JP6687942B2 - Method for manufacturing dye-sensitized solar cell - Google Patents

Description

  The present invention relates to a method for manufacturing a dye-sensitized solar cell, and more particularly to a method for manufacturing a dye-sensitized solar cell including a solid electrolyte layer.

  In recent years, from the viewpoint of global environmental problems such as global warming, solar cells that can convert solar energy, which is a clean energy source that replaces fossil fuels, into electric energy have attracted attention.

  The solar cells currently put into practical use are single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide. However, in these inorganic solar cells, for example, silicon solar cells, there is a problem that the purity is required to be very high, the refining process is complicated, the number of processes is large, and the manufacturing cost is high.

  On the other hand, as a new type of solar cell, a dye-sensitized solar cell was proposed by the group of Gretzel et al. In 1991, and is expected as a cheaper and more efficient solar cell. The Gretzell cell includes a porous semiconductor layer such as titanium oxide carrying a sensitizing dye and an electrolyte layer between a transparent electrode and a counter electrode formed on two light-transmitting substrates such as glass. Sunlight enters from the transparent substrate, passes through the transparent electrode, reaches the semiconductor layer, and excites the sensitizing dye. The excited electrons generated move to the transparent electrode via the semiconductor layer, then return to the counter electrode via the external electric circuit, and are carried by the ions in the electrolyte layer in the battery to return to the dye in the oxidized state. . By repeating the electron transfer that begins with the generation of excited electrons of the dye by such sunlight, sunlight energy is converted into electrical energy.

As the electrolyte layer, for example, a liquid layer using an electrolyte such as an iodide salt and a liquid carrier such as an acetonitrile / ethylene carbonate mixed solution containing a redox couple such as I ⁻ / I ₃ ⁻ is mainly used. However, there is a problem that the liquid carrier leaks from the solar cell or volatilizes.

  Therefore, a dye-sensitized solar cell including a solid electrolyte layer instead of the liquid electrolyte layer has been proposed. Among them, those using an electrolyte such as an imidazolium salt are attracting attention because of their stability and high conversion efficiency. For example, 1-methyl-3-acetylimidazolium iodide (Non-patent document 1), 1-propargyl-3-methylimidazolium iodide or 1-propargyl-1-methylpiperidinium iodide (Non-patent document 2). , Bis (N-pyrrolidinium) dibromide (Non-Patent Document 3) is used as a solid electrolyte, and an energy conversion efficiency (η) of about 2 to 6% is achieved.

Yong Zhao et al., Chem. Mater., 2008, 20, pp. 6022-6028 Hong Wang, et al., J. Am. Chem. Soc., 2013, 135, 12627-12633. Tong He, et al., ACS Appl. Mater. Interface, 2015, 7, 21381-21390

  However, there are some problems in the method of forming the solid electrolyte layer. First, in Non-Patent Documents 1 and 2, the electrolyte is dissolved in a solvent to form a solution, and the solution is dropped on the porous semiconductor layer on a hot plate, and then the solvent is dried. According to this method, it is necessary to repeat dropping and drying a number of times until the pores in the porous semiconductor layer are filled, and it is necessary to finally dry in a vacuum for one day or more, which is very difficult. take time. Further, in Non-Patent Document 3, after crushing a mixture of a solid electrolyte and an additive onto an electrode by knife coating, a heat seal film is formed between the counter electrode and the electrode on which a semiconductor layer is formed. It is made by hot pressing (0.18 MPa, 135 ° C., 35 seconds) while sandwiched as a spacer. Here, for coating, not only must the solid be pulverized into powder, but it must be dispersed in some medium to form a fluid paint. Further, it is not easy to press the powder into the porous semiconductor layer uniformly by hot pressing.

  Therefore, an object of the present invention is to provide a method for producing a solid electrolyte layer which is quicker and easier and suitable for practical use.

