JP2011195745A - Dye and dye-sensitized solar cell using the same - Google Patents

Abstract

【選択図】なしThe present invention provides a metal complex that has sensitivity to light in a wide range and can efficiently extract current, and also provides a good dye-sensitized oxide semiconductor electrode and a dye-sensitized solar cell using the metal complex.
ML1L2 [M is an element of group 8 to 10 on the periodic table, L1 is a terpyridine derivative; L2 is a pyridinecarboxylic acid derivative or the like. ] The metal complex dye represented by this. For example, a metal complex dye represented by the following formula, a semiconductor electrode using the complex, and a dye-sensitized solar cell.

[Selection figure] None

Description

  The present invention relates to a dye that efficiently absorbs solar energy and a solar cell using the same.

  Solar cells that can efficiently convert sunlight into electricity are attracting attention from the viewpoint of energy and environmental issues. The solar cells currently in practical use mainly use silicon, but these solar cells have a high production cost and have a big problem in the future spread. Therefore, research on a new type of solar cell that replaces a silicon-based solar cell is underway, and one of them is a dye sensitization that uses a metal oxide semiconductor such as titanium oxide in which a sensitizing dye is adsorbed instead of silicon as an electrode. There is a solar cell (Patent Document 1). Dye-sensitized solar cells have advantages such as less resource constraints and relatively low manufacturing costs, and are expected to be widely used. However, it is inferior to silicon-based solar cells in terms of energy conversion efficiency and durability, and improvements in these performances for practical use are being studied.

  In dye-sensitized solar cells, a ruthenium-polypyridine complex is often used as a dye, and it is known that power generation efficiency and durability greatly depend on the dye. Ruthenium-isothiocyanato complexes having a 2,2′-bipyridine derivative or a 2,2 ′: 6 ′, 2 ″ -terpyridine derivative as a ligand are particularly well known as those having high energy conversion efficiency (non-patent Document 1 and Non-patent document 2).

For practical application of dye-sensitized solar cells, further improvement in conversion efficiency, durability and the like becomes an important research subject. For this purpose, compounds used as sensitizing dyes such as ruthenium complexes are also required to have improved performance and stability to light and heat.
In order to improve the energy conversion efficiency, it can be said that development of a sensitizing dye capable of efficiently photoelectrically converting light in a wide range from the visible light region to the infrared light region is necessary. In terms of stability, the ruthenium-isothiocyanato complex having the polypyridine ligand mentioned above pointed out the possibility of dissociation or isomerization of the monodentate ligand isothiocyanate by stimulation of heat or light. Yes. These dissociation and isomerization reactions are considered to reduce not only the stability of the metal complex dye but also the performance, and it can be said that the development of a metal complex dye containing no monodentate ligand is necessary.

Non-patent document 3 reports a ruthenium complex represented by the following formula 5 as a metal complex dye not containing a monodentate ligand. This compound is referred to as “Compound 1”. The energy conversion efficiency of the dye-sensitized solar cell incorporating the compound 1 is 2.1%, and the region where photoelectric conversion is possible is from 400 nm to 800 nm. With respect to this type of sensitizing dye, it is expected to improve the energy conversion efficiency and expand the region capable of photoelectric conversion to the longer wavelength side.

Japanese Patent No. 2664194

J. Am. Chem. Soc. 1993, 115, 6382-6390 J. Am. Chem. Soc. 2001, 123, 1613-1624 Chem.Commun.2007, 1907-1909

  The present invention has been made in view of the above-described situation in the prior art, and an object of the present invention is to provide a metal complex dye having a novel structure that is sensitive to a wide range of light and that can efficiently extract current. It is another object of the present invention to provide a good dye-sensitized oxide semiconductor electrode and a dye-sensitized solar cell using the metal complex dye.

