JP2012003955A - Method of manufacturing dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a dye-sensitized solar cell, capable of improving productivity by shortening the time of a dye carrying step.SOLUTION: The method of manufacturing the dye-sensitized solar cell related to an embodiment of the invention includes: a step of forming a semiconductor layer on a base material; a step in which a dye solution obtained by dissolving photosensitization dye of 5 mM or more into a first solvent of which the contact angle with the surface of the semiconductor layer is 6° or less, and the boiling point is 80°C or more is coated on the surface of the semiconductor layer; and a step of having the semiconductor layer carry the dye.

Description

  The present invention relates to a method for producing a dye-sensitized solar cell including a semiconductor layer carrying a photosensitizing dye.

  In recent years, development of a dye-sensitized solar cell which is one of photoelectric conversion elements has been promoted. The dye-sensitized solar cell includes a semiconductor layer carrying a photosensitizing dye, a negative electrode in contact with the semiconductor layer, an electrolyte, and a positive electrode facing the semiconductor layer with the electrolyte interposed therebetween. The photosensitizing dye emits electrons by light incident on the semiconductor layer, and the emitted electrons are transported to the negative electrode through the semiconductor layer. The negative electrode and the positive electrode are connected to an external circuit, and electrons that have reached the positive electrode through the external circuit are returned to the dye by the electrolyte. By repeating such a cycle, electric energy is extracted in the external circuit.

  The photoelectric conversion efficiency of the dye-sensitized solar cell is higher as the amount of the dye carried on the semiconductor layer is larger. As a method for supporting a dye on the semiconductor layer, a so-called dipping method in which a substrate on which a semiconductor layer is formed is immersed in a dye solution is widely known. However, in the immersion method, in order to realize practical photoelectric conversion efficiency, it is necessary to immerse the semiconductor layer in the dye solution for a long time (for example, 12 hours or more). In addition, when multiple types of solutes are contained in the dye solution, when the dye solution is used repeatedly, it is necessary to replenish these solutes so as to compensate for the decrease in the amount of solute supported on the semiconductor layer. there were. In this case, because each solute decreases at a different rate based on the difference in adsorption force to the semiconductor layer surface, or because there is no method for easily measuring the concentration of the colorless and transparent coadsorbent, It was difficult to control the concentration of each solute in the solution.

  In view of this, a dye-carrying method that replaces the dipping method has been proposed. For example, Patent Document 1 below describes a method of adsorbing a dye to a semiconductor layer in a vacuum. According to this method, since deaeration of the semiconductor layer is promoted, a sufficient amount of dye can be adsorbed. Patent Document 2 below describes a method of supporting a dye solution on a semiconductor layer using an inkjet method.

JP 2002-246076 A Japanese Patent No. 4029553

  In recent years, improvement in productivity of dye-sensitized solar cells has been desired. However, the method described in Patent Document 1 requires an extra time for exhausting into the vacuum chamber and venting to the atmosphere, and thus a great improvement in productivity cannot be expected. Further, in the method described in Patent Document 2, since the discharge amount per one time from the ink jet nozzle is small, it is necessary to repeat the dye holding step a plurality of times in order to adsorb a sufficient amount of the dye.

  In view of the circumstances as described above, an object of the present invention is to provide a method for producing a dye-sensitized solar cell capable of shortening the time of the dye carrying step and improving the productivity.

In order to achieve the above object, a method for producing a dye-sensitized solar cell according to an embodiment of the present invention includes a step of forming a semiconductor layer on a substrate.
A dye solution obtained by dissolving 5 mM or more of a photosensitizing dye in a first solvent having a contact angle with the surface of the semiconductor layer of 6 ° or less and a boiling point of 80 ° C. or more is applied to the surface of the semiconductor layer. Is done.
The dye is supported on the semiconductor layer.

  In the above production method, a dye solution is prepared by dissolving a photosensitizing dye in a first solvent. This dye solution is applied to the porous semiconductor layer, and penetrates into the semiconductor layer using capillary action as a driving force. The dye contained in the permeated dye solution is carried by covalent bonding or coordinate bonding with the material constituting the semiconductor layer.

  By using a solvent having a contact angle with the surface of the semiconductor layer of 6 ° or less as the first solvent, the dye solution can be rapidly permeated into the porous semiconductor layer. Moreover, the pigment | dye solution contains the pigment | dye of 5 mM or more, and the carrying | support efficiency of the pigment | dye to a semiconductor layer can be improved. Furthermore, by using a solvent having a boiling point of 80 ° C. or higher as the first solvent, the dye solution can reach the deepest portion of the semiconductor layer without evaporating the dye solution. As a result, the amount of dye supported by the semiconductor layer is increased, and a dye-sensitized solar cell with high photoelectric conversion efficiency can be obtained.

The step of supporting the dye on the semiconductor layer may include a step of allowing the dye solution to penetrate into the semiconductor layer and a step of drying the first solvent.
Thus, the dye solution can reach the deepest part of the semiconductor layer, and the dye can be fixed to the semiconductor layer.

The method for producing the dye-sensitized solar cell may further include a step of washing the semiconductor layer supporting the dye with a second solvent that is a good solvent for the dye.
Thereby, the unsupported dye remaining on the surface of the semiconductor layer can be removed, and the unsupported dye remaining in the semiconductor layer can be further permeated into the semiconductor layer. The second solvent may be the same solvent as the first solvent, or may be a solvent having higher affinity with the semiconductor layer than the first solvent.