That is, the present invention is as follows.
A method for producing a dye-sensitized solar cell comprising a porous semiconductor layer carrying a sensitizing dye and a solid electrolyte layer at least between a pair of electrodes,
(1) a step of forming a porous semiconductor layer carrying a sensitizing dye,
(2) the porous semiconductor layer, you solidification step to applied by liquefaction a mixture comprising at least an electrolyte redox pair at a temperature of 70 ° C. to 210 ° C., and (3) The applied mixture as engineering, including the following,
(3-1) A step of maintaining the porous semiconductor layer to which the mixture has been applied for a predetermined time at a temperature equal to or lower than the temperature at which the liquefaction of step (2) was performed,
(3-2) a step of solidifying the mixture,
Including the method.

  Since the method of the present invention is applied to the semiconductor layer by liquefying a mixture containing an electrolyte or the like by heat and applying the mixture to the semiconductor layer, it is much more difficult than the method described in Non-Patent Documents 1 and 2 in which the solution is repeatedly dropped and dried. The electrolyte layer can be formed very quickly. Further, it is simply applied by liquefying the electrolyte or the like and dropping it from the top of the porous semiconductor layer, or spraying the electrolyte or the like onto the porous semiconductor layer, or placing it on the porous semiconductor layer and melting it. Since it is good, it is significantly simpler than the method described in Non-Patent Document 3, and is easily implemented on an industrial scale. Furthermore, it is not necessary to use a solvent for dissolving the electrolyte or the like, or a medium for forming a paint.

It is a schematic diagram showing an example of the structure of the dye-sensitized solar cell in the present invention. It is the schematic which shows the other example of the structure of the dye-sensitized solar cell in this invention. It is a schematic diagram showing an example of a manufacturing method of a dye-sensitized solar cell in an example.

  FIG. 1 is a diagram showing an example of the structure of the dye-sensitized solar cell in the present invention. The dye-sensitized solar cell includes at least a porous semiconductor layer 3 and a solid electrolyte layer 4 between a transparent electrode 2 and a counter electrode 6. The transparent electrode 2 is made of, for example, a transparent conductive film formed on one surface of the transparent substrate 1. The counter electrode 6 is formed of, for example, a counter electrode conductive layer formed on one surface of the counter electrode substrate 5 on the transparent electrode 2 side. A sensitizing dye (not shown) is carried on the porous semiconductor layer 3. Although the solid electrolyte layer 4 is shown as a layer above the porous semiconductor layer 3 in the drawing, it also penetrates and exists inside the porous semiconductor layer 3. In the present invention, “solid state” means a state of being non-fluid in the temperature range in which the dye-sensitized solar cell is used, and includes a plastic body such as a paste and a semi-solid state. Further, in the configuration of FIG. 1, the sealing portions 7 are provided on both side surface portions of the solar cell, but in the present invention, the electrolyte layer is a solid state, and thus is not an essential component. The sealing portion 7 may be provided with a spacer between the transparent substrate 1 and the counter electrode substrate 5.

  FIG. 2 is a diagram showing another example of the structure of the dye-sensitized solar cell of the present invention, which is a configuration that can be adopted because the electrolyte is solid. That is, the configuration of FIG. 2 does not include the counter electrode substrate 5 of FIG. 1, but the counter electrode 6 made of, for example, platinum covers the solid electrolyte layer 4 and the side surface of the porous semiconductor layer 3 and is terminated on the transparent substrate 1. . Then, the protective layer 8 covers the side surface of the porous semiconductor layer 3 and the surface of the counter electrode 6 to protect the dye-sensitized solar cell from scratches, contamination, and the like.

The method of the present invention is a method for producing a dye-sensitized solar cell comprising at least a porous semiconductor layer carrying a sensitizing dye and a solid electrolyte layer between a pair of electrodes as described above, which comprises: Process:
(1) a step of forming a porous semiconductor layer carrying a sensitizing dye,
(2) a step of liquefying and applying a mixture containing at least an electrolyte and a redox couple at a temperature of 70 ° C. to 210 ° C. to the porous semiconductor layer, and (3) a step of solidifying the applied mixture. ,
including.
The step (1) can be performed by a known method, and details will be described later. In step (2), liquefaction of the mixture containing at least the electrolyte and the redox couple (hereinafter sometimes referred to as “electrolyte mixture”) is performed by heating one of the electrolyte and the redox couple even if they are melted by heating. The other may be dissolved in the liquefied product. Here, "liquefaction" includes not only a completely liquid state but also a partially fluidized state. The "mixture" includes not only a homogeneous product but also a heterogeneous product in a simply combined state. The liquefaction means is not particularly limited, and for example, the electrolyte placed in a container is heated on a hot plate set at a temperature of 70 ° C. to 210 ° C. or in a constant temperature bath. Alternatively, light or electromagnetic waves such as microwaves may be applied, ultrasonic waves may be applied, or a plurality of these means may be combined for fluidization.

