WO2014196325A1

WO2014196325A1 - Porphyrin complex and dye-sensitized solar cell

Info

Publication number: WO2014196325A1
Application number: PCT/JP2014/062804
Authority: WO
Inventors: 博今堀; 敬黒飛
Original assignee: 日本写真印刷株式会社; 国立大学法人京都大学
Priority date: 2013-06-06
Filing date: 2014-05-14
Publication date: 2014-12-11
Also published as: TW201509942A; JP2014237743A

Abstract

[Problem] To provide a porphyrin complex that has exceptional light collection characteristics, and that when employed as a sensitizing dye in a dye-sensitized solar cell, is able to improve the cell characteristics. [Solution] The present invention relates to a porphyrin complex comprising metal atoms and a porphyrin derivative. The porphyrin derivative has one attracting group and at least two electron-donating groups, which are bonded to the porphyrin ring. The attracting group is an arylethynyl group substituted with a functional group having attraction and electron-withdrawing properties (the aryl ring may have additional substituent groups). The at least two electron-donating groups are bonded to the porphyrin ring, in an asymmetric positional relationship with respect to the arylethynyl group.

Description

Porphyrin complex and dye-sensitized solar cell

The present invention relates to a porphyrin complex comprising a metal atom and a porphyrin derivative, and a dye-sensitized solar cell using the same.

Solar cells that can directly convert light energy into electric power are attracting attention as a renewable and clean energy source. Silicon solar cells are the mainstream of currently popular solar cells, but dye-sensitized solar cells using sensitizing dyes are superior in cost, manufacturability, design, and the like as compared to silicon solar cells. For this reason, research and development on this dye-sensitized solar cell has been vigorously conducted. Among dye-sensitized solar cells, it is known that energy conversion efficiency exceeding 10% can be achieved by using a sensitizing dye comprising a ruthenium complex. However, since ruthenium is an expensive and rare metal, the production cost tends to be relatively high, and there are also resource constraints. Therefore, development of a sensitizing dye that is less expensive and less resource-constrained is desired.

Porphyrin is a compound that has utility as a sensitizing dye in terms of ease of molecular design, a large extinction coefficient, and possibility of inexpensive synthesis. Therefore, in a dye-sensitized solar cell using a porphyrin complex containing a porphyrin derivative as a sensitizing dye, research for optimizing the molecular structure of the porphyrin derivative has been promoted with the aim of improving the light collecting property. For example, in US Patent Application Publication No. 2013/0042916 (Patent Document 1), when a diarylamino group is introduced into another meso position of a porphyrin ring in which at least one of four meso positions is substituted with a carboxyaryl group The influence of the number of substituents and the position of substitution on battery characteristics has been studied.

Patent Document 1, Fig. 1, Fig. 2, etc. show that the light collecting properties can be improved by increasing the number of diarylamino groups introduced into the meso position. Further, it has been shown that when two diarylamino groups are introduced at the meso position, the light condensing characteristic can be improved by using the trans type as compared with the cis type or bis type. On the other hand, when focusing on the overall battery characteristics based on energy conversion efficiency, short-circuit current density, open-circuit voltage, etc., the case where only one diarylamino group is introduced at the meso position is superior. It has been shown to have properties (Fig.5 to Fig.10, TABLE 1, etc.). Thus, referring to the examination of Patent Document 1, it can be seen that the increase in the number of substituents, which is a factor for improving the light collecting characteristics, did not always work effectively for improving the battery characteristics. For this reason, the room which can improve a battery characteristic further remained.

US Patent Application Publication No. 2013/0042916

Therefore, it is desired to realize a novel porphyrin complex that has excellent light collecting properties and can improve battery properties when used as a sensitizing dye in a dye-sensitized solar cell.

According to the study by the present inventors, a push-pull type molecule is introduced by introducing a substituent having a high electron-withdrawing property into the porphyrin ring as an adsorbing group for the electrode material and introducing a plurality of electron-donating groups into the porphyrin ring. It turned out that the charge mobility of a molecule | numerator increases by setting it as a structure. In addition, when the molecular structure of the porphyrin complex is symmetric, for example, when two electron donating groups are introduced so as to be in the trans type, the electron density at the molecular axis containing the electron-withdrawing adsorbing group Was found to be extremely low. Based on these new findings, earnest research with the expectation that if the electron density at the molecular axis containing the adsorbing group can be increased while the molecular structure of the porphyrin complex is made to be a push-pull type, the battery characteristics can be greatly improved. As a result, the present invention was completed.

According to the present invention, a characteristic configuration of a porphyrin complex comprising a metal atom and a porphyrin derivative coordinated to the metal atom is as follows:
The porphyrin derivative has one adsorbing group bonded to the porphyrin ring and at least two electron donating groups bonded to the porphyrin ring in a state of forming a π-conjugated system with the porphyrin ring,
The adsorptive group is an arylethynyl group substituted with an adsorptive and electron-withdrawing functional group (the aryl ring may further have a substituent),
At least two of the electron donating groups are bonded to the porphyrin ring in an asymmetric positional relationship with respect to the arylethynyl group.

According to this characteristic configuration, by adopting an arylethynyl group substituted with an adsorptive and electron-withdrawing functional group as an adsorbing group for the electrode material of the dye-sensitized solar cell, it is pushed by this and the electron-donating group.・ Pull-type molecular structure is realized. Therefore, the charge mobility of the molecule can be improved. In addition, the light collecting property can be effectively improved by using a plurality of electron donating groups.

At this time, by coupling a plurality of electron donating groups to the porphyrin ring in an asymmetric positional relationship with respect to the arylethynyl group, the π-conjugated system mainly composed of porphyrin can be expanded asymmetrically. Therefore, the electron density in the molecular axis containing the arylethynyl group can be increased. In addition, the arylethynyl group itself has a triple bond, and this triple bond is conjugated with the π electron of the porphyrin ring to further expand the π conjugated system, which can further improve the light collecting property. it can. Moreover, since the electron density in the triple bond part of an aryl ethynyl group increases, the adsorptivity with respect to an electrode material and electron injection efficiency can be improved effectively. Therefore, by using this porphyrin complex as a sensitizing dye in a dye-sensitized solar cell, battery characteristics such as energy conversion efficiency and durability can be effectively improved.

