The class of plastic materials for which metallic and semiconductor characteristics can be observed are conjugated polymers. The semiconductor properties of these materials arise from the overlap of p z orbitals that originate from the double or triple bonds. Thus device designs and material structures can be copied into the new technology. For example the use of heterostructures, commonplace in III-V technology can also be applied to polymer devices for improved carrier confinement, or for varying offsets with respect to injection electrodes. The principal disadvantages are lifetime and mobility.
Mobilities are low due to the largely amorphous nature of conjugated polymer films.
Many of the applications of interest are for large area devices where the polymer materials would be an alternative to amorphous silicon. Lifetime is also a big concern when considering commercial applications of the technology. Much work has taken place over the last 50 years to improve the resistance of everyday polymers to photo oxidation principally through the use of additives to prevent discoloration. In the area of light emitting polymers significant activity is taking place to improve material lifetimes both through use of materials that are resistant to oxidation and through improved encapsulation. Conjugated polymers have found there first commercial applications as conductors.