer 31. This is because the movement speed is extremely slow, and when the layer thickness exceeds 5 μm, electrons that do not contribute to photoelectric conversion due to recombination increase, and high photoelectric conversion efficiency cannot be obtained.

  The lower limit of the sum of the layer thicknesses of the second porous layer 32 and the third porous layer 33 is 3 μm because it is the minimum thickness that can be formed by the coating process. When the sum of the layer thicknesses of the second porous layer 32 and the third porous layer 33 exceeds the upper limit of 50 μm, the electrode interval between the transparent electrode 2 and the counter electrode 4 increases, and the internal resistance of the battery increases. As a result, high photoelectric conversion efficiency cannot be obtained.

Next, examples in which the effects of the present invention have been confirmed will be described. Note that the present invention is not limited to these examples.
In this example, anatase-phase highly crystalline titania nanorods (hereinafter referred to as titania nanorods) were synthesized by a hydrothermal reaction and then analyzed. Moreover, the dye-sensitized solar cell 1 was manufactured using the obtained titania nanorod, and battery characteristics, such as photoelectric conversion efficiency, were evaluated.

<Example 1: Synthesis of titania nanorods and evaluation of structure>
In this example, titania nanorods were synthesized using the following reagents. All reagents were reagent grade and used without purification.

Tetraisopropyl orthotitanate (hereinafter referred to as TIPT) was used as the titanium organic compound. Pluralonic F127 (hereinafter referred to as F127) manufactured by BASF was used as a block copolymer having a hydrophobic block and a hydrophilic block. F127 is a ternary block copolymer represented by (PEO) _x (PPO) _y (PEO) _z : x, z = 100 to 110, y = 50 to 70. Further, ethylenediamine (hereinafter referred to as EDA) was used as the organic amine, and cetyltrimethylammonium bromide (hereinafter referred to as CTAB) was used as the cationic surfactant.

  A 10 wt% aqueous solution of F127 was prepared, and CTAB was added thereto at 0.05 mol / L, followed by stirring at 35 ° C. until a transparent aqueous solution was obtained. After adding EDA to this aqueous solution so that it might become 0.2 mol / L, TIPT was added, stirring until it became 0.22 mol / L, and the white titania sol was obtained. The aqueous solution containing the titania sol is placed in a Teflon (registered trademark) container sealed in a stainless steel pressure-resistant container, subjected to a hydrothermal reaction at 160 ° C. for 12 hours, and the desired titania nanorod is suspended in white (Hereinafter, this suspension is referred to as slurry A).

  The obtained titania nanorods were separated by filtration, washed twice with distilled water and twice with ethanol, and then centrifuged to obtain white powder of titania nanorods obtained by scanning electron microscope (SEM) and transmission electron microscope (TEM). Samples for high-resolution electron microscope (HRTEM) and X-ray diffraction (XRD) analysis were used.

<Comparative Example 1: Titania nanorods not using a block copolymer>
For comparison, a white suspension of titania nanorods was produced in the same manner as in Example 1 except that F127 was not used (hereinafter, this white suspension is referred to as slurry B).

(Comparison of structures by SEM and TEM)
FIG. 5 shows the morphology of the titania nanorods of Example 1 and Comparative Example 1. 5A to 5C are a TEM photograph, an SEM photograph, and an HRTEM photograph of Example 1, respectively, and FIGS. 5D and 5E are a TEM photograph and an SEM photograph of Comparative Example 1, respectively. These photographs are taken before firing the titania nanorods.

  First, TEM photographs (FIGS. 5A and 5D) and SEM photographs (FIGS. 5B and 5E) of Example 1 and Comparative Example 1 are compared. In the titania nanorod of Example 1, rods with a uniform shape having a diameter of 20 to 30 nm and a length of 100 to 200 nm are dispersed, and no branched rods are found. On the other hand, in Comparative Example 1, the diameter of the rod is 20 to 30 nm, but there are many rods having a length of 500 to 600 nm, which are not dispersed alone, and are in a branched state or an associated state. It turns out that it is a rod.