Hereinafter, preferred embodiments of the present invention will be described.

In one embodiment, the aryl ethynyl group is bonded to one of the four meso positions of the porphyrin ring, and the two electron donating groups are bonded to the meso position to which the aryl ethynyl group is bonded. It is preferable that they are respectively bonded to adjacent meso positions and opposite meso positions.

According to this configuration, a porphyrin complex capable of effectively improving battery characteristics can be synthesized by a relatively simple synthesis route.

In one embodiment, the electron donating group is preferably a diarylamino group (the aryl ring may have a substituent).

According to this configuration, the charge mobility of the molecule can be effectively enhanced by using a diarylamino group which is stable and has a high electron donating property. Therefore, the electron injection efficiency with respect to the electrode material can be effectively improved, and the battery characteristics can be effectively improved.

The porphyrin complex of the present invention is specifically represented by the following general formula as a preferred embodiment thereof.

[In the formula, A represents an arylene group which may have a substituent, X represents a carboxyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, or a phosphonic acid group, and k is an integer of 5 or less. Er1 and Er2 are the same or different and represent an electron-donating group capable of forming a π-conjugated system with a porphyrin ring, Ar1 represents an aryl group which may have a substituent, R1 to R8 Are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a halogen atom, and Ar1 and at least one of R6 and R7 are A condensed ring may be formed between them, and M represents a metal atom. ]

The characteristic configuration of the dye-sensitized solar cell according to the present invention includes a first electrode having a porous layer formed by adsorbing the porphyrin complex described above as a sensitizing dye on metal oxide particles, and the porous layer sandwiched between the first electrode and the porous layer. It is in the point provided with the 2nd electrode arrange | positioned facing said 1st electrode, and the electrolyte solution enclosed between said 1st electrode and said 2nd electrode.

According to this characteristic configuration, a dye-sensitized solar cell excellent in characteristics such as energy conversion efficiency, short-circuit current density, and open-circuit voltage can be realized.

Schematic diagram showing schematic configuration of dye-sensitized solar cell The figure which shows the synthetic | combination procedure of the porphyrin complex (ZnPBAT) of Example 1. Optical absorption spectrum of each porphyrin complex Energy diagram of each porphyrin complex Graph showing the initial energy conversion efficiency of dye-sensitized solar cells containing each porphyrin complex The graph which shows the effect by CDCA addition in the dye-sensitized solar cell containing each porphyrin complex Graph showing the aging effect in dye-sensitized solar cells containing each porphyrin complex Current-voltage curve of dye-sensitized solar cell containing each porphyrin complex Table showing evaluation results of battery performance of dye-sensitized solar cells containing each porphyrin complex Action spectrum of dye-sensitized solar cells containing each porphyrin complex FIG. 5 shows a synthesis procedure of the porphyrin complex (ZnPBAT-o-C8) of Example 2. The figure which shows the synthetic | combination procedure of the porphyrin complex (ZnPBAT-fused) of Example 3.

Embodiments of a dye-sensitized solar cell according to the present invention and a porphyrin complex used therein will be described with reference to the drawings. First, the overall configuration of the dye-sensitized solar cell 1 according to this embodiment will be described. As shown in FIG. 1, the dye-sensitized solar cell 1 includes a photoelectrode 10 as a first electrode, a counter electrode 20 as a second electrode disposed to face the photoelectrode 10, and a photoelectrode 10 and a counter electrode. 20 and an electrolytic solution 30 sealed between them.

The photoelectrode 10 has a conductive substrate 12 and a porous layer 14 formed on the surface of the conductive substrate 12. The conductive substrate 12 is obtained by forming a transparent conductive layer on a transparent substrate. As the transparent substrate for the photoelectrode 10, for example, a glass substrate such as a quartz substrate and a plastic substrate such as a polyethylene terephthalate substrate or a polycarbonate substrate can be used. The conductive layer can be composed of a transparent conductive film such as tin oxide (SnO2), fluorine-doped tin oxide (FTO), or indium tin oxide (ITO).

A porous layer 14 is laminated on the conductive layer of the conductive substrate 12. The porous layer 14 includes porous metal oxide particles 15 and sensitizing dyes 16 adsorbed on the surface of the metal oxide particles 15. Examples of the metal oxide constituting the metal oxide particles 15 include oxides of Ti, Sn, Zn, Fe, W, Zr, Hf, Sr, In, Ce, Y, La, V, Nb, or Ta. Is done. Among these, TiO2, SnO2, ZnO, ZrO2, Nb2O5 and Ta2O5 are preferable, and TiO2 can be particularly preferably used. The metal oxide particles 15 can be nano-sized to sub-micron sized particles. The sensitizing dye 16 has a function of absorbing and exciting light energy and injecting electrons into the metal oxide particles 15. The dye-sensitized solar cell according to the present invention is characterized in that a porphyrin complex having a specific molecular structure is used as such a sensitizing dye 16. Details of the porphyrin complex will be described later.

The counter electrode 20 has a conductive substrate 22 having a conductive layer formed on the substrate. The conductive substrate 22 has a conductive layer formed on a substrate. As the substrate for the counter electrode 20, for example, a glass substrate such as a quartz substrate, a plastic substrate such as a polyethylene terephthalate substrate or a polycarbonate substrate, and a metal substrate such as an aluminum substrate or a stainless steel substrate can be used. Similar to the photoelectrode 10, the conductive layer can be composed of a transparent conductive film such as tin oxide (SnO2), fluorine-doped tin oxide (FTO), or indium tin oxide (ITO). The counter electrode 20 may have a catalyst layer made of, for example, platinum or carbon.

The photoelectrode 10 and the counter electrode 20 are arranged to face each other with the porous layer 14 in between. In addition, they are arranged so that the porous layer 14 laminated on the conductive layer on the surface of the photoelectrode 10 and the conductive layer on the surface of the counter electrode 20 face each other with a gap. For this reason, a spacer (not shown) is provided between the photoelectrode 10 and the counter electrode 20. The spacer can be configured using a plastic material such as a polyolefin resin such as polyethylene or polypropylene. The spacer is formed, for example, in the shape of a rectangular frame and is provided at the peripheral edge of the photoelectrode 10 and the counter electrode 20, and defines a space between the two electrodes and forms a sealed closed space between the two electrodes.

