JP4210054B2 - Dye-sensitized solar cell - Google Patents

Description

【００６４】
【発明の効果】
上記の結果より本発明の効果は明らかである。すなわち、本発明は、表面に色素が吸着された色素結合電極と、これと対をなす対向電極と、これらの電極に接触する電解質含有体とを有する色素増感型太陽電池であって、前記色素は、有機金属錯体であり、中心原子である金属イオンまたは金属原子に配位結合で結合している配位子を有し、前記電解質含有体には、前記色素が有する配位子と同一の化学種を含有させてなるように構成されているので、長期間の使用においても増感色素の構造が変化しにくく、耐久性の高い色素増感型太陽電池を提供することができる。
【図面の簡単な説明】
【図１】本発明の色素増感型太陽電池の模式的構成例を示した図面である。
【符号の説明】
１…色素増感型太陽電池
４…酸化物半導体膜
５…電解液
７…色素膜
１０…色素結合電極
２０…基板
２２…透明導電性層
３０…電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dye-sensitized solar cell including a dye-coupled electrode to which a sensitizing dye of an organometallic complex is bound, and in particular, the electrolyte-containing body has a predetermined relationship with the ligand of the organometallic complex used. In order to improve the durability of the battery.
[0002]
[Prior art]
Conventionally, wet solar cells including an oxide semiconductor electrode sensitized with a dye are known. According to Nature, 261 (1976) p.402, rose bengal was adsorbed as a sensitizing dye on the surface of a sintered disk formed by compression molding zinc oxide powder and sintering at 1300 ° C. for 1 hour. A solar cell using an oxide semiconductor electrode has been proposed.
[0003]
However, according to the current / voltage curve of the solar cell in the proposal, the current value at an electromotive voltage of 0.2 V is as small as about 25 μA.
[0004]
By the way, research on solar cells has progressed further in recent years, and a porous titanium dioxide film is formed on a transparent conductive film, a Ru dipyridyl complex is adsorbed on the surface as a sensitizing dye, and dye enhancement using iodine as an electron mediator. A sensitive wet solar cell has been reported by Gretzel et al. (Japanese Patent Laid-Open No. 01-220380).
[0005]
In the solar cell proposed by Gretzell et al., The dye that is excited by absorbing light supplies electrons to titanium oxide, the electrons move from the counter electrode to iodine, and the reduced iodide ions give electrons to the dye. To complete the cycle. Such a dye-sensitized solar cell is theoretically expected to have high efficiency, and it has been reported that an efficiency of about 7 to 10% was actually obtained. Further, such a solar cell is considered to be very advantageous in terms of cost as compared to a solar cell using a silicon semiconductor because both the oxide semiconductor and the dye used therein are inexpensive. Yes.
[0006]
[Problems to be solved by the invention]
In the conventionally known dye-sensitized solar cell, for example, a Ru-NCS complex compound is used as a sensitizing dye, and iodide ion is used as an electrolyte. Since the Ru complex can undergo a ligand exchange reaction, in such a combination, the NCS ligand is eliminated and a Ru-I complex is formed, and the conversion efficiency gradually decreases. There is a risk of doing.
[0007]
As a prior art, a dye-sensitized solar cell using an electrolyte solution in which a sensitizing dye to be attached to a semiconductor surface is dissolved in advance has been proposed (Japanese Patent Laid-Open No. 2000-331720). However, in this case, since the dye is present in the electrolytic solution, the electron transport function of the electrolyte is hindered, and the efficiency may be reduced. In addition, there is no action to suppress the decomposition of the dye itself, and the durability is not sufficient.
[0008]
Under such circumstances, the present invention was invented, and its purpose was to create a combination of a sensitizing dye and an electrolyte-containing body in which the ligand exchange of the sensitizing dye is difficult to proceed, and to be used for a long time. Is to provide a dye-sensitized solar cell with extremely little change in characteristics and excellent durability.
[0009]
[Means for Solving the Problems]
In order to solve such problems, the present invention provides a dye-sensitized dye having a dye-binding electrode having a dye adsorbed on its surface, a counter electrode paired with the dye-binding electrode, and an electrolyte-containing body that contacts these electrodes. In the solar cell, the dye is an organometallic complex, and has a metal ion that is a central atom or a ligand that is bonded to a metal atom by a coordinate bond, dye has the same species and the ligand is contained with the same species and the ligand, as is at least one coordinating solvent selected from among ketones and nitriles Composed.