  In the case where the hydrothermal reaction of the titania sol was carried out in the presence of F127 without using CTAB, the present inventors independently dispersed the titania nanorods with the same rod diameter and length as in Example 1. It was confirmed that These results indicate that the diameter and length of the nanorods can be controlled by a block copolymer having a hydrophobic block and a hydrophilic block, such as F127.

  FIG. 5C is an HRTEM photograph of one titania nanorod obtained in Example 1. Since clear lattice-like stripes are observed in this photograph, it can be seen that the titania nanorod has high crystallinity and has almost no defects such as fine twins. In FIG. 5C, the edge of the (101) plane of the anatase phase titania having a lattice interval of 0.354 nm is observed, and further, the crystal of the titania nanorod is observed to grow in the (001) direction.

The XRD analysis result of the titania nanorod of Example 1 and Comparative Example 1 is shown in FIG. The bar on the horizontal axis in FIG. 6 indicates the peak position of the standard sample of the anatase phase titania. In FIG. 6, the top is the XRD peak curve of Example 1, and the bottom is that of Comparative Example 1.
From the X-ray diffraction patterns of these samples, in Example 1, the crystal region grew along the c-axis. As a result, the intensity ratio (004) / (200) between the (004) plane and the (200) plane was Comparative Example 1. It was observed that it was larger than

  That is, the intensity ratio (004) / (200) between the (004) plane and the (200) plane in the Miller index display shows a large value of 1.0 in Example 1 compared to 0.84 in Comparative Example 1. Admitted. The intensity ratio (004) / (200) of the standard sample of anatase phase titania was 0.57. Thus, since the intensity ratio (004) / (200) shows a high value of 0.85 or more, it can be seen that the c-axis has grown.

Here, the intensity ratio (004) / (200) was measured as follows.
A standard sample holder is loaded with a powder sample and mounted on an X-ray diffractometer (Rigaku, Rigaku Goniometer PMG-A2, CN2155D2). X-ray irradiation conditions are CuK _α 35 kV, 15 mA, using a Rigaku wide-angle goniometer, scan speed The measurement was performed at 2 deg / min, scan step: 0.017 deg, and scan range: 4 to 130 deg.

  As described above, the length of the rod of Comparative Example 1 is longer than that of Example 1, but in spite of this, the strength ratio (004) / (200) is 0.84, which is lower than that of Example 1. It is considered that the titania nanorod of Comparative Example 1 contains a branched portion that is not rod-shaped or contains titania in an associated state (FIGS. 5D and 5E).

  From the above, it can be seen that by adding F127 to the titania sol and conducting a hydrothermal reaction, relatively short titania nanorods grow independently in a completely dispersed state. In addition, from this, in the wet chemical process such as hydrothermal reaction, the shape of the nanocrystal can be formed by using a ligand capable of coordinating with titania, for example, a polymer having oxygen in the main chain or side chain capable of coordinating with the hydroxyl group of titania. Can be controlled.

<Example 2: Oxide semiconductor layer using titania nanorods>
An oxide semiconductor layer 7 using the titania nanorod synthesized in Example 1 was manufactured, and its crystal structure was evaluated.

The oxide semiconductor layer 7 was manufactured as follows.
On the ITO transparent electrode 2 (manufactured by Geomat Co., sheet resistance of about 5Ω / □) formed with indium tin oxide on a glass substrate, the slurry A obtained in Example 1 was used with a mending tape as a support. It apply | coated by the doctor blade method. The transparent electrode coated with the titania nanorods was naturally dried in the atmosphere at room temperature, and then placed in an electric furnace heated to 450 ° C. and baked for 10 minutes.