  According to the present invention, since the efficiency of dye support on the semiconductor layer can be increased, the time of the dye support process can be shortened to improve productivity.

It is a schematic sectional drawing which shows the structure of the dye-sensitized solar cell which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the electrode substrate which comprises the said dye-sensitized solar cell. It is a process flow explaining the manufacturing method of the dye-sensitized solar cell which concerns on one Embodiment of this invention. It is a figure explaining the application | coating process of the pigment | dye solution in FIG. It is a figure explaining the carrying | support process of the pigment | dye in FIG. It is a figure explaining the washing | cleaning process of the electrode substrate in FIG. It is a schematic sectional drawing which shows the modification of a structure of the said electrode substrate. It is a schematic sectional drawing which shows the modification of a structure of the said electrode substrate. It is a schematic sectional drawing which shows the modification of a structure of the said electrode substrate. It is a schematic sectional drawing which shows the modification of a structure of the said electrode substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Configuration of dye-sensitized solar cell]
FIG. 1 is a cross-sectional view showing a schematic configuration of a dye-sensitized solar cell according to an embodiment of the present invention. The dye-sensitized solar cell 1 includes a first base material 11, a transparent electrode layer 12, a semiconductor layer 13, an electrolyte layer 14, a counter electrode layer 15, and a second base material 16. The dye-sensitized solar cell 1 according to the present embodiment has an electrode structure in which charges are generated in the semiconductor layer 13 by light irradiated from the first base material 11 side. An external circuit (not shown) is connected between the transparent electrode layer 12 and the counter electrode layer 15.

  The first base material 11 has a function of supporting the semiconductor layer 13 and the transparent electrode layer 12. The 1st base material 11 has translucency, for example, is formed with the material which has the transmittance | permeability of 50% or more with respect to the light of a wavelength of 300-1500 nm. Specific examples of the material include glass or resin films such as PET (polyethylene terephthalate), PMMA (polymethyl methacrylate), TAC (triacetyl cellulose), PC (polycarbonate), and cycloolefin polymer.

The transparent electrode layer 12 has translucency, and supplies charges generated in the semiconductor layer 13 to the external circuit. Typically, the transparent electrode layer 12 is made of TCO (transparent tin oxide) such as ITO (indium tin oxide), ATO (antimony-doped tin oxide), IZO (indium zinc oxide), ZnO, FTO (fluorine-doped tin oxide), SnO ₂ or the like. Conducting oxide). The sheet resistance of the transparent electrode layer 12 is 1 kΩ or less.

  The semiconductor layer 13 is formed of a semiconductor material that carries a photosensitizing dye. The semiconductor layer 13 has a function of absorbing light and generating charges, and a function of transporting charges injected from the dye to the transparent electrode layer 12. The semiconductor layer 13 is formed of a porous material in order to increase the amount of dye supported. Specific semiconductor materials for forming the semiconductor layer 13 include various metal oxide semiconductors such as titanium oxide, zirconium oxide, zinc oxide, vanadium oxide, niobium oxide, tantalum oxide, and tungsten oxide, strontium titanate, and calcium titanate. , Various composite metal oxide semiconductors such as magnesium titanate, barium titanate, potassium niobate, transition metal oxides such as magnesium oxide, strontium oxide, aluminum oxide, cobalt oxide, nickel oxide, manganese oxide, cerium oxide, gadolinium oxide Lanthanoid oxides such as samarium oxide and ytterbium oxide, natural or synthetic silicate compounds represented by silica, and the like. These materials may be used alone or in combination.

  The photosensitizing dye (hereinafter also simply referred to as “dye”) held in the semiconductor layer 13 is not particularly limited as long as it exhibits a sensitizing action. Examples of photosensitizing dyes include xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine, cyanine dyes such as merocyanine, quinocyanine and cryptocyanine, and basic dyes such as phenosafranine, cabrio blue, thiocin and methylene blue. Other azo dyes, porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, phthalocyanine compounds, coumarin compounds, ruthenium Ru bipyridine complexes, terpyridine complexes, anthraquinone dyes, polycyclic quinone dyes, squarylium dyes, etc. Is mentioned. Among them, a ruthenium Ru bipyridine complex whose ligand has a pyridine ring has a high quantum yield and is preferable as a photosensitizing dye. However, the photosensitizing dye is not limited to this, and can be used alone or in combination of two or more.

The electrolyte layer 14 is provided between the semiconductor layer 13 and the counter electrode layer 15. As the electrolyte layer 14, an electrolytic solution, or a gel or solid electrolyte can be used. Examples of the electrolyte include a solution containing a redox system (redox _couple ). Specifically, a combination of iodine I ₂ and a metal iodide salt or an organic iodide salt, bromine Br ₂ and a metal bromide salt or an organic salt. A combination with a bromide salt is used. The cations constituting the metal halide salt are lithium Li ⁺ , sodium Na ⁺ , potassium K ⁺ , cesium Cs ⁺ , magnesium Mg ²⁺ , calcium Ca ²⁺ , and the cation constituting the organic halide salt is Quaternary ammonium ions such as tetraalkylammonium ions, pyridinium ions, and imidazolium ions are suitable, but are not limited to these, and can be used alone or in admixture of two or more.

