Charge transport in molecular solids: dynamic and static disorder

Abstract

Recent controversial issues in charge transport in molecular solids are discussed, with focus on the effects of static and dynamic disorder. The situation in ordered solids such as aromatic hydrocarbon crystals is reviewed with attention to the nature of charge carriers, and the theoretical development that led to the now accepted idea that the carriers are polaronic as a result of strong interaction with librations is described. Next, recent experiments on disordered solids (specifically molecularly doped polymers), are reviewed, and our theoretical work directed at their understanding is presented and compared with alternatives existing in the literature. Comparative comments are made on the three available approaches: the ordered polaronic, the disordered polaronic and the disordered non-polaronic. It is argued that none is in a satisfactory state at the moment. Key problems that require theoretical attention are identified.