  Subsequently, the operation of applying slurry A to the transparent electrode 2 on which the titania nanorods were fired by the doctor blade method and firing was repeated three times. The firing conditions were 450 ° C. for 10 minutes, and the final firing was performed at 450 ° C. for 40 minutes. In this manner, a porous oxide semiconductor layer 7 was formed on the transparent electrode 2.

<Comparative example 2>
As Comparative Example 2, a porous oxide semiconductor layer 7 was formed on the transparent electrode 2 by the same method as in Example 2, using the slurry B produced in Comparative Example 1 without using F127.

<Comparative Example 3>
As Comparative Example 3, the porous oxide semiconductor layer 7 was formed on the transparent electrode 2 using P25 (hereinafter referred to as P25) manufactured by Nippon Aerosil, which is a commercially available titania nanoparticle. In this comparative example, using a slurry C in which 2 g of P25 was dispersed in 30 ml of a 40 wt% polyethylene glycol aqueous solution, an ITO transparent electrode 2 (made by Geomat Co., sheet resistance of about sheet resistance) formed of indium tin oxide on a glass substrate was used. 5Ω / □) was applied by the doctor blade method in the same manner as in Example 2, and then fired at 450 ° C. to form the oxide semiconductor layer 7.

(Structure of oxide semiconductor layer)
Each oxide semiconductor layer 7 after firing was observed with an optical microscope. In the case of the oxide semiconductor layer 7 of Example 2, a thin film without cracks was observed on the surface, and it was confirmed that the adhesiveness with the transparent electrode 2 was excellent. On the other hand, in the case of Comparative Example 2 and Comparative Example 3, it was observed that the thin film of the oxide semiconductor layer 7 was partially peeled from the transparent electrode 2 due to surface cracks.

  Although the copolymer (F127) contained in the slurry A is expected to function as a binder for titania nanorods, surface cracks were observed in Comparative Example 3 using the slurry C containing polymer (polyethylene glycol). Thus, it can be seen that F127, which is a block copolymer, has a particularly remarkable effect in forming the oxide semiconductor layer 7 having excellent adhesion to the transparent electrode 2.

  SEM photographs of the oxide semiconductor layer 7 after firing are shown in FIG. 7A (Example 2) and FIG. 7B (Comparative Example 2). The titania nanorods manufactured using F127 of Example 2 maintain the shape of the nanorods after firing (FIG. 7A), whereas in Comparative Example 2, the shape changes from a rod shape to a shape close to particles, It was recognized that the diameter of the nanorods was 30 μm or more (FIG. 7B). That is, the titania nanorod manufactured using F127, which is a block copolymer, has a feature that the shape does not change even when fired. This is thought to be because the titania nanorods are not bonded to each other even when fired because F127 encloses and isolates the titania nanorods one by one.

  Next, the crystal structure of titania nanorods was analyzed by XRD analysis. For the measurement, an X-ray diffractometer for thin film analysis (Rigaku Goniometer PMG-A2, CN2155D2 manufactured by Rigaku) was used.

  The X-ray diffraction peak of the oxide semiconductor layer 7 of Example 2 coincided with the anatase type crystal peak position found in the diffraction pattern card JCPDS. The half-value width of the diffraction peak on the (101) plane, which is a characteristic peak of anatase phase titania, was 1 degree. The X-ray diffraction peak of Comparative Example 2 also showed the crystal peak position of the anatase phase, but the half width of the (101) plane diffraction peak was 1.5 degrees.

In the case of Comparative Example 3, an anatase phase crystal peak was obtained, but a rutile phase peak was also observed. The half width of the (101) plane diffraction peak was 2 degrees.
From these results, it is shown that the crystallinity of the titania nanorod constituting the oxide semiconductor layer 7 of Example 2 is higher than that of Comparative Example 2 and Comparative Example 3.

