JP2013214381A - Photosensitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitizing dye material having a strong absorption band in an infrared region.SOLUTION: The photosensitizer has a structure represented by the general formula (1) in each molecule. In the general formula (1), Rto Reach independently represent H, a carbonyl-containing group, a phosphate ester group, a C1-C30 alkyl group, a C2-C30 alkenyl group, a C1-C30 alkoxyalkyl group, a C1-C30 aminoalkyl group, a C1-C30 perfluoroalkyl group, a C6-C30 aryl group, a C7-C30 aralkyl group, or an alkyl group, alkenyl group, aryl group or aralkyl group that has a carbonyl group.

Description

The present invention relates to a photosensitizer, and particularly to a photosensitizer that is suitably used for a dye-sensitized solar cell.

  The dye-sensitized solar cell element announced by Gretzell et al. In 1991 is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode, and can obtain performance equivalent to that of a silicon solar cell. Has been reported (see Non-Patent Document 1). Since this method can use an inexpensive oxide semiconductor such as titania without purifying it with high purity, it can provide an inexpensive dye-sensitized solar cell, and the absorption of the dye is broad. It has the advantage of being able to convert light in almost all areas into electricity, and is attracting attention. However, a known ruthenium complex dye absorbs visible light but hardly absorbs infrared light having a wavelength longer than 700 nm, and thus has low photoelectric conversion characteristics in the infrared region. Therefore, in order to further increase the conversion efficiency, development of a dye having absorption not only in the visible light but also in the infrared region has been desired.

  On the other hand, the black die can absorb light up to 920 nm, but has a small extinction coefficient. Therefore, in order to obtain a high current value, it is necessary to increase the amount adsorbed on the titanium oxide porous thin film. Although there are various methods for increasing the amount of adsorption to the titanium oxide porous thin film, it is generally possible to increase the thickness of the thin film (see Non-Patent Documents 2 and 3). When the thickness of the thin film is increased, the conversion efficiency cannot be greatly increased because the open-circuit voltage value is decreased and the FF is decreased due to an increase in reverse electron transfer and a decrease in the electron density in the thin film.

  There is also a report of using a complex using an imidazophenanthroline ligand as a solar cell, but sufficient efficiency has not been achieved (see Patent Document 1). Furthermore, in black dyes and N719 dyes, it has been reported that the orbital energy of molecules increases and a high photoelectric conversion characteristic can be obtained by forming a part of the —COOH group of the photosensitizing dye as a salt with a cation. (See Non-Patent Document 3).

  The present inventors have succeeded in developing a photosensitizer having a triallylamine derivative in response to such circumstances, and succeeded in obtaining high photoelectric conversion characteristics in the dye-sensitized solar cell (see Patent Document 2). ). On the other hand, nickel complex dyes having a dithiolene skeleton are known to have strong absorbers in the near-infrared region. Near-infrared filters for electronic equipment and photographs, protective glasses and sunglasses, heat ray shielding films, agricultural films Various uses such as optical disks, electrophotographic photoreceptors, solar heat storage materials have been proposed (see Patent Document 3 and Non-Patent Document 4).

International Publication No. 2007/006026 JP 2009-280789 A Japanese Patent Laid-Open No. 07-041492

B. O'Regan, M. Gratzel, "Nature" (UK), 1991, 353, p. 737 M. Gratzel, “Journal of American Chemical Society” (USA), 2001, 123, p. 1613 M. Gratzel, “Inorganic Chemistry” (USA), 1999, 38, p. 6298 Deplano et al., “Inorganic Chemistry”, (USA), 1997, 36, p. 1218

  An object of the present invention is to obtain high conversion efficiency by using the infrared region in a dye-sensitized solar cell, and more specifically, a dye material that can use the infrared region, particularly strong in the infrared region. It is to provide a dye material having an absorption band. In particular, it is to provide a dye material for a tandem dye-sensitized solar cell in which a plurality of cells are combined.

As a result of intensive studies, the present inventors have found that a dye material based on a Ni metal complex dye containing a dithiolene skeleton (see Patent Document 3 and Non-Patent Document 4) can solve the above problems. That is, according to the present invention, the following dye sensitizers are provided.

[1] A photosensitizer having a structure represented by the general formula (1) in one molecule.


In general formula (1), R ^{1 to} R ⁴ are each independently H, a carbonyl-containing group, a phosphate ester group, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or 1 carbon atom. An alkoxyalkyl group having -30 carbon atoms, an aminoalkyl group having 1-30 carbon atoms, a perfluoroalkyl group having 1-30 carbon atoms, an aryl group having 6-30 carbon atoms, an aralkyl group having 7-30 carbon atoms, or a carbonyl group. Represents an alkyl group, an alkenyl group, an aryl group or an aralkyl group.

[2] Light according to [1] for forming the general formula (1) ^R 1 ^{R 1} and ^{R 2} in to R ^4, and aromatic or heterocyclic ring ^{R 3} and ^{R 4} are each bonded in the Sensitizer.

[3] The photosensitizer according to the above [1] or [2], which has a large absorption coefficient in the near infrared region.

It is the figure which showed the ultraviolet visible absorption spectrum in the dichloromethane of the photosensitizer 1 in Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

The photosensitizer of the present embodiment is a compound (Ni complex dye) having a structure represented by the general formula (1) in one molecule.


