JP6209424B2 - Metal complex, dye-sensitized solar cell, dye-sensitized solar cell module, method for producing metal complex - Google Patents

Description

  The present invention relates to a metal complex, a dye-sensitized solar cell, a dye-sensitized solar cell module, a method for producing a metal complex, and a ligand.

  In recent years, various metal complexes have been studied as sensitizing dyes used in dye-sensitized solar cells. For example, as a metal complex that is a sensitizing dye, a bipyridine ruthenium complex in which two bipyridine substituted ligands are coordinated to ruthenium has been proposed (see Patent Documents 1 to 3). Such a metal complex can be used as a dye for a dye-sensitized solar cell, and has been actively studied in recent years. Further, a metal complex dye in which a tridentate terpyridine ligand having three pyridine structures is coordinated to a transition metal as a photosensitizer has been proposed (see Patent Documents 3 and 4). For example, a tricarboxylic acid terpyridine compound (also referred to as a black dye) which is a tridentate ligand has a relatively high conversion efficiency, and various studies have been made on its improvement (see Non-Patent Documents 1 to 3). Further, for example, Non-Patent Documents 2 and 3 propose to introduce an electron-donating functional group to improve the performance of the solar cell.

Japanese National Patent Publication No. 5-508420 JP 7-500630 Japanese National Patent Publication No. 10-504521 JP 2002-512729 A

Journal of the American Chemical Society 2001, 123, 1613-1624 Adv. Funct. Mater. 2012, DOI: 10.1002 / adfm.201202504 Phys. Chem. Chem. Phys., 2012, 14, 14190-14195

However, the existing black dye (N749 dye) described above has a low extinction coefficient, for example, in the vicinity of a wavelength of 400 nm, and it has been desired to increase the extinction coefficient of this portion. In addition, when an electron donating functional group is introduced, the absorption wavelength band (absorption edge) may change. In addition, according to Non-Patent Document 3, it has been shown that when CF ₃ that is an electron withdrawing group is introduced, it does not function as a solar cell. Until now, an approach to introduce an electron withdrawing group via an aryl group has been shown. Was not done.

  The present invention has been made to solve such problems, and a main object of the present invention is to provide a complex dye capable of further increasing the extinction coefficient without largely changing the absorption wavelength band.

  In order to achieve the above-mentioned object, the present inventors have selected one of the carboxy groups bonded to the pyridine ring of the N749 dye having a tridentate terpyridine ligand bonded to each pyridine structure. When the structure having an electron-withdrawing group bonded through an aryl group is substituted, it has been found that the absorption coefficient in the vicinity of a wavelength of 400 nm can be increased without greatly changing the absorption wavelength band as compared with the N749 dye. The invention has been completed.

That is, the metal complex of the present invention is
It has a transition metal ion and three pyridine structures coordinated to the transition metal ion. At least one of the pyridine structures has an electron-withdrawing group bonded thereto via an aryl group, and the remaining pyridine structure has a carboxy structure. An anionic complex having a tridentate terpyridine ligand to which a group is bonded;
A counter cation attached to the anionic complex;
It is what has.

  The dye-sensitized solar cell of the present invention uses the above-described metal complex as a dye.

The dye-sensitized solar cell module of the present invention is
A plurality of the dye-sensitized solar cells described above are provided.

The method for producing the metal complex of the present invention comprises:
A method for producing a metal complex having a tridentate terpyridine ligand, wherein -X (X is a halogen group) is bonded to the 2- or 6-position of the pyridine structure in which the electron-withdrawing group is bonded via an aryl group. The group-bonded halide is cross-coupled with an organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 6-position or 6′-position of the 2,2′-bipyridine structure, or electrons are bonded via an aryl group. An electron-withdrawing group-bonded organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 2-position or 6-position of the pyridine structure to which the attractive group is bonded; and the 6-position or 6′-position of the 2,2′-bipyridine structure; It includes a ligand synthesis step of synthesizing the tridentate terpyridine ligand by cross-coupling with a halide to which —X (X is a halogen group) is bonded.

The ligand of the present invention is
A tridentate terpyridine ligand having three pyridine structures,
At least one of the pyridine structures is bonded with an electron-withdrawing group via an aryl group, and the remaining pyridine structure is bonded with a carboxy group.

  In the present invention, the extinction coefficient can be increased without greatly changing the absorption wavelength band (absorption edge). The reason why such an effect can be obtained is assumed as follows. That is, in the present invention, an electron withdrawing group is introduced into the terpyridine directly contributing to the ligand field of a metal such as ruthenium via an aryl group. This is presumably because the effect of increasing the extinction coefficient by maintaining the absorption wavelength band by the electron withdrawing group while maintaining the balance of the electron density of the metal complex having a tridentate terpyridine ligand is obtained.

FIG. 3 is a cross-sectional view showing an example of a schematic configuration of the dye-sensitized solar cell module 10. FIG. 3 is a cross-sectional view illustrating an example of a schematic configuration of a dye-sensitized solar cell 40. Explanatory drawing which shows the synthetic route of a ligand. Explanatory drawing which shows the synthetic route of a ligand. Explanatory drawing which shows the synthetic route of a ligand. ¹ H-NMR result of the ligand. MALDI-MS mass spectrometry result of the ligand. Explanatory drawing which shows the synthetic pathway of a complex pigment | dye. Explanatory drawing which shows the refinement | purification procedure of a complex pigment | dye. ¹ H-NMR result of the complex dye. MALDI-MS mass spectrometry result of complex dye. The absorption spectrum of the metal complex of Example 1 and Comparative Example 1. Calculation results of the highest occupied molecular orbital (HOMO) -lowest orbital (LUMO) energy gap of a complex dye by molecular orbital calculation. The external quantum efficiency (IPCE) spectrum of the dye-sensitized solar cell of Example 1 and Comparative Example 1. The measurement result of the solar cell characteristic of the dye-sensitized solar cell of Example 1 and Comparative Example 1.

