Understanding the dependence of transport parameters on carrier concentration within a Gaussian density of states in molecular organic semiconductors.

We study charge transport in molecular organic semiconductors using two terminal and three terminal field effect transistor devices. Using phthalocyanines as examples, we achieve unification of carrier mobility between the different configurations in a Gaussian density of states. We find that the current density-voltage characteristics for two terminal devices can be understood by introducing a concentration dependence of the carrier mobility, as described by Oelerich et al (2012 Phys. Rev. Lett. 108 226403, 2010 Appl. Phys. Lett. 97 143302). Studying the evolution of the activation energy with the carrier density, we find results consistent with a percolation picture and a density dependent transport energy.