Bi-pyridyl-rumetal complexes

Details Bi-pyridyl-rumetal complexes Bi-pyridyl-rumetal complexes

1994-04-20

1995-10-31

Ivy, C. Warren

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D21322, C07D40104, C07F 1500

Patent

active

054630576

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 application of PCT/EP93/02221.
The invention relates to new transition metal dyestuffs and to their use in photovoltaic cells. These dyes can be coated on titanium dioxide films rendering the device effective in the conversion of visible light to electric energy.
Titanium dioxide films (layers) are known for their semiconductive properties and this property renders them useful for photovoltaic cells. However titanium dioxide has a large band gap and therefore it does not absorb light in the visible region of the spectrum. For solar applications it is important that the titanium dioxide film be coated with a photosensitizer which harvests light in the wavelength domain where the sun emits light, i.e. between 300 and 2000 nm. Thermodynamic considerations show that conversion of solar energy into electricity is achieved in the most efficient fashion when all the emitted photons with wavelengths below 820 nm are absorbed by the photosensitizer. The optimal dye for solar conversion should therefore have an absorption onset around 800 nm and the absorption spectrum should be such that it covers the whole visible domain.
A second requirement for efficient solar light energy conversion is that the dyestuff after having absorbed light and thereby acquired an energy-rich state is able to inject with practically unit quantum yield, an electron in the conduction band of the titanium dioxide film. This requires that the dyestuff is attached to the surface of the titanium dioxide through suitable interlocking groups. The function of the interlocking group is to provide electronic coupling between the chromophoric group of the dyestuff and the conduction band of the semiconductor. This type of electronic coupling is required to facilitate electron transfer between the excited state of the dyestuff band the conduction band. Suitable interlocking groups are p-conducting substituents such as carboxylate groups, cyano groups, phosphate groups or chelating groups with p-conducting character such as oximes, dioximes, hydroxy quinolines, salicylates and alpha keto enolates. The electrons, photoinjected by the dyestuff, generate electrical current in the external circuit when the photovoltaic cell is operated.
Accordingly a new series of dyes has been developed to act as a photosensitizer.
According to the invention, there is provided a compound of formula I and SeCN; and ##STR1## and L, is selected from a ligand of formula a) to g) ##STR2## where each R independently is selected from OH, hydrogen, C.sub.1-20 alkyl, --OR.sub.2 or --N(R.sub.a).sub.2
Preferred groups of L, are those of formula a) b) c) and d).
Preferably X is X' where X' is Cl, CN, --NCO or --SCN.
Preferably L.sub.1, is L.sub.1 ', where L.sub.1 ', is selected from a ligand of formula a', b, and c' ##STR3## in which R' is OH, hydrogen or C.sub.1-20 alkyl, (more preferably R" where R" is hydrogen or C.sub.1-20 alkyl).
More preferred compounds of formula I are of formula II ##STR4## L is as defined above: X' is selected from Cl, CN --NCO and SCN; and
Most preferably L" is a ligand of the formula b) ##STR5## Especially preferred is cis and trans (preferably cis)-dithiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium (II).
Preferably in formulae a, a' and a", the group R and R' respectively are located in the para position to the N atom in the 4-position.
According to the invention there is provided a photovoltaic cell comprising: on a support (preferably glass plate a transparent polymer sheet or a metal surface) to which one or more (preferably porous high surface area) titanium dioxide layers have been applied, characterized by applying a compound of formula I defined above (as a photosensitizer) to the TiO.sub.2 layer.
Still further according to the invention, there is provided a photovoltaic cell comprising: light transmittance of at least 60%, the plates being arranged so as to define a receptacle between them, in which receptacle an electrolyte is located, one of the electrodes having a film of titanium dioxide (preferably high s

REFERENCES:
patent: 4125414 (1978-11-01), Tang et al.
patent: 4127738 (1978-11-01), Ghosh et al.
patent: 5112974 (1992-05-01), Barton
Chemical Abstracts, vol. 90, No. 4, Abstract 29,446u, p. 384, Jan. 22, 1979.
Chemical Abstracts, vol. 87, No. 16, Abstract 125,308j, p. 522, Oct. 17, 1977.
Chemical Abstracts, vol. 95, No. 10, Abstract 88,183g, p. 479, Sep. 7, 1981.

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