An electrolytic solution 30 is sealed in a closed space between the photoelectrode 10, the counter electrode 20, and the spacer. The electrolytic solution 30 has a function of transporting electrons from the counter electrode 20 to the photoelectrode 10. The electrolytic solution 30 is not particularly limited as long as it contains ions capable of donating electrons to the sensitizing dye 16 that has performed electron injection into the metal oxide particles 15 in the porous layer 14. Examples of the electrolyte 30 include an iodine-based electrolyte containing I− / I3−, a bromine-based electrolyte including Br− / Br3−, a cobalt-based electrolyte including Co2 + / Co3 +, and a quinone forming a redox pair. / Quinone type electrolyte containing hydroquinone can be used. These can be used in a state in which the electrolyte is dissolved in a nonaqueous solvent (such as single or mixed solvent) such as acetonitrile, propylene carbonate, and ethylene carbonate.

When light such as sunlight or room light is incident on the photoelectrode 10, the incident light is hardly absorbed and passes through the conductive substrate 12, and most of the light reaches the porous layer 14. When the incident light reaching the porous layer 14 is irradiated to the sensitizing dye 16, the sensitizing dye 16 absorbs light energy and is excited. When the energy level of the sensitizing dye 16 becomes higher than the conduction band of the metal oxide constituting the metal oxide particle 15 by this excitation by a predetermined level or more, electrons are injected from the sensitizing dye 16 into the metal oxide particle 15. Is done. The injected electrons are collected by the photoelectrode 10.

On the other hand, ions in the electrolytic solution 30 surrounding the periphery of the sensitizing dye 16 that has injected electrons into the metal oxide particles 15 donate electrons. In this case, the oxidized ions are reduced by receiving electrons from the counter electrode 20. In this way, ions in the electrolytic solution 30 repeat a redox reaction between the sensitizing dye 16 and the counter electrode 20, thereby generating a potential gradient between the photoelectrode 10 and the counter electrode 20. By connecting 40, power can be supplied to the external load 40.

Next, a porphyrin complex having a specific molecular structure (hereinafter referred to as “the present porphyrin complex”) used as the sensitizing dye 16 in the present invention will be described. This porphyrin complex is a complex composed of a metal atom and a porphyrin derivative having a specific molecular structure coordinated to the metal atom. Porphyrin is a macrocyclic compound in which four pyrrole rings and four methine groups are alternately bonded (each pyrrole ring is bonded at the α-position). The porphyrin derivative represents a derivative of this porphyrin.

The metal atom (central metal atom) constituting the porphyrin complex is not particularly limited as long as it can coordinate to the porphyrin ring. However, considering the influence on the durability performance of the dye-sensitized solar cell 1, it is preferable to use a metal having excellent stability when coordinated to the porphyrin ring. In view of sustainability and cost, it is preferable to use an inexpensive metal with few resource restrictions. Examples of metal atoms that satisfy these requirements include Zn, Cu, Ti, Ni, Fe, and Mg. Among these, Zn, Cu, Fe, and Mg are preferable, and Zn is particularly preferable.

The porphyrin derivative constituting the porphyrin complex has one adsorbing group bonded to the porphyrin ring and at least two electron donating groups bonded to the porphyrin ring. The adsorbing group has an adsorptive functional group for adsorbing (chemical adsorption) on the surface of the metal oxide particle 15. The adsorbing group is designed so as to have an electron withdrawing property as a whole. As such an adsorbing group, an arylethynyl group (hereinafter referred to as “adsorbing arylethynyl group”) substituted with at least one adsorptive and electron-withdrawing functional group is used in the present invention. The aryl ring may further have a substituent.

Examples of the adsorptive and electron-withdrawing functional group include a carboxyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, and a phosphonic acid group. When a phosphonic acid group is used, one hydroxyl group may be substituted with an alkyl group or an aryl group (the aryl ring may have a substituent). In the present specification, the “phosphonic acid group” is a concept including such an alkyl group-substituted or aryl group-substituted phosphonic acid group. Among the above, a carboxyl group is preferable. Further, the number of adsorptive and electron-withdrawing functional groups is preferably one or two. That is, a monocarboxyaryl ethynyl group or a dicarboxyaryl ethynyl group is most preferable as the adsorptive group. The adsorptive arylethynyl group as the adsorptive group is bonded to the meso position or β position of the porphyrin ring in a state of forming a π-conjugated system with the porphyrin ring. A π-conjugated system is a state in which a plurality of carbon atoms are bonded by alternately repeating single bonds and multiple bonds, and π electrons (electrons on p orbitals) are conjugated to each other and delocalized throughout the molecule. Represents the system that has become.

A plurality of electron donating groups are also bonded to the meso position or β position of the porphyrin ring in a state of forming a π-conjugated system with the porphyrin ring. In the present invention, a plurality of electron donating groups are bonded to the porphyrin ring in an asymmetric positional relationship with respect to the adsorptive arylethynyl group. In other words, the plurality of electron donating groups are bonded to the porphyrin ring so that the molecular structure of the porphyrin complex is asymmetric. That is, a plurality of electron donating groups are respectively bonded to positions of porphyrin rings that are asymmetric with respect to the molecular axis including the adsorbing arylethynyl group in the porphyrin complex.

In one embodiment, the porphyrin complex has a structure in which one adsorbing arylethynyl group and two electron donating groups are asymmetrically bonded to any three of the four meso positions of the porphyrin ring. Have. That is, the adsorptive arylethynyl group is bonded to one of the four meso positions of the porphyrin ring, and the two electron donating groups are adjacent to the meso position to which the adsorptive arylethynyl group is bonded. It has a structure bonded to the position and the opposite meso position. This porphyrin complex can be represented by the following formula (1).