Among these, an electrolyte combining iodine I ₂ and a quaternary ammonium compound such as lithium iodide LiI, sodium iodide NaI, or imidazolium iodide is particularly preferable. The concentration of the electrolyte salt in the electrolytic solution is preferably 0.05M to 5M, more preferably 0.1M to 3M. The concentration of iodine I ₂ or bromine Br ₂ is preferably 0.0005M to 1M, and more preferably 0.005 to 0.5M. Various additives such as 4-tert-butylpyridine and carboxylic acid can be added for the purpose of improving the open circuit voltage and the short circuit current.

In the present embodiment, the electrolyte layer 14 is composed of an electrolytic solution containing a redox species. Examples of the redox species include I ⁻ / I ₃ ⁻ . Here, the triiodide ion I ₃ ⁻ is a chemical species in which I ₂ is associated with the iodide ion I ⁻ and exists as an ion.

  The counter electrode layer 15 is laminated on the second base material 16 and is formed of, for example, a platinum layer or a carbon layer. The second substrate 16 is for supporting the counter electrode layer 15 and is formed of the same material as that of the first substrate 11, for example. Note that the second base material 16 may be formed of a non-translucent material.

[Operation of dye-sensitized solar cell]
The dye-sensitized solar cell 1 configured as described above operates as a battery having the counter electrode layer 15 as a positive electrode and the transparent electrode layer 12 as a negative electrode when light enters from the first substrate 11 side.

  That is, when the photosensitizing dye absorbs photons that have passed through the first base material 11 and the transparent electrode layer 12, electrons in the dye are excited from the ground state to the excited state. Excited electrons are extracted to the conduction band of the semiconductor layer 13 through electrical coupling between the dye and the semiconductor layer 13, and reach the transparent electrode layer 12 through the semiconductor layer 13.

On the other hand, the dye that has lost electrons receives electrons from the reducing agent in the electrolyte layer 14, for example, I ^−, by the following reaction, and generates an oxidizing agent, for example, I ₃ ⁻ in the electrolyte layer 14.
2I ⁻ → I ₂ + 2e ⁻
I ₂ + I ⁻ → I ₃ ⁻
The generated oxidizing agent reaches the counter electrode layer 15 by diffusion, receives electrons from the counter electrode layer 15 by the following reaction opposite to the above reaction, and is reduced to the original reducing agent.
I ₃ ⁻ → I ₂ + I ⁻
I ₂ + 2e ⁻ → 2I ⁻

  The electrons supplied from the transparent electrode layer 12 to the external circuit are converted into electrical work by the external circuit and then returned to the counter electrode layer 15. By repeating the above operation, light energy is converted into electric energy.

[Method for producing dye-sensitized solar cell]
Next, a method for producing a dye-sensitized solar cell, particularly a method for supporting a dye on a semiconductor material forming the semiconductor layer 13 will be described.

  First, as shown in FIG. 2, an electrode substrate 10 in which a transparent electrode layer 12 and a semiconductor material layer 13a are sequentially laminated on a first base material 11 is prepared. In forming the semiconductor material layer 13a, a coating liquid in which semiconductor fine particles such as titanium oxide fine particles are dispersed in a solvent is prepared, and the transparent electrode layer 12 is coated with a coating film having a predetermined thickness by a coating method or a printing method. Form on top. Then, after evaporating the solvent component from the coating liquid layer, baking is performed.

  The semiconductor material layer 13 a is laminated on the transparent electrode layer 12. The transparent electrode layer 12 may be formed in the entire region of the substrate 11 or may be formed in a partial region of the substrate 11. For example, the transparent electrode layer 12 may be formed on the surface of the substrate 11 in a predetermined shape such as a stripe shape. In this case, the semiconductor material layer 13 a is formed in a predetermined shape such as a stripe shape in accordance with the shape of the transparent electrode layer 12.

  Next, a photosensitizing dye is adsorbed on the semiconductor material layer 13a. FIG. 3 is a flow showing the processing procedure of the dye adsorption step. The dye adsorption process to the semiconductor material layer 13a includes a dye solution coating process (step 101), a dye supporting process (step 102), a cleaning process (step 103), and a drying process (step 104).

(Dye solution application process)
The dye solution is prepared by dissolving a photosensitizing dye in a solvent. It is desirable that the dye solution and the semiconductor material layer 13a have high affinity in order to penetrate the dye solution deep into the semiconductor material layer 13a and realize quick and uniform dye coating. In the present embodiment, a solvent having a contact angle with the surface of the semiconductor material layer 13a of 6 ° or less, more preferably 5 ° or less is used as a solvent for the dye.

  In order to improve the carrying speed by increasing the amount of the dye to penetrate, the dye concentration of the dye solution is 5 mM or more due to the limitation of the coating thickness in the coating process. The upper limit of the dye concentration is not particularly limited, but if the concentration is excessively high, the amount of the dye contained in the solution greatly exceeds the amount of the dye that can be carried on the semiconductor material layer 13a, and a large amount of residual dye is generated. There is a possibility. In order to prevent wasteful use of the dye, the concentration of the dye solution is, for example, 100 mM or less.

