JP4730951B2 - Porphyrin dye having trimethylsilyl group, photoelectric conversion element using the same, and dye-sensitized solar cell - Google Patents

Description

  The present invention relates to a porphyrin dye that can be suitably used as a sensitizing dye in a dye-sensitized photoelectric conversion element and a solar cell, and the photoelectric conversion element and the solar cell using the porphyrin dye.

  Solar cells are highly expected as clean, regenerative energy sources. Single-crystal silicon-based, polycrystalline silicon-based, amorphous silicon-based solar cells, and solar cells made of compound semiconductors such as cadmium telluride and indium copper selenide However, in order to spread it as a household power source, all the solar cells have many problems such as high cost and problems of securing raw materials.

  Under such circumstances, it is said that the dye-sensitized solar cell is very advantageous in terms of cost, large area, and raw materials. A dye-sensitized solar cell, a dye-sensitized photoelectric conversion element, and a photoelectrochemical cell are formed from a photoelectrode, a charge transfer layer, and a counter electrode, each of which includes a semiconductor fine particle-containing layer that adsorbs a dye formed on a conductive support. Composed. In particular, Nature (Vol. 353, 737-740, 1991) and US Pat. No. 4,927,721 disclose a photoelectric conversion element and a solar cell using semiconductor fine particles sensitized with a dye, and a material for producing the same. And manufacturing techniques are disclosed.

  Here, metal oxide semiconductors such as titanium dioxide, zinc oxide, and tin oxide used as photo semiconductor electrode materials are stable and harmless to light and heat, but because the band gap is as large as 3.0 eV, It cannot absorb the most intensely visible or near infrared sunlight. When a dye such as an organic substance or a metal complex that absorbs visible light is adsorbed or coated on the surface of the metal oxide optical semiconductor electrode, the wavelength region in which the electrode performs photoelectric conversion can be expanded to the visible light region.

  Since only the dye adsorbed on the surface of the semiconductor electrode by the monomolecular layer is dye-sensitized, the light utilization efficiency is about 1% when the dye is adsorbed on the smooth semiconductor surface by the monomolecular layer. As a result, the photoelectric conversion efficiency is low. In order to increase the light utilization efficiency of the electrode, it is necessary to make the surface of the semiconductor adsorbed with the dye as large as possible with respect to the light irradiation area.

  It is known to use titanium dioxide (Japanese Patent Laid-Open No. 1-220380) having a large specific surface area or a titanium dioxide thin film having a pore on the surface (Japanese Patent Laid-Open No. 8-99041) as a semiconductor electrode. . Many compounds such as xanthene organic dyes, cyanine dyes, basic dyes, porphyrin compounds, phthalocyanine compounds, azo dyes, ruthenium metal complexes are known as sensitizing dyes (Japanese Patent Publication No. 7-500630). JP, 11-144772, JP 13-59062, JP 13-253894, JP 13-247546).

  Currently, from the point of photoelectric conversion efficiency, ruthenium metal complex dyes are said to be the most dominant, but ruthenium is an expensive metal, and the wavelength range of sunlight absorbed by the dye is about 300 to 900 nm. is there. In the future, in order to further increase the photoelectric conversion efficiency, it is essential to develop a sensitizing dye that absorbs most of the wavelength region of sunlight. To further emphasize the low cost of dye-sensitized solar cells, It must be possible to use inexpensive dyes.

Nature (Vol. 353, 737-740, 1991) U.S. Pat. No. 4,927,721 JP-A-1-220380 JP-A 8-99041 Special table hei 7-500630 JP 11-144772 A JP-A-13-59062 JP-A-13-253894 JP-A-13-247546

  The present invention has an absorptive ability in a wide wavelength range, and can be used as a sensitizing dye for a dye-sensitized photoelectric conversion element or a solar cell without requiring an expensive metal as a central metal. It is an object of the present invention to provide a possible new dye body, and the photoelectric conversion element and the solar cell using the dye body.