［式中、Mは周期律表上の8から10族の元素であって、L¹は下記一般式（２）で表される配位子であり、L²は下記一般式（３）で表される配位子であり、一般式（２）は、

（式中、A¹〜A³はそれぞれ独立にカルボキシ基、スルホン酸基、リン酸基、若しくはホウ酸基、又はこれらの塩に相当する基であり、R¹〜R³はそれぞれ独立に置換基であり、m1〜m3はそれぞれ独立に0〜3の整数であり（ただしm1〜m3はすべて同時に0になることはない。）、n1〜n3はそれぞれ独立に0〜3の整数である。ただしm1+n1≦4であり、m2+n2≦3であり、m3+n3≦4である。）で表記され、一般式（３）は、

（式中、Zは含窒素芳香環を形成する原子群である。）で表記される。］

上記一般式（１）中の一般式（３）で表される配位子L²のうち、好ましいものの例としては、以下の一般式（４）であらわされる配位子が挙げられる。

（式中、R⁴は置換基であり、n4は0〜3の整数である。）
また、上記一般式（１）において、Mは、ルテニウムであることがとくに好ましい。
さらに、本発明は、当該金属錯体色素が酸化物半導体に吸着されてなる色素増感金属酸化物半導体電極を提供する。
さらにまた、本発明は、導電性支持体上に形成された当該色素増感金属酸化物半導体電極とその対極、及びそれらの電極に接触するレドックス電解質とから構成される色素増感太陽電池を提供する。 In order to solve the above problems, the present invention provides a novel metal complex dye represented by the following general formula (1).
General formula (1)

[Wherein M is a group 8 to 10 element on the periodic table, L ¹ is a ligand represented by the following general formula (2), and L ² is a general formula (3) A ligand represented by the general formula (2):

(In the formula, A ^{1 to} A ³ are each independently a carboxy group, a sulfonic acid group, a phosphoric acid group, a boric acid group, or a group corresponding to a salt thereof, and R ^{1 to} R ³ are each independently substituted. M1 to m3 are each independently an integer of 0 to 3 (however, m1 to m3 are not all 0 at the same time), and n1 to n3 are each independently an integer of 0 to 3. However, m1 + n1 ≦ 4, m2 + n2 ≦ 3, and m3 + n3 ≦ 4), and the general formula (3) is

(Wherein Z is an atomic group forming a nitrogen-containing aromatic ring). ]

Of the ligands L ² represented by the general formula (3) in the general formula (1), a preferable example is a ligand represented by the following general formula (4).

(In the formula, R ⁴ is a substituent, and n ⁴ is an integer of 0 to 3.)
In the general formula (1), M is particularly preferably ruthenium.
Furthermore, the present invention provides a dye-sensitized metal oxide semiconductor electrode in which the metal complex dye is adsorbed on an oxide semiconductor.
Furthermore, the present invention provides a dye-sensitized solar cell comprising the dye-sensitized metal oxide semiconductor electrode formed on a conductive support, a counter electrode thereof, and a redox electrolyte in contact with the electrode. To do.

  The metal complex dye of the present invention has sensitivity to a wide range of light and can efficiently extract current. For this reason, the dye-sensitized metal oxide semiconductor electrode and dye-sensitized solar cell using this can achieve favorable photoelectric conversion efficiency.

［式中、Mは周期律表上の8から10族の元素であって、L¹は下記一般式（２）で表される配位子であり、L²は下記一般式（３）で表される配位子であり、一般式（２）は、

（式中、A¹〜A³はそれぞれ独立にカルボキシ基、スルホン酸基、リン酸基、若しくはホウ酸基、又はこれらの塩に相当する基であり、R¹〜R³はそれぞれ独立に置換基であり、m1〜m3はそれぞれ独立に0〜3の整数であり（ただしm1〜m3はすべて同時に0になることはない。）、n1〜n3はそれぞれ独立に0〜3の整数である。ただしm1+n1≦4であり、m2+n2≦3であり、m3+n3≦4である。）で表記され、 一般式（３）は、