  An embodiment of the dye-sensitized solar cell module of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating an example of a schematic configuration of a dye-sensitized solar cell module 10. As shown in FIG. 1, the dye-sensitized solar cell module 10 according to this embodiment has a configuration in which a plurality of dye-sensitized solar cells 40 (hereinafter also referred to as cells) are sequentially arranged on a transparent conductive substrate 14. It has become. These cells are connected in series. In this dye-sensitized solar cell module 10, a sealing material 32 is formed so as to fill between the cells, and a flat protective member is provided on the surface of the sealing material 32 on the side opposite to the transparent conductive substrate 14. 34 is formed. The dye-sensitized solar cell 40 according to this embodiment includes a transparent conductive substrate 14 having a transparent conductive film 12 formed on the surface of a transparent substrate 11 through which light is transmitted, and a dye formed on the transparent conductive film 12. A porous semiconductor layer 24 and a counter electrode 30 provided on the porous semiconductor layer 24 via an electrolyte layer 26 are provided. The photoelectrode 20 is disposed on the transparent conductive substrate 14 and the transparent conductive film 12 formed separately on the surface opposite to the light receiving surface 13 of the transparent substrate 11 and is provided with a porous semiconductor layer 24 that emits electrons upon receiving light. It has. This dye-sensitized solar cell 40 includes an electrolyte layer 26 formed by containing an electrolyte solution in a porous body, and has a configuration capable of generating power via the electrolyte solution.

The transparent conductive substrate 14 is composed of the transparent substrate 11 and the transparent conductive film 12, and has light transmittance and conductivity. Specific examples include fluorine-doped SnO ₂ coated glass, ITO coated glass, ZnO: Al coated glass, and antimony-doped tin oxide (SnO ₂ —Sb) coated glass. Also, a transparent electrode obtained by doping tin oxide or indium oxide with cations or anions having different valences, or a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, provided on a substrate such as a glass substrate. Can be used. Current collecting electrodes 16 and 17 are provided at both ends of the transparent conductive substrate 14 on the transparent conductive film 12 side. Electric power generated by the dye-sensitized solar cell 40 via the current collecting electrodes 16 and 17 is provided. Can be used.

  Examples of the transparent substrate 11 include transparent glass, a transparent plastic plate, a transparent plastic film, and an inorganic transparent crystal, and among these, transparent glass is preferable. The transparent substrate 11 may be a transparent glass substrate, a glass substrate whose surface is appropriately roughened to prevent reflection of light, or a transparent glass substrate such as a ground glass-like translucent glass substrate. The transparent conductive film 12 can be formed, for example, by depositing tin oxide on the transparent substrate 11. In particular, if a metal oxide such as tin oxide (FTO) doped with fluorine is used, a suitable transparent conductive film 12 can be formed. In the transparent conductive film 12, grooves 18 are formed at predetermined intervals, and a plurality of regions of the transparent conductive film 12 are separately formed at intervals corresponding to the width of the grooves 18.

The porous semiconductor layer 24 is formed of a metal complex that is a photosensitizer and a porous n-type semiconductor layer containing the metal complex. As the n-type semiconductor, a metal oxide semiconductor or a metal sulfide semiconductor is suitable. For example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium sulfide (CdS), sulfide It is preferable that it is at least 1 or more among zinc (ZnS), and among these, porous titanium oxide is more preferable. By thinning these semiconductor materials into a microcrystalline or polycrystalline state, a good porous n-type semiconductor layer can be formed. In particular, the porous titanium oxide layer is suitable as an n-type semiconductor layer included in the photoelectrode 20. Further, as titanium oxide, anatase TiO ₂ is preferable to rutile TiO ₂ because the energy level at the lower end of the conduction band is higher and the open-circuit voltage is higher.

The metal complex has an anionic complex and a counter cation attached to the anionic complex. This anionic complex has a transition metal ion and three pyridine structures coordinated to the metal ion, and at least one of the pyridine structures has an electron withdrawing group bonded thereto via an aryl group, and the rest The pyridine structure has a tridentate terpyridine ligand to which a carboxy group is bonded. In the carboxy group, protons may be ionized. Examples of the aryl group include a phenyl group, a naphthyl group, and an anthryl group. Examples of the electron withdrawing group include a halogen group, a halogenated alkyl group (such as CF ₃ ), a cyano group, a nitro group, an aldehyde group, a carboxy group, a tosyl group, a mesyl group, and an acyl group. Of these, a halogen group, a halogenated alkyl group, a cyano group and the like are preferable. This is because the electron withdrawing property is particularly high.

This metal complex may be represented, for example, by the basic formula (1). As shown in the basic formula (1), the anionic complex is composed of a tridentate terpyridine ligand and three monovalent anionic ligands (L ¹ , L ² and L ³ in the formula (1)). ), Coordinated to the transition metal M.

In the basic formula (1), at least one of R ^{1 to} R ³ has a structure in which an electron withdrawing group is bonded via an aryl group, and the remainder is a carboxy group. When a plurality of R ^{1 to} R ³ have a structure in which an electron withdrawing group is bonded via an aryl group, they may be the same or different. R ^{1 to} R ³ may be any one of the functional groups represented by formulas (2) to (5), for example. In the formula (3), R ^{4 to} R ⁸ may be all the same or all different but may be the same in part and different in part, and are an electron withdrawing group or hydrogen. In the formula (4), R ^{9 to} R ¹⁵ may be all the same, all different, or the same in part and different in part, and are an electron withdrawing group or hydrogen. In the formula (5), R ^{16 to} R ²⁴ may be all the same or all different but may be the same and partly different, and are an electron withdrawing group or hydrogen. In the basic formula (1), R ^{1 to} R ³ may be all the same or all different or may be partially the same and partially different. In addition, in Formula (1), the sign of-and + shows whether it is an anion or a cation, and does not show a specific valence. For this reason, the anionic complex may not be a monovalent anion, and the counter cation may not be a monovalent cation.

In the basic formula (1), a is an integer of 1 to 4, and a is preferably 1. When a is 1, R ¹ is preferably bonded to a position facing N of the pyridine structure. When a is 2 or more, each R ¹ may be the same functional group or different functional groups. b is an integer of 1 to 3, and b is preferably 1. When b is 1, R ² is preferably bonded to a position facing N of the pyridine structure. When b is 2 or more, each R ² may be the same functional group or a different functional group. c is an integer of 1 or more and 4 or less, and c is preferably 1. When c is 1, R ³ is preferably bonded to a position facing N of the pyridine structure. Moreover, when c is 2 or more, each R ³ may be the same functional group or a different functional group.

