TW201318247A - Dye for dye-sensitized solar cell, photoelectric conversion element including said dye, and dye-sensitized solar cell - Google Patents

Abstract

To provide a dye for dye-sensitized solar cells which is useful as a sensitizing dye for improving thermal durability, a photoelectric conversion element including the dye, and a dye-sensitized solar cell. Ru(4,4'-di(9-nonenyl)-2,2'-bipyridine)(4,4'- dicarboxy-2,2'-bipyridine)(NCS)2 is used as a sensitizing dye.

Description

Pigment for dye-sensitized solar cell, photoelectric conversion element using the same, and dye-sensitized solar cell

The present invention relates to a dye for a dye-sensitized solar cell for improving the heat durability of a dye-sensitized solar cell, a photoelectric conversion element using the dye, and a dye-sensitized solar cell.

In recent years, research and development of photoelectric conversion elements are active in order to solve the problem of global warming caused by the depletion of fossil fuels such as oil or natural gas or greenhouse gas, focusing on solar power generation using clean and safe natural energy. get on. At present, the 矽 photoelectric conversion element has been put into practical use to form a lanthanide solar cell, but it is difficult to spread and expand from the viewpoint of price or material supply. Therefore, research and development of solar cells using materials other than ruthenium are being carried out for the expansion of the popularity of solar cells, and it is a candidate for the next-generation solar cell of low price which is manufactured by inexpensive raw materials and simple processes. Looking forward to dye-sensitized solar cells.

For the dye-sensitized solar cell system, in the group of Professor Gratzel of the Lausanne University of Technology in Switzerland in 1991, a group of iodine-based electrolysis was sealed between a porous titanium oxide (TiO ₂ ) electrode and a counter electrode held by a ruthenium pigment. Liquid dye-sensitized solar cells have received much attention since they have been able to achieve conversion efficiencies of up to 10%. The characteristics of the dye-sensitized solar cell are low in cost of the raw material and the production surface, and it is also possible to design, for example, a high-color design and a high output under a fluorescent lamp. A dye-sensitized solar cell is a solar cell that generates electricity by a chemical reaction similar to the photosynthetic synthesis of a plant. By irradiation with visible light, the sensitizing dye absorbs light and becomes an excited state, and the excited sensitizing dye electrons are injected into the oxidized state. In the conduction band of the titanium semiconductor, the injected electrons move to the opposite electrode via the external electric portion, and the moving electrons are returned to the sensitizing dye by the ions in the electrolytic solution, and the electric energy is taken out by repeating such a process.

One of the problems suitable for the spread of the dye-sensitized solar cell is, for example, an improvement in thermal durability. The deterioration environmental factor of the dye-sensitized solar cell is indicated by the temperature, and the phenomenon of the pigment detachment of the electrode generated by the high temperature is one of the causes of the deterioration of the solar cell characteristics. In the past, many efforts have been made to improve the heat durability of dye-sensitized solar cells. For example, using K19 pigment (Ru(4,4'-dicarboxylic acid-2,2'-bipyridyl) (4,4'-bis(p-hexyloxystyryl)-2,2'-bipyridine) (NCS) ₂ ) as a sensitizing dye, using a 3-methoxypropionitrile solution containing 1-propyl-3-methylimidazolinium iodide, iodine, guanidinium thiocyanate and N-methylbenzimidazole as electrolysis Liquid, a nanocrystalline TiO ₂ dye-sensitized solar cell in which 1-mercaptophosphonic acid is co-grafted on the surface of the porous TiO ₂ film, after 1000 hours of thermal stress at 80 ° C The conversion efficiency of 8% or more has been reported (refer to Non-Patent Document 1).

In addition, the concentrating wiring protective layer of the wiring protective layer and the ionic liquid dye-sensitized solar cell produced by the moisture-resistant package which avoids moisture incorporation can reach 85 ° C, 85% RH, and 1000 hours. The durability evaluation item specified by JIS has been reported (refer to Non-Patent Document 2).

The sensitizing dye used in the dye-sensitized solar cell is modified to form a ruthenium dye containing a crosslinkable olefin group polymerizable on the porous TiO ₂ electrode, and the acetonitrile/third butanol mixed solution containing the ruthenium dye is coated. The TiO ₂ layer on the fluorine-doped tin oxide (FTO) substrate is added with methacrylic acid and a polymerization initiator azobisisobutyronitrile (AIBN) solution, and photopolymerization is carried out by ultraviolet irradiation to prepare the ruthenium pigment. Bonded to the surface of the porous TiO ₂ film by cross-linking with methacrylic acid, and further used to add polymethacrylic acid powder to an acetonitrile solution containing lithium iodide, lithium, and 4-tetrabutylpyridine The heat-gelled polymethacrylate-based gel electrolyte is used as an electrolyte solution, and is sealed between the electrodes, and the dye-sensitized solar cell which seals the injection port of the electrolyte by the sheet-like hot-melt sealing material is used. For the N3 dye (Ru(4,4'-dicarboxy-2,2'-bipyridine) ₂ (NCS) ₂ ) containing a crosslinkable olefin group, the conversion efficiency and storage life of 5% or more can be achieved. Long-term and improved durability, the papers reported above have been published (see non-patent Document 3). However, the durability test is basically a report of the deterioration condition at room temperature.