  The electrolyte mixture may be fluidized at a temperature of 70 ° C to 210 ° C to such an extent that it can penetrate into the porous semiconductor layer. Those in which the electrolyte mixture fluidizes at a temperature lower than the lower limit value may leak when the temperature rises during the operation of the dye-sensitized solar cell. On the other hand, if the fluidizing temperature exceeds the above upper limit, the sensitizing dye may deteriorate due to thermal decomposition or the like when applied to the semiconductor layer. Preferably, the electrolyte has a melting point, that is, a temperature at which a phase transition from a solid or semi-solid state to a liquid state under atmospheric pressure is 70 to 210 ° C, preferably 80 ° C to 180 ° C, more preferably 85 ° C to 160 ° C. Stuff used. The melting point can be measured by a known method such as thermal analysis, and the temperature may vary. Alternatively, a combination of electrolytes having a temperature in the above range due to a melting point decrease by using a mixture of a plurality of electrolytes may be used.

  Examples of the electrolyte include ammonium salts, amine halogen salts, pyridinium salts, piperidinium salts, imidazolium salts, phosphonium salts, sulfoxonium salts, and mixtures thereof having a melting point in the above temperature range. Examples of the anion in the salt include a halogen anion, a sulfide ion, and a polysulfide ion. Of these, a halogen anion is preferable, and an iodine anion is most preferable.

As the ammonium salt, acetylcholine iodide (161 to 164 ° C), acetylthiocholine iodide (205 to 210 ° C), butyrylcholine iodide (85 to 89 ° C), butyrylthiocholine iodide (171 to 174 ° C), Propionyl thiocholine iodide (200-202 ° C), benzyltriethylammonium iodide (168-173 ° C), tetra-n-butylammonium iodide (141-143 ° C), trimethylphenylammonium iodide (175 ° C), the following formula (1-tert-Butoxycarbonyl-7-azaindole-3-methyl) trimethylammonium iodide (138 to 143 ° C.), tetramethylammonium iodide (> 300 ° C.), tetraethylan represented by (1) Pyridinium iodide (> 300 ° C.) are exemplified. The values in parentheses are melting points under atmospheric pressure.

  Examples of the amine halogenate include butylamine hydrochloride (169 to 173 ° C) and benzylamine hydrochloride (176 to 180 ° C).

  As the pyridinium salt, 1-amino-2-methylpyridinium iodide (160 to 162 ° C.), 1-aminopyridinium iodide (159 to 161 ° C.), 2-chloro-1-methylpyridinium iodide (about 200 ° C.) , 1-ethylpyridinium iodide (97 ° C.) and 1-propargyl-3-pyridinium iodide (80 ° C.).

  Examples of the piperidinium salt include 1-propargyl-3-piperidinium iodide (80 ° C.).

As the imidazolium salt, 1,2-dimethyl-3-propylimidazolium iodide (abbreviation: CIM10P, formula (2), 72 to 74 ° C.), 1,3-dimethylimidazolium iodide (abbreviation: DMI, formula) (3), 92 ° C), 1-ethyl-3-methylimidazolium iodide (abbreviation: EMI, formula (4), 77.5-79 ° C), 1-methyl-3-acetylimidazolium iodide (formula (5), 188 to 189 ° C.) and 1-propargyl-3-methylimidazolium iodide (formula (6), 100 ° C.).

