Chemistry: electrical current producing apparatus – product – and – Deferred action type – Responsive to light
Patent
1993-12-30
1995-08-15
Weisstuch, Aaron
Chemistry: electrical current producing apparatus, product, and
Deferred action type
Responsive to light
H01M 636
Patent
active
054418275
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a regenerating photoelectrochemical cell and, more particularly, to a cell of this type that does not absorb, or that very weakly absorbs electromagnetic radiation having wavelengths in the visible range. The term regenerating photoelectrochemical cell is generally understood to mean an electrochemical system in which the reactions at the electrodes are reversible and in which the different types of chemicals involved are preserved.
Regenerating photoelectrochemical cells of the semiconductor oxide/electrolyte interface type are already known. In these cells, the semiconductor oxide is deposited in the form of a continuous layer on a substrate previously covered with an electrode. However, the disadvantage of these cells is that they only absorb a very small proportion of the incident light, with the result that their efficiency is too low to produce a utilizable amount of energy.
PCT International Patent Application WO 91/16719 discloses a regenerating photoelectrochemical cell having a titanium dioxide layer which is produced in the form of a porous nanostructure formed of sintered colloidal particles and covered with a monomolecular layer of chromophors. Although providing a high efficiency, this cell nonetheless has the disadvantage that it absorbs a large amount of the incident light with wavelengths in the visible and ultraviolet regions. There are, however, numerous applications for which it is preferable or even essential that the cell does not absorb light in the visible range.
European patent EP 407 182 describes a photoelectrochemical cell comprising, among others, a porous membrane of semiconductor oxide formed of sintered colloidal particles and having no chromophors. The efficiency of a cell of this type is, however, not entirely satisfactory.
OBJECTS AND SUMMARY OF THE INVENTION
It is thus a main object of the invention to overcome the disadvantages of the above-mentioned prior art by providing a regenerating photoelectrochemical cell which does not diffuse incident light and which does not absorb light having wavelengths in the visible range, while still presenting a satisfactory conversion rate from incident light energy into electrical energy.
For this purpose, an object of the invention is a regenerating photoelectrochemical cell having a first transparent substrate which has a first transparent electrode, a second transparent substrate which has a second transparent electrode on which is deposited a first layer of a photoelectrochemically active semiconductor oxide in the form of a porous nanostructure formed of sintered colloidal particles, the substrates being so disposed in relation to one another as to define a space filled with electrolyte, said electrolyte impregnating said porous structure in a manner such that it is in contact on the one hand with the electrode disposed on the first substrate and on the other hand with the electrode disposed on the second substrate, characterised in that the second substrate also has a second compact continuous semiconductor oxide layer extending between the second electrode and the first semiconductor oxide layer.
The presence of this second layer substantially increases the efficiency as well as the stability of the cell according to the invention, without the need to add chromophors, with the result that a cell is obtained which is transparent to light having wavelengths in the visible range and which is non-diffusing while operating satisfactorily in various applications.
The field of application of the cell is greater than that of cells of the prior art. All the layers forming the cell of the invention are thus invisible to the naked eye.
According to one feature of the invention, the second semiconductor oxide layer is of the same material as the first semiconductor oxide layer.
The thickness of the second semiconductor oxide layer is preferably between 10 and 50 nanometers.
According to another feature of the invention, the first substrate also has an electrocatalytic layer extendin
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Gratzel Michael
Saurer Eric
Asulab S.A.
Weisstuch Aaron
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