now, photovoltaics, the conversion of sunlight to electrical power, has been
dominated by solid-state junction devices, often made of silicon. But this dominance
is now being challenged by the emergence of a new generation of photovoltaic
cells, based on, for example, on nanocrystalline materials and conducting polymer
films. These offer the prospect of cheap fabrication together with other attractive
features such as flexibility. Contrary to expectations, some of the new devices
have strikingly high conversion efficiencies, which compete with those of conventional
1: Example of test solar cells resulting of dye sensitised semiconductor switched
between two electrical conducting glasses.
Example of a larger solar cell based on the same principle as in figure 1.
Becquerel did first photoelectric experiments in 1839 where he observed an
electrical current arising between two electrodes after illumination of a
metal chloride salt solution. After the first photographic picture in 1837
by Daguerre, numerous efforts have been invest to rise photographic film sensitivity.
At the beginning, films made with silver chloride were not sensible to red
light. In 1883, Vogel discovered it was possible to sensitise silver salts
to longer wavelength by addition of a dye to the photographic emulsion. It
was the beginning of semi-conductor sensitisation.
No longer than
40 years before, sensitisation experiences on semi-conductors demonstrated
the best efficiencies observed were obtained when dye was dispersed in monolayer