  Examples of the phosphonium salt include ethyltriphenylphosphonium iodide (164 to 170 ° C), isopropyltriphenylphosphonium iodide (194 to 197 ° C), and methyltriphenoxyphosphonium iodide (141 to 145 ° C).

Examples of sulfoxonium salts include trimethylsulfoxonium iodide (208 to 212 ° C.).

  Of these salts, pyridinium, piperidinium, and imidazolium iodides are preferable, and imidazolium iodides are more preferably used.

As the redox couple, those generally used in dye-sensitized solar cells may be used. Examples thereof include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, Fe ²⁺ / Fe ³⁺ system, quinone / hydroquinone system, and the like. Combination of metal iodide such as lithium iodide, potassium iodide, calcium iodide and iodine, tetraalkylammonium salt such as tetraethylammonium iodide, tetrapropylammonium iodide, tetrabutylammonium iodide, tetrahexylammonium iodide And iodine, as well as a combination of bromine with a metal bromide such as lithium bromide, sodium bromide, potassium bromide, calcium bromide. Of these, the I ⁻ / I ₃ ⁻ system is particularly preferable. The concentration of the redox couple in the electrolyte mixture is 1 to 90, preferably 5 to 50 wt%, and more preferably 5 to 15 wt% of oxidant, for example, I ₃ ⁻ .

  The electrolyte mixture may contain additives such as conventionally used organic basic compounds. As examples of the additive, nitrogen-containing aromatic compounds such as pyridine, quinoline, imidazole, and triazole, which have a melting point of 100 ° C. or higher, are preferable. The concentration of the additive in the electrolyte mixture is about 1 to 10 wt%.

  The porous semiconductor layer 3 to which the liquefied electrolyte mixture is applied is provided, for example, in a form formed on the transparent conductive film 2 on the transparent substrate 1 and heated so that the electrolyte mixture does not solidify. It is placed on a hot plate or in a constant temperature bath. The heating may be at a temperature at which the applied electrolyte mixture does not solidify. The temperature does not have to be the same as the temperature at which the electrolyte mixture is melted, and is preferably as low as possible in order to prevent thermal deterioration of the sensitizing dye. The method of applying the liquefied electrolyte mixture to the porous semiconductor layer 3 is not limited, and it can be dropped by a dispenser or the like, sprayed by a spray or the like, applied by various coaters, or printed. At this time, it is preferable to heat the dispenser or the like so as not to solidify the electrolyte mixture, or to use a device provided with a heating means.

  Alternatively, the solid electrolyte mixture may be placed directly on the heated porous semiconductor layer, and the electrolyte mixture may be melted and allowed to penetrate into the porous semiconductor layer at the same time. At this time, in order to promote the permeation of the electrolyte mixture into the semiconductor layer, pressure may be applied or the entire transparent substrate may be vibrated. The amount of the electrolyte mixture applied may be an amount sufficient to fill the space in the porous semiconductor layer and to fill the space between the counter electrode in the configuration of FIG. In the case of the structure shown in FIG. 2, the amount may be such that the unevenness on the surface of the porous semiconductor layer is leveled by the graded mixture to obtain a flat surface. After the application, the excess electrolyte mixture may be wiped off with a cotton swab or the like to be flattened. Preferably, a counter electrode is formed on the flat surface by vapor deposition or the like.

The porous semiconductor layer may be provided as a cell in which the transparent substrate 1 and the counter electrode substrate 5 are opposed to each other with a spacer interposed therebetween and sealed in the dye-sensitized solar cell having the structure shown in FIG. In that case, it is applied by introducing the liquefied electrolyte mixture into the cell. The introduction can be performed, for example, by the following procedure:
(I) To introduce the liquefied electrolyte mixture, a hole is formed through the counter electrode substrate 5 and the counter electrode 6.
(Ii) With the opening of the hole facing upward, the hole is placed in a container such as a desiccator capable of heating or having means for heating the cell and capable of reducing the pressure, and the opening of the hole is formed on the counter electrode substrate 5. A predetermined amount of the solid electrolyte mixture is placed so as to cover the.
(Iii) Purge the air in the container with an inert gas such as nitrogen gas.
(Iv) Heat the cell to melt the electrolyte mixture.
(V) Simultaneous with or after melting, evacuation is started to remove air in the cell. Evacuation is continued until no bubbles are generated from the molten electrolyte mixture.
(Vi) The inside of the container is returned to normal pressure, and the melted electrolyte mixture is permeated into the cell.

