Electronic transport in molecular solids and liquids

This paper is concerned with some of the more fundamental aspects of electronic transport in molecular crystals and liquids. If the wavefunctions of molecular states associated with the excess charge carriers overlap strongly, the transport can be described on a delocalized model, as in conventional semiconductor theory. This applies to the solids and liquids formed from the rare gases Ar, Kr, and Xe. In the majority of molecular solids, however, the excess carriers are more strongly localized, and vibrational interaction is likely to play a predominant role, with the formation of small polarons. The resulting conduction mechanisms are discussed with particular reference to drift mobility and optical studies on orthorhombic sulfur, both in the crystalline and the liquid states.