In order to solve the above problems, the present invention provides:
The present invention relates to a porphyrin characterized by being represented by the general formula (a): (wherein one of R is a carboxyl group and three R are trimethylsilyl groups (—Si (CH ₃ ) ₃ )) .

  The inventors of the present invention have intensively studied to achieve the above object. As a result, the inventors have focused on porphyrin dyes that do not require the use of an expensive metal as a central metal as a dye body in order to achieve the above object. However, the porphyrin dye as it is cannot be sufficiently adsorbed on the surface of the metal oxide semiconductor electrode constituting the photoelectric conversion element when used as a dye-sensitized photoelectric conversion element or the like, and can be put to practical use. It turned out not to be possible. Furthermore, it was found that due to its low electron donating property, when the porphyrin dye was used as the dye body, sufficient electron transfer from the dye body to the metal oxide semiconductor electrode could not be caused. did.

In view of such a problem, the present inventors have further intensively studied and attempted to solve the above problem by introducing a functional group into the porphyrin dye. Specifically, by introducing a carboxyl group (—COOH) or the like to the porphyrin, the adsorptivity to the metal oxide semiconductor electrode or the like in the photoelectric conversion element or the like can be sufficiently improved. I found out. Furthermore, by introducing a trimethylsilyl group (—Si (CH ₃ ) ₃ ) into the porphyrin, it is possible to impart electron donating properties to the porphyrin, and from the porphyrin to the metal oxide semiconductor electrode. It was found that it is possible to generate sufficient electron transfer.

  Therefore, the porphyrin of the present invention described above can be suitably used as a sensitizing dye in a photoelectric conversion element including a metal oxide semiconductor electrode or a solar cell, and sensitization in a dye-sensitized photoelectric conversion element or a solar cell. It can be used as a new and inexpensive pigment that can be used as a pigment.

  In a preferred embodiment of the present invention, three of R in the general formula of the porphyrin dye described above are trimethylsilyl groups, and so-called 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilyl) It constitutes an isomer called phenyl) porphyrin. In this case, one of the Rs is a carboxyl group, which can sufficiently secure the adsorptivity with the metal oxide semiconductor electrode constituting the photoelectric conversion element and the like, and the metal oxide described above. The electron donating property to the semiconductor electrode can be sufficiently increased. As a result, the photoelectric conversion efficiency of the photoelectric conversion element having the porphyrin dye can be sufficiently increased.

  Moreover, the photoelectric conversion element and solar cell of this invention are characterized by having the porphyrin dye mentioned above as a sensitizing dye.

  As described above, according to the present invention, a dye-sensitized photoelectric conversion element, a solar cell, or the like has an absorption ability in a wide wavelength range and does not require an expensive metal as a central metal. It is possible to provide a novel dye body that can be used as a sensitizing dye, and the photoelectric conversion element and the solar cell using the dye body.

  Hereinafter, other features and advantages of the present invention will be described based on the best mode for carrying out the invention.

(Porphyrin chromophore)
As described above, the porphyrin of the present invention can be used as a sensitizing dye for dye-sensitized photoelectric conversion elements and solar cells. In this case, it is necessary that the porphyrin has an adsorptivity with the metal oxide semiconductor electrode constituting the photoelectric conversion element, and therefore, the porphyrin has a carboxyl group (—COOH) as a polar group. is required. However, examples of the polar group having the same effect include a sulfo group (—SO ₃ H), an amino group (—NH ₂ ), and a pyridyl group (C ₅ H ₄ N) in addition to the carboxyl group. can do. However, a carboxyl group is particularly preferable.

  Further, as described above, the porphyrin of the present invention is a so-called 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin, in which three of R are trimethylsilyl groups. It is preferable to constitute an isomer. In this case, one of the Rs is a carboxyl group, which can sufficiently secure the adsorptivity with the metal oxide semiconductor electrode constituting the photoelectric conversion element and the like, and the metal oxide described above. The electron donating property to the semiconductor electrode can be sufficiently increased. As a result, the photoelectric conversion efficiency of the photoelectric conversion element having the porphyrin dye can be sufficiently increased.

The isomer can be represented by the following general formula (b).