  In step (3), the applied liquefied mixture is solidified to form a solid electrolyte layer. Note that, also in the step (2), a part of the electrolyte mixture may be solidified, and it goes without saying that the step (2) and the step (3) may be performed as a series of steps. The solidification in the step (3) can be performed by cooling or by volatilizing the solvent when the solvent described later is added. The cooling means is not particularly limited, and may be natural cooling or forced cooling in a temperature-controlled room in which cold air is circulated.

Preferably, before the solidification step, a step of maintaining the temperature below the liquefaction temperature to sufficiently diffuse the electrolyte mixture into the semiconductor layer is included. The temperature is above the temperature at which the electrolyte mixture solidifies or, if a solvent is added, below the boiling point of the solvent. In addition, while maintaining, light, electromagnetic waves such as microwaves, ultrasonic waves, or the like may be irradiated to promote diffusion of the electrolyte mixture. The maintaining time depends on the maintaining temperature, the thickness of the porous semiconductor layer and the like, but may be about 1 minute to 20 minutes. When the porosity of the porous semiconductor layer is about 0.4 to 0.7, when the thickness of the semiconductor layer is 0.1 to 5 μm, heating is maintained for about 1 to 2 minutes, and the thickness is 6 μm to 50 μm. In this case, it is preferable to maintain the heating for 5 minutes or longer. The porosity (ρ) is ρ = W from the density of semiconductor single crystal (d gcm ^-3 ), the apparent volume of the formed film (V cm ³ : Area x film thickness) and the weight (W g). Calculated by (Vd) ^-1 . In order to further increase the diffusion efficiency of the electrolyte mixture and shorten the maintenance time, a low boiling point solvent, for example, an alcohol solvent such as ethanol, a nitrile solvent such as acetonitrile is added to the electrolyte mixture, and a solid electrolyte of You may accelerate impregnation. The addition is different from the conventional method of applying the solution in the semiconductor layer in that it is added to the electrolyte mixture existing in the semiconductor layer, and the addition amount may be very small. When the solvent is added as described above, solidification can be performed by maintaining the temperature at the boiling point of the solvent or lower and then heating the solvent to a temperature at which it volatilizes.

  The steps (1) to (3) are preferably performed in an inert atmosphere such as a glove box, but may be performed inside a desiccator or the like that can be heated and depressurized as described above.

  Parts other than the solid electrolyte layer of the dye-sensitized solar cell may be formed by a known method using a known material. As the transparent substrate 1, glass or plastic can be used. The glass is not particularly limited as long as it can efficiently transmit sunlight and is heat resistant, and soda lime float glass is used, for example. Examples of plastics include tetraacetyl cellulose, polyethylene terephthalate, polyphenylene sulfide, polycarbonate, polyarylate, and polyetherimide.

  As the transparent electrode 2, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), or the like can be used. A commercially available product in which these films are integrated on the transparent substrate 1 with a thickness of about 0.02 to 5 μm can be used.

  A metal lead wire may be provided on the transparent substrate 1, and its material is preferably platinum, copper, aluminum, indium, nickel or the like. The metal lead wire may be formed on a transparent substrate by sputtering, vapor deposition or the like, and the transparent electrode 2 may be provided thereon.

  In the step (1), the porous semiconductor layer 3 supporting the sensitizing dye is formed on the transparent substrate 1. As the semiconductor, for example, titanium oxide, zinc oxide, tin oxide, iron oxide, niobium oxide, zirconium oxide, cerium oxide, tungsten oxide, silicon oxide, aluminum oxide, nickel oxide, barium titanate, strontium titanate, cadmium sulfide, Lead sulfide, zinc sulfide, indium phosphide, copper-indium sulfide or combinations thereof can be used. Among these, titanium oxide, zinc oxide, tin oxide and niobium oxide are preferable, and titanium oxide is particularly preferable from the viewpoint of stability and safety.

