Hole transport in vapor deposited bis(ditolylaminostyryl)benzene

Hole mobilities have been measured in vapor deposited bis(ditolylaminostyryl)benzene (TASB). TASB is a weakly polar molecule that contains two aniline donor functionalities. The results are described by a formalism based on disorder, due to Bassler and coworkers. The formalism is based on the assumption that charge transport occurs by hopping through a manifold of localized states that are distributed in energy. The key parameter of the formalism is the energy width of the hopping site manifold. The width is described by a model based on dipolar disorder. According to the model, the total width is comprised of a dipolar component and a van der Waals component. For TASB, the dipolar component is 0.012 eV and the van der Waals component 0.091 eV. The van der Waals component is considerably larger than values reported for other triarylamine donor glasses. This is attributed to differences in stereochemistry of the aniline donor functionalities.