  The porphyrin production method of the present invention will be specifically described in detail in the following examples.

(Photoelectric conversion element)
The photoelectric conversion element and solar cell of the present invention adsorb the above-described porphyrin on the surface of the metal oxide semiconductor electrode as a sensitizing dye. This metal oxide semiconductor electrode is preferably a porous electrode. As a result, the substantial surface area of the electrode can be increased, and the amount of sensitizing dye adsorbed to the electrode can be increased to increase the photoelectric conversion efficiency of the photoelectric conversion element and the like. . Such a porous metal oxide semiconductor electrode is formed by accumulating fine oxide semiconductor fine particles.

  FIG. 1 is a configuration diagram illustrating an example of the photoelectric conversion element of the present invention, and FIG. 2 is an enlarged view illustrating the vicinity of an oxide semiconductor electrode of the photoelectric conversion element illustrated in FIG. 1. The photoelectric conversion element 100 shown in FIG. 1 is arranged so that the photoelectrode 101 and the counter electrode 109 face each other, and a partition wall 120 is provided between both electrodes, and is formed by these electrodes and the partition wall. An electrolyte 108 is injected into the space.

  As shown in FIG. 2, the photoelectrode 101 is formed as a transparent conductive substrate 102 by forming a transparent conductive layer 105 on a transparent substrate 104, and then an oxide semiconductor electrode 103 is formed on the transparent conductive substrate 102. Being done. The oxide semiconductor electrode 103 is configured by adsorbing the sensitizing dye 107 on the oxide semiconductor fine particles 106. Thus, since the oxide semiconductor electrode 103 is composed of the oxide semiconductor fine particles 106, the oxide semiconductor electrode 103 can be configured to be porous and increase the adsorption amount of the sensitizing dye 107.

  The sensitizing dye 107 is composed of the porphyrin described above according to the present invention. The carboxyl group of the porphyrin exhibits high adsorptivity to the oxide semiconductor fine particles 106, whereby the sensitizing dye 107 made of porphyrin is stably adsorbed to the oxide semiconductor fine particles 106. Further, since the porphyrin has a trimethylsilyl group, the oxide semiconductor fine particles 106 exhibit high electron donating properties.

  As the transparent substrate 104, a general-purpose glass substrate and a quartz substrate, a transparent plastic substrate such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, and polyethylene can be used. Specifically, it can be appropriately selected in consideration of stability, workability, lightness, flexibility, and the like.

  For the transparent conductive layer 105, tin oxide, fluorine-doped tin oxide, ITO, ATO, zinc oxide, aluminum-doped zinc oxide, or a light-transmitting transparent conductive material in which a coating of tin oxide or fluorine-doped tin oxide is provided on the surface thereof. It can consist of layers.

  As the oxide semiconductor fine particles 106 of the oxide semiconductor electrode 103, for example, a single metal oxide or a compound having a perovskite structure can be used. The single metal oxide is preferably an oxide of titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum. Preferred examples of the compound having a perovskite structure include strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate.

  However, in the present invention, the porphyrin described above is used as the sensitizing dye 107, and at least one of titanium oxide, zinc oxide, and zirconium oxide is used in consideration of the adsorptivity to the sensitizing dye and the electron donating property. Is preferred.

  Note that the oxide semiconductor fine particles 106 preferably have a particle size of 5 nm to 500 nm, more preferably 10 nm to 300 nm, and particularly preferably 15 nm to 200 nm.

The electrolyte 108 can be used in a solid or liquid state. Specifically, it is possible to use various electrolytes such as iodine-based electrolyte, bromine-based electrolyte, selenium-based electrolyte, sulfur-based electrolyte, I ₂ , LiI, dimethylpropylimidazolium iodide, t-butylpyridine, A solution in which 1,2-dimethyl-3-propylimidazolium iodide is dissolved in an electrically inactive organic solvent such as acetonitrile, methoxyacetonitrile, propylene carbonate, ethylene carbonate, 3-methoxypropionyl, propylene carbonate, etc. is suitable. Used for.

