HOLE TRAPPING IN TRI-P-TOLYLAMINE-DOPED POLY(STYRENE)

Hole mobilities have been measured in tri-p-tolylamine-doped poly(styr ene) containing different concentrations of di-p-tolyl-p-anisylamine ( DTA), di-p-anisyl-p-tolylamine (DAT), and tri-p-anisylamine (TAA). DTA , DAT and TAA are traps with depths of 0.08, 0.15 and 0.22 eV. The mob ilities decrease with increasing trap concentration and trap depth whi le the field and temperature dependencies remain unchanged. The prefac tor mobilities are independent of trap concentrations and depths. The results are discussed within the framework of the recent simulations o f Wolf et al. The results are in good agreement and confirm the argume nt that for shallow trapping the basic phenomenology of transport, as revealed by the field and temperature dependencies of the mobility, re main unchanged. Quantitatively, the effects of traps can be accounted for by the replacement of the energy width of the hopping site manifol d by an effective width whose square increases linearly with trap dept h and the logarithm of the trap concentration. (C) 1998 Elsevier Scien ce B.V. All rights reserved.