  Titanium oxide is roughly classified into two types, that is, anatase-type and rutile-type crystal forms, which are usually a mixture thereof. From the viewpoint of photocatalytic activity, the anatase type is preferred, and the anatase type content is preferably 90% by weight or more. The anatase-type titanium oxide may be a commercially available powder, sol, or slurry, or may have a predetermined particle size by a known method described in various documents.

Regarding the particle size of the semiconductor fine particles, the average particle size (D ₅₀ ) is preferably 1 nm to 1 μm. Further, two or more kinds of particles having different particle sizes may be mixed and used. In this case, it is preferable that the ratio of the average particle size has a difference of 10 times or more. Particles with a large particle size (preferably 100 to 500 nm) have the effect of scattering incident light and increasing the quantum yield. In addition, particles having a small particle size (preferably 5 to 50 nm) have an effect of filling spaces between large particles and increasing the number of sites for supporting the sensitizing dye.

  In order to form the porous semiconductor layer 3, for example, a suspension containing semiconductor particles is applied onto a transparent conductive film, dried, and preferably baked to reduce the electric resistance value. Examples of the solvent for suspending the semiconductor fine particles include ethylene glycol monomethyl ether, isopropyl alcohol, isopropyl alcohol-toluene mixed solvent, water and the like. Further, a commercially available titanium oxide paste may be used instead of the suspension. The application to the substrate can be carried out by various methods such as a dip method, a spray method, a wire bar method, a spin coating method, a roller coating method, a blade coating method, a gravure coating method and a screen printing. The drying temperature and time are appropriately selected according to the boiling point of the suspension solvent used. Further, the firing temperature, time, atmosphere, etc. can be adjusted depending on the types of the substrate and semiconductor particles. In the case of titanium oxide, it is carried out under atmospheric pressure at 400 to 600 ° C. for about 20 minutes to 3 hours. The steps of coating, drying and baking may be repeated twice or more. Further, when a plastic substrate is used as the transparent substrate 1, pressure pressing may be performed at 1 to 100 MPa instead of firing under atmospheric pressure.

The porous semiconductor layer 3 preferably has a large surface area so that it can carry many dyes. However, if it is too large, the diffusion distance of injected electrons increases and the loss due to charge recombination also increases. Therefore, the surface area is preferably 10 to ²⁰⁰ m ² / g, and the thickness is preferably about 0.1 to 100 μm. In the step (2), when the liquefied electrolyte mixture is dropped and applied by a dispenser or the like, the thickness is more preferably 0.1 to 5 μm. When the solid electrolyte mixture is placed on the heated porous semiconductor layer and the electrolyte mixture is melted and simultaneously penetrated into the porous semiconductor layer, the thickness is 5 to 50 μm. More preferably.

  Then, a sensitizing dye is supported on the porous semiconductor layer 3. As the sensitizing dye, known metal complex dyes or organic dyes can be used. Examples of the metal complex include ruthenium complexes, cobalt complexes, various metal porphyrins, metal phthalocyanines and the like. Of these, ruthenium complexes are preferable, and for example, N749 Black Dye, N-3, N-719, Z-907 and the like can be used. As the organic dye, a cyanine dye, a hemicyanine dye, a xanthene dye, a carbazole dye, and a triphenylmethane dye can be used. Among them, a carbazole dye, for example, (2-cyano-3- [5 '' '-(9-Ethyl-9H-carbazole-3-yl) -3', 3,3 '' ', 4-tetra-n-hexyl- [2,2', 5 ', 2' ', 5' ' , 2 '' '']-quarter thiophen-5-yl] acrylic acid: MK-2) is preferred.