  Further, for the purpose of reducing the volatilization of the electrolyte, it is possible to dissolve the gelling agent, the polymer crosslinking monomer or the like in the above-described electrolyte composition and use it as a gel electrolyte. As for the ratio between the gel matrix and the electrolyte composition, the greater the electrolyte composition, the higher the ionic conductivity, but the lower the mechanical strength. On the other hand, if the electrolyte composition is too small, the mechanical strength is high, but the ionic conductivity decreases. Therefore, the electrolyte composition is desirably 50 wt% to 99 wt% of the gel electrolyte, and more preferably 80 wt% to 97 wt%.

  Furthermore, it is also possible to realize an all-solid-type photoelectric conversion element by dissolving it in a polymer using the electrolyte and the plasticizer and volatilizing and removing the plasticizer.

  The counter electrode 109 is, for example, a substrate made of a metal such as Al or SUS, glass, plastic, and the like, and a conductive material such as Pt, C, Ni, Cr, stainless steel, fluorine-doped tin oxide, or ITO formed thereon. Composed of layers. Moreover, it can also be comprised from the electroconductive glass which provided conductive layers, such as fluorine dope tin oxide, on the surface.

  The counter electrode 109 can include a catalyst layer such as platinum or carbon. As a result, the electron transfer between the counter electrode 109 and the electrolyte 108 can be performed more easily.

(Manufacturing method of photoelectric conversion element)
Next, the manufacturing method of the photoelectric conversion element of this invention is demonstrated. In order to clarify the description, a manufacturing method thereof will be described below based on the photoelectric conversion element 100 shown in FIGS.

  First, the transparent substrate 104 is prepared, the transparent conductive layer 105 is formed on the transparent substrate 104, and the transparent conductive substrate 102 is produced. The transparent conductive layer 105 can be formed using a known film formation technique such as a sputtering method, a CVD method, or a coating method. A transparent substrate 104 on which a commercially available transparent conductive layer 105 is formed can also be used directly as the transparent conductive substrate 102.

  Next, an oxide semiconductor ink or paste containing the oxide semiconductor fine particles 106 is prepared, coated on the transparent conductive substrate 102 by a wet coating method or a wet printing method, and baked to remove components other than the oxide semiconductor fine particles. As a result, the oxide semiconductor fine particles 106 are formed in layers on the transparent conductive substrate 102, and the photoelectrode 101 is formed.

  In addition, wet film forming methods such as the above wet coating method and wet printing method are advantageous methods in consideration of physical properties of the formed film, convenience, manufacturing cost, and the like. Specific examples of the wet coating method include spin coating, roller coating, dipping, spraying, wire bar, blade coating, and gravure coating. In addition, as the wet printing method, methods such as letterpress, offset, gravure, intaglio, rubber plate, and screen printing can be used.

  When a commercially available powder is used as the oxide semiconductor fine particles, it is preferable to eliminate secondary aggregation of the particles, and it is preferable to pulverize the particles using a mortar, a ball mill or the like when preparing the coating solution. At this time, it is preferable to add acetylacetone, hydrochloric acid, nitric acid, a surfactant, a chelating agent, or the like in order to prevent re-aggregation of particles whose secondary aggregation has been released. For the purpose of thickening, various thickeners such as polymers such as polyethylene oxide and polyvinyl alcohol and cellulose thickeners can be added.

  As said baking temperature, 250-600 degreeC is used, Preferably 400-550 degreeC is used. If the firing temperature is lower than the above range, a good crystal state cannot be obtained. Therefore, the produced oxide photo semiconductor fine particle film is not preferable because it becomes a high resistance film. Becomes noticeable and the specific surface area decreases, which is not preferable.

  Next, the sensitizing dye 107 is dissolved in a predetermined solvent to prepare a sensitizing dye solution, and the oxide semiconductor fine particle film 106 is immersed in the solution together with the substrate, whereby the sensitizing dye 107 is converted into the oxide semiconductor fine particles. It is adsorbed and supported on 106. Examples of the solvent include alcohols such as methanol, ethanol, 2 propanol, 1 butanol and t-butanol, nitriles such as acetonitrile, methoxyacetonitrile, propionitrile and 3 methoxypropionitrile, and aromatic compounds such as benzene and toluene. Or a mixed solvent thereof can be used.