In the formula (1), A represents an arylene group which may have a substituent. X represents an adsorptive functional group, and specifically represents a carboxyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, or a phosphonic acid group. k represents an integer of 5 or less. Er1 and Er2 are the same or different and represent an electron donating group capable of forming a π-conjugated system with a porphyrin ring. Ar1 represents an aryl group which may have a substituent. R1 to R8 are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a halogen atom. Ar1 and at least one of R6 and R7 may form a condensed ring between them. M represents a metal atom.

Examples of Er1 and Er2 include a diarylamino group (the aryl ring may have a substituent) and a dialkylaminoarylethynyl group (the aryl ring may further have a substituent). When Er1 and Er2 are diarylamino groups, two aryl groups may form a condensed ring between them. Er1 and Er2 may be the same or different from each other, but preferably Er1 and Er2 are each a diarylamino group (the aryl ring may have a substituent).

This porphyrin complex can be specifically represented by the following formula (2) or formula (3) as one embodiment.

In the formulas (2) and (3), A, X, k, Ar1, R1 to R8, and M have the same definitions as in the formula (1). Ar2 to Ar5 are the same or different and each represents an aryl group which may have a substituent. R11 to R14 are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent.

In the formulas (1) to (3), examples of the arylene group represented by A include a phenylene group and a naphthylene group. Examples of the aryl group represented by Ar1 to Ar5 and the aryl groups represented by R1 to R8 and R11 to R14 include a phenyl group, a naphthyl group, and an anthryl group. Examples of the alkyl group represented by R1 to R8 and R11 to R14 include a linear alkyl group, a branched alkyl group, or a cyclic alkyl group having 1 to 20 carbon atoms. Specifically, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, hexyl group, cyclohexyl group, octyl group, decyl group. Groups and the like. Examples of the halogen atom represented by R1 to R8 and R11 to R14 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In the formulas (1) to (3), the arylene group represented by A may have a substituent, the aryl group represented by Ar1 to Ar5 may have a substituent, R1 to R8, Examples of the substituent that the alkyl group or aryl group represented by R11 to R14 may have include a lower alkyl group, a halogen atom, a hydroxyl group, a nitro group, an amino group, a mono-lower alkylamino group, and a di-lower alkylamino. Group, lower alkylcarbonyl group, lower alkoxycarbonyl group, alkoxy group, formyl group, cyano group, carboxy group, carbonyl group, carbamoyl group, lower alkylcarbamoyl group, lower alkylsulfonyl group, arylsulfonyl group, lower alkoxysulfonyl group, sulfamoyl Group, lower alkylsulfamoyl group, sulfanyl group, sulfino group, Group, a di-lower alkyl phosphoryl groups, diarylphosphoryl group, a di-lower alkoxy phosphoryl group, diamino phosphoryl group and the like. Note that lower means that the number of carbon atoms is 1-6. The number of substituents is usually 1 to 3, and in the case of 2 or more, the 2 or more substituents may be the same or different.

Preferable examples of the arylene group represented by A include a phenylene group. Preferable examples of the adsorptive functional group represented by X include a carboxyl group. Preferable examples of the aryl group represented by Ar1 include a phenyl group, a naphthyl group, and an anthryl group. Preferable examples of the aryl group represented by Ar2 to Ar5 include a phenyl group. Preferable examples of R1 to R8 include a hydrogen atom or a halogen atom. Preferable examples of R11 to R14 include alkyl groups such as methyl group and ethyl group, or alkoxy groups.

Preferred examples of the phenylene group as a representative example of A include an unsubstituted phenylene group in addition to the ethynyl group and the carboxyl group. Preferable examples of the substituent that the phenyl group, naphthyl group, or anthryl group as a representative example of Ar1 may have include an alkyl group such as a methyl group and a t-butyl group, and an alkoxy group such as an octyloxy group. Can be mentioned. Preferable examples of the substituent that the phenyl group as a typical example of Ar2 to Ar5 may have include an alkyl group such as a methyl group or a hexyl group.

In the formulas (1) to (3), Ar1 and R6 may cooperate with each other to form a condensed ring between them. Ar1 and R7 may cooperate with each other to form a condensed ring between them. Ar1 and both R6 and R7 may cooperate with each other to form a condensed ring between them. When Er1 and Er2 are diarylamino groups, in formula (2), Ar2 and Ar3 and / or Ar4 and Ar5 cooperate with each other to form a condensed ring between them. Also good.

In formulas (1) to (3), preferred examples of “k” representing the number of adsorptive functional groups include 1 or 2. In the case of one (k = 1), the one adsorptive functional group is preferably bonded to the p-position or m-position with respect to the bonding position with the ethynyl group in the aryl ring, Is most preferred. In the case of two (k = 2), the two adsorptive functional groups are bonded to two m-positions or p-position and m-position, respectively, with respect to the bonding position with the ethynyl group in the aryl ring. It is preferable. In the case of having two adsorptive functional groups, the adsorptive power can be increased as compared with the case of only one adsorptive functional group, and the durability of the dye-sensitized solar cell can be improved.

The porphyrin complex can be represented by any of the following formulas (4) to (12) as a preferred embodiment.

In another aspect, the porphyrin complex has an adsorbing arylethynyl group and at least two electron donating groups that are not limited to the four meso positions of the porphyrin ring. It has a structure bonded to any three or more of the meso-position and β-position. For example, it has a structure in which one adsorptive arylethynyl group is bonded to the β-position of the porphyrin ring and two to four electron-donating groups are bonded to any one of four meso positions of the porphyrin ring. . Two or three electron donating groups may be bonded in any combination to the four meso positions, but from the viewpoint of the stability of the molecular structure, they are bonded so as to reduce steric hindrance. It is preferable.

In the present porphyrin complex, as a preferred example, an adsorbing arylethynyl group is bonded to one of the β positions of the porphyrin ring, and two electron donating groups are bonded to a pyrrole ring bonded to the adsorbing arylethynyl group. It has a structure bonded to two meso positions adjacent to both sides of the opposing pyrrole ring. Alternatively, the adsorptive aryl ethynyl group is bonded to one of the β positions of the porphyrin ring, and three electron donating groups are adjacent to both sides of the pyrrole ring facing the pyrrole ring to which the adsorptive aryl ethynyl group is bonded. The two meso positions and the meso position of the remaining two meso positions located further away from the adsorptive arylethynyl group. Alternatively, the adsorptive arylethynyl group is bonded to one of the β positions of the porphyrin ring, and four electron donating groups are bonded to the four meso positions. The porphyrin complex can be represented by the following formulas (13) to (15) as one embodiment.