  FIG. 8 shows X-ray diffraction patterns of the oxide semiconductor layer 7 before and after firing in Example 2. The strength ratio (004) / (200) before firing was 1.0, whereas the value after firing was 0.893, which was only about 10% smaller even after firing. This indicates that the highly crystalline titania nanorods according to the present invention change very little even when fired. This is also a feature of the highly crystalline titania nanorod according to the present invention as well as the shape does not change by firing as described above.

Moreover, when the BET specific surface area before and after baking a titania nanorod was measured, the remarkable change was not seen with 45.5 m < ² > / g before baking and 43.7 m < ² > / g after baking. This also indicates that the structure of the titania nanorod according to the present invention does not change before and after firing.

(Application to dye-sensitized solar cells)
Next, a highly crystalline titania nanorod was applied to the dye-sensitized solar cell 1 and its performance was evaluated. Since tin oxide doped with fluorine has a larger electric resistance than metal, when the transparent electrode 2 is enlarged, the efficiency of the dye-sensitized solar cell 1 is greatly reduced by the resistance. Therefore, the dye-sensitized solar cell 1 was manufactured by producing a transparent electrode 2 in which a tin oxide film doped with fluorine and a metal wiring were combined.

<Example 3>
The transparent electrode 2 was produced by the following procedure, and after forming the oxide semiconductor layer 7 on the transparent electrode 2 by the method shown in Example 2, the dye-sensitized solar cell 1 was produced.
First, as shown in FIG. 9, a groove 53 is laid on a glass substrate 51 on which a fluorine-doped tin oxide film 52 is formed on a glass substrate, and a silver paste (made by Tanaka Kikinzoku) is placed in the groove 53. The metal wiring 54 was installed by embedding and baking at 550 ° C. for 1 hour.

  In order to electrically connect the metal wiring 54 and the fluorine-doped tin oxide film, an indium-doped tin oxide precursor solution (ITO-05, manufactured by Kojundo Chemical Laboratories) was applied at 400 ° C. Baked for 1 hour. The ITO thin film 55 thus produced serves to protect the metal wiring 54 from the electrolytic solution 5 as well as to ensure electrical connection between the metal wiring 54 and the fluorine-doped tin oxide film 52.

An oxide semiconductor layer 7 was formed on the transparent electrode 2 thus obtained by the same method as in Example 2. Subsequently, the sensitizing dye 6 was adsorbed on the oxide semiconductor layer 7. First, as sensitizing dye 6, cis-Di (thiocyanato) -N, N′-bis (2,2′-bipyrylyl-4,4′dicarboxylic acid) -Ruthenium (II) (trade name N719, manufactured by solaronix) was used. A solution dissolved in ethanol at a concentration of 3 × 10 ⁻⁴ mol / L was prepared.

  Next, the transparent electrode 2 on which the oxide semiconductor layer 7 was laminated was immersed in this solution and allowed to stand at 40 ° C. for 20 hours. Thereafter, the transparent electrode 2 was taken out from this solution, washed with ethanol, and naturally dried in a dark place. Thereby, the oxide semiconductor layer 7 adsorbing the sensitizing dye 6 was formed on the transparent electrode 2.

  Next, an electrode in which platinum was sputtered on the surface of a transparent conductive glass (ITO sputtered glass, manufactured by Nippon Sheet Glass Co., Ltd.) having the same size as the transparent electrode 2 was manufactured as the counter electrode 4.

  Further, as an electrolytic solution 5, an iodine-based redox solution (iodine 0.05 mol / L, lithium iodide 0.1 mol / L, 2,3 dimethyl-imidazolium iodide 0.5 mol / L, solvent; Methoxyacetonitrile) was prepared.

  Further, the transparent electrode 2 and the counter electrode 4 were opposed to each other through the spacer 11 and heated to bring the both electrode and the spacer 11 into close contact. The spacer 11 was made of an ionomer (trade name: High Milan 1702, manufactured by Mitsui DuPont Polychemical Co., Ltd.). Then, by using the capillary phenomenon, the space formed by the spacer 11, the transparent electrode 2 and the counter electrode 4 is filled with the electrolytic solution 5, and then the opening between the transparent electrode 2 and the counter electrode 4 is bonded with epoxy. The dye-sensitized solar cell 1 was completed by sealing with an agent.