Further, in the dye-sensitized solar cell, an ionic liquid having a tetracyanate borate anion and an organic cation as a base material is used as an electrolyte solution, and the initial value of the conversion efficiency is retained after a heat history of 1000 hours at 80 °C. More than 90% have been reported (refer to Patent Document 1).

[Previous Technical Literature] [Non-patent literature]

[Non-Patent Document 1] Peng Wang, Cédric Klein, Robin Humphry-Baker, Shaik M. Zakeeruddin, Michael Grätzel, Applied Physics Letters 86, (2005) 123508

[Non-Patent Document 2] Arakawa, Yamaguchi, Okada, Matsui, Kitamura, Fujikura Technical News, 114, (2008 (2)), 48-53

[Non-Patent Document 3] KEN-YEN LIU, CHIAO-LING HSU, SHUN-HSING CHANG, JIAN-GING CHEN, KUO-CHUAN HO, KING-FU LIN, Jouranl of Polymer Science: Part A: Polymer Chemistry, 48, ( 2010), 366

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2009-527074

[Summary of the Invention]

As described above, the thermal durability of the conventional dye-sensitized solar cell is limited to 85 ° C, and is still insufficient in thermal durability as a solar cell product. Therefore, the improvement of thermal stability is One of the problems to overcome.

Therefore, the present invention has been made in view of the above circumstances, and an object of the invention is to provide a dye for a dye-sensitized solar cell for improving the durability of a thermal dye-sensitized solar cell, a photoelectric conversion element using the same, and dye sensitization. Solar cell.

In order to solve the above-mentioned problems, the present inventors have found that a novel ruthenium complex dye having a long alkyl group having a vinyl group introduced at the end thereof is synthesized as a sensitizing dye, and is not an organic solvent such as acetonitrile. Highly durable ionic liquids are used as electrolytes, which are higher than conventional ones. After heat treatment at a temperature in the range of 100 to 120 ° C to prepare a dye-sensitized solar cell, the heat durability is raised from a conventional 85 ° C to 120 ° C, and the present invention is finally completed based on such knowledge.

That is, the dye for a dye-sensitized solar cell of the present invention is composed of Ru(4,4'-bis(9-nonenyl)-2,2'-bipyridine) (4,4'-dicarboxy- 2,2'-bipyridyl) (NCS) ₂ is composed.

Moreover, the photoelectric conversion element of the present invention includes a transparent conductive substrate and a photoelectric conversion element which is a porous film formed on the transparent conductive substrate, and the porous film is a TiO which adsorbs the dye for the dye-sensitized solar cell. ₂ particles are composed.

Further, the dye-sensitized solar cell of the present invention uses the above-described photoelectric conversion element.

According to the present invention, the thermal durability of the dye-sensitized solar cell is rapidly increased by suppressing the detachment of the dye generated in a high temperature environment as compared with the conventional dye. Therefore, the present invention contributes greatly to the future spread of the dye-sensitized solar cell.

[Formation for implementing the invention]

Hereinafter, the present invention will be described in detail.

The pigment for dye-sensitized solar cells of the present invention is composed of Ru(4,4'-bis(9-nonenyl)-2,2'-bipyridine) (4,4'-dicarboxy-2,2' -Bipyridine) (NCS) ₂ (hereinafter, simply referred to as "SG1051 pigment") is expressed by the following formula.

Since the dye for the dye-sensitized solar cell is surrounded by the electrolytic solution, it is easily detached from the surface of the TiO ₂ electrode. However, since the dye of the present invention is firmly bonded to the surface of the porous TiO ₂ , it is produced in a high-temperature environment. Since the pigment detachment is small, a dye-sensitized solar cell excellent in thermal durability can be obtained. Further, the dye of the present invention can be combined with an electrolytic solution composed of a specific ionic liquid to be described later, and the dye can be further adsorbed on the electrode and heated in a specific temperature range to further improve the heat of the dye-sensitized solar cell. Durability.

A method for producing a dye for a dye-sensitized solar cell of the present invention will be described. The dye for dye-sensitized solar cell of the present invention uses dichloro(p-isopropyltoluene) ruthenium (II) as a starting material, and 4,4'-bis(9-nonenyl) is sequentially carried out. -2,2'-bipyridine, 4,4'-dicarboxy-2,2'bipyridine, sodium thiocyanate reaction. Also, the manufacture of the pigment The method is not limited to this.

The 4,4'-bis(9-nonenyl)-2,2'-bipyridine system can be prepared, for example, as follows. First, a solution of n-butyllithium in hexane is added to a solution of diisopropylamine in tetrahydrofuran at 0 to 5 ° C, stirred for 0.5 to 1.0 hour, and then added dropwise to 4,4'-dimethyl-2. A solution of 2'-bipyridyl in tetrahydrofuran. After the dropwise addition, the mixture was stirred at -70 to -60 ° C for 3 to 4 hours. Then, a solution of 9-pyridinium iodide in tetrahydrofuran was added at -78 to -60 ° C to react at the same temperature for 12 to 15 hours. Thereafter, it was cooled with methanol, and the obtained yellow-brown solution was poured into cold water, extracted with diethyl ether, and then diethyl ether was evaporated, and recrystallized from hexane to obtain 4,4'- Bis(9-decenyl)-2,2'-bipyridyl. Further, 9-decyl iodide may be produced by a known technique using an iodinated alcohol, for example, triphenylphosphine is added to a mixed solution of 9-nonen-1-ol of a starting material in diethyl ether/acetonitrile. , imidazole, and iodine are obtained by iodinating an alcohol.

