Within the Consolider HOPE project (projects funded by the
Ministry of Innovation and Science), a group of scientists at Universidad Pablo de
Olavide (UPO), headed by Juan Antonio Anta, are working on the optimization
of a type of photovoltaic cell (Grätzel cell) that artificially mimics
photosynthesis.
Grätzel cells are photovoltaic devices that take advantage
of the interaction of a structured semiconductor less than nanometer in size
and an organic dye that acts as a solar collector.
According to Elena Guillén, member of UPO's Coloides y
Celdas Solares Nanoestructuradas (Nanostructured Colloids and Solar Cells)
Group, this dye can be either synthetic or natural and can even enable the use
of chlorophyll for this type of cell.
Thus, researchers at UPO have begun a study with which they
hope to increase the efficiency of these eosin or mercurochrome -based organic
components by incorporating ionic salts, known as green solvents, with a view
to preventing evaporation of the liquid compounds and the consequent reduction
in efficiency.
Previous studies show that ionic salts are less volatile and
it is this characteristic that the group headed by Professor Anta seeks to
exploit. "Notwithstanding its liquid state, these types of solvents have
high viscosity levels and, therefore, during the coming months we will continue
our study, working on different alternatives within ionic liquids, their
synthesis, etc.," comments Elena Guillén.
The pros and cons of
the new generation
Although there are already some third generation cells on
the market (for example, for recharging mobile phones), according to the
researchers their practical use is anecdotal. However, due to their properties
of flexibility and variety of colors and shapes, the future of these cells lies
in new market niches such as decoration or use in colored windows that not only
allow light through but use this light to generate electricity.
On the other hand, apart from the rapid amortization of
energy production costs—estimated in one year's use—there is also the low cost
of the materials.
"Organic materials are usually cheaper," affirms
the researcher, despite which the search continues for an alternative organic
dye to the one currently used, derived from ruthenium.
"The paradox lies in the fact that if one uses these
cells because their competitive edge is that they are cheaper and more readily
available, and then one uses a dye based on a precious metal, what is the
advantage?" points out Elena Guillén.
On the other hand, the researchers are aware that it is a
relatively new technology—this type of cell was invented in 1991—that still
need to be greatly developed. Furthermore, the maximum efficiency obtained in
laboratory is only 11%, which is competitive but it drops when extrapolated to
an industrial scale.
The main technological challenge is currently the problem of
cell degradation. "If you use an organic dye, it can be degraded by the
action of sunlight, with the consequent reduction in useful life compared to
silicon cells. On the other hand," the researcher highlights, "our
group is working on one of the key aspect for improving cell stability—elimination
of the need to use liquids that can present problems with evaporation, etc. and
for which, as already mentioned, our focus is on the use of ionic salts."