（式中、Zは含窒素芳香環を形成する原子群である。）で表記される。］
上記一般式（１）中の一般式（３）で表される配位子L²のうち、好ましいものの例としては、以下の一般式（４）であらわされる配位子が挙げられる。

（式中、R⁴は置換基であり、n4は0〜3の整数である。） The dye of the present invention can be used as a sensitizer for modifying a metal oxide semiconductor of a dye-sensitized solar cell. In the dye-sensitized solar cell of the present invention, a well-known electrode such as a platinum electrode is used as the counter electrode. A well-known redox electrolyte in contact with these electrodes can also be used.
The metal complex dye of the present invention is
General formula (1)

[Wherein M is a group 8 to 10 element on the periodic table, L ¹ is a ligand represented by the following general formula (2), and L ² is a general formula (3) A ligand represented by the general formula (2):

(In the formula, A ^{1 to} A ³ are each independently a carboxy group, a sulfonic acid group, a phosphoric acid group, a boric acid group, or a group corresponding to a salt thereof, and R ^{1 to} R ³ are each independently substituted. M1 to m3 are each independently an integer of 0 to 3 (however, m1 to m3 are not all 0 at the same time), and n1 to n3 are each independently an integer of 0 to 3. However, m1 + n1 ≦ 4, m2 + n2 ≦ 3, and m3 + n3 ≦ 4.) General formula (3) is

(Wherein Z is an atomic group forming a nitrogen-containing aromatic ring). ]
Of the ligands L ² represented by the general formula (3) in the general formula (1), a preferable example is a ligand represented by the following general formula (4).

(In the formula, R ⁴ is a substituent, and n ⁴ is an integer of 0 to 3.)

Examples of M in the above formula (1) include iron, cobalt, nickel, ruthenium, osmium, iridium, and platinum. Of these, ruthenium is particularly preferable.
A ¹ , A ² and A ³ in the above formula (2) are each independently a carboxy group, a sulfonic acid group, a phosphoric acid group, a boric acid group, or a group corresponding to a salt thereof. It is preferably a carboxy group or a salt thereof.
When A ¹ , A ² , or A ³ is a salt, the counter cation is ammonium ion, dimethyl ammonium ion, diethyl ammonium ion, tetramethyl ammonium ion, tetraethyl ammonium ion, tetrapropyl ammonium ion, tetrabutyl ammonium ion, sodium An ion, a potassium ion, etc. can be mentioned, Preferably it is a tetrabutylammonium ion.
R ¹ , R ² and R ³ in the above formula (2) are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, Aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen atom, cyano group, heterocyclic group Etc.

Specific examples of the structure of L ¹ represented by the formula (2) include ligands represented by the following formulas (6) to (8).

In the above formula (3), Z represents an atomic group forming a nitrogen-containing aromatic ring. The nitrogen-containing aromatic ring formed by Z is preferably a 4-10 membered ring, more preferably a 5-6 membered ring. The nitrogen-containing aromatic ring preferably has 2 to 30 carbon atoms, more preferably 4 to 10 carbon atoms. Examples of the nitrogen-containing aromatic ring formed by Z include pyridine, pyrazine, pyrimidine, quinoline, isoquinoline, imidazole, thiazole, isothiazole, oxazole, triazole, oxadiazole, thiadiazole and the like.
The ring formed by Z may have a substituent, and preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group. Group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen atom, cyano group, hetero And a ring group.

In the above formula (4), R ⁴ is preferably an alkyl group, alkenyl group, alkynyl group, aryl group, amino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group. , Acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, halogen atom, cyano group, heterocyclic group and the like.

Preferable examples of L ² represented by formula (3) or (4) include, for example, ligands represented by the following formulas (9) to (30).

Specific examples of the metal complex dye of the present invention include those represented by the following formulas (31) to (34).