  As a method of supporting the sensitizing dye on the porous semiconductor layer 3, a method of immersing the transparent substrate 1 provided with the porous semiconductor layer 3 in a solution in which the sensitizing dye is dissolved is generally used. Examples of the solvent for the dye solution include organic solvents such as alcohol, toluene, acetonitrile, tetrahydrofuran, chloroform and dimethylformamide, and two or more kinds of solvents may be mixed in order to improve the solubility. The dye concentration in the solvent is appropriately adjusted depending on the types of the sensitizing dye and the solvent, but is preferably about 0.01 to 10 mM. If necessary, deoxycholic acid or the like may be added to reduce the association of sensitizing dye molecules. The immersion time is appropriately adjusted depending on the sensitizing dye to be used, the type of solvent, the concentration of the solution, etc., but it is preferably 2 to 50 hours, and the temperature at the time of immersion is preferably 10 to 50 ° C. Immersion may be performed once or multiple times. Also, if the amount of dye supported is large, dye that is not directly bound to the semiconductor will be released into the electrolyte layer of the solar cell and cause a decrease in photoelectric conversion efficiency.Therefore, after dipping in a dye solution, wash with an organic solvent. Then, it is preferable to remove the unsupported dye. Examples of the cleaning agent include relatively highly volatile methanol, ethanol, acetonitrile, acetone and the like. Further, after removing the excess dye by washing, the surface of the semiconductor may be treated with an organic basic compound in order to make the dye-supported state more stable, to accelerate the removal of the unsupported dye. When these compounds are liquid, they may be used as they are, but when they are solid, they may be dissolved in the same solvent as the dye solution and used.

  The counter electrode may have a structure in which the counter electrode substrate 5 and the counter electrode 6 are integrated as shown in FIG. 1 or a structure without the counter electrode substrate as shown in FIG. As the material of the counter electrode 6, in addition to the material of the transparent electrode 2 described above, a semiconductor such as silicon or germanium; a compound semiconductor such as GaAs, InP, ZnSe, CsS or the like; a metal such as gold, platinum, silver or copper, Aluminum, titanium, tantalum, tungsten, etc. can be used. As the counter substrate 5, in addition to the material of the transparent substrate 1 described above, a metal substrate such as aluminum or copper can be used. The counter electrode 6 can be formed on the counter electrode substrate 5 or the solid electrolyte layer 4 by a conventional method such as vapor deposition or coating so as to have a film thickness of about 0.1 to 1.0 μm.

  The sealing layer 7 can be formed by applying a resin adhesive that is cured by heat, light, an electron beam or the like, for example, an epoxy resin adhesive, and then curing the resin adhesive. As the spacer, a polymer film such as a polyester film or a polyethylene film having a constant thickness of 5 to 100 μm can be used.

  In the configuration of FIG. 2, the protective layer 8 can be formed using glass, metal, or a polymer film, and is bonded to the transparent electrode 2 and the counter electrode 6 via an adhesive, for example. Examples of the polymer film include polyvinyl fluoride, polyester, polyolefin, polyphenylene ether, and films used for backsheets of silicon solar cells such as laminated films thereof.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[Examples 1 to 5]
<Preparation of electrolyte mixture>
(1) Iodide salts 1 to 5 shown in the table below (all manufactured by Tokyo Chemical Industry Co., Ltd.) were used.


(2) To each salt, 6 wt% iodine and 4 wt% imidazole were added to the weight of the electrolyte mixture to prepare an electrolyte mixture.