  The sensitizing dye 107 is composed of the porphyrin of the present invention. Since this porphyrin usually exists in a powder state, when preparing the above-mentioned solution, the porphyrin powder is uniformly dispersed and dissolved in the solvent.

  Next, if necessary, a counter electrode 109 having a catalyst layer is prepared to face the photoelectrode 101, a partition wall 120 is provided therebetween, and the electrolyte 108 is injected into a space formed by these electrodes and the partition wall. The target photoelectric conversion element 100 is obtained.

(Dye-sensitized solar cell)
The dye-sensitized solar cell of the present invention can be obtained by modularizing the photoelectric conversion element 100 shown in FIG. 1 and providing predetermined electrical wiring.

  3 and 4 are configuration diagrams illustrating an example of a dye-sensitized solar cell configured using the photoelectric conversion element illustrated in FIGS. 1 and 2. FIG. 3 is a development configuration diagram of the dye-sensitized solar cell, and FIG. 4 is a side sectional view of the dye-sensitized solar cell. 3 and 4, the same reference numerals are used for components similar to those in FIGS. 1 and 2.

  As shown in FIGS. 3 and 4, the solar cell 200 of the present invention is arranged such that the photoelectrode 102 and the counter electrode 109 face each other with a spacer 203 interposed therebetween. The photoelectrode 101 has the same structure as that shown in FIGS. 1 and 2, and an oxide semiconductor electrode 103 on which a sensitizing dye made of the porphyrin of the present invention is adsorbed is formed on a transparent conductive substrate 102. In addition, the spacer 203 is provided with an opening 203A at a substantially central portion, and an electrolyte 108 is injected into the opening 203A.

  In addition, a copper wire 207 for extracting current is fixed to the photoelectrode 101 and the counter electrode 109 by solder 205. Accordingly, porphyrin (not shown) which is a sensitizing dye in the oxide semiconductor electrode 103 is excited by the light hυ incident from the photoelectrode 101 side, and excited electrons are provided to the oxide semiconductor fine particles (not shown). At the same time, the electrons are supplied to the counter electrode 109 through the electrolyte 108, and the current thus generated is taken out by the copper wire 207.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely according to an Example, this invention is not limited to the content of an Example.

(Example)
<Synthesis of porphyrin dye>
4-Trimethylsilylbenzaldehyde (4.83 g, 27.1 mmol) and terephthalaldehyde acid (1.35 g, 8.99 mmol) were dissolved in propionic acid (150 mL), and pyrrole (2.5 mL, 36 mmol) was added dropwise while heating under reflux. This was refluxed for an additional hour and cooled to room temperature. The reaction mixture was concentrated under reduced pressure to about 35 mL, and water-methanol (1: 1, 50 mL) was added thereto and stirred. The precipitated solid was filtered by suction and dried under reduced pressure. Next, a part (1.0 g) of the obtained solid (5.78 g) was separated by column chromatography (silica gel, the solvent was chloroform and then chloroform-methanol (95: 5)), and the resulting black purple solid was obtained. Is separated by column chromatography (silica gel, solvent is dichloromethane-chloroform-ethyl acetate-methanol (50: 40: 7: 3)) to give 5- (4-carboxyphenyl) -10,15,20-Tris 0.051 g of (4-trimethylsilylphenyl) porphyrin was obtained as a purple solid. The yield in terms of solid (5.78 g) obtained after the reaction is 4%.