The method for producing a metal complex dye of the present invention includes, for example, reacting 4,4 ′, 4 ″ -trimethoxycarbonyl-2,2 ′: 6 ′, 2 ″ -terpyridine (L ³ ) with ruthenium trichloride in advance. Then, a [RuL ³ Cl ₃ ] complex to be a skeleton is synthesized, and L ² is introduced into the complex. The [RuL ³ Cl ₃ ] complex is a known substance and can be synthesized with reference to, for example, J. Am. Chem. Soc. 123 (2001) 1613. The intermediate obtained from the reaction of [RuL ³ Cl ₃ ] complex with L ² ([Ru L ² L ³ ] complex) is composed of [RuL ³ Cl ₃ ] complex, L ² , lithium chloride, and triethylamine ethanol. The solution is refluxed at 100 ° C. for 2-8 hours, then cooled to room temperature, and the resulting solid product is sufficiently washed with ethanol and dried.

The target metal complex dye is obtained by dissolving [Ru L ² L ³ ] complex and triethylamine in dimethylformamide and pure water and refluxing at 110 to 120 ° C. for 20 to 24 hours. The target metal complex dye can be obtained by cooling the reaction mixture and purifying the solid product from which the solvent has been removed by column chromatography.

The dye-sensitized solar cell of the present invention using the metal complex dye of the present invention comprises a dye-sensitized metal oxide semiconductor electrode formed on a conductive support, an electrolyte, and a counter electrode, which are sequentially laminated. The metal complex dye of the present invention is chemisorbed on the sensitized metal oxide semiconductor electrode.
As the conductive support, a metal or glass or plastic having a conductive layer on the surface can be suitably used. Examples of the conductive layer include metals such as gold, platinum, silver, copper, and indium, conductive carbon, indium tin composite compounds, tin oxide doped with fluorine, and the like. Using these conductive materials, a conductive layer can be formed on the support surface by a conventional method. Further, when the conductive support is a light receiving surface, it is preferably transparent.

  Examples of the material constituting the oxide semiconductor electrode include titanium oxide, niobium oxide, zinc oxide, tin oxide, tungsten oxide, and indium oxide. Of these, titanium oxide, niobium oxide and tin oxide are preferable, and titanium oxide is particularly preferable. There is no limitation on the method of forming the oxide semiconductor electrode. For example, fine particles of oxide to be an oxide semiconductor electrode are formed, suspended in a suitable solvent, and applied onto transparent conductive glass. It can manufacture by the method of heating, after removing.

The method for chemically adsorbing the dye of the present invention to the oxide thin film electrode is not particularly limited, and a known method can be employed. For example, the oxide semiconductor electrode obtained by the above method can be immersed in a solution containing the metal complex dye of the present invention. The solvent used here is not particularly limited as long as it dissolves the metal complex dye, and is preferably methanol, ethanol, butanol, acetonitrile, acetone, diethyl ether, or a mixed solvent in which they are combined. The concentration of the metal complex dye solution is preferably about 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol / liter. The immersion time can be appropriately adjusted according to the metal complex dye used, the type of solvent, the concentration of the solution, and the like. The immersion time is preferably 0.5 to 50 hours, more preferably 2 to 25 hours. As temperature at the time of immersion, it is preferable that it is 0-100 degreeC, and 10-50 degreeC is still more preferable.

The electrolyte is composed of a conductive material that can transport electrons, holes, and ions. Among the conductive materials, an ionic conductor is preferable, and a solution, solid, or ionic liquid containing a redox system can be used. Specifically, redox systems include I ⁻ / I ^3- system, Br ^2- / Br ^3- system, Co ²⁺ / Co ³⁺ system, Fe ²⁺ / Fe ³⁺ system, etc. Examples thereof include nitrile compounds such as acetonitrile and carbonate compounds such as propylene carbonate. Liquid electrolyte additives include conventionally used nitrogen-containing aromatic compounds such as 4-tert-butylpyridine or imidazole salts such as (1,2-dimethyl-3-propyl) imidazolium iodide. These additives may be added to the liquid electrolyte at a concentration of about 0.1 to 1.5 mol / liter.