In general formula (I), R ^{1 to} R ⁵ are each independently H, a carbonyl-containing group, a phosphate ester group, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or 1 carbon atom. An alkoxyalkyl group having -30 carbon atoms, an aminoalkyl group having 1-30 carbon atoms, a perfluoroalkyl group having 1-30 carbon atoms, an aryl group having 6-30 carbon atoms, an aralkyl group having 7-30 carbon atoms, or a carbonyl group. Represents an alkyl group, an alkenyl group, an aryl group or an aralkyl group.

As a compound (photosensitizer) represented by the general formula (1) that satisfies the above conditions, R ¹ and R ² and R ³ and R ⁴ are bonded to each other to form an aromatic ring or a heterocyclic ring, and A compound having at least one carboxylic acid moiety in the molecule as an adsorption site for an electrode such as a metal oxide is preferable. In addition, the compound (photosensitizer) represented by General formula (1) is not limited to these, The following compounds may be sufficient.

A method for synthesizing the photosensitizer of this embodiment will be described. Incidentally, the photosensitizer of the present embodiment is represented by NiL ₂ when expressed using the ligand L. First, a method in which a ligand L is sequentially reacted with a nickel raw material is preferably used. As the nickel raw material, nickel (II) salts such as nickel chloride and nickel perchlorate can be used. As the ligand L, dithiolene containing an aromatic ring moiety is preferably used as shown in the following general formula (11).

  As the reaction solvent, a general organic solvent can be used, and preferably, acetone, a halogen-based solvent such as chloroform and dichloromethane, and an aromatic solvent such as toluene are used. Although reaction temperature is not specifically limited, In order to advance reaction, heating is preferable and it is especially preferable to carry out in the range of 50-100 degreeC. For heating, an oil bath, a water bath, a microwave heating device, or the like can be used. Although reaction time is not specifically limited, Usually, it is 1 minute-several days, Preferably it is 10 minutes-1 day, It is preferable to change time with a heating apparatus.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Example 1 is an example corresponding to the first embodiment. As shown in the following reaction scheme, compound 1 and compound 2 as precursors of ligand L, and then photosensitizer 1 were synthesized in this order.

<Synthesis of Compound 1>
Methyl isothiocyanate (0.03 mol) methyl 4-aminobenzoate (0.02 mol) was dissolved in acetone and refluxed overnight. After completion of the reaction, the mixture was allowed to cool and concentrated to dryness using a rotary evaporator to obtain Compound 1 as white crystals.

<Synthesis of Compound 2>
Compound 1 (0.9 mmol) was added to ethyl chloroglyoxylate (1.8 mmol) and refluxed in dehydrated chloroform for 1 hour. After completion of the reaction, the reaction mixture was allowed to cool and concentrated to dryness using a rotary evaporator. The residue was dissolved in dichloromethane and washed with water. The organic phase was concentrated to dryness using an evaporator to obtain yellow crystalline compound 2. Compound 2 was identified by ¹ H-NMR (300 MHz, dmso-d ₆ : 3.31 (s, 3H), 3.89 (s, 3H), 7.52 (d, 2H), 8.12 (D, 2H)).

<Synthesis of Photosensitizer 1>
Compound 2 (0.5 mmol) was dissolved in toluene, heated and stirred at 70 ° C. for a while, then Lawesson's reagent (0.9 mmol) was added, and the mixture was refluxed for 10 minutes. During this time, the color of the reaction solution changed from yellow to brown. Subsequently, nickel perchlorate hexahydrate (0.27 mmol) dissolved in a small amount of ethanol was added to the reaction solution and refluxed for 1 hour. After completion of the reaction, the mixture was allowed to cool, concentrated and dried using a rotary evaporator, and the resulting dark green solid was washed with ethanol and chloroform to obtain photosensitizer 1 which was a dark green solid.

<UV-visible absorption spectrum of photosensitizer 1>
FIG. 1 shows an ultraviolet-visible absorption spectrum of photosensitizer 1 in dichloromethane. The photosensitizer 1 of this example was confirmed to have a strong absorption band (λ _max = 1,010; ε = 110,000 M ⁻¹ cm ⁻¹ ) in the near infrared region. It has been confirmed that the dye-sensitized solar cell used in No. 1 has a large extinction coefficient as a dye material specialized in the near-infrared region, particularly a tandem dye-sensitized solar cell.

  The dye sensitizer of the present invention can be used for a dye-sensitized solar cell using light in the infrared region.

Claims (3)

The photosensitizer which has a structure represented by General formula (1) in 1 molecule.

(In General Formula (1), R ^{1 to} R ⁴ are each independently H, a carbonyl-containing group, a phosphate ester group, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or the number of carbon atoms. An alkoxyalkyl group having 1 to 30 carbon atoms, an aminoalkyl group having 1 to 30 carbon atoms, a perfluoroalkyl group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 30 carbon atoms, or a carbonyl group Represents an alkyl group, alkenyl group, aryl group or aralkyl group having ^{R 1} and ^{R 2,} and ^{R 3} and photosensitizer of claim 1 ^{wherein R 4} combine together to form an aromatic ring or heterocyclic ring in ^R 1 to R ⁴ in the general formula (1). The photosensitizer according to claim 1 or 2, which has a large absorption coefficient in the near infrared region.