<Result of identification>
The structure of 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin was identified by the following spectrum.
¹ H NMR (CDCl ₃ ): δ-2.79 (s, 2H), 0.50 (s, 27H), 7.89 (d, 6H, J = 7.4 Hz), 8.19 (d, 6H, J = 7.4 Hz), 8.35 ( d, 2H, J = 7.8 Hz), 8.52 (d, 2H, J = 7.8 Hz), 8.79 (d, 2H, J = 4.3 Hz), 8.86 (s, 4H), 8.89 (d, 2H, J = 4.3 ^{. Hz) 13 C NMR (CDCl} 3):. δ-0.9, 118.4, 120.4, 120.6, 128.1, 129.6, 131.59, 131.61, 134.00, 134.04, 134.5, 139.6, 142.2, 142.3, 147.1 29 Si NMR (CDCl 3) : δ-3.5. IR (KBr): 3420, 3310, 3060, 3010, 2920, 1690, 1600, 1250, 1110, 970, 840, 800 cm ^-1 . UV-Vis (λ _max (ε), CHCl ₃ ) : 237 (17000), 421 (410000), 518 (15000), 552 (7300), 594 (3900), 647 nm (4100).

<Production of Photoelectrode in Photoelectric Conversion Element (Solar Cell)>
As a porous oxide semiconductor thin film used as a porous oxide semiconductor electrode, a paste of titanium dioxide (TiO ₂ ) powder (average particle size 21 nm) is fixed on a tin oxide-coated transparent conductive glass as a transparent electrode, A 15 μm porous TiO ₂ thin film was prepared.

As a specific method for manufacturing the porous TiO ₂ thin film, in order to produce a homogeneous porous TiO ₂ thin film efficiently, using spin coating in this example. The spin coating method is a method in which a solution or sol of a sample to be formed into a thin film is dropped on a substrate that rotates at high speed and is stretched on the substrate by centrifugal force to form a uniform film.

First, in order to prepare TiO ₂ sol, TiO ₂ powder (P-25, Nippon Aerosil; Rutile: anatase = 3: 7) having an average particle diameter of 21 nm was added to 3.0 g of acetylacetone (99.5%, Kanto Chemical). The operation of adding 0.1 ml and 0.1 ml of ion exchange water, stirring and mixing in an agate mortar for 10 minutes, adding 1.0 ml of ion exchange water and stirring and mixing for 30 minutes was repeated 7 times. To this, 0.1 ml of Triton X-100 (ICN Biomedicals Inc.) and 1.0 ml of ion-exchanged water were added. After stirring and mixing for 5 minutes, 7 ml of ion-exchanged water was added, and an ultrasonic cleaner was used for over 1 hour. Sonication was performed to obtain a TiO ₂ sol.

Then, a tin oxide-coated transparent conductive glass (15 to 20Ω / □, 25 × 50 × 1.1 mm ³ , Asahi Glass) is used as a substrate, fixed on a sample table in the center of a spin coater (ACTIVE ACT-300A), and TiO _2. In order to spread the sol uniformly, first, 5 drops of a Triton X-100: water = 1: 100 solution were dropped, and the temperature was increased to 2000 rpm in 0.1 second and rotated at 2000 rpm for 3 seconds. Next, methanol is evenly dropped on the tin oxide-coated transparent conductive glass and rotated at the above rotation speed and time. After that, the TiO ₂ sol is evenly dropped on the tin oxide-coated transparent conductive glass, and the same rotation speed and time are obtained. It was rotated to produce a TiO ₂ thin film.

This is air-dried at room temperature, heated to 450 ° C. (10 ° C./min) in an electric furnace, held at 450 ° C. for 30 minutes, and cooled to room temperature (−10 ° C./min), thereby allowing tin oxide coated transparent conductive A porous TiO ₂ thin film was formed and fixed on the porous glass. The film thickness of the porous TiO ₂ thin film obtained by this spin coating method was 15 ± 2 μm as a result of measurement using a surface shape measuring device (KEYENCE, VF-7500).

In addition, in the dye-sensitized solar cell, it has been reported that the photovoltaic property is improved by treating the porous TiO ₂ thin film used as the porous oxide semiconductor electrode with TiCl _4. The porous TiO ₂ thin film was treated with TiCl ₄ . The TiCl ₄ treatment was performed according to the following procedure.