<Example 4>
As described above, the oxide semiconductor layer 7 is composed of titania nanoparticles having a particle diameter of 1 to 5 nm so that I ₃ ⁻ can reach the counter electrode 4 without being prevented from diffusing in the pores of the oxide semiconductor layer 7. Dye enhancement formed by the first porous layer 31, the second porous layer containing titania nanorods having an anatase phase of 5 to 30 nm in diameter, and the third porous layer containing titania nanorods having a maximum diameter exceeding 30 nm A solar cell 1 was manufactured.

(Construction of the first porous layer 31)
First, titania nanoparticles having a particle diameter of 1 to 5 nm constituting the first porous layer were produced. 0.2 g of 2 molar hydrochloric acid was added to 30 mL of distilled water, and 3 g of F127 was dissolved therein to prepare an aqueous solution containing 10 wt% of F127. Next, titanium alkoxide tetraisopropyl orthotitanate (TIPT) and acetylacetone (ACA) were mixed at a molar ratio of 1: 1. Specifically, 3.4 g of TIPT and 1.2 g of ACA were mixed.

Then, the 10 wt% aqueous solution of F127 and the mixed solution of TIPT and ACA were mixed at 40 ° C. and stirred for 24 hours to obtain a transparent liquid. The liquid that became transparent was allowed to gel for 3 days without stirring in an air constant temperature bath at 80 ° C. to obtain a white suspension containing titania. (Hereinafter, this suspension is referred to as slurry D.)
In addition, it confirmed by SEM observation that the particle diameter of the obtained titania nanoparticle was 2-4 nm.

Next, slurry D was applied onto the transparent electrode 2 by a doctor blade method using a mending tape as a support. The transparent electrode coated with the titania nanoparticles was naturally dried at room temperature in the atmosphere and then placed in an electric furnace heated to 450 ° C. and baked for 10 minutes.
Subsequently, the operation of applying slurry D on the transparent electrode 2 on which the titania nanoparticles were baked and baking it by a doctor blade method was repeated three times. The firing condition was 450 ° C. for 10 minutes.

(Construction of the second porous layer 32)
On the first porous layer obtained here, the slurry A obtained in Example 1 was applied by a doctor blade method using a mending tape as a support. The transparent electrode coated with the titania nanorods was naturally dried in the atmosphere at room temperature, and then placed in an electric furnace heated to 450 ° C. and baked for 10 minutes.
Subsequently, the operation of applying slurry A to the transparent electrode 2 on which the titania nanorods were fired by the doctor blade method and firing was repeated three times. The firing condition was 450 ° C. for 10 minutes.

(Construction of the third porous layer 33)
A third porous layer was constructed for the purpose of extending the optical path length using light scattering. That is, the slurry B used in Comparative Example 1 was applied onto the second porous layer 32 by a doctor blade method using a mending tape as a support. After the coating, it was naturally dried at room temperature in the atmosphere, and then baked for 40 minutes in an electric furnace heated to 450 ° C.

(Manufacture of dye-sensitized solar cell 1)
The sensitizing dye 6 is adsorbed to the transparent electrode 2 on which the oxide semiconductor layer 7 thus formed is laminated in the same manner as in Example 3, and the dye-sensitized solar cell 1 is completed in the same manner as in Example 3. It was.

<Comparative example 4>
A dye-sensitized solar cell 1 was manufactured in the same manner as in Example 3 except that the oxide semiconductor layer 7 was formed using the oxide semiconductor 3 manufactured without using F127. .

<Comparative Example 5>
A dye-sensitized solar cell 1 was manufactured in the same manner as in Example 3 except that the oxide semiconductor layer 7 was formed using P25, which is a commercially available titania nanoparticle, and used as Comparative Example 5.