In the formulas (13) to (15), A, X, k, Er1, Er2, Ar1, R1 to R5, R7, R8, and M have the same definitions as in the formula (1). Ar6 represents an aryl group which may have a substituent. Er3 and Er4 are the same or different and represent an electron donating group capable of forming a π-conjugated system with a porphyrin ring. In Formula (13), Ar1 and R7 may form a condensed ring between them.

This porphyrin complex has, as another embodiment, a structure in which one adsorbing arylethynyl group and at least two diarylamino groups are bound to a porphyrin ring without being limited to an asymmetric structure. For example, the porphyrin derivative constituting the porphyrin complex has one adsorptive aryl ethynyl group bonded to the porphyrin ring (the aryl ring may further have a substituent) and at least two bonded to the porphyrin ring. And a diarylamino group (the aryl ring may have a substituent).

In this case, as one embodiment, the adsorptive aryl ethynyl group is bonded to one of the four meso positions of the porphyrin ring, and at least two diarylamino groups are bonded to the meso-bonded aryl ethynyl group. It is preferable that the bond is bonded to the meso positions adjacent to both sides of the position.

As a more specific embodiment, it is preferable that two diarylamino groups are bonded to only meso positions adjacent to both sides of the meso position to which the adsorptive aryl ethynyl group is bonded. Alternatively, it is preferable that the three diarylamino groups are bonded to the meso position adjacent to the both sides of the meso position to which the adsorptive aryl ethynyl group is bonded, respectively. In other words, it is preferable that the three diarylamino groups are respectively bonded to the remaining three meso positions. This porphyrin complex can be represented by the following formula (16) or formula (17).

In the formulas (16) and (17), A, X, k, Ar1 to Ar5, R1 to R8, and M have the same definitions as in the formula (2). Ar6 and Ar7 are the same or different and each represents an aryl group which may have a substituent.

This porphyrin complex can be synthesized according to the following procedure. That is, the method for producing the porphyrin complex includes the following steps. In the description of this production method, “porphyrin derivative” means a state in which the porphyrin derivative forms a complex with a metal atom and a free state in which no complex is formed, depending on the situation at each stage. The concept includes both.

First stage: A porphyrin derivative in which one of four meso positions is substituted with an aryl group which may have a substituent is prepared.
Second stage; cis of a porphyrin derivative substituted with an aryl group which may have a substituent and a halogen atom by halogenating one of the other meso positions of the porphyrin derivative obtained in the first stage. A mixture of body and trans form is obtained.
Third stage: The cis isomer is separated from the mixture of the cis isomer and the trans isomer obtained in the second stage.
Fourth stage: The halogen atom in the cis isomer obtained in the third stage is substituted with an ethynyl group whose terminal side is protected with a protecting group.
Fifth stage: The remaining two meso positions of the porphyrin derivative obtained in the fourth stage are halogenated.
Sixth stage: Two halogen atoms in the porphyrin derivative obtained in the fifth stage are each substituted with an electron donating group capable of forming a π-conjugated system together with the porphyrin ring.
Seventh step: After deprotecting the ethynyl group in the porphyrin derivative obtained in the sixth step, an aryl group substituted with an adsorptive and electron-withdrawing functional group on the terminal side of the ethynyl group (the aryl ring is Furthermore, an optionally substituted group is bonded.

Hereinafter, the present porphyrin complex and the dye-sensitized solar cell using the same will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples. The discussion in the following description includes a part of estimation, and the scope of the present invention is not limited by the correctness.

[Example 1]
The procedure for 5- (4-carboxyphenylethynyl) -10,15-bis (4-methylphenyl) amino-20- (2,4,6-trimethylphenyl) porphyrinatozinc (II) (ZnPBAT) is shown in FIG. Was synthesized according to

5- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 21 (199 mg, 0.405 mmol) was dissolved in dichloromethane (100 mL), and this solution was stirred at room temperature while stirring trifluoroacetic acid (TFA). ) (1.0 mL) was added. After stirring for 12 hours, the reaction mixture was neutralized with a saturated aqueous solution of sodium bicarbonate (100 mL) and then extracted with dichloromethane. The obtained extract was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure to obtain a reddish purple solid 5- (2,4,6-trimethylphenyl) porphyrin 22. The yield was 96%. The production of porphyrin derivative 22 was confirmed by nuclear magnetic resonance spectroscopy and high resolution mass spectrometry.

5- (2,4,6-trimethylphenyl) porphyrin 22 (232 mg, 0.541 mmol) and pyridine (2 mL) were dissolved in chloroform (120 mL), and this solution was stirred at 0 ° C. with N— Bromosuccinimide (NBS) (91.5 mg, 0.514 mmol) was added. After stirring for 30 minutes, acetone (5 mL) was added to terminate the reaction, and the solvent was removed under reduced pressure. The residue was purified with a silica gel column (eluent: dichloromethane / hexane = 1/2) to obtain a crude intermediate (mixture of cis-type intermediate and trans-type intermediate). The obtained mixture was subjected to column chromatography using silica gel (eluent: dichloromethane / hexane = 1/2) to separate a cis-type intermediate from the mixture. This cis-type intermediate was dissolved in dichloromethane (50 mL), a saturated methanol solution of zinc acetate (5 mL) was added to the solution, and the mixture was stirred for 3 hours. The reaction was terminated by the addition of a saturated aqueous solution of sodium bicarbonate (30 mL), and then the mixture was extracted with dichloromethane. The obtained extract was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure to obtain 5-bromo-10- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 23 as a reddish purple solid. The yield was 27%. The production of porphyrin complex 23 was confirmed by nuclear magnetic resonance spectroscopy, high resolution mass spectrometry, and Fourier transform infrared spectroscopy.