  The dye solution penetrates into the semiconductor material layer 13a by capillary action. At the same time, the dye solution evaporates from the surface of the semiconductor material layer 13a. When the volatility of the solvent is high, the solvent volatilizes before the dye solution sufficiently penetrates into the semiconductor material layer 13a, and the dye does not reach the back of the semiconductor material layer 13a. Therefore, in the present embodiment, a solvent having a boiling point of 80 ° C. or higher is used in order to prevent the solvent from evaporating before the dye solution reaches the deepest portion of the semiconductor material layer 13a. Further, since the penetration of the dye solution into the semiconductor material layer 13a is faster as the viscosity of the dye solution is lower, a solvent is used such that the viscosity after preparation of the dye solution is 100 mPa · s or less at room temperature.

  Specific examples of such a solvent include 3-methoxypropionitrile (MPN), 3,3-dimethoxypropionitrile ethoxypropionitrile, 3-ethoxypropionitrile, 3,3′-oxydipropionitrile, 3-aminopropionitrile, propionitrile, propyl cyanoacetate, 3-methoxypropyl isothiocyanate, 3-phenoxypropionitrile, p-anisidine 3- (phenylmethoxy) propanenitrile, n-propanol, 2-propanol, n -Butanol, 2-butanol, isobutanol, t-butanol, ethylene glycol, triethylene glycol, 1-methoxy-ethanol, 1,1-dimethyl-2-methoxyethanol, 3-methoxy-1-propanol, dimethylformamide (DMF) ), Benzene, toluene, o-xylene, m-xylene, p-xylene, chlorobenze , Dichlorobenzene, butyl acetate, ethyl acetate, cyclohexanone, cyclopentanone, dimethylacetamide, dimethyl carbonate, butyl cellosolve, diacetone alcohol and the like. These solvents may be used alone, or a plurality of these solvents may be combined to obtain a desired contact angle, boiling point, solubility, and viscosity. In this embodiment, an amide solvent is used, and more specifically, dimethylformamide (DMF) is used.

As the dye, Ru complex N3, N621, N712, N719, N749, N773, N790, N820, N823, N845, N886, N945, K9, K19, K23, K27, K29, K51, K60, K66, K69, K73, K77, Z235, Z316, Z907, Z907Na, Z910, Z991, CYC-B1, HRS-1, As an organic dye system, Anthocyanine, WMC234, WMC236, WMC239, WMC273, PPDCA, PTCA, BBAPDC, NKX-2311, NKX-2510, NKX-2553 (manufactured by Hayashibara Biochemical), NKX-2554 (manufactured by Hayashibara Biochemical), NKX-2569, NKX-2586, NKX-2587 (manufactured by Hayashibara Biochemical), NKX-2677 (manufactured by Hayashibara Biochemical), NKX- 2697, NKX-2753, NKX-2883, NK-5958 (manufactured by Hayashibara Biochemical), NK-2684 (manufactured by Hayashibara Biochemical), Eosin Y, Mercurochrome, MK-2 (manufactured by Soken Chemical), D77, D102 (Mitsubishi Paper) Chemical), D120, D131 (Mitsubishi Paper Chemical), D149 (Mitsubishi Paper Chemical), D150, D190, D205 (Mitsubishi Paper Chemical), D358 (Mitsubishi Paper Chemical), JK-1, JK-2, 5, ZnTPP, H ₂ TC ₁ PP, H ₂ TC ₄ PP, Phthhalocyanine Dye (Zinc phtalocyanine-2,9,16,23-tetra-carboxylic acid, 2- [2 '-(zinc9', 16 ', 23' -tri-t ert-butyl-29H, 31H-phthalocyanyl)] succinic acid, Polythiohene Dye (TT-1), Pendant type polymer, Cyanine Dye (P3TTA, C1-D, SQ-3, B1) and the like.

  The dye supporting step is performed by applying a dye solution onto the semiconductor material layer 13a. The coating method is not particularly limited, and a known coating method can be used. Known coating methods include, for example, micro gravure coating method, wire bar coating method, direct gravure coating method, die coating method, spray coating method, reverse roll coating method, curtain coating method, comma coating method, knife coating method, spin coating. Law.

  FIG. 4 schematically shows a state in which the dye solution is die-coated in a stripe shape on the semiconductor material layer 13a formed in a stripe shape on the base material 11. FIG. An arrow A in the figure indicates the transport direction of the electrode substrate 10, and the electrode substrate 10 is transported along the extending direction of the semiconductor material layer 13a. The electrode substrate 10 may be formed in a band shape (web shape) so that it can be conveyed by a roll-to-roll method. In this case, the electrode substrate 10 is cut into a predetermined size in a subsequent process. The die head 100 has a plurality of slits 100a for discharging the dye solution at the tip. Each slit 100a faces the semiconductor material layer 13a in each column and has a length corresponding to the width of the semiconductor material layer 13a in each column. As described above, the coating film 13b of the dye solution having a predetermined thickness is formed in each row of the semiconductor material layer 13a of each row of the electrode substrate 10.

  The thickness of the coating film 13b is also adjusted by the viscosity of the dye solution. When the viscosity of the dye solution is 100 mPa · s or less at room temperature, the thickness of the coating film 13b is preferably 150 μm or less because the dye solution may flow out to the outside of the coating region. Note that organic solvents such as DMF have low affinity for plastics such as PET. For this reason, when DMF is used as the solvent of the dye solution, the dye solution is less likely to adhere to the PET substrate 11, and the coating film 13b can be formed on the semiconductor material layer 13a with high accuracy.

