organicsolarcells

Until 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 devices.

Figure 1: Example of test solar cells resulting of dye sensitised semiconductor switched between two electrical conducting glasses.

Figure 2: Example of a larger solar cell based on the same principle as in figure 1.

History
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 manner.