On the concentration and field dependences of the hopping mobility in disordered organic solids

Theoretical approaches to hopping transport of charge carriers in random organic solids are considered. Concepts well approved in the field of inorganic disordered materials are claimed to be applicable to description of charge transport in random organic solids. This is illustrated by calculations of the dependence of the carrier mobility on the concentration of localized states based on the concept of transport energy. Also the widely discussed phenomenon of the mobility ‘increasing with decreasing electric field at low fields’ in organic materials is considered. Our calculations show that this phenomenon is likely to be an artefact caused by misinterpretation of experimental data. The concept based on the averaging of hopping rates is discussed and qualified as inappropriate.