(Characteristic evaluation as dye-sensitized solar cell)
Characteristic evaluation as a dye-sensitized solar cell, such as the short circuit current density and fill factor of Example 3, Comparative Example 4, and Comparative Example 5, was performed according to the following procedures and measurement conditions. The characteristic evaluation was performed by irradiating simulated sunlight under the conditions of irradiation intensity 1 Sun and air mass 1.5 using a solar simulator (product name: XIL-05A50K, manufactured by Celic).

About each dye-sensitized solar cell 1 of Example 3, Example 4, Comparative Example 4, and Comparative Example 5, using potentiostat (BAS-100W, manufactured by BAS), current / voltage at room temperature (20 ° C.) The characteristics were measured, the open circuit voltage (hereinafter Voc: unit V), the short-circuit current density (hereinafter Jsc: unit mA / cm ² ), and the fill factor were calculated, and the photoelectric conversion efficiency (unit%) at the initial stage of startup was determined from these.

(Influence of block copolymer on battery characteristics)
The characteristics of the dye-sensitized solar cell 1 of Example 3 and Comparative Example 4 were measured by the above method, and the results are shown in Table 1.

  As is clear from Table 1, the Voc, Jsc, fill factor, and photoelectric conversion efficiency of the dye-sensitized solar cell 1 of Example 3 are all superior to those of Comparative Example 4, and exhibit excellent characteristics as a battery by firing. It was recognized that This is considered to be because, in Example 3, F127 enclosing the titania nanorods becomes carbon by firing, and the surface of the titania nanorods is covered like an insulating layer to prevent leakage of electrons during transportation. it can.

(Comparison of battery characteristics with nanoparticles)
Table 2 shows the results of comparing the characteristics of the dye-sensitized solar cell 1 of Example 3 and Comparative Example 5 (battery using commercially available titania particles).

  From Table 2, the dye-sensitized solar cell using the highly crystalline titania nanorods of the present invention has a performance superior to that when titania nanoparticles are used, and in particular, the photoelectric conversion efficiency is about 1.5 times. It can be seen that This shows that the titania nanorod of the present invention is suitable for a dye-sensitized solar cell.

(Comparison by construction of porous layer)
Table 3 shows the results of measuring the characteristics of the dye-sensitized solar cell 1 obtained by constructing the porous layer for Example 3 and Example 4.

As is apparent from Table 3, since the oxide semiconductor layer 7 is formed of the first porous layer 31 to the third porous layer 33, the diffusion of I ₃ ⁻ proceeds without being suppressed. It can be seen that the value Jsc increases. From this, it can be seen that the dye-sensitized solar cell 1 exhibiting higher photoelectric conversion efficiency can be produced by applying the titania nanorod of the present invention and laminating the porous layer.

  FIG. 10 shows the relationship between the film thickness of the oxide semiconductor layer 7, Jsc, and photoelectric conversion efficiency for Example 3 and Comparative Example 5. In a relatively thin region having a film thickness of 8 μm or less, both Jscs are the same or tend to be slightly higher in Comparative Example 5.

However, when the film thickness exceeds 8 μm, the Jsc of the battery of Example 3 continues to increase and exceeds that of Comparative Example 5. Further, the photoelectric conversion efficiency of Example 3 monotonously increased to 7.5% even when the film thickness exceeded 8 μm, and reached 7.5%, but the photoelectric conversion efficiency of Comparative Example 5 was about 5 when the film thickness exceeded 8 μm. % Tends to saturate.
Since the photoelectric conversion efficiency of the solar cell using titania reported conventionally is 7 to 8% at the maximum, it can be said that the titania nanorod according to the present invention has a high photoelectric conversion efficiency.