  The counter electrode is not particularly limited as long as it has conductivity. For example, a material obtained by depositing platinum on the surface of a conductive support or a material obtained by attaching conductive carbon can be preferably used.

  In order to prevent contact between the dye-sensitized semiconductor electrode and the counter electrode, a spacer may be used. Examples of the spacer include a polymer film such as polyethylene.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
[RuL ³ Cl ₃ ] complex (200 mg) (L ³ is 4,4 ′, 4 ″ -trimethoxycarbonyl-2,2 ′: 6 ′, 2 ″ -terpyridine), 2,6-pyridinedicarboxylic acid (54 mg) and lithium chloride (276 mg) are dissolved in ethanol and triethylamine, and then heated to reflux. The reaction mixture is cooled and then filtered. The filtrate was washed thoroughly with ethanol to give 210 mg of product. Analysis by ¹ H-NMR and ESI-MS revealed that this product was represented by the following formula (35). This product is referred to as “Compound 2”.

Example 2
Compound 2 (100 mg) and triethylamine are dissolved in dimethylformamide and water, and then heated to reflux. The residue after evaporation of the solvent was purified by column chromatography to give 42 mg of product. Analysis by ¹ H-NMR and ESI-MS revealed that this product was represented by the following formula (36). This product is referred to as “Compound 3”.

Example 3
The metal oxide semiconductor electrode was produced according to the method described in Coord. Chem. Rev. 2004, 248, 1381-1389. Specifically, a titanium oxide porous film (thickness is 36 μm, area is 0 μm) as a semiconductor layer on the surface of the transparent conductive glass on which fluorine oxide as a transparent conductive support is deposited on the glass surface. .25 cm ² ) was used.

The dye-sensitized metal oxide semiconductor electrode was prepared by immersing the metal oxide semiconductor electrode produced by the above method in an ethanol solution (1 × 10 ⁻⁴ mol / liter) of the compound 3 obtained in Example 2 for 24 hours. Formed. A polyethylene film spacer and an electrolyte solution were sandwiched between the semiconductor electrode and a counter electrode obtained by depositing platinum on the surface of the conductive glass to obtain a dye-sensitized solar cell. As electrolyte solutions, lithium iodide (0.1 mol / liter), iodine (0.05 mol / liter), (1,2-dimethyl-3-propyl) imidazolium iodide (0.6 mol / liter) Acetonitrile solution containing 4-tert-butylpyridine (0.05 mol / liter) was used. Solar cell performance was evaluated using a solar simulator (AM1.5, 100 mW cm ⁻² ). As a result, a short-circuit current of 16.3 mA cm ⁻² , an open-circuit voltage of 0.55 V, a fill factor of 0.69, and an energy conversion efficiency of 6.2% were obtained. Moreover, the region where photoelectric conversion of this solar cell is possible is from 400 nm to 900 nm, and the region where photoelectric conversion is possible compared with Compound 1 was able to be extended to the long wavelength side.

Example 4
[RuL ³ Cl ₃ ] complex (200 mg) (L ³ is 4,4 ′, 4 ″ -trimethoxycarbonyl-2,2 ′: 6 ′, 2′-terpyridine), 4-decyloxy-2,6-pyridine Dicarboxylic acid (105 mg) and lithium chloride (276 mg) are dissolved in ethanol and triethylamine, then heated to reflux, the reaction mixture is cooled and filtered, and the filtrate is washed thoroughly with ethanol to yield 180 mg. Analysis by ¹ H-NMR and ESI-MS revealed that the product was represented by the following formula (37), which was referred to as “compound 4”. .

