Emission limited injection by thermally assisted tunneling into a trap-free transport polymer

Abstract
We have measured the steady‐state current supported by a variety of contacts on a polytetraphenylbenzidine hole transport polymer. When glassy carbon is used as a hole injecting contact to the polymer, the current is found to exhibit prototypical emission limited behavior. Unique features of the electric field and temperature dependence of the emission limited current cannot be explained by injection theories appropriate to conventional band type semiconductors. A model of thermally assisted tunneling from carriers at the Fermi level of the contact to localized states in the polymer has been formulated. This model is able to critically account for key features in the experimental data.