Organic materials with optical properties

Microelectronics based on semi-conductors plays an important role in inform ation technology since several decades. However, for the high rates needed for todays highly performing systems of telecommunications, the new optoele ctronic technologies use processes involving the photon as well as the elec tron. Thus, what is usually called "Molecular Optoelectronics" has been dev eloped since over the last ten years: it requires the expertise of both phy sicists and chemists. This molecular approach of information technology is based on a deep knowledge at the molecular level, from which are built comp lex supramolecular assemblies having specific physical properties. This are a of investigation is nearly infinite since the choice of molecules able to supply the elementary bricks of the assemblies is unlimited, It has also t o take into account the establishment of strong correlations between the st ructure and the optoelectronic properties of the supramolecular assemblies. Due to the large possibilities of molecular engineering, organic materials are very promising for many optoelectronic applications. In this chapter w e will describe three of them. The first one deals with fullerene derivativ es which can be used in photovoltaic cells. The second one concerns photore fractive polymers for recording and storage of optical informations in holo grams. Finally, the third one concerns electroluminescent conjugated oligom ers and polymers used in large flat displays. In connection with the latter , the way to prepare and to control the quality of thin films obtained by t he Langmuir-Blodgett technique will be described.