ZERO ELECTRIC-FIELD ACTIVATION-ENERGY IN MOLECULARLY DOPED POLYMER SYSTEMS

The Poole-Frenkel approach has been applied to two charged centers sep arated by a distance R. The reduction of the potential barrier due to a finite R and the presence of an externally applied electric field E is calculated. In the limiting case E --> 0 the activation energy is f ound to be Delta epsilon(E = 0, R) = Delta epsilon(0) - e(2)/epsilon(0 ) epsilon R, where Delta epsilon(0) denotes the potential barrier heig ht for an isolated center. Experimental results on drift mobility meas urements in N-isopropylcarbazole dispersed into amorphous polycarbonat e are in agreement with this relation.