Charge transport in molecularly doped polymers

Abstract

This paper re-examines literature data on the charge-carrier mobility in tri-phenyl methane/polycarbonate, triphenyl amine/lexan and PVK: TNF composite systems. In all cases the dependence of μ on both temperature T and electric field E, as well as its absolute magnitude, can be interpreted consistently in terms of hopping across a Gaussian density-of-states distribution of width σ. The exponential dependence of μ on T −2 and E predicted by computer simulation and analytic theory for transport in the long-time limit are recovered. The essential parameters that control μ are μ0= lim μ(T) which is the mobility of the hypothetical crystalline counterpart structure, and σ. The latter quantity increases with increasing polarity of the constituent molecules and is responsible for the variation of μ upon chemical substitution reported for the triphenyl methane polycarbonate system.