  In the basic formula (1), M is a transition metal. This transition metal may be one or more selected from Fe, Ru, Os, Pt, Ir, Re, Rh, and Pd. Of these, Ru and Os are preferable, and Ru is more preferable. This transition metal is preferably a transition metal ion having a divalent octahedral structure, for example.

In the basic formula (1), L ¹ , L ² and L ³ may be monodentate ligands (monovalent anionic ligands). These ligands L ¹ , L ² , and L ³ may be all the same or all different or may be partially the same and partially different. Among these, it is more preferable that all of these ligands are the same. These ligands L ¹ , L ² , and L ³ are assumed to be one or more selected from, for example, —F, —Cl, —Br, —I, —OH, —CN, —SCN, and —NCS. Also good. Among these, -SCN and -NCS are preferable, and -NCS (isothiocyanate group) is more preferable.

In the basic formula (1), Z ⁺ is a counter cation, and n is 1 or more and 2 or less. In such a case, there are one or more carboxy groups bonded to the pyridine structure in which protons are not ionized. The cation may be, for example, an alkali metal cation such as H ⁺ , K ⁺ , Na ⁺ , or Cs ^+, or may be an ammonium cation or a quaternary ammonium cation such as tetra n-butylammonium (TBA). . As the quaternary ammonium cation, for example, those having an alkyl straight chain having 1 to 8 carbon atoms (which may have a side chain) are preferable, and TBA is more preferable.

In this metal complex, it is preferable that a carboxy group is directly bonded to two of the three pyridine structures described above, and an electron withdrawing group is bonded to the remaining one through an aryl group. For example, in the above-described formula (1), two of R ^{1 to} R ³ are carboxy groups (formula (2)), and the other one is a structure in which an electron withdrawing group is bonded via an aryl group (for example, the formula (3) to (5)) are preferable. Among them, R ¹ and R ² are carboxy groups (formula (2)) and R ³ is a structure in which an electron withdrawing group is bonded via an aryl group (for example, formulas (3) to (5)), or R ^More preferably, ² and R ³ are a carboxy group (formula (2)) and R ¹ is a structure in which an electron withdrawing group is bonded via an aryl group (eg, formulas (3) to (5)).

  In this metal complex, it is preferable that at least one selected from the formulas (6) to (9) is bonded to at least one of the pyridine structures described above as an aryl group to which an electron withdrawing group is bonded. For example, in the formula (1) described above, the structure in which the electron withdrawing group is bonded via the aryl group is preferably selected from the formulas (6) to (9). This is because it is considered that the absorption coefficient can be further increased.

  In this metal complex, it is preferable that three isothiocyanate groups are coordinated as a ligand in addition to the tridentate terpyridine ligand to the transition metal ion described above. In this metal complex, the counter cation is preferably a tetrabutylammonium cation (TBA).

More specifically, such a metal complex is preferably one represented by the basic formula (10). In the basic formula (10), all of R ^{4 to} R ⁸ may be the same or all different, but the same or part may be different and are an electron withdrawing group or hydrogen. Z ⁺ is a counter cation, and n is 1 or more and 2 or less.

  This metal complex may be obtained by the production method shown below. Below, the manufacturing method of the metal complex of this invention is demonstrated. This production method includes, for example, (1) a ligand synthesis step for synthesizing a tridentate terpyridine ligand, and (2) a metal complex synthesis step for synthesizing a metal complex by coordinating a ligand to a transition metal ion. , May be included.

(1) Ligand synthesis step In this step, an electron-withdrawing group-bonded halide in which -X (X is a halogen group) is bonded to the 2-position or 6-position of the pyridine structure to which an electron-withdrawing group is bonded via an aryl group; And a tridentate terpyridine ligand by cross-coupling with an organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 6-position or 6′-position of the 2,2′-bipyridine structure. You may synthesize. Further, an electron-withdrawing group-bonded organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 2-position or 6-position of a pyridine structure in which an electron-withdrawing group is bonded via an aryl group; and a 2,2′-bipyridine structure A tridentate terpyridine ligand may be synthesized by cross-coupling with a halide in which —X (X is a halogen group) is bonded to the 6-position or 6′-position. The electron-withdrawing group-bonded halide used in the former is preferable because it is easier to isolate than the electron-withdrawing group-bonded organotin compound used in the latter. On the other hand, the latter is preferable because a tridentate terpyridine ligand can be obtained in a higher yield than the former. In the electron-withdrawing group-bonded halide and halide, X may be a halogen group, but more preferably a Br group. In the organotin compound and the electron-withdrawing group-bonded organotin compound, R may be an alkyl group, but more preferably a methyl group. In the halide and organotin compound, each pyridine constituting the bipyridine structure is preferably bonded to a carboxy group or an alkoxycarbonyl group, and a carboxy group or an alkoxycarbonyl group is located at a position opposite to N of each pyridine. Is more preferably bonded. As the alkoxycarbonyl group, a methoxycarbonyl group is preferable. In the electron-withdrawing group-bonded halide, organotin compound, electron-withdrawing group-bonded organotin compound, and halide, examples of the aryl group include a phenyl group, a naphthyl group, and an anthryl group. Of these, a phenyl group is preferred. Examples of the electron withdrawing group include a halogen group, a halogenated alkyl group (such as CF ₃ ), a cyano group, a nitro group, an aldehyde group, a carboxy group, a tosyl group, a mesyl group, a phenyl group, and an acyl group. . Of these, a halogen group, a halogenated alkyl group, a cyano group and the like are preferable. The method of cross coupling is not particularly limited, and for example, cross coupling may be performed by the action of a palladium catalyst.