[0010]
As a preferred embodiment of the present invention, the coordinating solvent is configured to be at least one selected from acetylacetone, acetonitrile, and 3-methoxypropionitrile .
[0015]
That is, according to the present invention, in a dye-sensitized solar cell using an organometallic complex as a sensitizing dye, the same chemical species as the ligand that the dye has an easy detachment is previously contained in the electrolyte-containing body.
[0016]
In such an environment, the elimination of the ligand of the sensitizing dye is extremely difficult. Moreover, even if desorption occurs, it tends to have the same structure as the original sensitizing dye. As a result, the sensitizing dye is unlikely to undergo structural changes even during long-term use, and a highly durable dye-sensitized solar cell can be provided.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the dye-sensitized solar cell of the present invention will be described in detail. FIG. 1 shows a schematic configuration example of the dye-sensitized solar cell of the present invention. As shown in FIG. 1, the dye-sensitized solar cell 1 of the present invention has a configuration in which two electrodes 10, 30 are arranged to face each other with an electrolyte-containing body 5 interposed therebetween, for example. One of the two electrodes 10 is a dye-coupled electrode 10 including a dye, which includes, for example, a substrate 20, a transparent conductive layer 22 formed thereon, and a conductive layer 22. An oxide semiconductor film 4 formed on the surface and a dye film 7 bonded to the surface of the oxide semiconductor film are included.
[0018]
In the present invention, the dye is an organometallic complex having a metal ion as a central atom or a ligand bonded to the metal atom by a coordinate bond, and the electrolyte-containing body 5 has a coordination that the dye has. The same chemical species (compound, ion, group) as the ligand are contained in advance.
[0019]
That is, the present invention is characterized in that the same chemical species as the ligand that the dye has is easily removed is previously contained in the electrolyte-containing body 5.
[0020]
In the present invention, the same compound as the ligand of the pigment previously contained in the electrolyte-containing body 5 is (1) a coordinating anion species or (2) a coordinating solvent (metal) A solvent capable of coordinating to
[0021]
(1) Coordinating anion species include halide ion, pseudohalide ion, sulfate ion, nitrate ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, acetate ion, hydroxide ion Etc.
[0022]
The halide ions, fluoride ions: F ^-, chloride ion: Cl ^-, bromide: Br ^-, iodide ion: I ^-, astatine hydride ion: At ^-, hexafluorosilicate ion: SiF _6, tetraiodo Mercuric acid ions: HgI _{4 and the} like are preferred examples.
[0023]
Preferable examples of pseudohalide ions include thiocyanate ion: NCS ⁻ , cyanide ion: CN ⁻ , cyanate ion: OCN ⁻ , isocyanate ion: ONC ⁻ , and azide ion: N ₃ ^— .
[0024]
Such a coordinating anion species is set to a concentration of 0.01 to 5 mol / L, preferably 0.1 to 1 mol / L in the electrolyte-containing body 5. If it is less than 0.01 mol / L, the effect of the present invention cannot be sufficiently obtained. On the other hand, if the concentration exceeds 5 mol / L, the organic solvent is saturated.
[0025]
(2) Examples of the coordinating solvent include ketones, nitriles, alcohols, pyridines, carboxylic acids, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, tetrahydrofuran, and water.
[0026]
Preferred examples of ketones include acetylacetone and acetone. Preferred examples of nitriles include acetonitrile and methoxypropionitrile. Preferred examples of alcohols include methanol, ethanol, propanol, butanol and the like. Preferable examples of pyridines include methylpyridine, ethylpyridine, propylpyridine, butylpyridine and the like. Preferred examples of the carboxylic acid include acetic acid and propionic acid.
[0027]
Such a coordinating solvent is set to a concentration of 50 to 99 wt%, preferably 70 to 95 wt% in the electrolyte-containing body 5. If it is less than 50 wt%, the effect of the present invention cannot be sufficiently obtained. On the other hand, if the concentration exceeds 99 wt%, the electrolyte concentration is too low and the electron transport function is degraded.
[0028]
The coordinating anion species and the coordinating solvent described above have a function of coordinating with a metal in the dye. On the other hand, the electrolyte-containing body 5 has conductivity as a supporting electrolyte (coordinating anion species) or has a function of dissolving the electrolyte as a solvent (coordinating solvent).
[0029]
By the way, the basic function of the electrolyte-containing body 5 in the present invention is to give and receive electrons so as to exert the function of a so-called battery, and the state is a so-called liquid state, solid state, molten salt state (imidazolium salt etc. Molten salt of: 100% electrolyte), quasi-solid state (gelled with a gelling agent or the like), etc.
