Enhanced hole mobility in ambipolar rubrene thin film transistors on polystyrene

We report amorphous rubrene thin film transistors with a polystyrene intermediate layer on the SiO(2) gate dielectric that have hole mobilities up to 0.01 cm(2)/V s. This improvement by two orders of magnitude over devices formed on SiO(2) alone occurs without the crystallization of rubrene. The enhanced charge transport is a result of the more planar growth and subsequent better geometrical connection of the first molecular layers of rubrene. Ambipolar conduction in the rubrene suggests that polystyrene minimizes the concentration of interfacial electron trap states. (C) 2008 American Institute of Physics.