(Dye loading process)
The dye solution applied to the semiconductor material layer 13a penetrates into the porous semiconductor material layer 13a using a capillary phenomenon as a driving force, and the dye contained in the dye solution is supported by covalent bonding or coordinate bonding on the surface of the semiconductor material. Is done.

  According to this embodiment, since the solvent having a contact angle with the surface of the semiconductor material layer 13a of 6 ° or less is used as the solvent of the dye solution, the dye solution quickly penetrates into the porous semiconductor material layer 13a. Can be made. Moreover, the pigment | dye solution contains the pigment | dye of 5 mM or more, and the carrying | support efficiency of the pigment | dye to the semiconductor material layer 13a can be improved. Furthermore, since the solvent having a boiling point of 80 ° C. or higher is used as the solvent, the dye solution can reach the deepest portion of the semiconductor material layer 13a without evaporating the dye solution.

  Next, the electrode substrate 10 is dried. As a result, the loading of the pigment by the semiconductor material layer 13a is promoted, and the excess solvent on the semiconductor material layer 13a is removed. The drying process may be performed after the dye solution has sufficiently penetrated into the semiconductor material layer 13a, or may be performed before it has sufficiently penetrated.

  The drying process is performed under an atmospheric pressure or a reduced pressure atmosphere. The drying temperature may be room temperature or a heated atmosphere. In addition, the drying process may be performed in a cooling atmosphere as long as the viscosity of the solvent is not increased more than necessary. By performing the drying process in a cooling atmosphere, the dye solution can be sufficiently permeated into the semiconductor material layer 13a while suppressing evaporation of the solvent. Further, for the purpose of obtaining the above action, the atmospheric temperature of the drying process may be variably controlled.

  FIG. 5 is a schematic perspective view of the drying furnace 101 for explaining the drying process of the electrode substrate 10. The drying furnace 101 transports the electrode substrate 10 in the direction of arrow A by the transport roller 102. The drying furnace 101 has a plurality of heaters 103 arranged along the transport direction of the electrode substrate 10. The electrode substrate 10 is conveyed through the drying furnace 101 while being subjected to the heat treatment by the heater 103, whereby the solvent component of the dye solution is removed from the semiconductor material layer 13a.

  In the drying treatment, the solvent of the dye solution may be in a completely dried state from the semiconductor material layer 13a or may be in an incompletely dried state slightly remaining in the semiconductor material layer 13a.

(Washing process)
Subsequently, a cleaning process of the electrode substrate 10 is performed. The purpose of this step is to wash the electrode substrate 10 with a good solvent for the dye and to remove the unsupported dye from the semiconductor material layer 13a. FIG. 6 is a schematic perspective view of the cleaning apparatus 104 for explaining the cleaning process of the electrode substrate 10.

  The cleaning device 104 includes a container 106 that stores a cleaning solvent 105 and a plurality of guide rollers 107 that guide the electrode substrate 10 into the container 106. In the cleaning process of the electrode substrate 10, the excess dye remaining in the semiconductor material layer 13 a is removed by immersing the electrode substrate 10 in the solvent 105 in the container 106. In order to enhance the cleaning effect, ultrasonic vibration may be applied to the solvent 105. In this case, the ultrasonic generator 108 is installed at the bottom of the container 106 as shown in the figure, but the installation location is not limited to this. Further, the cleaning process may be performed while the electrode substrate 10 is continuously transported, or the cleaning process may be performed while the electrode substrate 10 is transported intermittently.

  If the solvent evaporates in the depth (thickness) direction of the semiconductor material layer 13a in the above-described dye supporting step, a region where the dye is not supported is formed in a deeper region. In this embodiment, since the semiconductor material layer 13a is cleaned with a good solvent for the dye, the unsupported dye remaining on the surface of the semiconductor material layer 13a is removed while remaining in the semiconductor material layer 13a. The unsupported dye can be re-penetrated into a deeper region of the semiconductor material layer 13a. Further, by applying ultrasonic waves to the solvent, the penetration effect of the solvent is increased, and thereby the dye can reach the deepest portion of the semiconductor material layer 13a.

  The solvent used for washing is not particularly limited as long as it is a good solvent for the dye. For example, the above-mentioned various solvents (for example, DMF) used for preparing the dye solution are used. A solvent having higher affinity for the semiconductor material layer 13a than the solvent used for the dye solution may be used as the cleaning solvent. Thereby, the re-penetration effect of the pigment | dye in a washing | cleaning process can be heightened.

(Drying process)
After completion of the cleaning process, the electrode substrate 10 is dried. By this drying treatment, the solvent used for washing is removed, and the step of supporting the dye on the semiconductor material layer 13a is completed. Thereby, the semiconductor layer 13 carrying the photosensitizing dye is produced. The drying process described with reference to FIG. 5 can be used for this drying process. In addition to this, a hot air drying method or a natural drying method may be employed.

  According to this embodiment, the dye solution can be penetrated to the back of the semiconductor material layer 13a, and the dye application can be performed quickly and without unevenness. Thereby, the dye-sensitized solar cell with the high photoelectric conversion efficiency provided with the semiconductor layer 13 with a high dye carrying amount can be manufactured.

  Further, according to the present embodiment, since the dye solution having very high affinity with the semiconductor material layer 13a and excellent in permeability to the semiconductor material layer 13a is used, the processing time required for the dye supporting process is reduced. It can be shortened and productivity can be improved.

[Experimental example]
Hereinafter, experimental examples performed by the present inventors will be described.

(Experimental example 1)
A titanium oxide coating solution for forming a semiconductor material layer was prepared. Two types of titanium oxide fine particles were used for preparing the coating liquid. As the first titanium oxide fine particles, P25 (trade name; manufactured by Degussa, a mixture of anatase type crystals (80%) and rutile type crystals (20%), average particle size of primary particles of about 20 nm) was used. TA-300 (trade name; manufactured by Fuji Titanium Industry Co., Ltd., anatase crystal, average particle diameter of primary particles of about 200 nm) was used as the second titanium oxide fine particles. These titanium oxide fine particles, butoxy titanium dimer (DBT; manufactured by Mitsubishi Gas Chemical Co., Inc.), and tetramethoxysilane (TMOS; manufactured by Junsei Chemical Co., Ltd.) are mixed and dispersed in a solvent, thereby obtaining titanium oxide. A coating solution was prepared. The blending amounts in the coating solution were 2.5% by mass for DBT and 0.1% by mass for TMOS. Ethanol was used as the solvent.

  The titanium oxide coating solution prepared as described above was applied on a PET film (trade name: 0300E; manufactured by Mitsubishi Plastics Co., Ltd.) with a thickness of 125 μm with a No. 30 bar coater, allowed to dry naturally, and then at 150 ° C. for 30 The titanium oxide semiconductor layer was formed by baking for a minute. A part of the produced titanium oxide semiconductor layer was scraped off by the edge of the glass plate, and the level difference from the surface of the semiconductor fine particle layer to the surface of the base material was measured. The measurement result was 5 μm. For measuring the level difference, a stylus type surface roughness measuring device “Surf Corder ET4000” (trade name) manufactured by Kosaka Laboratory Ltd. was used.

  A dye solution was prepared by dissolving Z907 dye in a ratio of 3, 5, 8, 15, 50 mM and dodecylphosphonic acid in a ratio of 0.045 mM in DMF (dimethylformamide) as a solvent. The contact angle between the titanium oxide semiconductor layer and the solvent was measured with a solid surface energy analyzer “FACE CA-EX” (trade name). As a result of the measurement, the contact angle was 5 ° or less.

  Each prepared dye solution was apply | coated to the titanium oxide semiconductor layer using the 3, 7, 14, 30, 44, 75th bar coater. The coating thickness was a value obtained by multiplying the numerical value of the count by 2.29. After coating, the dye solution was naturally dried under air. Thereafter, the titanium oxide semiconductor layer was dipped in acetonitrile together with the base material, and was washed for 5 minutes under ultrasonic waves to remove excess dye. Then, it was dried and the penetration degree of the dye in the titanium oxide semiconductor layer was evaluated.

In evaluating the penetration of the dye, the titanium oxide semiconductor layer was observed from the back surface of the substrate to evaluate whether the dye penetrated evenly. Moreover, the penetration degree of the pigment | dye in a layer was evaluated by cut | disconnecting a titanium oxide semiconductor layer with a microtome, and observing the cut surface. As an evaluation method, the above evaluation was performed for each dye solution, and the determination was made based on the following three criteria.
○: The dye penetrates deep into the semiconductor layer without unevenness. Δ: The dye penetrates unevenly, and there is an area that penetrates deep into the semiconductor layer, but some areas do not penetrate. ×: The dye penetrates deeply. Not penetrated

(Experimental example 2)
A titanium oxide semiconductor layer was prepared under the same conditions as in Experimental Example 1 except that the solvent of the dye solution was ethanol, and the degree of dye penetration was evaluated. The contact angle between ethanol and the titanium oxide semiconductor layer was 5 ° or less.

(Experimental example 3)
A titanium oxide semiconductor layer was prepared under the same conditions as in Experimental Example 1 except that MPN (3-methoxypropionitrile) was used as the solvent of the dye solution, and the degree of penetration of the dye was evaluated. The contact angle between MPN and the titanium oxide semiconductor layer was 5.9 °.

  The evaluation results of Experimental Examples 1 to 3 are summarized in Table 1.

  As shown in Table 1, the higher the dye concentration, the smaller the coating thickness of the dye solution that can penetrate the dye to the back of the semiconductor layer without unevenness. That is, the lower the dye concentration, the smaller the amount of dye carried on the semiconductor layer. Therefore, in order to increase the amount of dye carried, it is necessary to increase the coating thickness of the dye solution. However, due to the relationship with the viscosity of the dye solution, there is a limit to the thickness that can be accurately applied to the coating region. Therefore, for example, the dye concentration at which the dye can be efficiently supported on the semiconductor layer with a coating thickness of 150 μm or less is 5 mM or more in Experimental Example 1, 50 mM or more in Experimental Example 2, and 15 mM or more in Experimental Example 3.

  The reason why the penetration degree of the dye into the semiconductor layer is greatly different between Experimental Example 1 and Experimental Example 2 is based on the difference in the solvent boiling point of the dye solution. That is, it is considered that the lower the boiling point of the solvent, the faster the solvent evaporates after coating the dye solution, so that the dye cannot reach the back of the semiconductor layer. In this case, by increasing the dye concentration, the dye can reach the back of the semiconductor layer, but the dye remains undissolved and the cost increases.

  On the other hand, the difference in the degree of penetration of the dye into the semiconductor layer between Experimental Example 1 and Experimental Example 3 is based on the difference in the contact angle between the solvent of the dye solution and the titanium oxide semiconductor layer. That is, the solvent (DMF) used in Experimental Example 1 has a smaller contact angle with the semiconductor layer and higher affinity than the solvent (MPN) used in Experimental Example 3. Thus, the quality of the dye solution penetrating into the semiconductor layer is considered to cause a difference in the degree of dye penetration.

(Experimental example 4)
On a FTO glass substrate (manufactured by Nippon Sheet Glass Co., Ltd., surface resistance 13Ω / □), a titanium oxide semiconductor layer produced under the same conditions as in Experimental Example 1 was formed with a film thickness of 5 μm. A dye solution was prepared by dissolving 15 mM of Z907 dye and 0.045 mM of dodecylphosphonic acid in DMF. The dye solution was applied to the titanium oxide semiconductor layer using a number 7 bar coater and allowed to dry naturally. The treatment time of the dye on the semiconductor layer was 5 minutes. After coating, the semiconductor layer was immersed in acetonitrile and rinsed under ultrasonic waves for 5 minutes. Thereafter, it was naturally dried and the degree of pigment was evaluated. As a result, the evaluation standard of Experimental Example 1 was “◯”.

  The dried titanium oxide semiconductor layer was shaped into a 1 cm square, and the titanium oxide semiconductor layer was surrounded by a 50 μm silicon spacer. Thereafter, an electrolytic solution was dropped on the semiconductor layer, and the electrolytic solution was sandwiched between glasses on which a platinum film as a counter electrode was formed by sputtering to produce a dye-sensitized solar cell. The photoelectric conversion efficiency of the produced cell was evaluated.

(Experimental example 5)
Except for the dye supporting treatment, dye-sensitized solar cells were prepared under the same conditions as in Experimental Example 4, and the photoelectric conversion efficiency was evaluated. In this experimental example, a dye solution was prepared by dissolving Z907 dye in ethanol at a ratio of 15 mM and dodecylphosphonic acid at a ratio of 0.045 mM. The process of applying the pigment | dye to the titanium oxide semiconductor layer using the number 7 bar coater, and air-drying was repeated twice. The total treatment time of the dye on the semiconductor layer was 10 minutes. After coating, the semiconductor layer was immersed in acetonitrile and rinsed under ultrasonic waves for 5 minutes. The degree of penetration of the dye was “◯” according to the evaluation criteria of Experimental Example 1.

(Experimental example 6)
Except for the dye supporting treatment, dye-sensitized solar cells were prepared under the same conditions as in Experimental Example 4, and the photoelectric conversion efficiency was evaluated. In this experiment example, Z907 dye and dodecylphosphonic acid were dissolved in a solvent in which acetonitrile (MeCN) and t-butanol (t-BuOH) were mixed at a ratio of 1: 1, and dissolved in 3 mM and 0.045 mM rings, respectively. To prepare a dye solution. The titanium oxide semiconductor layer was immersed in a dye solution having a temperature of 25 ° C., and subjected to ultrasonic treatment for 10 minutes as a dye supporting process. After the titanium oxide semiconductor layer was taken out from the dye solution, it was immediately rinsed with acetonitrile for 1 minute to remove unsupported dye. The degree of penetration of the dye was “◯” according to the evaluation criteria of Experimental Example 1.

(Experimental example 7)
Except for the dye supporting treatment, dye-sensitized solar cells were prepared under the same conditions as in Experimental Example 4, and the photoelectric conversion efficiency was evaluated. In this experimental example, 0.3 mM of Z907 dye and 0.045 mM of dodecylphosphonic acid are dissolved in a solvent in which acetonitrile (MeCN) and t-butanol (t-BuOH) are mixed at a ratio of 1: 1 to obtain a dye solution. Was prepared. The titanium oxide semiconductor layer was immersed in the dye solution and allowed to stand at room temperature for 22 hours. After the semiconductor layer was lifted from the dye solution, it was immediately immersed in acetonitrile for 1 minute to wash the unsupported dye and let it air dry. The degree of penetration of the dye was “◯” according to the evaluation criteria of Experimental Example 1.

  The evaluation results of Experimental Examples 4 to 7 are shown in Table 2. Here, the photoelectric change rate of the cell according to each experimental example is expressed as a relative value with respect to the photoelectric conversion efficiency of the cell according to experimental example 7.

  As shown in Table 2, according to Experimental Examples 4 to 6, the photoelectric conversion efficiency equivalent to that of the cell according to Experimental Example 7 can be obtained in a much shorter time than Experimental Example 7. In addition, according to Experimental Examples 4 and 5, since the coating method is adopted for the dye-supporting treatment, compared with the immersion method as in Experimental Examples 6 and 7, it is not necessary to manage the solution of the dye. A stable dye-carrying treatment can be performed.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, in the above embodiment, the electrode substrate 10 having a laminated structure of the base material 11, the transparent electrode layer 12, and the semiconductor layer 13 has been described as an example. However, the configuration of the electrode substrate 10 is limited to the above example. However, for example, the present invention is applicable to the electrode substrate 10 having the configuration shown in FIGS.

  The electrode substrate shown in FIG. 7 has a laminated structure of a base material 11, a semiconductor layer 13, and a back contact layer 17. The back contact layer 17 is an electrode layer for taking out charges from the semiconductor layer 13 to an external circuit, and has a sheet resistance of 1 kΩ / □ or less. Moreover, in order to make electrolyte solution and the semiconductor layer 13 contact, it has a hole of 1 nm-1000 micrometers. Examples of the constituent material of the back contact layer 17 include a metal mesh, a conductive woven fabric, a conductive polymer coating, a metal particle coating, and a metal thin film. As the metal, titanium, tungsten, molybdenum, nickel, chromium, tantalum, niobium, zirconium, stainless steel, and the like are suitable. Also in the electrode substrate having such a structure, after the back contact layer 17 is formed, the above-described dye supporting treatment is performed on the semiconductor layer 13.

  The electrode substrate shown in FIG. 8 has a laminated structure of a base material 11, a transparent electrode layer 12, a semiconductor layer 13, and an insulating layer 18. Further, the electrode substrate shown in FIG. 9 has a laminated structure of the base material 11, the semiconductor layer 13, the back contact layer 17, and the insulating layer 18. The insulating layer 18 has an electrical insulating function that prevents a short circuit between the counter electrode layer 15 (FIG. 1) and the semiconductor layer 13 or the back contact layer 17. In these electrode substrates, after the insulating layer 18 is formed, the above-described dye supporting treatment is performed on the semiconductor layer 13. For this reason, the insulating layer 18 is formed of a porous material. In addition, by forming the insulating layer 18 from a porous material, a circulation path for circulating the electrolyte component between the semiconductor layer and the counter electrode when a cell is configured by the electrode substrate is secured.

  In the electrode substrate shown in FIGS. 8 and 9, the insulating layer 18 may have a light reflecting function. Thereby, when light is irradiated from the substrate 11 side, the light that has not been absorbed by the semiconductor layer 13 by the insulating layer 18 can be reflected and returned to the semiconductor layer 13 again, thereby improving the photoelectric conversion efficiency. Can do. On the other hand, when irradiating light from the insulating layer 18 side, the insulating layer 18 needs to have transparency. Examples of the constituent material of the insulating layer 18 include metal oxides such as silica, titanium oxide, zirconium oxide, and aluminum oxide, or transparent resins such as PET, PC, PP (polypropylene), and PE (polyethylene).

  The electrode substrate shown in FIG. 10 has a laminated structure of a base material 11, a transparent electrode layer 12, a semiconductor layer 13, an insulating layer 18, and a counter electrode layer 19. The counter electrode layer 19 has a function of taking out charges generated in the semiconductor layer 13 through an electrolyte to an external circuit. In the electrode substrate, after the counter electrode layer 19 is formed, the above-described dye supporting treatment is performed on the semiconductor layer 13. For this reason, the counter electrode layer 19 is formed of a porous material. Further, by configuring the counter electrode layer 19 with a porous material, a circulation path for circulating the electrolyte component between the semiconductor layer and the counter electrode layer when a cell is configured with the electrode substrate is secured.

  In addition to the above-described configuration example of the electrode substrate, for example, the transparent electrode layer 12 is formed of a non-transparent metal material, or a mesh-like metal wiring layer is formed on the base of the transparent electrode layer 12, The sheet resistance may be reduced.

DESCRIPTION OF SYMBOLS 1 ... Dye-sensitized solar cell 10 ... Electrode substrate 11 ... Base material 12 ... Transparent electrode layer 13 ... Semiconductor layer

Claims (7)

Forming a semiconductor layer on the substrate;
A dye solution prepared by dissolving 5 mM or more of a photosensitizing dye in a first solvent having a contact angle with the surface of the semiconductor layer of 6 ° or less and a boiling point of 80 ° C. or more is applied to the surface of the semiconductor layer. ,
A method for producing a dye-sensitized solar cell, wherein the dye is supported on the semiconductor layer. A method for producing a dye-sensitized solar cell according to claim 1,
The step of supporting the dye on the semiconductor layer includes:
Infiltrating the dye solution into the semiconductor layer;
A method for producing a dye-sensitized solar cell, wherein the first solvent is dried. A method for producing a dye-sensitized solar cell according to claim 2,
The step of applying the dye solution is a method for manufacturing a dye-sensitized solar cell, in which the dye solution is applied to the surface of the semiconductor layer with a thickness of 150 μm or less. A method for producing a dye-sensitized solar cell according to claim 3,
The method for producing a dye-sensitized solar cell, wherein the solvent is an amide solvent. The method for producing a dye-sensitized solar cell according to claim 1, further comprising:
A method for producing a dye-sensitized solar cell, wherein the semiconductor layer supporting the dye is washed with a second solvent which is a good solvent for the dye. A method for producing a dye-sensitized solar cell according to claim 5,
The step of cleaning the semiconductor layer is a method for manufacturing a dye-sensitized solar cell in which the semiconductor layer is immersed in the second solvent. A method for producing a dye-sensitized solar cell according to claim 1,
The step of forming the semiconductor layer is a method for manufacturing a dye-sensitized solar cell, in which the semiconductor layer is formed in a stripe shape on the base material formed of a resin film.

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