[0030]
In the present invention, when the electrolyte-containing body 5 is in a liquid state, and the same chemical species as the ligand that the pigment easily has is contained in the electrolyte-containing body 5 as an electrolyte (coordinating anion species), There is no restriction | limiting in particular in the solvent used for the electrolyte containing body 5. FIG. In this case, the solvent may be an electrochemically inert solvent, for example, an organic solvent such as acetonitrile, propylene carbonate, or ethylene carbonate. Moreover, you may coexist a redox electrolyte. Examples of the redox electrolyte include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, and quinone / hydroquinone system. Such a redox electrolyte can be obtained by a conventionally known method. For example, an I ⁻ / I ₃ ⁻ based electrolyte can be obtained by mixing iodine ammonium salt and iodine.
[0031]
On the other hand, in the case where the same chemical species as the ligand that the dye has easily removed is contained in the electrolyte-containing body 5 as a solvent (coordinating solvent), the electrolyte used for the electrolyte-containing body 5 includes There is no particular limitation. As the electrolyte in this case, the above-described redox electrolyte is preferably used.
[0032]
Next, the dye-coupled electrode 10 including a dye will be described. As described above, this is, for example, the substrate 20, the transparent conductive layer 22 formed thereon, the oxide semiconductor film 4 formed on the surface of the conductive layer 22, and the oxide semiconductor film. It has a dye film 7 bonded to the surface.
[0033]
The substrate 20 is not particularly limited as long as it is a light-transmitting substrate. For example, a glass substrate, a transparent resin substrate, an inorganic transparent crystal body, or the like is used.
[0034]
As the transparent conductive layer 22, for example, a metal oxide conductor such as In ₂ O ₃ or SnO ₂ is preferably used.
[0035]
As the oxide semiconductor material constituting the oxide semiconductor film 4, various known materials are used. Specific examples include oxides of transition metals such as Ti, Nb, Zn, Sn, Zr, Y, La, and Ta, and perovskite oxides such as SrTiO ₃ and CaTiO ₃ . The oxide semiconductor material constituting the oxide semiconductor film 4 is preferably as fine as possible, and its average particle size is 200 nm or less, preferably 30 nm or less. For preferred specific production examples, see the examples below.
[0036]
On the oxide semiconductor film 4, a dye film 7 using the organometallic complex dye as described above is formed. The dye film 7 is preferably formed on the oxide semiconductor film 4 so as to chemically bond the dye as a monomolecular film. For this purpose, the entire substrate having the oxide semiconductor film 4 on the surface is immersed in a dye solution formed by dissolving the dye in an organic solvent, and the dye is reacted with, for example, a hydroxyl group of titanium in the oxide semiconductor film 4. Or the remaining alkoxide group may be substituted.
[0037]
The dye used in the present invention is preferably a dye that can be chemically bonded to the metal oxide constituting the oxide semiconductor film 4 (particularly the titanium oxide film), and has a carboxyl group, sulfonic acid group, phosphoric acid in the molecule. Those having a group or a hydroxyl group are preferred. Specific examples include Ru complexes such as bipyridyl Ru complexes, ta-pyridyl Ru complexes, phenanthroline Ru complexes, and bicinchoninic acid Ru complexes.
[0038]
In order to adsorb the dye as a single molecule on the surface of the titanium oxide film which is a preferred embodiment of the oxide semiconductor film 4, the titanium oxide film is immersed together with the substrate in a dye solution formed by dissolving the dye in an organic solvent. Good. In this case, in order for the dye solution to penetrate deeply into the titanium oxide film, which is a porous structure film, the film is subjected to reduced pressure treatment or heat treatment prior to immersion in the dye, so that bubbles contained in the film Is preferably removed in advance. The immersion time is about 30 minutes to 24 hours. In order to efficiently adsorb the dye, a reflux treatment may be performed. Further, the immersion treatment can be repeated a plurality of times as necessary. After the immersion treatment, the titanium oxide film adsorbed with the pigment is dried at room temperature to 80 ° C.
[0039]
In the present invention, the dye adsorbed on the titanium oxide film does not need to be one kind, and a plurality of dyes having different light absorption regions can be adsorbed as necessary. Thereby, light can be used efficiently. In order to adsorb a plurality of dyes to the film, a method of immersing the film in a solution containing a plurality of dyes, a method of preparing a plurality of dye solutions, and sequentially immersing the film in these solutions, and the like can be mentioned. In the solution in which the dye is dissolved in the organic solvent, any organic solvent can be used as long as it can dissolve the dye. Examples of such include methanol, ethanol, acetonitrile, dimethylformamide, dioxane, dichloromethane, toluene and the like. The concentration of the dye in the solution is about 1 to 200 mg, preferably about 10 to 100 mg, in 100 ml of the solution.
