Modeling of the temperature dependence of the field-effect mobility in thin film devices of conjugated oligomers

A simple model is proposed for charge carrier transport across grain bounda ries with an acceptor-like trap level. Potential wells between the grains a re formed due to negatively charged grain boundaries. Based on this model, a variety of temperature dependencies of the charge carrier mobility can be described. Using realistic parameters, this model reproduces very well the measured temperature dependencies of the field-effect mobility in polycrys talline pentacene and oligothiophene thin film devices. Therefore, it seems to be difficult to investigate the intrinsic material properties of organi c semiconductors using only polycrystalline field-effect devices, since the y may be masked by the effects of traps and grain boundaries. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)00202-8].