5-bromo-10- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 23 (78.5 mg, 0.138 mmol), triisopropylsilylacetylene (0.070 mL, 0.30 mmol), dichlorobis (triphenylphosphine) palladium ( 20.1 mg, 0.0286 mmol, copper iodide (8.5 mg, 0.045 mmol), tetrahydrofuran (THF) (6 mL), and triethylamine (1 mL) were gently refluxed under argon for 4 hours. After removing the solvent under reduced pressure, the residue was purified with a silica gel column (eluent: dichloromethane / hexane = 1/4). As a result, a red-purple solid 5-triisopropylsilylethynyl-10- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 24 was obtained. The yield was 87%. The production of porphyrin complex 24 was confirmed by nuclear magnetic resonance spectroscopy, time-of-flight mass spectrometry, and Fourier transform infrared spectroscopy.

Dissolve 5-triisopropylsilylethynyl-10- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 24 (80.9 mg, 0.120 mmol) in a mixed solvent of dichloromethane (45 ジクロロメタン mL) and pyridine (1.8 mL) N-bromosuccinimide (47.1 mg, 0.265 mmol) was added to the solution. After stirring for 30 minutes, acetone (4.5 mL) was added to terminate the reaction, and the solvent was removed under reduced pressure. The residue was purified with a silica gel column (eluent: dichloromethane / hexane = 1/4) and reddish purple solid 5,10-dibromo-15-triisopropylsilylethynyl-20- (2,4,6-trimethylphenyl) Porphyrinato zinc (II) 25 was obtained. The yield was 50%. The production of porphyrin complex 25 was confirmed by time-of-flight mass spectrometry.

Bis (4-methylphenyl) amine (95.2 mg, 0.483 mmol) was dissolved in toluene (5 mL), and 1.6M n-butyllithium in hexane (0.29 mL) was added to this solution under argon at -78 ° C. , 0.47 mmol). After stirring for 1 hour, the reaction temperature was raised to room temperature. To this reaction solution, 5,10-dibromo-15-triisopropylsilylethynyl-20- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 25 (49.6 mg, 0.0598 mmol), toluene (10 mL), A mixed solution of bis (diphenylphosphino) diphenyl ether (DPEphos) (24.1 mg, 0.0447 mmol) and palladium acetate (6.7 mg, 0.030 mmol) was added. The resulting mixed solution was gently refluxed under argon for 4 hours. After removing the solvent under reduced pressure, the residue was purified with a silica gel column (eluent: dichloromethane / hexane = 1/4). As a result, green solid 5,10-bis (bis (4-methylphenyl) amino) -15-triisopropylsilylethynyl-20- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 26 was obtained. It was. The yield was 61%. In addition, the production | generation of the porphyrin complex 26 was confirmed by the time-of-flight mass spectrometry.

5,10-bis (bis (4-methylphenyl) amino) -15-triisopropylsilylethynyl-20- (2,4,6-trimethylphenyl) porphyrinatozinc (II) 26 was dissolved in tetrahydrofuran (5 mL). To this solution was added 1.0 M tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran (0.19 mL). The resulting mixed solution was stirred at room temperature for 30 minutes under argon. Thereafter, water was added to terminate the reaction, and the resulting mixed solution was extracted with dichloromethane. The obtained extract (organic phase) was dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue was dissolved in 4-iodobenzoic acid (44.0 mg, 0.177 mmol) in a mixed solvent of tetrahydrofuran (10 mL) and triethylamine (1.7 mL). After degassing for 10 minutes, tris (dibenzylideneacetone) dipalladium (Pd2 (dba) 3) (10.0 mg, 0.0109 mmol) and triphenylarsine (22.0 mg, 0.0718 mmol) were further added. The resulting mixed solution was refluxed for 4 hours under argon. After removing the solvent under reduced pressure, the residue was purified with a silica gel column (eluent: dichloromethane / methanol = 20/1). After further purification by recrystallization, green solid 5- (carboxyphenylethynyl) -10,15-bis (bis (4-methylphenyl) amino) -20- (2,4,6-trimethylphenyl) porphyrinato Zinc (II) (ZnPBAT) was obtained. The yield was 79%. The formation of ZnPBAT was confirmed by nuclear magnetic resonance spectroscopy, high resolution mass spectrometry, and Fourier transform infrared spectroscopy.

[Comparative example]
According to the method described in Hsieh, C.-P. et al. J. Mater. Chem. 20, 1127-1134 (2010), 5- (carboxyphenylethynyl) -10,20-bis (3,5-di- (T-Butyl) phenyl) -15-bis (4-hexylphenyl) aminoporphyrinato zinc (II) (YD2; see FIG. 4) was obtained. In addition, according to the method described in US Patent Application Publication No. 2013/0042916, 5- (carboxyphenyl) -10,15-bis (bis (4-methylphenyl) amino) -20- (2,4,4) 6-Trimethylphenyl) porphyrinato zinc (II) (ZnPBA; see FIG. 4) was obtained.

[Evaluation test]
The present porphyrin complex (ZnPBAT) and the porphyrin complex of the comparative example (YD2, ZnPBA) were evaluated for their abilities as sensitizing dyes. Moreover, the dye-sensitized solar cell which used these as a sensitizing dye was produced, and the battery characteristic was evaluated.

<Light absorption characteristics>
Each of ZnPBAT, YD2, and ZnPBA was evaluated for light absorption characteristics in an ethanol solution. FIG. 3 shows the light absorption spectrum of each porphyrin complex in the ultraviolet-visible near-infrared region. In FIG. 3, the vertical axis represents the molar extinction coefficient, and the horizontal axis represents the wavelength. From this figure, it can be understood that the light absorption spectrum of ZnPBAT having two diarylamino groups is broader than the light absorption spectrum of YD2 having only one diarylamino group. Moreover, it can be understood that the light absorption spectrum of ZnPBAT has a longer wavelength than the light absorption spectra of YD2 and ZnPBA. In particular, when comparing the peak wavelengths in the absorption band on the long wavelength side corresponding to the Q band of porphyrin, the peak wavelength of ZnPBAT is 15 nm or more longer than the peak wavelength of YD2, and 30 nm or more compared to the peak wavelength of ZnPBA. It was long. Further, when comparing the integrated values in the absorption band on the long wavelength side, ZnPBAT having an ethynyl group (triple bond) bonded to a porphyrin ring has a higher absorption band than ZnPBA having no such functional group. It can be understood that it is greatly enhanced. These results indicate that ZnPBAT further improved the light collection characteristics in the visible region and the near-infrared region as compared with YD2 and ZnPBA.

