Electric field dependent activation energy of electron transport in fullerene diodes and field effect transistors: Gill's law

The electric field and temperature dependence of the electron mobility is studied comparatively in the bulk of fullerene (C-60) diodes and at the interface with dielectric of organic field effect transistors (OFETs). Electron mobility values follow a Poole-Frenkel-type electric field dependence in both types of devices. The activation energy for electron transport is electric field dependent and follows the square root law of field in both devices as predicted by Gill's law. The same Gill's energy E-Gill=34 meV is measured in diodes and OFETs, which corresponds well to Meyer-Neldel energy (E-MN=35 meV). It is shown that both the electric field and charge carrier concentration must be accounted for the description of disordered charge transport. (C) 2011 American Institute of Physics. [doi:10.1063/1.3557503]