Hole trapping in molecularly doped polymers: The Hoesterey-Letson formalism

Hole trapping has been investigated in di-p-anisyl-p -tolylamine (DAT), tri-p-tolylamine (TTA), di-p-toiylphenylamine (DTP), and diphenyl-p-tolylamine (DPT) doped poly(styrene) containing different concentrations of tri-p-anislyamine (TAA). From oxidation potential measurements, TAA is a trap for DAT. TTA, DTP, and DPT with depths 0.07, 0.22. 0.27, and 0.34 eV. respectively. In such a way, it is possible to investigate the effect of trap depth using the same trap molecule. The mobilities decrease with increasing trap depth and concentration. For a TAA molar concentration of 10(-2), the room temperature mobilities are suppressed by as much as four orders of magnitude. The results are compared to predictions of the Hoesterey-Letson formalism and discussed within the framework of the recent simulations of Wolf et al. [Chem. Phys. 222 (1997) 259] and Borsenberger et al. (submitted to Chem. Phys.).