Next, 4,4'-bis(9-decene) was added to a commercially available solution of [(p-isopropyltoluene)RuCl(μ-Cl)] ₂ in N,N-dimethylformamide (DMF). Base 2,2'-bipyridyl, stirred at 50-80 ° C for 0.5-2.0 hours under argon, then add commercially available 4,4'-dicarboxy-2,2'bipyridine to 100~ The mixture was heated and stirred at 140 ° C for 10 to 20 hours and reacted. Then, excess NH ₄ NCS was added to the reaction product, and the reaction was carried out at 120 to 140 ° C for 2 to 10 hours, and then the solvent DMF solution was evaporated by a rotary evaporator. Thereafter, excess NH ₄ NCS was removed with water, and the insoluble product was washed with water and diethyl ether, and then dried. The obtained crude product is dissolved in methanol, and purified by gel filtration chromatography (separation liquid: methanol or the like). In this way, a dye-sensitized solar cell excellent in thermal durability can be produced. Ru(4,4'-bis(9-nonenyl)-2,2'-bipyridyl) (4,4'-dicarboxy-2,2) of the pigment for dye-sensitized solar cells of the present invention can be obtained. '-bipyridyl) (NCS) ₂ .

The photoelectric conversion element of the present invention is produced by using the above-described dye, for example, by the following method.

First, a transparent conductive film substrate on which a transparent conductive film is formed on an electrode substrate is prepared. The electrode substrate is preferably light transmissive, and may be, for example, a plate or a film made of glass, ceramics, plastic or the like.

The transparent conductive film may, for example, be a tin oxide doped fluorine film (FTO film), a small amount of tin oxide added to the indium oxide film (ITO film), a tin oxide doped germanium film (ATO film), or oxidized. Tin and so on.

The transparent conductive substrate is produced by forming a transparent conductive film on one surface, both sides, or the entire surface of the electrode substrate by a spray pyrolysis method, a vapor deposition method, a sputtering method, an ion plating method, a hydrolysis method, or the like.

Then, a porous film is formed on the transparent conductive film of the transparent conductive substrate. The porous film is preferably an n-type metal oxide semiconductor film made of titanium oxide or the like, and particularly preferably a porous TiO ₂ film obtained by baking a TiO ₂ paste. In the TiO ₂ paste, TiO ₂ particles are added and mixed with an aqueous solvent to prepare a dispersion, and a viscosity increasing agent, a dispersing agent, or the like is added to the dispersion liquid, and the mixture is uniformly mixed and prepared.

Next, a method of forming a porous film will be described. The TiO ₂ paste is applied onto the transparent conductive film of the transparent conductive substrate by, for example, a doctor blade method, a doctor blade method, a spin coating method, a screen printing method, an electrophoresis method, a spray coating method, or the like, and then placed in the transparent conductive film. The electric furnace is baked at 300 to 700 ° C for 10 to 60 minutes in the atmosphere to form a porous film on the transparent conductive film. The porous film-based transparent conductive substrate and the dye together constitute a photoelectric conversion element. When the firing temperature is less than 300 ° C, the firing of the TiO ₂ particles is insufficient, so that the adsorption of the dye is inhibited, and high light conversion characteristics cannot be obtained. If the firing temperature exceeds 700 ° C, the transparent conductive substrate may be inferior. Further, when the firing time is less than 10 minutes, the sintering becomes insufficient, and if it exceeds 60 minutes, the grain growth is excessively performed by firing, and the specific surface area is lowered.

The porous film on the transparent conductive film is not only a single layer but also a multilayer structure of two or more layers. For example, when the porous film is two layers, the film of the first layer provided on the transparent conductive film of the transparent conductive substrate is formed by using the average particle diameter of the diameter when the projected area is converted into a circle as a primary particle. A transparent layer composed of 5 to 200 nm TiO ₂ particles is formed thereon with a light scattering layer composed of TiO ₂ particles having an average particle diameter of 100 to 600 nm. By forming such a two-layer structure of TiO ₂ film, the conversion efficiency can be further improved.

Then, the transparent conductive substrate on which the porous film is formed on the transparent conductive film is immersed in the dye solution, and the dye is adsorbed to the porous film to be fixed. The dye solution is obtained by dissolving the pigment of the present invention in a hydrocarbon such as hexane, octane, toluene or xylene, or an aliphatic alcohol such as methanol, ethanol, propanol or n-butanol, acetonitrile or propionitrile. a ketone such as a nitrile, acetone or methyl ethyl ketone; an ester such as ethyl acetate or butyl acetate; a carbonate such as diethyl carbonate or propylene carbonate; dimethyl carbonate or diethyl carbonate; Separate solvents such as phthalamides such as carbonates, lactones, dimethylformamide, dimethylacetamide, guanamines, dimethylammonium, cyclopentanthene, etc. Or such a mixed solvent to adjust. Preferably, an aliphatic alcohol or a nitrile can be used. The pigment concentration in the dye solution is 0.01 mM or more, preferably 0.1 to 10 mM. The impregnation of the transparent conductive substrate in the dye solution is carried out at 10 to 40 ° C for 1 to 24 hours. Further, by imparting ultrasonic vibration, the porous film can be improved in dye adsorption efficiency, and it can be immersed at room temperature for 5 to 60 minutes. The surface of the porous membrane on which the above dye is adsorbed is washed and dried. Thereby, a photoelectric conversion element having a light-transmissive transparent conductive substrate and a porous film formed on the transparent conductive substrate can be obtained, and the porous film is a TiO ₂ particle to which at least the pigment of the present invention is adsorbed. A photoelectric conversion element constructed.