[0040]
The counter electrode 30 that forms a pair with the dye-coupled electrode 10 may be any conductive material, and any conductive material can be used. However, the reduction reaction of oxidized redox ions such as I ₃ ⁻ ions is possible. It is preferable to use a material having a catalytic ability to carry out the reaction at a sufficient speed. Examples of such a material include a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, and carbon.
[0041]
The solar cell 1 of the present invention is generally formed in a state where the dye-coupled electrode 10, the electrolyte-containing body 5 and the counter electrode 30 are housed in a case and sealed, or the whole is sealed with a resin. In this case, the electrode (dye-binding electrode) 10 to which the dye is bonded has a structure that receives light. In the battery having such a structure, when the dye-coupled electrode 10 is irradiated with sunlight or visible light equivalent to sunlight, a potential difference is generated between the dye-coupled electrode 10 and the electrode 30 facing the dye-coupled electrode 10, and both electrodes 10, 30. A current flows between them.
[0042]
【Example】
Next, the present invention will be described in more detail with reference to specific examples of the present invention.
[0043]
[Experimental Example I]
(Production of Examples 1 to 8)
Preparation of dye The sensitizing dye is composed of (4,4'-dicarboxylic acid-2,2'-bipyridine) ruthenium (II) dichloro skeleton and the chloro moiety in substance A shown in Table 1 below. A replacement structure was used. The synthesis was performed by a conventionally known method. That is, (4,4′-dicarboxylic acid-2,2′-bipyridine) ruthenium (II) dichloromethane and substance A were heated to reflux in dimethylformamide for 4 hours to obtain the desired dye.
[0044]
Preparation of titanium oxide sol solution Titanium oxide sol solution was prepared by hydrolyzing titanium isopropoxide as follows.
[0045]
125 ml of titanium isopropoxide was added to 750 ml of 0.1 M aqueous nitric acid solution with stirring. This was vigorously stirred at 80 ° C. for 8 hours. The resulting liquid was autoclaved at 230 ° C. for 16 hours in a Teflon pressure vessel. The sol solution containing the precipitate was resuspended by stirring. The precipitate that was not resuspended was removed by suction filtration, and the sol solution was concentrated with an evaporator until the titanium oxide concentration became 11 wt%. One drop of Triton X-100 was added to improve the paintability on the substrate.
[0046]
Next, titanium alkoxide was added to the sol solution as follows in order to prevent generation of cracks during the firing of the titanium oxide film and peeling of the film from the conductive surface.
[0047]
That is, while stirring the sol solution, an 80:20 mixed solution of di-iso-propoxy bis (acetylacetonato) titanium and acetylacetone was added little by little. After completion of the addition, the mixture was stirred for 1 hour.
[0048]
The sample was prepared with an addition amount of di-iso-propoxy bis (acetylacetonato) titanium of 3.4 g (10 wt% with respect to the titanium oxide fine particle weight).
[0049]
Production of dye-coupled electrode (titanium oxide electrode) A titanium oxide electrode was produced in the following manner using the titanium alkoxide-added sol solution prepared as described above.
[0050]
A square of 0.5 cm in length and 0.5 cm in width on the conductive film side of a conductive glass substrate (F-SnO ₂ , sheet resistance 10 Ω / □) having a length of 2.0 cm, a width of 1.5 cm, and a thickness of 1 mm. A masking tape having a thickness of 70 μm provided with a hole was attached, and 3 μl (microliter) of the titanium alkoxide-added sol solution was added to the end of the hole with a pipette.
[0051]
The sol solution was spread on a substrate by stretching using a glass plate having a flat edge. The film thus spread was dried in air for 30 minutes, and after drying, the masking tape was peeled off.
[0052]
Next, it baked for 30 minutes at 500 degreeC using the electric furnace. The heating rate was 2 ° C./min.
[0053]
After firing, when the substrate temperature dropped to 80 ° C., the sensitizing dye prepared in advance as described above was immersed in 20 ml of an anhydrous ethanol solution added at a concentration of 3 × 10 ⁻⁴ M and left for 12 hours. did.
[0054]
After standing, the titanium oxide electrode was taken out and washed with anhydrous acetonitrile. The titanium oxide film on the substrate became deep red due to the adsorbed ruthenium dye (preparation of dye-coupled electrode sample).
