Organic semiconductors for the new millennium

Organic semiconductors are carbon-based materials capable of transporting charged excitations and interacting with visible radiation. For this reason they can replace conventional inorganic semiconductors in optoelectronic devices such as light-emitting diodes, photovoltaic cells and field-effect transistors. Organic chemistry offers a wide variety of tools for tailoring the functional properties of these materials, essentially molecular and macromolecular in nature, via addition or substitution of carefully designed chemical groups. This also provides the opportunity for transduction of chemical or biochemical interactions into optoelectronic signals, and hence for the fabrication of chemo- and bio-sensors. Very cheap manufacture, the possibility of covering large-area and flexible substrates with an immense freedom in the tunability of the electronic and optical properties are the promise of organic, possibly polymeric, optoelectronics for the next millennium. In this paper we briefly review some aspects of the basic physics and give an account of the state-of-the-art reached so far in turning these materials into useful devices. Finally, we attempt to project how the development of the latter may link up to progress in the biotechnologies.