The transparent conductive substrate is immersed in the dye solution, and after the dye of the present invention is adsorbed to the porous film, heat treatment is applied in a range of from 120 to 300 ° C, preferably from 150 to 300 ° C, for a period of from 0.5 to 60 minutes. Further, at least a part of the porous film is composed of a reactant obtained by mutually polymerizing the pigment of the present invention, and the heat durability can be further improved. This heat treatment can also be performed as a main seal or a final seal when a dye-sensitized solar cell is produced as will be described later. It is considered that the polymerization between the dyes of the present invention is carried out by the heat treatment described above, and the SG1051 dye is not removed from the state, and the main cause of the decrease in the characteristics of the dye-sensitized solar cell is reduced. Further, when the dye of the present invention is polymerized on a porous film, a polymerization reaction using a polymerization initiator is not required.

The photoelectric conversion element of the present invention has two terminal vinyl functional groups of a moderate length by the pigment of the present invention, and the pigment molecules or the dye are formed by bonding with the surface of the TiO ₂ particles, and are firmly adsorbed to the TiO ₂ particles. The pigment detachment generated in a high-temperature environment is greatly reduced compared to the conventional pigment, and thus the thermal durability is excellent. Further, since the polymerization reaction using the polymerization initiator for the adsorption of the porous film is an unnecessary dye, it can be easily produced. Further, by continuing to use the ruthenium dye detachment by the photoelectric conversion element, there is no need for a complicated step of returning to the original state. Therefore, the photoelectric conversion element of the present invention is very useful as a photoelectric conversion element such as a dye-sensitized solar cell.

Next, a method of producing a dye-sensitized solar cell using the above photoelectric conversion element will be described.

First, a transparent conductive substrate on which a transparent conductive film is formed on an electrode substrate is prepared, and a conductive film is formed on the transparent conductive film to form a counter electrode. The electrode substrate is preferably light transmissive, and may be, for example, a plate or a film made of glass, ceramics, plastic or the like.

The transparent conductive film may, for example, be a tin oxide doped fluorine film (FTO film), a small amount of tin oxide added to the indium oxide film (ITO film), a tin oxide doped germanium film (ATO film), or oxidized. Tin and so on.

The transparent conductive substrate is produced by forming a transparent conductive film on one surface, both sides, or the entire surface of the electrode substrate by a spray pyrolysis method, a vapor deposition method, a sputtering method, an ion plating method, a hydrolysis method, or the like.

The conductive film formed on the transparent conductive film may be a film made of, for example, platinum or carbon. The conductive film is formed by a vapor deposition method, a sputtering method, an ion plating method, a hydrolysis method, or the like. The thickness of the conductive film is generally several nm.

Then, the photoelectric conversion element and the counter electrode are separated by a specific interval. In the opposite state, the sealing material (main sealing material) is bonded to each other, and an electrolyte solution is injected between the electrodes to form an electrolyte layer. Finally, the sealing port of the electrolyte is sealed with a sealing material (final sealing material), and further, as needed The final sealing material is encapsulated by a cover material made of glass or the like. Thereby, a dye-sensitized solar cell was produced. The main seal member may, for example, be a hot melt material, an ultraviolet curable resin, a thermosetting resin, a glass frit or the like. In the present invention, in particular, the main sealing material composed of the hot-melt material is heated and sealed in a temperature range of 120 to 300 ° C, preferably 150 to 300 ° C for 0.5 to 60 minutes, and is heat-resistant. The point of sexual improvement is better. Specific examples of the main sealing material composed of the hot-melt material include a hot-melt gasket made of an ionic monomer resin (Surlyn 1702, trade name, thickness 25 μm, manufactured by DuPont), and heat of a polyethylene resin. Melt gasket (Bynel, trade name, thickness 25μm, manufactured by DuPont).

