Metal complex useful as sensitizer, dye-sensitized oxide...

Details Metal complex useful as sensitizer, dye-sensitized oxide... Metal complex useful as sensitizer, dye-sensitized oxide...

1999-03-18

2001-08-21

Diamond, Alan (Department: 1753)

Batteries: thermoelectric and photoelectric

Photoelectric

Cells

C136S252000, C136S256000, C257S040000, C257S428000, C257S431000, C429S111000, C546S002000, C546S008000, C546S009000, C546S010000, C546S011000, C546S012000, C548S101000, C548S107000, C548S108000, C548S109000, C556S137000, C556S138000, C556S140000, C556S145000, C556S146000

Reexamination Certificate

active

06278056

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a metal complex having an organic dye ligand and to an electrode having a surface on which such a metal complex has been adsorbed. The present invention is also directed to a solar cell using such an electrode.
One known solar cell uses an oxide semiconductor electrode containing titanium oxide. It is also known to adsorb a sensitizing organic dye capable of absorbing a light of a visible region on such an electrode for the purpose of improving light energy absorbing efficiency thereof. The known sensitizing organic dye is, however, not fully satisfactory, because the wavelength region of light which can be absorbed by the dye is not sufficiently broad and because the coefficient of absorption of the dye is not high.
SUMMARY OF THE INVENTION
It is, therefore, the prime object of the present invention to provide a metal complex which can efficiently absorb solar light and which is useful as a sensitizer.
Another object of the present invention is to provide a dye-sensitized oxide semiconductor electrode using the above sensitizer.
It is a further object of the present invention to provide a solar cell using the above electrode, which has a high photoelectric transfer efficiency.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a metal complex represented by one of the following formulas (1)-(3):
wherein M represents a Group VIII metal, X represents a polar group, L
1
represents a phenanthroline containing at least one carboxyl group which may be neutralized, L
2
represents a nitrogen-containing polycyclic compound which may contain one or more substituents, and n is an integer of 1 or 2.
In another aspect, the present invention provides a dye-sensitized oxide semiconductor electrode comprising an electrically conductive body, an oxide semiconductor film provided on a surface of said electrically conductive body, and the above metal complex adsorbed on said film.
The present invention also provides a solar cell comprising the above dye-sensitized oxide semiconductor electrode, a counter electrode, and a redox electrolyte contacting with said dye-sensitized oxide semiconductor electrode and said counter electrode.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
In the above formulas (1)-(3), M stands for a metal belonging to Group VIII of the Periodic Table. Illustrative of suitable Group VIII metals are Fe, Ru, Os, Pd, Rh and Ir. Particularly preferred is the use of Fe, Ru or Os.
Any polar group may be used as the group X. Illustrative of suitable polar groups are halogen atoms (such as Cl, Br and I), a thiocyanate group (SCN), a hydroxyl group (OH), a cyan group (CN), an isocyanate group (NCO) and a selenocyan group (SeCN). The polar group serves to improve the adsorbing efficiency of the metal complex on a surface of an oxide semiconductor.
The group L
1
represents a first organic ligand and is a phenanthroline containing at least one carboxyl group (COOH) or at least one neutralized carboxyl group (COOM
1
), where M
1
is a cation such as an ammonium ion, a substituted ammonium ion or a metal ion such as an alkali metal ion). The substituted or unsubstituted ammonium ion may be represented by the formula (4):
—COO
−
.N
+
(R
11
)(R
12
)(R
13
)(R
14
)  (4)
wherein R
11
, R
12
, R
13
and R
14
each stand for a hydrogen atom or an alkyl group which is preferably a lower alkyl group such as C1 to C4 alkyl group.
The number of the carboxyl group (which may be neutralized) contained in the phenanthroline is at least one, preferably at least 2. The upper limit of the carboxyl group is not specifically limited but is generally 4. The carboxyl group (which may be neutralized) of L