1) First, it dropped approximately 0.5ml of TiCl ₄ aqueous solution (0.2 mol / dm ³⁾ to the porous TiO ₂ thin film surface, wet the porous TiO ₂ membrane surface evenly.
2) Next, in order to maintain this state, it is placed in a desiccator filled with water and left at room temperature for 15 hours.
3) Remove the electrode from the desiccator, wash the surface with water, put it in an electric furnace, raise the temperature to 450 ° C. at 10 ° C./min, heat to 450 ° C. for 30 minutes, and then lower the temperature to 10 ° C./min to room temperature. .

Porous fixation of the dye to the TiO ₂ electrode surface after 1 hour heating and drying the porous TiO ₂ electrode at 200 ° C., cooled to 75 ° C., it is a dye 5- (4-carboxyphenyl) -10, It was performed by immersing in a toluene / methanol solution (3 × 10 ⁻⁴ M) of 15,20-tris (4-trimethylsilylphenyl) porphyrin and refluxing for 1 hour.

<Production of dye-sensitized solar cell by modularization>
Using the porous TiO ₂ electrode obtained by immobilizing 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin obtained as described above, FIG. 3 and FIG. The dye-sensitized solar cell 200 having the configuration as shown was assembled, and the photovoltaic properties were measured. The spacer 203 is made of polyethylene, and the size of the opening 203A is 10 × 10 × 0.1 mm ³ . The electrolyte 108 was a 0.3 M LiI-0.015 MI ₂ acetonitrile: ethylene carbonate (2: 8) solution. Further, a counter electrode 109 having a tin oxide-coated transparent conductive glass surface with a platinum thin film formed by a sputtering method was used.

(Comparative example)
<Synthesis of porphyrin dye>
Benzaldehyde (5.5 mL, 54 mmol) and terephthalaldehyde acid (2.70 g, 18.0 mmol) were dissolved in propionic acid (300 mL), and pyrrole (5.0 mL, 72 mmol) was added dropwise while heating under reflux. This was refluxed for an additional hour and cooled to room temperature. The reaction mixture was concentrated to about 70 mL under reduced pressure, and water-methanol (1: 1, 100 mL) was added thereto and stirred. The precipitated solid was filtered by suction and dried under reduced pressure. A part (1.0 g) of the obtained solid (9.57 g) was separated by column chromatography (silica gel, the solvent was chloroform and then chloroform-methanol (95: 5)). The obtained black purple solid was separated again by column chromatography (silica gel, solvent was dichloromethane-chloroform-ethyl acetate-methanol (50: 45: 3.5: 1.5)), and 5- (4-carboxyphenyl) -10, 0.063 g of 15,20-triphenylporphyrin was obtained as a purple solid. The yield in terms of solid (9.57 g) obtained after the reaction is 5%.

<Result of identification>
The structure of 5- (4-carboxyphenyl) -10,15,20-triphenylporphyrin was identified by the following spectrum.
¹ H NMR (CDCl ₃ ): δ-2.81 (s, 2H), 7.73-7.78 (m, 9H), 8.20 (d, 6H, J = 6.4 Hz), 8.34 (d, 2H, J = 8.1 Hz), 8.50 (d, 2H, J = 8.1 Hz), 8.79 (d, 2H, J = 4.8 Hz), 8.84 (s, 4H), 8.86 (d, 2H, J = 4.8 Hz). ¹³ C NMR (CDCl ₃ ) : δ-118.5, 120.3, 120.5, 126.7, 127.7, 128.2, 129.6, 134.49, 134.52, 141.9, 147.0, 169.0. IR (KBr): 3450, 3320, 3060, 3020, 1730, 1690, 1610, 1470, 970, 800, 700 cm ^-1 .UV-Vis (λ _max (ε), CHCl ₃ ): 237 (22000), 419 (400000), 516 (16000), 550 (6800), 592 (4400), 647 nm (3800 ).

<Preparation of dye-sensitized solar cell>
Next, the photoelectrode in a photoelectric conversion element (solar cell) was produced like the Example, and the dye-sensitized solar cell was produced by modularizing. However, in this comparative example, instead of an electrode including a porous TiO ₂ electrode on which 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin is immobilized as a photoelectrode, A material including a porous TiO ₂ electrode on which 5- (4-carboxyphenyl) -10,15,20-triphenylporphyrin was immobilized was used.

(Evaluation)
<Photoelectric conversion characteristics>
Evaluation of the dye-sensitized solar cells obtained in the above-described Examples and Comparative Examples was performed by measuring the photovoltaic characteristics of the dye-sensitized solar cells under irradiation with simulated sunlight.
As a simulated solar light source, a halogen lamp with a dichroic mirror (HOYA-SCHOTT Co., Ltd., LH150) is used, and an optical fiber light guide (HOYA-SCHOTT Co., Ltd., FGR) is used from the photoelectrode side of the dye-sensitized solar cell. Photoirradiation was performed, and the photovoltaic properties were measured by measuring the open-circuit voltage (V _oc ) and short-circuit current (I _SC ) between the dye-fixed porous TiO ₂ electrode and the platinum sputter counter electrode during light irradiation.

The irradiation light has a wavelength distribution characteristic of approximately AM-1.5 and corresponds to an incident light intensity of 50 to 100 mWcm ⁻² . Note _{V OC} and with Advantest R820 digital multimeter connected via a personal computer and GPIB interface for the measurement of _{I SC,} record the time change of _{V OC} and _{I SC} in the personal _{computer, V OC} and _{I SC} is The value at a stable time was taken as the measurement result. The measurement results are shown in Table 1.

Table 1 As is apparent, the two despite changes little in V _OC between the dye, I _SC Dyes 5- (4-carboxyphenyl) -10,15,20-tris ( When 4-trimethylsilylphenyl) porphyrin was used, the value was about three times that when 5- (4-carboxyphenyl) -10,15,20-triphenylporphyrin was used. This result shows that when 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin is used as the dye, 5- (4-carboxyphenyl) -10,15,20 This shows that the photoelectric conversion efficiency is improved by about 200% compared to the case of using -triphenylporphyrin.

There is almost no difference in the absorbance in the visible light region of the porous TiO ₂ electrode on which the dye is immobilized, and 5- (4-carboxyphenyl) -10,15,20-tris (4-trimethylsilylphenyl) porphyrin is used as the dye. The improvement of photoelectric conversion efficiency when using Fluorine was achieved because the trimethylsilyl group, which is a functional group with high electron donating property, was introduced into the porphyrin dye, thereby realizing high efficiency of electron transfer from the dye to the metal oxide semiconductor. it is conceivable that.

  As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes are made without departing from the scope of the present invention. It can be changed.

It is a block diagram which shows roughly an example of the photoelectric conversion element of this invention. It is a figure which expands and shows the oxide semiconductor electrode vicinity of the photoelectric conversion element shown in FIG. It is an expanded block diagram which shows an example of the dye-sensitized solar cell of this invention. It is a sectional side view of the dye-sensitized solar cell shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Photoelectric conversion element 101 Photoelectrode 102 Transparent conductive substrate 103 Oxide semiconductor electrode 104 Transparent substrate 105 Transparent conductive layer 106 Oxide semiconductor fine particle 107 Sensitizing dye 108 Electrolyte 109 Counter electrode 110 Conductive substrate 111 Conductive layer 112 Catalyst layer 120 Partition wall 200 Dye-sensitized solar cell 203 Spacer 203A Spacer opening 205 Solder 207 Copper wire

Claims (4)

A porphyrin represented by the general formula (I): wherein one of R is a carboxyl group and three R are trimethylsilyl groups (—Si (CH ₃ ) ₃ ) .

  2. A photoelectric conversion element, wherein the porphyrin according to claim 1 is used as the sensitizing dye in a photoelectric conversion element in which a sensitizing dye is adsorbed to an optical semiconductor electrode using an oxide optical semiconductor. The photoelectric conversion element according to claim 2 , wherein the oxide optical semiconductor is at least one selected from titanium oxide, zinc oxide, and zirconium oxide. A dye-sensitized solar cell comprising the photoelectric conversion element according to claim 2 .

Images