Example 5
Compound 4 (100 mg) and triethylamine are dissolved in dimethylformamide and water, and then heated to reflux. The residue after evaporation of the solvent was purified by column chromatography to obtain 57 mg of product. Analysis by ¹ H-NMR and ESI-MS revealed that this product was represented by the following formula (38). This product is referred to as “Compound 5”.

Example 6
The metal oxide semiconductor electrode produced by the method described in Example 3 was immersed in an ethanol solution (1 × 10 ⁻⁴ mol / liter) of Compound 5 obtained in Example 5 for 24 hours, thereby sensitizing the dye. A metal oxide semiconductor electrode was formed. A polyethylene film spacer and an electrolyte solution were sandwiched between the semiconductor electrode and a counter electrode obtained by depositing platinum on the surface of the conductive glass to obtain a dye-sensitized solar cell. As electrolyte solutions, lithium iodide (0.1 mol / liter), iodine (0.05 mol / liter), (1,2-dimethyl-3-propyl) imidazolium iodide (0.6 mol / liter) Acetonitrile solution containing 4-tert-butylpyridine (0.1 mol / liter) was used. Solar cell performance was evaluated using a solar simulator (AM1.5, 100 mW cm ⁻² ). As a result, a short-circuit current of 14.1 mA cm ⁻² , an open-circuit voltage of 0.60 V, a fill factor of 0.66, and an energy conversion efficiency of 5.6% were obtained. Moreover, the area | region which can perform photoelectric conversion of this solar cell is 400 nm to 900 nm, and compared with the compound 1, the area | region which can be photoelectrically converted was able to be extended to the long wavelength side.

  From the above results, it was confirmed that Compound 3 and Compound 5 were effective as dyes applicable to the electrode of the dye-sensitized solar cell.

  The present invention is a dye that efficiently absorbs sunlight energy in a wide wavelength region, and a solar cell using the same, and has high industrial utility value.

Claims (5)

General formula (1)

[Wherein M is a group 8 to 10 element on the periodic table, L ¹ is a ligand represented by the following general formula (2), and L ² is a general formula (3) A ligand represented by the general formula (2):

(In the formula, A ^{1 to} A ³ are each independently a carboxy group, a sulfonic acid group, a phosphoric acid group, a boric acid group, or a group corresponding to a salt thereof, and R ^{1 to} R ³ are each independently substituted. M1 to m3 are each independently an integer of 0 to 3 (however, m1 to m3 are not all 0 at the same time), and n1 to n3 are each independently an integer of 0 to 3. However, m1 + n1 ≦ 4, m2 + n2 ≦ 3, and m3 + n3 ≦ 4), and the general formula (3) is

(Wherein Z is an atomic group forming a nitrogen-containing aromatic ring). ] The metal complex dye represented by this. General formula (1)

[Wherein M is a group 8 to 10 element on the periodic table, L ¹ is a ligand represented by the following general formula (2), and L ² is a general formula (4) A ligand represented by the general formula (2):

(In the formula, A ^{1 to} A ³ are each independently a carboxy group, a sulfonic acid group, a phosphoric acid group, a boric acid group, or a group corresponding to a salt thereof, and R ^{1 to} R ³ are each independently substituted. M1 to m3 are each independently an integer of 0 to 3 (however, m1 to m3 are not all 0 at the same time), and n1 to n3 are each independently an integer of 0 to 3. However, m1 + n1 ≦ 4, m2 + n2 ≦ 3, and m3 + n3 ≦ 4)), and the general formula (4) is

(Wherein R ⁴ is a substituent, and n4 is an integer of 0 to 3). The metal complex dye of Claim 1 represented by these.   The metal complex dye according to claim 1, wherein M is ruthenium.   A dye-sensitized metal oxide semiconductor electrode, wherein the metal complex dye according to claim 1 is adsorbed on an oxide semiconductor.   A dye-sensitized solar cell comprising the dye-sensitized metal oxide semiconductor electrode of claim 4 formed on a conductive support, a counter electrode thereof, and a redox electrolyte in contact with the electrode.