1
serves to improve the adsorbing efficiency of the metal complex on a surface of an oxide semiconductor. The phenanthroline can contain one or more substituents such as a hydroxyl group, an alkoxy group, an alkyl group and substituted or unsubstituted amino group. Illustrative of suitable phenanthroline compounds are as follows:
wherein M
1
is as defined above.
The group L
2
represents a second organic ligand and is a nitrogen-containing polycyclic compound which may contain one or more substituents. The term “polycyclic compound” herein is intended to refer to a compound having two or more nitrogen-containing rings which may be condensed rings or rings connected to each other through a direct bond or a divalent group. Illustrative of suitable nitrogen-containing polycyclic compounds are as follows:
In the above structural formulas (a)-(f), R represents a hydrogen atom or an organic substituent such as a hydroxyl group, a lower alkyl group such as C1-C6 alkyl group, a lower alkoxy group such as C1-C6 alkoxy group, an unsubstituted amino group or an amino group having a substituent such as a lower alkyl group, e.g. C1-C4 alkyl group. The above nitrogen-containing polycyclic compounds are known per se.
The above described metal complex according to the present invention may be produced, for example, as follows.
In the case of the preparation of a metal complex of the formula (2) [RuL
1
2
(NCS)
2
], L
1
is first produced. For example, in a case where L
1
is a compound of the formula (5) in which M
1
represents a hydrogen atom, a dialdehyde corresponding to the compound L
1
is first refluxed in 70% nitric acid for 3 hours. The reaction mixture is then poured into a vessel containing ice to obtain the compound L
1
. This is then mixed with 0.5 equivalent of ruthenium chloride and dimethylformaide and the mixture is refluxed to obtain crude RuL
1
2
Cl
2
. After purification, 200 mg of RuL
1
2
Cl
2
are mixed with 990 mg of ammonium thiocyanate ((NH4)NCS) and 50 ml of dimethylformamide and the mixture is refluxed for 4 hours to obtain 150 mg of RuL
1
2
(NCS)
2
. This is further treated with tetrabutylammonium hydroxide to obtain a compound of the formula:
RuL
1
2
(NCS)
2
(8)
in which L
1
represents the compound of the formula (5) in which one of the two M
1
radicals is a hydrogen atom and the other M
1
is tetrabutylammonium ion [(C
4
H
9
)
4
N]. In the above reaction, the compound of the formula (5) can be replaced by the compound of the formula (6) or by a mixture of the compounds (5) and (6).
By using another Group VIII element in place of Ru, ML
1
2
(NCS)
2
can be obtained in the same manner as above.
By using H
2
O, (NH
4
)CN, (NH
4
)NCO or (NH
4
)SeCN in place of (NH
4
)NCS, a metal complex of the formula ML
1
2
(OH)
2
, ML
1
2
(CN)
2
, ML
1
2
(NCO)
2
or ML
1
2
(SeCN)
2
can be obtained in the same manner as above.
A metal complex of the formula (3) [(L
1
)
2
ML
2
] may be prepared by, for example, reacting RuL
1
2
Cl
2
with a second organic ligand of the formula (a)-(f).
A metal complex of the formula (1) [(X)
n
ML
1
L
2
] may be produced as follows. A halide of a Group VIII metal is reacted with one equivalent of a compound corresponding to the first organic ligand L
1
(e.g. a compound of the formula (5) or (6) or a mixture of the compounds (5) and (6)) and then with a compound corresponding to the second organic ligand L
2
(e.g. a compound of the formula (a)-(f) or a mixture thereof) to obtain (X)
n
ML
1
L
2
(X: halide). Alternatively, a halide of a Group VIII metal may be first reacted with one equivalent of a compound corresponding to the second organic ligand L
2
and then with a compound corresponding to the first organic ligand L
1
. If desired, the resulting product (X)
n
ML
1
L
2
(X: halide) may be reacted with H
2
O, (NH
4
)CN, (NH
4
)NCO or (NH
4
)SeCN to substitute the halide with OH, CN, NCO or SeCN.
Metal complexes of the formula (1)-(3) in which L
1
is a phenanthroline containing at least one carboxyl group (COOH) may be converted into the corresponding metal complexes in which L
1
is at least one neutralized carboxyl

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