<Creation of dye-sensitized solar cell>
(1) A dye-sensitized solar cell was prepared by the procedure shown in FIG. First, a part of the SnO ₂ film of the fluorine-doped glass substrate with SnO ₂ film (manufactured by Nippon Sheet Glass Co., Ltd.) was etched with zinc powder and hydrochloric acid, washed with distilled water and ethanol, and then dried. Titanium oxide paste (Ti nanoxide T / SP manufactured by Solaronix Co., Ltd.) was screen-printed on the etched portion so as to have an area of about 5 mm × 5 mm, pre-dried at 100 ° C. for 30 minutes, and then 500 in an air atmosphere. Sintering was performed at 0 ° C. for 1 hour to form a titanium oxide layer having a film thickness of 4.5 μm. Next, the glass substrate provided with the titanium oxide layer was immersed in an acetone solution of the sensitizing dye (MK-2) for 24 to 48 hours to support the sensitizing dye on the titanium oxide layer, and then washed with acetone.
(2) The glass substrate was placed on a hot plate in a glove box with the titanium oxide layer facing upward. A reagent bottle containing 0.3 g of the electrolyte mixture was also placed on the same hot plate, and the temperature of the hot plate was raised to 100 ° C. After confirming that the electrolyte mixture was melted, 20 to 60 μL was sucked with a micropipette and dropped onto the titanium oxide layer, and it was confirmed that the electrolyte mixture spreads in and on the titanium oxide layer. In Examples 4 and 5, 0.3 g of the electrolyte mixture was placed on the titanium oxide layer and applied, and FIG. 3 shows this mode. The obtained glass substrates were kept at 100 ° C. for 1 minute in Examples 1, 2 and 3 and 2 minutes in Examples 4 and 5, respectively, and then the electrolyte mixture adhering to the conductive glass was removed with a cotton swab and oxidized. The excess electrolyte mixture on the titanium layer was removed and flattened. The substrate was removed from the hot plate and naturally cooled. Then, platinum was sputtered on the obtained solid electrolyte layer to form a counter electrode. In order to prevent contamination of the electrolyte and the like, the counter electrode was covered with a cover glass of 10 mm × 10 mm, and the periphery was sealed with a heat fusion sheet to prepare dye-sensitized solar cells 1 to 5. The time required for all steps was 10 to 20 minutes.

[Example 6]
The thickness of the titanium oxide layer was set to 10 μm, and 10 mg of the electrolyte mixture of Example 1 was placed on the titanium oxide layer and melted instead of dropping with a micropipette. Dye-sensitized solar cell 6 was prepared in the same manner as in Example 4.

[Comparative example]
According to the method described in Non-Patent Document 1, a solution obtained by dissolving the same electrolyte mixture as that in Example 1 in methanol was dropped and dried repeatedly to prepare a dye-enhanced solar cell (comparative).

<Measurement of photoelectric conversion characteristics>
The obtained dye-sensitized solar cell was attached with a black mask (having a square hole of 4.8 mm square) so as not to be affected by scattered light from the surroundings, and the intensity of 100 mWcm ⁻² . (1SUN, AM1.5, solar simulator) was irradiated, and the current-voltage characteristics were measured according to a standard method. The results are shown in Table 2.

  As shown in the above table, according to the method of the present invention, a photoelectric conversion efficiency (η) of 2% or more with respect to sunlight is achieved in a very short time except for Example 4 (EPY) and Example 5 (BDI). We were able to. In Example 6, since the photoelectric conversion efficiency was remarkably improved by allowing the film to stand on the thicker titanium oxide layer for a longer period of time, it is expected that the same improvement can be seen in the other Examples. It

  According to the production method of the present invention, a dye-sensitized solar cell provided with a solid electrolyte layer suitable for practical use can be produced quickly and easily.

1 Transparent Substrate 2 Transparent Electrode 3 Porous Semiconductor Layer 4 Solid Electrolyte Layer 5 Counter Electrode Substrate 6 Counter Electrode 7 Sealing Layer 8 Protective Layer

Claims (2)

A method for producing a dye-sensitized solar cell comprising a porous semiconductor layer carrying a sensitizing dye and a solid electrolyte layer at least between a pair of electrodes,
(1) a step of forming a porous semiconductor layer carrying a sensitizing dye,
(2) the porous semiconductor layer, you solidification step to applied by liquefaction a mixture comprising at least an electrolyte redox pair at a temperature of 70 ° C. to 210 ° C., and (3) The applied mixture as engineering, including the following,
(3-1) A step of maintaining the porous semiconductor layer to which the mixture has been applied for a predetermined time at a temperature equal to or lower than the temperature at which the liquefaction of step (2) was performed,
(3-2) a step of solidifying the mixture,
Including the method.
Electrolyte has a melting point of 70 ° C. to 210 ° C. at atmospheric pressure, pyridinium salts, is at least one selected from the group consisting of piperidinium salts and imidazolium salts, according to claim 1 Symbol placement methods.