In this step, the electron-withdrawing group bond halide represented by the formula (11) and the organotin compound represented by the formula (12) are cross-coupled, or the electron-withdrawing group bond represented by the formula (13) It is preferable to synthesize a tridentate terpyridine ligand by cross-coupling the tin compound and the halide represented by the formula (14). In the formulas (11) to (14), X may be a halogen group, but is preferably a Br group. R may be an alkyl group, but is preferably a methyl group. R ¹⁰¹ and R ¹⁰² may have a structure in which an electron withdrawing group is bonded via an aryl group or an alkoxycarbonyl group, but both are preferably an alkoxycarbonyl group, and more preferably a methoxycarbonyl group. R ¹⁰³ may have a structure in which an electron withdrawing group is bonded via an aryl group. For example, R ¹⁰³ is preferably one represented by the above formulas (3) to (5), and the above formulas (6) to (6) It is more preferable that it is shown by (9). a is an integer of 1 or more and 4 or less, b is an integer of 1 or more and 3 or less, and c may be an integer of 1 or more and 4 or less, but is preferably 1 in all cases.

In this step, the electron-withdrawing group bond halide represented by the formula (15) and the organotin compound represented by the formula (16) are cross-coupled or the electron-withdrawing group bond represented by the formula (17) is used. It is more preferable to synthesize a tridentate terpyridine ligand by cross-coupling the tin compound and the halide represented by the formula (18). In formulas (15) to (18), X may be a halogen group, but is preferably a Br group. R may be an alkyl group, but is preferably a methyl group. R ^{104 to} R ¹⁰⁸ may be all the same, all different or partially the same and partially different, and are an electron withdrawing group or hydrogen. R ¹⁰⁹ and R ¹¹⁰ may be the same or different and are hydrogen or an alkyl group, and preferably both are methyl groups.

In this step, when the electron-withdrawing group-bonded halide and the organotin compound are cross-coupled, for example, an electron-withdrawing group-bonded halide synthesis step and an organotin compound synthesis step described below may be included. In the electron-withdrawing group-bonded halide synthesis step, a pyridine compound having a structure in which —X (X is a halogen group) is bonded to the 2-position or 6-position of the pyridine structure, and benzene having a structure in which an electron-withdrawing group is bonded to the benzene ring For example, a compound such as a palladium catalyst is allowed to act on the compound for cross coupling. At this time, if the pyridine compound has a boronyl group or the like and the benzene compound has a halogen group such as a Br group, the coupling easily proceeds. The obtained compound may be used as an electron-withdrawing group-bonded halide as it is, or is subjected to a treatment for substituting —X with a compound suitable for subsequent cross-coupling with an organotin compound, and then combined with an electron-withdrawing group. It may be a halide. In the organic tin compound synthesis step, first, -X of a pyridine compound having a structure in which -X (X is a halogen group) is bonded to the 2-position or 6-position of the pyridine structure is tinned in the presence of a catalyst such as a palladium catalyst. (As -SnR ₃ (wherein R is an alkyl group)), a treatment for obtaining a stannated pyridine compound is performed. Subsequently, the resulting stannic pyridine compound and a compound in which —X (X is a halogen group) bonded to the 2nd and 6th positions of the pyridine structure are cross-coupled by acting a catalyst such as a palladium catalyst, A treatment for obtaining a bipyridine compound having -X (X is a halogen group) is performed. Finally, -X of the obtained bipyridine compound is tinned in the presence of a catalyst such as a palladium catalyst (as -SnR ₃ (where R is an alkyl group)) to obtain an organotin compound.

In this step, when the electron-withdrawing group-bonded organotin compound and the halide are cross-coupled, for example, the electron-withdrawing group-bonded organotin compound synthesis step and the halide synthesis step shown below may be included. Good. In the electron-withdrawing group-bonded organotin compound synthesizing step, -X (X is a halogen group) of the electron-withdrawing group-bonded halide obtained in the electron-withdrawing group-bonded halide synthesizing step is converted in the presence of a catalyst such as a palladium catalyst. It may be tinned (as -SnR ₃ (R is an alkyl group)). In the halide synthesizing step, in the above-described organotin compound synthesizing step, the last -X tinning of the bipyridine compound may be omitted, and the bipyridine compound having -X may be obtained as a halide.

  The ligand thus obtained is a tridentate terpyridine ligand having three pyridine structures, and at least one of the pyridine structures has an electron-withdrawing group bonded thereto via an aryl group, and the remaining pyridine structure. A carboxy group is bonded to.

(2) Metal complex synthesis process In this process, the process which forms the metal complex containing the anionic complex which coordinated the synthesized tridentate terpyridine ligand to the transition metal, and the counter cation attached to an anionic complex. Do. In this step, the transition metal may be coordinated with a tridentate terpyridine ligand, and one or more monodentate ligands may be further coordinated with the transition metal. Examples of the transition metal include one or more selected from Fe, Ru, Os, Pt, Ir, Re, Rh, and Pd. Of these, Ru, Os, and the like are preferable. The transition metal can be, for example, divalent or trivalent, and is preferably a transition metal ion having an octahedral structure as a divalent ion. In this step, a transition metal salt is used, but chloride is preferably used in terms of reaction control. In this step, after the tridentate terpyridine ligand is coordinated to the transition metal, the transition metal may be reduced, and the monodentate ligand may be coordinated to replace the counter cation. The monodentate ligand (monovalent anion ligand) is, for example, one or more selected from -F, -Cl, -Br, -I, -OH, -CN, -SCN, and -NCS. It may be a thing. Of these, -SCN and -NCS are preferred, and -NCS is more preferred. The introduced counter cation may be an alkali metal cation such as H ⁺ , K ⁺ , Na ⁺ , or Cs ^+, or a quaternary ammonium cation. Of these, quaternary ammonium cations are preferred.

  This metal complex may be adsorbed on the surface of a porous n-type semiconductor. This adsorption can be performed by chemical adsorption or physical adsorption. Specifically, after forming a porous n-type semiconductor layer on the transparent conductive substrate 14, a method of dropping a solution containing a metal complex onto the n-type semiconductor layer and drying it, or forming an n-type semiconductor layer The transparent conductive substrate 14 can be produced by immersing it in a solution containing a metal complex and then drying it.

  The electrolyte layer 26 is a layer that mediates the transfer of electrons between the counter electrode 30 and the photoelectrode 20, and may include, for example, a liquid or gel electrolyte. For example, the electrolyte layer 26 is preferably a layer containing an electrolytic solution in a porous body. The porous body is not particularly limited as long as it is capable of holding an electrolytic solution and does not have electron conductivity. For example, a porous body formed of rutile titanium oxide particles is used as the porous body. May be used. This porous body has a separator function. The porous body has a portion that covers the back surface 25 of the porous semiconductor layer 24 and a jaw-shaped edge portion that is in close contact with the side surface of the porous semiconductor layer 24 adjacent to the back surface 25. This bowl-shaped edge portion is in direct contact with the transparent substrate 11. In the connection portion between the transparent conductive substrate 14 and the porous body of the electrolyte layer 26, a part of the transparent conductive film 12 is completely scraped off by a technique such as laser scribing, and the surface of the transparent substrate 11 is exposed. A groove 18 having a depth is formed. The groove 18 is inserted with an edge portion of the electrolyte layer 26 formed in the shape of a bowl of a porous body.

  The electrolyte solution contained in the electrolyte layer 26 may contain an ionic liquid. Examples of the ionic liquid include 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMI-TFSI), 1-allyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (AMII-TFSI). ), Imidazolium salts such as 1-ethyl-3-methylimidazolium tetracyanoborate (EMI-TCB) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF4). Further, the electrolytic solution may contain an organic solvent instead of or in addition to the ionic liquid. Examples of the organic solvent include one or more of nitrile solvents such as methoxyproponitrile and acetonitrile, lactone solvents such as γ-butyrolactone and valerolactone, and carbonate solvents such as ethylene carbonate and propylene carbonate. . In addition, it is preferable that electrolyte solution contains an ionic liquid. By using a highly viscous ionic liquid with low vapor pressure and low volatility as the solvent of the electrolyte, it is considered that the solubility of the metal complex is low with respect to the organic solvent, and the elimination of the metal complex can be further suppressed. Because.

The electrolytic solution contained in the electrolyte layer 26 may include a redox pair. This redox pair mediates the transfer of electrons between the photoelectrode 20 and the counter electrode 30. A part of the electrolytic solution is usually impregnated in the photoelectrode 20 which is a porous body. Examples of the redox pair include I ₃ ⁻ / I ⁻ , Br ₃ ⁻ / Br ⁻ , hydroquinone / quinone, cobalt ion, iron ion, etc. Among these, I ₃ ⁻ / I ⁻ is particularly preferably used. Can do. Moreover, it is preferable that an electrolytic solution contains an ionic liquid containing iodine as a redox pair (iodine ionic liquid). Examples of the iodine-based ionic liquid include 1-propyl-3-methylimidazolium iodide (hereinafter abbreviated as PMII), 1,2 dimethyl-3-propylimidazolium iodide (DMPII), 1- Butyl-3-methylimidazolium iodide, 1-hexyl-3-methylimidazolium iodide, 1-allyl-3-ethylimidazolium iodide, 1,3-dimethylimidazolium iodide, 1,2-dimethyl-3 -Propyl imidazolium iodide etc. are mentioned.

  The electrolytic solution contained in the electrolyte layer 26 may contain an additive. As the additive, for example, guanidine thiocyanate (GuSCN), 4-tert-butylpyridine (4TBP), N-methyl-benzimidazole, and the like may be appropriately added. The concentration of the additive in the electrolytic solution is preferably in the range of 0.001 mol / L to 1.0 mol / L.

  The counter electrode 30 is formed in an L-shaped cross section having a bowl-shaped edge portion so as to contact the back surface 27 of the electrolyte layer 26 and the bowl-shaped edge portion. The counter electrode 30 is connected to the back surface of the electrolyte layer 26, and the flange-shaped edge portion is connected to the adjacent transparent conductive film 12 via the connection portion 21. The surface of the counter electrode 30 that is in contact with the back surface 27 of the electrolyte layer 26 faces the photoelectrode 20 at a predetermined interval. The counter electrode 30 is not particularly limited as long as it has conductivity and bondability with the electrolyte layer 26, and examples thereof include Pt, Au, and carbon. Among these, carbon is preferable. The counter electrode 30 may be, for example, a porous carbon electrode formed using carbon black particles, graphite particles, and conductive oxide particles such as anatase-type titanium oxide particles as constituent materials. The counter electrode 30 may be dispersedly supported with catalyst fine particles such as Pt fine particles, for example, from the viewpoint of more rapidly increasing the speed of the electrode reaction.

  The sealing material 32 is formed so as to cover the outer peripheral side of each dye-sensitized solar cell 40, and the main purpose is to prevent the electrolyte filled in the electrolyte layer 26 from leaking outside. Is provided. As the sealing material 32, for example, any insulating member can be used without any particular limitation, and a thermoplastic resin film such as polyethylene or ionomer resin, an epoxy adhesive, or the like can be used.

  The protection member 34 is a member that protects the dye-sensitized solar cell 40, and can be, for example, a moisture-proof film or protective glass.

  When the dye-sensitized solar cell 40 is irradiated with light from the light receiving surface 13 side of the transparent substrate 11, the light reaches the porous semiconductor layer 24 through the light receiving surface 15 and the light receiving surface 23 of the transparent conductive film 12. The dye absorbs light and generates electrons. Electrons move from the photoelectrode 20 to the adjacent counter electrode 30 via the transparent conductive film 12 and the connection portion 21. In the dye-sensitized solar cell 40, an electromotive force is generated by the movement of the electrons, and the power generation action of the battery is obtained.

  In this dye-sensitized solar cell module 10, since the metal complex described above is used as the sensitizing dye in the porous semiconductor layer 24, the absorption coefficient can be increased without greatly changing the absorption wavelength band (absorption edge). it can. The reason why such an effect can be obtained is assumed as follows. That is, by introducing an electron-withdrawing group via an aryl group into a terpyridine that directly contributes to the ligand field of a metal such as ruthenium having an octahedral structure, the electrons of the metal complex having a tridentate terpyridine ligand It is presumed that the effect of increasing the extinction coefficient can be obtained by maintaining the absorption wavelength band by the electron withdrawing group while maintaining the balance of density.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the dye-sensitized solar cell module 10 is used. However, the present invention is not particularly limited thereto, and the dye-sensitized solar cell 40 may be used. FIG. 2 is a cross-sectional view illustrating an example of a schematic configuration of the dye-sensitized solar cell 40. 2, the same components as those described in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 2, in the dye-sensitized solar cell 40 alone, the electrolyte layer 26 and the counter electrode 30 may not be L-shaped in cross section, but may be formed in a flat plate shape without a bowl-shaped edge portion. Good. The counter electrode 30 may be, for example, one having the same configuration as that of the transparent conductive substrate 14, or may be one in which platinum is attached to the transparent conductive film 12, or a metal thin film such as platinum. Further, the electrolyte layer 26 may be configured such that the porous body is omitted and the electrolytic solution is accommodated in the space between the photoelectrode 20 and the counter electrode 30.

  Below, the example which produced the dye-sensitized solar cell 40 concretely is demonstrated as an Example.

[Synthesis of metal complexes]
Example 1
In Example 1, diCF1 + nTBA (see formula (19)) was used as the metal complex. Below, the synthesis method of diCF1 is demonstrated. In this method, a ligand was first synthesized, and a complex dye diCF1 + nTBA was synthesized using this ligand.

(1) Ligand Synthesis (1-1) Ligand Synthesis Route FIGS. 3 to 5 are explanatory views showing the synthesis route of the complex dye. In this synthetic route, a ligand is synthesized using compound 2 synthesized by steps (a) to (b) in FIG. 3 and compound 5 synthesized by steps (c) to (e) in FIG. (Step (f) in FIG. 5). Below, process (a)-(f) is demonstrated. In the figure, Me represents a methyl group.

  In step (a), first, 1-bromo 3,5-bis (trifluoromethyl) benzene (compound a, 1.10 mL, 6.35 mmol) and tetrakis (triphenylphosphine) palladium (0) (0) (0 187 mg, 0.162 mmol) was dissolved in 1,2-dimethoxyethane under a nitrogen atmosphere and stirred at room temperature for 1 hour. Then, in another flask, (2-chloro-4-pyridyl) boronic acid (compound b, 1.0 g, 6.35 mmol) and sodium carbonate (1.21 g, 10.7 mmol) were added in 10 mL of ion-exchanged water. While stirring, a nitrogen flow was performed for about 1 hour to replace oxygen in ion-exchanged water. Then, the solution B was dropped into the flask containing the solution A with a pipette, mixed, and heated at about 100 ° C. for 10 hours under nitrogen. After cooling to room temperature, the organic layer was concentrated under reduced pressure and filtered to give a white solid. This solid was dried and purified with a silica column using chloroform as a developing solvent to obtain about 860 mg of a white solid. This was designated Compound 1.

  In step (b), compound 1 (300 mg, 0.92 mmol), acetic acid (10 mL), and hydrogen bromide (8 mL) were heated to reflux for about 24 hours with stirring in a nitrogen atmosphere. Thereafter, the mixture was concentrated under reduced pressure, and about 100 times equivalent amount of water was added to obtain the desired product. This was designated as Compound 2.

  In step (c), methyl 2-bromo-4-pyridinecarboxylate (compound c, 8.5 g, 39.53 mmol), hexamethyldistin (9.0 mL, 43.48 mmol), tetrakis (triphenylphosphine) palladium ( 0) (2.28 g, 1.98 mol) was dissolved in toluene under a nitrogen atmosphere. Then, it heated at 110 degreeC for 3 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and subjected to an alumina column using toluene as a developing solvent to obtain a yellow oil. This was designated as Compound 3.

  In step (d), compound 3 (2.0 g, 6.668 mmol), methyl 2,6-dibromopyridine-4-carboxylate (compound d, 2.0 g, 6.781 mmol), tetrakis (triphenylphosphine) palladium (0) (0.01 mol equivalent) was dissolved in toluene under a nitrogen atmosphere. Then, it heated at 110 degreeC for 10 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and subjected to silica column using dichloromethane as a developing solvent to obtain a white solid. This was designated as Compound 4.

  In step (e), compound 4 (351 mg, 1.0 mmol), hexamethyldistin (0.25 mL, 1.2 mmol), tetrakis (triphenylphosphine) palladium (0) (70 mg, 5.0 mol%) were added in a nitrogen atmosphere. Under dissolved in toluene. Then, it heated at 110 degreeC for 6 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and subjected to an alumina column using a mixed solvent of hexane and ethyl acetate as a developing solvent to obtain a white solid. This was designated as Compound 5.

  In the step (f), compound 5 (150 mg, 0.345 mmol), compound 2 (185 mg, 0.5 mmol), tetrakis (triphenylphosphine) palladium (0) (0.001 mol equivalent) was dissolved in toluene under a nitrogen atmosphere. Melted. Then, it heated at 110 degreeC for 18 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure, and subjected to molecular sieve chromatography using chloroform as a developing solvent to obtain a white solid (22 mg, 0.0392 mmol, yield 11%). This was designated as terpyridine L (ligand).

(1-2) Confirmation of ligand structure Structural analysis of the ligand (terpyridine L) obtained in step (f) using a ¹ H-NMR apparatus (solvent is deuterated chloroform) and a MALDI-MS mass spectrometer. Went. FIG. 6 shows the ¹ H-NMR result of the ligand. In FIG. 6, 11 protons in the aromatic region were confirmed. FIG. 7 shows the results of MALDI-MS mass spectrometry of the ligand. From FIG. 7, the ligand generally agreed with the theoretical value of the mass of terpyridine L in FIG. 5. From the above, it was confirmed that the ligand had the structure of terpyridine L in FIG.

(2) Synthesis of Complex Dye (2-1) Synthesis Route of Complex Dye FIG. 8 is an explanatory diagram showing a synthesis route of the complex dye. Hereinafter, steps (g) to (h) in FIG. 8 will be described.

  In step (g), terpyridine L (22 mg, 0.0392 mmol) was first dissolved in dichloromethane in the flask, and ruthenium chloride hydrate (15.0 mg, 0.0577 mmol) dissolved in ethanol was placed in the flask. The mixture was heated at 55 ° C. for 6 hours under a nitrogen atmosphere. After cooling to room temperature, the solution was concentrated under reduced pressure, washed with a small amount of ethanol and filtered to obtain 31 mg of a brown solid. This was designated as Compound 6.

  In step (h), compound 6 (31 mg) and ammonium thiocyanate (200 mg) were dissolved in N, N-dimethylformamide under a nitrogen atmosphere and heated to reflux. Then, after cooling to room temperature, 2.5 mL of triethylamine and 1.0 mL of water were added and heated at 110 ° C. for 24 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure, 100 mL of water was added, and the dark green precipitate was filtered and washed with water to obtain a complex dye diCF1 + nTEAH cation (TEAH: triethylamine) as a crude product.

(2-2) Purification of Complex Dye FIG. 9 is an explanatory diagram showing a purification procedure of the complex dye. For purification of complex dyes, first, crude diCF1 is dissolved in a mixed organic solvent (chloroform and methanol), purified on a silica column, and further purified using Sephadex (Sephadex is a registered trademark) with methanol as a developing solvent. As a result, the target product diCF1 was obtained. Finally, diCF1 dissolved in a small amount of water and a tetrabutylammonium hydroxide solution was titrated with nitric acid to obtain diCF1 + nTBA cation (high purity complex dye) as the final target.

(2-3) Structure confirmation of complex dye The purified complex dye (diCF1 + nTBA cation) was subjected to structural analysis using a ¹ H-NMR apparatus (solvent is deuterated methanol) and a MALDI-MS mass spectrometer. FIG. 10 shows the ¹ H-NMR result of the complex dye. In FIG. 10, 11 protons in the aromatic region were confirmed. It was also confirmed that the molar ratio of TBA ⁺ to diCF1 was 2.0. FIG. 11 shows the results of MALDI-MS mass spectrometry of the complex dye. From FIG. 11, the presence of diCF1 was confirmed. From the above, it was confirmed that the complex dye had the structure of diCF1 + nTBA (n = 2.0) cation in FIG.

(Comparative Example 1)
In Comparative Example 1, commercially available N749 (see formula (20) (n = 2.9)) was used as the metal complex.

[Measurement of absorption spectra of metal complexes]
The absorption spectra of the metal complexes of Example 1 and Comparative Example 1 were measured. Specifically, each metal complex was dissolved in methanol so as to have a concentration of 0.03 mM, and the absorption spectrum of the obtained solution was measured. The absorption spectrum was measured with a spectrophotometer (U-3400 manufactured by Hitachi, Ltd.) in a wavelength region of 300 nm to 900 nm. FIG. 12 shows absorption spectra of the metal complexes of Example 1 and Comparative Example 1. In the metal complex of Example 1 (diCF1-nTBA cation), the extinction coefficient in the vicinity of a wavelength of 400 nm was improved by about 9% compared to the metal complex of Comparative Example 1 (N749).

Furthermore, by enhancing the electron withdrawing property on the aryl group, the absorption wavelength band near 600 nm is made equal to N749, so that the solar cell performance can be improved without reducing the absorption in the long wavelength range (600 nm-900 nm). It was guessed. FIG. 13 shows the calculation result of the highest occupied orbital (HOMO) -lowest orbital (LUMO) energy gap of the complex dye by molecular orbital calculation as a relative value with N749 as 1.00. In Example 1 (A1 in the figure), since the HOMO-LUMO energy gap was larger than that in Comparative Example 1 (N749), A1 in Example 1 was changed to HOMO-LUMO energy such as A2, A4 and A5. It was inferred that a decrease in absorption in the long wavelength region can be further suppressed by using a narrow gap, particularly a narrow HOMO-LUMO energy gap such as A4. It has been inferred that the same effect can be obtained by introducing CN (cyano group) or the like in addition to F and CF ₃ as the electron withdrawing group. In addition to the phenyl group, it was speculated that the same effect can be obtained by using a naphthyl group, an anthryl group, or the like as the aryl group.

[Production of dye-sensitized solar cell]
Using the metal complexes of Example 1 and Comparative Example 1, respectively, dye-sensitized solar cells of Example 1 and Comparative Example 1 were produced. First, a titania paste containing titania (TiO ₂ ), which is an n-type semiconductor, was applied to a glass substrate with a transparent conductive film (TCO) by a screen printing method. This titania electrode was immersed in a metal complex solution to prepare a dye-adsorbing titania electrode. The titania side of this electrode and the Pt side of the TCO substrate carrying Pt were bonded together, and an electrolyte was sealed between them to produce a dye-sensitized solar cell.

The electrolyte was an iodine compound, 0.2 mol / L of I ₂ , 65% by volume of 1-propyl-3-methylimidazolium iodide (PMII), and 1-ethyl-3-methylimidazolium ion as a solvent. An ionic liquid composed of (EMI) and bis (trifluoromethanesulfonyl) imide ion (TFSI) is 35% by volume. As an additive having a charge, guanidine thiocyanate (GuSCN) is 0.5 mol / L, 4-tert-butylpyridine (4TBP). ) Was used.

[Measurement of external quantum efficiency]
The external quantum efficiency was measured using a spectral sensitivity measuring apparatus (CEP-2000 manufactured by Spectrometer Co., Ltd.). Specifically, light monochromatized using a monochromator is applied to the photoelectrodes of the dye-sensitized solar cells of Example 1 and Comparative Example 1, and the number of electrons obtained with respect to the number of incident photons is measured. Thus, the external quantum efficiency (Incident Photon to Current Conversion Efficiency (IPCE)) was obtained.

  FIG. 14 shows the measurement results of the external quantum efficiency (IPCE) of the cell 14 days after the 1 sun 60 ° C. operation durability test of Example 1 and Comparative Example 1. From FIG. 14, it was found that in Example 1, the quantum efficiency in the vicinity of a wavelength of 400 to 600 nm can be increased.

[Measurement of solar cell characteristics]
Example 1 using an AM1.5G solar simulator (WXS-155S-L2, Wacom Denso) and an IV tester (IV-9701, Wacom Denso) equipped with a 1 kW xenon lamp and a 400 W halogen lamp The current (I) -voltage (V) characteristics (IV characteristics) of the dye-sensitized solar cell of Comparative Example 1 were measured. In the measurement, the dye-sensitized solar cells of Example 1 and Comparative Example 1 were irradiated with 1 sun (= 1000 W / m ² ) of 60 ° C. light for 336 hours.