<Energy diagram>
The energy level of each molecular orbital of ZnPBAT, YD2, ZnPBA was calculated. FIG. 4 shows an energy diagram of each porphyrin complex. In FIG. 4, the vertical axis represents the oxidation-reduction potential using a standard hydrogen electrode as a reference electrode, the upper straight line in each porphyrin complex represents LUMO, and the lower straight line represents HOMO. From this figure, it can be understood that ZnPBAT has an increased HOMO level compared to YD2 having a comparable LUMO level. It can also be seen that ZnPBAT has a lower LUMO level than ZnPBA having a comparable HOMO level. Accordingly, it can be understood that ZnPBAT has a reduced HOMO-LUMO gap compared to YD2 and ZnPBA. These results suggest that ZnPBAT enables efficient charge transfer between metal oxide particles and ions in the electrolyte as compared with YD2 and ZnPBA.

<Preparation of dye-sensitized solar cell>
A porous layer made of TiO2 particles was laminated on the surface of FTO glass to prepare a titanium oxide electrode. The porous layer is about 8 μm layer composed of TiO 2 particles having an average particle diameter of 20 nm, about 4 μm layer composed of TiO 2 particles having an average particle diameter of 30 nm, and about TiO 2 particles having an average particle diameter of 400 nm. A three-layer structure consisting of 4 μm layers was formed. The prepared titanium oxide electrode was immersed in a 0.2 mM ethanol solution of each porphyrin complex (ZnPBAT, YD2, ZnPBA) to obtain a dye-modified titanium oxide electrode (photoelectrode) in which each porphyrin complex was adsorbed on the surface of TiO2 particles. . A counter electrode was prepared by forming a platinum thin film on the surface of the FTO glass. The dye-modified titanium oxide electrode and the counter electrode were opposed to each other through a spacer, and an electrolyte solution was sealed to prepare a dye-sensitized solar cell. The electrolyte included 1.0M 1,3-dimethylimidazolium iodide, 0.03M iodine, 0.05M lithium iodide, 0.1M guanidine thiocyanate, and 0.5M 4-t. A solution obtained by dissolving an electrolyte composed of butylpyridine in a mixed solvent of acetonitrile and valeronitrile (85:15 by volume) was used.

<Battery characteristics>
Evaluation of battery characteristics of each of dye-sensitized solar cells containing any of ZnPBAT, YD2, and ZnPBA as sensitizing dyes (hereinafter referred to as “ZnPBAT battery”, “YD2 battery”, and “ZnPBA battery”, respectively) It was. The battery characteristics were evaluated mainly based on energy conversion efficiency (η), short circuit current density, open circuit voltage, and fill factor.

First, changes in the initial energy conversion efficiency of each battery were verified. FIG. 5 shows the result. In FIG. 5, the vertical axis represents energy conversion efficiency, and the horizontal axis represents immersion time. From this figure, it can be understood that, in the YD2 battery and the ZnPBA battery, the energy conversion efficiency with respect to the immersion time changes so as to match the adsorption behavior of the sensitizing dye on the TiO2 particle surface and reaches the maximum value in about 3 hours. . On the other hand, in the ZnPBAT battery, it can be understood that the energy conversion efficiency rapidly increases during the immersion time of about 1 hour, shows a maximum value, and then decreases slightly and converges to a predetermined value. Thus, it was found that the ZnPBAT battery has completely different changes in the energy conversion efficiency in the initial stage compared to the YD2 battery and the ZnPBA battery. Although this is not clear in detail, it is expected to be a phenomenon based on the difference in the association state of the porphyrin complex on the TiO2 particles.

In order to suppress aggregation of the porphyrin complex on the TiO2 particles, chenodeoxycholic acid (CDCA) was added as a co-adsorbent to the ethanol solution of each porphyrin complex. FIG. 6 is a graph showing the relationship between the amount of chenodeoxycholic acid added and the energy conversion efficiency. The vertical axis represents energy conversion efficiency, and the horizontal axis represents the amount added. From this figure, it was found that the amount of chenodeoxycholic acid added to each porphyrin complex was optimally about 10 equivalents for ZnPBAT, about 2 equivalents for YD2, and about 5 equivalents for ZnPBA. These results are considered to reflect the difference in the state of association of the porphyrin complex on the TiO2 particles.

The dye-sensitized solar cell added with the optimum amount of chenodeoxycholic acid according to each porphyrin complex was left in the dark to verify the effect of aging. FIG. 7 shows the result. In FIG. 7, the vertical axis represents energy conversion efficiency, and the horizontal axis represents aging time. As shown in this figure, the energy conversion efficiency of the ZnPBAT cell reached a maximum value of 10.1% after aging for about 36 hours. This is a value that greatly exceeds the maximum value of 8.3% in the ZnPBA battery (approximately 20% increase), and is also significantly higher than the maximum value of 9.1% in the YD2 battery (approximately 10% increase). Regarding YD2 batteries, 11% energy conversion efficiency was reported in Bessho, T. et al. Angew. Chem. Int. Ed. 49, 6646-6649 (2010). The test failed to confirm it. This is probably because the optimization was not always sufficient. Considering this point, if the specifications of the dye-sensitized solar cell are further optimized by future research, it is expected that an energy conversion efficiency exceeding 11% will be achieved in the ZnPBAT cell.