The electrolyte solution sealed between the photoelectric conversion element and the counter electrode is a redox pair of a supporting electrolyte composed of a cation such as lithium ion or an anion such as an iodide ion, and an iodine-iodine compound or a bromine-bromine compound, and a solvent. Mix to modulate. Examples of the solvent include water, alcohols, nitriles, ethers, esters, ketones, lactones, heterocyclic compounds, guanamines, nitromethane, halogenated hydrocarbons, dimethyl azine, and cyclopentane. a solvent or a mixed solvent of hydrazine, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolinone, a hydrocarbon, or the like, but in the present invention, it is preferably a tetraalkyl group. An ionic liquid of a pyridinium, an imidazolium borate, a quaternary ammonium salt or the like, and more preferably an imidazolium borate. In particular, 1-ethyl-3-methylimidazolium tetracyanide borate is preferred from the point of improvement in thermal stability. Ionic liquid system only The salt composed of positive and negative ions has a low melting point and is liquid at room temperature, and has no volatility, and is effective for preventing deterioration of characteristics of the dye-sensitized solar cell that passes over time. Particularly suitable electrolyte composition can be exemplified by 0.2 to 2 M of 1-ethyl-3-methylimidazolium iodide, 0.2 to 2 M of 1,3-dimethylimidazolium iodide, and 0.1 to 1 M of thiocyanate. Ester, 0.1~1M N-butylbenzimidazole, 1-ethyl-3-methylimidazolium tetracyanate solution containing 0.05~0.5M iodine. This electrolyte solution is excellent in thermal stability and is less likely to cause deterioration of the electrode.

After the photoelectric conversion element and the counter electrode are bonded to each other, the electrolyte solution is injected into the gap between the photoelectric conversion element and the counter electrode, for example, at least one of the photoelectric conversion element and the counter electrode is opened to the through hole (injection port), and the through hole is opened through the through hole. The electrolyte is injected, and after the injection, the through hole is sealed with a sealing material (final sealing material). In the other, a method of decompressing in a state of being immersed in an electrolytic solution and then releasing it to a normal pressure can be exemplified, whereby the electrolytic solution is easily filled in a space between the photoelectric conversion element and the counter electrode.

After the electrolyte is injected, the material of the sealing material (the final sealing material) that encapsulates the through-hole (injection port) may be, for example, a hot melt material, an ultraviolet curable resin, a thermosetting resin, or a glass medium.

In the dye-sensitized solar cell having such a structure, the dye of the present invention has two terminal vinyl functional groups of a moderate length, and the dye molecules or the dye are bonded to the surface of the TiO ₂ particles, and are firmly adsorbed to the TiO. ₂ particles, so it is excellent in thermal durability. Further, since the polymerization reaction using the polymerization initiator for the adsorption of the porous film is an unnecessary dye, it can be produced relatively easily. By continuing to use the photoelectric conversion element to detach the ruthenium pigment, there is no need for complicated steps of returning to the original state.

The dye-sensitized solar cell of the present invention is not a sandwich structure as described above, and can be formed into a complex structure such as a W-type accumulation structure, a Z-type accumulation structure, or a monolithic accumulation structure by a plurality of accumulations, and is accumulated by plural numbers. , can increase the output.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the examples.

[Production of Porous TiO ₂ Electrode]

The FTO glass substrate (LOFTec7, trade name, manufactured by Nippon Sheet Glass Co., Ltd.) with a FTO film-attached conductive glass substrate was cut into 25 mm × 75 mm, and washed with 50 mM hydrochloric acid for 5 minutes using the most ultrasonic wave, and washed with acetone. After 5 minutes, again, each of hydrochloric acid and acetone was washed for 15 minutes. After the washing was terminated, it was carefully rinsed with water and ethanol, and after drying, the residual organic matter was treated by a UV-O ₃ system for 18 minutes. Then, the FTO glass substrate after the UV-O ₃ treatment was placed in a 40 mM TiCl ₄ aqueous solution, and held at 70 ° C for 30 minutes, and then taken out and rinsed with water and ethanol to prepare an FTO glass substrate.

Then, a TiO ₂ paste (PST-30NRT, trade name, manufactured by Nikko Chemical Co., Ltd.) having a particle size of 20 to 30 nm was applied by screen printing on a FTO glass substrate, and dried and fired to form a transparent layer. This coating, drying, and baking operation was performed three times so that the film thickness of the transparent layer finally became 9 μm.

Then, a TiO ₂ paste having a particle size of 400 nm (PST-400C, trade name, manufactured by Nikkiso Chemical Co., Ltd.) was applied by screen printing on the transparent layer, and dried and fired to form a film thickness of 4 to 5 μm. Light scattering layer. Next, the thus prepared TiO ₂ electrode was placed in an electric furnace, and dried at 325 ° C for 5 minutes, at 375 ° C for 5 minutes, at 450 ° C for 15 minutes, and finally at 500 ° C for 15 minutes, and dried to form an FTO glass substrate. A porous TiO ₂ film composed of _two layers. TiO ₂ removed from the electric furnace electrodes, again, TiO ₂ electrode placed in an aqueous solution 40mM of TiCl _4, for 30 minutes, taken out after rinsing with water and ethanol, to the use of hydrochloric acid was immersed in 50Mm stored at 70 ℃. The TiO ₂ electrode taken out from hydrochloric acid at the time of use was washed with ethanol in ethanol, and then fired at 500 ° C for 30 minutes using a heat gun. After air cooling to 80 ° C, the fired TiO ₂ electrode was immersed in a mixed solution of 0.3 mM SG1051 pigment in acetonitrile / valeronitrile (1:1) at room temperature for 1 hour to carry out adsorption of the dye. After the dye was adsorbed, the electrode was pulled up from the solution, and the unadsorbed pigment was removed, and washed with acetonitrile. Thus, a porous TiO ₂ electrode in which SG1051 pigment was supported on TiO ₂ particles was produced.

[Pt pole production]

FTO glass (LOF Tec7, trade name, manufactured by Nippon Sheet Glass Co., Ltd., thickness mm) was cut into a size of 12 mm × 12 mm. A through hole having a diameter of 1 mm was opened from a corner of the FTO glass at a position of 8 mm × 8 mm by a manual drilling machine (U-hobby, trade name, manufactured by Urawa Co., Ltd.). The glass of the glass sheet or the like was removed from the FTO glass which opened the through hole, and washed with water for 10 minutes. Then, it was washed with 50 mM hydrochloric acid for 5 minutes, rinsed with acetone, and washed with acetone for 5 minutes. After the washing, the cells were again washed with 50 mM hydrochloric acid and acetone for 15 minutes. The FTO glass which was washed and washed was carefully washed with water, and then stored until immersed in 50 mM hydrochloric acid. The FTO glass taken out from hydrochloric acid during use is placed in a dust-free box. After drying naturally, a drop of H ₂ PtCl ₆ solution (containing 2 mg of Pt in 1 ml of ethanol) is applied to the FTO glass, using a heat gun. The mixture was heated at 400 ° C for 15 minutes to prepare a Pt counter electrode having Pt coated with FTO glass of 0.5 to 5 mm.

[Production of dye-sensitized solar cell]

The porous TiO ₂ electrode (size: 0.25 cm ² ) and the Pt counter electrode are brought into contact with each other, and a hot melt gasket composed of an ionic monomer resin is sandwiched between them (Surlyn 1702, trade name, thickness 25 μm, DuPont) As a sealing material (main sealing material), it is heated at a temperature of 250 ° C for 1 to 3 minutes to adhere the porous TiO ₂ electrode to the Pt counter electrode. The sealing material has a width of 1 mm, and the opening is formed to be ₂ mm larger than the TiO ₂ electrode.

The Pt-to-pole through-hole was sealed by heating the other sealing material at 250 ° C for 1 to 3 minutes using a heat sealer. After the sealing, the through hole is opened in the sealing material using a needle. Then, one drop of the electrolyte was dropped on the through hole, and placed in a small vacuum chamber, and the electrolyte was placed in the cell by the reverse vacuum. Finally, the through-holes were sealed with a hot-melt ionic monomer at a temperature of 250 ° C for 1 to 3 minutes, and further coated with a cover glass to prepare a sandwich-type dye-sensitized solar cell.

Further, in the mounting of each measurement described later, in order to remove the TiO ₂ film of the joint portion, the electrical contact was good, and the outer end of the FTO glass was slightly cut with a sandpaper or a film. The solder is applied to both of the FTO electrodes. The position of the solder is from the end of the aforementioned gasket to the outside of 1 mm, that is, from the end of the TiO ₂ layer to the outside of 4 mm. Further, in order to reduce the scattered light, a plastic type mask is attached to the assembled cell. It is attached to a filter sheet of an anti-reflection film (Arctop, trade name, Asahi Glass Co., Ltd.).

0.75 M of 1-ethyl-3-methylimidazolium iodide, 0.75 M of 1,3-dimethylimidazolium iodide, 0.2 M of guanidinium thiocyanate, 0.2 M of N was used in the above electrolyte. - Butylbenzimidazole, 1-ethyl-3-methylimidazolium tetracyanate solution containing 0.1 M iodine.

[heat durability test]

The dye-sensitized solar cell produced by using the SG1051 dye was placed in a 120 ° C oven (AS ONE) to study the photoelectric characteristics (open circuit voltage (V), short-circuit current density of the solar cell). (short circuit current density) (mA/cm ² ), fill factor, and efficiency (%) change with time, and evaluate the thermal durability of the dye-sensitized solar cell. ) is determined by the energy of the open voltage × short-circuit current × fill factor / incident light. Also, Z907 pigment Ru (4,4'-dicarboxylate-2,2'-bipyridine) (4,4) '-Dimercapto-2,2'-bipyridyl) (NCS) ₂ ) A dye-sensitized solar cell produced by the same procedure as described above was replaced with the SG1051 dye as a comparative control. The results of these are shown in Figures 1 to 4. Fig. 1 is a graph showing changes in the open voltage of a dye-sensitized solar cell with respect to passage of time. Fig. 2 is a graph showing changes in the short-circuit current density of the dye-sensitized solar cell with respect to the passage of time. Fig. 3 is a graph showing changes in the filling factor of the dye-sensitized solar cell with respect to the passage of time. Fig. 4 is a graph showing changes in the conversion efficiency of the dye-sensitized solar cell with respect to the passage of time.

[Measurement of Photoelectric Characteristics]

The photoelectric characteristic of the dye-sensitized solar cell is a current value and an electrode when the load between the electrodes of the dye-sensitized solar cell is changed by using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) equipped with a 450 W xenon lamp. The current-voltage curve obtained by the voltage mapping is measured. In order to suppress the error of pseudo-light and AM1.5 to 2% or less, a reference Si photodiode (manufactured by Spectrometer Co., Ltd.) equipped with an IR intercept filter was used, and the output of the pseudo-light was 100 mW/cm ² . The current-voltage curve is applied to a dye-sensitized solar cell by an external bias voltage, and is produced by measuring the photocurrent generated by a digital power meter (ADCMT). The voltage step is set at 10 mV. Moreover, the delay time of the photocurrent is set to 500 ms.

[Evaluation of Photoelectric Characteristics]

As can be seen from the results shown in Fig. 1 to Fig. 4, the dye-sensitized solar cell system using the Z907 dye and the SG1051 dye, respectively, after about 30 hours from the start of heating, shows the same photoelectric characteristics, but if it exceeds 200 hours, the Z907 pigment is used. The performance of the prepared dye-sensitized solar cell is lowered. Further, in the SG1051 dye, if it is about 500 hours, it can be operated at 120 °C. From these results, it was confirmed that the SG1051 pigment exhibits superior thermal durability than the Z907 pigment. It is considered that the Z907 pigment system is detached from the porous TiO ₂ film in a high temperature environment of 120 ° C, but the SG1051 pigment is polymerized with each other, and even if a part of the pigment is detached from the porous TiO ₂ film, the pigments are also linked, so that the porous material cannot be separated from the porous material. The TiO ₂ film was completely detached.

[Pigment adsorption test]

The N719 pigment (RuL ₂ (NCS) 2.2 TBA: L = _2, 2'-bipyridyl-4,4'-dicarboxylate, TBA = tetrabutylammonium), Z907 pigment, SG1051 The porous TiO ₂ electrode of the dye was measured for the absorbance before and after the treatment with a sodium hydroxide aqueous solution (or aqueous sodium hydroxide solution and acetonitrile), and the adsorption strength of each of the dyes and the porous TiO ₂ electrode was comparatively investigated. The absorbance measurement of the TiO ₂ electrode was carried out by irradiating a monochromatic light having a wavelength (380 to 800 nm) with an absorbance measuring instrument and measuring the reflection of the monochromatic light.

The absorbance of the TiO ₂ electrode was measured. If the absorbance was decreased, the pigment was detached, and the adsorption strength of the dye and the porous TiO ₂ electrode was compared depending on the degree of change in absorbance. Further, sodium hydroxide is an effective reagent for separating the dye from the surface of TiO ₂ .

[N719 adsorption of pigment]

The TiO ₂ electrode before dye adsorption (1 cm × 1 cm) prepared by the same method as described above was immersed in a mixed solution of acetonitrile/t-butanol (1:1 (volume ratio)) containing 0.5 mM of the N719 dye at 20 °C. For 24 hours, a porous TiO ₂ electrode having a N719 pigment was prepared on a porous TiO ₂ film. Thereafter, the absorbance of the TiO ₂ electrode was measured. Then, after immersing in a 0.1 M sodium hydroxide solution, it was washed with water, and the absorbance of the dried TiO ₂ electrode was measured. The impregnation system of the sodium hydroxide solution was carried out for 30 seconds. The results are shown in Fig. 5 (the horizontal axis is the wavelength, the unit is nm, and the vertical axis is the absorbance).

[Adsorption of Z907 pigment]

In a mixed solution of acetonitrile/t-butanol (1:1 (volume ratio)) containing 0.3 mM of Z907 pigment, the TiO ₂ electrode before dye adsorption (1 cm × 1 cm) prepared by the same method as described above was immersed at room temperature. 20 hours, ruthenium was produced on a porous TiO ₂ film to hold a porous TiO ₂ electrode of Z907 pigment. Thereafter, the absorbance of the TiO ₂ electrode was measured. Then, after immersing in a 0.1 M sodium hydroxide solution, it was washed with water, and the absorbance of the dried TiO ₂ electrode was measured. The impregnation system of the sodium hydroxide solution was carried out for 30 seconds. The results are shown in Fig. 6 (the horizontal axis is the wavelength, the unit is nm, and the vertical axis is the absorbance).

[Adsorption power of SG1051 pigment]

In a mixed solution of acetonitrile/t-butanol (1:1 (volume ratio)) containing 0.3 mM of SG1051 pigment, the TiO ₂ electrode before dye adsorption (1 cm × 1 cm) prepared by the same method as described above was immersed at room temperature. 1 hour, ruthenium was prepared on a porous TiO ₂ film to hold a porous TiO ₂ electrode of SG1051 pigment. Thereafter, the absorbance of the TiO ₂ electrode was measured. Then, after immersing in a 0.1 M sodium hydroxide solution, it was washed with water, and the absorbance of the dried TiO ₂ electrode was measured. The impregnation system of the sodium hydroxide solution was carried out for 30 seconds. Further, after the immersion in the sodium hydroxide solution, the mixture was washed with acetonitrile, and the absorbance of the dried TiO ₂ electrode was measured. The results are shown in Fig. 7 (the horizontal axis is the wavelength, the unit is nm, and the vertical axis is the absorbance).

[Adsorption of SG1051 pigment heated at 125 ° C]

The TiO ₂ electrode before dye adsorption (1 cm × 1 cm) prepared by the same method as described above was immersed in a mixed solution of acetonitrile/t-butanol (1:1 (volume ratio)) containing 0.3 mM of the SG1051 dye at 20 °C. 1 hour, ruthenium was prepared on a porous TiO ₂ film to hold a porous TiO ₂ electrode of SG1051 pigment. Thereafter, the TiO ₂ electrode was heated at 125 ° C for 1 minute to measure the absorbance of the TiO ₂ electrode. Then, after immersing in a 0.1 M sodium hydroxide solution, it was washed with water, and the absorbance of the dried TiO ₂ electrode was measured. The impregnation system of the sodium hydroxide solution was carried out for 30 seconds. Further, after the immersion in the sodium hydroxide solution, the mixture was washed with acetonitrile, and the absorbance of the dried TiO ₂ electrode was measured. The results are shown in Fig. 8 (the horizontal axis is the wavelength, the unit is nm, and the vertical axis is the absorbance).

[Adsorption of SG1051 pigment heated at 250 ° C]

In a mixed solution of acetonitrile/t-butanol (1:1 (volume ratio)) containing 0.3 mM of SG1051 pigment, the TiO ₂ electrode before dye adsorption (1 cm × 1 cm) prepared by the same method as described above was immersed at room temperature. 1 hour, ruthenium was prepared on a porous TiO ₂ film to hold a porous TiO ₂ electrode of SG1051 pigment. Thereafter, the TiO ₂ electrode was heated at 250 ° C for 1 minute to measure the absorbance of the TiO ₂ electrode. Then, after immersing in a 0.1 M sodium hydroxide solution, it was washed with water, and the absorbance of the dried TiO ₂ electrode was measured. The impregnation system of the sodium hydroxide solution was carried out for 30 seconds. Further, after the immersion in the sodium hydroxide solution, the mixture was washed with acetonitrile, and the absorbance of the dried TiO ₂ electrode was measured. The results are shown in Fig. 9 (the horizontal axis is the wavelength, the unit is nm, and the vertical axis is the absorbance).

[Evaluation of pigment adsorption]

From the results shown in Fig. 5 to Fig. 9, it is understood that the SG1051 pigment is different from the N719 pigment or the Z907 pigment, and does not desorb in the sodium hydroxide solution, but thereafter, if it is washed with an organic solvent (acetonitrile), the SG1051 pigment Department is detached. Further, it was found that the SG1051 dye was polymerized by heating at 250 ° C for one time before washing with a sodium hydroxide solution and an organic solvent (acetonitrile), and the SG1051 dye was not separated. Since the SG1051 pigment of the present invention is strongly adsorbed to the porous TiO ₂ electrode, the pigment detachment of the main factor of the deterioration of the characteristics of the dye-sensitized solar cell is small, and therefore, the heat durability of the solar cell as a dye-sensitized solar cell can be confirmed. Sexual pigments are very useful.

Fig. 1 is a graph showing changes in the open voltage of a dye-sensitized solar cell with respect to passage of time.

Fig. 2 is a graph showing changes in short-circuit current density of a dye-sensitized solar cell with respect to passage of time.

Fig. 3 is a graph showing changes in the filling factor of the dye-sensitized solar cell with respect to the passage of time.

Fig. 4 is a graph showing changes in the conversion efficiency of the dye-sensitized solar cell with respect to the passage of time.

Fig. 5 is a graph showing the absorbance of a porous TiO ₂ electrode in which a N719 dye is supported on a porous TiO ₂ film, wherein the horizontal axis represents a wavelength and the unit is nm, and the vertical axis represents absorbance.

Fig. 6 is a graph showing the absorbance of a porous TiO ₂ electrode in which a Z907 dye is supported on a porous TiO ₂ film, wherein the horizontal axis represents a wavelength and the unit is nm, and the vertical axis represents absorbance.

Fig. 7 is a graph showing the absorbance of a porous TiO ₂ electrode in which a SG1051 dye is supported on a porous TiO ₂ film, wherein the horizontal axis represents a wavelength and the unit is nm, and the vertical axis represents absorbance.

Fig. 8 is a graph showing the absorbance of a porous TiO ₂ electrode in which a SG1051 dye heated at 125 ° C is supported on a porous TiO ₂ film, wherein the horizontal axis represents a wavelength and the unit is nm, and the vertical axis represents absorbance.

Fig. 9 is a graph showing the absorbance of a porous TiO ₂ electrode in which a SG1051 dye heated at 250 ° C is supported on a porous TiO ₂ film, wherein the horizontal axis represents a wavelength and the unit is nm, and the vertical axis represents absorbance.

Claims (6)

A dye for dye-sensitized solar cell, which is composed of Ru(4,4'-bis(9-nonenyl)-2,2'-bipyridine) (4,4'-dicarboxy-2,2' -bipyridine) (NCS) ₂ is composed. A photoelectric conversion element comprising a transparent conductive substrate and a photoelectric conversion element formed on the transparent conductive substrate, wherein the porous film is a dye-sensitized solar cell adsorbed as in the first aspect of the patent application It is composed of TiO ₂ particles of pigment. A photoelectric conversion element comprising a transparent conductive substrate and a photoelectric conversion element formed on a porous film formed on the transparent conductive substrate, wherein at least a part of the porous film is formed so as to adsorb the dye according to Item 1 of the patent application scope The sensible solar cell pigment is composed of TiO ₂ particles of a reaction product obtained by heat treatment at 120 to 300 ° C. A dye-sensitized solar cell using the photoelectric conversion element of the second or third aspect of the patent application. A dye-sensitized solar cell according to claim 4, which contains an ionic liquid having iodine. A dye-sensitized solar cell according to claim 5, wherein the ionic liquid is 1-ethyl-3-methylimidazolium tetracyanate.