  The measurement result of the solar cell characteristic of Example 1 and Comparative Example 1 is shown in FIG. Specifically, a short circuit current density (Jsc), an open circuit voltage (Voc), a form factor (FF), a conversion efficiency (Eff), etc. are shown. These are all expressed as relative values when Comparative Example 1 is 1.000. As shown in FIG. 15, Example 1 showed performance equal to or better than Comparative Example 1.

[Results and discussion]
As described above, in Example 1, the electron withdrawing group was introduced into N749 (Comparative Example 1). However, by introducing the electron withdrawing group through the aryl group, the performance was equal to or higher than that of N749. And it turned out that it operates as a solar cell. Further, in Example 1, it was found that the extinction coefficient can be increased particularly in the vicinity of the wavelength of 400 nm without largely changing the absorption wavelength band.

  The present invention can be used in the technical field of solar cells.

  10 Dye-sensitized solar cell module, 11 Transparent substrate, 12 Transparent conductive film, 13 Light receiving surface, 14 Transparent conductive substrate, 15 Light receiving surface, 16, 17 Current collecting electrode, 18 Groove, 20 Photo electrode, 21 Connection portion, 23 Photosensitive surface, 24 Porous semiconductor layer, 25 Back surface, 26 Electrolyte layer, 27 Back surface, 30 Counter electrode, 32 Sealing material, 34 Protection member, 40 Dye-sensitized solar cell.

Claims (13)

It has a transition metal ion and three pyridine structures coordinated to the transition metal ion. At least one of the pyridine structures has an electron-withdrawing group bonded thereto via an aryl group, and the remaining pyridine structure has a carboxy structure. An anionic complex having a tridentate terpyridine ligand to which a group is bonded;
A counter cation attached to the anionic complex,
At least one selected from the formulas (1) to (4) is bonded to at least one of the pyridine structures as an aryl group to which the electron withdrawing group is bonded,
In addition to the tridentate terpyridine ligand, three isothiocyanate groups are coordinated as ligands to the transition metal ion.
Metal complex.
The metal complex according to claim 1, which is represented by the basic formula (5).
(In the formula, at least one of R ^{1 to} R ³ is a structure in which an electron withdrawing group is bonded via an aryl group, and the remainder is a carboxy group. A is an integer of 1 to 4, and b is 1 or more. C is an integer of 3 or less, c is an integer of 1 to 4. M is a transition metal, L ¹ , L ² and L ³ are the isothiocyanate groups , Z ⁺ is a counter cation. , N is 1 or more and 2 or less.)   The metal complex according to claim 1 or 2, wherein a carboxy group is directly bonded to two of the three pyridine structures, and an electron withdrawing group is bonded to the remaining one through an aryl group.   4. The metal complex according to claim 1, wherein the transition metal is one or more selected from Fe, Ru, Os, Pt, Ir, Re, Rh, and Pd.   The metal complex according to any one of claims 1 to 4, wherein the counter cation is a tetrabutylammonium cation. The metal complex according to any one of claims 1 to 5, which is represented by the basic formula (6).
(In the formula, R ⁴ is one or more groups selected from the formulas (1) to (4), Z ⁺ is a counter cation, and n is 1 or more and 2 or less.)   A dye-sensitized solar cell using the metal complex according to any one of claims 1 to 6 as a dye. A photoelectrode comprising a semiconductor layer containing the metal complex according to any one of claims 1 to 7 as a pigment on a transparent conductive substrate;
A counter electrode arranged to face the photoelectrode;
An electrolyte layer interposed between the photoelectrode and the counter electrode;
A dye-sensitized solar cell comprising:   A dye-sensitized solar cell module comprising a plurality of the dye-sensitized solar cells according to claim 7 or 8. A method for producing a metal complex having a tridentate terpyridine ligand, wherein -X (X is a halogen group) is bonded to the 2- or 6-position of the pyridine structure in which the electron-withdrawing group is bonded via an aryl group. The group-bonded halide is cross-coupled with an organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 6-position or 6′-position of the 2,2′-bipyridine structure, or electrons are bonded via an aryl group. An electron-withdrawing group-bonded organotin compound in which —SnR ₃ (R is an alkyl group) is bonded to the 2-position or 6-position of the pyridine structure to which the attractive group is bonded; and the 6-position or 6′-position of the 2,2′-bipyridine structure; A ligand synthesis step of synthesizing the tridentate terpyridine ligand by cross-coupling with a halide to which -X (X is a halogen group) is bonded;
Forming a metal complex comprising an anionic complex in which the synthesized tridentate terpyridine ligand is coordinated to a transition metal and a counter cation attached to the anionic complex,
In the ligand synthesis step, the pyridine structure in which one or more structures selected from formulas (7) to (10) are bonded as an aryl group to which the electron withdrawing group is bonded is used.
A method for producing a metal complex.
In the ligand synthesis step, the electron-withdrawing group-bonded halide represented by the formula (11) and the organotin compound represented by the formula (12) are cross-coupled or represented by the formula (13). The metal complex according to claim 10, wherein the tridentate terpyridine ligand is synthesized by cross-coupling the electron-withdrawing group-bonded tin compound and the halide represented by the formula (14). Method.
(Wherein X is a halogen group and R is an alkyl group. R ¹⁰¹ and R ¹⁰² are one or more structures selected from formulas (7) to (10) or an alkoxycarbonyl group, and R ¹⁰³ is It is one or more structures selected from formulas (7) to (10), a is an integer of 1 to 4, b is an integer of 1 to 3, and c is an integer of 1 to 4. is there.)   In the ligand synthesis step, the organotin compound is synthesized by a tinning process of -X (X is a halogen group) bonded to the 6-position or 6'-position of the 2,2'-bipyridine structure. The method for producing a metal complex according to claim 10 or 11, wherein the tridentate terpyridine ligand is synthesized by coupling a compound and the electron-withdrawing group-bonded halide.   In the metal complex synthesis step, after the tridentate terpyridine ligand is coordinated to the transition metal, the transition metal is reduced, and three isothiocyanate groups as monodentate ligands are coordinated. The manufacturing method of the metal complex of any one of Claims 10-12 which performs substitution of a cation.