[0055]
Preparation <br/> counter electrode of the counter electrode, the conductive film face side of the conductive glass substrate with a hole of 1mmφ exist two places, was used as the sputtering platinum to a thickness of 100 nm.
[0056]
Preparation of electrolyte-containing body (electrolyte solution) When a coordinating anion species is used as the substance A as corresponding to the ligand of the sensitizing dye, the substance A is saturated with a 3-methoxypropionitrile solution. Was prepared. When using a coordinating solvent as the substance A, a solution of the substance A containing tetrapropylammonium iodide (0.45M) and iodine (0.06M) was prepared and used as an electrolyte solution.
[0057]
Production of solar cell A solar cell sample was produced and evaluated in the following manner using both the electrodes and the electrolyte-containing body.
[0058]
High Milan (thickness 50 μm) manufactured by Mitsui DuPont Polychemical Co., Ltd. was used as a spacer for bonding the dye-bonded electrode (titanium oxide electrode) as the working electrode and the counter electrode. In addition, when this spacer is bonded to the working electrode, a central portion overlapping with the dye-adsorbed titanium oxide film is perforated, and an electrolyte-containing body (electrolyte solution) containing a urea derivative in the perforated space portion. ) Can be stored. Using this, the titanium oxide film side of the working electrode adsorbed with the dye and the platinum-sputtered side of the counter electrode were bonded together.
[0059]
Thereafter, an electrolyte containing body (electrolyte solution) was introduced from one of the two holes previously formed in the counter electrode. The electrolyte-containing body (electrolyte solution) was left for a sufficient period of time so that it was introduced into the battery. Thereafter, one HiMilan and one cover glass were sequentially laminated as a sealing plate from the back side of the counter electrode to close the two holes, and the electrolyte-containing body (electrolyte solution) was sealed. Thus, various example samples shown in Table 1 were produced.
[0060]
(Production of Comparative Example 1 sample)
Using (4,4′-dicarboxylic acid-2,2′-bipyridine) ruthenium (II) dithiocyanate as the dye, tetrapropylammonium iodide (0.45 M) and iodine (0.06 M) are contained in the electrolyte solution. 3-methoxypropionitrile was used. Otherwise, the sample of Comparative Example 1 was produced in the same manner as the sample of Example 1 above.
[0061]
[Evaluation of battery characteristics]
Durability test A battery durability test was performed on each battery sample in the following manner.
When each battery sample was left standing at a temperature of 80 ° C. and a humidity of 50% RH, the change over time in the photocurrent density (Jsc) was measured, and the photocurrent density (Jsc) was −10% of the initial battery characteristics. Asked for time. This time was used as an index of durability. The larger this value, the better the durability at high temperatures after the battery is produced.
[0062]
The results are shown in Table 1 below.
[0063]
[Table 1]

[0064]
【The invention's effect】
The effects of the present invention are clear from the above results. That is, the present invention is a dye-sensitized solar cell having a dye-binding electrode having a dye adsorbed on its surface, a counter electrode paired therewith, and an electrolyte-containing body that contacts these electrodes, The dye is an organometallic complex and has a metal ion as a central atom or a ligand bonded to a metal atom by a coordinate bond, and the electrolyte-containing body has the same ligand as the dye Thus, the structure of the sensitizing dye hardly changes even after long-term use, and a highly durable dye-sensitized solar cell can be provided.
[Brief description of the drawings]
FIG. 1 is a drawing showing an example of a schematic configuration of a dye-sensitized solar cell of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Dye-sensitized solar cell 4 ... Oxide semiconductor film 5 ... Electrolytic solution 7 ... Dye film 10 ... Dye coupling electrode 20 ... Substrate 22 ... Transparent conductive layer 30 ... Electrode

Claims (2)

A dye-sensitized solar cell comprising a dye-binding electrode having a dye adsorbed on its surface, a counter electrode paired with the dye-binding electrode, and an electrolyte-containing body in contact with these electrodes,
The dye is an organometallic complex, and has a metal ion as a central atom or a ligand bonded to a metal atom by a coordinate bond,
Wherein the electrolyte inclusion, the same species and the ligand, wherein the dye has are contained,
The dye-sensitized solar cell, wherein the same chemical species as the ligand is at least one coordination solvent selected from ketones and nitriles . The dye-sensitized solar cell according to claim 1, wherein the coordinating solvent is at least one selected from acetylacetone, acetonitrile, and 3-methoxypropionitrile .

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