The current-voltage characteristics of each battery were verified under the optimization conditions in this evaluation test. FIG. 8 shows the result. In FIG. 8, the vertical axis represents current, and the horizontal axis represents voltage. From this figure, the short circuit current density (JSC), open circuit voltage (VOC), and fill factor (FF) of each battery were calculated. The results are summarized in FIG. 9 together with the maximum energy conversion efficiency. The fill factor was almost the same in each battery. The open circuit voltage was slightly higher for the YD2 battery, but not so significant. The short-circuit current density of the ZnPBAT battery was superior to that of the YD2 battery or ZnPBA battery. The short-circuit current density of the ZnPBAT battery was significantly higher than that of the ZnPBA battery (approximately 20% increase), and significantly higher than that of the YD2 battery (approximately 10% increase). From these results, it was confirmed that the ZnPBAT battery was very excellent when focusing on the overall battery characteristics.

The spectral sensitivity characteristics of each battery were evaluated. FIG. 10 shows the action spectrum of each battery. In FIG. 10, the vertical axis represents external quantum efficiency (IPCE), and the horizontal axis represents wavelength. From this figure, it can be understood that the external quantum efficiency of the ZnPBAT battery is improved in comparison with the YD2 battery and the ZnPBA battery in the wavelength region of 650 to 800 nm. Further, considering FIG. 10 and FIG. 3 together, the improvement of the external quantum efficiency in the wavelength region of 650 to 800 nm has a positive correlation with the improvement of the light condensing characteristic of the sensitizing dye ZnPBAT itself. I understand that. That is, in the ZnPBAT battery, it can be understood that the improvement of the light collection characteristic works effectively for the improvement of the battery characteristic.

Thus, the porphyrin complex has an enhanced push-pull type molecular structure, uses an adsorbing group including an arylethynyl group having a triple bond, and a plurality of electron donating groups with respect to the adsorbing group. It is characterized in that it is introduced so as to have lower symmetry. Thereby, the condensing characteristic in the visible region and the near-infrared region can be improved, and when it is used as a sensitizing dye in a dye-sensitized solar cell, the battery characteristic can also be improved effectively. .

[Example 2]
5- (4-Carboxyphenylethynyl) -10,15-bis (bis (4-methylphenyl) amino) -20- (2,6-bis (octyloxy) phenyl) porphyrinato zinc (II) (ZnPBAT-o- C8) was synthesized. In synthesizing ZnPBAT-o-C8, a porphyrin derivative in which one of four meso positions was substituted with a 2,6-dioctyloxyphenyl group was prepared according to the procedure shown in FIG. From this porphyrin derivative, ZnPBAT-o-C8 was synthesized according to a procedure similar to that in Example 1 thereafter. It was confirmed that ZnPBAT-o-C8 also has the same current collecting characteristics as ZnPBAT and can improve the battery characteristics like ZnPBAT. In addition, a result suggesting that ZnPBAT-o-C8 can suppress the reverse transfer of electrons to ions and the association between porphyrin complexes at the interface with the electrolytic solution as compared with ZnPBAT.

[Example 3]
5- (4-Carboxyphenylethynyl) -10,15-bis (bis (4-methylphenyl) amino) -2,20- (4,5- (1-octyloxynaphthalene)) porphyrinatozinc (II) (ZnPBAT -Fused) was synthesized. In synthesizing ZnPBAT-fused, a porphyrin derivative in which one of four meso positions was substituted with a 4-octyloxynaphthyl group was prepared according to the procedure shown in FIG. Using this porphyrin derivative, ZnPBAT-fused was synthesized according to a procedure similar to that in Example 1 thereafter. In addition, iron chloride and nitromethane were added to the dichloroethane solution of the porphyrin derivative after introducing two electron donating groups into the porphyrin ring, thereby condensing the 4-octyloxynaphthyl group and the porphyrin ring. Thereafter, a carboxyphenyl group was introduced at the end of the ethynyl group to obtain ZnPBAT-fused. It has been confirmed that ZnPBAT-fused has the same current collecting characteristics as ZnPBAT and can improve the battery characteristics in the same manner as ZnPBAT.

It should be understood that the embodiments disclosed herein and examples embodying the embodiments are illustrative in all respects, and the scope of the present invention is not limited thereby. Those skilled in the art will readily understand that appropriate modifications can be made without departing from the spirit of the present invention based on the above-described embodiments and examples. Accordingly, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

The present invention can be effectively used as a sensitizing dye for a dye-sensitized solar cell.

1 Dye-sensitized solar cell 10 Photoelectrode (first electrode)
14 Porous layer 15 Metal oxide particle 16 Sensitizing dye (porphyrin complex)
20 Counter electrode (second electrode)
30 electrolyte

Claims

A porphyrin complex comprising a metal atom and a porphyrin derivative coordinated to the metal atom,
The porphyrin derivative has one adsorbing group bonded to the porphyrin ring and at least two electron donating groups bonded to the porphyrin ring in a state of forming a π-conjugated system with the porphyrin ring,
The adsorptive group is an arylethynyl group substituted with an adsorptive and electron-withdrawing functional group (the aryl ring may further have a substituent),
A porphyrin complex in which at least two of the electron donating groups are bonded to the porphyrin ring in an asymmetric positional relationship with respect to the arylethynyl group.
The arylethynyl group is bonded to one of the four meso positions of the porphyrin ring;
2. The porphyrin complex according to claim 1, wherein the two electron donating groups are respectively bonded to an adjacent meso position and an opposite meso position with respect to the meso position to which the arylethynyl group is bonded.
The porphyrin complex according to claim 1 or 2, wherein the electron donating group is a diarylamino group (the aryl ring may have a substituent).
The porphyrin complex as described in any one of Claim 1 to 3 represented by the following general formula.

[Where:
A represents an arylene group which may have a substituent,
X represents a carboxyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, or a phosphonic acid group,
k represents an integer of 5 or less,
Er1 and Er2 are the same or different and represent an electron donating group capable of forming a π-conjugated system with a porphyrin ring,
Ar1 represents an aryl group which may have a substituent,
R1 to R8 are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or a halogen atom;
Ar1 and at least one of R6 and R7 may form a condensed ring between them,
M represents a metal atom. ]
A first electrode having a porous layer formed by adsorbing the porphyrin complex according to any one of claims 1 to 4 on a metal oxide particle as a sensitizing dye;
A second electrode disposed opposite to the first electrode across the porous layer;
An electrolyte solution sealed between the first electrode and the second electrode;
A dye-sensitized solar cell comprising: