Doping-concentration-dependent hole mobility in a ReO3 doped organic semiconductor of 4,4′,4″-tris(N-(2-naphthyl)-N-phenyl-amino)-triphenylamine

The effect of electrical doping on the hole carrier mobility in a p-doped organic semiconductor is reported. We focus on the ohmic current region where the density of carriers generated by doping is much higher than that of injected carriers. We can therefore analyze the effect of doping on the charge-carrier mobility, excluding the effect of the injected charge-carrier density and the electric field. The hole mobility decreases as the doping concentration increases, indicating that the negatively charged dopants form Coulomb traps that disturb hole transport in the p-doped organic system. The activation energy of the mobility increases as the doping concentration increases, consistent with a broadening of the Gaussian density-of-states distribution by the negatively charged dopants.