Further, as shown in FIG. 11, in the region where the adsorption amount of the sensitizing dye 6 is 6 × 10 ⁻⁸ mol / cm ² or less, the Jsc curves with respect to the dye adsorption amounts of Example 3 and Comparative Example 5 almost overlap. However, in the region where the amount of dye adsorbed was larger than this, Jsc of Example 3 showed a tendency to increase linearly, whereas Jsc of Comparative Example 5 showed a tendency to become saturated.
Thus, the linear increase tendency of Jsc in the high dye concentration region in Example 3 is recognized. If a highly crystalline titania nanorod is used, a more efficient dye-sensitized solar cell can be obtained. It shows that there is.

  In Example 3, high Jsc and photoelectric conversion efficiency are recognized because in the highly crystalline and uniform titania nanorod as seen in the HRTEM photograph of FIG. It is thought that electron transfer takes place. Compared to nanoparticles, the conductive band is formed longer in the titania nanorods, so that it can be said that it is an electrically homogeneous material and the movement of electrons is facilitated. Furthermore, if highly crystalline titania nanorods are used instead of titania nanoparticles, the number of contact points between titania at the granular interface that can become electron traps is also a factor that facilitates the movement of electrons.

  This is supported by the relationship between fill factor and film thickness in Example 3 and Comparative Example 5 shown in FIG. The fill factor correlates with the resistance of the battery. When electrons can move quickly and efficiently, the resistance decreases and the fill factor increases. As is clear from FIG. 12, in Comparative Example 5, the fill factor tends to decrease as the film thickness increases. This indicates that the resistance increases as the thickness of titania nanoparticles having semiconducting properties increases.

  However, in the dye-sensitized solar cell 1 using the highly crystalline titania nanorod of Example 3, the fill factor does not decrease even when the film thickness increases, and the resistance does not increase even when the film thickness increases. Is shown. From the above, it can be seen that the highly crystalline titania nanorod of the present invention is a material suitable for electron transport.

FIG. 13 shows Jsc-voltage characteristics of the dye-sensitized solar cell 1 of Example 3 and Comparative Example 5. As can be seen from this figure, the dye-sensitized solar cell 1 of Example 3 shows higher values for both Jsc and Voc than Comparative Example 5 and has excellent battery characteristics. In addition, the film thickness of the oxide semiconductor layer 7 of the titania nanorod adsorbing the sensitizing dye 6 of Example 3 used here is 16 μm, the adsorption amount of the sensitizing dye 6 is 10 mol / cm ² , and the increase in Comparative Example 5 is used. The film thickness of the oxide semiconductor layer 7 of titania nanoparticles having adsorbed the dye 6 is 16 μm, and the adsorption amount of the sensitizing dye 6 is 12 × 10 ⁻⁸ mol / cm ² .

Incidentally, and the BET specific surface area, titania nanorods of Example 3 is ^{45 m} 2 / g, it was slightly less than the 50~55m ² / g of P25. This is an expected result because the nanorod of Example 3 has a large size (length) but a small surface area. This also indicates that by reducing the diameter of the titania nanorods and increasing the surface area, the adsorption amount of the sensitizing dye 6 can be further increased to increase the photoelectric conversion efficiency.

It is a schematic diagram of a dye-sensitized solar cell. It is the schematic diagram showing the cross-section of the dye-sensitized solar cell which concerns on this embodiment. It is the elements on larger scale of the oxide semiconductor layer concerning this embodiment. It is the elements on larger scale of the modification of the oxide semiconductor layer which concerns on this embodiment. 5A to 5C are TEM photographs, SEM photographs, and HRTEM photographs of Example 1, and FIGS. 5D and 5E are TEM photographs and SEM photographs of Comparative Example 1. FIG. It is a figure showing the XRD measurement result of Example 1 and Comparative Example 1. 7A is an SEM photograph of Example 2 after firing the oxide semiconductor layer of FIG. 7B Comparative Example 2. FIG. 6 is a diagram illustrating an XRD measurement result before and after firing an oxide semiconductor layer of Example 2. FIG. It is sectional drawing showing the structure of the transparent electrode used in each Example. It is the figure which showed the relationship between the film thickness of an oxide semiconductor layer, Jsc, and photoelectric conversion efficiency of Example 3 and Comparative Example 5. It is the figure which showed the relationship between the dye adsorption amount and Jsc of Example 3 and Comparative Example 5. It is the figure which showed the relationship between the fill factor and film thickness of Example 3 and Comparative Example 5. It is the figure which showed the relationship between Jsc of the dye-sensitized solar cell of Example 3 and Comparative Example 5, and a voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dye-sensitized solar cell 2 Transparent electrode 3 Oxide semiconductor 4 Counter electrode 5 Electrolytic solution 6 Sensitizing dye 7 Oxide semiconductor layer 11 Spacer 12 External load 31 1st porous layer 32 2nd porous layer 33 3rd porous Layer U Incident light

Claims (13)

  An anatase phase titania nanorod having an X-ray diffraction intensity ratio (004) / (200) of (004) plane and (200) plane in the Miller index display of 0.85 to 1.0.   2. The anatase phase titania nanorod according to claim 1, wherein the nanorod has a diameter of 5 to 30 nm and a length of 50 to 300 nm. A step of obtaining a titania sol by reacting a block copolymer having a hydrophobic block and a hydrophilic block, and an aqueous solution containing an organic amine or ammonia with a titanium organic compound;
And a step of producing a titania nanorod by hydrothermal reaction of the titania sol.   The method for producing anatase-phase titania nanorods according to claim 3, wherein the aqueous solution further contains a cationic surfactant. The method for producing anatase titania nanorods according to claim 4, wherein the cationic surfactant is a halogenated quaternary ammonium salt containing a long-chain alkyl group.
The said titanium organic compound is a titanium alkoxide represented by Ti (OR) ₄ (R is a C1-C6 alkyl group), The any one of Claims 3-5 characterized by the above-mentioned. Of producing anatase phase titania nanorods.   7. The block copolymer having the hydrophobic block and the hydrophilic block, wherein the hydrophobic block is polyoxypropylene, and the hydrophilic block is polyoxyethylene. A method for producing an anatase phase titania nanorod according to claim 1.   The block copolymer having the hydrophobic block and the hydrophilic block is a ternary block copolymer composed of polyoxyethylene-polyoxypropylene-polyoxyethylene. Method for producing anatase phase titania nanorods.   The method for producing an anatase titania nanorod according to any one of claims 3 to 8, wherein the organic amine is an aliphatic amine or an aliphatic diamine. A transparent electrode;
A porous oxide semiconductor layer laminated on the transparent electrode and having a sensitizing dye adsorbed on the surface;
A counter electrode provided to face the transparent electrode;
A dye-sensitized solar cell comprising: an electrolyte solution impregnated between the transparent electrode and the counter electrode;
The said oxide semiconductor layer contains the titania nanorod of the anatase phase of Claim 1 or Claim 2, The dye-sensitized solar cell characterized by the above-mentioned. The porous oxide semiconductor layer is
A first porous layer formed by laminating oxide semiconductor nanoparticles having a particle size of 1 to 5 nm on the transparent electrode;
A second porous layer containing titania nanorods of anatase phase having a diameter of 5 to 30 nm and laminated on the first porous layer;
The dye-sensitized solar cell according to claim 10, wherein   12. The dye according to claim 11, comprising a third porous layer containing oxide semiconductor nanoparticles or oxide semiconductor nanorods having a maximum diameter of more than 30 nm and laminated on the second porous layer. Sensitized solar cell.   The layer thickness of the first porous layer is 0.5 to 5 μm, and the sum of the layer thickness of the second porous layer and the layer thickness of the third porous layer is 3 to 50 μm. The dye-sensitized solar cell according to claim 12, which is characterized by: