Molecular electronics. Aspects of the physics

Conjugated (unsaturated) polymers are particularly promising for molecular electronics. They differ from the more common saturated polymers by having a delocalised electronic structure that can accommodate charge carrying species (eg holes and electrons). In addition, the excited states (shown by an asterisk) of the conjugated polymers do not simply correspond to the antibonding (σ*) levels of specific bonds, as in saturated molecules, but are excited states of the whole conjugated bonding network. This paper reviews the physical concepts underlying the conductivity of conjugated polymers and their application as semiconductors in electronic and electrooptical devices, including electroluminescence devices.