Hole mobility in various transition-metal-oxides doped organic semiconductor films

Hole mobility in various p−doped organic semiconductors possessing different energetic disorder parameters in low-to-moderate doping range is reported. The hole mobility is reduced by orders of magnitude and converged to 10−7–10−6 cm2/Vs at a doping concentration of 5 mol. % for all the materials, even though the pristine organic films possess orders of magnitude of different mobilities from 10−5 to 10−3 cm2/Vs. These results indicate that the ionized dopants behave as traps for generated carriers to reduce the mobility. Further increase in the doping concentration either increases or decreases the mobility depending on the energetic disorder parameters of the organic films. These phenomena are interpreted based on the Coulomb trap depth of the ionized dopants and energetic disorder of the host layers.